Herbage intake, ingestive behaviour, and growth performance in unbred and once-bred hereford × friesian heifers

Abstract

The once-bred heifer beef production system involves mating heifers at 15 months of age to calve as 2-year-olds. This study compared the performance of once-bred Hereford × Friesian heifers mated to Limousin or Charolais sires and the herbage intake of once-bred and never-bred heifers during periods corresponding to late pregnancy and early lactation in the former group. Heifers carrying Limousin-sired (LS) calves had gestation lengths slightly longer than those carrying Charolais-sired (CS) calves (290.4 versus 286.6, pooled SE (PSE) = 1.2 days, P < 0.10), but there was no effect of calf sex on gestation length. The average birth weight of calves was 40 ± 1 kg, there being no difference between female and male, or LS and CS, calves. Dystocia caused mortality rates of 19% in calves and 9% in heifer dams. Female calves had 9 kg lower weaning weights at 142 days of age than male calves, whereas the CS calves had greater weaning weights than LS calves (218.3 versus 204.9 kg, PSE = 3.6 kg, P < 0.01). Dam weaning weights were 443.5 versus 394.7 kg (PSE = 9.5 kg, P < 0.01) and 437.5 versus 400.7 kg (PSE = 9.5 kg, P < 0.05) in heifers suckling female versus male and LS versus CS calves, respectively. During late pregnancy, pregnant heifers had similar ingestive behaviour, herbage intake, and liveweight gains to never-pregnant heifers when offered a restricted pasture allowance of 7 kg dry matter (DM)/head per day. During early lactation, however, never-pregnant and lactating heifers consumed 9.19 versus 11.36 kg organic matter (OM)/head per day, (PSE = 0.63 kg OM/head per day P < 0.05) at a pasture allowance designed to permit ad libitum intakes. During this period, liveweight gains of 1.70 versus 0.61 kg/day (PSE = 0.28 kg/day, P < 0.05) were recorded for the never-pregnant versus lactating heifers. Results are discussed in the context of beef production from unbred and once-bred heifers. © 1993 Taylor & Francis Group, LLC.