Jennifer Carrelli | ALES Graduate Seminar

Date(s) - 22/01/2021
1:00 pm - 2:00 pm

A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Jennifer Carrelli. This seminar is open to the general public to attend.

Thesis Topic: Exploration of anogenital distance as a novel fertility phenotype in dairy cattle

MSc with Drs. Divakar Ambrose and Masahito Oba.

Seminar Abstract: With more recent technological advancements, opportunity arises to identify and incorporate novel fertility traits, with the potential to complement current traits, into breeding objectives in an effort to achieve more substantial genetic gain for fertility. Recently, anogenital distance (AGD), measured as the distance from the centre of the anus to the base of the clitoris, has shown an inverse association with measures of fertility in dairy cows. Two studies were conducted to explore the associations between anogenital distance and measures of fertility in a larger population of dairy heifers and cows from Western Canada and the USA.
The objectives of these studies were to: (1) characterize AGD in nulliparous heifers, (2) determine if an inverse relationship between AGD and fertility, previously found in lactating dairy cows, is also evident in nulliparous heifers, (3) validate previous findings that AGD is inversely related to measures of fertility in lactating dairy cows, and (4) determine the association between AGD and milk yield. In both populations, AGD was normally distributed, highly variable, and inversely related with measures of fertility. Heifers with short AGD required fewer services per conception, conceived 6 d earlier, and became pregnant to first artificial insemination (AI) more often than their long-AGD counterparts. Moreover, heifers with long AGD had reduced cumulative pregnancy risk to 450 d of life compared with those with short AGD. Cows with short AGD had improved pregnancy to first AI and remained non-pregnant for fewer days than cows with long AGD. Cows with short AGD tended to require fewer services per conception than their long-AGD counterparts but, cumulative pregnancy risks up to 150 and 250 days in milk did not
differ between AGD categories. Anogenital distance had a weak positive association with 305-d mature-equivalent milk yield. Results demonstrate an inverse relationship between AGD and measures of fertility in nulliparous heifers and confirm previous findings of a similar inverse relationship between AGD and fertility in lactating dairy cows. Moreover, results indicate that the phenotypic selection for AGD will not have a significant impact on milk production. These findings provide further insight into AGD and its associations with fertility on a larger scale, lending further support for AGD to become an indicator of fertility for future consideration in selection indices.