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Association of combined serum macromineral profiles with clinical diseases in post-partum Holstein cows
Tsiamadis, V., Banos, G., Panousis...
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Objectives
Post-partum serum concentration distortions of macrominerals (Ca, P, Mg, K) are negatively associated with health and productivity of dairy cows. The individual effects of each one has been studied separately from the others, so far. The objective of this research was to evaluate the association of combined macromineral concentrations during the first and second day in milk (DIM) on clinical diseases in early post-partum dairy cows.
Material and Methods
The research was conducted in compliance with international ethical standards. The study was conducted in 9 Holstein dairy herds; 938 cows were enrolled; parity 1, 2 and 3+ cows were 434, 232 and 272, respectively. Cows were blood-sampled on DIM 1 and 2 to assess serum concentrations of Ca (Ca1, Ca2), P (P1, P2), Mg (Mg1, Mg2) and K (K1, K2), and clinically examined on DIM 1, 2, 4 and 8. Body Condition Score (BCS) was evaluated at DIM 1 and 8. Calcium and Mg concentrations were determined with atomic absorption spectrophotometry, while those of P and K with a biochemical/electrolyte analyzer. The biochemical data set consisted of 7,504 macromineral records. The clinical data set consisted of 3,752 observations including retained fetal membranes (RFM), metritis, mastitis, displaced abomasum (DA) and clinical ketosis (KET). A new trait defined as at least one diagnosis on any of the aforementioned clinical diseases was created (CD_1-8). An Exploratory Principal Component Analysis (PCA) analysis with Direct Oblimin rotation was performed in order to test the null hypothesis that factors to-be-extracted were correlated. After rejecting it, a second PCA with Varimax rotation and Kaiser Normalization, which assumes that factors are independent and uncorrelated, was performed. In both analyses, macromineral concentrations were used as variables. Principal components (PC) were extracted using the elbow rule and used as continuous variables in the subsequent analyses. Afterwards, a univariate binary logistic regression (U-BLR) was performed to assess the effects of herd, parity, calving season, BCS and PC on the likelihood that cows have any of the aforementioned diseases diagnosed on DIM 1 to 8. The interaction between potential covariates was also examined. Predicted probabilities derived from U-BLR were used in subsequent receiver operating characteristic (ROC) analysis in order to evaluate the overall U-BLR model performance and to determine proper macromineral thresholds. All analyses were performed with SPSS ver. 25. Statistical significance was set at P≤0.05.
Results
ROC estimated thresholds (in mmol/L) were: Ca1≤2.1, Ca2≤2.03, P1≥1.9, P2≥4.6, Mg1≤1.01, Mg2≤0.95, K1≤4.5 and K2≤4.8. All estimated model Areas Under the Curve were >0.70 (0.64-0.78). Four components (namely first to forth) accounted for 68.3% of total macromineral variance. First component comprised mainly Ca1, Ca2 and Mg2; Ca and Mg concentrations above thresholds were associated with a decreased probability of metritis, DA and CD_1-8, by 77% (64- 94%), 63% (41-96%) and 76% (65-89%), respectively. Second component included mainly Mg1 and Mg2; Mg concentrations above thresholds were associated with a decreased probability of metritis by 84% (72-99%). Third component comprised mainly Ca2, P2, K1 and K2; concentrations of Ca, K (above thresholds) and P (below threshold) were associated with a decreased probability of KET by 69% (50-96%). Finally, Forth component consisted mainly of P1, P2 and K1; concentrations of P (above threshold) and K (below threshold) were associated with an increased probability of mastitis by 50% (20-90%). Herd significantly affected all post-partum clinical diseases studied. Compared to parity 1, cows in parities 2 and 3+ were 2.3 (1.4-3.6) and 2.1 (1.3-3.4) times more likely to be diagnosed with RFM; compared to parity 1, cows in parity 3+ were also 3.9 (1.7-8.8) times more likely to be diagnosed with KET. Cows with 3.0≤BCS≤3.5 and ≥3.75 were 7.1 (1.7-30.9) and 9.9 (2.0-48.0) times more likely, respectively, to be diagnosed with KET than cows with BCS≤2.75. Cows with BCS≥3.75 were 3.7 (1.3-10.1) times more likely to be diagnosed with KET than cows with 3.0≤BCS≤3.5. In U-BLR analysis no interaction between potential covariates were identified.
Conclusion
When implementing preventive health management measures, serum concentrations of all four macrominerals must be considered simultaneously. Appropriate Ca, P, Mg and K serum profiles would greatly reduce morbidity of post-partum dairy cows.
Keywords: Macrominerals, Principal Components, Calcium, Magnesium, clinical diseases.
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