Effects of walnut shell biochar feed additive on rumen fermentation, nutrient utilization, and performance in fattening lambs

Converting agricultural waste into biochar offers a promising approach to improve animal nutrition and mitigate environmental impacts. This study investigated the effects of dietary supplementation with walnut shell-derived biochar on growth performance, nutrient digestibility, and rumen fermentation characteristics in fattening male lambs. Twelve lambs (initial body weight: 34.4 kg) were randomly assigned to two dietary treatments: a control diet and a diet supplemented with 1 % walnut shell biochar, over a period of 60 days. The inclusion of 1 % walnut shell biochar did not significantly affect dry matter intake (DMI) (p = 0.08), average daily gain (ADG) (p = 0.06), or feed conversion ratio (FCR) (p = 0.47). However, lambs fed the walnut shell biochar diet had a higher final body weight compared to the control group (p = 0.05). In contrast, lambs fed the walnut shell biochar -supplemented diet showed significantly higher digestibility coefficients of organic matter (OM), neutral detergent fiber (NDF), and acid detergent fiber (ADF) (p < 0.05). Rumen fermentation parameters were also influenced by the walnut shell biochar supplement, with increased total volatile fatty acid (VFA) concentration (p = 0.03), higher propionate levels (p = 0.054), and reduced protozoa counts (p = 0.0003), while rumen pH (p = 0.76) and ammonia nitrogen (NNH3) concentrations (p = 0.64) remained unaffected. These findings suggest that walnut shell biochar may improve fiber and organic matter digestibility and beneficially modulate rumen fermentation without compromising growth performance in lambs.