Date of Award
Master of Science (MS)
Gibbons, John R.
Higdon III , H. Lee
Pratt , Scott L.
Swaying the bovine sex ratio is beneficial because dairy heifers are significantly more valuable than bull calves, whereas in the beef industry, bull calves are more desirable than females. Currently, there is no inexpensive, reliable, effective method for commercially separating X- and Y- bearing sperm. The objective of these experiments was to determine the efficacy of a commercially available post-thaw bovine semen sexing kit, HeiferPlusTM, which claims to sway the sex ratio in favor of female calves.
Three trials included the insemination of hyperstimulated cows with Control or HeiferPlusTM treated semen, non-surgical embryo collection on Day 7, and a novel combined PCR/ Southern blot assay to determine embryo sex. Overall, 271 embryos were collected and a sex was assigned to 265 of them. Chi square analysis showed that the Control group produced a significantly higher proportion (p< 0.0005) of female embryos than the HeiferPlusTM (HP) group (65.0% and 43.0%, respectively). There was no difference in the proportion of transferable versus degenerate embryos and ANOVA showed no difference in the number of ovulations, embryos, and unfertilized oocytes collected from Control versus HP groups. Of the two bulls used in the hyperstimulation studies, one produced an overall higher proportion of females (p< 0.05), suggesting a bull effect.
Another trial involved the insemination of cows synchronized via OvSynch¨ with fetal sexing via ultrasonography between Days 55- 58. Of the 152 cows inseminated, 51.3% (78/ 152) were pregnant at Day 35. Of the cows inseminated with HP treated semen, 54.5% became pregnant and 48.0% of the Controls were pregnant. HP treated cows resulted in 54.8% male (23/ 42) and 45.2% female (19/ 42) fetuses. Control cows had 52.8% male (19/ 36) and 47.2% female (17/ 36) fetuses at 58 days gestation. Chi square analysis showed no significant difference in the sex ratio proportions. Semen from six bulls was used in this trial, and pregnancy rates among bulls were not different. Computer automated semen analysis (CASA) showed that there was no significant difference in motility or progressive forward motility of Control versus HP treated semen in any of the bulls.
Results of these studies indicated that HeiferPlusTM semen sexing kit did not sway the sex ratio in favor of females in either hyperstimulated or single-ovulating cows. In the hyperstimulated cows, the Control group actually produced a significantly higher proportion of female embryos than the HP group. No differences in embryo production or embryo grade were observed. Further research is needed to investigate the effects of semen incubation or other semen manipulations on the sex ratio of cattle.
Curry, Erin, "Determining the Efficacy of a Commercially Available Post-Thaw Bovine Semen Sexing Kit" (2007). All Theses. 176.