Effects of different carbohydrate sources on the performance, ruminal and blood metabolites and nutrients digestibility in fattening male-lambs fed corn steep liquor

The current experiment was conducted to evaluate the effects of replacing dietary corn/barley mixture with molasses, a ruminal fermentable carbohydrate source, at 0, 50 and 100 g/kg dietary dry matter (DM) in the diet of fattening lambs containing corn steep liquor (CSL, 130 g/kg DM), a ruminal degradable protein source. Twenty-four male Lori lambs (average body weight of 27.7±3.41 kg; 120.0±7.5 days of age) were randomly assigned into three groups of eight lambs each in a balanced completely randomized design. Results indicated that supplementing dietary CSL with increasing levels of molasses up to 100 g/kg DM linearly increased the digestibility of organic matter and ash-free neutral detergent fiber (P<0.05). Increasing the level of molasses in the CSL containing diets had no effect on ruminal pH (P>0.05), but linearly decreased rumen concentration of NH 3-N (P<0.05). Except for total volatile fatty acids (VFAs) and molar proportion of butyrate which were increased linearly with increasing dietary molasses level, other VFAs were not influenced by the experimental diets. Increasing the level of molasses in the diet up to 100 g/kg DM linearly increased plasma total protein concentration while linearly reduced blood urea nitrogen concentration. Total weight gain and average daily gain were improved but feed conversion ratio decreased linearly with increasing dietary level of molasses. In conclusion, supplementing CSL with molasses at the level of 100 g/kg dietary DM increased the nutrient digestibility and performance of fattening lambs.