The Effects of Dietary Crude Protein Levels on Nutrient Digestibility, Nitrogen Retention, Rumen Environment and Microbial Nitrogen Synthesis of Growing Female Bach Thao Goats in Vietnam

An experiment was carried out to evaluate the effects of crude protein (CP) contents on feed intake, nutrient digestibility, rumen parameters and estimated nitrogen synthesis of Bach Thao goats. Five female goats from 4-5 months of age (16.7±0.92 kg) were used for this experiment in a Latin square design. Five treatments were applied, containing dietary CP contents of 5.0, 5.5, 6.0, 6.5 or 7.0 g/kgLW/day. The results showed that dry matter (DM), Neutral detergent fiber (NDF) and acid detergent fiber (ADF) intakes and digestibilities were not significantly different among the treatments (P > 0.05), and the rumen parameters were also similar in different treatments. However, the nitrogen retention was significantly different (P < 0.05) among the treatments and it was higher for the treatments of 6.0, 6.5 and 7.0 gCP/kgLW. The purine derivatives and estimated microbial nitrogen synthesis were numerically higher for the treatments containing 6.0, 6.5 and 7.0 gCP/kgLW. Although there was a gradual increase of daily weight gain by increasing the amount of dietary CP from 5.0 to 7.0 gCP, no significant difference was found. Based on the results, the dietary CP from 6.0 to 6.5 g/kgLW for growing Bach Thao goats is recommended.