Rumen Fermentation and Microbial Nitrogen Supply in Native Sheep Fed Crop Residue based Densified Feed Blocks Varying in Particle Size of Roughage

Abstract

Background: Roughages with an appropriate particle size are required to maintain the optimum rumen health, fermentation and nutrient digestibility. In this regard, the present study was conducted in sheep to determine the optimum particle size for preparation of complete feed blocks. Methods: Twenty-one adult Deccani rams (19.45±0.80 kg) of 2-3 yrs age were used in a complete randomized design to assess the effect of particle size (PS) of sorghum stover (SS) on rumen fermentation characteristics and microbial nitrogen supply. Rams were divided into 3 groups consisting of 7 animals each and fed complete feed blocks containing 8 mm (SSCFB-8), 12 mm (SSCFB-12) and 16 mm (SSCFB-16) particle sizes of the stover. Rumen liquor was collected using stomach tube from each animal at 0, 2, 4 and 6 h after feeding to assess rumen fermentation pattern. Result: Mean rumen pH was increased (P less than 0.001) with increased PS of the SS in the CFBs and the rams fed SSCFB-12 and SSCFB-16 diets were shown highest (P less than 0.001) pH values. Average ammonia nitrogen concentrations were lower (P less than 0.01) in rams fed SSCFB-16 diet compared to those fed SSCFB-12 or SSCFB-8 diets. The average total volatile fatty acid (TVFA) concentration was decreased with increase in PS of SS in the feed blocks. The rams fed SSCFB-8 diet had shown higher (P less than 0.05) TVFA mean values than those fed SSCFB-12 or SSCFB-16 diets. Microbialnitrogen (g/day, g/kg W0.75) and protein supply (g/day, g/kg W0.75 and g/kg DOMI) was not affected by the PS of sorghum stover in complete feed blocks.Based on the results of the current study the SS ground to 8 mm can be considered as optimum for sheep fed SS based diets.