The dairy industry today is beginning to dedicate more focus on the growth of the calf from birth to first breeding to better improve the milk production as well as the overall performance of the individual cows. While the development of the rumen is one of the most vital contributors to the performance of the calf, it remains unknown what molecular mechanisms are responsible for the development of the rumen, and more specifically the proliferation of rumen epithelial cells. The objectives of this study were to investigate the existing data on rumen development through meta-analysis and to explore the effects of sodium butyrate and lipopolysaccharide (LPS) on rumen development in calves through experiment. In the first study a meta-analysis was performed to summarize the literature on calf performance and derive equations that relate rumen (e.g., rumen pH, reticulorumen weight, papillae area) and non-rumen factors (e.g., feed composition, form of feed, housing) to animal performance (e.g., intake of milk replacer (MR), starter, and forage; average daily gain (ADG); and feed efficiency). We looked at four different relationships to further investigate the connections between rumen, non-rumen, and performance factors. In the first and second relationships of interest, the effect of dietary and environmental variables on rumen variables and performance variables were examined, respectively. The third relationship of interest was how rumen variables influenced performance variables. The final relationship of interest was investigating the additive effects of the rumen, dietary, and environmental variables on the performance variables. Forward selection, multiple regression was used to derive equations to select variables that explained variation in the response variable in each model. Results showed that the variation in calf ADG was explained by daily forage intake, calves that were weaned, total starter intake, and total MR intake (concordance correlation coefficient (CCC) = 0.976). The variation in feed to gain ratio was explained by the weight of the ruminal contents, daily forage, MR, and starter intakes, percent of starter in the diet, and total starter intake (CCC = 0.992). The variation in daily forage intake was explained by the percent of the diet that was starter or MR (CCC = 0.998). The variation in daily starter intake was explained by the percent of acid detergent fiber in the starter, a pelleted starter (versus a texturized), diets including starter and forage (versus a milk replacer only diet), and the percent of the diet that was MR (CCC = 0.998). The variation in daily MR intake was explained by the percent of the diet that was starter, final body weight, ruminal propionate concentration, and daily starter intake (CCC = 0.918). Based on these analyses, although dietary and environmental factors are closely associated with calf performance, ruminal factors such as volatile fatty acid (VFA) concentration and ruminal contents appear to have additional, additive influences on calf performance. In the second study, 24 Holstein bull calves were challenged with oral doses of LPS and sodium butyrate. The hypothesis here was that LPS and sodium butyrate would instigate rumen cell proliferation independently and additively. Calves were assigned to one of four treatments: control (CON; n=5), butyrate (BUTY; n=5), LPS only (LPS-O) (n=6), or LPS plus butyrate (LPSB; n=6). All treatments were administered orally twice daily consisting of either: 0.9% saline (CON); 11 mM sodium butyrate (BUTY); LPS ranging from 2.5 to 40 µg/kg metabolic body weight (BW0.75, LPS), or both butyrate and LPS (LPSB). Calves were fed milk replacer (22% CP, 20% fat, as-fed) and starter (20% CP, 3% fat, as-fed) based on metabolic BW, or about 12% BW of MR and 3% BW of starter. Feed intake, fecal and respiratory scores, and rectal temperature were recorded daily. Calf BW, hip height, jugular blood samples, and rumen content samples (via oroesophageal tube) were collected weekly. Calves were weaned at 6 wk of age and euthanized at 8 wk of age, whereupon ruminal weights and ruminal samples for papillae area and epithelial thickness were collected. Blood and rumen samples were analyzed for concentrations of beta-hydroxybutyrate, glucose, LPS-binding protein, and VFA. Data were analyzed as a 2x2 factorial with the repeated effect of week. Three non-orthogonal contrasts (CON versus the average of all other treatments; LPS-O versus LPSB, and LPSB versus BUTY) were investigated. Feed intake, health measures, and blood metabolites did not differ by treatment. Calf BW increased by week (P < 0.0001). Irrespective of week, LPS calves weighed more and had higher ADG than BUTY calves (P = 0.020). Irrespective of week, withers height was greater in LPS compared to CON (P = 0.006). Rumen pH and rumen VFA concentrations did not differ by treatment but did decrease and increase, respectively, with week in conjunction with increased starter intake. Total empty forestomach (P = 0.014) and reticulorumen weights (P = 0.012) were greater in LPSB compared to BUTY. Overall, LPS and sodium butyrate appeared to have synergistically affected some, but not all rumen measurements