Effect of herbage allowance on the performance of pregnant beef heifers

G.B. Nicoll, D.C. Smeaton and K.R. McGuire

Ruakura Animal Research Station, Ministry of Agriculture and Fisheries, Hamilton and Whatawhata Hill Country Research Centre, Ministry of Agriculture and Fisheries, Hamilton

Proceedings of the New Zealand Society of Animal Production. 1984, 44: 173-176

Two experiments studied the effects of herbage allowance in the latter half of pregnancy on the performance of 18-month beef heifers. In Experiment 1, 54 heifers were offered daily allowances of 4.5 (H) or 3.3 (M1) kg DM/100 kg live weight (LW), and in Experiment 2, 64 heifers were offered 3.1 (M2) or 1.9 (L) kg DM/100 kg LW.

Average daily gain to post-calving weight (net ADG) for the H and M1 heifers in Experiment 1 was 0.46 and 0.34 kg/d (P<0.001). The post- partum anoestrous interval (PPAI) was short in both groups (H+ 42.7 and M1 = 49.2 days; P<0.10). H calves were 1.8 kg heavier at birth and 7.6 kg heavier at weaning than M1 calves (P<0.05). In Experiment 2, M2 and L heifer net ADG was 0.23 and -0.03 kg/d respectively (P<0.001). The PPAI was 28.4 d shorter for M2 than L heifers (P<0.001). Birth and weaning weights of M2 calves were heavier by 1.8 kg (P<0.07) and 14.0 kg (P<0.05) respectively than those of L calves.

Results suggest that a herbage allowance of around 3 kg DM/100 kg LW over the latter half of gestation may be adequate for satisfactory performance of yearling-mated heifers.

Keywords: NZSAPAB; Herbage allowance; beef heifers; growth; calving date; post- partum anoestrous interval

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