Effects of Timed Breeding on Yield and Sex of Superovulated Bovine Embryos

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Christine Ham and Andrea Louscher.
Dr. Glenn Wehner, Faculty Mentor, 1999.

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Breeding beef cows 12-15 hours pre-estrus has resulted in a significant (P<.025) increase in female calves born (Anim. Repro. Sci. 46:27-34) on an individual cow basis. The current study was conducted to examine the effects on yield of embryos harvested and the ability to influence sex ratios towards females in a superovulated cow bred on a normal time table mucus early breeding. A mature Gelbvieh cow was superovulated with Follicle Stimulating Hormone (FSH) and bred by artificial insemination (AI) at standing heat, again 12 hours and 24 hours later as per industry standards. Yield of embryos was obtained at harvest and sex determined by DNA typing. The treatment was duplicated with the exception of timed AI. Standard plush techniques yielded 12 embryos with a male:female ratio of 9:1 with 2 undetermined. Experimental flashes were disappointing with 2 unfertilized eggs on the first attempt due to hormone problem and 8 embryos ratioed at 6:2 for a second attempt. It was noted that inexperience in timed breeding regime resulted in a later than desired AI resulting in the larger male embryo count. Further research will work with adjusting AI time to better reflect individual cow data.