Associative effect of molasses-urea block and forage quality on nutrient digestion and nitrogen retention in sheep

An experiment was conducted in a 4x4 Latin square design involving four adult crossbred (Kaghani x Rambouillet) wethers. The wethers were kept in individual metabolic crates and were fed tour experimental diets viz. chopped maize stovers (Diet A), chopped maize stovers with 150 g/d molasses-urea block (Diet B), "chopped lucerne hay (Diet C) and chopped lucerne hay with 150 g/d molasses urea block (Diet D). The daily intake of the basal diet was restricted to 2% of body weight. Total dry matter intake was significantly affected by the diets (P less than 0.001). Total DMI on molasses-urea block (MUB) supplemented diets (Diets B and D) remained the same (893.75 and 904.00 g/d, respectively) but was higher (P less than 0.05) than diets A and C. Daily water consumption significantly varied (P less than 0.001) due to diet composition and was higher on diets containing MUB or lucerne hay. Diets containing lucerne hay had greater (P less than 0.05) dry matter digestibility (DMD) and organic matter digestibility (OMD) than those containing maize stovers. Supplementation of MUB to maize stovers or lucerne hay did not affect the digestibility in the wethers. However, the nitrogen digestibility (ND) significantly responded (P less than 0.01) to forage quality and MUB supplementation. Nitrogen retention (g/d) in the body of the animals responded (P less than 0.001) to diet composition. The wethers receiving lucerne hay-based diets retained more nitrogen (P less than 0.001) than those given maize stovers (8.50 vs 3.12 g/d). Similarly MUB supplementation on both forages increased (P less than 0.05) the N retention in the animals. Mean nitrogen retention was 1.82, 4.41, 7.19 and 9.82 g/d in wethers receiving diets A, B, C and D, respectively. Rumen ammonia concentration was also affected by both diet composition (P less than 0.05) and sampling time (P less than 0.05). In wethers receiving maize stovers, the mean rumen ammonia concentration (mg N/100 ml) was 10.52 which increased (P less than 0.05) to 17.87 in response to MUB supplementation. On lucerne hay, MUB feeding did not change ammonia concentration in the rumen and were 24.24 and 29.88 mg N/100 ml on diets C and D, respectively. Ammonia concentration was higher (P less than 0.05) in the samples of rumen fluid collected 2 hours after feeding than those collected before feeding. It is conducted that MUB supplementation did not affect in vivo dry matter or organic matter digestibility of the diets, but was effective in supporting higher nitrogen retention in tire wethers fed either maize stovers or lucerne hay. Diet based can lucerne hay were more digestible and caused higher nitrogen retention in wethers than those fed maize stovers. Feeding of MUB increased the demand of the wethers for drinking water. Molasses-urea block-as a strategic feed supplement may also serve as a carrier for rumen modifiers, growth promoters and therapeutic agents which warrant further investigations.