Two levels of steaming-up and two levels of concentrate feeding after calving were compared in a feeding trial extending over a complete lactation using sixteen autumn-calving Ayrshire cows in each of 2 years. On the high and low levels of steaming-up 3·3 and 1·6 cwt of concentrates respectively were fed per cow in the 5 weeks before calving. On the high and low levels of concentrate feeding after calving the concentrates were fed at rates of 4·1 and 2·2 lb per 10 lb of milk respectively from the third day after calving until spring grazing began. The total weight of concentrates fed after calving was 25·8 cwt per cow on the high treatment and 12·1 cwt on the low treatment. All the cows grazed good pasture in the autumn and the following spring and had a ration of 9–11 lb of hay and 50–90 lb of grass silage per day during the winter feeding period. During this period the estimated mean intakes of starch equivalent on the high and low concentrate treatments were 17 and 13 lb/day, which were equivalent to 122 and 103% of Woodman's standards respectively.

Milk yield, milk quality, length of lactation and live weight were not affected by the difference between the steaming-up treatments, and no interaction between steaming-up and post-calving treatments was found. Average milk yields in the first 70 and 140 days after calving and in the complete lactations were all higher on the high post-calving concentrate treatment than on the low treatment, and the response per 1 lb additional starch equivalent fed was 1·05 lb milk. The fat content of the milk was similar on all treatments whereas the S.N.F. content increased from 8·64% on the low treatment to 8·82% on the high treatment, giving a response of 0·045% S.N.F. per 1 lb of additional starch equivalent.

Larger losses in live weight occurred on the low treatment in the first 10 weeks after calving than on the high treatment, but in both groups the weights were almost identical after 45 weeks.