Sustainable Intensification of Beef Production in the Tropics: The Role of Genetically Improving Sexual Precocity of Heifers

Abstract

Increasing productivity through continued animal genetic improvement is a crucial part of implementing sustainable livestock intensification programs. In Zebu cattle, the lack of sexual precocity is one of the main obstacles to improving beef production efficiency. Puberty-related traits are complex, but large-scale data sets from different “omics” have provided information on specific genes and biological processes with major effects on the expression of such traits, which can greatly increase animal genetic evaluation. In addition, genetic parameter estimates and genomic predictions involving sexual precocity indicator traits and productive, reproductive, and feed-efficiency related traits highlighted the feasibility and importance of direct selection for anticipating heifer reproductive life. Indeed, the case study of selection for sexual precocity in Nellore breeding programs presented here show that, in 12 years of selection for female early precocity and improved management practices, the phenotypic means of age at first calving showed a strong decreasing trend, changing from nearly 34 to less than 28 months, with a genetic trend of almost −2 days/year. In this period, the percentage of early pregnancy in the herds changed from around 10% to more than 60%, showing that the genetic improvement of heifer’s sexual precocity allows optimizing the productive cycle by reducing the number of unproductive animals in the herd. It has a direct impact on sustainability by better use of resources. Genomic selection breeding programs accounting for genotype by environment interaction represent promising tools for accelerating genetic progress for sexual precocity in tropical beef cattle.

Effect of Creep Feeding Supplementation on Growth Performance and Metabolic Characteristics of Nellore Heifers

“…In general, puberty traits-particularly the age and weight at first corpus luteum-respond to selection in tropical beef cattle [20]. Genetic characteristics in Zebu cattle that are associated with heifers' puberty and production traits include fat depth, rib fat, body condition, live weight, and Longissimus dorsi muscle area [21]. However, the relationship of growth and fatness with puberty traits is not expected to be linear, which is in agreement with our results that showed that, as measured by progesterone concentration, puberty traits were not achieved naturally at the end of the growing phase.…”

Efeito da idade a primeira concepção como critério de seleção em características de crescimento e carcaça em bovinos Nelore

“…A lucratividade da bovinocultura de corte está associada à redução da idade a maturidade das novilhas, uma vez que permite maior número de bezerros por vaca e maior longevidade produtiva (6)(7)(8)(9) . Novilhas que emprenham no início da estação reprodutiva e parem também no início da estação de nascimento, apresentam bezerros mais pesados e maior tempo de recuperação pós-parto, resultando em maiores chances de se apresentarem prenhas no início das estações reprodutivas subsequentes (10,11) . Assim, a seleção genética para precocidade sexual em novilhas permite otimizar o ciclo produtivo e em sistemas de produção de bovinos de corte a sustentabilidade econômica está relacionada ao crescimento, eficiência reprodutiva, carcaça e produção (12) .…”

Effect of age at first conception as a selection criterion on growth and carcass traits in Nellore cattle

“…Beef cattle profitability is associated with reduced onset of females' maturity since it allows for a greater number of calves to be produced per cow and increased productive longevity (6)(7)(8)(9) . Heifers that calve earlier during the calving season have heavier calves and a longer post-partum recovery time, resulting in increased chances of displaying early pregnancies in subsequent breeding seasons (10,11) . Thus, the genetic improvement of heifers' sexual precocity allows optimizing the productive cycle, and, in a beef cattle production system, economic sustainability is related to growth, reproductive efficiency, carcass, and production (12) .…”