without affecting calf growth, intake, or health. Results from the meta-analysis emphasize the importance of continuing to focus on the solid feed intake of the calf from birth through weaning. Implications from the LPS study are imperative to other dairy scientists who will attempt to further study the effects of LPS on the rumen. / Master of Science in Life Sciences / Dairy calves are born with an under-developed stomach. The stomach has four compartments: the rumen, reticulum, omasum, and abomasum. The rumen is the largest component where finger-like projections called papillae grow to absorb nutrients for the calf. It is vital to the calf that the rumen develops not only the papillae to absorb nutrients but also to foster a microbe-rich environment so the microbes can act as a defense mechanism for the calf to aid in fighting disease. While it is known that things like solid feed support the development of the rumen, the mechanism behind how that is happening still remains unclear in the literature. The objective of this study was first to better understand the relationships that exist in the literature between dietary, environmental, and ruminal factors, and second to investigate the claim that certain components of the bacteria in the rumen are stimulating rumen development independently and additively with sodium butyrate. In order to investigate the relationships amongst the dietary, environmental, and ruminal parameters, a computer program called R Studio was used to analyze over 30 different models that extracted data from a database that included a collection of 36 studies from the literature. This is also known as a meta-analysis. The associations of interest that we found were: average daily gain (ADG) of the calf was associated with daily forage intake, calves that were weaned, total starter intake, and total MR intake. Feed efficiency of the calf was associated with the weight of the ruminal contents, daily forage, milk replacer (MR), and starter intakes, percent of the diet composed of starter, and total starter intake. Daily forage intake was associated with the percent of the diet that was starter or MR. Daily starter intake was associated with acid detergent fiber in the starter, a pelleted starter (versus a texturized starter), diets including starter and forage (versus a MR only diet), and the percent of the diet that was MR. Daily MR intake was associated with the percentage of the diet that was starter, final body weight (BW), ruminal propionate concentration, and daily starter intake. These relationships emphasized that although dietary and environmental factors are more closely associated with calf performance, ruminal factors such as rumen contents and volatile fatty acid concentrations appear to have additional, additive influences on calf performance. The second part of the study objective was to explore an idea that, to our knowledge, has not been published in the literature. In the second study, 24 dairy calves were challenged with oral doses of a gram-negative bacteria lipopolysaccharide (LPS), and a short-chain fatty acid sodium butyrate. The hypothesis in this study was that the LPS and sodium butyrate would trigger metabolic pathways on the rumen cell membranes to a greater extent together, versus independently, to increase the amount of cells growing. Calves were assigned to one of four treatments: control (CON), butyrate (BUTY), LPS only (LPS-O), or LPS plus butyrate (LPSB). To study this effect, each treatment group was administered their respective treatment orally as a liquid twice daily. To measure the results, the following data was collected: feed intake, fecal and respiratory scores, rectal temperature BW, hip and withers height, blood samples, rumen content and pH samples, papillae area, epithelial thickness, and organ weights. Blood and rumen samples were analyzed for blood metabolites and volatile fatty acids concentrations respectively. Data were analyzed and results showed no difference amongst feed intake, health measures, rumen pH, rumen VFA concentration, and blood metabolites by treatment. Calves on the LPS treatment weighed more and had higher ADG than BUTY treatment calves. Withers height was higher in the LPS group when compared to CON. Stomach weights were higher in the LPSB group when compared to the BUTY group.

No description available.

Foram conduzidos dois experimentos com objetivo de avaliar o efeito da substituição do milho moído por diferentes co-produtos da indústria sobre o desempenho e metabolismo de bezerros em aleitamento. No primeiro experimento, 24 bezerros da raça Holandês foram distribuídos em três tratamentos, de acordo com o nível de inclusão de polpa cítrica desidratada (PC): (1) concentrado contendo 64% de milho e 0% de PC (0PC); (2) concentrado contendo 32% de milho e 32% de PC (50PC); e (3) concentrado contendo 0% de milho e 64% de PC (100PC). No segundo experimento, 36 bezerros da raça Holandês foram distribuídos em quatro tratamentos, de acordo com o nível de inclusão de melaço de cana líquido (ME) e xarope de glicose (XG): (1) concentrado contendo 65% de milho, 0% de ME e 0% XG (0ME); (2) concentrado contendo 60% de milho e 5% ME (5ME); (3) concentrado contendo 55% de milho e 10% de ME (10ME); e (4) concentrado contendo 60% de milho e 5% de XG (5XG). Os animais de ambos os experimentos receberam diariamente 4 L de sucedâneo lácteo, além de concentrado e água ad libitum. O consumo do concentrado e o escore fecal foram controlados diariamente. Semanalmente os animais foram pesados e tiveram as medidas corporais aferidas. Amostras de sangue foram colhidas semanalmente para determinação de glicose, lactato e ?