Evaluation of hempseed cake on cattle performance, carcass characteristics, feeding behavior and plasma metabolites in finishing diets

Thirty-one cross-bred heifers were assigned randomly to one of two treatments: a diet containing 20% dried distillers grains plus solubles (DDGS; CON) or 20% hempseed cake (HEMP) on a dry-matter basis. Cattle were fed for 111 days and were slaughtered at the end of the trial to determine potential withdrawal effects of hempseed cake. During the course of the study, body weights (BW) and blood were collected bi-weekly. Feeding behavior was monitored throughout the trial using the Insentec bunk system. Blood samples were processed for the analysis of plasma metabolites including glucose, urea nitrogen (N) and total amino acids (AA). Data were analyzed as a completely randomized design using the MIXED procedure of SAS. Final BW, average daily gain (ADG), feed conversion (F:G) and hot carcass weight (HCW) were reduced by 2.3%, 7.7%, 7.7% and 2.6%, respectively (P ≤ 0.05), in HEMP cattle, compared with DDGS cattle. Plasma urea N concentration increased (P < 0.01) by 21% in heifers fed hempseed cake, compared with DDGS.

Industrial hemp production has been revitalized in the U.S. after it was removed from the list of U.S. Drug Enforcement Agency Schedule 1 drugs as a result of the 2018 Agricultural Improvement Act. A series of pilot studies was allowed under the 2014 Agricultural Improvement Act and led to reinstating industrial hemp production cultivation. Industrial hemp must contain less than 0.3% delta-9-tetrahydrocannabinol (THC), which is the psychoactive component of the hemp plant.

Mechanical processing of the hemp seed for oil extraction has increased with the rise in demand for hemp oil for human use. This process creates a byproduct that is high in fiber and protein (roughly 50% and 30%, respectively) but limited markets are available for it because hemp and hemp byproducts are not an FDA-approved feedstuff for livestock in the U.S.

Because of the nutrient profile of the hempseed byproduct (hempseed cake), ruminants are an ideal target species because of their ability to convert fiber to usable energy. Furthermore, hemp and hemp byproducts are thought to potentially have therapeutic benefits when fed to livestock (Kleinhenz et al., 2020). While feeding hemp byproducts is legal in the European Union (among other places), relatively limited data is available on the nutritive value of hempseed cake as a protein source to beef cattle (Hessle et al., 2008).

Thirty-one cross-bred heifers (initial body weight [BW] = 1,091 pounds; SD = 99) were assigned randomly to one of two treatments: a diet containing 20% DDGS (CON, n = 16) or 20% hempseed cake (HEMP, n = 15) on a dry-matter basis (Table 1). Diets were corn-based (10% roughage) finishing rations formulated to meet or exceed ruminally degradable and metabolizable protein, vitamin and mineral requirements.

1 - Dried distillers grains plus solubles (DDGS).
2 - Formulated to supply monensin (Rumensin-90, Elanco Animal Health, Greenfield, Ind.) at 36 grams/ton. Urea included at 1% of diet DM.
3 - Average of weekly samples.

Cattle received 36 grams/ton of Rumensin and each diet contained 1% urea. On day one, heifers were implanted with Revalor H. Body weights were collected on days zero, one, two, three, seven, 14 and biweekly until day 98, with the final BW occurring at slaughter (days 112 to 120). Additionally, blood samples were collected via jugular venipuncture and centrifuged to obtain plasma on days zero, two, three, seven, 14, 28, 42, 56, 70, 84 and 98 and were analyzed for glucose and urea N concentrations.

Plasma samples were analyzed for AA concentrations on days zero, seven, 56 and 98. For this report, only total plasma amino acid concentrations are presented.

At the conclusion of the 111-day feeding period, cattle were assigned to slaughter groups on five days within a nine-day window between days 112 and 120. Carcass data were collected after cattle were slaughtered via captive bolt stunning and exsanguination.

Dietary net energy for maintenance (NEm) and net energy for gain (NEg) were calculated using performance data as described by Galyean (2009) and the National Research Council (NRC; 1996). Feeding behavior data were collected using the Insentec bunk system. Data were analyzed using the MIXED procedure of SAS, with initial BW used as a covariate for performance and carcass data and repeated measures were utilized for plasma metabolite data.

The nutrient analysis shows that dry matter, crude protein, ether extract and neutral detergent fiber (NDF) concentrations were comparable, while acid detergent fiber (ADF) was 5 percentage units greater (numerically) for the hemp treatment (Table 2).

1 - Performance parameters: Initial body weight (BW), final BW, dry-matter intake (DMI), average daily gain (ADG), feed conversion (F:G), Net energy for maintenance (NEm, Mcal/lb), Net energy for gain (NEg, Mcal/lb).
2 - Carcass characteristics: Hot carcass weight (HCW), dressing percent (Dress %), longissimus muscle area (LM area).
3 - Marbling score: 400 = Slight00, 450 = Slight50, 500 = Small, etc.
4 - Yield Grade (YG) = 2.50 + (0.9843 x rib fat thickness, cm) + (0.2 x 2.5% kidney, pelvic and heart fat), + (0.0084 x hot carcass weight) – (0.496 x LM area, cm2; USDA, 2016).

Heifers fed DDGS had greater final BW, average daily gain (ADG) and feed conversion, compared with HEMP cattle (P ≤ 0.05; Table 3), while dry-matter intake (DMI) was not different between treatments (P = 0.94).

1 - Linear (Lin) and quadratic (Quad) effects were tested for each variable across days.

The observed lack of effect on DMI is similar to what other authors have reported (Mustafa et al., 1999; Gibb et al., 2005) from cattle fed hempseed meal. Dietary NEm and NEg (megacalorie per kilogram [Mcal/kg] of feed, DM basis) was greater for CON, compared with HEMP treatments (P = 0.02). While dietary energy is lower for HEMP, compared with the CON diet, the NEm and NEg values for the HEMP diet are comparable to many finishing diets commonly fed.

These performance-based measures of feed energy and availability indicate that finishing cattle performance should be reduced, compared with cattle receiving a finishing ration containing DDGS at the current inclusion rate of 20% (DM-basis). Hot carcass weight (HCW) was greater (P = 0.03) in heifers fed DDGS vs. hempseed cake while all other carcass characteristics were not different (P ≥ 0.37). This agrees with previous research where feeding hemp products did not affect carcass characteristics (Hessle et al., 2008; Gibb et al., 2005).

Feeding behavior was not different between treatments (P ≥ 0.32; data not shown). While the effect of hempseed cake on cattle feeding behavior has not been reported elsewhere, the lack of effect is not surprising because of the observed lack of difference in DMI. Greater ADF concentration in the HEMP diet, compared with the CON diet, may explain some of the performance differences that were observed in this experiment

Total AA were not different between treatments (P = 0.53; Table 4); however, we observed a day effect (P < 0.01; Table 3). With some exceptions, the general trend of individual AA concentration in plasma decreased between day zero and seven and then increased from day seven to 56 and 98, surpassing day zero baseline levels. The observed decrease between day zero and seven could be a result of stress/immune response in the heifers, shifting the use of AA toward acute phase protein synthesis rather than growth.

Plasma glucose was not different (P = 0.17) between treatments, while urea N increased (P < 0.01) in HEMP heifers, compared with CON heifers. Day was significant for glucose and urea N (P < 0.01), while an interaction between treatment and day was observed for urea N (P < 0.01). The observed greater plasma urea N was likely because the hempseed cake diet had greater CP concentration. This also indicates that the protein with hempseed cake is likely digested and utilized somewhat similarly to the diets containing DDGS.

Further understanding of how hempseed cake influences performance is necessary to better understand the quality of this feedstuff for use in cattle diets. Overall, the results of this study suggest that hempseed cake has lower dietary energy relative to DDGS, while still providing the cattle with adequate nutrition to support acceptable performance
of finishing cattle. While industrial hemp byproducts are not an approved feedstuff, these data suggest that, although hempseed cake may have lower nutritional quality and potentially result in marginally lower performance than DDGS, it could be a viable alternative feed source for ruminants depending on availability and cost.

Galyean, M. 2009. The Home Page of Michael Galyean. NEm and NEg Calculations. Available: www.depts.ttu.edu/afs/home/mgalyean/. Accessed Aug. 9, 2021.

Gibb, D.J., M.A. Shah, P.S. Mir and T.A. McAllister. 2005. Effect of full-fat hemp seed on performance and tissue fatty acids of feedlot cattle. Can. J. Anim. Sci. 85:223-230.

Hessle, A., M. Eriksson, E. Nadau, T. Turner and B. Johansson. 2008. Cold-pressed hempseed cake as a protein feed for growing cattle. Acta Agriculturae Scand Section A. 58:136-145

Kleinhenz, M.D., Magnin, G., Lin, Z., Griffin, J., Kleinhenz, K.E., Montgomery, S., Curtis, A., Martin, M., and Coetzee, J.F. 2020. Plasma concentrations of eleven cannabinoids in cattle following oral administration of industrial hemp (Cannabis sativa). Scientific Reports. 10(1):1–7.

NRC. 1996. Nutrient Requirements of Beef Cattle: Eighth Revised Edition. The National Academies Press. Washington, D.C.

Mustafa, A.F., J.J. McKinnon and D.A. Christensen. 1998. The nutritive value of hemp meal for ruminants. Can. J. Anim. Sci. 79:91-95