153. The Effects of By-product Meals, Hulls and Oils at Varying Inclusion Rates in Lactating Dairy Cow TMR-based Diets on DMD, Total Gas and CH4 Production, and Ruminal Fermentation Parameters In Vitro.

Abstract The fermentation profile of by-product meals, hulls and oils at varying inclusion rates in lactating dairy cow TMR diets were evaluated using in vitro batch culture. Four by-product meals (canola, hemp, soybean, camelina) and hemp protein concentrate (HPC) were included at 10, 15 or 20% (DM basis). Two hull by-products (hemp and soybean) were incorporated at 10% or 20% (DM basis). Four oils (hemp, camelina, canola, and soybean) were added at 3 or 5% (DM basis). Controls were also included without meals, hulls or oils. Rumen fluid was collected from three ruminally cannulated lactating dairy cows, pooled and mixed with a buffer solution (1:2) and incubated for 48 hr. Headspace gas pressures were recorded at 3, 6, 9, 12, 18, 24, 36 and 48 hr, with gas samples collected for CH4 determination. Post incubation, pH, DMD, VFA and NH3-N were measured. Data analyses were performed using PROC Mixed in SAS. Dry matter digestibility for hemp (61.3%) and HPC (64.5%) included at 20% diet DM were lowest, whereas soybean at 10% diet DM (74.0%) was highest relative to the control (67.0%; no meal). Comparing hulls, hemp included at 10 and 20% diet DM (66.8 and 60.9%, respectively) were lower (P < 0.001) relative to the control (71.3%), whereas the soybean products at the same inclusion rates (72.1 and 71.9%) were the highest. Overall, compared to the control (71.0%), oil reduced (P = 0.004) DMD in all treatments and was lowest in soybean at 5% inclusion (65.6%). Total gas production (GP; mL g-1 DM incubated) for soybean at 10% inclusion was highest (206.0; P = 0.01) and it was numerically increased in most meal treatments, with the exception of hemp at 20% inclusion (174.3), relative to the control (176.9). Neither hull nor oil inclusion affected total GP on a DM incubated basis relative to the respective control treatments. Regardless of meal, hull or oil treatment, total GP (mL g-1 DMD) and CH4 production (DM or DMD basis) were not affected. Total VFA concentrations (mmol) for hemp (109.7), soybean (104.0) meals and HPC at 20% inclusion (51.5) were lowest (P < 0.001) and highest in camelina at 15% inclusion (133.0) relative to the control (115.4; no meal). Soybean hulls at 10% inclusion were lowest (102.9; P = 0.004), whereas hemp hulls at 20% inclusion were highest (124.6) relative to the control (119.4). Hemp (55.0), canola (97.9) and soybean (71.4) oil at 5% were lower relative to the control (115.0; no oil). In conclusion, overall hemp products had lower DMD and total GP (DM incubated), however, there was no effect on CH4 production regardless of the unit of expression. The addition of all oils resulted in a linear decrease in DMD, however no CH4 reduction benefit was observed. For image description, please refer to the figure legend and surrounding text. For image description, please refer to the figure legend and surrounding text. For image description, please refer to the figure legend and surrounding text. For image description, please refer to the figure legend and surrounding text. For image description, please refer to the figure legend and surrounding text.