-hidroxibutirato. Amostras de fluído ruminal foram colhidas nas semanas 4, 6 e 8 para determinação de pH, N-amoniacal e ácidos graxos de cadeia curta (AGCC). Na oitava semana de vida os animais foram abatidos para avaliação do desenvolvimento do trato digestório superior (peso e volume dos compartimentos e tamanho, área e número das papilas ruminais). No primeiro experimento não houve diferença entre tratamentos (P>0,05) para as variáveis de consumo, desempenho, parâmetros sanguíneos e ruminais, exceto para a concentração de butirato, onde os tratamentos 50PC e 100PC apresentaram maior (P<0,05) concentração que 0PC. Este resultado está relacionado ao maior (P<0,05) peso do trato digestório superior total, maior proporção do retículo-rúmen e área das papilas ruminais dos tratamentos com inclusão de PC, uma vez que o butirato é o principal AGCC estimulador do desenvolvimento ruminal. Dessa forma, a substituição parcial ou total do milho por PC no concentrado inicial não altera o desempenho de bezerros leiteiros, podendo ainda apresentar efeitos positivos no metabolismo ruminal e desenvolvimento do trato digestório superior. No segundo experimento não houve efeito de tratamento (P>0,05) para as variáveis de consumo, desempenho e escore fecal. Porém, observou-se aumento (P<0,05) na concentração total de AGCC, acetato e propionato do tratamento 5ME quando comparado à 0ME, sendo que os demais não diferiram de 5ME e 0ME. Essa alteração no metabolismo ruminal não foi acompanhada (P>0,05) por mudanças nos parâmetros sanguíneos ou de desenvolvimento do trato digestório superior. Pode-se concluir que a substituição do milho por 5 e 10% de ME ou 5% de XG no concentrado não prejudica o desenvolvimento corporal de bezerros leiteiros, sendo uma alternativa ao uso do milho na composição de dietas sólidas para esta classe animal. / Two studies were conducted to evaluate the effect of replacing corn grain by co-products, on the performance and changes in the metabolism of dairy calves. In the first study, 24 Holstein calves were divided into three groups, according to level of inclusion of citrus pulp (CP): (1) starter containing 64% corn and 0% CP (0CP), (2) starter containing 32% corn and 32% CP (50CP), and (3) starter containing 0% corn and 64% CP (100CP). In the second study, 36 Holstein calves were allocated four treatments according to level of inclusion of liquid sugar cane molasses (MO) or glucose syrup (GS): (1) starter containing 65% corn, 0% MO and 0% GS (0MO), (2) starter containing 60% corn and 5% MO (5MO), (3) starter containing 55% corn and 10% MO (10MO), and (4) starter containing 60% corn and 5% GS (5GS). The animals of both experiments received 4 L milk replacer daily. Starter and water were provided ad libitum. Starter intake and fecal score were monitored daily. Weekly, the animals were weighed and had their body measurements monitored until eight weeks. Blood samples were taken weekly for glucose, lactate and ?-hydroxybutyrate analysis. Ruminal fluid samples were collected at weeks 4, 6 and 8 of age to pH, ammonia-N and short chain fatty acids (SCFA) determination. In the eighth week of life animals were slaughtered to evaluate the development of the upper digestive tract (weight and volume of the compartments, as well as size, area and number of ruminal papillae). In the first experiment there were no differences among treatments (P>0.05) for starter intake, performance, ruminal and blood parameters, except for the concentration of butyrate, where treatments 50CP and 100CP had higher concentration (P<0.05) than 0CP. This result is related to the higher (P<0.05) weight of total upper digestive tract, proportion of the reticulum-rumen and rumen papillae area of treatments including CP, since butyrate is the main SCFA stimulating rumen development. Thus, the partial or total replacement of corn by citrus pulp in the starter does not change the performance of calves, and may present positive effects on ruminal metabolism and development of the upper digestive tract. In the second study there was no effect of the starter composition (P>0.05) for starter intake, performance or fecal scores. However, there was an increase (P<0.05) in the total SCFA, acetate and propionate concentration for treatment 5MO compared to 0MO, whereas the other treatments did not differ from 5MO and 0MO. This change in ruminal metabolism was not accompanied (P>0.05) by changes in blood parameters and development of the upper digestive tract. It may be concluded that the substitution of corn for 5 and 10% MO or 5% GS in the starter has no detrimental effect on body development of dairy calves, being an alternative to the use of corn in solid feed composition for these animals.

