Effect of by-product feeds, alone or in combination, with a grass-hay based diet on in vitro dry matter disappearance, gas and methane production, and rumen fermentation

Abstract

This thesis evaluated the effects of by-product feeds, alone or in combination, with a grass-hay based diet on in vitro dry matter disappearance, gas and methane production, and rumen fermentation. Firstly, by-products were evaluated using batch culture, alone, as potential energy (Chapter 4) and protein (Chapter 5) sources, for dry matter disappearance (DMD), as well as gas and CH4 production. When included as either a protein or energy supplement, hemp hulls and hemp powder exhibited the lowest DMD, gas and CH4 production (DM basis). However, on a DMD basis, hemp hulls had the highest CH4 production, with flax screenings numerically lowest. Pea hulls had the highest CH4 production and red osier dogwood the lowest CH4 on a DMD basis. The impact of by-product source (month and location of sampling) was also determined, with wheat screenings being most variable and flax screenings and oat pellets being the least variable for the parameters of interest. In Chapter 6, a RUSITEC experiment evaluated the impact of three by-products included in a grass-hay based diet on DMD, gas, CH4 and rumen fermentation. Treatments were grass hay plus quinoa screenings (Quinoa), flax screenings (Flax), or sunflower screenings (Sunflower) compared to a grass-only diet (Control). Compared to the Control, Quinoa and Flax did not affect DMD, however it was reduced (14.5%) with Sunflower. Quinoa and Flax did not effect gas or CH4 compared to the Control, however Sunflower reduced CH4 (irrespective of unit) compared to all other treatments. In conclusion, through the initial screening of by-products, those high in fat and protein including sunflower screenings, flax screenings and hemp hulls, showed lower CH4 production while those high in starch had higher CH4. However, the trends depended on unit of expression and inverse responses were observed when comparing on a DM or DMD basis. On a DMD basis, the inclusion of sunflower screenings showed potential to reduce CH4, demonstrating that high fat concentration has the potential to decrease CH4 production in forage-based diets. Consideration of the impact on DMD and subsequent animal performance is critical for future adoption of high fat-based mitigation strategies involving by-product supplementation.