9:00 am - 10:00 am
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 Iswarya Rajesh. This seminar is open to the general public to attend.
Thesis Topic: Repeatability of anogenital distance in Holstein cattle and its association with embryo yield and quality
MSc with Drs. Divakar Ambrose and Masahito Oba.
Anogenital distance (AGD; the distance from the center of the anus to the base of the clitoris) is a promising new reproductive phenotype in cattle, inversely associated with the measures of fertility, and reported to have high genetic variation and moderate heritability. For a reproductive phenotype to be considered reliable for use in future genetic selection, it should be consistent (repeatable) regardless of the animal’s physiological state and be measurable earlier in life.
Of the two studies conducted, the first was to investigate the repeatability of AGD at different ages (from 0 to 15 months) and physiological states (phases of the estrous cycle, gestation and lactation). Contrary to our expectation, AGD at birth (0 month) was not correlated with that of breeding age (15 month) heifers, but AGD measured at 6 months of age was correlated with the adult AGD. The AGD measurements at the different phases of the estrous cycle, gestation (except at 270 days of gestation) and lactation were highly repeatable within an individual.
To test the hypothesis that the greater fertility associated with short AGD, in previous reports, is attributable to higher quality embryos in short-AGD cattle, the second study determined the differences in embryo yield and quality in superovulated cows and heifers of short- and long-AGD. Although the superovulation response and embryo yield did not differ between short- and long-AGD cows, the proportion of follicles was greater in cows with short-AGD. The proportions of fertilized eggs and viable embryos out of total structures recovered were greater in cows with short-AGD than in cows with long-AGD. However, superovulation response, embryo yield or embryo quality did not differ between short- and long-AGD heifers.
In conclusion, AGD measured at 6 months of age was related to AGD in breeding age heifers; AGD measured during adult life was repeatable at different phases of the estrous cycle, lactation and gestation, except when measured at 270 d of gestation, indicating that AGD may be measured reliably at any physiological state in adult cattle except at an advanced stage of pregnancy. Embryo quality was greater in short-AGD cows than in long-AGD cows, but no AGD-related differences in embryo yield and quality were evident in heifers. The latter findings need validation in a larger population of cattle.