Les quantités importantes d’aliments consommés et la proportion élevée de concentrés devant être incorporée aux rations pour soutenir les besoins des vaches hautes-productrices induisent bien souvent des perturbations de l’équilibre ruminal. Ces changements se répercutent sur la biohydrogénation ruminale des acides gras insaturés de la ration, qui entraînent à leur tour une inhibition de la synthèse des matières grasses par le tissu mammaire. Plusieurs stratégies nutritionnelles ont été mises de l’avant pour mieux tirer profit des rations riches en concentrés. Récemment, des études ont montré la capacité du carbonate de potassium (K2CO3) à prévenir la chute de matière grasse associée à des régimes à forte teneur en concentrés. Toutefois, on comprend encore mal l’origine de ces effets. Les travaux de cette thèse visaient donc, dans un premier temps, à départager si les effets observés en ajoutant du K2CO3 aux rations des vaches laitières étaient dus à une augmentation de la différence alimentaire cation anion (DACA), de la teneur en ions K+ ou encore du pouvoir tampon de la ration. Un autre objectif de cette thèse était de déterminer les effets d’un ajout de K2CO3 sur la synthèse de matières grasses du lait lorsque des sources d’acides gras polyinsaturés (AGPI) sont introduites dans l’alimentation de la vache laitière. Enfin, les travaux cherchaient à déterminer l’effet d’un ajout de K2CO3 à la ration sur les populations microbiennes du rumen, particulièrement celles reconnues pour être impliquées dans le métabolisme lipidique. Pour répondre à ces questions, une première expérience a été mise en place, où 35 vaches Holstein en début de lactation ont été distribuées selon un plan en blocs complets aléatoires. La période expérimentale était de 28 jours et précédée d’une collecte de 5 jours (covariable). Les cinq rations expérimentales étaient constituées en vue de départager les effets du K2CO3 (témoin vs K2CO3), de la capacité tampon (K2CO3 vs KHCO3), de la DACA (K2CO3 vs KCl) et du type de cations (K2CO3 vs Na2CO3). Dans cette expérience, et contrairement aux études antérieures, l’ajout de K2CO3 aux rations riches en concentrés n’a pas permis d’augmenter la production de lait ou la matière grasse des vaches en début de lactation. De plus, les résultats suggèrent qu’une augmentation du K alimentaire via l’ajout de K2CO3 pourrait induire un déséquilibre ionique cellulaire qui pourrait affecter le transport des nutriments dans les cellules épithéliales mammaires et ainsi affecter la synthèse du lait. Une seconde expérience a ensuite été menée, où 28 vaches Holstein en début de lactation ont été distribuées selon un plan en blocs complets aléatoires. La période expérimentale était également de 28 jours et précédée d’une collecte de 5 jours (covariable). Les quatre rations expérimentales étaient offertes selon un arrangement factoriel 2 × 2, soit 0 ou 1,5 % K2CO3 et 0 ou 2 % d’huile de soya, comme source d’acides gras polyinsaturés. Les résultats ont montré que l’ajout de K2CO3 peut entraîner une augmentation de la sécrétion des matières grasses laitières chez des animaux recevant de grandes quantités de concentrés. Cette augmentation dépend toutefois de la teneur en lipides de la ration. Cette étude a également permis de mettre en lumière une relation positive entre la production laitière et la teneur en chlore du lait. Lors de cette seconde expérience, des échantillons de contenu ruminal ont également été prélevés chez 24 vaches (n = 6) afin d’étudier l’impact d’un supplément de K2CO3 sur l’environnement et les populations microbiennes du rumen des vaches en début de lactation recevant des rations riches en concentrés avec ou sans huile de soya. Ces travaux ont permis de comprendre que le K2CO3 et l’huile de soya ont des effets distincts sur les populations microbiennes. L’ajout de K2CO3 a stimulé la croissance de Butyrivibrio hungatei, bactérie productrice de 18:1 trans-11. L’ajout d’huile de soya a, quant à elle, réduit la présence de Butyrivibrio/Pseudobutyrivibrio, un groupe de bactéries productrices de 18:1 trans-11, de Fibrobacter succinogenes, une bactérie fibrolytique, de Butyrivibrio proteoclasticus, une bactérie productrice de 18:0, et de Streptococcus bovis, une bactérie amylolytique Les travaux regroupés dans cette thèse apportent un éclairage nouveau sur le rôle de la supplémentation minérale sur les performances de production des vaches laitières / Negative energy balance typically appears in early-lactation dairy cows as a consequence of a reduction of dry matter intake, as well as of an increase in energy demand for milk production. To compensate this energy deficit, cows are fed with high-concentrate diets. However, highly fermentable carbohydrates introduced in diets can result in a decreased milk fat synthesis. Previous studies reported that addition of potassium carbonate (K2CO3) to high-concentrate diets helps to maintain milk fat, although the mechanism is yet to be established. Consequently, the objective of the current thesis was, firstly, to investigate the effects