Importance of breeding management in abnormal estrous cycles: a case study

In the expanding small animal breeding industry, accurate estrus detection and ovulation timing are essential for breeding management. Many clinics rely on inhouse progesterone tests for convenient and efficient results. Despite widespread use of these tests, it is critical to monitor progesterone concentrations comprehensively due to potential abnormalities in the estrous cycles of individual patients. Such an anomalous cycle was diagnosed in Suzie, a 3.5 year old Fawn Chinese Pug, who was presented to Crestwood Veterinary Centre for artificial insemination. Suzie’s baseline progesterone concentration on December 18, 2019 was 0.8 nmol/l (0.25 ng/ml) with concurrent clinical proestrus signs. Regular progesterone monitoring at 2 - 3 day intervals continued until December 27, 2019, where an increase to 4.0 nmol/l (1.26 ng/ml) indicated an impending luteinizing hormone (LH) surge. Despite this, on December 30, 2019, progesterone concentration decreased abruptly and was undetectable. Vaginal cytology had cornified cells confirming estrus. Suzie was bred on January 1 and 3 via artificial insemination with fresh semen; however, pregnancy was not achieved. A theriogenologist reviewed this case and suggested that Suzie’s progesterone decrease after an apparent LH surge indicated she had not ovulated, and therefore should not have been bred. Her progesterone readings suggested an atypical estrous cycle, possibly a split heat or anovulatory cycle. ¹ It was recommended to monitor Suzie’s next cycle using serial examinations of serum progesterone and vaginal cytology, and to breed only after confirmation of ovulation via serum progesterone 2 - 3 days after the perceived LH surge. It was also suggested to induce ovulation using gonadotropin-releasing hormone or human chorionic gonadotropin in case of repeated anovulatory cycles. With advances in theriogenology, we are better able to understand dysfunctional or abnormal canine estrous cycles and to provide suitable advice to our clients in their management.

Keywords: Estrus, progesterone, canine, luteinizing hormone, artificial insemination, ovulation

Reference

1.Meyers-Wallen VV: Unusual and abnormal canine estrous cycles. Theriogenology 2007;68:1205-1210.

This manuscript was originally published in the journal Clinical Theriogenology Vol 12(3) Sept 2020.  Clinical Theriogenology is the official journal of the Society for Theriogenology (SFT) and the American College of Theriogenologists (ACT).  This content has been reproduced on the IVIS website with the explicit permission of the SFT/ACT.