Effects of Barley Grain Particle Size on Ruminal Fermentation and Carcass Characteristics of Male Lambs Fed High Urea Diet

Two experiments were conducted to evaluate effects of barley grains particle size on ruminal pH and am-monia concentration of rams (experiment 1) and carcass characteristics (experiment 2) of male lambs fed high urea diet. Treatments in two experiments were (1: basal diet + whole barley grains, 2: basal diet + ground barley grains with a 5 mm screen, 3: basal diet + ground barley grains with a 3 mm screen and 4: basal diet + ground barley grains with a 1 mm screen). Basal diet (on a dry matter (DM) basis) consisted of 365 g/kg corn silage, 10 g/kg limestone, 10 g/kg urea, 5 g/kg salt, 10 g/kg a vitamin-mineral premix and 600 g/kg of barley. In experiment 1, three 2-year old rams were fistulated for measuring ruminal pH and ruminal ammonia concentration. Ruminl pH was decreased by feeding ground barley grains through a 1 mm screen compared to feeding the whole barley grains (P<0.05). However, Ruminal ammonia concentra-tions were similar for all groups. In experiment 2, twenty four male lambs were used in a completely ran-domized design. Lambs were fed with the above mentioned diets for 90 days. Average daily gain, feed con-version ratio, average DM intake was significantly affected by treatments (P<0.05). Final body weight, cold carcass weight, dressing percentage, back fat thicknesses, carcass cuts (leg, shoulder, back and neck weights), internal organs (kidney, lungs, heart and gastrointestinal tract) weights were not significantly dif-ferent between diets (P>0.05). Lambs fed diet containing ground barley with 3 mm of screen had (P<0.05) higher longissimus muscle area compared to lambs fed whole barley grain. Consumption of whole barley grains increased DM intake and pelvic and abdominal fats. As a conclusion, the consumption of ground barley grain with a 3 mm or a 5 mm screen is suggested for feeding lambs fed high urea diet.