The objective of this study was to identify genomic regions and metabolic pathways associated with dry matter intake, average daily gain, feed efficiency and residual feed intake in an experimental Nellore cattle population. The high-density SNP chip (Illumina High-Density Bovine BeadChip, 777k) was used to genotype the animals. The SNP markers effects and their variances were estimated using the single-step genome wide association method. The (co)variance components were estimated by Bayesian inference. The chromosome segments that are responsible for more than 1.0% of additive genetic variance were selected to explore and determine possible quantitative trait loci. The bovine genome Map Viewer was used to identify genes. In total, 51 genomic regions were identified for all analyzed traits. The heritability estimated for feed efficiency was low magnitude (0.13±0.06). For average daily gain, dry matter intake and residual feed intake, heritability was moderate to high (0.43±0.05; 0.47±0.05, 0.18±0.05, respectively). A total of 8, 17, 14 and 12 windows that are responsible for more than 1% of the additive genetic variance for dry matter intake, average daily gain, feed efficiency and residual feed intake, respectively, were identified. Candidate genes GOLIM4, RFX6, CACNG7, CACNG6, CAPN8, CAPN2, AKT2, GPRC6A, and GPR45 were associated with feed efficiency traits. It was expected that the response to selection would be higher for residual feed intake than for feed efficiency. Genomic regions harboring possible QTL for feed efficiency indicator traits were identified. Candidate genes identified are involved in energy use, metabolism protein, ion transport, transmembrane transport, the olfactory system, the immune system, secretion and cellular activity. The identification of these regions and their respective candidate genes should contribute to the formation of a genetic basis in Nellore cattle for feed efficiency indicator traits, and these results would support the selection for these traits.

The objectives of this study were to estimate genetic parameters for indicator traits of feed efficiency and to recommend traits that would result in better responses to selection for increased weaning weight (weaning weight adjusted to 210 d of age [W210]), ADG, and metabolic BW (BW(0.75)) and lower DMI. Records of W210 from 8,004 Nellore animals born between 1978 and 2011 and postweaning performance test records from 678 males and females born between 2004 and 2011 were used. The following feed efficiency traits were evaluated: G:F, partial efficiency of growth (PEG), relative growth rate (RGR), Kleiber's ratio (KR), residual feed intake (RFI), residual weight gain (RWG), and residual intake and gain (RIG). Covariance and variance components were estimated by the restricted maximum likelihood method using multitrait analysis under an animal model. Estimates of genetic gain and correlated responses were obtained considering single-stage and 2-stage selection. Heritability estimates were 0.22 ± 0.03 (W210), 0.60 ± 0.08 (DMI), 0.42 ± 0.08 (ADG), 0.56 ± 0.06 (BW(0.75)), 0.19 ± 0.07 (G:F), 0.25 ± 0.09 (PEG), 0.19 ± 0.07 (RGR), 0.22 ± 0.07 (KR), 0.33 ± 0.10 (RFI), 0.13 ± 0.07 (RWG), and 0.19 ± 0.08 (RIG). The genetic correlations of DMI with W210 (0.64 ± 0.10), ADG (0.87 ± 0.06), and BW(0.75) (0.84 ± 0.05) were high. The only efficiency traits showing favorable responses to selection for lower DMI were G:F, PEG, RFI, and RIG. However, the use of G:F, PEG, or RFI as a selection criterion results in unfavorable correlated responses in some growth traits. The linear combination of RFI and RWG through RIG is the best selection criterion to obtain favorable responses in postweaning growth and feed intake of Nellore cattle in single-stage selection. Genetic gains in feed efficiency are expected even after preselection for W210 and subsequent feed efficiency testing of the preselected animals.

