title: Effect of rapid or gradual grain adaptation on subacute acidosis and feed intake by feedlot cattle.
abstract: The effects of grain adaptation protocol on subacute acidosis and feed intake by cattle were studied in a completely randomized experiment using 12 crossbred heifers (384 +/- 25 kg BW). The dietary proportion of concentrate was increased from 40 to 90% (DM basis) either by rapid adaptation (65% concentrate diet fed for 3 d) or by gradual adaptation (five intermediate diets containing 48.3, 56.7, 65.0, 73.3, and 81.7% concentrate, fed for 3 d each). Feed intake and ruminal pH (by indwelling ruminal electrodes) were monitored over 20 d. Mean daily pH variables did not differ (P > or = 0.10) between treatments on any of the 3 or 4 d that 65 or 90% concentrate was fed. Variances of a number of pH variables were greater (P < 0.05) for rapidly adapted heifers than for those on the gradual adaptation protocol during adaptation to 65 and 90% concentrate. Mean hourly pH did not differ over the first 24 h of adaptation to 65% concentrate, but variance of hourly pH tended (P < 0.10) to be greater for rapidly adapted than for gradually adapted heifers for eight of the first 24 h. On the first day of feeding 90% concentrate, ruminal pH tended (P = 0.07) to be less at 11 and 12 h after feeding with rapid adaptation than with gradual adaptation. Variance of hourly pH increased steadily in rapidly adapted heifers from 6 h after feeding onward. Ruminal VFA concentration and osmolality did not differ between treatments. Ruminal lactate concentration was < 1 mM, except in two rapidly adapted heifers and one gradually adapted heifer after introduction to 90% concentrate. Adaptation method did not affect DMI or day-to-day variation in DMI. Detection of acidosis was associated with increased variance in ruminal pH variables. A range of individual responses to grain challenge was observed, but current management strategies for preventing acidosis in pens of cattle are based on responses of the most susceptible individuals. A better understanding of factors governing individual responses to acidotic challenge may allow for the development of more effective acidosis prevention practices.
authors.affiliation: Agriculture and Agri-Food Canada Research Centre, Lethbridge, Alberta, T1J 4B1, Canada.
authors.forename: D W
authors.initials: DW
authors.lastname: Bevans
authors.forename: K A
authors.initials: KA
authors.lastname: Beauchemin
authors.forename: K S
authors.initials: KS
authors.lastname: Schwartzkopf-Genswein
authors.forename: J J
authors.initials: JJ
authors.lastname: McKinnon
authors.forename: T A
authors.initials: TA
authors.lastname: McAllister
mesh_terms: D000138:Acidosis / Q000503:physiopathology / Q000662:veterinary*; D000222:Adaptation, Physiological; D000821:Animal Feed; D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D019540:Area Under Curve; D001774:Blood Chemical Analysis / Q000662:veterinary; D001786:Blood Glucose / Q000032:analysis; D002245:Carbon Dioxide / Q000097:blood; D002417:Cattle; D002418:Cattle Diseases / Q000503:physiopathology*; D004435:Eating / Q000502:physiology*; D005232:Fatty Acids, Volatile / Q000032:analysis / Q000378:metabolism; D005260:Female; D005285:Fermentation / Q000502:physiology; D005526:Food, Formulated; D006400:Hematocrit / Q000662:veterinary; D006863:Hydrogen-Ion Concentration; D007770:L-Lactate Dehydrogenase / Q000097:blood; D011897:Random Allocation; D012417:Rumen / Q000737:chemistry / Q000378:metabolism; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D005232:Fatty Acids, Volatile; D002245:Carbon Dioxide; D007770:L-Lactate Dehydrogenase