Effect of replacing cottonseed meal with canola meal on growth performance, blood metabolites, thyroid function, and ruminal parameters of growing lambs.

The objective was to clarify the impact of replacing cottonseed meal with canola meal (CM) on growth performance, blood metabolites, thyroxin function, and ruminal parameters of growing lambs. Twenty-four growing Barki male lambs (4-5 months of age) were assigned randomly into four equal groups (6 lambs each). Four dietary treatments were the control group with 0% CM (CON) and three experimental groups where CM replaced 25% (CN), 50% (CN), and 75% (CN) of cottonseed meal. There were no dietary effects (P > 0.05) on the lambs' feed intake, average daily gain, and feed conversion ratio of the lambs. The dietary CM linearly decreased the concentrations of serum total proteins (P = 0.003), albumin (P = 0.010), globulin (P = 0.011), AST (P = 0.041), and urea (P = 0.001) in growing lambs. The levels of ALT and creatinine, however, were not significantly affected by dietary treatments (P > 0.05). Furthermore, serum triiodothyronine, thyroxine, and electrolyte concentrations were similar (P > 0.05) in different dietary groups. Dietary treatments significantly affected the values of ruminal pH and ammonia at 0 h (P = 0.003 and 0.048, respectively) and 3 h (P = 0.033 and P = 0.006, respectively) postfeeding. The CN group showed significantly higher concentrations of ruminal ammonia at 0 and 3 h postfeeding. Furthermore, dietary CM (CN) significantly reduced the ruminal pH values at 0 and 3 h postfeeding. Meanwhile, dietary treatments did not affect the concentration of total VFAs in the ruminal fluid. In conclusion, CM can replace the cottonseed meal (up to 75%) in lamb diets without compromising their growth performance, thyroid function, and ruminal fermentation parameters.