The advent of twinning in suckler cows, through the application of multiple ovulation and embryo transfer techniques has provided a means of increasing the biological efficiency of the suckled calf system of beef production. However, even with improvement in output the need remains for twin-bearing suckler cows to be fed economically. This can be achieved by making effective use of summer and autumn grazing which on most farms provides a high plane of nutrition and allows the cows to increase their body reserves. This generous level of feeding may be followed by more stringent and controlled feeding in winter and early spring, when conserved feeds, grain and by-products are fed. This restriction leads to a reduction in feed costs and also to a depletion of the accumulated resrves.