Yearling rough-stock bulls (n = 38) were utilized in a randomized complete block design to evaluate dietary hempseed meal (HSM) inclusion on growth (ADG), intake (DMI), and efficiency (F:G). Bulls were blocked by body weight (BW), grouped into 10 pens (n = 3–4 bulls/pen), and randomly assigned to an HSM or control supplement treatment (CON; 72.5% cottonseed meal, 14.5% soy hulls, 13% fat). Treatments were offered at 10%, while 90% was fed as a mixed ration [50% Bermuda grass hay, 40% textured commercial feed (10% CP)]. Diet samples were dried and DMI was calculated. F:G was evaluated using DMI and ADG. Blood for plasma analysis and BW were obtained on sample days, prior to feed delivery. Data were analyzed using the GLIMMIX procedure in SAS version 9.4. The results were considered significant when p ≤ 0.050. There was no treatment × time interaction, or treatment effect for interim BW, ADG, or F:G (p ≥ 0.100). A treatment × time interaction occurred for DMI (p < 0.01), and BW (p = 0.01) increased in all bulls over time, while ADG decreased (p = 0.005), suggesting that interim live performance was not affected by HSM. Plasma urea nitrogen increased over time (p < 0.001) in all bulls, with greater concentrations observed in HSM bulls (p = 0.043).

Neutral detergent fiber (NDF) and acid detergent fiber (ADF) composition have been shown to predict in vitro true digestibility (IVTD), in vitro NDF digestibility (IVNDFD), and in vitro ADF digestibility (IVADFD) in ruminants. This study’s objective was to estimate in vitro digestibility measures within the Daisy^II incubator using equine fecal inoculum from feedstuff NDF and ADF composition. Analyzed feedstuffs included alfalfa hay (Medicago sativa), Coastal Bermudagrass hay, soybean meal, rice bran, hempseed meal, and Bluebonnet® Equilene® Pellets. Data were analyzed using Akaike’s information criterion (AIC) within the R Statistical Program©. The highest ranked model for IVTD was the interaction of NDF and ADF: 10003.32 – 0.2904 × NDF − 0.4220 × ADF − 0.0010 × NDF × ADF (Adjusted R² = 0.959 and AICc = 474.97). Sample IVNDFD was moderately predicted by ADF: 855.15 – 1.5183 × ADF (Adjusted R² = 0.749 and AICc = 560.82). Feedstuff ADF produced the highest ranked model for IVNDFD: 881.91 – 1.5952 × ADF (Adj. R² = 0.835 and AICc = 541.33). These results indicate the effectiveness of using feedstuff NDF and ADF composition to predict IVTD, IVNDFD, and IVADFD within equine fecal inoculum. The findings of this study provide better understanding of feedstuff digestibility using equine fecal inoculum, but more research is warranted for validation of the models and the potential impact in vivo.

Ruminant in vitro methodologies use washing with neutral detergent solution (NDS) after incubation to mimic ruminant digestion, which is physiologically different compared to that of horses. Our objectives were to determine if washing feed samples with NDS before in vitro fermentation (PRE) would suppress fiber digestion versus a post-incubation wash (POST), and to compare in vitro digestibility of forage-based feed mixtures with added soluble carbohydrates (CARB), soluble protein (PROT), or soluble carbohydrates and soluble protein (C + P) to only-forage samples (CONT). Dried, ground feed mixtures sealed in ANKOM filter bags were placed in Daisy^II incubators for 48 h in a split–split-plot batch culture design. Digestibility was determined as in vitro neutral detergent fiber digestibility (IVNDFD), in vitro acid detergent fiber digestibility (IVADFD), in vitro hemicellulose digestibility (IVHD), and in vitro true digestibility (IVTD). The PRE treatment decreased IVHD for CARB versus POST (p = 0.007). Pooling all mixtures, PRE decreased IVTD (p = 0.001), IVADFD (p = 0.036), and IVHD (p = 0.001) and tended to decrease IVNDFD (p = 0.072). The CARB mixture increased IVTD versus all other mixtures (p < 0.001). Pre-washing with NDS suppressed in vitro fermentation by removing soluble carbohydrates. Without removal of soluble carbohydrates to mimic in vivo digestion, fiber digestibility is likely overestimated.

When the 2014 and 2018 US Farm Bills legalized hemp (Cannabis sativa L.), increased farming created an abundance of hemp by-products. Hempseed meal (HSM) is a by-product of hempseed oil extraction. With increasing availability, hemp must be evaluated as a potential feedstuff for sustainable livestock systems. The objective of this study was to evaluate the palatability of HSM as an equine feedstuff. The study used a modified 3x3 Latin Square design utilizing 3 mature geldings (G; 7.3 ± 2.5 yr) and 3 mature mares (M; 12.5 ± 6.5 yr) blocked by sex. Basal feed consumption and bucket preference was established during a washout period of 2 feedings/d over 3 days before each period. During each treatment period (3d) horses were offered either 500g of soybean meal pellets (SBM), rice bran pellets (RBP), or beet pulp pellets (BPP) in one bucket and 500g of HSM in a second bucket each feeding. Feed treatments were switched between bucket positions each feeding. Findings are presented as mean ± SEM. Data were analyzed using an ANOVA within R Statistical Program©. The study found that HSM consumption (351.2 ± 30.6g) did not differ with treatment (p = 0.63), bucket (p = 0.94), or sex (p = 0.67). HSM consumption was greater than SBM (237.7 ± 34.8g; p = 0.005) and BPP (37.0 ± 9.3g; p< 0.001) but was not different from RBP (299.1 ± 35.2g; p = 0.19). HSM consumption increased with each subsequent period (Period 1: 229.6 ± 33.4g; Period 2: 381.3 ± 27.1g; Period 3: 442.6 ± 17.2; p < 0.001). These findings indicate that HSM may be more palatable than SBM and BPP but similar to RBP. HSM consumption may continue to increase over time. HSM may serve as an acceptable replacement to more common feedstuffs used in equine rations.