Effect of Concentrate Mix Supplementation to Urea-Treated and Ensiled Maize Stover on Feed Intake, Digestibility and Nitrogen Balance of Hararghe Highland Sheep

Abstract

The effects of feeding different levels of concentrate mixture to sheep fed urea treated maize stover basal diet on feed intake, digestibility, and nitrogen balance were evaluated at Haramaya University. The experiment was conducted in a randomized complete block design using twenty male Hararghe Highland sheep with a mean initial body weight (BW) of 17.2 ± 1.74 (mean ± SD) kg. The animals were grouped into five blocks based on their initial BW and randomly assigned to four treatments within the block. The levels of supplementation were 0 g (control, T1), 150 g (low, T2), 250 g (medium, T3) and 350 g (high, T4) of the concentrate mix prepared from brewers dried grain, peanut cake and wheat bran at a ratio of 1:1:3 on dry matter basis, respectively. Hundred kg (dry matter basis) of chopped maize stover was treated with 4 kg of urea dissolved in 100 liters of water and ensiled for 21 days before used as a basal diet. The urea treated maize stover (UTMS) was offered ad libitum and water and mineral block were available to the experimental animals all the time throughout the experiment. Intake trial was conducted for 90 days. Digestibility and nitrogen balance trials were carried out for 7 days following 3 days of adaptation to the metabolic cage and carrying of the fecal collection bag following 15 days of adaptation. Urea treatment improved the crude protein (CP) content of maize stover by about 33% (from 5.8 to 7.7%). The UTMS intake was lower (P < 0.05) for the sheep in T4 (665 ± 16 g DM day-1) than in T1 (768 ± 16 g DM day-1) and T3 (754 ± 16 g DM day-1). Daily DM intake per kg W0.75 was higher (P < 0.01) for T3 (105.7 ± 1.7 g day-1) and T4 (104.1 ± 1.7 g day-1) than T1 (91.9 ± 1.7 g day-1). Total CP intake per kg W0.75 (7.8, 10.4, 12.7, and 13.8 (SEM = ± 0.16), for T1, T2, T3, and T4, respectively) increased with increasing level of  supplementation (P < 0.01). Crude protein digestibility was lower (P < 0.05) in non-supplemented sheep (0.42 ± 0.04) than the supplemented sheep (0.65, 0.71, and 0.70 (SEM = ± 0.04) for T2, T3 and T4,  respectively). Nitrogen intake during digestibility trial (6.4, 11.2, 14.4, and 17.5 (SEM = ± 0.3) g day-1 for T1, T2, T3 and T4, respectively) increased with increasing levels of supplementation (P < 0.001). Nitrogen retention was positive and higher in the supplemented groups (8.2, 7, and 4.4 (SEM = ± 0.63) for T4, T3, and T2, respectively) than in T1 (-0.02 ± 0.63 g day-1), which has a negative nitrogen balance (P < 0.01). The result indicated that supplementation improved feed intake, digestibility and nitrogen balance, but feeding sole urea treated maize stover failed to support sufficient nitrogen intake which might have resulted in body reserve mobilization to meet the maintenance requirement of the animal.

Keywords: Concentrate Mix; Digestibility; Hararghe Highland Sheep; Maize stover; Nitrogen Balance; Urea Treatment