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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Os objetivos deste estudo foram: 1) classificar os animais em grupos de alta e baixa eficiência utilizando dois índices de eficiência alimentar (consumo alimentar residual (CAR) e consumo e ganho de peso residual (CGR), e 2) avaliar se bezerras durante a fase de aleitamento, divergentes para índices de eficiência alimentar, apresentam diferenças em desempenho, medidas corporais, parâmetros sanguíneos e ruminais, digestibilidade, partição de energia, partição de nitrogênio e termografia. Trinta e duas bezerras Gir foram utilizadas no experimento com 63 dias de duração e classificadas em dois grupos de eficiência alimentar (EA) baseados no CAR e CGR (média ± 0,5 DP). Os grupos foram classificados como CAR de alta eficiência (AE) (AE CAR, n = 9; AE CGR, n = 10) e CAR de baixa eficiência (BE) (BE CAR, n = 10; BE CGR, n = 11). As bezerras de AE e BE apresentaram valores de CAR de - 0,052 e 0,049 kg / d (P < 0,05), respectivamente). Ao nascimento, a quantidade de leite integral fornecida para cada animal foi calculada com base no seu peso metabólico ao nascimento (42% x PV0,75). A dieta líquida foi dividida em duas refeições às 07:00 e 14:00 horas. A dieta sólida total (DS) foi composta de 92% de concentrado e 8% de feno de tifton 85 picado em 5 cm de comprimento. A ingestão foi medida diariamente. O peso corporal e as medidas foram realizadas no nascimento, terceiro e sétimo dia e semanalmente em diante. As concentrações sanguíneas de insulina, BHB, ureia e glicose, além de pH, N-NH3 e ácidos graxos voláteis (AGV) no líquido ruminal foram avaliadas aos 14, 28, 42, 56 e 70 dias de idade, respectivamente. Do 50º ao 55º dia de idade, os animais foram submetidos a um ensaio de digestibilidade. Aos 55 (± 6) dias de idade, as trocas respiratórias foram mensuradas por uma câmara respirométrica de circuito aberto. As imagens térmicas dos bezerros foram realizadas com uma câmera de infravermelho em d 56 (± 3) às 06:00 h, antes da alimentação. O grupo AE CAR consumiu 8,9% menos dieta sólida do que o grupo BE CAR. Os animais AE CAR exibiram maior digestibilidade da proteína bruta e de extrato etéreo e tenderam a ter maior digestibilidade total da matéria seca e orgânica. Os animais do BE CAR apresentaram maior consumo de energia bruta e nitrogênio, porém, maiores perdas fecais tenderam a reduzir a eficiência no uso de energia e nitrogênio nesse grupo. A concentração total de AGV (µmol/mL), a proporção de acetato e propionato (% AGV) no fluido ruminal foram maiores para o grupo de BE em comparação ao grupo de AE. A concentração de ureia no sangue tendeu a ser maior em BE que em AE. As bezerras de AE e BE apresentaram valores de CGR de 0,080 e -0,077kg / d (P ≤ 0,01), respectivamente. Os animais de AE para CGR exibiram maior ganho médio diário (9,4%), peso corporal e circunferência torácica, embora o grupo de AE para CGR tivessem um quadril mais estreito. Os animais de AE para CGR tenderam a ter maior digestibilidade de extrato etéreo, mas maiores perdas de metano (% da energia bruta). Os animais AE CGR tenderam a ter maior proporção ruminal de acetato e menor propionato (% AGV). A concentração de insulina no sangue foi maior e a glicose sanguínea tendeu a ser maior para os animais BE que para os animais AE CGR. O grupo de BE CGR apresentou maiores temperaturas de costela e flanco esquerdo e superfície do ânus medida por termografia infravermelha em comparação ao grupo AE CGR. Maior eficiência em grupos de AE para CAR durante a fase de aleitamento parece estar relacionado a diferenças na digestibilidade, mas não a diferenças na fermentação ruminal. Diferenças no metabolismo de proteína parece afetar diferenças em CAR durante esta fase. Animais divergentes para CGR durante a fase avaliada parecem diferir em medidas corporais e no metabolismo de glicose e insulina, o que pode estar relacionado a diferenças na composição do ganho. A termografia infravermelha parece estar correlacionada ao CGR, mas não à produção de calor (PC) em bezerras durante a fase de aleitamento. The objectives of this study were: 1) to classify animals into groups of high and low feed efficiency using two feed efficiency indexes (residual feed intake (RFI) and residual feed intake and body weight gain (RIG)), and 2) to evaluate if pre-weaning heifer calves divergent for feed efficiency indexes exhibit differences in performance, body measurements, blood and ruminal parameters, digestibility, energy partitioning, nitrogen partitioning and thermography. 