Sexual precocity and productivity of beef cattle female under grazing conditions

Abstract

In view of the importance of female reproductive traits as a key profit indicator in beef-cattle production systems, the objective of the present study was to explore the relationships between female sexual precocity and potential predictive traits of easy and early measurement, related to the productive and reproductive efficiency. Heifers born in 2011 and 2012 (n = 132) from five genetic groups (Angus, Hereford, Angus-Hereford, Hereford-Angus and Argentine Creole) in 2 years (Trial 1 and Trial 2) under grazing conditions were evaluated. After weaning, the presence of corpus luteum, liveweight, body condition score, hip height, rump fat thickness and rib fat thickness were recorded every 28 days, and Longissimus muscle area at 15 months of age. Also, to evaluate the relationships between age at puberty and the subsequent production efficiency, the annual records of 895 cows (217 Angus, 253 Hereford, 125 Creole, 116 Angus-Hereford and 184 Hereford-Angus) born between 1986 and 2009 were studied to estimate the average annual productivity of cows, and its components of (Co)variance, heritability and breeding values. Nutritional conditions immediately after weaning were determinants in reaching puberty. The univariate animal model for average annual productivity showed a heritability of 0.14 ± 0.05. Regression multiple and covariance analyses revealed that the rib fat thickness at 450 days of age was a good predictor of age at puberty, but lose some relevance as early selection criterion. Finally, it is important for future studies to analyse in more detail the existence of critical thresholds of fat deposition for the onset of reproductive activity.