of dietary cation-anion difference (DCAD), cation source, and buffering ability of the mineral supplement on rumen biohydrogenation of fatty acids (FA) and production performance of dairy cows fed a high-concentrate diet. Secondly, this thesis aimed at evaluating the effect of K2CO3 on production performance, biohydrogenation of fatty acids, and mineral composition of milk in early-lactation dairy cows fed a high-concentrate diet with or without soybean oil (SBO), as a source of polyunsaturated fatty acid. A third objective of this thesis was to evaluate the effect of K2CO3 supplementation, in diets containing soybean oil (SBO) on rumen microbial population associated with lipid metabolism. Consequently, a first experiment was set up, where 35 early-lactation Holstein cows were used in a randomized complete block design with 33-d periods, including a 5-d pretreatment collection period used as a covariate. Five different dietary treatments were used to assess the effects of K2CO3 (control vs. K2CO3), buffering ability (K2CO3 vs. KHCO3), DCAD (K2CO3 vs. KCl), and cation type (K2CO3 vs. Na2CO3). In this experiment, and as opposed to previous studies, supplementing high-concentrate diets with K2CO3 did not increase milk or milk fat yield in early-lactation cows. Also, results suggested that increasing dietary K through the addition of K2CO3 could lead to a disequilibrium in cellular ion composition that can impair nutrient transport into and out of the mammary epithelial cells, and consequently affect milk synthesis. A second experiment was conducted where 28 ruminally fistulated Holstein cows were used in a randomized complete block design. The experiment lasted 33 d, including a 5-d pre-treatment collection period used as a covariate. Experimental treatments were arranged as a 2 × 2 factorial with 0 or 1.5% K2CO3 and with 0 or 2% SBO. Results of this experiment revealed that potential effect of K2CO3 on milk fat synthesis is dependent on the levels of dietary polyunsaturated FA. Moreover, a positive relation was established between milk Cl concentration and milk yield, suggesting that the equilibrium of this ion is linked to the efficiency of lactogenesis Finally, rumen samples were collected from the rumen of 24 cows enrolled in the second experiment (n = 6) to assess treatment effects on rumen microbial population associated with lipid metabolism. Feeding K2CO3 and SBO had distinct effects on rumen bacteria. Dietary K2CO3 stimulated the growth of Butyrivibrio hungatei, a bacterium recognized to produce trans-11-18:1 during biohydrogenation. Conversely, feeding SBO reduced the growth of Butyrivibrio/Pseudobutyrivibrio bacterium group, known to produce trans-11-18:1, of Fibrobacter succinogenes, a fibrolytic bacterium, of Butyrivibrio proteoclasticus, a bacterium involved in 18:0 production, and of Streptococcus bovis, an amylolytic bacterium. Overall, the experiments conducted and reported in this thesis provide new insights on the impact of mineral supplementation on milk performance in dairy cows.

In 1704 Hedvig Eleonora, the dowager queen of Sweden, commissioned a portrait of herself and her great-grandson, Karl Fredrik, the duke of Holstein-Gottorp, four years of age. The portrait by court portraitist David von Krafft is quite formal in style, and alludes to other royal portraits in a number of dynastic symbols and visual conventions although it is unusual in its composition and subject-matter. There are two very similar copies of this painting, one in the collections of the Swedish National Museum, and one in Schloss Eutin in Germany. The Swedish painting has attracted little interest from art historians and has not been exhibited for many years. The aim of this study is to analyse the paiting in its historical, political and dynastic context. What was the purpose of the painting and what message was it to convey? A comprehensive comparision of royal portraits, commissioned in the late 1600:s and early 1700:s, reveals that many have visual conventions and status-enhancing details in common. However, the double-portrait differs from them in some important aspects. The composition of the portrait was most probably carefully considered. Hedwig Eleonora was an experienced art commissioner after 60 years of shaping the dynastic image-building of her son Charles XI and grandson Charles XII. She was also well versed in the visual use of symbolism and dynastic symbols. When the portrait was painted the unmarried king Charles II had been away in war for several years. The question of succession was pressing and the double-portrait can be read as a visual opinion piece on behalf of one of two possible heirs to the throne, the young Karl Fredrik. The young boy was the current duke of of Holstein Gottorp and the dowager queen herself was born a princess of Holstein-Gottorp. The double-portrait testifies to her life-long efforts to forward the cause of the dukedom. Perhaps it is also a testament to her failure. The king fought a long, wrenching war and when he died, another regent was chosen.

