RESUMEN
This study aimed to investigate the effect of age at weaning of calves on non-esterified fatty acids (NEFA) and reproductive parameters of beef cows. Animals (n = 65) were randomly assigned to three treatments after calving: hyper-early weaning (W30) at 32 ± 0.89 days, early weaning (W75) at 77 ± 0.95 days, and conventional weaning (W180) at 183 ± 0.82 days. Body weight (BW) and body condition score (BCS) were evaluated at parturition (AP) and at 30, 45, 64, 81, 100 and 115 days postpartum (dPP). Blood samples were collected to analyze NEFA levels and progesterone (P4) at 30, 45, 64 and 81 dPP. Higher BW and BCS were observed from 64 to 115 dPP in W30 cows than W180 ones (p < 0.05). Cows subjected to W30 condition had higher levels of NEFA at 30 dPP compared to 64 and 81 dPP (p < 0.05). We also observed that cows from W180 group showed decreased levels of NEFA at 30 dPP compared to 45 (p < 0.01) and 64 dPP (p < 0.05). The highest P4 level was observed at 64 dPP in W30 cows compared to W75 and W180 (p < 0.05). We also observed higher CR of W30 (86%) compared to W180 (47%) at 45 dPP (p < 0.05). The overall pregnancy rate (PR) was higher for W30 (95.5%) than W180 (73.9%). In addition, higher BW at calving and P4 levels at 30 dPP were positively correlated with the possibility of pregnancy (p < 0.05). Improvement in BW and BCS were observed in cows subjected to hyper-early weaning management. However, levels of NEFA decreased as the postpartum period progressed. We concluded that cows who weaned calves hyper-early have greater chances of increasing cyclicity and PRs.
