Effects of walnut shell and chicken manure biochar on in vitro fermentation and in vivo nutrient digestibility and performance of dairy ewes

Two experiments were conducted to investigate the effects of addition of walnut shell biochar (WSB) and chicken manure biochar (CMB) to dairy ewes’ diet. In in vitro experiment, the effects of different levels of WSB and CMB (0.5, 1, and 1.5% diet dry matter (DM)) on rumen fermentation characteristics were assessed in a completely randomized design with seven treatments and three replicates. Treatments were as follows: basal diet without biochar (control), basal diet with 0.5, 1, and 1.5% WSB, and basal diet with 0.5, 1, and 1.5% CMB. Addition of 1% WSB and 1.5% CMB to the diet linearly decreased methane production and ammonia-N concentrations and increased pH compared to control (P < 0.001). Inclusion of WSB and CMB to the diet did not change volume of gas production and total volatile fatty acids (VFA) and proportion of acetate, propionate, and butyrate. In the second experiment, six milking Kermanian ewes were used in a replicated Latin square design with three treatments and three 21-day periods to evaluate the effects of 1% WSB and 1.5% CMB (based on results obtained from in vitro trial) on intake, digestibility, and milk yield and composition. Dietary inclusion of 1% WSB and 1.5% CMB resulted in more milk yield (P < 0.01), milk protein (P < 0.05), and solids not fat (SNF) (P < 0.001). Blood glucose and total protein increased (P < 0.01) in ewes fed 1% WSB and 1.5% CMB in comparison to ewes fed control diet. Apparent digestibility coefficients of DM (P < 0.01) and OM (P < 0.10) were increased with inclusion of 1% WSB and 1.5% CMB in diet. Neutral detergent fiber (NDF) digestibility was also increased in WSB-fed ewes (P < 0.01). The lack of negative effects of 1% WSB and 1.5% CMB coupled with the observed reduction in methane emission and ammonia concentration and also improvement in milk production suggested that biochars can be beneficially incorporated in dairy ewes’ ration as a low-cost feed additive.