O objetivo deste estudo foi avaliar o efeito da substituição de milho por glicerina bruta no concentrado inicial, sobre o desempenho e alterações no metabolismo energético de bezerros em aleitamento. Vinte e quatro bezerros da raça Holandês recém-nascidos foram alojados em abrigos individuais até a 8a semana de vida, com livre acesso à água, sendo alimentados com 4 litros de sucedâneo/dia e concentrado ad libitum. Os animais foram distribuídos em blocos casualizados de acordo com a data de nascimento e peso ao nascer, e alocados em um dos seguintes tratamentos, de acordo com a inclusão de glicerina em substituição ao milho no concentrado inicial: 1) 0% Glicerina bruta; 2) 5% Glicerina bruta; 3) 10% Glicerina bruta. O aleitamento foi realizado duas vezes ao dia (07 e 17h) com sucedâneo comercial (22% proteína bruta; 19% extrato etéreo). O consumo de concentrado inicial e o escore fecal foram registrados diariamente, enquanto que a pesagem e as medidas de altura na cernelha, perímetro torácico e largura da garupa foram realizadas semanalmente, a partir da segunda semana, até a oitava semana. A partir da segunda semana, foram realizadas colheitas semanais de amostras de sangue, duas horas após o aleitamento da manhã, para determinação das concentrações plasmáticas de glicose, lactato, proteínas totais e &beta;-hidroxibutirato (BHBA). Nas semanas 4, 6 e 8 de idade foram colhidas amostras de fluido ruminal, utilizando-se sonda oroesofágica e bomba a vácuo, para determinação do pH e ácidos graxos de cadeia curta (AGCC). Na oitava semana, se encerrou o período experimental e os animais foram abatidos para avaliação do desenvolvimento do trato digestório superior e de papilas ruminais. O consumo de concentrado inicial, o ganho de peso diário e o peso vivo não apresentaram diferenças (P>0,05) entre os tratamentos. As medidas corporais, não apresentaram diferenças significativas (P>0,05). A média encontrada dos escores fecais durante todo o período experimental sugere baixa frequência de diarreia nos animais. Dentre os parâmetros ruminais avaliados, apenas o propionato e a relação acetato:propionato foram afetados (P<0,05) pelos tratamentos, apresentando menores valores de propionato em animais consumindo concentrado com 5% de glicerina bruta e menor relação acetato:propionato encontrados para os animais recebendo glicerina, este último em resposta ao tipo de fermentação do glicerol. Os parâmetros sanguíneos avaliados (glicose, BHBA, lactato e proteínas totais), não foram afetados pelos diferentes tratamentos (P<0,05), apresentando valores adequados. O peso total do trato digestório superior, os pesos médios de cada compartimento e a capacidade máxima do retículo-rúmen não foram afetados pelos tratamentos, assim como os parâmetros de desenvolvimento do epitélio ruminal. A glicerina pode ser utilizada como ingrediente energético alternativo até a taxa de 10% de substituição ao milho do concentrado inicial de bezerros leiteiros no período de aleitamento sem afetar o crescimento, o desenvolvimento ou o metabolismo do animal. / The purpose of this study was to evaluate the effect of the replacement of corn by crude glycerin in the starter concentrate on performance and energy metabolism of dairy calves. Twenty-four newborns Holstein calves were housed in individual shelters until the eighth week of age, fed 4 liters of milk / day and ad libitum water and concentrate. The animals were distributed in randomized blocks according to the birth date and birth weight, and assigned to one of the following treatments, in accordance with the inclusion of glycerin replacing corn in the starter concentrate: 1) 0% Crude glycerin, 2) 5% Crude glycerin; 3) 10% Crude glycerin. Milk-feeding was performed twice daily (07 and 17h) with commercial milk replacer (22% crude protein, 19% ether extract). The initial feed intake and fecal scores were recorded daily, while weighing and measurements of height at withers, heart girth and hip width were measured from second week to eighth week. From the second week of age, blood samples were collected once a week, two hours after morning feeding, for determination of plasma glucose, lactate, total proteins and &beta;-hydroxybutyrate (BHBA) concentrations. Ruminal fluid was collected at 4, 6 and 8 weeks using an oro-ruminal probe and a suction pump for determination of pH and short-chain fatty acids (SCFA). At the end of eighth week of life, animals were slaughtered to evaluate development of the upper digestive tract and rumen papillae. Feed intake, average daily gain and body weight did not differ (P>0.05) among treatments. No differences was observed for body measurements (P>0.05). The fecal scores suggested low frequency of severe diarrhea in animals. Among the ruminal parameters, only propionate and acetate: propionate ratio were affected (P<0.05) by treatments, with smaller amounts of propionate for animals fed concentrate containing 5% of crude glycerin; and lower acetate: propionate ratio for animals receiving glycerin, because of the type of glycerol fermentation. Blood parameters (glucose, BHBA, total protein and lactate) were not affected by treatments (P<0.05), presenting adequate values. The total forestomach weight, the average weight of each compartment and the maximum capacity of reticulum-rumen were not affected by treatments, as well as the parameters for ruminal epithelium development. Crude glycerin can be used as an alternative energy source replacing corn up to 10% in the starter concentrate for milk-feeding dairy calves without affecting growth, development or animal metabolism.

