Key points are not available for this paper at this time.
Nutritional stress during gestation in tropical grazing systems can impair maternal performance and foetal development. This study evaluated the effects of weaning strategy and dam parity on the feedlot performance, carcass traits, and mRNA abundance profiles of Nelore young bulls that were in utero at the time of the weaning intervention. A randomised 2 × 2 factorial design was utilised with 57 Nelore bulls. The treatments were composed of early (EW; 150 d lactation) versus conventional weaning (CW; 240 d lactation) and dam parity (multiparous (MP) or secundiparous (SP)). The data were analysed considering the animal as an experimental unit by using the Mixed procedure, considering the WS, DP as a fixed effect, and the two-way interaction in the model. There was an interaction between WS × DP on performance measures in the feedlot, with CW-SP bulls showing smaller initial BW (P < 0.05) and a trend for smaller final BW (P = 0.07) compared to other groups. For carcass traits, there was only a tendency (P = 0.09) for WS × DP interaction on subcutaneous fat thickness, which was small in CW-SP bulls compared to other groups. Additionally, there was a WS × DP interaction (P < 0.05) with CW-MP bulls showing a small number of muscle fibres than EW-SP and CW-MP offspring, but no significant differences with EW-MP offspring. Furthermore, bulls from CW dams exhibited greater cross-sectional area and diameter compared to EW. Regarding gene regulation, a WS × DP interaction with the GSK3B gene (P < 0.05) showed smaller expression in CW-SP compared to CW-MP and EW-MP. Conversely, the SCD1 gene (P < 0.05) showed greater expression in EW-MP bulls compared to CW-MP and EW-SP offspring. The genes PAX7, MYF5, IGFR1, and PPARG showed a tendency (P < 0.10) for greater expression in MP bulls than the SP group. The gene EIF4E showed significantly greater expression (P < 0.05) in bulls from the EW group compared to the CW group, while the gene MTOR tended (P = 0.10) to have greater expression in the EW group compared to the CW group. These findings indicate that early weaning improves maternal reserves and positively programmes offspring growth. The observed alterations in gene expression profiles suggest that alleviating maternal nutritional stress during gestation has long-term consequences on the molecular machinery regulating muscle growth and turnover in the offspring.
Carlis et al. (Thu,) studied this question.