Influence of different alfalfa:sorghum ratios in the diet of dairy goats on productivity and rumen turnover

Abstract

Four alfalfa:sorghum ratios in the diet were evaluated for changes in milk production and composition and rumen digesta turnover time of 12 mature rumen fistulated Nubian dairy goats, at 48 days postpartum. Animals were distributed according to a triplicated 4 × 4 Latin square design into four treatments of four alfalfa:sorghum ratios (80:20, 70:30, 60:40, and 50:50). These corresponded to four levels of NDF in the diet: 32%, 31%, 29%, and 28%. Rumen digesta turnover time was estimated by rumen emptying using lignin as an internal marker. No differences were found among alfalfa:sorghum ratios ( P > 0.10) for mean DM intake (1.5 ± 0.05 kg), crude protein (0.24 ± 0.04 kg), NDF (0.48 ± 0.01 kg) and cellulose (0.19 ± 0.005 kg). Mean milk production (1.16 ± 0.05 kg) and milk fat percentage (4.38 ± 0.13%) did not differ ( P > 0.05); however, 4% fat-corrected milk was slightly higher ( P < 0.06) in the group receiving the 60:40 alfalfa:sorghum ratio, corresponding to 29% NDF in the diet (1.31 kg vs. 1.20 kg, 1.10 kg, and 1.23 kg for ratios 80:20, 70:30 and 50:50, respectively). Average rumen digesta turnover time did not differ ( P > 0.10) among treatments (17.65 ± 1.85 h). Results suggest that productivity of dairy goats may be influenced by the forage:concentrate ratio offered, and probably by the NDF level of the diet.