Modelling the long-term consequences of undernutrition of cows grazing semiarid range for the growth of their progeny

Undernutrition of cows grazing semi-arid range as a result of drought or heavy stocking rates reduces prenatal and pre-weaning growth of their calves. A mechanistic model has been developed that simulates the productivity of vegetation and cattle on semi-arid savanna rangeland in southern Africa. When cows are stocked at 0.200 cows/ha instead of 0.123 cows/ha the model predicted that empty body weights of their progeny at birth and weaning would be reduced by 2.9 and 43.8 kg, respectively. If all young animals are stocked at 0.22 animals/ha after weaning, differences in empty body weight at weaning are predicted to persist almost unchanged for a further two years. The model also predicted that undernutrition of cattle aged 21 months would be followed by partial compensatory growth. Comparison of simulated results with data from experiments in Zimbabwe indicates that the model realistically simulates the effects of stocking rate on cattle growth.