Four diets containing 9-6 MJ metabolizable energy (ME) per kg dry matter (DM) (LMEC), and four diets containing 11-3 MJ/kg DM (HMEC) were formulated. One diet of each ME concentration contained 90 g crude protein (CP) per kg DM and served as a negative control (NC). In the three other diets of each ME concentration, the level of CP was raised to 140 g/kg DM by inclusion of poultry litter (PL), non-protein nitrogen (NPN) or fish meal (FM). These diets were examined in a digestion and N balance trial and in a feeding trial.For the NC, PL, NPN and FM subtreatments of the LMEC diets, DM intakes were 107-1, 112-4, 100-6 and 130-2 g/kg M 075 respectively; digestibility coefficients of organic matter (OM) were 0-64, 0-70, 0-67 and 0-71 respectively; and N retention 0-40, 0-76, 0-53 and 1-21 g/kg M 075 respectively. For the respective subtreatments of the HMEC diets, the values were: 100-4, 119-4, 109-3, 107-5 for DM intake; 0-64, 0-73, 0-73, 0-73 for digestibility coefficients of OM and 0-40, 0-87, 1-06 and 1-03 g/kg M 075 for N retention.Daily gain on the respective diets in the first 130 days of the feeding trial was 0-85, 0-90, 0-91, 1-04 kg for the LMEC and 1-09, 1-21, 119, 1-24 kg for the HMEC diets, and from the 131st day to slaughter was 0-98, 1-02, 100, 1-08 kg for the LMEC and 1-03, 1-02, 1-07, 1-05 kg for the HMEC diets respectively. Daily carcass gain was 0-49, 0-51, 0-51, 0-53 kg for the LMEC and 0-55, 0-59, 0-59, 0-60 kg for the HMEC diets, respectively.The relationship between ME concentration in the diet and source of CP is discussed.

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Link to this article: http://journals.cambridge.org/abstract_S0003356100002592How to cite this article: D. Levy, Z. Holzer, V. Samuel and I. Bruckental (1986). The effect of source of nitrogen and level of its supplementation on the performance of growing-fattening bulls. ABSTRACTTwo feeding trails were made and in both all the diets given contained about 11 MJ metabolizable energy (ME) per kg dry matter (DM).In trial 1, diets containing three concentrations of crude protein (CP) were given to a total of 84 Friesian bulls in each of three stages of growth. They were, in stage 1 (150 to 250 kg live weight) 130, 145 and 160 g CP per kg dietary DM; in stage 2 (250 to 350 kg live weight) 110, 130 and 145 g CP per kg dietary DM; in stage 3 (350 kg to slaughter) 95, 110 and 130 g CP per kg dietary DM. In stages 2 and 3, the source of supplementary nitrogen at each CP concentration was either soya-bean meal or non-protein nitrogen (NPN) giving six combinations of concentration and source of dietary CP. Liveweight gains in stage 1 were 1-52, 1-60 and 1-58 kg/day respectively (P > 005). In the stages involving both concentrations and source of nitrogen (soya-bean meal in parentheses), the mean daily live-weight gains were (06) and 1-08 kg for stage 3 (P < 005), for the diets of 130, 145 and 160 g CP per kg diet respectively.Trial 2 consisted of six stages of growth, the first five of 45 days duration and the sixth of varying length up to a predicted slaughter weight, and seven dietary treatments. Treatment 1 was a negative control (NC) with a dietary CP concentration of 90 g/kg DM. For the other six treatments two concentrations of dietary CP were given; 120 g/kg and 140 g/kg in stages 1 and 2 and 100 g/kg or 120 g/kg in stages 3 to 6. Dietary CP concentration was increased by the addition of NPN, fish meal or soya-bean meal. A total of 98 Friesian bulls were used with an initial average live weight of 185 kg. Daily gain of the NC group in the six stages of the trial was 0-86, 0-97, 101, 1-13, 1-07 and 1-00 kg for stages 1 to 6 respectively. From the results it was concluded that feeding NPN is not efficient at live weights lower than 250 kg and that there is no advantage to feeding fish meal over soya-bean meal in diets of medium energy concentration at live weights heavier than 250 kg.

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Four groups of 12 beef heifers were each given either straw treated with 35 g sodium hydroxide per kg (TS) or untreated straw (US) and were either supplemented with 35 mg monensin per kg (Ms) or not supplemented (Ns). The diet consisted of approximately 0-40 of a concentrate mixture that contained 12-8 MJ metabolizable energy and 243 g crude protein per kg dry matter, and 0-60 straw. Feeding was ad libitum. The average initial weight of the heifers was 207-2 kg and the experiment lasted 86 days.The average dry matter consumed was 2-3g/kg live weight. Average daily gain ( + s.e.) was 505 + 31-6, 371+33-8, 380 + 26-2 and 257±32-7g/day for treatment groups TS-Ms, TS-Ns, US-Ms and US-Ns, respectively. These findings indicate that monensin may counteract some ill-effects of diets high in sodium hydroxide-treated straw and thus further research is warranted.