Ghrelin and its correlation with leptin, energy related metabolites and thyroidal hormones in dairy cows in transitional period.

The transition from late gestation to early lactation is a critical period in a dairy cow's life so that dairy cows undergo tremendous changes during this period. The aim of this study was to determine blood levels of ghrelin, leptin, glucose, β-ydroxybutyrate (BHB), non-esterified fatty acids (NEFA), triglycerides (TG), triiodothyronine (T3) and thyroxine (T4) in dairy Holstein cows (n=20) and their correlations during the transition period. Blood samples were collected weekly from 3 wk antepartum to 6 wk postpartum from 20 high-yielding Holstein-Friesian cows. Ghrelin and leptin of plasma and glucose, BHB, NEFA, TG, T3, T4 of serum were then measured. Early lactation cows showed significantly higher (p<0.05) values of ghrelin, BHB and NEFA, and lower levels of leptin, TG, T3 and T4 (p<0.05) compared to late dry cows. Serum concentrations of glucose did not differ significantly at any time (P>0.05). Plasma ghrelin concentrations showed positive correlations with the serum BHB and NEFA (p<0.01), while plasma ghrelin had negative correlations (p<0.01) with leptin, TG, T3 and T4. In addition, no significant correlation (p>0.05) was found between ghrelin and glucose. The results of the study showed that blood ghrelin, leptin, BHB and NEFA levels are sensitive indicators of the energy balance during the peri-partum period in dairy cows and glucose values may not be considered as a precise indicator of negative energy balance in dairy cows.