Effects of carob (<i>Ceratonia siliqua</i> L.) pod supplementation of lamb diets on <i>in vitro</i> methane production, digestion, and microbial yield

Enteric fermentation in ruminants produces methane (CH₄), which is a major gas that contributes to global warming. The pods of the carob tree, Ceratonia siliqua L., which are abundant in tannins and water-soluble carbohydrates (WSC), could improve microbial protein yield (MPY) and reduce emissions of CH₄ without influencing digestion. The effects of carob pod supplementation in lamb diets on CH₄ emissions, digestibility, partitioning factor (PF), MPY, and EMPY (efficiency of MPY) were examined in this study. Four iso-caloric and iso-nitrogenous lamb diets (17% crude protein, 2650 kcal/kg dry matter) with differing quantities of carob pods were developed and evaluated using the Menke in vitro gas generation technique. Gas production (GP), CH₄ emissions, digestibility, PF, MPY, and EMPY were evaluated during a 24-hour fermentation using buffered rumen fluid from ‘Awassi’ sheep. The incorporation of carob pods considerably decreased gas and CH₄ production (p &lt; 0.001), with a decrease of up to 15% in CH₄ emission at higher levels of supplementation. The increase in PF, MPY, and EMPY was accompanied by no change in digestibility. At 30% supplementation, MPY increased by 35.32 mg, while EMPY increased to 31.5% from 23.14% in the control. There was a linear reduction in gas and CH₄ emission as the amount of carob supplementation increased. Lamb diets supplemented with 30% carob pods had a 15% decrease in CH₄ emissions and an increase in MPY without any change in digestibility. Additional in vivo research is needed to validate the long-term impacts on performance and health, but the results show promise for carob pods to improve ruminant production and decrease emissions of greenhouse gases.