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.

Nutrient intake and milk yield and composition of Alpine lactating goats fed diets with different fiber levelsABSTRACT -Fifty Alpine lactating does were used to evaluate the effects of feeding different levels of forage neutral detergent fiber (FNDF) on nutrient intake and milk yield and composition. Animals were housed individually and assigned to a completely randomized design with five treatments and ten replicates. A total mixed ration, containing Tifton-85 (Cynodon sp.)hay, ground corn, soybean meal and mineral mixture was fed ad libitum. The experimental diets contained 20, 27, 34, 41 or 48% of FNDF. As dietary FNDF increased, the intakes of DM, OM, CP, EE, TC, NSC and net energy (NE) decreased linearly.In addition, increasing dietary FNDF linearly increased intakes of NDF, FNDF and ADF. There was no effect of FNDF level on contents of milk fat and milk total solids. However, milk yield, fat-corrected milk and yield of total solids all decreased linearly. The efficiency of utilization of metabolizable energy to milk yield reached a plateau at 35.4% of FNDF.Key Words: feeding, fiber, forage, goats IntroduçãoO consumo voluntário pode ser definido como a quantidade máxima de MS ingerida por um animal ou grupo de animais durante determinado período no qual há livre acesso ao alimento (Forbes, 1995). Em um sistema de produção, o consumo de alimento é de grande importância, visto que a ingestão de MS determina o fornecimento de nutrientes necessários para atender os requerimentos de mantença e produção dos animais.Segundo Rodrigues (1998), o consumo de nutrientes é o principal fator a limitar a produção de ruminantes. Portanto, maximizar o consumo de um animal é fundamental no desenvolvimento de rações e estratégias de alimentação que otimizarão a rentabilidade da produção.Mertens (1994) afirma que a ingestão de MS é controlada por fatores físicos, fisiológicos e psicogênicos. O fator físico refere-se à distensão física do rúmen-retículo, o fisiológico é regulado pelo balanço energético ou nutricional e a regulação psicogênica envolve o comportamento animal em resposta a fatores inibidores ou estimuladores no alimento ou ao manejo alimentar, que não são relacionados ao valor energético do alimento ou ao efeito de repleção.Entre os fatores envolvidos na regulação do consumo, a concentração de FDN na dieta de ruminantes tem sido considerada, por sua lenta degradação e por apresentar

Understanding the reasons why animals of similar performances have different feed requirements is important to increase profits for cattle producers and to decrease the environmental footprint of beef cattle production. This study was carried out aiming to identify the associations between residual feed intake (RFI) and animal performance, nutrient digestibility, and blood metabolites related to energy balance of young Nellore bulls during the finishing period. Animals previously classified as low (n = 13) and high RFI (n = 12), with average initial body weight of 398 kg and age of 503 days were used. Cattle were fed a high energy diet and were slaughtered when rib fat thickness measured by ultrasound between the 12th and 13th ribs reached the minimum of 4 mm. A completely randomized design was adopted, being data analyzed with a mixed model that included the random effect of slaughter group, the fixed effect of RFI class, and linear effect of the covariate feedlot time. No differences were found (p > 0.10) between RFI classes for performance, dry matter, and nutrients intake. However, dry (p = 0.0911) and organic matter (p = 0.0876) digestibility tended to be lower, and digestibility of neutral detergent fiber corrected for ash and protein (p = 0.0017), and total digestible nutrients (p = 0.0657) were lower for high RFI animals, indicating lesser capacity of food utilization. Difference between low and high RFI animals was also found for blood cortisol at the end of the trial (p = 0.0044), having low RFI animals lower cortisol concentrations. Differences in the ability to digest food can affect the efficiency of transforming feed into meat by Nellore cattle.

This study was conducted to evaluate associations of performance traits, feed efficiency, and blood variables with residual feed intake (RFI) in growing Nellore cattle. A total of 118 growing Nellore animals, 62 males and 56 females, were used. A diet containing 2 Mcal/kg was offered ad libitum and individual DMI was measured over a period of 84 d. Animals were classified as low (≤0.128 kg/d; = 40), medium (-0.128 to 0.135 kg/d; = 42), or high RFI (>0.135 kg/d; = 36). Blood samples were collected at the beginning and at the end of the test for determination of plasma concentrations of different blood variables. Data were analyzed using a mixed model that included the random effect of facility the fixed effects of sex, RFI class, and linear effect of the covariate age within sex; and the interaction between RFI class and sex. Least squares means were compared using a -test. Animals of different RFI classes presented similar performance traits and different DMI. Low-RFI animals consumed, on average, 0.670 kg/d less DM than high-RFI animals. Among the blood variables analyzed, significant differences among RFI classes were observed for urea, IGF-1, and insulin. Plasma urea concentrations were lower (5.58 vs. 5.91 mmol/L) and insulin (4.45 vs. 3.70 μIU/mL) and IGF-1 (433 vs. 399 ng/mL) concentrations were higher in low-RFI animals when compared to high-RFI animals. Plasma concentrations of urea, IGF-1, and insulin can be used as indicators of feed utilization efficiency in Nellore cattle.