Two grass sUages made in June and two made in September, all from the same field, were compared in a 16-week winter-feeding experiment with 12 Ayrshire cows. The silages were fed ad lib. with a supplement of barley and groundnut eake. One of the sUages made in June and one made in September had been treated with \ gallon of formie acid per ton of herbage when cut, whereas the other two silages were untreated. The contents of digestible organic matter in the sQage DM made with and without the acid additive were 67-4 and 63-8%, respectively, in the June silage, and 66-1 and 62-7% in the September sUage. The intakes of silage and total DM were higher in the treatments containing the acid-treated silages than in those containing the untreated sflages. The mean daily milk yields from cows fed on the sUages made with and without the additive were 36-3 and 33-8 lb (16-5 and 15-3 kg), respectively, for sflages made in June, and 35-4 and 34-1 lb (16-0 and 15-5 kg) for those made in September. The solids-not-fat (S.N.F.) contents of the milk averaged 8-60 and 8-50% respectively, from the silages with and without the additive. It is concluded that the silage with the formic-acid additive was superior to the untreated silage as a feed for dairy cows.

Three grass silages of different chop lengths made from a uniform sward of S23 perennial ryegrass were compared in four experiments including a feeding experiment with twelve lactating cows, an eating behaviour study, a rate of passage investigation and a selection trial. The silages had median chop lengths of 9-4. 17-4 and 720 mm, termed short, medium and long, with pH values of 3-93, 3-94 and 417 and D-values of 659, 65-2 and 64 4 respectively.The daily intakes of silage DM and the daily milk yields increased as silage chop length decreased. The milk yield response to shorter chopping was significant with a supplement of groundnut but not significant with a supplement of sugar-beet pulp. Chop length had small and generally non-significant effects on milk composition.Eating and ruminating times expressed as min per kg DM decreased as silage chop length decreased but the retention time ofthe silage residues in the entire digestive tract was not significantly affected by chop length. When offered simultaneously, the intakes of the individual silages were 52 2, 319 and 15 9% ofthe total DM intake for the short, medium and long treatments respectively.Although silage with a chop length of 9 mm had nutritional advantages over longer silages, it is concluded that the mechanical and economic aspects of silage making must be considered fully when defining optimum chop length.

Grass silage of hjgh digestibility made in late May from S23 perennial ryegrass was offered to twelve Ayrshire cows in a 16-week winter-feeding experiment. The silage had a DM content of 27-2% and contained 14 7% crude protein and 70-3% digestible organic matter in the DM. The silage was fed ad libitum and was the sole feed in the control treatment.

Two grass silages made from perennial ryegrass, and with D-values of 0-616 and 0-655, were offered ad libitum to 18 Ayrshire cows in two feeding experiments. On the control treatment the silages were supplemented with soybean meal only, and on the other two treatments with equal weights of DM from either barley or dried molassed sugar-beet pulp plus the same weight of soya as on the control treatment. The daily intakes of silage DM were not significantly different on the barley and beet-pulp treatments, and, on average, the intake of silage DM was reduced by 0-44 and 0-40 kg by feeding 1 kg barley and beet pulp DM respectively.The daily milk yields were not significantly different on the barley and beet-pulp treatments with mean values of 19-2 and 19-6 kg per cow respectively compared with 17-1 kg on the control treatment. On the barley and beet-pulp treatments the fat, SNF, CP and lactose concentrations in the milk and the live weights of the cows were not significantly different. It is concluded that the barley and beet pulp had similar feeding values and replacement rates when used as supplements with grass silage, and that the two feeds were interchangeable on an equal DM basis.

Three grass silages, all made in mid-Jnne from the same herbage, were compared in a 12-week winter-feeding experiment with 12 Ayrshire cows. The silages were fed ad lib. witb a supplement of moist barley and gronndnut cake. Silage A was made from unwilted berbage witb no additive, silage B from identical berbage treated witb \ gal of formic acid/ton (2-24 L/tonne) of berbage, and silage C from tbe herbage after wilting for 28 b. Tbe DM contents of silages A, B and C were 20-5, 21-1 and 31-8%, respectively, and tbe contents of digestible organic matter in tbe DM were 58-9, 68-8 and 67-8%. Silage and total DM intake were bigbest on tbe treatment containing sOage B. Tbe mean dafly milk yields on tbe treatments witb sflages A, B and C were 35-1, 38-0 and 34-3 Ib (15-9, 17-2 and 15-6 kg), respectively and tbe solids-not-fat (S.N.F.) contents of tbe milk averaged 8-53, 8-54 and 8-50%. It is concluded tbat silage B, tbe unwilted silage witb formicacid additive, was superior to botb tbe untreated and tbe wilted silage as a feed for dairy cows. INTRODUCnON