Free-access acidified milk feeding is increasingly being adopted to feed dairy and veal calves. Acidification is used to preserve milk and facilitate free-access feeding. There is, however, little controlled research to support the adoption of free-access acidified milk feeding over traditional feeding programs. The objectives of this thesis were to describe the preweaned calf management and feeding practices used on dairy farms in Ontario, Canada, and to investigate the effects of milk replacer acidification and free-access feeding on the productivity and welfare of calves. A total of 140 Ontario dairy producers participated in a cross-sectional study and were surveyed about on-farm calf management and feeding practices. Results from this study documented that there are currently a range of management practices and several different feeding programs being used on farms. Colostrum and milk feeding management are the areas where the most progress has been made in recent years; however, several other aspects of calf management and feeding still warrant improvement. A pilot study was conducted to examine the effects of milk replacer acidification and free-access feeding on the nutrient intake, growth, rumen papillary development and behaviour of calves. A field study was designed to evaluate the effects of a free-access acidified milk replacer feeding program on the pre and postweaning health and growth of dairy and veal calves. A randomized controlled study was completed to investigate how milk replacer acidification, under free-access feeding conditions, affects the pre and postweaning performance and health of veal calves. Results from these studies demonstrated that milk replacer acidification limited calves’ intake of milk replacer by approximately 1 L/d, resulted in more fragmented feeding behaviour, promoted earlier solid feed intake and tended to support improved respiratory health, but had little impact on rumen development or long-term calf performance. Moreover, free-access feeding facilitated larger intakes of milk, resulted in fewer signs of hunger or frustration, and supported greater preweaning growth, but delayed the onset of solid feed consumption and appeared to negatively affect rumen development, compared to restricted feeding. Collectively, these results demonstrate that free-access acidified milk feeding promotes greater early life productivity and enhances calf welfare. / Ontario Ministry of Agriculture, Food and Rural Affairs, Dairy Farmers of Ontario, Ontario Veal Association, National Sciences and Engineering Research Council, Grober Nutrition and 3M Canada

O objetivo deste estudo foi avaliar o efeito da substituição de milho por glicerina bruta no concentrado inicial, sobre o desempenho e alterações no metabolismo energético de bezerros em aleitamento. Vinte e quatro bezerros da raça Holandês recém-nascidos foram alojados em abrigos individuais até a 8a semana de vida, com livre acesso à água, sendo alimentados com 4 litros de sucedâneo/dia e concentrado ad libitum. Os animais foram distribuídos em blocos casualizados de acordo com a data de nascimento e peso ao nascer, e alocados em um dos seguintes tratamentos, de acordo com a inclusão de glicerina em substituição ao milho no concentrado inicial: 1) 0% Glicerina bruta; 2) 5% Glicerina bruta; 3) 10% Glicerina bruta. O aleitamento foi realizado duas vezes ao dia (07 e 17h) com sucedâneo comercial (22% proteína bruta; 19% extrato etéreo). O consumo de concentrado inicial e o escore fecal foram registrados diariamente, enquanto que a pesagem e as medidas de altura na cernelha, perímetro torácico e largura da garupa foram realizadas semanalmente, a partir da segunda semana, até a oitava semana. A partir da segunda semana, foram realizadas colheitas semanais de amostras de sangue, duas horas após o aleitamento da manhã, para determinação das concentrações plasmáticas de glicose, lactato, proteínas totais e &beta;-hidroxibutirato (BHBA). Nas semanas 4, 6 e 8 de idade foram colhidas amostras de fluido ruminal, utilizando-se sonda oroesofágica e bomba a vácuo, para determinação do pH e ácidos graxos de cadeia curta (AGCC). Na oitava semana, se encerrou o período experimental e os animais foram abatidos para avaliação do desenvolvimento do trato digestório superior e de papilas ruminais. O consumo de concentrado inicial, o ganho de peso diário e o peso vivo não apresentaram diferenças (P>0,05) entre os tratamentos. As medidas corporais, não apresentaram diferenças significativas (P>0,05). A média encontrada dos escores fecais durante todo o período experimental sugere baixa frequência de diarreia nos animais. Dentre os parâmetros ruminais avaliados, apenas o propionato e a relação acetato:propionato foram afetados (P<0,05) pelos tratamentos, apresentando menores valores de propionato em animais consumindo concentrado com 5% de glicerina bruta e menor relação acetato:propionato encontrados para os animais recebendo glicerina, este último em resposta ao tipo de fermentação do glicerol. Os parâmetros sanguíneos avaliados (glicose, BHBA, lactato e proteínas