Com o objetivo de avaliar o processo de secagem da glândula mamária de vacas da raça Holandesa foram examinadas 44 mamas na fase final da lactação, durante a evolução do processo de secagem (dia da última ordenha; 1º, 3º, 5º, 7º, 10º, 15º, 30º e 45º dia do período seco), assim como no retorno à lactação. Antes da colheita das amostras, a glândula mamária era submetida a minucioso exame clínico por inspeção e palpação, sendo complementado pela avaliação do aspecto da secreção láctea. Após os primeiros jatos da secreção terem sido desprezados, procedia-se a sua colheita asséptica, para ser utilizada no exame microbiológico, seguida da colheita das amostras destinadas à avaliação das seguintes características físico-químicas e celulares: pH, eletrocondutividade, cloretos, lactose, gordura, proteína, sólidos totais, cálculo do índice cloreto/lactose, California Mastitis Test - CMT e do número de células somáticas. O processo de secagem determinou alterações na consistência da mama, pois no retorno da lactação a freqüência de glândulas classificadas como sendo do Tipo III (firme) foi maior do que a observada antes do início da secagem e no 45ºdia do período seco, e, favoreceu a recuperação dos tetos nos quais era perceptível a presença de prolapso de pequena severidade do orifício do teto, em contrapartida, o processo de secagem não influenciou na recuperação de prolapsos considerados de grande severidade, levando a conclusão que este grau de prolapso torna-se irreversível, mesmo após longos períodos sem ordenha. Numa fase inicial do processo de secagem, a abrupta retenção do leite determinou o aumento do grau de distensão da mama e dos tetos, sendo que, durante a primeira semana, observou-se uma gradual diminuição desta distensão e, a partir do 10° dia do período seco, verificou-se o aumento progressivo na freqüência de mamas e tetos não distendidos, nas quais o processo de involução havia chegado ao seu final. No decorrer do processo de involução constatou-se que o leite foi substituído por uma secreção aquosa de coloração branca ou creme clara; sendo que a partir do 7º dia, também foi observada a presença de secreção com aspecto viscoso de coloração amarelada; ao final do processo, no 45º dia do período seco, observou-se em 40,9 % das mamas uma secreção pré-colostral, com aspecto de mel ou soro lácteo. Durante o período seco, em animais, nos quais a supressão da ordenha tenha ocorrido há mais de três dias, foram observadas alterações similares àquelas descritas nas mamites diagnosticas durante a lactação ou nas retenções de leite, ou seja, observou-se um aumento abrupto dos valores do pH, eletrocondutividade, cloretos, índice cloretos/lactose, proteína e número de células somáticas, enquanto os teores lácteos de lactose diminuíram abruptamente. Entre o 3º e o 45º dia do período seco foram obtidos os seguintes valores para as características físico-químicas e celulares da secreção láctea de vacas sadias: pH entre 7,08 e 7,34; Eletrocondutividade entre 7,50 e 8,35 mS/cm; Cloretos entre 242,20 e 287,66 mg/dl; Lactose entre 1,20 e 2,45 g/dl; Índice Cloretos/Lactose entre 12,99 e 26,40; Gordura entre 2,27 ± 7,97 g/dl; Proteína entre 6,00 e 9,47 g/dl; Sólidos Totais entre 10,73 e 16,35 g/dl; Número de Células Somáticas entre 1.930.450 e 6.486.900 células/ml. A partir do 5º dia do período seco nenhuma das amostras apresentou reações negativas ao CMT e entre o 7º e o 45º dia todas as amostras apresentavam reações do CMT classificadas como duas ou três cruzes. A avaliação da influência da ocorrência de mamite durante o processo de secagem nas características físico-químicas e celulares da secreção láctea demonstrou ser ela parcial e restrita a alguns momentos do período seco, sendo que as diferenças entre os valores obtidos no grupo de mamas com mamite e no grupo com mamas sadias eram de pequena magnitude, impedindo o diagnóstico baseado na avaliação dos resultados obtidos nas características físico-químicas e celulares da secreção láctea.Entre a última ordenha antes do seu início e o 45ºdia do período seco não houve diferenças estatísticas entre as freqüências de isolamentos bacterianos, enquanto o percentual de mamas com isolamento bacteriano no retorno da lactação foi menor do que o encontrado durante o processo de secagem da glândula mamária. / In order to evaluate the involution of the mammary gland of Holstein cows, we examined 44 udders at the end of lactation, during the dry period (last milking, and days 1, 3, 5, 7, 10, 15, 30 and 45 of the dry period), as well as the return to lactation. The mammary glands were thoroughly examined by inspection and palpation before the collection of samples. The lacteal secretion was also inspected. After discarding the first jets of the lacteal secretion, the samples for the microbiological analysis were aseptically collected, followed by the samples for the evaluation of the physicochemical and cellular characteristics - pH, electrical conductivity, chlorides, lactose, fat, protein, total solids, chloride/lactose ratio, California Mastitis Test (CMT) and somatic cell count. The involution process was accompanied by alterations in the consistency of the udder. On the return to lactation, the frequency of udders that were classified as Type III (firm) was higher than that observed before the beginning and on the 45th day of the dry period. The involution process also favored the recovery of the teats, but it did not have any effect over severe prolapses of the teat orifices, leading us to the conclusion that severe prolapses are irreversible, even after long periods without milking. On the initial phase of the dry period, the sudden retention of milk caused a distension, of the udder and of the teats, that gradually decreased along the first week. After the 10th day of the dry period, there was an increase in the number of udders and teats that were no longer distended, indicating that the involution process had ended. Along the process of involution of the mammary gland, we observed that the milk was replaced by a white or cream colored secretion; from the 7th day, a viscous and yellowish secretion was also observed; at the end of the process, on the 45th day, we observed that 40.9% of the udders were producing a pre-colostrum secretion that looked like honey or whey. During