Ovulation timing in the bitch: Conception rate and influencing factors in 1401 estrus cycles

Abstract

Introduction The optimal date for breeding bitches is relatively difficult to determine due to challenges posed by the estrus cycle. Ovulation timing is a service provided by the university clinic in Utrecht for breeders to advise them on the optimal breeding date. The service consists of clinical visits during which bitches are examined for behavioral and physical signs associated with estrus. Also, a blood sample is taken for measurement of plasma progesterone concentration. Based on these findings the date of ovulation and the optimal date for breeding are determined. Objectives The objective of this study was to determine the conception rate and influencing factors when performing ovulation timing. A secondary goal was describing the population presented for ovulation timing in the university clinic. Methods Bitches who were presented for ovulation timing at the Utrecht university clinic from January 2003 to January 2021 were selected for this study. Cases with no registered progesterone concentrations and cases where no conception could not be interpreted were excluded. Available variables were univariably and multivariable analyzed for significance. Results In total there were 1401 cases included. Bitches with a known fertility problem (n=267) showed a significantly (p < .001) reduced chance of conception. Nullipara had a significantly (p=.008) lower conception rate with an 0.69 OR for conception compared to multipara. The odds ratio for conception for autumn (n=326), spring (n=309) and winter (n=392) was 0.58, 0.72 and 0.71, respectively, compared to summer (n=374). Bitches bred using AI (n=163) had a significantly (p < .001) lower conception rate compared to naturally mated bitches (n=824), 53.5% and 84.8%, respectively. Conclusion The overall conception rate when performing ovulation timing in bitches was 79.7%. The five variables in the multivariable model that significantly influenced conception rate were: ‘known fertility problem’, ‘nulliparity’, ‘method of breeding’, ‘season’ and ‘breed size’.