Primary growths of perennial ryegrass (Lolium perenne) were cut on 22 May and 12 June and wilted for 24 h prior to ensiling. A 40 : 60 mixture of the two silages was offered ad libitum with two pelleted supplements. Supplement Ba was a mixture of (dry matter (DM) basis) 932 g rolled barley and 68 g fish meal per kg. Supplement SBP/FF consisted of 555 g unmolassed beet pulp, 314 g extracted rice bran, 56 g fat prills and 75 g soya-bean meal per kg. The factorial combination of the two supplements (Ba and SBP/FF) given at two levels, 6 kg DM (L) or 12 kg DM (H), provided the four treatments imposed over weeks 3 to 10 of lactation on 40 British Friesian cows. During weeks 12 to 20 of lactation (post-experiment period) the cows were given an equal mixture of the two concentrates at 9 kg DM per day.Supplement Ba contained less ash (31 v. 94 g/kg), acid-detergent fibre (68 v. 218 g/kg) and fat (29 v. 77 g/kg) but more starch (558 v. 89 g/kg) and digestible organic matter in the dry matter in vitro (DOMD) (781 v. 627 g/kg) than SBP/FF. The concentration of total nitrogen (N) was similar at 25-6 g/kg. Silage had a DOMD of 643 g/kg, a pH of 3-8 and proportionately 0-82 of fermentation acids as lactic acid.Apparent digestibility of gross energy was higher for Ba diets (0-748) than for SBP/FF (0-704). Cows given SBP/FF ate 0-9 kg more silage DM than those given Ba (P < 0-01) but there was no difference in digestible energy intake or in substitution rate (-0-37 kg silage DM per kg additional supplement DM).Increasing the amount of supplement increased milk yield by 3-9 kg/day (P < 0-001). Cows given SBP/FF yielded on average 1-6 kg more milk than those given Ba (P < 0-05). However, this increased output consisted almost entirely of lactose and water as a result of a high concentration of fat in the milk of cows given Ba at the low level (46-3 g/kg). Further, the concentration of protein was less with SBP/FF (28-0 g/kg) than with Ba (29-2 g/kg).The effects of SBP/FF in early lactation were translated into a positive residual effect in mid lactation equivalent to the immediate effect. In contrast, raising yield by increasing the amount of supplement did not result in increased output subsequently.The results show that a supplement of fibre and fat despite having a lower digestibility than barley can produce more milk but a similar yield of fat and protein provided silage is offered ad libitum.

Silages were made from the primary growth of perennial ryegrass (Lolium perenne) or red clover (Trifolium pratense) and were given ad libitum to 52 British Friesian cows, together with 70 kg dry matter per day of a barley/ground maize/soya bean supplement in 2 years. Twenty of the cows were used in both years, providing a total of 72 observations. Three treatments were imposed during weeks 3 t o 20 of lactation: red clover silage, (RC/RC); red clover silage, weeks 3 to 10, grass silage weeks 12 to 20 (RC/PRG); grass silage (PRG/PRG).Apparent digestibility of the gross energy assessed in lactation weeks 14 and 15 was slightly lower for red clover than for perennial ryegrass (0·683, 0·706 and 0·701 for treatments RC/RC, RC/PRG and PRG/PRG respectively). There was no effect of previous treatment on the digestibility of perennial ryegrass diets (RC/PRG v. PRG/PRG). Cows given red clover silage consumed proportionately 1·22 of the dry matter and 1·09 of the digestible energy ingested by those given perennial ryegrass. The intake of perennial ryegrass in mid lactation was similar, irrespective of early lactation treatment.During weeks 3 to 20, cows given red clover yielded 1·9 kg more milk than did those given perennial ryegrass (P < 0·01). However, this milk had a significantly lower concentration of fat (P < 0·01; 37·2 and 41·2 g/kg for treatment RC/RC and PRG/PRG respectively). In mid lactation the cows that had received red clover silage in early lactation (RC/PRG) had the lowest yield of milk, milk fat, protein and lactose and the difference between this treatment and PRG/PRG was significant for milk and milk fat yields (P < 0·05).Red clover silage rather than perennial ryegrass silage of similar digestibility resulted in higher silage intake and higher yields of milk, milk protein and lactose. However, the strategic use of red clover silage to increase yield in early lactation did not induce positive residual effects in mid lactation; rather, there was evidence of a negative effect on milk and milk-fat yield.

Thirty-six British Holstein-Friesian cows were offered 9 kg dry matter (DM) daily of one of 12 concentrates together with grass silage ad libitum in a cyclical change-over design experiment during lactation weeks 8 to 22. The carbohydrate source in the concentrates was either mainly starch, mainly digestible fibre or a 1:1 mixture. Each concentrate type was formulated to provide 120,160,200 or 240 g crude protein (CP) per kg DM and similar metabolizable energy concentration. Silage contained 142 g CP per kg DM, in vivo digestible organic matter was 0-690 kg/kg DM, pH 4-4 and ammonia-N 172-2 g/kg total nitrogen. Silage intake increased as fibre replaced starch in the concentrate. Apparent digestibility of organic matter and energy were highest for starch-based concentrates, but there was no effect of carbohydrate source on yields of milk and milk solids. Milk protein concentration was depressed by feeding mixed or fibrous carbohydrates. Silage intake increased on average by 0-13 kg DM per additional 10 g/kg CP in the concentrate. The digestibility of the diet was not affected by increasing CP except for nitrogen. Milk yield increased by 0-028 kg per additional g/kg CP in the concentrate and there were linear effects ofCP on yields of milk solids. As CP increased, milk fat concentration tended to rise ivith starch but was depressed both overall and by offering mixed or fibrous carbohydrates. In contrast milk protein concentration increased with mixed and fibrous carbohydrates but not with starch. It is concluded that when silage is given ad libitum with 9 kg/day concentrates, CP level has more effect than source of carbohydrate on milk production.

