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Four silages were prepared at 1-week intervals from a primary growth of timothy-meadow fescue sward. They were offered to 32 Finnish Ayrshire cows and supplemented with 7 or 10 kg of concentrate containing 0 or 1·15 kg rapeseed meal (RSM). The basal concentrate consisted of barley, oats and molassed sugar-beet pulp (2: 2: 1) and minerals. Diets were arranged 4 × 2 × 2 factorially in a cyclic change-over experiment with four periods of 21 days each.Silages contained 739, 730, 707 and 639 g digestible organic matter (D value) per kg dry matter (DM) for harvests I, II, III and IV, respectively. All dietary factors had marked effects on the performance of the cows but generally interactions between treatments could not be detected. A decrease of 10 g/kg in silage D value decreased energy-corrected milk (ECM) production of the cows by 0·50 kg/day and silage DM intake by 0·162 kg/day. An increment of 1 kg concentrate DM decreased silage DM intake by 0·61 kg and yielded 0·55 kg more ECM per day. Inclusion of RSM into the concentrate increased daily ECM production by 1·7 kg and silage DM intake by 0·60 kg/kg RSM when substituting the basal concentrate. Milk yield and yields of milk constituents decreased curvilinearly with delayed date of harvest the difference being greatest between the last two cuts and thus closely reflected the changes in silage D value. Milk protein concentration increased as apparent digestibility (P < 0.001) and concentrate level in the diet increased (P < 0.001). Milk fat concentration was not affected by the dietary treatments.Marginal ECM production responses to estimated metabolizable energy (ME) intake were higher when intake was manipulated with the date of silage harvest (0·138 kg ECM per MJ additional ME) compared with increased concentrate feeding (0·103); highest response was achieved by RSM feeding (0·244). Additional intake of calculated amino acids absorbed from the small intestine (AAT) manipulated by silage harvest time resulted in the highest marginal response (0·59 g milk protein per g additional AAT), while increased concentrate feeding and inclusion of RSM were equal (0·50 v. 0·49, respectively). Improving silage quality by earlier harvest resulted in higher milk yield, and in greater efficiency in the use of increments of estimated ME and AAT than was seen with increased concentrate feeding. Protein supplementation improved milk production irrespective of silage harvest date.

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Field data from 16 051 Finnish milk recorded herds including milk yield (MY), feed consumption, feed analyses, and the herd effect for milk yield (HMILK) obtained from the national breeding value estimation program, were analysed to detect the influence of concentrate feeding on milk production. HMILKs are deviations from the average national level with mean of 45 kg and SD of 722 kg. Mean MY was 6917 kg and mean dry matter intake (DMI) 5679 kg per cow per year. The effect of concentrate feeding on HMILK and MY was studied by using quantitative [amount of energy (FUI) and concentrates (CI) in the diet] and qualitative [proportion of grain (Gc) or compound feed (Mc) in concentrates or CP content (CPc) of concentrates] diet characteristics as dependent variables in multivariate regression analysis. The general linear effect of CI was 1.18 kg MY/kg CI. Production response of CI decreased with increasing CI as indicated by significant interactions between CI and CI classes. Gc showed a negative relationship with HMILK, but CPc proved to be a more important factor affecting HMILK. Feeding grain instead of compound feed was connected with too low protein content in concentrates. Mc was positively correlated with CP content of concentrates. However, the use of compound feed appeared to give a slight increase in HMILK even after accounting for the effect of CP. ;