Spent hemp biomass in broiler diets: effects on performance, meat quality, expression of genes in internal adipose tissue, and corticosterone in feathers.

Prior use of spent hemp biomass (SHB), a byproduct of cannabidiol extraction, has shown promise as a low-cost livestock feed in ruminant diets. However, due to concerns over residual cannabinoids in carcass tissues, it has not been approved by the FDA-CVM for livestock use. Moreover, research on SHB effects in monogastrics remains scarce. The objective of this study was to examine varying levels of dietary SHB inclusion in broiler diets and their effects on performance, meat quality, expression of genes in adipose tissue, and stress. Two hundred (n=200) 5-day-old Cobb-500 chicks were randomly assigned to corn-soybean-based diets containing 0%, 5%, 10%, or 20% SHB for a 42-day feeding trial (5 pens/group). Diets were isocaloric, isonitrogenous, and balanced for fiber. At the end of the experiment, birds were euthanized and sexed, with two males and two females selected from each pen (n=80) for subsequent sampling. Feed intake was not adversely affected by SHB supplementation; however, inclusion at ≥10% negatively impacted feed conversion rate and body weight, while pasty vent was higher in all SHB treatments than in the control. Dietary SHB at ≥10% level decreased growth and breast weight. SHB at 20% level increased breast yellowness (b*), drip loss (vs. lower SHB doses), and shear force (i.e., lower tenderness). Feeding 20% SHB decreased triglycerides, total fatty acids, and the proportion of unsaturated fatty acids in muscle (vs. lower SHB doses), while increasing the proportion of cholesterogenic and bacteria-derived fatty acids (vs. lower SHB doses), suggesting SHB affects lipid synthesis and utilization. This was confirmed by the increase in transcription of genes involved in fat catabolism, ACAA1 and ACOX, in the abdominal adipose tissue, specifically for males. Birds receiving 20% SHB also had higher corticosterone in the feathers, indicating possibly higher chronic stress. Overall, dietary SHB inclusion at levels ≥10% negatively affected broiler performance, meat quality, lipid metabolism, and corticosterone in feathers (as a chronic stress indicator), whereas inclusion at 5% did not produce adverse effects. These results indicate that low levels of SHB may be incorporated into broiler diets without compromising bird health or productivity, although higher inclusion rates appear detrimental.