Probiotic-inoculated biochar as a feed additive for dairy sheep: Effect on apparent digestibility, microbial protein supply, methane emissions and productive performance

Two experiments were performed to investigate the effect of feeding probiotic-inoculated biochar on nutrient digestibility, microbial protein supply, methane emissions and productive performance in dairy sheep. The first trial consisted of a cross over design with two 24-day periods in respiratory chambers. The initial 14 days of each period were for dietary adaptation and the subsequent 10 days served for measurement of dry matter (DM) intake, apparent digestibility, microbial protein supply and CH₄ production. Six dry non pregnant Latxa sheep were used. All sheep were fed a grass hay and a concentrate (hay to concentrate ratio 70:30) containing 0 (CTR, n = 3) or 50 (BIO, n = 3) g biochar/ kg of concentrate DM. Biochar was inoculated with probiotics (Lactobacillus casei, Lactobacillus plantarum and Saccharomyces cerevisiae). Sheep fed inoculated biochar showed similar DM intake but increased apparent digestibility of DM (P = 0.014) and neutral detergent fibre (P = 0.003) compared to CTR-fed sheep. Inoculated biochar increased total purine derivatives excretion (P = 0.009) and microbial N supply (P = 0.008) and tended to increase the efficiency of microbial protein supply (P = 0.061). Daily net CH₄ production was increased by 11 % (P = 0.003) and CH₄ production per kg of digested DM was reduced by 9 % (P = 0.003) in inoculated biochar group compared to CTR. In the second trial, twenty-four multiparous Latxa ewes were used to examine the effect of feeding the same treatments on ewe productive performance and CH₄ production. All sheep were offered grass hay ad libitum, and the concentrates were the same as those described in the first trial. The experimental period extended for 45 days, with the initial 7 days allocated for covariate determination, the subsequent 13 days for diet adaptation, and the remaining 25 days for measurements of DM intake, milk production and composition and CH₄ production. Feeding inoculated biochar had no effect on daily DM intake, daily milk yield or feed conversion efficiency (P > 0.1). Sheep fed inoculated biochar showed similar content of crude protein (P = 0.108) and lactose (P = 0.741) in milk, but higher milk fat content (P < 0.001) compared to CTR. Daily net CH₄ production was 11 % higher in inoculated biochar fed animals than in CTR group (P = 0.049). In conclusion, probiotic-inoculated biochar increased apparent digestibility of dietary DM and improved microbial protein supply and milk fat content, without impacting milk yield. Feeding inoculated biochar had no favorable impact on daily net CH₄ production, but reduced enteric CH₄ production per kg of digested DM.