Abstract
Due to the unique nature of the rumen, unlike monogastric animals, ruminants like cattle largely depend on microbial hydrolysis of feed rather than post-ruminal enzymatic degradation. However, in ruminants fed high-grain diets, significant amounts of starch can bypass ruminal fermentation, where pancreatic and small intestinal enzymes play a vital role in digestion. Ruminal microbiota, as well as the host animal, require protein as a nitrogen source to optimize digestibility. Hempseed cake (containing >30% of crude protein) is a by-product of hempseed oil production, but currently is not used as a feed source as it is not an FDA-approved feed ingredient. Presently, the availability and costs of protein supplements are volatile, and sourcing alternative protein sources is needed. Therefore, information is necessary on the effect of feeding hempseed cake on ruminant digestive function. This study aimed to evaluate the effects of feeding hempseed cake on pancreatic and intestinal enzymatic activity in finishing heifers. Angus-crossbred finishing heifers (494 ± 10 kg BW) were fed for 111 days with one of two dietary treatments: 20% [dry matter (DM) basis] of dried corn distillers grains plus solubles (n = 16, control) or hempseed cake (n = 16, hemp). All animals were slaughtered at the end of treatment. Intestinal tissues for digestive enzyme assays were isolated and stored at -80(0)C following immediate flash freezing with liquid nitrogen. The MIXED procedure in SAS was used to analyze the data. There was a tendency (P = 0.09) of greater pancreatic tissue mass in the hemp group than in the control group. The activity of pancreatic α-amylase, trypsin, and lipase relative to protein (U/g protein) was less (P < 0.01) in heifers fed hemp than in heifers fed distillers grains primarily because protein concentration (mg/g) and content (g/pancreas) were greater (P < 0.01) in the hemp group than the control group. However, there were no differences (P ≥ 0.2) in digestive enzyme activity (U/g of tissue) in pancreatic and small intestinal tissues. Overall, our results suggest that there was no adverse effect of feeding hemp on the enzymes responsible for nutrient digestion in the small intestine and that hempseed cake may be useful as an alternative source of protein in cattle fed finishing diets.