The impact on beef herd performance of weaning calves before or after cows clean-up low quality summer pasture was assessed. Surplus pasture was cleaned-up by weaned cows, and unweaned cows and calves, using either a single hard grazing (1 x 56 d rotation) or 2 x 28 d rotations commencing 20 January in 1986 and 22 January in 1987. Pastures had accumulated about 4.5 t dry matter (DM) /ha after being retired from grazing in late November as a pasture control measure. Weaned calves were fed quality (70+% green) pasture at pre-graze masses of 1.5, 2.0 or 2.3 t DM/ha under set-stocking 1986, or a fast rotation, 1987. Unweaned calves gained 38 and 39 kg over the 8 weeks in 1986 and 1987, respectively. There was no effect of pasture clean-up method on calf growth. Calves in the best weaned treatment gained just 23 and 30 kg in 1986 and 1987, respectively. Weaned calves suffered from facial eczema (mean gamma glutamyl transferase )GGT) 290 iu) in 1986 which reduced their growth. The rank pasture reduced exposure to facial eczema (mean GGT cows and calves 15 iu) Calf age had no effect on calf growth rates. Weaned cows lost 3 and 15 kg in each year. Unweaned cows lost 20 kg more than weaned cows. Benefits of late weaning were increased calf growth and reduced demand for quality autumn pasture. They were considered to outweigh costs of cow liveweight loss.
Proceedings of the New Zealand Society of Animal Production, Volume 48, , 201-206, 1988
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