O presente estudo foi conduzido com o objetivo de avaliar os efeitos de diferentes níveis de inclusão de grão de soja cru e integral na alimentação de vacas leiteiras em início de lactação, e seus efeitos sobre o consumo e digestibilidade da matéria seca e nutrientes, fermentação ruminal, síntese de proteína microbiana, produção e composição do leite, perfil de ácidos graxos da gordura do leite, concentrações de parâmetros sanguíneos, balanço de energia e nitrogênio, excreção e composição do grão de soja presente nas fezes e desempenho produtivo. Foram utilizadas 12 vacas da raça Holandesa, agrupadas em três quadrados latinos balanceados e contemporâneos 4x4, alimentadas com as seguintes rações: 1) Controle (C), composto por ração sem a inclusão de grão de soja; 2) Grão de soja integral 8% (G8), 3) Grão de soja integral 16% (G16), e 4) Grão de soja integral 24% (G24), com a utilização respectivamente, de 8,0, 16,0 e 24% de grão de soja cru e integral na ração, na matéria seca. A produção de leite e o consumo de matéria seca foram mensurados diariamente durante todo o período experimental. As amostras utilizadas para análise da composição do leite foram coletadas no 16o dia de cada período experimental, sendo provenientes das duas ordenhas diárias. As amostras de sangue foram coletadas em tubos vacuolizados por punção da veia e/ou artéria coccígea. As amostras de líquido ruminal foram coletadas com a utilização de sonda esofágica três horas após a alimentação matinal. A digestibilidade foi determinada por meio de indicador interno FDAi. Houve redução no consumo de matéria seca e de carboidratos não fibrosos nas vacas suplementadas com a ração G24 em relação às demais rações, que não diferiram entre si. Foi observado efeito linear crescente no consumo de extrato etéreo, onde os animais submetidos à dieta G24 apresentaram maiores valores. Houve diferença na digestibilidade aparente total dos nutrientes entre as rações experimentais, sendo que a dieta G24 apresentou diminuição da digestibilidade da proteína bruta, em relação às dietas C, G8 e G16. Não houve efeito das rações utilizadas nos valores de pH ruminal. A concentração de nitrogênio amoniacal ruminal foi maior (P<0,05) para as vacas que receberam a dieta controle em relação às dietas com grão de soja. Entre as rações utilizadas, a ração G24 resultou em redução da produção de leite e de proteína em Kg/dia. Os teores no leite de proteína, gordura e lactose não foram alterados pelas fontes de gordura adicionadas nas rações, da mesma maneira o perfil de ácidos graxos da gordura do leite não sofreu alterações significativas. As concentrações de colesterol total e HDL foram maiores para as vacas alimentadas com rações contendo grão de soja em relação à ração controle. As concentrações de uréia e nitrogênio uréico, no soro e no leite, foram semelhantes entre as rações utilizadas. As rações utilizadas não influenciaram a síntese de proteína microbiana. O balanço de energia não foi influenciado pelas dietas experimentais. Houve efeito das rações experimentais sobre o balanço de nitrogênio, onde a ração G16 apresentou o melhor resultado, e a excreção fecal de nitrogênio foi maior para a dieta G24. Com relação a composição das fezes a dieta G24 apresentou porcentagens maiores de proteína e extrato etéreo, e a excreção de grão de soja nas fezes mostrou efeito linear crescente, assim a medida que aumentava os níveis de inclusão aumentava a excreção do grão nas fezes. A utilização de diferentes níveis de grão de soja nas rações altera o consumo, desempenho produtivo e metabolismo de vacas em lactação, sendo o resultado dependente da fase do nível de grão de soja cru e integral adicionado as rações. / This study was conducted to evaluate the effects of different levels of inclusion of crude soybean and full in feeding of dairy cows in early lactation and their effects on intake and dry matter digestibility and nutrients, rumen fermentation, microbial protein synthesis, yield and milk composition, fatty acids profile of milk fat, concentrations of blood parameters, energy and nitrogen balance, excretion and composition of soybean present in faeces and productive performance. A total of 12 holstein cows, grouped in three latin squares balanced and contemporary 4x4, fed the following diets: 1) control (C), composed of feed without the inclusion of soybean, 2) grain soybean 8% (G8), 3) grain soybean 16% (G16), and 4) grain of soybean 24% (G24), using respectively 8.0, 16.0 and 24% of whole raw soybean in the diet, in dry matter. Milk yield and dry matter intake were measured daily throughout the experimental period. The samples used for analysis of milk composition were collected on the 16th day of each period, and from the two milkings. Blood samples were collected in tubes by venipuncture vacuolated and/or coccygeal artery. Samples of rumen fluid were collected with use of gavage three hours after the morning feeding. The digestibility was determined by means of an internal indicator iADF. A reduction in dry matter intake and non-fibrous carbohydrates in cows fed the G24 ration compared to other diets, which did not differ. Increased linear effect was observed in the ether extract intake in the consumption of fat, where the animals submitted to G24 diet presented higher values. Total apparent digestibility of the nutrients between experimental diets, and the G24 diet showed decreased crude protein digestibility compared to diets C, G8 and G16. No effect of diets used in the values of rumen pH. The rumen ammonia concentration was higher (P<0.05) for cows that received the control diet compared to diets with soybean. Among the rations, ration G24 resulted in decreased milk yield and protein in Kg/day. The levels in milk protein, fat and lactose were not affected by fat sources added to the diet, just as the fatty acid profile of milk fat did not significantly change. The concentrations of total cholesterol and HDL were higher for cows fed diets containing soybean in relation to the control diet. The urea and urea nitrogen concentrations in serum and milk were similar between the rations. The rations did not affect microbial protein synthesis. The energy balance was not influenced by experimental diets. There was an effect of experimental diets on nitrogen balance, where the G16 ration presented better result, and fecal nitrogen excretion was higher for G24 diet. Regarding the composition of faeces G24 diet showed larger percentages of protein and fat, and excretion of soybean in the feces showed a increasing linear effect, as well as the increased levels of inclusion of grain increased excretion in the faeces. The use of different levels of soybean in the diet alter the intake, productive performance and metabolism in dairy cows, and the results being dependent on the stage of the level of raw and integral soybean added to diets.

