In two trials, three groups of eight dairy cows were fed for 2 months before calving to achieve condition scores at calving of 1·5 to 2 (low), 2·5 to 3 (medium) and 3·5 to 4 (high). For 16 weeks after calving, all cows were given a complete diet composed of silage, malt distillers' grains, barley, swedes and soya bean meal (metabolizable energy 12·25 and 12·35 MJ/kg dry matter in trials 1 and 2 respectively).

In both trials, significant differences were found between groups in dry-matter intake after calving. Cows that had higher condition scores at calving ate less and reached maximum intake of dry matter later than cows with lower condition scores (high, medium and low condition-score cattle attained maximum intakes in 14·5, 12·7 and 9·3 weeks in trial 1, and in 141, 9·6 and 7·9 weeks in trial 2). In trial 1, no difference was found in milk yield but, in trial 2, cows that had lower condition scores at calving produced slightly more milk. In both trials, cows that had higher condition scores at calving lost more body weight and condition, over a longer period, and started to regain the losses later than cows with lower condition scores. The biological efficiencies of milk production (energy output/energy input) from 8 weeks before calving until 16 weeks after calving were 0·302, 0·299 and 0·295 in trial 1, and 0·312, 0·290 and 0·306 in trial 2, for the low, medium and high groups respectively.

It was concluded that cows with lower condition scores at calving produced more milk directly from food rather than via body fat, were in positive energy balance earlier in lactation and over the total period were biologically more efficient than cows with higher condition scores. There appears to be no benefit from feeding cows to achieve a condition score greater than 1·5 to 2 at calving if high-energy complete diets are offered in early lactation.