The effect of quality and quantity of carbohydrate and protein in the ration of the sheep on the digestibility of cellulose and other constituents of the ration, with a note on the effect of adding vitamins of the B-complex on the digestibility and retention of the nutrients of a hay ration

Abstract

1. The effects of various starch and protein supplements on the digestibility of cellulose determined by the Norman-Jenkins technique and other constituents of the ration were studied in sheep.2. The addition of small amounts of maize or potato starch or flaked maize to a ration of about 1 lb. of poor hay was associated with a depression in the digestibility of (Norman-Jenkins) cellulose.3. When tested separately at varying levels, the addition of nearly pure maize protein, casein, white fishmeal, decorticated groundnut cake meal, urea or urea + DL-methionine, had no effect on the digestibility of cellulose, at any particular level of starch equivalent.4. The digestibility of nitrogenous nutrients was depressed by the addition of maize starch or flaked maize to the ration except when urea was the nitrogen supplement. The depression was even greater when potato starch was added to the ration instead of maize starch.5. The retention of nitrogen was not decreased by the addition of starch to the ration, although the digestibility of nitrogen-containing material was depressed. The retention was increased when starch was added to a ration containing casein.6. The retention of nitrogen was poor from rations containing urea and starch, but it was slightly improved by the supplementation with 1 g. DL-methionine per day.7. The addition of the various supplements had no marked effect on the digestibility of the dry matter or ‘other nutrients’ of the ration.8. It is suggested that the growth of the microorganisms digesting cellulose in the rumen is not dependent on the supplementary feed nitrogen when the substrate they are digesting contains a reasonable amount of nitrogen. This amount appears to be about 1%.9. The addition of vitamins of the B-complex to a daily ration of 1100 g. of hay did not affect the digestibility of the dry matter or nitrogencontaining substances or the retention of nitrogen by sheep.

Growth of lambs offered fixed amounts of roughage and concentrate either simultaneously or sequentially

“…These associative effects can be explained by the fact that MADF digestibility was reduced by the addition of concentrate to the diet (Table 2). Similar results have been obtained by numerous workers (Head 1953;Campling 1966;Vadiveloo & Holmes 1973;Mould 1982), although work carried out at the feed evaluation unit at the Rowett Research Institute (Wainman et al 1975(Wainman et al , 1978(Wainman et al , 1981(Wainman et al , 1984 has failed to substantiate these findings. These conflicting results can be explained by the fact that, in the Rowett work, diets were offered at the maintenance level of nutrition and associative effects are usually only apparent where diets are offered at rates above the energy requirement for maintenance.…”

Rearing of dairy cattle. 4. Effect of concentrate supplementation on the live-weight gain and feed intake of calves offered roughages ad libitum

“…If larger amounts of concentrates are offered as in this series of experiments in which concentrate dry-matter intakes accounted for 33 to 85% of total dry-matter intakes, voluntary intake of roughage is depressed (Stone et al, 1964;Campling and Murdoch, 1966). Supplementary soluble carbohydrates are known to depress the digestibility of crude fibre in the rumen (Hamilton, 1942;Head, 1953) owing to a reduction in the cellulolytic activity of the rumen micro-organisms (El-Shazly, Dehority and Johnson, 1961). As a result the rate of disappearance of roughage from the digestive tract is depressed (Eng, Riewe, Craig and Smith, 1964;Campling, 1966a) with a consequent reduction in the intake of roughage.…”

The effect of processing on digestion and utilization of cereals by ruminants

“…This effect has been thought to result from a reduction in rate of cellulose digestion as both Head (1953) and MacRae & Armstrong (1969) showed a reduction in cellulose digestibility. Studies by Mann & Orskov (1975) showed that lambs fed on whole barley had on average I x 106 viable cellulolytic bacteridml of rumen contents, while lambs given processed barley had only 5 x 1 0~.…”