677. The effect of variations in nutrient intake upon the yield and composition of milk: I. Variations in the amount and type of concentrates fed in winter rations

Abstract

1. A series of five experiments on the effects of variation in the concentrate ration of cows receiving normal diets of hay and grass silage are described.2. Responses in milk yield to the feeding of additional concentrates occurred in all five experiments and were statistically significant in three of them.3. Mean responses in four experiments with adequate statistical control ranged from 0·7 to 1·0 lb. milk/lb. additional S.E. at levels of feeding from 90 to 120% of the Woodman standard, and were not economic at prices ruling during the winter of 1955–56.4. There were indications that the responses varied with the yield of the cow, and in two experiments there was clear evidence that the response to a second addition of 20% in the production ration was approximately half of that to the first.5. The response to additional S.E. was appreciably reduced when normal protein standards were not maintained in the additional concentrates.6. A limited substitution of hay for concentrates, which did not alter S.E. intakes appreciably, had no appreciable effect on milk yield.7. Significant responses of solids-not-fat percentage to the feeding of concentrates above the normal standards occurred in two experiments, but not in two others where the control percentages were lower. The importance of factors other than energy intake in influencing this quantity was emphasized.

678. The effect of variations in nutrient intake upon the yield and composition of milk II. Factors affecting rate of eating roughage and responses to an increase in the amount of concentrates fed

“…additional s.E.) upon milk yield (lb./day) was + 0-035 ± 0-04 which is in very close agreement with the value previously reported (23). The predicted response ranged from 0-6 lb.…”

“…The response to a standard amount of additional concentrates was significantly and positively related to milk yield, and there were no independent effects due to stage of lactation. These observations confirm the results of a previous analysis of a series of conventional feeding experiments (23), and the regressions contrast with the results of Jensen et a£. (15) who reported that responses to increased feeding were very similar in 'good' and 'poor' producing cows when the comparison was made at the same percentage of the Haecker production standards for total digestible nutrients.…”

The effect of the plane of energy nutrition of the cow on the secretion in milk of the constituents of the solids-not-fat fraction and on the concentrations of certain blood-plasma constituents

“…The effect of the plane of energy nutrition of the cow on the S.N.F. content of milk, as demonstrated in this and earlier work (Burt, 19573;Dijkstra, 1942;Holmes, Reid, MacLusky, Waite & Watson, 1957;Rook, 1953;Rowland, 1946), is represented in Fig. 3.…”

Some factors affecting voluntary food intake in buffaloes. 3. Effect of concentrate feeding on intake of roughages fed to lactating buffaloes

“…Concentrate feeding to buffaloes receiving maize silage ad libitum resulted in a significant increase in milk yield which could be explained on the basis of increased intake of D.M. and TDN (Jensen et al 1942;Burt, 1957;Laird & Walker-Love, 1962;Jackson & Gupta, 1971). The SNF content of milk was higher for animals on supplemented rations which is understandable in view of the higher plane of nutrition consequent upon supplementary feeding (Rook, 1961;Huber & Bowman, 1966).…”