totais), não foram afetados pelos diferentes tratamentos (P<0,05), apresentando valores adequados. O peso total do trato digestório superior, os pesos médios de cada compartimento e a capacidade máxima do retículo-rúmen não foram afetados pelos tratamentos, assim como os parâmetros de desenvolvimento do epitélio ruminal. A glicerina pode ser utilizada como ingrediente energético alternativo até a taxa de 10% de substituição ao milho do concentrado inicial de bezerros leiteiros no período de aleitamento sem afetar o crescimento, o desenvolvimento ou o metabolismo do animal. / The purpose of this study was to evaluate the effect of the replacement of corn by crude glycerin in the starter concentrate on performance and energy metabolism of dairy calves. Twenty-four newborns Holstein calves were housed in individual shelters until the eighth week of age, fed 4 liters of milk / day and ad libitum water and concentrate. The animals were distributed in randomized blocks according to the birth date and birth weight, and assigned to one of the following treatments, in accordance with the inclusion of glycerin replacing corn in the starter concentrate: 1) 0% Crude glycerin, 2) 5% Crude glycerin; 3) 10% Crude glycerin. Milk-feeding was performed twice daily (07 and 17h) with commercial milk replacer (22% crude protein, 19% ether extract). The initial feed intake and fecal scores were recorded daily, while weighing and measurements of height at withers, heart girth and hip width were measured from second week to eighth week. From the second week of age, blood samples were collected once a week, two hours after morning feeding, for determination of plasma glucose, lactate, total proteins and &beta;-hydroxybutyrate (BHBA) concentrations. Ruminal fluid was collected at 4, 6 and 8 weeks using an oro-ruminal probe and a suction pump for determination of pH and short-chain fatty acids (SCFA). At the end of eighth week of life, animals were slaughtered to evaluate development of the upper digestive tract and rumen papillae. Feed intake, average daily gain and body weight did not differ (P>0.05) among treatments. No differences was observed for body measurements (P>0.05). The fecal scores suggested low frequency of severe diarrhea in animals. Among the ruminal parameters, only propionate and acetate: propionate ratio were affected (P<0.05) by treatments, with smaller amounts of propionate for animals fed concentrate containing 5% of crude glycerin; and lower acetate: propionate ratio for animals receiving glycerin, because of the type of glycerol fermentation. Blood parameters (glucose, BHBA, total protein and lactate) were not affected by treatments (P<0.05), presenting adequate values. The total forestomach weight, the average weight of each compartment and the maximum capacity of reticulum-rumen were not affected by treatments, as well as the parameters for ruminal epithelium development. Crude glycerin can be used as an alternative energy source replacing corn up to 10% in the starter concentrate for milk-feeding dairy calves without affecting growth, development or animal metabolism.

Foram conduzidos dois experimentos com objetivo de avaliar o efeito da substituição do milho moído por diferentes co-produtos da indústria sobre o desempenho e metabolismo de bezerros em aleitamento. No primeiro experimento, 24 bezerros da raça Holandês foram distribuídos em três tratamentos, de acordo com o nível de inclusão de polpa cítrica desidratada (PC): (1) concentrado contendo 64% de milho e 0% de PC (0PC); (2) concentrado contendo 32% de milho e 32% de PC (50PC); e (3) concentrado contendo 0% de milho e 64% de PC (100PC). No segundo experimento, 36 bezerros da raça Holandês foram distribuídos em quatro tratamentos, de acordo com o nível de inclusão de melaço de cana líquido (ME) e xarope de glicose (XG): (1) concentrado contendo 65% de milho, 0% de ME e 0% XG (0ME); (2) concentrado contendo 60% de milho e 5% ME (5ME); (3) concentrado contendo 55% de milho e 10% de ME (10ME); e (4) concentrado contendo 60% de milho e 5% de XG (5XG). Os animais de ambos os experimentos receberam diariamente 4 L de sucedâneo lácteo, além de concentrado e água ad libitum. O consumo do concentrado e o escore fecal foram controlados diariamente. Semanalmente os animais foram pesados e tiveram as medidas corporais aferidas. Amostras de sangue foram colhidas semanalmente para determinação de glicose, lactato e ?