The objectives of the current study were to determine methane (CH4) emissions, rumen fermentation characteristics, rumen digestion kinetics and total tract digestibility in sheep from low and high CH4 yield (g/kg dry matter intake; DMI) selection lines fed good or poor quality pasture (vegetative improved vs. very mature unimproved pasture). Methane emissions were determined over 48 h in open circuit respiration chambers, rumen samples were collected 16 h after feeding, and digestion kinetics and total tract digestibility were determined over six days in metabolism crates. Methane emissions and total tract digestibility were similar between low and high CH4 yield selection line sheep fed pasture of two qualities. Phenotypic differences as previously found in selected extremes were observed including shorter rumen retention time of solubles and particles (P<0.05) and lower concentrations of total and individual volatile fatty acids (P<0.05). The lack of interactions between CH4 yield selection line and pasture quality suggest that these phenotypic characteristics of the low CH4 yield selection line sheep are expressed independent of diet quality.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Electronic Poster Session - Challenges - Environmental, , 366, 2018
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