The nutritional quality of a fresh orange pulp-wheat straw mixture ensiled with either sugar beet pulp, wheat bran, or urea compared to corn silage (Zea mays) in sheep

Abstract

Abstract This study compares corn silage (CS) with an orange pulp-wheat straw mixture (OW) ensiled with either sugar beet pulp (SBP), wheat bran (WB), or urea in terms of intake, chemical composition, phenolic compounds, silage fermentation characteristics, digestibility, in vivo rumen variables and biochemical blood variables in 48 Shall male sheep, and in vitro methane (CH4) production. In addition to CS, five other silages: OW (i.e., 87.5% fresh orange pulp + 12.5% wheat straw); OWU (OW + 1% urea); OWS (87.5% fresh orange pulp + 8.6% wheat straw + 3.9% SBP); OWSU (87.5% fresh orange pulp + 8.6% wheat straw + 1% urea + 3.9% SBP); and OWB (87.5% fresh orange pulp + 8.6% wheat straw + 3.9% SBP) were ensiled for 90 days. All diets, which contained a mineral-vitamin premix (10 g/kg of dry matter [DM]), were each randomly assigned to five sheep (live weight 40 ± 2.5 kg) using a completely randomized design, and the SAS software MIXED method was used for data analysis. Among all silages, OWU and OWSU had the highest (P < 0.01) ammonia-N concentration, but there were no differences in other fermentation characteristics. Animals fed on the CS diet had higher DM intake (P = 0.01) and DM (P = 0.01), organic matter (P = 0.01), and neutral detergent fiber (P = 0.02) digestibilities compared with other diets. However, sheep receiving OWU and OWSU diets had higher (P < 0.01) crude protein digestibility than those fed on other diets. The OWU and OWSU-fed sheep had the highest (P = 0.04) ruminal ammonia-N concentration. Sheep fed on CS had higher (P = 0.03) ruminal total short-chain fatty acids, acetate concentration (P = 0.02), total protozoa (P < 0.01), and cellulolytic bacteria numbers (P < 0.01), but had a lower (P = 0.03) propionate concentration compared with the other sheep. In vitro CH4 production was higher (P = 0.01) with the CS diet compared to the orange pulp diets. Estimated microbial protein supply was lower (P = 0.05) with CS compared to all orange silages. In conclusion, the variation in the nutritive quality among the OWS, OWSU, and OWB is relatively small, and the OWB, which is most comparable to CS, was judged to be nutritionally the best among the diets.