the dry period, after the 3rd day of the cessation of lactation, the cows had alterations consistent with those observed in mastitis during lactation or milk retentions. There was a sudden increase in pH, in electrical conductivity, in chlorides, in the chloride/lactose ratio, in protein and in the somatic cell count, as well as a sudden decrease in the lactose content. We observed the following values for the physicochemical and cellular characteristics of the lacteal secretion of healthy cows between the 3rd and the 45th day of the dry period: pH - between 7.08 and 7.34; Electrical Conductivity - between 7.50 and 8.35 mS/cm; Chloride - between 242.20 and 287.66 mg/dl; Lactose - between 1.20 and 2.45 g/dl; Chloride/Lactose Ratio - between 12.99 and 26.40; Fat - between 2.27 and 7.97 g/dl; Protein - between 6.00 and 9.47 g/dl; Total Solids - between 10.73 and 16.35 g/dl; Somatic Cell Count - between 1,930,450 and 6,486,900 cells/ml. From the 5th day of the dry period, none of the samples had negative reactions to the CMT; and between the 7th and the 45th day, all samples had a distinct positive or a strong positive reaction to the CMT. The influence of mastitis during the involution of the udder over the physicochemical and cellular characteristics of the lacteal secretion was partial and restricted to certain moments of the dry period. The differences between the values of these characteristics in udders with or without mastitis, was very small, so these analyses can not be used to diagnose mastitis. There was no statistical difference between the frequency of bacteria isolated from the last milking and from the 45th day of the dry period. The percentage of bacteria isolated from the udders was lower on the return to lactation than during the involution of the mammary gland.

A curva de lactação é a descrição gráfica da produção de leite em dado período de tempo, normalmente descrita por modelos matemáticos dos quais podem ser obtidos fatores multiplicativos de predição e estimativas de interesse econômico como o pico, persistência e produção acumulada aos 305 dias. Entretanto, faz-se necessário a seleção de funções de curvas para que as estimativas obtidas apresentem o menor erro de predição associado, bem como, identificar os fatores que influenciam a curva de lactação para que essas estimativas sejam desprovidas de tais fontes de variação. Desta forma, foram utilizadas cinco funções não lineares para modelar 10.679 lactações pertencentes a vacas holandesas, de grupo genético PCOD (puro por cruza de origem desconhecida), PCOC (puro por cruza de origem conhecida) e PO (puro de origem), pertencentes a 38 rebanhos agrupados em três níveis de produção, situados nos estados de São Paulo e Minas Gerais no período de 1997 a 2009. A seleção da função baseou-se simultaneamente no maior valor do coeficiente de determinação e nos menores valores do quadrado médio do erro de predição, raiz quadrada do quadrado médio do erro de predição, critério bayesiano de informação e percentual de curvas atípicas. Independente do nível de produção e ordem de lactação, dentre os modelos avaliados, a função de Wood obteve o melhor ajuste e, portanto, foi utilizada para obter estimativas de pico, tempo de ascensão ao pico, persistência e produção acumulada aos 305 dias. Posteriormente, avaliou-se a influência de fatores ano de parto, época de parto, ordem de lactação, rebanho, nível de produção e duração da lactação sobre os parâmetros a (produção inicia), b (taxa de acréscimo na produção até o pico) e c (taxa de decréscimo na produção após o pico de lactação) e estimativas de pico, tempo de pico, persistência e produção acumulada aos 305 dias das curvas de lactação modeladas pela função de Wood. Em seus respectivos níveis de produção, as médias dos parâmetros e estimativas aumentaram proporcionalmente às classes de duração da lactação e maiores estimativas foram observadas para multíparas na época seca do ano. Dado o exposto, para os rebanhos em estudos, fatores de predição da produção de leite aos 305 dias podem ser construídos de acordo com o nível de produção, ordem, época e duração da lactação. / The lactation curve is a graphic depiction of milk production in a given period of time, usually described by mathematical models which can be obtained by multiplicative factors of prediction and estimates of economic interest as the peak, persistence and cumulative production to 305 days. However, it is necessary to select the functions of curves obtained for the estimates have the smallest prediction error associated, as well as to identify factors that influence the lactation curve for these estimates are devoid of these sources of variation. Thus, five were used to model nonlinear functions belonging to 10,679 lactations Holsteins, genetic group PCOD (pure by crosses of unknown origin), PCOC (pure by crosses of known origin) and PO (pure original), belonging to 38 herds grouped in three levels of production, located in São Paulo and Minas Gerais from 1997 to 2009. The function selection was based on both the greater coefficient of determination and lower values of mean square prediction error, the square root of mean square prediction error, Bayesian information criterion and the percentage of atypical curves. Regardless of the level of production and parity among the models evaluated, the function of Wood obtained the best fit and therefore was used to estimate the peak, rise time to peak, persistence and cumulative production to 305 days. Subsequently, we evaluated the influence of year of birth, season of calving, lactation order, herd production level and duration of lactation on the parameters a (production starts), b (rate of increase in production to peak) and c (rate of decline in production after peak lactation) and estimates of peak, peak time, persistence and cumulative production to 305 days of lactation curves modeled by the function of Wood. In their production levels, the mean estimates of parameters and increased proportionally to the classes of lactation length and higher estimates were observed for multiparous in the dry season. Given the above, for livestock studies, predictors of milk production to 305 days can be constructed according to the level of production, order, timing and duration of lactation.