O objetivo deste estudo foi avaliar o efeito da degradabilidade de fontes nitrogenadas em rações de vacas leiteiras, utilizando volumoso à base de cana-de-açúcar, sobre o consumo e digestibilidade dos nutrientes, fermentação ruminal, produção e composição do leite, composição da fração proteica do leite, e parâmetros sanguíneos. Foram utilizadas 12 vacas da raça Holandesa, agrupadas em três quadrados latinos balanceados 4x4, com período experimental de 21 dias, sendo nos 7 últimos dias as coletas. Os animais foram alimentados com rações isoproteicas (15,7% de PB): a) Controle - 66,25% PDR, 33,75 % PNDR, farelo de soja e ureia; b) Alta degradabilidade 71,33% PDR, 29,29% PNDR, farelo de soja e alta concentração de ureia (1,71% da MS); c) Média degradabilidade - 69,42% PDR, 31,21% PNDR, soja crua em grão como fonte proteica e d) Baixa degradabilidade 62,42% PDR, 37,57% PNDR, farelo de glúten de milho como fonte proteica. As amostras utilizadas para análise de composição do leite foram coletadas nos quatro últimos dias consecutivos de cada período experimental. As amostras de líquido ruminal foram coletadas por sonda esofágica três horas após a alimentação matinal. A digestibilidade foi determinada por meio de indicador interno FDAi. Houve aumento de consumo de extrato etéreo nas vacas alimentadas com a ração contendo grão de soja, fonte nitrogenada com média degradabilidade, em relação aos demais tratamentos. Houve redução na digestibilidade aparente total das proteínas nas rações de média degradabilidade. Não houve efeito das rações utilizadas nos valores de pH ruminal, três horas após a alimentação. Neste mesmo tempo, a concentração de nitrogênio amoniacal ruminal foi menor para as vacas que receberam grão de soja nas rações. Entre as rações nitrogenadas controle e as que possuem diferentes degradabilidades, a ração com grão de soja resultou em redução da produção de leite corrigida para 3,5% de gordura e produção de gordura. Houve aumento no teor e produção de proteína para a ração controle, dentre as demais. Os teores de proteína bruta no leite, nitrogênio não caseinoso e proteína verdadeira foram maiores para vacas alimentadas com ração controle. As concentrações de colesterol total e colesterol-HDL foram maiores para as vacas alimentadas com rações contendo grão de soja. As concentrações de ureia e nitrogênio ureico no soro foram menores nas dietas com grão de soja. Estas concentrações quando no leite foram semelhantes entre as rações utilizadas. Os parâmetros de síntese proteica não foram alterados com as rações experimentais. A utilização de fontes nitrogenadas com diferentes degradabilidades nas rações de vacas leiteiras, com volumoso cana-de-açúcar, não altera o consumo e o desempenho produtivo, mas altera o teor de proteína bruta e verdadeira do leite. O uso do grão de soja como fonte proteica reduz a digestibilidade aparente total da proteína. / This study was carried out to evaluate the effect of degradability of dietary protein sources for dairy cows, using sugar cane based diets on intake and nutrients digestibility, ruminal fermentation, milk yield and composition, milk protein fraction composition, and blood parameters. Twelve Holstein cows were allocated in three balanced latin square 4x4, with experimental period of 21 days and 7 last days for data collection. Animals were fed the following rations isoproteic (15,7% CP): a) control - 66,25% RPD, 33,75 % RUP, soybean meal and urea; b) high degradability - 71,33% RPD, 29,29% RUP, soybean meal and high concentration of urea ( 1,71% of DM); c) medium degradability - 69,42% RPD, 31,21% RUP, raw soybeans and, d) low degradability 62,42% RPD, 37,57% RUP, corn gluten meal as the protein source. Milk samples for composition analysis were collected during the last four consecutives days in each period. Ruminal fluid samples were collected using an esophageal probe three hours after the morning fedding. Digestibility was determined using ADFi as an internal indicator. There was an increase in ether extract intake in cows fed raw soybean ration, compared with other treatments. It was observed a reduction in apparent digestibility of CP in the diets of medium degradability. It was not observed effects of treatments in ruminal pH, however, concentration of ruminal ammonia was lower for cows fed whole soybeans. Cows fed raw soybean produced less 3,5% fat milk and lower fat yield. Milk crude protein and protein yield was higher for cows fed control diet. Milk crude protein, non-casein nitrogen and true protein were higher for cows fed control diet. Concentrations of total cholesterol and cholesterol-HDL were higher for cows that received soybean, compared with the others treatments. Concentrations of urea and serum urea nitrogen were lower in cows fed soybean ration. The concentrations of urea and milk urea nitrogen were similar between the treatments. Feeding nitrogen sources with different degradability rates in sugar cane based diets for dairy cows not change intake and production performance but change milk crude protein and true protein. Feeding soybean as protein source decreases protein total apparent digestibility.

O objetivo deste estudo foi avaliar diferentes concentrações de monensina sódica na ração de vacas em lactação e seus efeitos sobre o consumo e digestibilidade aparente total da matéria seca e dos nutrientes, produção e composição do leite, fermentação ruminal, síntese de proteína microbiana, parâmetros sanguíneos e resíduos de monensina no leite. Foram utilizadas 12 vacas da raça Holandesa, distribuídas em três quadrados latinos 4x4 balanceados, alimentadas com as seguintes rações: 1) Controle (C), composto por ração basal sem adição de monensina, 2) Monensina 12 (M12), adição de 12 mg/kg MS de monensina na ração, adicionada ao concentrado, 3) Monensina 24 (M24), adição de 24 mg/kg MS de monensina na ração, adicionada ao concentrado e 4) Monensina 48 (M48), adição de 48 mg/kg MS de monensina, adicionada ao concentrado. A produção de leite e o consumo de matéria seca foram mensurados diariamente durante todo o período experimental. As amostras utilizadas para análise da composição do leite foram coletadas no 16o dia de cada período experimental, sendo provenientes das duas ordenhas diárias. As amostras de sangue foram coletadas em tubos vacuolizados por punção da veia e/ou artéria coccígea. As amostras de líquido ruminal foram coletadas com a utilização de sonda esofágica três horas após a alimentação matinal. A digestibilidade foi determinada por meio de indicador interno FDAi. Houve efeito linear decrescente do consumo de matéria seca, matéria orgânica, proteína bruta, extrato etéreo, carboidratos totais, fibra detergente neutro, carboidratos não fibrosos e nutrientes digestíveis totais. Não houve diferença na digestibilidade aparente total da matéria seca e dos nutrientes em função das rações experimentais, excetuando-se a digestibilidade aparente total da proteína bruta e fibra detergente neutro, que foram observados efeitos linear crescente e decrescente, respectivamente. Não houve efeito das rações experimentais sobre os valores de pH ruminal. A suplementação com monensina sódica nas dietas resultou em alteração da proporção molar de propionato no líquido ruminal, além de diminuir a relação acetato:propionato. As rações contendo monensina sódica apresentaram maior proporção molar de propionato e menor de acetato em relação à ração controle, e, de forma semelhante, apresentaram menor relação acetato:propionato. Não houve efeito das dietas experimentais nas excreções diárias totais de urina, de alantoína e de acido úrico na urina, e de derivados de purinas totais. Não houve diferença na porcentagem de alantoína nos derivados de purina, das purinas absorvidas e do nitrogênio microbiano para as rações experimentais. Foi observado aumento de produção de leite para as vacas alimentadas com as concentrações intermediárias de monensina sódica nas rações. Não houve efeito da adição de monensina sódica nas rações sobre os parâmetros sangüíneos glicose, colesterol total, proteína total, albumina, aspartato aminotransferase e &gamma;-glutamiltransferase. Foi observado efeito