Impact of endometritis on post-partum ovarian cyclicity in dairy cows

Highlights

• Cows with endometritis had increased risk of atypical progesterone profiles.

• Prolonged luteal activity was the principal cyclicity problem associated with endometritis.

• Cows with endometritis had a 3-day delay in the onset of luteal activity.

• Endometritis was not associated with adverse effects on delayed first ovulation or cessation of cyclicity.

• The effect of endometritis on ovarian cyclicity was dependent on the grade of endometritis.

Abstract

Endometritis in dairy cows is a major global issue and has been associated with a decrease in reproductive performance. The aim of this study was to quantify the effect of endometritis (as defined by the presence of any abnormal vaginal discharge after 21 days post-partum) on post-partum ovarian cyclicity in dairy cows. Milk progesterone analysis was used to monitor reproductive cyclicity in 170 dairy cows across three different commercial herds. Associations between the occurrence of endometritis and the incidence risk of a variety of atypical cycle profiles during the calving to conception period were investigated to establish the importance of endometritis on post-partum ovarian activity.

Endometritis increased the incidence odds of atypical ovarian profiles (P < 0.05) with prolonged luteal activity being the most affected (P < 0.05), but also showed prolonged time (3 days) to onset of luteal activity after parturition (P < 0.05). Using milk progesterone analysis, we found a relatively low incidence odds for reproductive cycle problems in healthy cows during the calving to conception period. However, the incidence odds of cycle problems, in particular prolonged luteal activity, were high in cows that had experienced endometritis, which would have significantly impaired reproductive function.

Introduction

To achieve a calving interval of 365 days, cows should resume their ovarian cycles within 25 days post calving and conceive within 85 days post-partum. Endometritis is the principle infectious disease of the uterus at this time and is caused by persistent bacterial infection after calving (Sheldon et al., 2006, Barlund et al., 2008, Gilbert et al., 2005, Runciman et al., 2008, Sheldon et al., 2009). Often, the real impact of endometritis is only measured by subsequent analysis and, while the economic impact of this disease remains to be fully quantified, it is speculated to cost many millions of pounds annually for the UK dairy industry alone (McNaughton and Murray, 2009).

The mechanism by which uterine infection with bacterial endotoxin during the post-partum period adversely affects fertility is likely to be multi-factorial influencing fertility both locally and systematically. There is a disruption in the production of prostaglandin (PG) F_2α and PGE₂ by the endometrium (Herath et al., 2009). At the same time, there is an alteration to immune system mediators and production of cytokines, which can affect the function of the hypothalamus and pituitary gland (Sheldon et al., 2009). An important observation was that uterine infection adversely affected follicular growth and function (Sheldon et al., 2002) with the bacterial endotoxin lipopolysaccharide (LPS) detected in follicular fluid.

An association between clinical signs of uterine inflammation and post-partum ovarian cyclicity has been reported previously (Opsomer et al., 2000, Mateus et al., 2003, Taylor et al., 2003, Shrestha et al., 2004, McCoy et al., 2006, Williams et al., 2007). Milk progesterone monitoring has been used widely for assessment of ovarian function, reproductive patterns and abnormalities in dairy cows (King et al., 1976, Bulman and Lamming, 1978, Bulman and Lamming, 1979). One abnormality identified by progesterone profiling is prolonged luteal activity. Abnormal ovarian profiles, mainly prolonged luteal activity, have been associated with an abnormal uterine environment which can perturb the production of prostaglandins (Opsomer et al., 1998). The risk factors for prolonged luteal activity have included metritis, abnormal vaginal discharge and retained fetal membrane (Opsomer et al., 1998, Opsomer et al., 2000). This supports the concept that uterine inflammatory/infection problems could lead to prolonged luteal activity post-partum as well as follicular dysfunctions such as smaller follicles and reduced oestradiol secretions. However, the sequelae of cows having endometritis on the distribution of the different atypical ovarian profiles (i.e. cessation of cyclicity, delayed ovulation or prolonged luteal activity) is less clear and whether particular atypical ovarian profiles are affected. Thus, the objective of this study was to quantify the incidence risk of different atypical ovarian profiles in dairy cows experiencing post-partum. This was then further expanded to compare the influence of different grades of endometritis on ovarian cyclicity.