| dc.description.abstract | In order to identify selection criteria to improve the reproductive capacity of the female bovine, we studied 132 heifers born in 2011 and 2012, belonging to 5 genetic groups (GG): Angus (A), Hereford (H), AH, HA and Creole (C) in two years (Trials 1 and 2). After weaning, the presence of corpus luteum, live weight, body condition, rump height, rump fat thickness, rib fat thickness and rib eye area were recorded every 28 days. By DNA analysis we determined the genotype for a total of 70 SNPs of genes involved in the hypothalamic-gonadal metabolic pathways, growth and fat metabolism. On the other hand, in order to evaluate the relationships between the beginning of the reproductive life of the females and their productive efficiency, the annual records of 895 cows (217 A, 253 H, 125 C, 116 AH y 184 HA) born between 1986 and 2009 in Experimental Unit Nº 7 - EEA INTA Balcarce were analyzed to estimate the average annual productivity of the cow (PRODAM), its components of (Co) variance and breeding values (EBV). The environmental differences between the two trials evaluated conditioned the age at which the heifers reached puberty, which was higher in those who had lower postweaning gains. HA heifers reached puberty 54±15 days before C (p
<0.05), while the rest of GG did not show differences between themselves (p> 0.05). The rib fat thickness measured by ultrasonography at 450 days of age (15 months) was a good predictor of age at puberty and consequently a selection criterion potentially useful to improve the fertility of the female. Estimation of (co)variance components for PRODAM showed a heritability of 0.14±0.05. Age at puberty of the evaluated heifers was associated with the average annual productivity of their mothers, which would be a good predictor of the productive performance of cows. SNPs in SPAG11 and PTGER2 showed a certain association with age, weight and height at puberty. From the analysis performed, the nutritional conditions immediately after weaning are of vital importance for an earlier presence of the first corpus luteum, an indicator of puberty. The rib fat thickness in the heifers could be used as a selection criterion for sexual precocity. However, it is important for future studies to analyze in more detail the relationship between fat deposition dynamics and the onset of puberty, in order to determine the existence of critical thresholds (minimum and maximum) for the onset of reproductive activity. Selection for sexual precocity provides an opportunity to improve the annual average productivity of cows and thus cattle fertility. At the molecular level, the associations found among the genotypes of the SNPs evaluated should be validated in populations with a larger number of animals before being identified as selection criteria to increase the female fertility | |
