Cow-level factors associated with subclinical hypocalcemia at calving in multiparous Jersey cows

摘要

The objective of our study was to identify cow-levelfactors associated with subclinical hypocalcemia atcalving (SCH) in multiparous Jersey cows. A totalof 598 Jersey and 218 Jersey × Holstein crossbreedcows from 2 commercial dairy herds were enrolled ina retrospective cohort study. Blood samples to determinetotal Ca concentration were collected from thecoccygeal vessels at 3 h 19 min (±2 h 33 min) aftercalving. We used 2 serum Ca concentration thresholdsto define SCH: <2.00 mmol/L (SCH-2.00) and <2.12mmol/L (SCH-2.12). We evaluated the association ofcow-level factors with SCH with multivariable Poissonregression models. Variables evaluated for associationwith SCH were herd; parity (2, 3, and ≥4); breed;previous lactation length and 305-d mature-equivalentmilk yield; previous lactation first test milk yield andlast test somatic cell count; lengths of calving interval,gestation, dry, and close-up periods; body conditionand locomotion scores at calving; calving ease; and calfsex for singletons. We categorized continuous variablesinto quartiles (≤25th percentile, interquartile rangeand ≥75th percentile). The prevalence of SCH amongJersey cows was 40 (SCH-2.00) and 64% (SCH-2.12).Jersey cows of higher parity had greater risk of SCH-2.00 and SCH-2.12. The risk of SCH-2.12 was higherafter birthing male calves. We also found a tendencyfor previous lactation length and previous lactation305-d mature-equivalent milk yield effect to affect riskof SCH-2.12. The risk of SCH-2.12 was lower for cowsthat had a previous lactation length shorter than the25th percentile compared with cows that had a previouslactation length within the interquartile range.The risk of SCH-2.12 was higher for cows that had aprevious lactation 305-d mature-equivalent milk yieldbelow the 25th percentile compared with cows thathad a previous lactation 305-d mature-equivalent milkyield above the 75th percentile. Also, Jersey × Holsteincrossbreed was associated with increased risk of SCH-2.00. In the multivariable analysis, we observed noassociation between SCH and previous lactation firsttest milk yield; last test somatic cell count; lengths ofcalving interval, gestation, dry, and close-up periods;body condition and locomotion scores at calving; andcalving ease. Our study identified parity, breed, calfsex, previous lactation length, and previous lactation305-d mature-equivalent milk yield as cow-level factorsassociated with SCH in multiparous Jersey cows.