STTMMARY. Seven changeover experiments were conducted to examine the effect of giving restricted amounts of concentrates on the voluntary intake of different roughages by non-lactating dairy cows. The addition of up to 6 kg concentrates daily to the diet of cows receiving roughage ad lib. caused little change in the intake of hay and a small increase in the intake of barley straw. Larger amounts of concentrates of 6 and 8 kg daily reduced hay intake by between 0-2 and 0-4 kg dry matter/kg concentrate dry matter given. When concentrates were given to the cows the rate of decline in intake of hay tended to be greatest with the hays of highest digestibility. The daily addition of up to 8 kg concentrates to the diet of cows offered silage ad lib. caused only small depressions in the intake of silage. The results are discussed in relation to recent work on this subject with cattle and sheep.

The dry-matter intake of silage was increased when the silage had a higher dry-matter content and when the time of access to the silage was increased from 3 to 24 h. Concentrate supplementation had a greater influence in depressing the intake of hay than that of silage. Only a small difference was observed in the replacement of hay by concentrates when the concentrates were given with two hays of different dry-matter digestibility. Concentrates with a relatively high protein content depressed roughage intake to a lesser extent than concentrates with a low protein content.

Lucerne was ensiled at various dry matter contents, within the range of 19·8% to 39·6%. An increase was found in lactic acid production, with a consequent decrease in volatile acid and volatile base content, up to the level of 33·9% dry matter. The dry matter intake of cows was increased by feeding silage with a high dry matter content.

The value of lacerating or chopping herbage for silage has been indicated by research work in this country and overseas. NASH (1) has shown that rather better silage can be made from high-protein grass lacerated before ensiling than from similar herbage to which has been added 20 Ib. molasses per ton. WOODWARD and SHEPHERD (2) noted that the less drastic treatment of chopping the herbage also had a beneficial effect on the quality of the silage; but it has been shown in laboratory expeiiments that, while crushed grass produced a bettei silage than unchopped material, the pH ofthe crushed silage was not always lowered to the level of 4-2 (DE MAN) (3). MARTIN and BUYSSE (4) in their experiments found that silage made from chopped lucerne had a lower pH and butyric-acid content and a higher lactic-acid content than that made from unchopped herbage.Even better silages have been obtained when the herbage was chopped with the addition of a carbohydrate-rich material. The 'Hardeland' method, where crushed beet is intimately mixed with chopped grass, has proved to be a reliable ensiling technique in Holland (KAPPELLE) (5).Wilting of the herbage before ensiling has been advocated in America, and results from experiments there show that, when the crop was ensiled at a dry-matter content of above 30 per cent, a good silage was produced (WOODWARD and SHEPHERD) (2). All the herbage was chopped before ensiling in these trials and the silage was under heavy pressure in the silos and, probably due to this, there was no difficulty in controlling the rise in temperature in the silage, even when the dry-matter content ofthe herbage was as high as 40 to 60 per cent. In small silos MARTIN and BUYSSE (4) found difficulty in preventing mould formation in wilted unchopjjed silage. It was also noted that the pH of wilted silage was higher than that made from herbage of a lower drymatter content, but in spite of this the butyric-acid content of the silage was low.In the trials to be described here the quality of silage made from lacerated, chopped and unchopped herbage has been compared. Wilting of the crop has also been tried, and the wilted herbage ensiled in a chopped and unchopped state. This was done with the object of comparing wilting as it would be done in Britain (ensiled unchopped) with the American method of the combined treatment of wilting and chopping. In addition, the value of adding molasses as the crop was chopped has been investigated. EXPERIMENTAL PROCEDURE The rate of fermentation in lacerated and chopped silageAs a preliminary to the main trials, a laboratory trial was conducted in 1952 to find the influence of laceration and chopping of herbage on the formation of acids in the silage. The herbage was predominantly a mixture of ryegrass, cocksfoot and clover, and when ensiled had a dry-matter content of 19 4 per cent and a crude-protein content of 16-5 per cent. The silage was sampled at intervals of 1, 2, 4, 7 and 14 days after ensiling, and the pH, lactic-acid and total volatile-acid content were determined on each...

SummaryIn a series of 3 trials there was little or no difference in milk yield when cows were fed the same quantity of dry matter in the form of well-preserved hay or silage from the same sward.A higher milk yield was obtained from silage made from grass at an early stage of maturity than from silage or hay made from the same crop 5 weeks later.In 2 trials when hay or silage was fed ad lib. the dry-matter intakes of the cows were higher with hay than with silage, and there was a consequent increase in milk yield and S.N.F. content in favour of hay.Some of the results indicated that with certain silages a depression in the S.N.F. content of the milk, due to a decrease in the casein content, could occur, although this was not associated with an inadequate energy intake.