It has been known for many years that organic acids are produced by bacterial fermentation in the rumen. T h e importance of such fermentation in the nutrition of the ruminant has been adequately appreciated only recently, with the establishment of the relative proportions in which the acids are produced and the discovery of their role in ruminant metabolism.

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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...

1. Two Shorthorn cows with rumen fistulas were used to investigate the effect of diets high in concentrates and low in hay on the physical and biochemical processes of the reticulo-rumen.2. During the initial control period of the investigation the cows received daily 16 lb. hay and 20 lb. concentrates (flaked maize 50%, weatings 35%, decorticated ground-nut cake 15%) and during the final control period 18 lb. hay and 10 lb. concentrates. There were three intervening experimental periods, in each of which the cows received 2 lb. hay daily. In the first experimental period they received, in addition to the hay, 24 lb. concentrates; in the second, 20 lb. concentrates and 5 lb. of dried delignified straw pulp in a finely macerated form; and in the third, 20 lb. concentrates. The experiment lasted 27 weeks.3. In the experimental periods the mean milk-fat percentage remained below 2·0 for 10 weeks, whereas the mean value for the control periods was about 3·5. Addition of the straw pulp to the diet low in hay brought about no recovery in milk-fat percentage. It is calculated that in the two cows the losses in the yield of fat were 62·2 and 51·2% in the first experimental period and 62·5 and 58·7% in the second. In the experimental periods there were increases in the milk solids-not-fat percentage amounting in the two cows to upwards of 0·75 and 0·40 respectively. The composition of the butterfat was influenced by the diets low in hay, the main changes being a marked fall in the Reichert value, and a rise in the iodine value.4. Digestibility trials showed that in the initial control period and the first and second experimental periods the mean daily intake of digestible crudefibrewas 2·6,0·6 and 3·0 lb. respectively. A tentative estimate of the extent of digestion in the reticulo-rumen, based on the lignin-ratio method, showed that a marked depression in values for the digestibility of the cellulosic constituents of the diet given during the first experimental period took place in the reticulo-rumen. In all experimental periods, even the first, the digestion of starch in the reticulo-rumen was virtually complete, only traces passing undigested to the remainder of the gut. In these three periods the mean daily intake of ether extract remained at 0·4·0·5 lb.

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1. Three comparable groups of cows were used to investigate the effect, on milk composition and yield, of diets consisting of 4 lb. hay daily and concentrates containing 35% weatings, 15% decorticated groundnut cake and 50% of either flaked maize, maize meal or dredge corn (crushed oats and barley) respectively.2. During initial and final control periods all the cows received 16 lb. hay daily and, per 10 lb. of milk produced, they received about 4 lb. of the concentrate mixture containing flaked maize. During the experimental period of 6 weeks all the cows received 4 lb. hay, concentrates according to milk yield, and an extra 7 lb. of concentrates daily. One group of cows received the concentrate mixture containing flaked maize, a second group the mixture with maize meal and the third group that with dredge corn. The mean daily intakes of starch for the different groups were respectively 6·0, 6·4 and 5·8 lb. per cow.3. The diet containing flaked maize caused a marked, and that containing maize meal a small fall in the fat content of the milk, but the diet containing dredge corn was without effect. In the last 2 weeks of experimental treatment the adjusted mean fat percentage for the group of cows receiving flaked maize was 0·51 and 0·71 below the percentages for the groups receiving maize meal and dredge corn respectively. The yields of milk and of milk fat were also lower in the group receiving flaked maize than in either of the other groups, but the experimental treatments produced no changes in the milk solids-not-fat percentage.4. This experiment has shown that when diets low in hay and high in concentrates are given to lactating cows, the type of starch in the concentrates is of great importance in determining the extent of the depression in milk fat percentage. The greater depression with flaked maize than with maize meal or dredge corn is thought to be associated with the effect of the starch on the flora of the reticulo-rumen.

1. Twenty cows were used in an experiment to compare the effect of five different diets on the fat and solids-not-fat content and yield of milk.2. During initial and final control periods all the cows received 18 lb. hay daily and about 4 lb. of a balanced concentrate mixture (crude protein 16·5%) per 10 lb. of milk produced. In the experimental period, which lasted 7 weeks, a control group of four cows remained on this diet. Two similar groups received daily only 4 lb. hay and about 6 lb. extra concentrates; in these groups the concentrates contained 22·3% crude protein. The remaining two groups received similar treatment except that the concentrates contained only 11·6% crude protein. In addition, 10 1b. macerated delignified straw pulp (containing 1 lb. crude fibre) were given to half the cows receiving each type of concentrate. At the end of the experiment the cows were turned out to grass.3. With the diets low in hay and high in concentrates there was a fall in the fat content of the milk, with some variability in the response of individual cows (see 4 below). With the concentrates high in protein, the fall appeared to be rather slower than with those low in protein, but by the sixth and seventh weeks of experimental treatment it was estimated to be 0·67% fat with high and 0·72% fat with low protein concentrates. The experiment showed, therefore, that serious falls in fat content may occur in cows early in lactation with diets of 4 lb. hay and concentrates containing 22·3 or 11·6% protein. The addition of a limited amount of crude fibre as straw pulp brought about no recovery in milk fat content.4. The extent of the depression brought about by the change to diets low in hay diminished with advancing stage of lactation.