Growth, feed conversion efficiency and carcass composition of Arabian fat-tailed lambs fed diets with different proportions of a cardboard-based protein-enriched fermented feed

Twenty fat-tailed ram lambs of the Naeemi breed in Kuwait were offered four diets (5 lambs/diet) containing cardboard-based protein-enriched fermented feed (PEFF) and concentrates in ratios of 0:100 (control), 25:75 (PEFF25), 50:50 (PEFF50) and 75:25 (PEFF75) together with 200 g lucerne hay in order to determine the ability of PEFF to replace cereals in the diet. The PEFF was produced by treating cardboard boxes with Phanerochaete chrysosporium and Pleurotus ostreatus fungi which increased the crude protein (CP) content of the cardboard from 7 to 96 g/kg dry matter (DM). The average CP concentration of the diets fed was 162 g/kg. Average daily feed intake (ADFI), average dry matter intake (DMI), average daily gain (ADG) and feed conversion (i.e., FC = kg feed/kg gain), dressing percentage, carcass side weight (half-carcass), and weights of subcutaneous fat, muscle and bone were measured. ADG and FC were 279 g and 5.1, 224 g and 6.7, 146 g and 7.7, and 83 g and 11.3 for the control, PEFF25, PEFF50 and PEFF75 diets, respectively. Dressing percentage, adjusted for age, was 422, 437, 414 and 399 g/kg liveweight for the lambs fed the above diets, respectively. The difference between the PEFF25 and PEFF75 diets was significant. Side weights were similar for the control and PEFF25 diets at 12.1 and 11.0 kg, respectively, but significantly lower for the PEFF50 (8.5 kg) and PEFF75 diets (6.8 kg). When calculated on a constant side weight basis (g/kg side weight), lambs fed the PEFF25 diet were 75 g lower in subcutaneous fat, 68 g more in muscle and the same amount of bone as the control lambs. Increasing the proportion of PEFF in the diet from 250 to 750 g/kg feed, did not change the proportion of lean in the lamb carcasses. Lambs fed PEFF50 or PEFF75 diet had a significantly greater proportion of bone in their carcasses compared to the lambs offered the control or PEFF25 diet. The study indicates that PEFF could replace 250 g/kg of the conventional dietary ingredients in diets for growing lambs.