title: Relationship of rumen fill and fermentation to diurnal and seasonal variation of herbage intake in dairy cows grazed on perennial ryegrass pasture.
abstract: To clarify the effect of digesta weight in the reticulorumen on diurnal and seasonal fluctuations in herbage intake, six ruminally cannulated, non-lactating dairy cows were grazed on perennial ryegrass/white clover pasture during morning and evening sessions in spring and autumn. The digesta weight of fresh matter, dry matter (DM) and fiber in the reticulorumen at the beginning and the end of each grazing session was lower in spring than in autumn (P < 0.01). Although the digesta weight was similar between the sessions at the beginning of grazing, it was greater for the evening than for the morning at the end of grazing (P < 0.01). The large particles proportion in the digesta was lower for the morning than the evening (P < 0.01), and it was lower in spring than in autumn (P < 0.01). The concentrations of volatile fatty acids in rumen fluid were generally higher in spring compared with autumn. The herbage DM intake during the evening was greater compared with the morning in both seasons (P < 0.01). However, there was no difference in herbage DM intake between seasons. The results showed that the rumen digesta fill was not the sole factor explaining diurnal and seasonal variation of herbage intake in grazing dairy cows.
authors.affiliation: Laboratory of Animal Production System, Graduate School of Agriculture, Hokkaido University, Sapporo, Japan.
authors.forename: Koichiro
authors.initials: K
authors.lastname: Ueda
authors.affiliation: Field Science Center for Northern Biosphere, Hokkaido University, Sapporo, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Mitani
authors.affiliation: Laboratory of Animal Production System, Graduate School of Agriculture, Hokkaido University, Sapporo, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Kondo
mesh_terms: D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena / Q000502:physiology*; D000818:Animals; D002417:Cattle / Q000378:metabolism* / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D004032:Diet / Q000662:veterinary*; D004435:Eating / Q000502:physiology*; D005232:Fatty Acids, Volatile / Q000378:metabolism*; D005260:Female; D060434:Herbivory; D008129:Lolium; D012417:Rumen / Q000378:metabolism* / Q000502:physiology*; D012621:Seasons
chemical_list: D005232:Fatty Acids, Volatile
keywords: dairy cow; grazing; herbage intake; rumen fill; season