RESUMO
OBJECTIVE: To evaluate the association between serum phosphorus concentration and the outcome of postpartum downer cows. ANIMALS: Postpartum downer dairy cows presented over a 22-year period. PROCEDURES: In this cross-sectional study (1994 to 2016), medical records of all postpartum downer cows presented to a referral large animal hospital were reviewed. The association between serum inorganic phosphorus concentration and survival was assessed using a multivariable logistic regression. RESULTS: 907 postpartum downer dairy cows were included and classified as hypophosphatemic (mild: > 2.25 to < 3.25 mg/dL, moderate: > 1.50 to ≤ 2.25 mg/dL, and severe: ≤ 1.50 mg/dL), normophosphatemic (≥ 3.25 and ≤ 8.76 mg/dL) or hyperphosphatemic (> 8.76 mg/dL). Hypophosphatemia was observed in 19.4% of the cows (n = 176). Of those, 54.5% (n = 96) were also hypocalcemic. Overall, 58.4% cows (n = 530) survived after hospitalization. Hypophosphatemia was not significantly associated with the outcome of postpartum downer cows (mild: OR = 1.0, 95% CI: 0.6 to 1.8; moderate: OR = 0.5, 95% CI: 0.2 to 1.1; severe: OR = 1.0, 95% CI: 0.4 to 2.4). CLINICAL RELEVANCE: Low serum phosphorus concentration was frequently observed with hypocalcemia and was not associated with the outcome of postpartum downer cows.