title: Effects of a subacute ruminal acidosis model on the diet selection of dairy cows.
abstract: Two experiments were conducted to study the effects of a subacute ruminal acidosis (SARA) model on diet choice in dairy cows. In the first experiment, 25% of the ad libitum dry matter intake (DMI) of the total mixed ration (TMR) was replaced with wheat-barley pellets (WBP, 50% ground wheat, 50% ground barley). Rumen pH was measured continuously via in-dwelling probes in 4 mid to late lactation cows. This diet change reduced rumen pH by 0.14 +/- 0.02 pH units (mean +/- SE) and increased time below pH 6.0, from 319 +/- 36 min(-1) to 641 +/- 36 min(-1). Hence, the nutritional model successfully induced SARA. The second experiment determined if inducing SARA increases the feed preference for long alfalfa hay compared with alfalfa pellets. The 2 wk of inducing SARA were separated by 1 control wk. Four cows on either SARA and control diets were given a choice of 2 feeds, 2 times per d, for 30 min. The preference ratios (PR = Amount of Hay consumed/Amount of Hay + Pellets consumed) for alfalfa hay during two SARA weeks was greater (0.85 +/- 0.03) compared with the control week (0.60 +/- 0.03). In SARA weeks, average rumen pH was 0.23 +/- 0.03 units lower, and time below pH 6.0 and 5.6 was higher compared to control. These results suggest that when given a choice of feeds, dairy cows alter their diet selection to attempt to attenuate SARA.
authors.affiliation: Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada N1G2W1.
authors.forename: J E
authors.initials: JE
authors.lastname: Keunen
authors.forename: J C
authors.initials: JC
authors.lastname: Plaizier
authors.forename: L
authors.initials: L
authors.lastname: Kyriazakis
authors.forename: T F
authors.initials: TF
authors.lastname: Duffield
authors.forename: T M
authors.initials: TM
authors.lastname: Widowski
authors.forename: M I
authors.initials: MI
authors.lastname: Lindinger
authors.forename: B W
authors.initials: BW
authors.lastname: McBride
mesh_terms: D000138:Acidosis / Q000503:physiopathology / Q000662:veterinary*; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000503:physiopathology*; D004032:Diet; D005260:Female; D005518:Food Preferences; D001467:Hordeum; D006863:Hydrogen-Ion Concentration; D000455:Medicago sativa; D012417:Rumen; D013272:Stomach Diseases / Q000503:physiopathology / Q000662:veterinary*; D014908:Triticum