PS3-22. Evaluation of Feed By-product Inclusion in Lactating Dairy Cow TMR Diets and Their Effects on DMD, Total Gas and CH4 Production, and Ruminal Fermentation Parameters in vitro.

Abstract The fermentation profile associated with inclusion of by-product meals, hulls, screenings and oils in lactating dairy cow TMR-based diets was explored using in vitro batch culture. Canola, hemp, soybean and camelina meals and hemp protein concentrate (HPC) were evaluated with a silage-based TMR at 15% inclusion (DM basis). Five hull/screening products (hemp, soybean and canola hulls/screenings) were included at 10% of the diet (DM basis), while oils (hemp, soybean, camelina and canola) were included at 3% of the diet (DM basis) and compared to equivalent standard TMR diets without by-product. Rumen fluid was collected from three ruminally cannulated lactating dairy cows, pooled and mixed with a buffer solution (1:2) incubated for 48 hr. Gas pressure was recorded at 3, 6, 9, 12, 18, 24, 36 and 48 hr, with gas samples obtained for CH4 determination at each timepoint. Post incubation, pH, DMD and VFA and NH3-N were measured. Data was analyzed using PROC Mixed in SAS. When comparing meal by-products, hemp meal had the lowest DMD (66.2%; P < 0.001) relative to the control (75.2%) and soybean meal (76.9%) which did not differ. Among the hulls/screenings, hemp had the lowest DMD (66.3%; P < 0.001), soybean hulls highest (75.6%) with the control intermediate (72.2%). Comparing oils, camelina was lowest (69.1%; P < 0.001) and the control highest (74.3%). For total gas production (GP; mL g-1 DM incubated), hemp meal (187.7) and HPC (187.0) were lowest (P < 0.001) whereas soybean meal (216.1) and the control (no meal; 211.7) were highest. Total GP (DMD basis) was not affected by meal replacement. Methane production (mL g-1 DM incubated) was lowest for hemp meal (17.9; P < 0.001) and highest for soybean meal (22.9). Comparing hulls/screenings, total GP (mL g-1 DM incubated) was lowest (P < 0.001) for hemp products (mean 190.9) and highest for soybean products (mean 206.8). Total GP (mL g-1 DMD basis) and CH4 production were not affected by hull/screening inclusion. Comparing oils, total GP (mL g-1 DM incubated basis) was not affected; however, on a DMD basis, hemp oil was lowest (323.4 ml; P < 0.001) and the control highest (369.1). Methane production did not differ (P ≥ 0.10) from the control. Among meal treatments, total VFA concentration (mmol) was lowest (P = 0.01) in canola (97.9), with soybean highest (125.9) and similar to HPC (117.7) and the control (114.8; no meal). Hull/screening replacement did not affect VFA production. Relative to the control (116.9), soybean oil was lowest (109.7; P = 0.02) and canola oil (130.7) highest. In conclusion, hemp products reduced GP and CH4 but the concomitant decrease in DMD may result in a negative effect on milk production. Other hulls and oil inclusion did not affect CH4 production, however, oil decreased DMD which is undesirable from a productivity perspective. For image description, please refer to the figure legend and surrounding text. For image description, please refer to the figure legend and surrounding text.