Abstract
The nutritive value of rumen contents and barley mixture (4:1 w/w; RCB) was evaluated and the effect of their feeding on growth performances in Najdi lambs was studied. A metabolism trial was conducted with 16 rams divided into four dietary groups. The diets were: a whole-mixed control diet and three diets where RCB was incorporated at the rates of 25, 50 and 100%, replacing an equal amount of control diet. The results showed that there was a depression (p<0.05) in DM digestibility for the 100% RCB diet in comparison with other diets. The digestibility of CP was higher (p<0.05) for the 25% RCB diet as compared to the control diet; there was a trend for a small (p>0.05) decrease in digestibility as level of RCB increased. Lambs in all studied diets were in positive nitrogen balance; the differences between diets were not significant. A total of 45 lambs were allotted into three groups and used to evaluate the effect of dietary inclusion of RCB (0, 25 and 50%) on growth performance and carcass traits. Daily DM intake, final body weight, carcass weight and dressing percentage were not different among treatments. Average weight gain and ether extract (EE) in 9-11th rib joint were higher (p<0.05) in lambs fed control diet than those fed RCB diets. The substitution of RCB for 50% of control diet exhibited 11.8% reduction in feeding cost for each kg of body weight gain.