RESUMO -Avaliou-se o efeito de diferentes níveis de fibra em detergente neutro proveniente da forragem (FDNF) na dieta sobre o comportamento ingestivo de cabras em lactação. Cinqüenta cabras da raça Alpina foram distribuídas em um delineamento inteiramente casualizado, com cinco tratamentos e dez repetições, sendo alimentadas à vontade com dietas contendo 20, 27, 34, 41 ou 48% de FDNF. Foi utilizada uma ração completa com feno de tifton-85 (Cynodon sp.) + mistura concentrada constituída de fubá de milho (Zea mays L.), farelo de soja (Glycine max L.) e mistura mineral.As dietas foram fornecidas duas vezes ao dia, às 8h30 e 16h30. O comportamento ingestivo foi determinado mediante observação visual individual dos animais, durante 24 horas, a intervalos de 10 minutos para se determinar o tempo despendido em alimentação, ruminação e ócio. O tempo com alimentação e ruminação e o tempo de mastigação total aumentaram linearmente, enquanto o tempo de ócio diminuiu linearmente com o aumento do nível de FDNF nas dietas.Observaram-se efeitos linear decrescente na eficiência de alimentação e ruminação (g MS/h) e linear crescente no número diário de refeições, conforme amumentaram os níveis de FDNF.Palavras-chave: alimentação, caprinos, fibra, ócio, ruminação Feeding behavior of lactating Alpine goats fed diets containing different dietary levels of forage neutral detergent fiberABSTRACT -The objective of this trial was to study the effects of different dietary levels of forage neutral detergent fiber (FNDF) on feeding behavior of lactating goats. Fifty Alpine goats were randomly assigned to five treatments (ten replicates) in a completely randomized design. Animals had free access to diets containing: 20, 27, 34, 41 or 48% of FNDF.The total mixed ration was constituted of Tifton-85 (Cynodon sp.) hay and concentrate composed of ground corn (Zea mays L.), soybean meal (Glycine max L.), and minerals. Diets were fed twice a day at 8:30 AM and 4:30 PM. Feeding behavior was determined by individual appraisal of animals every 10 minutes during 24 hours to measure eating, ruminating, and resting times. Eating, ruminating, and total chewing times increased linearly whereas the opposite was observed for resting time when FNDF levels ranged from 20 to 48% of the diet. Linear decreases on feeding and rumination efficiencies both expressed as g DM/h, and a linear increase in the number of daily meals were observed with the increment of dietary FNDF.Key Words: feed intake, goats, fiber, resting time, rumination IntroduçãoPara que ocorra alta produção de leite durante a lactação, é necessária a maximização do consumo de alimento. Todavia, os animais leiteiros normalmente não consomem quantidades de energia suficientes para atender seu requerimento, pois, nesse período, a capacidade do rúmen-retículo pode limitar fisicamente o consumo.Entretanto, quando a produção de leite aumenta, é essencial a redução no efeito de enchimento das dietas para se maximizar o consumo de energia e evitar a excessiva mobilização de reservas corporais, o que...

Fifty-nine Nellore bulls from low and high residual feed intake (RFI) levels were studied with the objective of evaluating meat quality traits. Animals were slaughtered when ultrasound-measured backfat thickness reached 4mm, and samples of Longissimus were collected. A mixed model including RFI as fixed effect and herd and diet as random effects was used, and least square means were compared by t-test. More efficient animals consumed 0.730 kg dry matter/day less than less efficient animals, with similar performance. No significant differences in carcass weight, prime meat cuts proportion, chemical composition, pH, sarcomere length, or color were observed between RFI groups. Shear force, myofibrillar fragmentation index and soluble collagen content were influenced by RFI, with a higher shear force and soluble collagen content and a lower fragmentation index in low RFI animals. Feedlot-finished low RFI young Nellore bulls more efficiently convert feed into meat, presenting carcasses within quality standards.

RESUMO -O efeito de diferentes formas de suplementação lipídica sobre o consumo, a digestibilidade, o balanço de compostos nitrogenados, a produção de leite e a eficiência de utilização de nutrientes em cabras lactantes foi testado com a inclusão de óleo de soja (OS), sais de cálcio de ácidos graxos de cadeia longa (SC) e grão de soja (GS) na dieta. Foram utilizadas 24 cabras lactantes, alocadas em delineamento inteiramente casualizado, com quatro tratamentos e seis repetições. Os tratamentos consistiram de uma dieta controle (C), com 2,2% de EE e isenta de lipídio suplementar, e de três outras dietas, adicionadas de um dos suplementos testados, contribuindo com 4,5% de EE suplementar. O consumo voluntário e a produção de leite foram monitorados diariamente no período de 51 a 138 dias de lactação. Effects of fat supplements on intake and efficiency of nutrient utilization in lactating dairy goats ABSTRACT -The effect of different fat supplements on intake, digestibility, nitrogen balance, milk yield and efficiency of nutrient utilization was evaluated in lactating dairy goats. Twenty-four dairy goats were assigned to a completely randomized design with four treatments and six replicates/treatment. The fat supplements tested were soybean oil (SO), calcium salts of longchain fatty acids (CS) and whole soybean (WS), which contributed with 4.5% of dietary ether extract. A control diet with no added fat was also fed to the animals. Daily measurements of intake and milk yield were done from day 51 to day 138 of lactation.Intakes of DM (DMI), NDF (NDFI), TDN (TDNI), and net energy (NEI) were lower on soybean oil and whole soybean than on control and CS diets. Feeding fat supplements to lactating goats reduced digestibilities of OM, CP and TC. Digestibility of NDF was reduced by SO while that of NFC was reduced by WS. Yields of milk fat, milk protein and milk decreased when WS was fed and the feeding of all three fat supplements depressed the yield of milk lactose. No significant differences in the concentration of milk components were observed across treatments. Similarly, the net efficiency of utilization of ingested metabolizable energy for milk production (kl) did not differ among diets. The same was true for nitrogen balance and retained nitrogen.Key Words: calcium salts of fatty acids, goats, milk, oil, production, soybean IntroduçãoA produção de leite é um processo metabólico altamente dependente de energia. No início da lactação, ocorrem simultaneamente redução da capacidade de ingestão de MS e elevação das exigências energéticas, em razão da maior produção. Assim, os animais, por meio da homeorresia (Bauman, 2000), mobilizam suas reservas corporais para atender esta condição fisiológica.