linear crescente com a adição de monensina sódica nas rações sobre a uréia e nitrogênio uréico do soro. Os resíduos de monensina sódica detectados no leite estão dentro do limite máximo estabelecido pela FAO/WHO. A utilização de monensina sódica nas rações de vacas leiteiras no terço médio de lactação influencia o desempenho produtivo dependendo da dose utilizada, e não resulta em resíduos no leite independentemente da dose utilizada. / This aim this study was evaluate the use of different concentrations of sodic monensin the feed of dairy cows and its effects on consumption and total apparent digestibility of dry matter and nutrients, milk yield and milk composition, ruminal fermentation, synthesis microbial protein, blood parameters and sodic monensis residues in milk. Twelve Holstein cows were allocated in three balanced Latin squares 4x4, and fed with the following rations: 1) control (C), basal diet without sodic monensin addition, 2) monensin 24 (M24), addition of 24 mg/kg DM of monensin in the ration, added to concentrate, and 3) monensin 48 (M48), addition of 48 mg/kg DM of monensin in the ration, added to concentrate. Milk yield and dry matter intake were measured daily throughout the experimental period. The samples used for analysis of milk composition were collected on the 16th day of each period, and from the two milkings. Blood samples were collected in vacuolated tubes by puncture or coccygeal vein or artery. Samples of rumen fluid were collected with use of esophageal probe three hours after the morning feeding. The digestibility was determined by means of an internal indicator iADF. There was linear effect dry matter intake, organic matter, crude protein, ether extract, total carbohydrates, neutral detergent fiber, non-fiber carbohydrates and total digestible nutrients. There was no difference on apparent total tract digestibility of dry matter, organic matter, ether extract, total carbohydrates, non-fiber carbohydrates and total digestible nutrient values observed for the experimental diets. There was no difference in total apparent digestibility of dry matter and nutrients depending on the experimental diets, except for the total apparent digestibility of crude protein and neutral detergent fiber, wich effects were observed linear ascending and descending, respectively. There was no effect for ruminal pH values. Supplementation with sodic monensin in the diets resulted inchanging the molar proportion of propionate in ruminal fluid while decreasing the acetate:propionate. The rations containing monensin had higher molar ratio of acetate propionate and smaller relation to the control diet and similary had a lower acetate:propionate ratio. There was no effect in total daily urine excretion of allantoin and uric acidin urine and total purine derivates. There was no difference in the percentage of allantoin in the purine derivates, absorbed purines and microbial nitrogen to the experimental diets. We observed increase in milk yield for cows fed the intermediate concentration of monensin in the feed. There was no effect of monensin in feed on the blood parameters glucose, total cholesterol, total protein, albumin, aspartate aminotransferase and &gamma;-glutamyltransferase. Increased linearly, with the addition of monensin in the feed on the urea and serum urea nitrogen. The detected residues of sodic monensin in milk was smaller that the maximum limit established for FAO/WHO. The use of monensin in diets cows in the middle third of lactation influences growth performance depending on the dose used, and does not result in residues in milk regardless of dose.

Made available in DSpace on 2014-08-20T14:37:50Z (GMT). No. of bitstreams: 1 tese_elizabeth_schwegler.pdf: 1198143 bytes, checksum: 306f08a6253b951c8751a8eba9c7194c (MD5) Previous issue date: 2012-08-15 / The peripartum in dairy cows (three weeks before and three weeks after calving) is characterized by large changes in physiological demands in the animal where management practices, particularly nutrition, strongly influences the incidence of peripartum disorders and subsequent milk production. Most of the studies in that period in dairy cows are focused on confined systems where milk production is high. Therefore, the aim of this study was to assess metabolic markers associated with the occurrence of clinical and subclinical mastitis and insulin resistance in dairy cows in semi extensive system. Our study was divided into two major experiments with the following hypothesis: 1) medium milk production primiparous cows in semi extensive system have predictive metabolic markers of clinical and subclinical mastitis in the prepartum, 2) medium milk production pluriparous dairy cows with low rate of glucose metabolism during the prepartum, which is an indicative of insulin resistance, have higher minerals excretion in the postpartum period. In experiment 1, blood concentrations of NEFA in the prepartum period were higher, in contrast, phosphorus and glucose were lower (P <0.05) in animals with clinical mastitis postpartum. In experiment 2, pluriparous dairy cows with low rate of glucose metabolism in the prepartum had higher urinary calcium excretion in both prepartum and postpartum periods, and also the highest NEFA concentration in the prepartum period (P <0.05). The blood concentrations of calcium in dairy cows with high rate of glucose metabolism in the postpartum was elevated from the prepartum period and remained in the postpartum (P <0.05). Dairy cows kept in semi extensive system with moderate production level had predictive markers of mastitis in the prepartum, as previously demonstrated by other authors in more intensified systems of higher requirements for the animal. The highlighted marker was NEFA, however, in the second study it was shown in higher concentrations in the pluriparous dairy cows with low rate of glucose metabolism at prepartum, emphasizing the importance of this marker also in the insulin resistance. / O periparto nas vacas leiteiras (três semanas anteriores e as três posteriores ao parto) é caracterizado por grandes mudanças nas demandas fisiológicas do animal, sendo que, as práticas de manejo, principalmente nutricionais, influenciam intensamente a incidência de desordens no periparto e a subsequente produção de leite. A maioria dos estudos neste período na vaca leiteira é em sistemas confinados de alta produção leiteira, por essa razão o objetivo desta tese foi identificar marcadores metabólicos preditivos com a ocorrência de mastite clínica e subclínica e com a excreção de minerais em vacas leiteiras em sistema semi-extensivo. Nosso estudo foi estratificado em dois trabalhos com as seguintes hipóteses: 1) vacas leiteiras primíparas de média produção em sistema semi-extensivo possuem marcadores metabólicos preditivos de mastite clínica e subclínica no pré-parto; 2) vacas leiteiras pluríparas de média produção com menor taxa de metabolização de glicose, que é um indicativo de resistência da insulina, no pré-parto possuem maior excreção de minerais no pós-parto. No experimento 1 as concentrações sanguíneas de NEFA no pré-parto foram maiores e de fósforo e glicose menores (P<0,05), em animais com mastite clínica no pós-parto. No experimento 2 as vacas leiteiras pluríparas com menor taxa de metabolização de glicose no pré-parto apresentaram maior excreção urinária do cálcio no pré e pós-parto, e ainda, o NEFA mais alto no pré-parto (P<0,05). As concentrações sanguíneas de cálcio em vacas leiteiras com maior taxa de metabolização de glicose no pós-parto foi elevada desde o pré parto, mantendo-se no pós (P<0,05). Nas condições estudadas, em vacas leiteiras mantidas em sistema semi-extensivo de mediana produção foi observado que há marcadores preditivos de mastite já no pré-parto, como previamente comprovado por outros autores em sistemas mais intensificados de maiores exigências para o animal. O marcador em destaque foi o NEFA, sendo que o mesmo no segundo estudo se apresentou de forma mais elevada nas vacas leiteiras pluríparas com menor taxa de metabolização de glicose no pré-parto, enfatizando a importância deste marcador também na resistência à insulina.

