title: Regulation of rumen fermentation during seasonal fluctuations in food intake of muskoxen.
abstract: We studied rumen fermentation of castrated adult muskoxen (Ovibos moschatus; n=4) during periods of low (May) and high (August) food intake. Turnover time (17+/-1.8 h) and volume (26+/-3.9 L) of rumen fluid were consistent between May and August and among days within each season. Rumen temperature did not vary significantly during the day (38.8+/-0.29 degrees C) in either season. Rumen osmolality (271.9+/-16.4 vs. 245.9+/-11.4 mOsm kg(-1)) and pH (6.81+/-0.31 vs. 6.39+/-0.15) were higher in May than in August indicating a shift in the allostatic set point. Rumen fluid pH was more variable in May than in August both before and after a single meal of fermentable substrate even though fermentation acids were lower in May than in August (101.0+/-11.0 vs. 126.0+/-8.74 mM). Changing proportions of minor fermentation acids indicated a shift in metabolic pathways even though bacterial numbers were similar between seasons (6.4+/-5.8x10(9) mL(-1)). Allostatic set points probably alter the homeostatic range of conditions and the microbial diversity of fermentations in herbivores from highly seasonal environments.
authors.affiliation: Department of Biology and Wildlife, PO Box 6100, University of Alaska, Fairbanks, Alaska 99775-6100, USA.
authors.forename: Annie R
authors.initials: AR
authors.lastname: Crater
authors.forename: Perry S
authors.initials: PS
authors.lastname: Barboza
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Forster
mesh_terms: D000818:Animals; D001826:Body Fluids / Q000502:physiology; D004435:Eating; D004492:Edetic Acid; D005232:Fatty Acids, Volatile / Q000378:metabolism; D005285:Fermentation / Q000502:physiology*; D008297:Male; D009919:Orchiectomy; D012417:Rumen / Q000382:microbiology / Q000502:physiology*; D012418:Ruminants / Q000502:physiology*; D012621:Seasons; D013696:Temperature
chemical_list: D005232:Fatty Acids, Volatile; D004492:Edetic Acid