-hidroxibutirato. Amostras de fluído ruminal foram colhidas nas semanas 4, 6 e 8 para determinação de pH, N-amoniacal e ácidos graxos de cadeia curta (AGCC). Na oitava semana de vida os animais foram abatidos para avaliação do desenvolvimento do trato digestório superior (peso e volume dos compartimentos e tamanho, área e número das papilas ruminais). No primeiro experimento não houve diferença entre tratamentos (P>0,05) para as variáveis de consumo, desempenho, parâmetros sanguíneos e ruminais, exceto para a concentração de butirato, onde os tratamentos 50PC e 100PC apresentaram maior (P<0,05) concentração que 0PC. Este resultado está relacionado ao maior (P<0,05) peso do trato digestório superior total, maior proporção do retículo-rúmen e área das papilas ruminais dos tratamentos com inclusão de PC, uma vez que o butirato é o principal AGCC estimulador do desenvolvimento ruminal. Dessa forma, a substituição parcial ou total do milho por PC no concentrado inicial não altera o desempenho de bezerros leiteiros, podendo ainda apresentar efeitos positivos no metabolismo ruminal e desenvolvimento do trato digestório superior. No segundo experimento não houve efeito de tratamento (P>0,05) para as variáveis de consumo, desempenho e escore fecal. Porém, observou-se aumento (P<0,05) na concentração total de AGCC, acetato e propionato do tratamento 5ME quando comparado à 0ME, sendo que os demais não diferiram de 5ME e 0ME. Essa alteração no metabolismo ruminal não foi acompanhada (P>0,05) por mudanças nos parâmetros sanguíneos ou de desenvolvimento do trato digestório superior. Pode-se concluir que a substituição do milho por 5 e 10% de ME ou 5% de XG no concentrado não prejudica o desenvolvimento corporal de bezerros leiteiros, sendo uma alternativa ao uso do milho na composição de dietas sólidas para esta classe animal. / Two studies were conducted to evaluate the effect of replacing corn grain by co-products, on the performance and changes in the metabolism of dairy calves. In the first study, 24 Holstein calves were divided into three groups, according to level of inclusion of citrus pulp (CP): (1) starter containing 64% corn and 0% CP (0CP), (2) starter containing 32% corn and 32% CP (50CP), and (3) starter containing 0% corn and 64% CP (100CP). In the second study, 36 Holstein calves were allocated four treatments according to level of inclusion of liquid sugar cane molasses (MO) or glucose syrup (GS): (1) starter containing 65% corn, 0% MO and 0% GS (0MO), (2) starter containing 60% corn and 5% MO (5MO), (3) starter containing 55% corn and 10% MO (10MO), and (4) starter containing 60% corn and 5% GS (5GS). The animals of both experiments received 4 L milk replacer daily. Starter and water were provided ad libitum. Starter intake and fecal score were monitored daily. Weekly, the animals were weighed and had their body measurements monitored until eight weeks. Blood samples were taken weekly for glucose, lactate and ?-hydroxybutyrate analysis. Ruminal fluid samples were collected at weeks 4, 6 and 8 of age to pH, ammonia-N and short chain fatty acids (SCFA) determination. In the eighth week of life animals were slaughtered to evaluate the development of the upper digestive tract (weight and volume of the compartments, as well as size, area and number of ruminal papillae). In the first experiment there were no differences among treatments (P>0.05) for starter intake, performance, ruminal and blood parameters, except for the concentration of butyrate, where treatments 50CP and 100CP had higher concentration (P<0.05) than 0CP. This result is related to the higher (P<0.05) weight of total upper digestive tract, proportion of the reticulum-rumen and rumen papillae area of treatments including CP, since butyrate is the main SCFA stimulating rumen development. Thus, the partial or total replacement of corn by citrus pulp in the starter does not change the performance of calves, and may present positive effects on ruminal metabolism and development of the upper digestive tract. In the second study there was no effect of the starter composition (P>0.05) for starter intake, performance or fecal scores. However, there was an increase (P<0.05) in the total SCFA, acetate and propionate concentration for treatment 5MO compared to 0MO, whereas the other treatments did not differ from 5MO and 0MO. This change in ruminal metabolism was not accompanied (P>0.05) by changes in blood parameters and development of the upper digestive tract. It may be concluded that the substitution of corn for 5 and 10% MO or 5% GS in the starter has no detrimental effect on body development of dairy calves, being an alternative to the use of corn in solid feed composition for these animals.

La présente étude visait à déterminer les effets de l'âge de sevrage sur les performances de croissance, le développement du rumen et le microbiote chez les chevreaux alpins. Soixante-douze chevreaux ont été assignés au hasard par paires mâle et femelle à l'un des trois traitements. 1) sevrage précoce (EW), à l'âge de 6 semaines, 2) sevrage moyen (MW), à l'âge de 8 semaines (MW) et 3) sevrage tardif (LW), à 10 semaines d’âge (LW). Le lait de remplacement a été proposé ad libitum jusqu'à la semaine de sevrage, où le lait a été réduit de 12.5 % par jour pendant sept jours. Deux semaines après la naissance, du concentré, du foin et de l'eau ont été offerts à volonté jusqu'à l'âge de 12 semaines où les chevreaux ont été abattus. La consommation a été enregistrée quotidiennement et le poids corporel (PC) a été enregistré chaque semaine. Pour évaluer le développement du rumen, des échantillons de sang ont été prélevés pendant tout l'essai et analysés pour le β-hydroxybutyrate sanguin (BHB) et les acides gras non estérifiés (NEFA). Les mesures ruminales