Effect of body condition and suckling restriction with and without presence of the calf on cow and calf performance.

Nutrition and suckling are largely recognised as the most important factors affecting the postpartum period and consequently the reproductive efficiency of beef cattle. The aim of this study was to evaluate the effects of body condition score (BCS) and suckling restriction with and without the presence of the calf on milk production, reproductive efficiency and calf performance. Sixty-three crossbred (Angus × Hereford) multiparous cows were managed to maintain different BCS at calving and thereafter (low vs moderate; L, n= 31 and M, n= 32). Within each group of BCS (L and M) at week 9 postpartum (66 ± 0.88 days postpartum) cows were assigned to three suckling treatments (ST): (i) suckling ad libitum(S, n= 20); (ii) calves fitted with nose plates during 14 days remaining with their dams (NP, n= 22); and (iii) calves were completely removed from their dams for 14 days, and thereafter returned (CR, n= 21). Milk production was assessed by milking procedure at Day 65 (the day before onset of ST) and every 20–22 days until the end of the experiment. Cows were bled via jugular venipuncture every 28 days from Day –98 (Day 0 = calving) until Day 66. From Day 66 cows were bled every 7 days until the end of the mating period (Day 128). Concentrations of progesterone, non-esterified fatty acids and β-hydroxybutyrate acid and insulin were measured. Presence of corpus luteum (CL) was recorded and maximum follicle diameter was measured in all cows from the onset of the ST (Day 66) and during the following 4 weeks (until Day 94) in a weekly frequency. At Day 94, more cows (P< 0.001) in NP and in CR had CL compared with S cows (68, 57 and 21% for NP, CR and S, respectively). At that time, more cows in M-BCS presented CL than cows in L-BCS (77 vs 25; P< 0.0001). Within M-BCS, there were no differences in milk production between ST groups, while L-BCS cows with NP or CR produced less milk than S cows. Calf liveweight at weaning was 159.3 ± 3.1, 150.1 ± 2.9 and 147.0 ± 3.1 kg for S, NP and CR, respectively (P< 0.001). Suckling restriction with and without the presence of the calf had similar effects on reproductive performance, milk production and calf growth, while BCS interacted with ST to influence milk production. These results indicate that temporary suckling restriction could be an excellent management tool to increase reproductive performance of cows in moderate condition. [ABSTRACT FROM AUTHOR]