ABSTRACT
Summary In many parts of the world where year-round grazing is feasible, complementary forages such as oats or sorghum are sown to impove the quantity and quality of the forage available at specific periods. Experiments in which these crops complement well-fertilized grassland have generally not shown an increase in animal production compared with all-grassland systems. The present experiment aimed to determine the effects of a simulated complementary forage crop on pasture yield and on the production of breeding ewes. Eight groups of 10 sheep grazed 0.6-ha plots of Phalaris aquatica L.-Trifolium repens L., and eight groups of 10 sheep grazed 0.8-ha plots. To break the nexus between pasture and crop growth rate, the provision of a complementary forage crop was simulated by giving the ewes a ration of 250 g/ewe/day oat grain of c. 70% organic-matter digestibility, equivalent to almost half their basic maintenance requiremnt. It was supplied for 7-week periods at mating, during lambing, on both occasions, or not at all. The four treatments were replicated twice at each stocking rate. To simulate the effects of withdrawing part of a farm from grazing to grow a complemetary forage, stocking rates were increased by 10% for some weeks before each feeding period. Fine-wool merino ewes were used for 4 years, then crossbred ewes mated with Dorset rams were used for 2 years. The treatments did not significantly affect forage availability, wool production, reproductive performance of the ewes, or weaning weight of their lambs. There were no interactions with stocking rate even in an abnormally dry year or with the high twinning rates of the last 2 years, although production/animal was generally lower at the higher stocking rate. The experiment is considered in relation to other published comparisons. The importance of ensuring that the quantity and quality of the complement is consistently and materially superior to the pasture it replaces is briefly discussed.