Este experimento foi realizado com objetivo de se avaliar os efeitos da suplentação com os energéticos propileno glicol, propionato de cálcio e "Dairy Power Drench ?" no período pré e pós-parto de vacas leiteiras sobre: a) variação do escore de condição corporal (ECC); b) variação de peso; c) produção de leite, d) parâmetros de eficiência reprodutiva e e) concentração plasmática dos ácidos graxos livres (AGL). Para este estudo, foram utilizadas 165 fêmeas da raça Holandesa (132 vacas e 33 novilhas) de dois rebanhos comerciais. As parições destes animais ocorreram entre 15 de março a 15 de junho de 1999. Os animais foram distribuídos em quatro grupos: grupo C-Controle com 41 animais; grupo DR- com 42 animais que receberam 3 aplicações de "Dairy Power Drench ?" no pós-parto; grupo PC- com 39 animais que receberam 500g diários de propionato de cálcio, iniciando em média 11 dias antes da data do parto até 49 dias pós-parto; grupo PG com 43 animais que receberam 500mL diários de propileno glicol, iniciando em média 13 dias antes da data do parto e continuando até o 51 o dia pós-parto. A avaliação da condição corporal foi feita semanalmente, usando-se a escala de 1 a 5 e o peso foi aferido com auxílio da fita barimétrica, ambos no mesmo dia e pela mesma pessoa. A mensuração individual da produção de leite e a colheita de sangue para avaliação da concentração de ácidos graxos livres foram realizados semanalmente. O parâmetro reprodutivo, dias para primeiro cio pós-parto, foi realizado por observação visual, realizada duas vezes ao dia. Os dados foram submetidos à análise de variância que separou como causas de variação efeito de tratamento e efeito dos blocos formados em função da fazenda (Fazenda 1 e 2) e do números de partos (primíparas ou multíparas). As análises referentes aos valores de produção de leite, escore de condição corporal, peso vivo, variação diária do peso corporal e concentração de ácidos graxos livres foram acrescidos do fator medidas repetidas no tempo (semanas). A comparação entre as médias dos tratamentos foi realizada através do teste de Tukey. Não foi observado efeito de interação de tempo x tratamento sobre a variável escore de condição corporal. Entretanto, houve uma tendência (P<0,08) de efeito de tratamento e efeito quadrático de tempo (P<0,01). As vacas que receberam "Drench" tenderam a apresentar uma condição corporal 6% superior ao grupo que recebeu propileno glicol. Já a variação da condição corporal (ECC6 - ECC1) não sofreu efeito de tratamento. Para o peso corporal e variação diária de peso não foi observado efeito dos tratamentos, nem interação entre tempo x tratamento. Entretanto, sofreram efeito de tempo de comportamento quadrático (P<0,01 e P<0,05, respectivamente). As vacas produziram em média 27,3 kg de leite/dia, sendo observado efeito de interação tempo x tratamento (P<0,01) sobre esta variável. Porém, dentro de cada semana, as possíveis diferenças não foram detectadas. Os tratamentos não afetaram os parâmetros de eficiência reprodutiva. Encontrou-se em média 69,5 dias para o aparecimento do primeiro cio, 2,23 serviços/concepção e 172,6 dias para o período de serviço. As concentrações médias dos ácidos graxos livres encontradas durante o período experimental foram de 376,6 µeq/L, não se observando efeitos de interação tempo x tratamento ou de tratamento. Porém, sofreram efeito de tempo (P<0,01) com comportamento linear (P<0,01), decrescendo 48,2 µeq/L por semana. / The objective of this trial was to evaluate the effects of propylene glycol, calcium propionate and "Dairy Power Drench ?" supplementation on pre and postpartum period of Holstein cows. Parameters studied were: a) body condition score variation (BCS); b) body weight variation; c) milk production, d) reproduction efficiency and e) nonesterified fatty acids concentration (NEFA). One hundred and sixty and five animals were used (132 cows and 33 heifers) from two commercial herds. Parturitions started on March 15 th and ended on June 15 th of 1999. Animals were allocated in four groups: group C-Control (41 animals); group DR- (42 animals) with administration of "Dairy Power Drench ?" (once a day for 3 days) during postpartum period; group PC-(39 animals) with daily administration of calcium propionate (500g), starting 11 days (in average) prior to parturition and ending 49 days postpartum; group PG (43 animals) with daily administration of propylene glycol (500mL), starting 13 days (in average) prior to parturition and ending 51 days postpartum. The evaluation of BCS was done weekly, using a five-point scale over values from 1 to 5 and body weight was also measured, on the same day, by the same person. Milk production was measured individually and blood was sampled weekly. The parameter days to postpartum first detected estrus was done visually, twice a day. Variance analysis separated as variation sources the effect of treatments and blocks in function of farms (Farm 1 and 2) and parity (primiparous or multiparous). Analyses referred to milk production, body condition score, body weight, daily variation of body weight and nonesterified fatty acids concentration were added with repeated measures factor (weeks). Treatments were compared using Tukey's test. Interaction between time (weeks) and treatment was not found for BCS, however, there was a tendency (P<0.08) of treatment effect and quadratic effect of time (P<0.01). Supplementation of "Drench" tended to cause a body condition score 6% higher compared to supplementation of propylene glycol. But the variation of BSC (BSC6 -BSC1) was not affected by treatments. Body weight and its variation were not affected by treatment or interaction time x treatment. However, there was a quadratic effect of time (P<0.01 and P<0.05, respectively). Milk production average was 27.3 kg/day and an interaction time x treatment was found (P<0.01) on this parameter. But inside of each week, the possible differences were not detected. Treatments also did not affect reproductive efficiency parameters. On average, days to postpartum first detected estrus were 69.5, service/conception was 2.23 and service period was 172.6 days. Nonesterified fatty acids concentration average was 376.6 µeq/L and there was no effect of interaction time x treatment or treatment. But there was a linear effect (P<0.01), decreasing 48.2 µeq/L per week.

