Effect of hempseed meal on health, growth performance, ruminal fermentation, and carcass traits of intact male goats

Hempseed meal (HSM) is a potential alternative feedstuff for livestock due to its high protein content, but it has not been approved for animal feed in the United States due to safety concerns. This study was conducted to determine the effects of HSM on feed intake, growth performance, serum biochemistry, ruminal papillae morphology, ruminal fermentation profiles, and carcass characteristics of intact male goats. Thirty-six Boer x Spanish intact male goats were randomly assigned to one of four experimental diets (n = 9 goats/diet): 0%, 10%, 20%, and 30% HSM on as-fed basis. Diets were formulated to be isonitrogenous and fed free-choice for ad libitum consumption in the 60-day experiment. Linear and quadratic effects of different concentrations of HSM were determined. Total feed intake, crude protein intake, ruminal papillae morphology (papillae density, length, width, absorptive surface area, stratum corneum, and stratum granulosum thickness), carcass traits (longissimus muscle area, body wall thickness, backfat thickness, shrink percentage), and serum concentrations of most metabolites were similar among treatments (P > 0.05). Intake of acid detergent fiber (ADF) and nitrogen detergent fiber (NDF) increased linearly (P < 0.05) with increasing inclusion of HSM in the diet. Average daily gain (ADG), gain-to-feed ratio, and dressing percentage decreased linearly (P < 0.05) with an increasing percentage of HSM in the diet. Similarly, concentrations of propionic, butyric, iso-butyric, valeric, and isovaleric acids in ruminal fluid decreased linearly (P < 0.05) with an increasing percentage of HSM in diet, whereas concentration of acetic acid and total volatile fatty acids in ruminal fluid tended to decrease linearly (P-value nearly 0.10) with an increasing percentage of HSM in diet. The level of blood urea nitrogen increased linearly (P < 0.05) with increasing concentration of HSM, but values were within the normal range for goats. Findings from the serum metabolite analysis and ruminal papillae morphometrics suggest that goats can be fed HSM at a concentration of up to 30% in their diet. However, growth performance results indicate that further cost-benefit analysis is required to compare HSM with other commonly used protein sources such as soybean meal. These findings will be useful for legal bodies to review during the approval process of HSM as a feed ingredient for goats in the United States.