Made available in DSpace on 2014-08-20T13:32:50Z (GMT). No. of bitstreams: 1 tese_vinicius_coitinho_tabeleao.pdf: 864855 bytes, checksum: 84b7f4f2dc9f4bc7025094cdcd06be5f (MD5) Previous issue date: 2014-02-28 / Dairy cows are expected to perform maximum of their productive capacity, especially during the transition period (three weeks before and up to three weeks after calving). This period is characterized by intense changes in metabolism which cause a negative energy balance. This fact generates a period of typical weight loss, which has been correlated with insulin resistance, once the available glucose is destined for lactose synthesis, which in turn is responsible, in part, for milk production levels. Moreover, during lactation there are several managements that impairs animals health. If not executed properly, can cause trauma and predisposition for infections, especially of the mammary gland, because this gland is heavily manipulated and has contact with potentially infectious agents. From a entrance doorway, these agents can infect the gland and cause mastitis, which may be clinical (with clinical signs) or subclinical (without clinical signs). In situations of metabolic disorders or in cases of mastitis, the milk production may be affected. Therefore, there is a constant search for technologies that can minimize these disorders and assist the production systems. Our objective was to investigate the effects of combining butaphosphan and cyanocobalamin on the glycemic metabolism in healthy dairy cows in the postpartum period and their effects on the mammary gland recovery in dairy cows after clinical mastitis treatment. Thus, our study was stratified into two assumptions: 1) the use of the association of butaphosphan and cyanocobalamin enhances peripheral insulin resistance in dairy cows, providing greater amounts of glucose for milk production, 2) the supplementation with butaphosphan and cyanocobalamin facilitates mammary gland recovery in dairy cows affected by mastitis. In experiment 1, animals receiving repeated doses of butaphosphan and cyanocobalamin had greater weight loss and increased (P<0.05) of the activities of the enzymes aspartate aminotransferase and creatine kinase. Moreover, at end of treatment had an increase (P<0.05) in glucose concentration in treated animals when compared to the beginning of study. In experiment 2, the comparative analyzes between mild and moderate mastitis did not differ (P>0.05) in any parameters. The animals treated with butaphosphan and cyanocobalamin had lower (P<0.05) somatic cell count after the third application. However, the concentrations of glucose, albumin, TPP, NEFA and the chemical and physical components of milk did not differ (P>0.05) among groups. In concusion, the combination of butaphosphan and cyanocobalamin shows promising results as a source of nutrient that allows intensify physiological reactions mainly dependent phosphorylation. / As vacas leiteiras são desafiadas a desempenhar o máximo da sua capacidade produtiva, principalmente, durante o período de transição (três semanas anteriores e três semanas posteriores ao parto). Este período é caracterizado por intensas mudanças no metabolismo que causam um balanço energético negativo. Este fato gera uma perda de peso característica do período, que tem sido correlacionada com a resistência periférica à insulina, haja vista, que a glicose disponível esta sendo destinada para síntese de lactose, que por sua vez é responsável, parcialmente, pelo volume de leite produzido. Além disso, durante a lactação há vários manejos que podem oferecer risco à saúde dos animais, caso não sejam executados adequadamente, causando traumas e predispondo o animal a infecções, especialmente, da glândula mamária, já que ela é intensamente manipulada e tem contato com vários agentes potencialmente infecciosos. A partir de uma porta de entrada estes agentes podem infectar a glândula causando a mastite, que pode se apresentar na forma clínica (com presença de sinais clínicos), ou subclínica (sem sinais clínicos). Nas situações de desequilíbrio metabólico, ou em casos de mastite, a produção de leite pode ser prejudicada. Diante disso, há uma busca constante por tecnologias que possam minimizar estes transtornos e auxiliar os sistema de produção. Nosso objetivo foi verificar o efeito da associação de butafosfan e cianocobalamina sobre o metabolismo glicêmico de vacas leiteiras saudáveis no período pós-parto, além dos seus efeitos sobre a recuperação da glândula mamária em vacas leiteiras após o tratamento de mastite clínica. Para tanto, nosso estudo foi estratificado em dois trabalhos com as seguintes hipóteses: 1) a utilização da associação de butafosfan e cianocobalamina pode intensificar a resistência à insulina periférica, disponibilizando maior quantidade de glicose para a produção de leite em vacas leiteiras; 2) a suplementação da associação de butafosfan e cianocobalamina pode auxiliar na recuperação da glândula mamária de vacas leiteiras, após o tratamento da mastite clínica. No experimento 1, os animais que receberam sucessivas doses de butafosfan e cianocobalamina tiveram maior perda de peso e aumento (P<0,05) das atividades das enzimas aspartato amino transferase e creatinoquinase. Além disso, ao final do tratamento houve aumento (P<0,05) dos níveis glicêmicos nos animais tratados, quando comparados ao inicio. No experimento 2, as análises comparativas entre as mastites, leve e moderada, não diferiram em nenhum dos parâmetros (P>0,05). Os animais tratados com butafosfan e cianocobalamina apresentaram menor (P<0,05) contagem de células somáticas após a terceira aplicação. Entretanto, os níveis de glicose, albumina, PPT, AGNES e os componentes químicos e físicos do leite não diferiram (P>0,05) entre os grupos. Nessas condições de estudo, podemos concluir que a associação de butafosfan e cianocobalamina apresenta resultados promissores como fonte de nutriente que permite intensificar as reações fisiológicas, principalmente, as dependentes de fosforilação.

