Alternative for Intensification of Beef Production under Grazing

One of the challenges to overcome in order to assure the position occupied by Brazil as one of the most important players in the world beef market is to design sustainable technological alternatives, which will maintain a constant uniform beef supply all year round. This crucial problem could be solved by using more intensively, the alternatives available for pastures management and feed supplement-ation. However, the potential results created by these strategies might be better explored by using the right choice of animals as far as genetic group and weaning weight is concerned. Thus, in order to fulfill this goal it was designed an experiment was designed to evaluate combinations of pastures species (Brachiaria and Panicum), pasture management (feed supplementation and rotational grazing) and animal genetic groups

Peso ao nascer de bezerros Nelore: heritabilidade e interação sexo x reprodutor

Experimental data were obtained from the herd book of Campo Experimental de Terenos, and it refers to birth weight of 861 calves born during 1965 through 1977. The heritability was estimated by four models; the first model was the complete one; in the second model the effects that showed no significant influence on birth weight were drawn; the third model was used to analyze males and females separately and included the same variables as the complete model; the fourth model included the variables used in the second model. Year, sex and dam previous condition (cow that calved or not in the previous year and first calf heifers) affected birth weight (P<.01). The approximate mean weights of the males and females were 25.04 and 23.40 kg, respectively, for the different models. Cows that failed to conceive in the previous year produced calves, approximately, .70 kg heavier, at birth, than calves from heifers and from cows that calved in the previous year. Birth season, and cow's age did not affect birth weight. The heritability estimates of birth weight for the different models were as follows: .73 ± .15 for the first model; .70 ± 15 for the second one; .90 ± .20 and .90 ± .21, for males and females, respectively, on the third model; and .82 ± .20 and .81 ± .20, for males and females, respectively, on the fourth one. We can conclude, by these results, that sex does not affect sire evaluation for birth weight.Utilizaram-se dados obtidos dos livros de registro zootécnico do Campo Experimental de Terenos, antiga sede do Instituto de Pesquisa Agropecuária do Oeste (IPEAO), referentes a peso ao nascimento de 861 bezerros Nelore nascidos de 1965 a 1977. A heritabilidade foi estimada utilizando-se quatro modelos estatísticos: o primeiro modelo foi o completo; no segundo modelo foram retirados os efeitos que não mostraram significância sobre peso ao nascimento; o terceiro modelo foi utilizado para analisar machos e fêmeas separadamente, e incluiu as mesmas variáveis do modelo completo; o quarto modelo também foi usado para analisar machos e fêmeas separadamente, mas incluiu as variáveis usadas no segundo modelo. Ano, sexo e condição anterior da fêmea (que tenha parido ou não no ano anterior e novilha de primeira cria) influenciaram altamente o peso ao nascer (P<0,01). Os pesos médios aproximados de machos e fêmeas foram, respectivamente, 25,04 e 23,40 kg para os diferentes modelos. Vacas falhadas produziram bezerros aproximadamente 0,70 kg mais pesados ao nascimento, do que bezerros de novilhas e vacas que pariram no ano anterior. Estação de nascimento e idade da vaca não tiveram influência sobre o peso ao nascimento. As estimativas de heritabilidade do peso ao nascimento para os diferentes modelos foram as seguintes: 0,73 ± 0,15 para o modelo 1; 0,70 ± 0,15 para o modelo 2; 0,90 ± 0,20 e 0,90 ± 0,21 para machos e fêmeas, respectivamente, no modelo 3 e 0,82 ± 0,20 e 0,81 ± 0,20 para machos e fêmeas, respectivamente, no modelo 4. Pela pequena importância da interação sexo x reprodutor dentro de ano e, pela semelhança das estimativas de heritabilidade nos dois sexos, conclui-se que o sexo da progênie não influência na avaliação de reprodutores para peso ao nascimento de suas crias

