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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. ;

Barley was partially replaced with either rapeseed oil (RSO), unextracted steamexploded birch wood (W1) or extracted steam-exploded birch wood (W2), and fed to 10 lactating cows (5 multiparous and 5 primiparous cows) in comparison to rolled barley and oats. The experiment was designed in two balanced 5x5 Latin squares. The experimental periods lasted for 4 weeks and the cows were fed with a fixed amount of 8 kg (air dry basis) concentrate in two equal portions. Timothy dominant unwilted grass silage was provided ad libitum. The nutrient digestibility, blood metabolites, milk yield and composition were studied. Grass silage intake decreased by replacing barley with RSO and increased with W 1 and W2. Oat feeding also increased silage intake compared to barley feeding. Oat feeding decreased the digestibility ofthe organic matter (OM) compared to barley. No significant difference was observed between diets in plasma concentrations of insulin, free fatty acids, acetoacetate, β-hydroxybutyrate and glucose. Replacing part of the barley with RSO increased milk yield by 1.3 kg and 0.87 kg compared to oats and barley feeding, respectively. Replacement of barley by low energy birch wood decreased milk yield. Both RSO and oat feeding decreased milk protein content. Milk urea concentration was elevated by oats and depressed by RSO and birch wood. RSO and oat feeding decreased the short chain fatty acid content of milk, with a concomitant increase in stearic and oleic acids.

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Associations between protein feeding and reproductive efficiency in the dairy cow are reviewed. Examination of published data indicated that reproductive responses assessed as days open, services per conception or conception rate following changes in protein feeding tend to be inconsistent. Discrepancies can arise due to between-study variations in experimental design, statistical analysis, sample population size, uterine health, cow age, parity, reproductive management or nutrient intake. Detri-mental effects on reproductive efficiency following periods of excessive protein feeding are often attributed to increases in tissue urea and ammonia oncentrations leading to impaired reproductive hysiology, modified endocrine function or exacerbated postpartum negative energy balance. Examination of data collected from Finnish dairy herds (n = 16 051) participating in the national milk recording scheme during 1993 indicated that milk production was maximised in herds fed diets containing 180 g crude protein/kg dry matter. In contrast, no consistent relationships were identified between increases in on-farm protein feeding necessary to secure higher milk production and herd reproductive efficiency assessed as calving interval, first service interval and number of inseminations per calving. Further examination of data derived from 5 437 herds within the National recording scheme indicated that on-farm reproductive efficiency was independent of large variations in the mean annual urea concentration of bulk tank milk. It is concluded that increases in the crude protein content of Finnish dairy cow rations from 150 to between 170 and 180 g/kg dry matter would allow improvements in milk production to be realised without leading to significant reductions in reproductive efficiency.;