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Interpretive Summary: Estimation of genetic parameters for superovulatory response traits in Japanese Black cows

By: Dr. Emily Taylor

Japanese Wagyu cattle are one of Japan's greatest treasures and are famous for their excellent meat quality. In Japan, embryo transfer is widely used, and the value of Japanese Black calves is much higher than that of the other beef breeds. Therefore, utilizing dairy cows as recipients for Japanese Black cows is very profitable for producers. There is a large variability in the number of oocytes obtained from different breeds of cattle. In addition, the heritabilities of in vivo embryo production traits have yet to be estimated for Japanese Black cattle. The objective of this study was to estimate genetic parameters for superovulatory response traits in order to explore the possibility of genetic improvement in Japanese Black cows. 

Records were analyzed from 1532 donor cows between 2008 and 2018 for a total number of embryos and oocytes (TNE) and the number of good embryos (NGE). The data did not follow a normal distribution and were analyzed with no logarithmic or Anscombe transformation. Without transformation, the heritability estimates were 0.26 for TNE and 0.17 for NGE. With logarithmic transformation, they were 0.22 for TNE and 0.18 for NGE. With Anscombe transformation, they were 0.26 for TNE and 0.18 for NGE. Spearman's rank correlation coefficient between breeding values of cows with more than ten records was ≥0.95 with both transformations. 

In conclusion, data revealed moderate estimated heritability and a high estimated genetic correlation. These estimates varied little between untransformed and transformed data. In addition, the values of rank correlation coefficients of EBVs between with and without transformation were very high. These results suggest that genetic improvement of both TNE and NGE by selection is possible for Japanese Black cows.

This article is available in the Journal of Animal Science.