R. N. B. Lobo

Genetic parameters for reproductive traits of zebu cows in the semi-arid region of Brazil

Abstract Genetic parameters for age at first calving (AFC) and calving interval (CI) for zebu cows grazed on semi-arid pasture in Ceara State, Brazil, were estimated by Restricted Maximum Likelihood (REML). The animal model utilized included the fixed effects: year of birth of cow, herd, month and year of calving with respect to AFC, and additionally, month and year of calving preceding CI. Means were 59.0 months and 577.4 days for AFC and CI, respectively. Heritability estimates for AFC and CI were 0.29±0.09 and 0.14±0.01, respectively. Repeatability estimate for CI was 0.15±0.01. Genetic and phenotypic correlations between traits were 0.10 and 0.43, respectively.

Breeding program evaluation for dual purpose zebu cattle

A deterministic approach was used to predict genetic gain and net present value for a breeding program in a dual-purpose zebu cattle population. The considered criterias were body weights, dairy and reproductive traits. High genetic gains and profit were obtained. More than 70% of genetic profit was net present value, justifying selection costs. The small proportion of recorded animals in relationship to the beneficial population of the improvement and the high economic values of traits could explain this profit.

Evaluation of alternative breeding programs for dual purpose Zebu cattle

Utilizando-se simulacao deterministica, foram avaliados seis esquemas de melhoramento, com diferentes grupos de informacoes: (1) somente caracteristicas de crescimento, (2) somente caracteristicas leiteiras, (3) caracteristicas de crescimento e reprodutivas, (4) caracteristicas leiteiras e reprodutivas, (5) caracteristicas de crescimento e leiteiras e (6) caracteristicas de crescimento, leiteiras e reprodutivas. Avaliaram-se tambem a resposta a variacao no uso de touros provados por meio do teste de progenie, a resposta sem a realizacao do teste de progenie no estrato de vacas de corte da populacao e a resposta a variacao no valor economico do peso ao abate. Em todos os esquemas avaliados, foram verificados altos ganhos geneticos e lucros decorrentes do programa. Os esquemas que consideraram as caracteristicas leiteiras foram mais eficientes pela selecao para maior producao de leite e menor peso de vaca adulta. As caracteristicas de fertilidade foram mais importantes para os esquemas de corte. A resposta economica a selecao foi maior com o aumento no uso de touros provados, embora nao proporcionalmente. A contribuicao das caracteristicas de corte para o lucro genetico somente superou a das leiteiras quando o valor economico do peso ao abate superou em 14 vezes o da producao de leite. Foi demonstrado nao haver necessidade da realizacao do teste de progenie com as vacas de corte para o sistema de dupla aptidao estudado.

Do carcasses of lambs finished on commercial production systems meet market standards

This study aimed to characterize a commercial lamb finishing system using animals of undefined breed from production to slaughter by analyzing performance, carcass traits, yield of commercial cuts, and the quality and meat acceptance of different slaughter groups, as to evaluate whether this system provides the market with a standardized product. The lots were not homogeneous for yield of commercial cuts and performance and morphometric traits evaluated in vivo. The groups were heterogeneous to 75% of the 13 carcass traits evaluated, among them, hot and cold carcass weights, hot and cold carcass yields, carcass grade finishing and biological yield. There was also no uniformity for the proportion of non-carcass components, morphometry of carcass, visual appraisals, and loin traits. On the other hand, homogeneity was achieved in physico-chemical and sensory traits, except for hardness and proportion of saturated, monounsaturated and polyunsaturated fatty acids. We conclude that the commercial finishing system with the use of undefined crossbred lambs does not produce carcass and cuts standardized to the market.

Genetic parameters for rank of the Santa Inês sheep in agricultural fairs using Bayesian procedures

Abstract The aim of this study was to estimate the genetic parameters for the ability of a sheep to rank among the top three in its age category (ABI3) and for its total score (TS) on the judgement championships held in different agricultural fairs in Brazil. Data files included 3180 records referring to 1896 animals for ABI3 and 4383 records referring to 2170 animals for TS. The relationship matrix was composed by 4069 animals. Variance components were estimated fitting threshold and linear animal models for ABI3 and TS, respectively, by Bayesian analysis using the Gibbs sampler. The posterior means of the heritability and repeatability were, respectively, 0.10 ± 0.07 and 0.57 ± 0.11 for ABI3 and 0.12 ± 0.04 and 0.31 ± 0.02 for TS. The low values for the heritabilities related to these traits reveal a strong influence of the environmental factors, as the differential management offered to the animals before and during the fair. The repeatability values for ABI3 suggest high correlation among the animal classifications in different fairs. However, for TS, the observed performance has moderate confidence to be repeated over time. We conclude that although reduced, there is genetic variability for the animal’s performance in agricultural fairs. Nevertheless, due to the low heritability estimates, the expected response to direct selection for ABI3 and TS will be low.