Les performances de reproduction des vaches laitières se sont dégradées parallèlement à l’augmentation de leurs performances de production. L’intense sélection réalisée sur la production laitière est tenue responsable de cela. Chaque étape du processus de reproduction a été affectée : les anomalies de cyclicité ovarienne sont plus fréquentes dans la population actuelle, la durée et l’intensité des chaleurs ont diminué drastiquement, et les échecs de gestation sont plus fréquents. La littérature s’accorde sur le fait que la reproduction est affectée parce que la majeure partie des ressources est investie dans la production laitière. L’objectif de cette thèse de doctorat est d’étudier l’intérêt d’une stratégie de sélection alternative basée sur un fort potentiel génétique de taux butyreux et protéique sur la robustesse des vaches laitières.Les hypothèses testées étaient que par rapport aux vaches à fort potentiel de production laitière, celles à fort potentiel de taux butyreux et protéique (i) exportent moins d’énergie dans le lait et donc préservent leur réserves corporelles, (ii) ont de meilleures aptitudes à se reproduire. Nos résultats montrent que les vaches à fort potentiel de taux butyreux et protéique ont un retour de cyclicité plus précoce, une expression des chaleurs similaire mais plus d’échecs de gestation que celles à fort potentiel de production laitière. Ces résultats intrigants suggèrent que les étapes de la reproduction sont partiellement découplées sur le plan génétique. Sélectionner les vaches laitières sur les taux butyreux et protéique dans le but d’amé / Reproductive performance of dairy cows has been declining while their milk production was improving. The strong genetic selection that was applied on milk production is considered to be responsible for this. Each step of the reproductive process has been impacted: abnormal ovarian activity is more common in the current population, the duration and intensity of oestrus has dramatically decreased and the occurrence of pregnancy failures has increased. The consensus in the literature is that reproduction is impaired because dairy cows are investing most of their resources in milk production. The aim of this Ph.D. thesis is to explore the effect of alternative selection strategies based on milk fat and protein content on robustness of dairy cows. Our hypotheses were that at similar genetic merit for milk solids yield, compared to cows with high genetic merit for milk yield,dairy cows with high genetic merit for fat and protein contents (i) are exporting less energy in milk and are consequently safeguarding their body reserve; (ii) have better reproductive performance (earlier resumption of ovarian activity, more intense oestrus, better ability to ensure pregnancy). Our results suggest that cows selected for production through high fat and protein content instead of high milk yield would resume ovarian activity earlier, have similar oestrus intensity but more pregnancy failures. These intriguing results suggest that the steps of the reproductive process are genetically partly disentangled. Selecting dairy cows for fat and protein content is not a promising way to improve repro

The objective of the study was to evaluate cow reproductive performance in the sweetveld and sourveld communal grazing areas of the Eastern Cape Province, South Africa. In the first experiment, farmer perceptions were obtained using participatory rural appraisals. Farmers ranked lack of fences, tick-borne diseases, poor animal condition during winter and poor breeding practices, respectively as major constraints limiting cattle production in the Eastern Cape. Cattle, sheep and goats, in that order, were ranked as the most important livestock species and were mainly kept for meat, cash and ceremonies, respectively. The non-descript cattle breed was the most common breed found in the smallholder areas. Most farmers preferred Nguni breed because of its adaptive attributes. In the second experiment, structured questionnaires were administered, between June and August 2006, to a total of 551 farmers from 10 communities of the Eastern Cape. There was a significant association (P<0.05) between the use of pregnancy diagnoses and community. About 87 and 77 % of the interviewed farmers did not respond on the extent of pregnancy and calving rates in their herds. A higher proportion of farmers from Hekele (51%) and from Upper Mnxe (45.3%) communities reported low number of bulls as a major constraint to cow reproductive performance. Body condition and ovarian activity were measured in the sweet and sour veld types. Body condition score of animals was measured from March iii 2007 until January 2008 and ovarian activity of cows was performed by a veterinarian through rectal palpation in June, August and October 2007 and January 2008. From March to July, there was a marked decline in body condition on both veld types. In the sweetveld, body condition improved from September until January, whereas in the sourveld the improvement in body condition started in October. The cows in both veld types conceived throughout the year. Most cows in the sweetveld were cycling in January and August (P<0.05) whereas in the sourveld there was no distinct period when the animals were cycling. Overall, there were no differences in the proportion of cows that were cycling between the sour and sweet veldts (P>0.05). There were more cows cycling in sourveld in October than in the sweetveld. Reproductive performance of cows in communal areas could, therefore, be determined by levels and quality of nutrition. Keywords: Participatory rural appraisals; Structured questionnaires; Farmer participation; Farmer perceptions; Body condition scoring; Ovarian activity; Pregnancy diagnoses.

Corpus luteum (CL), a transient endocrine structure formed from the ruptured ovarian follicle after ovulation, secretes progesterone (P4) that is essential for establishment and maintenance of pregnancy in mammals. The biosynthesis and secretion of P4 from CL depends, in general, on trophic hormones of the anterior pituitary gland and on hormones or factors originating from ovary, uterus, embryo and placenta. The structure and function of CL tissue is regulated by intricate interplay between two types of factors, namely, the luteotrophic factors, which stimulate CL growth and function, i.e., P4 secretion, and the luteolytic factors, which inhibit CL function and lead to luteal regression. In monoovulatory species such as higher primates and bovines, a striking diversity in the regulation of CL function exists not only between species, but also within the species during different stages of the luteal phase. In higher primates, unlike other species, one of the important characteristics of CL regulation is that, during non-fertile cycle, circulating LH appears to be the sole trophic factor responsible for maintenance of its function, and during fertile cycle, chorionic gonadotropin (CG), an LH analogue, originating from placenta maintains CL function. In higher primates, the role/involvement of luteolytic factors during luteolysis remains elusive. On the other hand, in the bovine species, the role/involvement of luteolytic factor, prostaglandin (PG) F2α during luteolysis is well established. It should be pointed out that in both the species, the mechanism of luteolysis is still poorly understood and the work presented in this thesis attempts to address these lacunae. Further, in bovines, studies have been carried out to examine potential trophic factor(s) responsible for the maintenance of CL function. Chapter I provides an extensive review of literature on CL structure and function with emphasis on factors that influence its growth, development, function and demise in primates and bovines. In Chapter II, employing bonnet monkey (Macaca radiata) as the representative animal model for higher primates, various studies have been conducted to examine the role of molecular modulators involved in regulation of CL function, particularly during spontaneous luteolysis. Although, it is well established that LH is essential for the maintenance of CL function in higher primates, the mechanism(s) responsible for the decline in serum P4 levels at the end of non-fertile cycles, without a concomitant change in circulating LH milieu, remains to be addressed. Several experiments have been conducted to examine the component(s) of luteotrophic (LH/CG) signaling that is/are modulated during luteolysis in the bonnet monkey CL. To understand the relative lack of responsiveness of CL to the circulating LH during the late luteal phase, LH/CG receptor (R) dynamics (expression of LH/CGR and its various transcript variants) was examined throughout the luteal phase and during different functional states of the monkey CL. The results indicated presence of LH/CGR mRNA, its transcript variants and functional LH/CGR protein in the monkey CL on day 1 of menses. Moreover, the functionality of receptors was tested by confirming the biological response of the CL to bolus