Experiments on the nutrition of the dairy heifer: I. Protein requirements of yearling stock

Abstract

The literature on the protein requirements of young dairy heifers has been discussed and the wide variations noted, both in quantities estimated for particular live-weight ranges and in the suggested trends of requirements with live weight.Short-term trials have been conducted in which the effect of variation in protein intake on rate of live-weight gain of dairy heifers of various ages was studied.The response to increments of protein in the ration was found to be curvilinear with a rapid decline in response above critical levels of intake. This level varied with the live weight of the animal, being 0·8 lb. crude protein at 300 lb. live weight and 1·0 lb. at 400 and 500 lb. when rations based on hay, decorticated ground-nut meal and flaked maize were fed.These levels are somewhat lower than estimates of protein requirements quoted in the literature, though the trend indicated in them agrees with some of the published data.No marked difference was observed between the values of decorticated ground-nut meal and white fish meal as protein supplements. Urea was inferior to decorticated ground-nut meal.The overall depressant effect of straw on rate of live-weight gain is demonstrated and discussed.

Experiments on the nutrition of the dairy heifer: VII. Observations on the effect of the energy intake on the utilization of protein in growth and in lactation

“…The results are summarized in Table 3 and the analyses of the feeds used are given in Table 2. Bailey & Broster (1957) examined the response to protein by yearling heifers over a wide range of intakes from deficiency to excess. The response to protein at low levels of intake was measured with 2 year old heifers by .…”

“…T~NTR O'DTTrTTO'N' similar result with pregnant heifers. These observations suggest that energy intake orientates the In earlier experiments (Bailey & Broster, 1957; response curve to protein relative to absolute rate of Broster, Tuck & Balch, 1963) we examined the live-weight gain. variation in the rate of live-weight gain of heifers Few of the published experiments on levels of given different amounts of protein in rations calcu-feeding for dairy cows have dealt with the question lated to be isocaloric.…”

Experiments on the nutrition of the dairy heifer: V. Nutrition in late pregnancy

“…The voluntary intake of hay was not high in the present trials. In a number of experiments (Bailey & Broster, 1957;Bartlett & Broster, 1958) the mean daily voluntary intake of yearling heifers was 2-0 Ib. hay/100 Ib.…”

“…Experiments on the protein requirements of yearling and two-year-old maiden heifers have been reported in two earlier papers in this series (Bailey & Broster, 1957;Broster, Tuck & Balch, 1963). The experiment now to be reported deals with the protein and energy requirements for growth of dairy heifers in late pregnancy.…”

The effect of the addition of large amounts of cod-liver oil to the rations of yearling heifers on their rate of live-weight gain

“…3 and the concentrates ration was increased by 2 lb/day. The ratio of cereal to decorticated groundnut meal was so arranged that in each experiment all treatment groups received the same level of protein; previous experiments suggest that in all the diets protein intake exceeded minimum requirements (Bailey & Broster, 1957). In addition to the ration of concentrates animals were given hay at the rate of 1-8 lb./lOO lb.…”