RESUMO
In this study, the effect of polymorphisms in the leptin gene on the hematological variables in periparturient dairy cows was investigated. The hematological profile of 67 Holstein cows was assessed for 6 wk around calving. The DNA of the cows was genotyped at 6 polymorphic loci within the leptin gene, and 7 haplotypes were reconstructed. Significant haplotype substitution effects were found, for haplotype 1, on total white blood cell count for 2 wk around calving (+0.70 10(3)/µL, P = 0.05; +1.38 10(3)/µL, P = 0.0001); on neutrophil cell count in the first week after calving (+0.94 10(3)/µL, P = 0.001); on lymphocyte count during the 3 wk before and the first week after calving (+0.32 10(3)/µL, P = 0.05; +0.27 10(3)/µL, P = 0.03; +0.26 10(3)/µL, P = 0.04; +0.34 10(3)/µL, P = 0.01); on red blood cell count during the last week before calving and wk 1 and 2 after calving (+0.21 10(6)/µL, P = 0.02; +0.23 10(6)/µL, P = 0.01; +0.20 10(6)/µL, P = 0.03); on mean corpuscular volume (-1.35 fL, P = 0.01; -1.29 fL, P = 0.002; -1.18 fL, P = 0.004; -1.09 fL, P = 0.008; -1.23 fL, P = 0.003; -1.31 fL, P = 0.003); and on mean corpuscular hemoglobin (-0.37 pg, P = 0.05; -0.38 pg, P = 0.02; -0.39 pg, P = 0.01; -0.34 pg, P = 0.03; -0.40 pg, P = 0.01; -0.40 pg, P = 0.01) during all 6 wk analyzed. Significant haplotype substitution effects, but opposite those of haplotype-1, were found for haplotype-2 on white blood cell count (-1.10 10(3)/µL, P = 0.01; -1.30 10(3)/µL, P = 0.002; -1.09 10(3)/µL, P = 0.01) and neutrophil count (-0.82 10(3)/µL, P = 0.02; -0.95 10(3)/µL, P = 0.005; -0.92 10(3)/µL, P = 0.01). Haplotype-3 influenced red blood cell count (-0.23 10(6)/µL, P = 0.03; -0.28 10(6)/µL, P = 0.01; -0.34 10(6)/µL, P = 0.002) during the last 2 wk before and the first week after calving, and also, with effects evident only in wk 3 and 2 before calving, mean corpuscular volume (+1.38 fL, P = 0.03; +0.97 fL, P = 0.05; +1.08 fL, P = 0.05), mean corpuscular hemoglobin (+0.58 pg, P = 0.02; +0.38 pg, P = 0.04; 0.51 pg, P = 0.01), and red blood cell distribution width (-0.56% P = 0.02; -0.47%, P = 0.05). The current study provided evidence that several polymorphisms in the leptin gene play a role in the variability of hematological variables during the peripartum period, and might be used as genetic markers for improving the immunological conditions of dairy cows in critical productive periods.
