title: Incidence, prevalence, severity, and risk factors for ruminal acidosis in feedlot steers during backgrounding, diet transition, and finishing.
abstract: The objective of this study was to determine the incidence, prevalence, severity, and risk factors for ruminal acidosis in feedlot steers during backgrounding, diet transition, and finishing. Steers were purchased from a local auction market (n = 250; mean ± SD; 330 ± 20.0 kg initial BW) and were grouped together with 28 steers fitted with a ruminal cannula (248 ± 25.5 kg initial BW). Steers were randomly allocated to 1 of 8 pens (3 to 4 cannulated steers per pen with a total of 35 steers/pen). The feeding period (143 d) was divided into 4 phases: backgrounding (BKGD; d 1 to 20), diet transition (TRAN; d 21 to 40), and the first (FIN1; d 41 to 91) and second half (FIN2; d 92 to 143) of finishing. The BKGD diet contained (% DM) barley silage (45.7%), barley grain (41.6%), canola meal (4.2%), and a pelleted mineral and vitamin supplement (8.5%). Steers were transitioned to a finishing diet containing (% DM) barley silage (5%), barley grain (80.9%), canola meal (4.9%), and a pelleted mineral and vitamin supplement (9.2%) using 4 transition diets. Feed was offered to achieve 5% refusals (as-is basis). Ruminal pH was recorded in cannulated steers every 10 min throughout the study, and feed refusals and BW were recorded at 2 wk intervals. Mean ruminal pH (P < 0.01) was 6.4, 6.3, 6.2, and 6.0 ± 0.01 during the BKGD, TRAN, FIN1, and FIN2, respectively. The duration (P < 0.01) pH < 5.5 was 4.1, 12.1, 78.7, and 194 ± 9.4 min/d during BKGD, TRAN, FIN1, and FIN2, respectively. Using a threshold of ruminal pH < 5.5 for at least 180 min to diagnose ruminal acidosis, incidence was defined as the number of times steers experienced ruminal acidosis during each period and prevalence was defined as the percentage of steers that experienced acidosis during each period. On average, the incidence rate (P < 0.01) of ruminal acidosis was 0.1, 0.3, 6.7, and 14.8 ± 0.97 episodes during BKGD, TRAN, FIN1, and FIN2, respectively. In the same order, the prevalence (P < 0.01) was 0.7, 1.7, 15.4, and 37.8 ± 2.0%. Based on multiple regression, factors associated with prevalence of ruminal acidosis and the duration pH < 5.5 were feeding phase (P < 0.01) and DMI (P < 0.01). Overall, the greatest incidence, prevalence, and severity of ruminal acidosis were observed towards the end of the finishing phase and were associated with days on feed and DMI.
authors.affiliation: Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Canada, S7N 5A8.
authors.forename: E
authors.initials: E
authors.lastname: Castillo-Lopez
authors.affiliation: Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Canada, S7N 5A8 Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada, S7N 5A8.
authors.forename: B I
authors.initials: BI
authors.lastname: Wiese
authors.affiliation: Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada, S7N 5A8.
authors.forename: S
authors.initials: S
authors.lastname: Hendrick
authors.affiliation: Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Canada, S7N 5A8.
authors.forename: J J
authors.initials: JJ
authors.lastname: McKinnon
authors.affiliation: Agriculture and Agri-Food Canada, Lethbridge, Alberta, Canada, T1J 4B1.
authors.forename: T A
authors.initials: TA
authors.lastname: McAllister
authors.affiliation: Agriculture and Agri-Food Canada, Lethbridge, Alberta, Canada, T1J 4B1.
authors.forename: K A
authors.initials: KA
authors.lastname: Beauchemin
authors.affiliation: Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Canada, S7N 5A8 greg.penner@usask.ca.
authors.forename: G B
authors.initials: GB
authors.lastname: Penner
mesh_terms: D000138:Acidosis / Q000453:epidemiology / Q000209:etiology / Q000662:veterinary*; D000821:Animal Feed; D000818:Animals; D002417:Cattle; D004032:Diet / Q000662:veterinary*; D006863:Hydrogen-Ion Concentration; D015994:Incidence; D008297:Male; D015995:Prevalence; D012307:Risk Factors; D012417:Rumen / Q000378:metabolism*; D012720:Severity of Illness Index; D013272:Stomach Diseases / Q000453:epidemiology / Q000209:etiology / Q000662:veterinary*
keywords: backgrounding; diet transition; feedlot cattle; finishing; prevalence; ruminal acidosis