32 Gyr heifer calves were enrolled in a 63-d trial and classified into 2 feed efficiency (FE) groups based on RFI and RIG (mean ± 0.5 SD). The groups were classified as high efficiency (HE) RFI (HE RFI, n = 9; HE RIG, n = 10), and low efficiency (LE) RFI (LE RFI, n = 10; LE RIG, n = 11). HE and LE calves had RFI values of - 0.052 and 0.049 kg/d (P < 0.05), respectively). At birth, the amount of whole milk provided for each animal was calculated based on their metabolic weight at birth (42% x BW0.75). The liquid diet was divided into two meals at 0700 and 1400. The total solid diet (TSD) was composed of 92% concentrate and 8% of tifton 85 hay chopped in 5 cm length as-fed. Intake was measured daily. Body weight and measurements were performed at birth, 3rd and 7th day and weekly onward. Blood concentrations of insulin, BHB, urea and glucose, and pH, N-NH3 and volatile fatty acids (VFA) in ruminal fluid were evaluated at 14, 28, 42, 56 and 70 days of age, respectively. From the 50th to the 55th day of age the animals were submitted to a digestibility assay. At 55th (±6) days of age, respiratory exchanges were measured by one open-circuit respirometry chamber. Thermal images of the calves were taken with an infrared camera on d 56 (±3) at 0600 h, before the morning feeding. The HE RFI group consumed 8.9% less solid diet than the LE RFI group. HE RFI animals exhibited an increased digestibility of crude protein and ether extract and tended to have higher total dry and organic matter digestibility. LE RFI animals had higher gross energy and nitrogen intake, though higher fecal losses resulted in a tendency to reduce energy and nitrogen use efficiency. Total VFA concentration (µmol/mL), proportion of acetate and propionate (%VFA) in ruminal fluid were greater for LE than HE RFI heifers. Blood urea concentration tended to be higher in LE than HE RFI heifers. HE and LE calves had RIG values of 0.080 and -0.077kg/d (P ≤ 0.01), respectively. HE RIG animals exhibited higher average daily gain (9.4%), body weight (BW), and heart girth, though HE RIG group exhibited narrower hip width. HE RIG animals tended to have higher ether extract digestibility but higher methane losses (% of gross energy). HE RIG animals tended to have greater ruminal proportion of acetate and lower propionate (%VFA). Blood insulin concentration was greater and blood glucose tended to be greater for LE than HE RIG animals. LE RIG had higher left rib, left flank and anus surface temperature measured by infrared thermography in comparison to HE RIG group. HE RFI in pre-weaning heifers seems to be related to differences in digestibility and not related to differences in ruminal fermentation. Differences in protein metabolism seems to affect RFI during this phase. Divergent animals for RIG during the assessed phase appear to differ in body measurements, and glucose and insulin metabolism, which may be related to differences in the composition of the gain. Infrared thermography seems to be correlated to RIG but not to heat production (HP) in pre-weaning calves.

The objectives of this study were: 1) to classify animals into groups of high and low feed efficiency using two feed efficiency indexes (Residual feed intake (RFI) and residual feed intake and body weight gain (RIG)), and 2) to evaluate if pre-weaning heifer calves divergent for feed efficiency indexes exhibit differences in performance, body measurements, digestibility, energy partitioning, and nitrogen partitioning. A total of 32 Gyr heifer calves were enrolled in a 63-d trial and classified into two feed efficiency (FE) groups based on RFI and RIG (mean ± 0.5 SD). The groups were classified as high efficiency (HE) RFI (HE RFI, n = 9; HE RIG, n = 10), and low efficiency (LE) RFI (LE RFI, n = 10; LE RIG, n = 11). The remaining animals were classified as intermediate (n = 13 (RFI) and n = 11 (RIG)). HE and LE calves had RFI values of?0.052 and 0.049 kg/d (P < 0.05), respectively. The HE RFI group consumed 8.9% less solid diet than the LE RFI group. HE RFI animals exhibited an increased digestibility of crude protein and ether extract and tended to have greater total dry and organic matter digestibility. LE RFI animals had greater gross energy and nitrogen intake, though greater fecal losses resulted in a tendency to reduce energy and nitrogen use efficiency. HE and LE calves had RIG values of 0.080 and -0.077kg/d (P ? 0.01), respectively. HE RIG animals exhibited greater average daily gain (9.4%), body weight (BW), and heart girth, though HE RIG group exhibited narrower hip width. HE RIG animals tended to have greater ether extract digestibility but greater methane losses (% of gross energy). HE RFI in pre-weaning heifers seems to be related to differences in digestibility. Divergent animals for RIG during the assessed phase appear to differ in body measurements, which may be related to differences in the composition of the gain. Made available in DSpace on 2020-01-13T18:15:49Z (GMT). No. of bitstreams: 1 ArtigoPlosOneSamariniRelationship.pdf: 1512277 bytes, checksum: 1a93b88921d623ad143f3b5f3c06ef7d (MD5) Previous issue date: 2019