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.
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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