Lamb growth rates improve as goat to sheep ratio increases

Abstract

Lambs were rotationally grazed with ewes in a 'sheep only' system and with low, medium, and high proportions,of wether goats from October to March on dryland perennial ryegrass-white clover pastures in Canterbury. Lambs grazed with ewes and goats until they were weaned; then they grazed ahead of other stock. Treatment ratios of adult stock on a per head basis were 3 ewes:1 goat ('low goats'), 3 ewes:2 goats ('medium goats') and 3 ewes:3 goats ('high goats'). The ewe:lamb ratio was 1:1.35 on all treatments. Lamb growth rates (g/day) were 152 for 'sheep only', and 169, 185 and 203 for low, medium and high goat treatments respectively. As each treatment lamb reached a target draft weight, it was replaced by a lighter lamb for finishing. In comparison with the 'sheep only' treatment, an extra 1.6 lambs/ha were drafted off the 'medium goat' and an additional 2.6-lambs/ha off the 'high goat' treatment by the end of January. Increasing the proportion of goats:ewes increased the supply of white clover in pastures especially after lambs were weaned. Examination of faecal plant material showed 30% clover in the diet of lambs in a 'sheep only' system, increasing as the goat:sheep ratio increased to 60% clover in the 'high goat' treatment. Keywords white clover, perennial ryegrass, goats, sheep,grazing management, diet, lamb