Possible markers of uterine and metabolic health in transition dairy cows
In transition dairy cows negative energy balance (NEB) status commonly leads to perturbed fertility, reduced immune function and decreased milk yield. The objective of this study was to investigate the relationship between indicators of NEB, systemic inflammation postpartum and genital diseases in transition dairy cows. Prepartum Holstein cows (n=10), from 20d before the predicted day of calving until 35d in milk (DIM) were assigned to two treatments: NEB (80% net energy requirements) and control. Dry matter intake (DMI) was recorded daily and clinical evaluation was conducted once a week. From the day of calving, milk yield, somatic cells count (scc), lactose, fat, protein and fat/protein ratio were recorded daily. From 7 till 35 DIM, weekly endometrial samples were collected for cytological evaluation, metagenomic characterization of the endometrial DNA and measurements of the expression of inflammatory genes. Ovarian activity was monitored every other day from 7 DIM. Blood samples were collected weekly and analyzed for non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHBA) and cholesterol. Correlationship between variables was evaluated using Spearman’s rank correlation test. Moreover, a stepwise regression analyses was performed to explain variability of indicators of uterine and metabolic status. As expected, NEB cows showed higher DMI (P <0.1), lower milk production (P <0.05) and a higher fat: protein ratio (P <0.05) until 35DIM. In addition, NEFA and BHBA were higher in the NEB cows (P <0.05), while cholesterol was lower (P <0.001). Moreover, even if not strong, a negative correlation was observed between BHBA levels and increment in BCS (- 0.37), and between NEFA and numbers of dominant follicles observed (-0.25). In addition, a negative correlation was observed between percentage of polymorphonuclear cells (PMS), from the endometrial samples, and serum cholesterol (- 0.40) supporting our hypothesis that total cholesterol level could be one of the possible markers for uterine health evaluation. In addition a positive correlation was observed between NEFA and PMS cells (- 0.40). Furthermore the stepwise regression analysis confirmed that serum BHBA and cholesterol levels were the ones that better explained the other variables (clinical evaluation, intake, reproduction). Data regarding the metagenomic characterization of the endometrial DNA and on the expression of inflammatory genes are still pending. The preliminary results confirmed the effects of NEB on biochemical parameters with potential as predictors of metabolic and genital diseases. Further validation based on larger data sets is required.
Keywords: NEB, transition cow, uterine involution