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Repeatability of ano-genital distance measurements at different stages of the estrous cycle.

I. Rajesh

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06-23-2020

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Abstract:

T100
Repeatability of ano-genital distance measurements at different stages of the estrous cycle.
I. Rajesh*1, M. Gobikrushanth1, J. E. Carrelli1, D. J. Ambrose1,2. 1Department of Agricultural, Food and Nutritional Science, University of Alberta Edmonton, AB, Canada, 2Livestock Research Section, Alberta Agriculture and Forestry Edmonton, AB, Canada.

The fertility of dairy cows may be improved by genetic selection for novel fertility traits. In a recent report from our lab, ano-genital distance (AGD; the distance from the center of the anus to the base of the clitoris), a novel reproductive phenotype, in Canadian Holstein cows was inversely associated with fertility and had moderate heritability. In addition to heritability, repeatability (i.e., the closeness of the measurements taken at different time points by the same person) is important for AGD to qualify as a potential fertility trait. The objective of this study, therefore, was to determine if AGD is repeatable at the different stages of the estrous cycle. The AGD was measured in triplicate (the mean value used), in 20 Canadian Holstein cows that were subjected to estrous synchronization using a progesterone-device-based ovulation synchronization protocol. The ovaries were subjected to transrectal ultrasonography and blood samples were collected for plasma progesterone quantification, every other day, starting from first ovulation until the subsequent ovulation. The stages of the estrous cycle were classified as proestrus, estrus, metestrus, and diestrus based on the size of corpus luteum and plasma progesterone concentration. Data were analyzed using the MIXED and CORR procedure of SAS. The average AGD measurements at different stages of the estrous cycle within the same animal did not differ (AGD at proestrus, estrus, metestrus, and diestrus were 130.81 � 2.1, 131.19 � 2.1, 131.17 � 2.1, and 131.38 � 2.1, respectively; P = 0.99) and the correlation between them was very high (r = 0.98; P < 0.01). In summary, AGD was not affected by the stages of the estrous cycle and AGD measurements were highly repeatable. Our findings further strengthen the reasons for pursuing AGD as a potential fertility trait.

Keywords: reproductive phenotype, genetic selection, heritability.

Biography: I earned a Doctor of Veterinary Medicine degree from Tamil Nadu Veterinary and Animal Sciences University in 2017 in India. Currently, pursuing my Master's degree at the University of Alberta, majoring in Animal Science - Reproductive Physiology under the advisory of Dr. Divakar Ambrose.