<p>Urea kao deo neproteinske frakcije azota mleka, predstavlja krajnji produkt metabolizma proteina u predželucima preživara. Portalnim krvotokom toksični amonijak, nastao mikrobiolo&scaron;kom razgradnjom proteina u rumenu dolazi do jetre gde se transformi&scaron;e u ureu, koja kasnije krvotokom dospeva u mleko. Ishrana, odnosno sadržaj sirovih proteina u obroku ima najveći uticaj na sadržaj uree u mleku. Sadržaj uree sve vi&scaron;e se koristi kao parametar pomoću kojeg je moguće pratiti unos sirovih proteina i energije obrokom kod mlečnih krava. Pored ishrane na sadržaj uree u mleku utiču i drugi faktori, kao &scaron;to su sezona, prinos mleka, stadijum laktacije, paritet i dr.<br />Plodnost krava je veoma važna osobina mlečnih goveda na koju utiče veliki broj faktora. Dosada&scaron;nja istraživanja u ovoj oblasti ukazuju na moguću vezu između plodnosti krava i sadržaja uree u mleku.<br />Određivanje sadržaja uree u mleku primenom infracrvene spektrofotometrije u analizi mleka prilikom redovne mesečne kontrole mlečnosti krava pružilo je nove mogućnosti u praćenju kvaliteta mleka.<br />Cilj ovog istraživanja bio je da se utvrdi:<br />1. variranje sadržaja uree u mleku unutar stada,<br />2. uticaj paragenetskih faktora (farma, sistem proizvodnje, sistem držanja, sezona, redni broj laktacije i stadijum laktacije) na sadržaj uree u mleku,<br />3. korelacija sadržaja uree sa parametrima mlečnosti krava i brojem somatskih ćelija i<br />4. korelacija između sadržaja uree u mleku i dužine servis perioda.</p><p>U okviru ovog istraživanja analizirano je 46.315 uzoraka mleka, u okviru redovne kontrole mlečnosti, sa 11 farmi sa područija Vojvodine. Od kojih je jedna sa organskom, a 10 farmi sa konvencionalnom proizvodnjom. Određivanje sadržaja uree u mleku vr&scaron;eno je na aparatu MilcoScan.<br />Prosečan sadržaj uree u mleku (25,18 mg/dl) bio je u okviru optimalnih vrednosti sadržaja uree u mleku. Koeficijent varijacije za sadržaj uree (34,15%) bio je znatno veći od koeficijenta varijacije za ostale sastojke mleka.<br />Dobijeni rezultati u okviru ove doktorske disertacije ukazuju da najveći uticaj na sadržaj uree u mleku ima menadžment farme. Utvrđen je i statitički značajan uticaj ostalih ispitivanih paragenetskih faktora.<br />Sistem držanja statistički značajno utiče na sadržaj uree u mleku. Niži sadržaj uree u mleku bio je kod krava u slobodnom sistemu držanja.<br />Kao posledica specifičnosti organske proizvodnje konstatovane su statistički značajne razlike između organske i konvencionalne proizvodnje mleka. Razlike se ogledaju u smanjenom sadržaju uree u mleku i prinosu mleka, a povećanom sadržaju mlečne masti i proteina. Broj somatskih ćelija u mleku iz organske proizvodnje je znatno manji u odnosu na broj istih u mleku iz konvencionalne proizvodnje mleka, dok je servis period u posmatranom periodu bio duži kod krava u organskoj proizvodnji u odnosu na krave u konvencionalnoj proizvodnji mleka.<br />Posmatrano po sezonama kontrole najniži sadržaj uree u mleku bio je u jesenjem periodu (22,19 mg/dl), a najveći u letnjem period (27,11 mg/dl). Razlike u sadržaju uree po laktacijama su male, ali statistčki značajne.<br />Konstatovan je statistički značajan uticaj stadijuma laktacije na sadržaj uree u mleku. Najniži sadržaj bio je na početku laktacije (23,05 mg/dl), a maksimalan sadržaj uree u mleku od 26,40 mg/dl, bio je od 121 do 180 dana laktacije.<br />Utvrđene su pozitivne, statistički visoko značajne, korelacije između sadržaja uree i pojedinih sastojaka mleka, kao i između sadržaja uree i prinosa mleka. Korelacija između sadržaja uree i broja somatskih ćelija u mleku je negativna i visoko statistički značajna.<br />U okviru ovog istraživanja utvrđena je pozitivna i statistički visoko značajna korelacija između sadržaja uree u mleku i dužine servis perioda.<br />Dobijeni rezultati, tumačeni u kontekstu drugih istraživanja na ovu temu ukazuju na veliki značaj praćenja sadržaja uree u mleku, koji može doprineti pobolj&scaron;anju menadžmenta ishrane i reprodukcije na farmama mlečnih krava, a sve u cilju smanjenja tro&scaron;kova na farmama, kroz smanjenje tro&scaron;kova ishrane i tro&scaron;kova veterinarskih usluga.