SummaryTwo experiments were conducted with eight rams in a latin-square design of four treatments with different lucerne hay (LH): maize grain (MG) ratios: 100:0, 80:20, 50:50 and 20:80. In Expt 1 the amount of food offered was restricted to 1 kg/day. In Expt 2 the rams were offered 1·5 kg/day, which was about the maximum amount the animals in the 100% LH treatment were able to consume. Animals were kept on each treatment for 4 weeks; during the final 8 days the faeces were oollected and weighed for each animal and analysed for dry matter, organic matter (OM), crude fibre and δCThe values of δC in LH, MG and different faeces samples were used for direct determination of LH and MG digestibilities of mixed diets in the different treatments.The increase of MG in the ration and the decrease of LH improved the digestibility of total OM. The effect of MG was more pronounced at the low than at the high level of consumption. At the low level of intake, an increase in the amount of MG in the ration did not affect the digestibility of LH, and MG digestibility was close to the extrapolated value. At a food intake level 1·5 times that of Expt 1, the addition of grain to more than 50 % of the ration caused a marked depression in digestibility of LH.Results of the δC method were discussed in comparison with calculated values of LH and MG digestibilities and with whole ration crude-fibre digestibility.
Sixty Israeli-Friesian cows were allocated, after calving, to five treatment groups of 12 cows per group according to the concentration and source of crude protein (CP) in the concentrate. Three groups received all their protein from plant sources: a basal control group (BP) was given concentrate containing 92 g CP per kg dry matter (DM), a medium-protein group (MP) was given a diet with soya-bean meal (SBM) added to give a CP concentration of 143 g/kg DM, and a high-protein group (HP) was given a diet with SBM added to give a concentration of 180 g/kg DM. Two groups were given the basal concentrate supplemented with urea (MU) or urea phosphate (MUP) up to approximately the same CP level as the MP group. The only roughage used was vetch-oats hay at a level of 350 g/kg total DM intake. The cows were given the experimental diets ad libitum throughout lactation.No difference was found between treatments in DM intake (kg/day), mean milk and fat-corrected milk (FCM; 40 g fat per kg) yields (kg/day), milk protein concentration, days from calving to conception or services per conception, during the entire lactation period. However, FCM yields during 60 days after calving were significantly higher for cows given the CP-supplemented diets than for the BP group. The FCM yield of the cows given the HP concentrate was higher than for those given the other concentrate mixtures only during the first 15 days after calving. Milk fat concentration was higher in cows given the BP and HP concentrates than in those given the MP ration, but only a trend in this respect was observed when part of the plant protein was replaced by urea or urea phosphate.The rate of body-weight loss after calving tended to increase with increase in amount of plant protein in the diet but was highest for the cows given the diets supplemented with non-protein nitrogen. Later in lactation, the body-weights of cows given the MP, HP and MUP diets increased immediately after they reached their lowest weight whilst cows given the BP and MU diets started gaining weight 165 and 120 days after calving, respectively.Rumen ammonia-N and blood urea-N concentrations (mg/1) for treatments BP, MP, HP, MU and MUP were: 56 and 101; 120 and 226; 143 and 269; 191 and 227; and 179 and 212, respectively. The relationship between rumen ammonia concentrations, blood urea concentrations and CP utilization for the different treatments is discussed. Supplying urea as urea phosphate tended to improve performance by an increase in annual milk and milk protein yields as well as in live-weight gain.
In an experiment with group-fed cattle from 6 months of age to slaughter at 480 kg live weight two levels of feed intake: 1, ad libitum, 2, 85 % of ad libitum amount, were combined with two ratios of concentrate to hay: a, 70 : 30; b, 30 : 70. In two further treatments, 3a and 3b, the cattle were fed diets a or b at 70 % of ad libitum from 6 to 10 months and ad libitum thereafter. Daily gain during the first 124 days of the experiment was (in grams) 1293, 983, 1097, 846, 992 and 756, and from the 125th day to slaughter 735, 600, 796, 579, 830 and 714, for treatments la, lb, 2a, 2b, 3a and 3b, respectively. The decline in rate of gain from the first period to the second was inversely related to the level of feed intake and to the percentage of concentrates in the ration in the first period. Daily carcass gain was 582, 393, 532, 350, 531 and 368 g for treatments la, lb, 2a, 2b, 3a and 3b, respectively. The treatments that were switched over from 70 % of ad libitum feed intake in the first period to 100 % in the second (3a and 3b), exhibited considerable compensatory growth in the second period, but this was not sufficient to be of economic advantage. The overall ME requirement per kg of live-weight gain was inversely related to rate of gain. Of the six treatments, 2a (85 % of ad libitum, 70% concentrate) was the most efficient (19-8 Mcal/kg live-weight gain). Animals on the 100 % level of feed intake throughout the experiment (treatments la, lb) were significantly fatter than those on the other treatments.
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