administration of exogenous LH preparations, which eventually suggested factor(s) downstream of LH/CGR activation to account for the decline in CL function observed during non-fertile cycle. Studies have been conducted to identify molecular modulators that would selectively exploit intraluteal processes to regulate trophic signaling pathways that are critical to the control of luteal function. Immunoblot and qPCR analyses were carried out to examine presence and activation of Src family of kinases (SFKs) and cAMP-phosphodiesterases (PDEs) during various functional states of CL. The results revealed an increased activation of Src (phosphorylated at Tyr 416) during spontaneous and PGF2α/CET-induced luteolysis that may participate in the regulation of cAMP levels in part by increasing the cAMP-PDE activity observed during spontaneous luteolysis. This observation raised the question on the possible mechanism by which CG, an analog of pituitary LH, rescues CL function during early pregnancy. Thus, subsequent experiments involving LH/hCG administration in CET-treated animals as well as simulated early pregnancy animal model were conducted and the results revealed that, a bolus of LH/hCG decreased Src activation and cAMP-PDE activity accompanying a momentous increase in cAMP levels in both these models that further led to a concomitant increase in P4 secretion. Although the mechanisms of action of LH/CG involve modulation of a number of signaling pathways in the CL, by far, the results from various experiments suggested that it leads to activation of Src kinase and cAMP-PDE, thus causing inhibition of various elements of the primary signaling cascade- AC/cAMP/PKA/CREB during spontaneous luteolysis. One of the consequences of activation of Src kinase and cAMP-PDE was the regulation of expression of genes associated with steroidogenesis and it was observed that expression of SR-B1, a membrane receptor associated with trafficking of HDL-CE into the luteal cells, was lower in the regressed CL. The results taken together suggest that the decrease in responsiveness of CL to LH milieu during non-fertile cycles is not associated with changes in LH/CGR dynamics, but, is instead coupled to the activation of Src kinase and cAMP-PDE, inhibition of molecules downstream of LH signaling, and a decrease in the SR-B1 expression that regulates cholesterol economy of the luteal cell, and in turn, P4 secretion. The control of primate CL function appears to be dominated by the luteotrophic factors (LH/CG) over the luteolytic factors, since the process of luteal regression was overcome by administration of LH/CG. Further, in the primate CL, the molecular modulators of LH/CG signaling (Src kinase and PDE) are maintained in the repressed state by the luteotrophic factor LH/CG for maximum steroidogenic function. In contrast, in non-primate species, without invoking a role for the luteotrophic factor, essentially the synthesis and secretion of luteolytic factor, PGF2α, from the uterus is kept in check during pregnancy by the trophoblast derived IFN- and thus allowing CL to continue to function that is essential for maintenance of pregnancy. In the bovine species, the mechanism of PGF2α-induced luteolysis that involves a change in expression of genes associated with various processes of cellular function is poorly understood. Experiments were conducted utilizing buffalo cows (Bubalus bubalis) as a model system, to determine temporal changes in the global gene expression profile of the CL in response to PGF2α treatment. For this purpose, CL tissues were collected on day 11 of estrous cycle without treatment (designated as 0 h) and at 3, 6 and 18 h post PGF2α treatment for various analyses. Global changes in gene expression pattern in the CL were investigated employing Affymetrix GeneChip bovine genome array and the results are presented in Chapter III. The hybridization intensity values obtained by microarray analysis were subjected to R/Bioconductor tool. Following the application of highly stringent statistical filters to eliminate false positives, a set of differentially expressed genes were identified. The differentially expressed genes were further classified based on a fold change cut-off filter of ≥2, and the analysis revealed 127 genes to be differentially expressed within 3 h of PGF2α administration, of these 64 and 63 genes were up-regulated and down-regulated, respectively. Analysis of microarray data at 6 h post PGF2α administration revealed 774 genes to be differentially expressed, of which 544 genes were up-regulated, while 230 genes were down-regulated. The microarray analysis performed on CL tissues collected at 18 h post PGF2α administration showed that out of the total 939 differentially expressed genes, 571 genes were up-regulated, while 368 genes were down-regulated. Analysis of the ontology report for the biological processes category showed that initially in response to PGF2α administration, genes regulating steroidogenesis, cell survival and transcription were differentially regulated in the CL, but at later time points, differential expression of genes involved in apoptosis, PGF2α metabolism, tissue remodeling and angiogenesis was observed. Further, involvement of molecules downstream of LH/IGF-1 activation was investigated and the results obtained indicated that PGF2α interfered with the LH/IGF-1 signaling since the expression of LH/CGR, GHR and pAkt were down-regulated following PGF2αadministration. Furthermore, the functional luteolysis observed post PGF2αadministration appeared to be due to an interruption in cholesterol trafficking to inner mitochondrial membrane, since StAR expression was inhibited. The results obtained also demonstrated that the expression of AGTR1, VEGFR2 and R3 were down-regulated following PGF 2α administration. Further, the data obtained also suggested modulation of expression of pro- and anti-angiogenic factors upon PGF2α-treatment indicative of an involvement of other autocrine or paracrine factor(s) in the regression of bovine CL. This was an interesting finding as it suggests a novel and potential functional relationship between angiogenesis and the luteolytic response of CL to PGF2α administration. In bovines, despite extensive research being carried out to examine factors involved in the regulation of development and function of the CL, the trophic factor(s) required for maintenance of CL function, especially, P4 biosynthesis and secretion are not well characterized. It was hypothesized that the function of the CL during its finite lifespan must be responsive to LH as well as to various growth factors. Thus, experiments were conducted to examine the effects of increased LH and GH/IGF-I on the maintenance of CL function during mid luteal phase and post PGF2α administration and the results of these studies are presented in Chapter IV. To elucidate the role of LH as a trophic factor in the regulation of CL function, effects of increased endogenous LH through GnRH administration and exogenous hCG injections were examined. The results indicated an absence of noticeable effect of various hCG/GnRH treatments on circulating P4 levels. On the other hand, administration of GH resulted in increased serum IGF-1 and P4 levels. It was further observed that the administration of a combination of hCG and GH increased serum P4 levels better than treatment with GH alone. Further experiments were carried out to examine the complex reciprocal relationship between LH/GH and PGF2α on expression of genes involved in the regulation of luteal structure and function. In buffalo cows, administration of exogenous hCG and/or GH following inhibition of CL function by PGF2α administration did not prevent the PGF2α-induced decline in serum P4 levels, but PGF2-mediated decrease in expression of LH/CGR and GHR genes was prevented upon GH administration. However, the decrease in StAR expression was not restored by hCG and GH treatments, thereby indicating that PGF2 action was not prevented by hCG and/or GH treatments. Taken together, the results of studies carried out in buffalo cows employing various experimental model systems suggest essential role for LH and GH/IGF-1, however, these factors were unable to reverse PGF2α-induced luteolysis. Further, our crucial findings of the effects of increased endogenous LH and IGF-1, in addition to their relationship with luteolytic agents such as PGF2α will open new avenues for studying the mechanisms involved in the regulation of structural and functional properties of the buffalo CL. It is well known that a large number of buffalo cows experience loss of pregnancy and infertility due to inadequate luteal function and/or failure of timely insemination. Results from our studies suggest that the incorporation of PGF2α and hCG or GH/IGF-1 protocols in buffalo cows to be beneficial for improving their breeding efficiency as these protocols are likely to increase luteal function with defined luteolysis. To summarize, the results of studies described in the present thesis provide new insights into