ABSTRACT1. The primary growth and first regrowth of perennial ryegrass were preserved either without additive (NA), or with a mixture consisting of equal volumes of formic acid and formalin at 10·0 and 13·01/t fresh crop for primary growth and regrowth herbage respectively (35 g formaldehyde per kg crude protein) (FF). The silages were given ad libitum to 40 lactating British Friesian heifers and cows, with a supplement of either pelleted ground maize (104 g crude protein per kg dry matter) (LP) or pelleted ground maize and soya bean meal (254 g crude protein per kg dry matter) (HP), at 6·1 and 7·1 kg per head per day for heifers and cows respectively. The primary growth silage was given from weeks 4 to 14 and the regrowth from weeks 15 to 22 of lactation. The silages were supplemented with urea so that the dietary supply of rumen degradable protein exceeded 7·8g/MJ metabolizable energy.2. Silage FF had lower concentrations of both fermentation acids and ammonia-nitrogen than silage NA. The digestibility of the dry matter, energy and crude protein of the diet containing silage FF was significantly less than that of diets containing silage NA when cows were given primary growth material (P < 0·001). But silage treatment had no significant effect on the digestibility of cellulose. When cows were given regrowth silage, silage treatment had no significant effect on the digestibility of dry matter, energy and cellulose, but formic acid/formaldehyde reduced the digestibility of crude protein (P < 0·01). The inclusion of soya bean meal in the supplement significantly increased the digestibility of crude protein, dry matter and energy, but when cows were given the primary growth silage the effect on the digestibility of dry matter and energy was only apparent with silage NA.3. Cows and heifers given silage FF from primary growth consumed 160g/kg more dry matter than those given silage NA (P < 0·01). This effect was not apparent when the animals were given regrowth silage. The effect of formic acid/formaldehyde on the intake of digestible energy was not significant in either period on the trial, but the inclusion of soya bean meal in the pellet significantly increased the intake of digestible energy (P < 0·01).4. Cows and heifers given silage FF from primary growth produced 90g/kg more milk and 50g/kg more solids-corrected milk than those given silage NA, but the differences were not significant and these trends were not apparent when regrowth silage was given. An increase in the crude protein content of supplement increased the milk (P < 0·01) and protein yield (P < 0·05) of cows, but not heifers, when they were given primary growth silage. The effect was less when milk output was expressed in terms of solids-corrected milk since milk fat content tended to fall when cows were given the HP supplement. Treatments had no significant effect on live-weight change.5. It is suggested that the increases in milk output were mediated via changes in the supply of energy rather than of protein.

Three experiments were conducted in the early grazing seasons of 1982–84 inclusive. Autumn-calved lactating British Friesian cows grazed a perennial ryegrass pasture either by strip grazing to leave 80 mm residual herbage (SG) or by rotationally grazing six paddocks on a fixed pre-determined cycle (PG). They were offered grazing only or grazing and average quality grass silage (S) or a 1: 1 mix of silage and ensiled brewers' grains (SB) given individually overnight in a cubicle house.In experiment 1, cows received treatments SG or SGS. The intake of silage dry matter (DM) was 4·3 kg/day and the estimated intakes of herbage DM from measured animal performance were 15·2 and 8·9 kg/day respectively. Milk yields were 18·4 and 15·3 kg/day, the concentrations of fat and protein in the milk were 38·0, 41·8 and 33·3, 30·8 g/kg and live-weight change was +679 and +348 g/day for treatments SG and SGS respectively.For experiment 2, cows received treatments SG, PG or PGS and grazing stocking rates were 5·2, 5·5 and 11·0 cows per ha respectively. Silage intake was 6·1 kg/day DM and the estimated intakes of herbage DM were 14·2, 15·3 and 7·7 kg/day respectively. Milk yields were 18·2, 18·2 and 16·1 kg/day, the concentrations of fat and protein were 41·6, 39·8, 42·3 and 33·3, 33·0, 30·4 g/kg and live-weight change was +325, +540 and +161 g/day for treatments SG, PG and PGS respectively.For experiment 3, cows received treatments PG, PGS or PGSB and grazing stocking rates were 5·8, 11·6 and 11·6 cows per ha respectively. The intakes of silage and silage plus brewers' grains DM were 6·5 and 8·5 kg/day. The estimated intakes of herbage DM were 14·2, 7·2 and 7·3 kg/day, milk yields were 18·7, 14·6 and 18·9 kg/day, the concentration of fat and protein in the milk were 37·3, 42·1, 40·3 and 33·4, 32·6, 32·9 g/kg and live-weight change was +425, +415 and +441 g/day for treatments PG, PGS and PGSB respectively.The results show that offering silage overnight allowed grazing stocking rates to be doubled, raised the concentration of fat in the milk and depressed the yields of milk and protein. When brewers' grains were given with the silage, yields of milk fat and protein were greater compared with when silage was offered alone and the yield of fat was greater than for herbage alone.