title: Evaluation of models of acute and subacute acidosis on dry matter intake, ruminal fermentation, blood chemistry, and endocrine profiles of beef steers.
abstract: Crossbred steers (n = 20; 316 +/- 4 kg BW), each fitted with a ruminal cannula, were used to evaluate the effects of acute acidosis (AA) and subacute acidosis (SA) on DMI, ruminal fermentation, blood chemistry, and endocrine profiles. Animals were blocked by BW and assigned to treatments including 1) intraruminal (via cannula) steam-flaked corn (3% of BW; AA); 2) intraruminal dry-rolled wheat:dry-rolled corn (50:50; 1.5% of BW; SA); 3) offering forage-adapted steers ad libitum access to a 50% concentrate diet (AA control; AC); and 4) offering 50% concentrate diet-adapted steers ad libitum access to a 50% concentrate diet (SA control; SC). Samples of ruminal fluid and whole blood were collected on the day of the challenge (d 0) and 3, 7, 10, and 14 d after the challenge. Daily DMI responded quadratically (P < 0.01) through d 7 for AA and SA steers and increased linearly (P < 0.01) for AC steers. Dry matter intake by AA steers reached a nadir (< 3 kg/d) on d 3 and gradually increased to a level similar to other treatments (7 kg/d) by d 10, whereas DMI by SA steers increased through d 3. Blood pH, bicarbonate, base excess, and total CO2 were decreased (P < 0.03) for AA steers and increased (P < 0.03) for SC steers through d 7. Ruminal pH decreased quadratically (P < 0.01) in AA and AC steers and increased (P = 0.01) in SA steers through d 7. Ruminal total lactate concentration and osmolality responded quadratically (P < 0.01) for AA and AC steers. Ruminal total lactate peaked on d 3 for AA steers and on d 0 for AC and decreased to basal concentrations by d 7. Plasma NEFA concentration increased (P < 0.04) on d 3 and 7 for AA steers. Serum Na decreased (P < 0.05) on d 0 for AA and SA steers and on d 7 and 14 for AA steers. Serum P decreased (P = 0.01) for AA steers through d 7 and decreased quadratically (P = 0.01) for AC steers through d 7. Serum albumin and cholesterol decreased (P < 0.02) for AA and AC steers through d 7. Area under the GH curve decreased (P = 0.02) for AA and AC steers through d 7. Considerable variation was evident in the ability of an animal to cope with a carbohydrate challenge. Results of data modeling generally suggest that serum amylase activity, cholesterol and potassium concentrations, and plasma NEFA concentrations were useful in distinguishing between steers classified as experiencing subacute acidosis or not affected by a carbohydrate challenge.
authors.affiliation: Department of Animal and Range Sciences, New Mexico State University, Las Cruces 88003-0003, USA. msbrown@mail.wtamu.edu
authors.forename: M S
authors.initials: MS
authors.lastname: Brown
authors.forename: C R
authors.initials: CR
authors.lastname: Krehbiel
authors.forename: M L
authors.initials: ML
authors.lastname: Galyean
authors.forename: M D
authors.initials: MD
authors.lastname: Remmenga
authors.forename: J P
authors.initials: JP
authors.lastname: Peters
authors.forename: B
authors.initials: B
authors.lastname: Hibbard
authors.forename: J
authors.initials: J
authors.lastname: Robinson
authors.forename: W M
authors.initials: WM
authors.lastname: Moseley
mesh_terms: D000138:Acidosis / Q000097:blood / Q000378:metabolism / Q000662:veterinary*; D000821:Animal Feed; D000818:Animals; D001774:Blood Chemical Analysis; D001786:Blood Glucose / Q000378:metabolism; D002417:Cattle / Q000097:blood / Q000378:metabolism*; D002418:Cattle Diseases / Q000097:blood / Q000378:metabolism*; D002149:Energy Intake; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000097:blood; D019344:Lactic Acid / Q000097:blood; D008297:Male; D008954:Models, Biological; D012417:Rumen / Q000378:metabolism*; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D007328:Insulin; D019344:Lactic Acid