</p> / <p>Urea as a part of non-protein fraction of nitrogen in milk represents the final product of protein metabolism in the rumen of ruminants. By portal bloodstream toxic ammonia comes into liver where it is transformed into urea, which comes later into milk by bloodstream. Nutrition and contents of crude proteins in the diet have the greatest influence on the milk urea content. The content of milk urea has been increasingly used as a parameter by which it is possible to monitor balance of energy and crude proteins in the feed of dairy cows.<br />Apart from feeding, milk urea content can be influenced by some other factors as season, milk yield, stage of lactation, parity etc.<br />A great number of factors influence cow&rsquo;s fertility. Previous research in this field has indicated a possible relationship between the fertility of cows and urea content in milk.<br />Determination of urea content in milk, by infrared spectrophotometric, on monthly bases, for milk recording porpoises, offers new opportunities for milk quality monitor.<br />The aim of this study was to determine:<br />1. Variations of milk urea content within the herd,<br />2. The influence of paragenetic factors (a farm, production and housing system, season, parity and stage of lactation) on the milk urea content,<br />3. The correlation with milk urea content and parameters of milk yield as well as the somatic cells count,<br />4. The correlation between the milk urea content and the length of open days.<br />This research includes 46,315 samples of milk which were analysed as regular milk recording samples from 11 farms in Vojvodina. There are 10 farms with</p><p>conventional and only one farm with organic production.<br />Determination of the milk urea contents was carried out by MilkoScan FT+.<br />In the analyzed milk samples the average milk urea content (25.18 mg / dl) was within the optimum values. The coefficient of variation for the milk urea content (34.15%) was significantly higher than the coefficient of variation for the other ingredients in milk.<br />The obtained results in this PhD thesis indicate that the management of a farm has the greatest influence on the content of milk urea. Statistically some significant influence of other examined paragenetic factors was found.<br />According to statistics the housing system significantly influences the milk urea content. Lower milk urea content was found in cow&#39;s milk in free-stall system.<br />As the result of specific organic production some statistically significant differences between organic and conventional milk production were found. The differences shows lower milk urea content and milk yield, as well as higher milk fat and protein content. The somatic cells count in organic milk production is significantly lower than their number in milk from conventional milk production. The open days during observation period were longer in cows from an organic dairy farm then the cows from conventional dairy farms.<br />According to season and stage of lactation an important influence on milk urea was found. The seasonal observation shows the lowest milk urea content in autumn period (22.19 mg / dl) and the highest in summer period (27.11 mg / dl). The lowest content was at the beginning of lactation (23.05 mg / dl) and the maximum milk urea content (26.40 mg /dl) was from 121 to 180 days of lactation. Differences in the milk urea content between lactation were small, but statistically significant.<br />There are positive and statistically significant, correlations between the milk urea content and some ingredients of milk, as well as between milk urea content and milk yield. The correlation between the milk urea content and somatic cells count in milk is negative and high statistically significant.<br />It is shown in this research that high milk urea content has negative impact on the length of open days.<br />Obtained results, interpreted in the context of other studies on the same subject indicate the great importance of the observation of the milk urea content. It can contribute to improving the feeding and reproduction on dairy farms, and lead to reduction of both feeding and veterinary costs.</p>

Originally presented as the author's Thesis (doctoral)--Johan Wolfgang von Goethe-Universität Frankfurt am Main, 1976. / Includes bibliographical references (p. 275-280). Also issued online.

No description available.

