Caracterização do consumo alimentar residual e relações com desempenho e características de carcaça de bovinos nelore

Objetivou-se com este trabalho avaliar desempenho, parâmetros de eficiência e correlações fenotípicas entre diferentes medidas de eficiência energética de animais Nelore selecionados para peso pós desmame e classificados quanto ao consumo alimentar residual (CAR). O CAR foi calculado pela diferença entre o consumo observado e o predito, baseado no PV0,75 e ganho médio diário (GMD), sendo os animais classificados como alto CAR (> 0,5 desvio padrão da média - menos eficientes), médio CAR (± 0,5 desvio padrão da média), e baixo CAR ( 0.5 standard deviation - less efficient), medium RFI ( ± 0.5 standard deviation), and low RFI (<0.5 standard deviation - more efficient). There were no differences in initial and final BW, ADG and dry matter intake (DMI) between RFI levels. Low RFI animals also were better in feed efficiency, feed conversion and partial efficiency of growth and were not different of relative growth rate and Kleiber ratio. RFI was correlated with feed efficiency (-0.25), feed conversion (0.25), partial efficiency of growth (-0.37) and DMI (0.16), and was not significantly correlated with BW (0.04 ), ADG (-0.02), relative growth rate (-0.03) and Kleiber ratio (-0.05). Significant correlations between feed conversion and initial BW (0.34) and ADG (-0.46) were detected. Partial efficiency of growth was correlated to all the others efficiency parameters analyzed. RFI, when compared to other energy efficiency measures, has great potential in productive efficiency, without affecting growth and size of animals.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Feed efficiency of Nellore cattle selected for postweaning weight

Foram comparados dois rebanhos Nelore, um selecionado para maior peso pós-desmame e outro controle, selecionado para a média de peso pós-desmame, para avaliar os efeitos de 29 anos de seleção sobre a eficiência alimentar. Sessenta machos Nelore com 205 kg e 267 dias de idade (41 selecionados e 19 controle), foram avaliados em baias individuais durante a prova de ganho de peso. O desempenho e o consumo de matéria seca foram utilizados para determinar as seguintes medidas de eficiência: conversão alimentar; consumo alimentar residual; ganho residual; eficiência parcial de crescimento; taxa de crescimento relativo; e taxa de Kleiber. Após o período experimental de 112 dias, os animais controle apresentaram menor peso vivo final em comparação aos selecionados, contudo, não diferiram quanto ao consumo de matéria seca (% do peso vivo), à área de olho-de-lombo e às espessuras de gordura subcutânea na altura da 12ª costela e na região da picanha. O consumo de matéria seca (kg/dia) e o ganho médio diário dos animais selecionados foram, respectivamente, 19,4 e 26,4% superiores aos dos controle. O maior ganho médio diário dos animais selecionados promoveu melhora significativa, em torno de 6%, na conversão alimentar; 70 g/dia no ganho residual; e de 17% na taxa de Kleiber. As demais medidas de eficiência (consumo alimentar residual, eficiência parcial de crescimento e taxa de crescimento relativo) não diferiram entre os rebanhos. Os 29 anos de seleção para peso pós-desmame não afetaram a eficiência alimentar de bovinos Nelore.Two Nellore herds were compared, one selected for greater postweaning weight and the other, control, selected for average postweaning weight, to evaluate the effects of 29 years of selection on feed efficiency. Sixty Nellore males (41 selected and 19 control) averaging 205 kg and 267 days of age were evaluated in individual pens during performance test. Performance and dry matter intake were used to determine the following feed efficiency traits: feed conversion; residual feed intake; residual gain; partial growth efficiency; relative growth rate and Kleiber ratio. After the 112-day experimental period, control animals showed lower body weight when compared to selected animals, however, they did not differ for dry matter intake (% of body weight), rib-eye area and fat thickness at the 12th rib subcutaneous region and on the rump region. Dry matter intake (kg/day) and average daily weight gain from selected animals were, respectively, 19.4% and 26.4% higher than the control ones. The highest average daily weight gain by selected animals promoted significant improvement, around 6%, on feed conversion; 70 g/day on residual gain; and 17% on Kleiber rate. The other feed efficiency traits (residual feed intake, partial growth efficiency and relative growth rate) did not differ between herds. The 29-year selection for post-weaning weight did not affect feed efficiency of Nellore cattle

Animal performance, feeding behaviour and carcass traits of feedlot cattle diet fed with agro-industrial by-product as fat source

In feedlot system is particularly important to reduce the cattle feeding cost without impact on the animal gain and carcass, in this sense, aimed with this study to evaluate animal performance and carcass traits of the young Nellore male (n = 40) finished with agro-industrial by-products in feedlot diet. The addition of cottonseed by-product (CSB) was based on the ether extract (EE) contents in the feedlot diet: 3, 4 and 5%; and two other reference treatments were also tested, with 3 and 5% of EE content and soybean by-product (SOB) as fat source, totalling five experimental diets. In diets with 3% EE, CSB did not alter performance, gain cost or carcass traits compared to the SOB. In diets with 5% EE, animals fed with CSB showed greater dry matter (DM) intake than animals fed with SOB (10.34 versus 8.94 kg/day), but because CSB is a cheaper ingredient than SOB, it reduced the gain cost from 1.60 to 1.35 US$/kg. The CBS used in diet with 3, 4 and 5% EE increased the daily gain (1.17, 1.38 and 1.50 kg/day) and the rumination time (225, 338 and 370 min/day, respectively). So, CSB does not change the carcass traits nor the feeding behaviour when compared to SOB. The increased of CSB concentration in the diet raised the daily gain, DM intake and rumination time, with no changes in carcass traits.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP