28 Effect of Dietary Hempseed Meal on Growth Performance and Dry Matter Intake in Yearling Rough-Stock Bulls
Authors: McGovern Samantha L , Brady Jeff A , Guay Kimberly A , Runyan Cheyenne L , Schwertner Thomas W , Smith Lane A , Springer Ryon W , Wellmann Kimberly B 
Published: May 2023

Abstract
The Association of American Feed Control Officials (AAFCO) is gathering information about the safety and efficacy of hemp and its derivatives as potential animal feedstuffs. Yearling rough-stock bulls (n = 38) were used in a randomized complete block design to evaluate the effects of hempseed meal (HSM) as a concentrate ingredient on growth, dry matter intake (DMI), and efficiency. Bulls were blocked by body weight (BW), grouped into 10 pens (n = 3 or 4 bulls/pen), and randomly assigned to hempseed meal (HSM) or a control supplement treatment (CON; 72.5% cottonseed meal, 14.5% soy hulls, and 13% fat). Ingredients for CON were used because they were common commercial commodities and were formulated to match the macronutrients of HSM. Treatments were top-dressed at 10% of the diet, while 90% was fed as a mixed ration [50% bermudagrass hay, 40% textured commercial feed (10% CP)]. Feed delivery, treatment delivery, and orts were recorded daily. Diet samples were dried and used to calculate dry matter intake (DMI). Blood for urea-N (SUN; VetScan Chemistry Analyzer) and BW were obtained on days 0, 21, 42, and 63. Efficiency was evaluated for each period using DMI and average daily gain (ADG). Data were analyzed using the GLIMMIX procedure in SAS 9.4. Results were considered significant at P &lt; 0.05, and tendencies were discussed at 0.05 &gt; P &gt; 0.10. No treatment×time interaction occurred for BW (P = 0.999), ADG (P = 0.563), interim DMI (P = 0.672), feed efficiency (P = 0.254), or SUN (P = 0.170). Treatment did not affect BW (320.4 and 324.69 ± 121.57 kg for CON and HSM, respectively, P = 0.996), but BW increased over time (261.13 ± 74.71 and 322.5 ± 121.57 kg, initial and final BW, respectively, P = 0.001). No treatment effect on ADG occurred (0.73 and 0.84 ± 0.13 kg for CON and HSM, respectively, P = 0.680). However, ADG decreased over time (1.0 ± 0.29, 1.19 ± 0.21 and 0.79 ± 0.13 kg, d0-21, d21-42, and d42-63, respectively, P = 0.005). Daily DMI resulted in a treatment×time interaction, where HSM often consumed more DM than CON (P &lt; 0.01). Interim DMI increased over time (7.44 ± 1.25, 7.84 ± 0.98, and 8.18 ± 0.82 kg, d0-21, d21-42, and d42-63, respectively, P = 0.0073), but when combined with ADG to determine feed efficiency, the main effects were not different (P ≥ 0.17). Over time, SUN increased (4.91, 10.52, 11.66 and 12.72 ± 0.35 mg/dL for days 0, 21, 42 and 63, respectively, P &lt; 0.001), and HSM had greater SUN than CON (10.46 and 9.45 ± 0.30 mg/dL for HSM and CON, respectively, P = 0.0426). These data suggest that bulls fed HSM at 10% diet DM perform similarly to bulls fed the same nutrient profile of standard commercial feed ingredients, indicating comparable nutrient availability between the treatments. Conversely, increased DMI and SUN in the HSM bulls suggest a difference in nitrogen metabolism between the treatments that warrants further investigation.