Rapeseed meal and urea as a protein source for growing bulls on alkali-treated straw-based feeding

Abstract

Between the ages of 3 1/2 and 10 months, 12 bulls took part in an experiment in which 1) Tower rapeseed meal or 2) urea plus rapeseed meal was used as a protein source in a diet based on dry alkali-treated straw. In group 1 the rapeseed meal composed 32 % of a concentrate mixture also containing barley, oats, molassed beet pulp and minerals. The average daily consumption of rapeseed meal was 1.2 kg/animal and it contributed 58 % of the digestible crude protein supply. In group 2 urea composed 2 % of the concentrate mixture and the average daily consumption was 84 g/animal. In this group urea contributed about 38 % and rapeseed meal 20 % of the digestible crude protein supply. The palatability of the concentrate mixture was good in both groups. The average daily intake of alkalitreated straw was 2.3 kg/animal or 0.77 kg dry matter/100 live weight kg. Treated straw was the only roughage received by the animals from the age of6 months. Up to that age the animals also received hay, on average 840 g per animal and day. The average daily live weight gain in group 1 was 1072 g/animal and in group 2 it was 1111 g; the carcass weights in the respective groups were 169 kg and 176kg, and the feed conversion rates were 4.08 f.u. and 4.16 f.u./kg live weight gain. The differences between the group were not significant (P > 0.05). Almost all the animals showed pathological changes in their inner organs, which may mean that alkali-treated straw sounds not to be suitable as the only roughage source for growing bulls.