the physiological and molecular mechanisms involved in the regulation of CL function during luteolysis in the monoovulatory species. The results suggest that the maintenance of CL function appears to be dependent on both luteotrophic and luteolytic factors, but with a varied degree of dominance between the two species examined. Further, the results indicate that while the luteotrophic factors (LH/CG) dominate the CL regulation in primates, the regulation of CL function in bovines is dominated by the actions of luteolytic factor (PGF2α). In monoovulatory species, the luteotrophic and luteolytic factors following binding to their specific plasma membrane receptors on the luteal cells, would counteract each other and modulate activation of various downstream signaling molecules subsequently leading to regulation of gene expression and P4 secretion (Fig.5.1). LH: luteinizing hormone; CG: chorionic gonadotropin; LH/CGR: LH/CG receptor; Gαs: stimulatory α-subunit of trimeric G-protein; AC: adenylate cyclase; cAMP: cyclic adenosine monophosphate; PKA: protein kinase A; p: phosphorylation: CREB: cAMP response element binding protein; SR-B1: scavenger receptor class B, type I; SF-1: steroidogenic factor 1; LRH-1: liver receptor homologue 1; P4; progesterone; Src; sarcoma; PDE4D: cAMP phosphodiesterase 4D; StAR, steroidogenic acute regulatory protein; PGF2α: prostaglandin F2α; PTGFR: PGF2α receptor; PLC: phospholipase C; CYP19A1: cytochrome P450 aromatase; PTGR1: Prostaglandin reductase 1; AREG: Amphiregulin; RTK: receptor tyrosine kinase; Akt: protein kinase B; FKHR: forkhead transcription factor; DAPL1: death associated protein like 1; ARG2: Arginase, type II Growth factor LH/CGR RR AC Gαs ? Gα TT P? Gα K PKP src cAMP ? P Akt PDE4D P PFKHR FKHR CREB P LRH-1CREB P SF-1 Genes associated with Genes associated with apoptosis ? CYP19A1, apoptosis SR-B1 PTGR1 DAPL1 SF-1, LRH-1 AREG ARG 2 P4 biosynthesis Apoptosis? P4 biosynthesis Apoptosis MONKEY BUFFALO COW Shown here is the diagram depicting intracellular signaling pathways regulated by luteotrophic factor (LH) and luteolytic factor (PGF2α) and their cross talk to counteract changes in the expressions of genes associated with the biosynthesis and secretion of P4 and apoptosis in the CL. In primates, LH/CG activates a multitude of intracellular signaling cascades, primarily Gαs/AC/cAMP/PKA/CREB leading to changes in gene expression. LH during early and mid luteal phase and CG during pregnancy maintain the activation of Src and PDE in an inhibitory state. However, during the late luteal phase of non-fertile cycle, results in present study suggests that activated Src levels and PDE activity increase, with accompanying decrease in cAMP and pCREB levels leading to concomitant decrease in SR-B1 expression, and in turn, P4 secretion. Surprisingly, regulation of apoptotic gene expression and CL regression are still unclear. In bovines, PGF2α of uterine origin mediates changes in luteal gene expression and results in decreased P4 secretion, principally by reduction in StAR level. The present study suggests that during luteolysis PGF2α affects the genes regulated by LH, by interfering with LH (and perhaps IGF-1) signaling leading to alteration in the expression of genes crucial for CL structure and function. (Pl refer the abstract file for figures)

As relações entre os fatores climáticos e as respostas fisiológicas de vacas lactantes são bastante conhecidas, porém sob condições de ambiente controlado. Este estudo teve como objetivo monitorar as respostas dos animais em instalações típicas para vacas leiteiras, para identificar o real impacto do ambiente climático sobre o animal. Foi proposto um método para avaliar o nível de estresse de vacas, que poderá servir como uma ferramenta simples, que traduza as sensações de conforto térmico dos animais. O experimento foi realizado em três fases, a saber: primavera (28 dias), verão (31 dias) e inverno (31 dias). Foram utilizados animais da raça Holandesa com produção média entre 20 a 25 kg leite/dia. Os animais foram alojados em instalação tipo free-stall com acesso livre a um piquete adjacente. Foram avaliadas a freqüência respiratória (FR), a temperatura retal (TR), a temperatura do pelame (TPE), a temperatura auricular (TAU), a temperatura da base da cauda (TCAU), a temperatura da vulva (TVU) e a produção de leite (PL). O ambiente foi monitorado 24 horas por dia, todos os dias, com registros da temperatura de bulbo seco (TBS), da umidade relativa (UR), da temperatura de ponto de orvalho e da temperatura de globo negro (TG). Posteriormente foram calculados os índices de temperatura e umidade (ITU) e o de temperatura de globo e umidade (ITGU). Todas as variáveis fisiológicas apresentaram padrão sazonal bem claro, com maiores valores durante as estações mais quentes (primavera e verão) e menores valores no inverno. A TAU, a TVU e a TCAU apresentaram correlações positivas com a TR, a FR e a TPE, o que indica uma associação entre estas variáveis. Porém estudos adicionais devem ser conduzidos para validar a aplicabilidade destas variáveis (TAU, TVU e TCAU) na caracterização do estresse térmico dos animais. A TPE e a FR foram as variáveis mais influenciadas pelo ambiente climático em todas as estações do ano. O ambiente noturno foi associado às variações da TR, da FR e da TPE, enquanto o ambiente do dia anterior não explicou a variação das respostas fisiológicas. Não houve evidência de efeitos de uma variável ambiental isolada sobre as variáveis fisiológicas, o que indicou a complexidade das relações entre o animal e o ambiente climático. Mesmo com ITU acima de 79, considerado estressante pela literatura estrangeira para vacas lactantes, não foram evidenciados valores estressantes para TR e FR e reduções na produção de leite. O modelo proposto neste trabalho para estimar presença ou ausência de estresse em vacas alojadas em free-stall, apresentou boa aderência ao conjunto de dados, com R&sup2; de 0,43. Dessa forma, disponibiliza uma ferramenta simples e rápida para produtores e técnicos, pela associação de duas medidas fisiológicas (FR e TPE) de fácil mensuração, ou então pela associação de duas variáveis ambientais (TBS e UR). Tal ferramenta diz respeito a uma amostra da população de vacas Holandesas alojadas em determinada instalação e região, o que condiciona o modelo proposto a outros estudos para sua validação em outros rebanhos e regiões. / It has been well known the relation between the environment and physiological answers of lactating dairy cows under controlled environmental conditions. The present study aimed to monitor the animal answers allocated at typical housing system to identify the real environmental impact over it. A method was proposed to evaluate the stress level of the animal, to be used as a tool to identify the sensations of thermal comfort. The experiment was conducted in three phases, in spring (28 days), summer (31 days) and winter (31 days) periods. Holstein dairy cows were used averaging milk yield around 20 to 25 kg/day. The animals were housed in a free stall shed with an open area. Respiratory rate (FR), rectal temperature (TR), surface skin temperature (TPE), internal ear temperature (TAU), tail temperature (TCAU), vulva temperature (TVU) and milk yield (PL) were evaluated. The environmental conditions were monitored during 24 hours every day, by recording the dry bulb temperature (TBS), relative humidity (UR), dew point temperature (Tpo) and black globe temperature (Tg). The calculation of temperature humidity index (ITU) and the black globe humidity index (ITGU) was based on these environmental variables. The physiological variables had a seasonal standard with higher values during hot periods (spring and summer) and lower values during the winter. The IET, VT and TT demonstrated positive correlations with RT, RR and SKT showing association between them. More studies are necessary to validate the applicability of these variables (IET, VT and TT) and to characterize heat stress in dairy cows. SKT and RR were the most influenced by the environment in all seasons. The night environment was associated to the RT, RR and SKT, while the day before environment did not explained the physiological variations. There was no evidence of isolated environmental variables over the physiological ones, showing the complexity between the animal and the environment. Even with the THI values above 79, what is considered stressful to dairy cows, there was no evidence of stressful values for RT and RR and of MY losses. The model proposed in this study to estimate presence or absence of heat stress in dairy cows avails a simple and fast tool to milk producers and technicians, where it could be associated two physiological variables (RR and SKT) of easy measurement or other two environment variables (DBT and RH). However, this result is related to the studied population at a specific housing system and situated at a specific region. Addiitonal studies must be conducted to validate the proposed model to others dairy herds and locations.

