Metabolic changes in dairy cows at different lactation class during the transition period

Introduction - During the transition period occurring from 3 weeks pre-partum to 3 weeks post-partum, metabolic changes are required in order to accommodate parturition and lactogenesis in mammals. Cows unable to adapt to the metabolic demands during transition period are more prone to negative subsequent events, and the associations between excessive of negative energy balance (NEB) in dairy cows and these detrimental health effects have been reported. Improving in knowledge of metabolic changes may help to supply a new strategy of farm management and reproductive performance in dairy cows during the transition period. Aim - In the present study, the change of BHB, NEFA, insulin and glucose levels in dairy cows at different lactation class have been evaluated around calving. Materials and methods - Fifty-two multiparous Holstein cows were selected from a high producing dairy farm in the Northeast Italy. Animals were dividid in 3 groups according to their lactation class: 16 in second lactation (L2), 17 in third lactation (L3) and 19 in fourth lactation (L4). From each animal blood samples were collected 7±5 days before calving (Pre/C) and 7±5 days after calving (Post/C). On blood samples metabolic profile analysis includeding glucose (Glu; mg/dL), beta-hydroxybutyrate (BHB; mmol/L), non-esterified fatty acids (NEFA; mEq/L) and insulin (Ins; pmol/L) was performed. Two-way analysis of variance (ANOVA) for repeated measures was applied to determine the statistically significant effects of lactation class and of calving period (Pre/C vs Post/C) on studied parameters. Results and discussion - Statistical analysis showed higher NEFA values in dairy cows of L2, L3 and L4 groups at Post/C respect to Pre/C (P<0.05), whereas, lower Ins levels were found in dairy cows of L2 and L4 groups at Post/C respect to Pre/C (P<0.05). No statistically significant effect of lactation class was found on studied parameters (P>0.05). Conclusions - The findings obtained in the present study confirm that metabolic changes occur around parturition in dairy cows suggesting the necessary to determine reference ranges of metabolic variables for cows during precalving and postcalving time.