ont été prises à la semaine 12 avec les trente-six mâles seulement. Le contenu du rumen a été obtenu pour l'analyse de la composition bactérienne en utilisant la région V4 du gène de l'ARNr 16S et la qPCR a été utilisée pour quantifier les bactéries, les protozoaires et les champignons. Les papilles du rumen ont été analysées dans 4 régions du rumen : atrium du rumen (RA), sac ventral (VS), Cul-de-sac caudo-dorsal (DS) et Cul-de-sac caudo-ventral (VBS). Les chevreaux sevrés à 10 semaines, contre 8 semaines et 6 semaines avaient un gain quotidien moyen plus élevé pour la semaine post-sevrage (0.35 vs. 0.24 vs. 0.24 kg/j) et étaient plus lourds à la 12e semaine (27.44 vs. 25.45 vs. 24.07 kg, P< .05). Chez les animaux LW, le PC n'a pas été affecté pendant la période post-sevrage; probablement en raison d'un apport élevé en énergie métabolisable (EM) causé par la stratégie de sevrage contrairement à ce que nous observons chez les animaux EW et MW. Les taux sanguins de BHB ont augmenté au moment du sevrage pour tous les traitements, mais étaient plus élevés chez les chevreaux EW par rapport aux chevreaux MW (+ 21 %) et LW (+ 41 %) (P< .05). Les taux sanguins de NEFA chez les chevreaux EW ont augmenté au sevrage et étaient plus élevés que MW (+ 40 %) et LW (+ 101 %) chez les chevreaux (P< .05), suggérant une mobilisation plus prononcée du tissu adipeux chez les chevreaux sevrés précocement au sevrage. La population de microbiote en post-sevrage a montré que si le sevrage était retardé, l'abondance des bactéries totales semblait augmenter (P< .05) par rapport aux animaux EW, tandis que les protozoaires et les champignons diminuaient pour les LW. L'âge du sevrage semble induire des modifications du microbiote ruminal au cours du post-sevrage. Les mesures d'absorptiométrie à rayons X à double énergie (DEXA) des carcasses ont été utilisées comme indication de la récupération de la composition des graisses après le sevrage. Le tissu adipeux (%) dans LW était (9.4%) et EW était (7.2%) plus élevé par rapport à MW (P< .05). La surface totale de la papille était plus grande chez les chevreaux LW, par rapport aux chevreaux MW (+ 49 %) et EW (+ 22 %) (P< .05). Globalement, le sevrage des chevreaux à l'âge de 10 semaines a limité l'impact négatif d'un sevrage précoce sur la croissance et le développement du rumen de la race alpine. / The present study aimed to determine the effects of weaning age on growth performance, rumen development and microbiota composition in Alpine goat kids. Seventy-two kids were randomly assigned in pairs male and female to one of three treatments. 1) early weaning, at 6 wk of age (EW), 2) medium weaning, at 8 wk of age (MW) and 3) late weaning, at 10 wk of age (LW). Milk replacer (MR) was offered ad libitum until the step-down wk, when milk was reduced by 12.5% per day for seven days. Two wk after birth, starter ration, hay, and water were offered ad libitum until 12 wk of age where kids were slaughtered. Feed intake was recorded daily, and body weight (BW) was recorded weekly. To evaluate rumen development, blood samples were taken during the whole trial and analyzed for blood β-hydroxybutyrate (BHB) and non-esterified fatty acids (NEFA). Ruminal measurements such as papillae, VFAs and microbiota were taken at wk 12 with only thirty-six males. Rumen contents were obtained for bacteria composition analysis using the V4 region of the 16S rRNA gene and qPCR was used to quantify bacteria, protozoa and fungi. Rumen papillae were obtained for histological analysis in 4 rumen areas: rumen atrium (RA), ventral sac (VS), caudodorsal blind sac (DS), and caudoventral blind sac (VBS). Kids weaned at 10 wk, compared with 8 wk and 6wk had higher average daily gain for the wk postweaning (0.35 vs. 0.24 vs. 0.24 kg / d) and were heavier at wk 12 (27.44 vs. 25.45 vs. 24.07 kg, P< .05). In LW animals, BW was not affected during post weaning period; possibly due to high metabolizable energy (ME) intake caused by the weaning strategy contrary to what was observed in EW and MW animals. Blood levels of BHB increased at weaning time for all treatments but were higher in EW compared to MW (+21%) and LW (+41%) kids (P< .05). Blood levels of NEFAs in EW kids spiked at weaning and were higher than MW (+ 40%) and LW (+101%) in kids (P< .05), suggesting a more pronounced adipose tissue mobilization in early weaned kids at weaning. Microbiota population in postweaning showed that while weaning was delayed, abundance of total bacteria seemed to increase (P< .05) compared with EW animals, whereas protozoa and fungi decreased for LW. Weaning age influences the ruminal microbiota during postweaning. Dual-energy X-ray absorptiometry (DEXA) measurements of carcasses were used as an indication of fat composition recovery in post-weaning. Fat tissue (%) in LW was (9.4%), and EW was (7.2%) higher compared to MW (P< .05). The total papilla surface area was greater in LW, compared to MW (+49%) and EW (+22%) kids (P< .05). Overall weaning kids at 10 wk of age limited the negative impact of earlier weaning on growth and rumen development in the Alpine breed.