Fetal programming effects of early weaning on subsequent parity calf performance

Mature Simmental × Angus cows [n = 147; body weight (BW) = 590 ± 72 kg] were used to evaluate the effects of early weaning on subsequent parity calf growth performance and carcass characteristics. Cows were assigned to one of two treatments based on their previous calf's weaning age: early wean (EW) or conventional wean (CW). Dams assigned to the EW treatment had calves previously weaned at 88 ± 6 d of age, whereas dams assigned to the CW treatment had calves previously weaned at 185 ± 6 d of age. Cow BW and body condition scores (BCS) were monitored during the experiment. All cows were managed as a common group from the onset of the experiment at breeding until final pregnancy check of their next production cycle 462 d later. All calves in the experiment were managed as one group and weaned at a single time point, then feedlot performance and carcass characteristics were evaluated. Initial cow BW was different (P < 0.05), so it was included as a covariate for cow BW analysis. There was a treatment × date interaction (P < 0.01) for cow BW and cow BCS. Cow BW was consistently greater for the EW treatment from day 39 to the end of the experiment (P < 0.01). Cow BCS were not different at the onset of the experiment (P = 0.20), although after breeding and throughout lactation, BCS diverged between treatments and the EW treatment consistently had greater (P < 0.01) BCS than the CW treatment throughout the entire subsequent lactation. Gestation length was not different (P = 0.21) between treatments, yet calf birth BW was greater (P = 0.05) for the EW treatment. Neither artificially inseminated pregnancy percentage nor overall pregnancy percentage was different between treatments (P ≥ 0.61). Despite the greater birth BW for the EW treatment and no difference (P = 0.25) in milk production, weaning BW was not different (P = 0.50) between treatments. Feedlot performance measures were not different (P ≥ 0.13) between treatments, including feedlot arrival weight, final BW, average daily gain, dry matter intake, and gain to feed. Final carcass characteristics were not different (P ≥ 0.33) between treatments, including dressing percentage, hot carcass weight, LM area, 12th rib fat thickness, kidney, pelvic, heart fat percentage, USDA yield grade, and marbling score. Thus, early weaning resulted in improved BW and BCS of cows as well as increased birth BW of subsequent calf, although that did not transpire into differences in postnatal growth performance or carcass traits.