A multiple trait, random regression, test day (TD) model was used to determine the heritability and genetic correlations of milk, fat, protein, and SCS with metritis, cystic ovary disease, mastitis, lameness, ketosis, milk fever, and displaced abomasum for four periods in lactations 1, 2, and 3-5 using two disease definitions. Definition 1 assumed that the first disease occurrence affects all TD thereafter equally and definition 2 assumed that disease affects only the next TD. Results were similar between definitions. The models were modified to allow the estimation of differences in disease occurrence by level of production, and to estimate production differences between diseased and non-diseased cows. Few significant associations were found between production levels and disease occurrence, the largest was between MAST and SCS. Diseased animals had lower levels of production than healthy animals for all diseases except COD. Animals with MAST had increased SCS. / Natural Sciences and Engineering Research Council (NSERC). Dairy Cattle Genetics Research and Development (DairyGen) Council.

Imported genetic material of the Holstein-Friesian breed from overseas (OS), mainly from North America, has been used in New Zealand (NZ) since the late 1960's. This has diluted the genetic base of the former NZ Friesian genotype selected under intensive seasonal pasture-based systems. As a result, increased concerns have been raised about the negative influence of these overseas genes on the modern NZ Holstein- Friesian, as it is apparent that the OS Holstein-Friesian has a lower capacity to perform on grazed pasture. The objective of the present thesis was to investigate differences in production performance between three Holstein-Friesian genotypes farmed at different feed allowances (FA) on pasture-based systems; in addition, to investigate differences in the grazing process between strains under contrasting managements and sward conditions, and so to identify animal and pasture factors that affect the herbage intake (DMIH) and performance of the grazing cow. An accurate procedure was also established to estimate DMIH for cows fed forage and maize supplements, grazing in groups. Two modern high breeding worth (BW) Holstein-Friesian strains from NZ (NZ90) or overseas (OS90) origin and a low BW 1970's NZ Friesian genotype (NZ70) were farmed in two field experiments: (1) a long-term 'system' study that compared the yield performance of these genotypes in a range of systems with different feed allowance (FA) per cow, and a (2) a short-term 'component' study that compared the grazing capacity of the strains under contrasting sward conditions but at a common daily herbage allowance. The differences in productive performance between genotypes increased as the study progressed in the system study, with the largest observed in the last season. The mean milksolids (MS) yield per cow and per hectare were higher in NZ90 (395 kg cow-1 and 1,236 k ha-1) than in the NZ70 (336 kg cow-1 and 1,093 kg ha-1) and the OS90 (377 kg cow-1 and 1,154 kg ha-1). The higher production of NZ90 cows was supported by their higher mean daily MS yield than the NZ70 (1.45 vs. 1.21 kg MS cow-1 day-1) and more days in milk than OS90 cows (271 vs. 257 DIM). The lower lactation length of the OS90 strain occurred due to its lower body condition score (BCS) in late lactation, which determined an early dry-off for these cows. The lowest BCS of OS90 at the nadir (irrespective of FA), during lactation and at dry-off indicate these cows mobilised greater amount of body reserves and partitioned most of the energy ingested to yield. Genotype by FA interactions for milk and lactose yields, protein content in the milk and BCS were observed in the second and third seasons of the 'system' study. Milk yield increased as FA increased to a greater extent in OS90 than in the two NZ strains, whereas the content of solids in milk, particularly protein, increased to a greater extent for NZ90 than in both OS90 and NZ70. During lactation DMIH was higher for NZ90, intermediate in OS90 and lower in NZ70 (14.5, 13.9 and 12.6 kg DM cow-1 day-1 respectively for NZ90, OS90 and NZ70, as measured with nalkanes), and declined as lactation progressed, with a smaller difference for the total intake achieved (15.5, 15.2 and 13.1 kg DM cow-1 day-1 respectively) due to the increased supplement consumption. These results indicate that the OS90 needs more feed with a higher proportion of supplement in the diet to improve productive performance on pasture-based systems; the NZ90 would perform better when cow nutrition is mainly supported by grazing pasture, although further increments in performance could be expected from strategic supplementation, but requiring more feed than NZ70. The DMIH per unit of live weight (DMIH/LW) was highest in NZ90 strain in both the 'system' and in the short sward of the 'component' study (31.5 and 31.1 g DM kg-1 DM in NZ90 vs. 28.9 and 28.6 g DM kg-1 DM for OS90 in 'system' and 'component' studies respectively). The higher intake of NZ90 on pasture was sustained by a higher capacity to graze short swards than NZ70 and OS90, and to deal with the herbage of higher bulk density and lower quality present at the base of taller swards. The NZ90 can maintain DMIH in swards with different structures, indicating higher flexibility to perform under different managements and sward conditions. The size of the jaw is smaller in NZ90 than OS90 (88.4 vs. 92.4 mm) with effects on bite area and bite size, and this flexibility to adapt the size of the bite to swards of different structure may improve bite penetration under constraining sward conditions. The reduced ability of the OS90 to adjust ingestive behaviour to different swards would limit the capacity of this strain to perform on pasture. The fact that OS90 cows increased DMIH and DMIH/LW substantially in a leafy and taller sward (up to 21.6 kg cow-1 and 40.8 g DM kg-1Lw vs. 19.2 kg cow-1 and 41.0 g DM kg-1Lw in NZ90 during early lactation) suggests that yield performance can be improved in these cows even on pasture, by fine-tuning pasture management.