Biological and economic efficiencies of steers in finishing period fed with supplementary diet in a palisade grass pasture

O objetivo deste trabalho foi avaliar as eficiências biológica e econômica de novilhos em terminação, em pastagem, que receberam suplementação durante o período seco. Trinta novilhos ½ Braford ¼ Angus ¼ Nelore, separados em dois lotes com pesos corporais mÚdios (PC) de 365 e 410ákg, foram distribuÝdos em seis piquetes de capim-marandu, em delineamento experimental inteiramente casualizado, com trÛs tratamentos e dez repetiþ§es. Osátratamentos foram constituÝdos pelos suplementos: sal-amireia; 0,6 e 1% do PC de concentrado. Aácada 28 dias, os animais foram pesados, e a cobertura de gordura foi avaliada. Mensalmente, todos os piquetes foram amostrados para determinaþÒo da massa de forragem dos componentes morfol¾gicos e do valor nutritivo. Osáanimais com suplementaþÒo de 1% do PC de concentrado ganharam mais peso do que aqueles com 0,6% do PC, e estes ·ltimos mais do que aqueles que receberam sal-amireia. Consequentemente, houve relaþÒo inversa entre a dose de suplementaþÒo e o tempo necessßrio para os animais atingirem o ponto de acabamento. Independentemente do tratamento, os animais mais leves apresentaram margens lÝquidas superiores. Para os dois lotes, a maior margem lÝquida esteve associada Ó suplementaþÒo apenas com sal-amireia.The objective of this work was to evaluate the biological and economic efficiencies of steers, in finishing period in a palisade grass pasture, with supplementation during the dry season. Thirty steers ½ Braford ¼ Angus ¼ Nelore separated in two groups with initial live weights (LW) of 365 kg and 410 kg were assigned to six paddocks of palisade grass. The experimental design was completely randomized, with three treatments and ten replicates. The treatments consisted of the following supplements: mineral salt plus starea; 0,6 and 1% LW of concentrate. Animals were weighted each 28 days, and their fat thickness was determined. Forage was sampled monthly to determine its mass, morphological components and nutritive value. Animals supplemented with 1% of the LW gained more weight than those supplemented with 0,6% of the LW, and these last gained more weight than those supplemented with mineral salt plus starea. Consequently, there was an inverse relationship between supplementation and time for reaching the predefined end-point. Independently of treatment, the lighter steers showed higher net margins. For the two groups of animals, the largest net margin was associated with the mineral salt plus starea supplementation only

Estimates of genetic parameters and evaluation of genotype x environment interaction for weaning weight in Nellore cattle

Records of 105,645 Nellore calves born from 1977 to 1994 in eight different regions of Brazil were used to estimate genetic and environmental parameters and evaluate genotype x environmental interaction for weaning weight (kg). Estimates were obtained using MTDFREML with a sire model. Mathematical model included random effects of sire and dam, and fixed effects of sex, month and year of birth, herd, and age of dam at calving. Estimates of phenotypic variances were 375, 431, 431, 407, 409, 400, 413, and 336 for the eight different regions and 420 over all regions. Estimates of heritability were, respectively, 0.22, 0.26, 0.16, 0.29, 0.34, 0.38, 0.37, 0.26, and 0.26. Heritability estimates for weaning weights from two trait analyses with measurements in different regions considered as different traits varied from 0.17 to 0.38 and estimated genetic correlations among weaning weights in different regions varied from - 0.03 to 1.00. Spearman rank correlations between EPDs for weaning weight from different regions were calculated to verify whether sires ranked differently in different regions. The correlations ranged from - 0.25 to 1.00 between pairs of regions. Estimates of heritability suggest that mass selection could result in genetic gain under a breeding program that utilizes weaning weight as a selection criterion. The apparent importance of genotype x environment interaction detected by this study suggests a need to choose sires appropriate for the region where they will be used, since relative performance of progeny of a sire appears to change from one region to another