Factors associated with subclinical hypocalcemia at calving on multiparous Jersey cows
Résumé
The objective was to evaluate factors associated with calcemic status
at calving on 527 multiparous Jersey cows from 2 commercial dairies.
Study variables included: lactation number (Lact; continuous, or 2,
3, ≥ 4); previous lactation 305-d mature equivalent milk production
(Pr305ME) and somatic cell count (PrSCC); calving body condition
score (BCS; ≤ 2.5, 2.75, ≥ 3) and locomotion score (LS; ≤ 2, 3, ≥ 4);
calf number, sex, and stillbirth; and dry period length (dDry). Blood
samples for serum Ca analysis were collected from the coccygeal vessels
3 h 14 min (±2 h 04 min) after calving. Previous lactation information
and calving outcomes were obtained from DairyComp305 herd records.
Based on serum Ca concentration at calving cows were classified as
hypocalcemic (SHC; Ca ≤8.5 mg/dL; n = 347) and normocalcemic (NC;
Ca >8.5 mg/dL; n = 180). Associations among variables were studied
using spearman rank correlations and mixed models for continuous,
and chi-squared and exact fisher tests for categorical data (CORR,
MIXED, GLIMMIX and FREQ procedures of SAS). A significant
positive correlation was observed between Lact and BCS, and both
were negatively correlated with serum Ca concentration at calving.
Cows with SHC had greater (P < 0.001) Lact (3.6 vs. 2.7), frequency
of Lact ≥4 (40.4 vs. 14.4%), dDry (68.8 vs. 64.6 d), and BCS (43.4 vs.
58.2%, 31.2 vs. 27.7% and 25.4 vs. 14.1% for BCS ≤2.5, 2.75 and ≥3,
respectively; P = 0.02[N1]) than NC cows. Twinning rate was higher
for SHC than NC (5.8 vs.1.1%; P = 0.01). The frequency of male calves
(n = 98) was higher for SHC than NC cows (22.4 vs. 14.0%, P = 0.02),
however, sexed semen was selectively used on both dairies and these
results may derive from herd reproductive management. There was no
association of Pr305ME, PrSCC, LS at calving or frequency of stillbirth
with calcemic status. These complex associations among SHC, Lact,
BCS, dDry, twinning and calf sex, could be used for the decision-making
concerning prophylactic SHC treatment at calving.
Domaines
Sciences du Vivant [q-bio]
Origine : Fichiers produits par l'(les) auteur(s)
