Abstract
The objective of this study was to determine the effects of uterine and systemic inflammatory responses to uterine bacterial contamination at calving in dairy cows on the growth and ovulatory outcomes of the first dominant follicle postpartum. Ovulatory capability of the first dominant follicle postpartum was predicted in 53 multiparous cows by using a combination of follicle growth characteristics and circulating estradiol concentrations. Endotoxin levels were assayed in follicular fluid samples that were aspirated the day after ovulatory outcome prediction. Plasma levels of haptoglobin, a proinflammatory acute phase protein, and paraoxonase, a negative acute phase protein were determined. Uterine bacteria and inflammation were evaluated in three uterine fluid samples from each cow collected on the day of calving, the day after follicle aspiration, and at 35 days postpartum. Cows that had a strong initial uterine inflammatory response (robust recruitment of polymorphonuclear leukocytes of ≥ 35% and cows with uterine pH < 8.5 on the day of calving) were more likely to have an ovulatory first dominant follicle. Follicular fluid endotoxin levels were higher in non-ovulatory cows compared with ovulatory cows. Endotoxin levels in circulation were not different between ovulatory groups but were higher prepartum than on day 7 and 14 postpartum. Systemic inflammation characterized by elevated haptoglobin concentrations was higher in non-ovulatory cows despite similar bacterial contamination and circulating endotoxin levels. Paraoxonase activity in follicular fluid was significantly associated with the paraoxonase activity in plasma, however, plasma paraoxonase concentrations were not different between non-ovulatory and ovulatory cows. Cows with a higher uterine bacterial load on the day of calving had slower ovarian follicle growth. In summary, a robust uterine inflammatory response on the day of calving was positively associated with ovarian function while elevated systemic inflammation during the early postpartum period was negatively associated with the ovulatory status of the first dominant follicle postpartum.
Highlights
The fertility of lactating dairy cows is poor compared with that in non-lactating animals [1]
A receiver operator characteristics curve (ROC) analysis was performed to identify the optimal cutoff point which was found to be at 35% polymorphonuclear leukocytes (PMN) and pH 8.5
We conclude that robust initial intrauterine inflammation on the day of calving is beneficial for ovarian ovulatory status while the heightened systemic inflammatory response to uterine bacterial contamination at calving is detrimental for ovulatory status
Summary
The fertility of lactating dairy cows is poor compared with that in non-lactating animals [1]. Dairy cows must overcome two primary challenges to have good fertility later during breeding: namely restoring uterine health and resuming ovulatory ovarian follicular function [2,3]. The ovary must have appropriate follicular function to produce a developmentally competent oocyte and to create a suitable endocrine environment for breeding and pregnancy [1]. These two reproductive processes are distinct, but clearly, there are interactions between uterine health status and ovarian follicular functions. Each ovulation increases in fertility [7] and cows that have an early resumption of ovulation would have more cycles before being bred for the first time and are more likely to become pregnant
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