Estratégias de vedação tem sido adotadas com o intuito de reduzir a entrada de oxigênio para o interior dos silos. Aditivos químicos como o benzoato de sódio, que apresenta funções antimicrobianas também pode ser empregado para melhoria da estabilidade aeróbia de silagens. Porém, ainda não se sabe se pode causar efeitos adversos no consumo ou metabolismo dos animais alimentados e, consequentemente levar a alterações no desempenho animal. Desta forma no presente estudo, objetivou-se avaliar a influência de estratégias de vedação de silos trincheira sobre as perdas de MS e valor nutritivo de silagens de milho e, a adição de benzoato sódio na ração total no valor nutritivo para vacas leteiras. O experimento foi conduzido no Departamento de Zootecnia da Escola Superior de Agricultura \"Luiz de Queiroz\" (ESALQ/USP). A cultura do milho foi colhida com aproximadamente 35% de matéria seca (MS) e ensilada em silos trincheira (capacidade de 40 t). No momento do fechamento dos silos, dois tratamentos foram impostos: (1) lona dupla-face 200 &mu;m protegida com bagaço de cana-de-açúcar (camada com espessura de 10 cm) (BG) e, (2) aplicação superficial de benzoato de sódio 150 g/m2 (diluído em água 1:4) imediatamente antes da vedação com lona dupla-face 200 &mu;m (BZ). Vinte vacas Holandesas em lactação foram alocadas em cinco Quadrados Latinos 4 × 4 em períodos de 21 dias (14 d adaptação). As dietas experimentais continham (%MS): 8% de caroço de algodão, 9,5% de polpa cítrica, 18% de farelo de soja, 9,0% de milho moído seco, 2,5% premix mineral + vitaminas e 53% de silagem de milho: BG ou BZ ou silagem de milho BG + 0,15% de benzoato de sódio ou silagem de milho BZ mais 0,15% de benzoato de sódio. O benzoato de sódio foi diluído em água (0,3:1) e aspergido na ração total imediatamente antes de cada trato. Os dados foram submetidos à análise utilizando-se o procedimento MIXED do SAS, através de arranjo fatorial 2 × 2. A silagem com cobertura de bagaço de cana foi mais eficiente em reduzir a entrada de oxigênio durante o processo de fermentação e, consequentemente levou ao menor crescimento de microrganismos deterioradores e melhor conservação dos nutrientes da silagem, resultando em maior digestibilidade da MS. A adição de benzoato de sódio na dose de 0,15% na MN não altera o desempenho de vacas leiteiras. / Sealing strategies have been adopted to reduce oxygen entrance to silo. Chemical additives such as sodium benzoate have antimicrobial activity and it can also promote an aerobic stability on silage. Nevertheless it is still unknown if sodium benzoate supplementation on silage may affect animal consumption or cause deleterious effect on metabolism with influence on animal performance. The objective of this study was using different sealing strategies to assess dry matter loss and nutritional value on corn silage, and the influence of supplementing sodium benzoate on total mixed ration for dairy cattle. This trial was conducted at Animal Science Department of Luiz de Queiroz College of Agriculture (ESALQ/USP). Corn crop was harvested with 35% of dry matter (DM) and ensiled on horizontal silos (40 t capacity). A factorial design (2x2) for silo sealing and benzoate as an additive on dietary feed were evaluated. Silo sealing strategies were confected as follows: (1) Plastic film doubled-sized 200 &mu;m covered with bagasse (layer thickness 10 cm) (BG) and 2) application of sodium benzoate on top surface of ensiled mass pulverizing 150 g m-2 (dilution of 1:4) sealing it immediately with plastic film double-sided 200 &mu;m (BZ). After 343 days of storage, the silos were open and the lactation trial started. Two dietary treatments evaluated the addition sodium benzoate on feed mixture of total ration. Sodium benzoate was incorporated (+ 0.15 % on total feed) on corn silage from BG and BZ and no incorporation to BG and BZ were used as control treatment. Dietary sodium benzoate was diluted on water (0.3:1 ratio) and pulverized on total ration immediately before each meal. Feed formulation: 8% cottonseed meal, 9.5% citric pulp, 18% soybean meal, 9% dry corn meal, 2.5 % vitamin and mineral premix, and 53% of corn silage. Twenty Holstein cows lactating were allocated in five Latin squares (4 x 4) during 21 days (14 days to acclimate) and fed twice a day. Dry matter intake (DMI), milk yield and quality were recorded between day 15th and 21st from each experimental period. Data were subjected to MIXED procedure from SAS for factorial design (2x2). The silage with sugarcane bagasse coverage was more effective in reducing the oxygen input during the fermentation process and consequently led to lower growth of spoilage microorganisms and better conservation of silage nutrients, resulting in increased digestibility of dry matter. Adding 0.15 % of sodium benzoate on fresh matter diet doesn\'t affect the performance of dairy cows.