THE EFFECT OF MAIZE GRAIN SUPPLEMENTATION OF DIETS BASED ON WHEAT STRAW AND POULTRY LITTER ON THEIR UTILIZATION BY BEEF-CATTLE

Six diets were formulated in a factorial design of three poultry litter levels ( 15. 30 and 45% on a dry matter (DM) basis: low (L), medium (M) and high (H). respectively), and two maize grain levels (0 and 20% on DM basis: - and +, respectively). The rest of the ration in all diets was wheat straw. The in vivo digestibility of DM components, nitrogen balance and digesta mean retention time of these diets were tested on 1 5 beef intact male calves (initial weight 150 kg). They were allocated (five animals per diet) in individual digestion stalls to diets L-, M-, and H- for a first experimental period, and then to L+, M+ and H+ for a second period, in which each calf had the same poultry titter level as in the first period. Daily DM intake of diets L-, M-, H- was 2.04, 2.19 and 1.79 kg, and of diets L+, M+, H+ was 3.07, 3.37 and 3.16 kg, respectively. The respective digestibility coefficients of organic matter were 50.5, 56.4, 54.3 and 6 1.3, 61.8, 66.7%, and nitrogen retention was -8.47, -4.04, -9.80 and 8.41, 18.87, 14.21 g day-1. The replacement of 20% of the diet by maize grain almost doubled the digestible intake ( 14.8, 17. 1, 13.2 MJ day-1 in diets L-, M-, H- and 29.2, 31.0, 30.8 MJ day-1 in diets L+, M+, H+, respectively). The mean retention time of fibres in the gastrointestinal tract and in the rumen was inversely related to the proportion of poultry litter in the diet, while the mean retention time of fluid was not affected.