Improving the pre-weaning nutrition of calves by supplementation of the cow and/or the calf while grazing low quality pastures. 1. Cow production

Large numbers of weaner calves destined for meat production in Australia are born to cows grazing low quality pastures and have low growth rates to weaning. A study was undertaken in a New South Wales subtropical coastal area (Grafton, 29°38′S, 152°54′E) to increase these growth rates by supplementing cows to mid lactation and/or their calves up to weaning. This paper reports on the effects of these supplementation regimes on cow production. Cows were either not supplemented or supplemented with cottonseed meal twice-a-week at 4.2 kg/head over 145 days, commencing before the expected start of calving. Calves, depending on their treatment group, either had unrestricted access to a ‘creep’ containing a high-energy, high-protein pellet given from 75 or 150 days old, or had no access at all to ‘creep’ feed. However, all cows and their calves had access to mineral blocks. Cottonseed meal-supplemented cows were heavier (408 v. 362 kg) and had higher condition scores (3.3 v. 2.9 units) than non-supplemented cows when weighed and scanned in November 1996, after all cows had calved, and they maintained these differences until April 1997 when calves were weaned. There was a trend for cows, whose calves had access to a ‘creep’ from 150 days old, to gain weight towards the end of lactation whereas cows from other treatment groups lost weight. Non-supplemented cows had a 3-fold greater daily intake of mineral blocks than cottonseed meal cows (178 v. 61 g/cow) providing them with an additional 9.8 g phosphorus/cow. Cottonseed meal cows were observed to have fewer grazing incidences (60 v. 75% of activities) during supplementation than non-supplemented cows, with grazing instances increasing for all cows during lactation. Cottonseed meal cows whose calves had access to ‘creep’ feed continued to have fewer grazing incidences (74 v. 90%) than other cows 70 days post-supplementation. Milk yield was higher in cottonseed meal cows than in non-supplemented cows (4.8 v. 4.0 kg/day). Following a synchronised insemination program, at the end of cottonseed meal supplementation, the pregnancy rate of formerly cottonseed meal-supplemented cows was twice that (40 v. 20%) of non-supplemented cows. The combination of cottonseed meal supplements and macrominerals from blocks improved cow liveweight, condition score, milk yield and fertility, and was a successful strategy for increasing production from low quality pastures.