260 EFFECTIVENESS OF A COMMERCIALLY AVAILABLE POST-THAW BOVINE SEMEN SEXING KIT IN BOTH MULTIPLE-AND SINGLE-OVULATING COWS

Abstract

Currently, there is no inexpensive method for commercially separating X- and Y-bearing bovine sperm cells. Because dairy heifer calves are significantly more valuable than bull calves, a reliable method of swaying the bovine sex ratio in favor of females is desirable in the dairy industry. The objective of these experiments was to determine the efficacy of a commercially available post-thaw semen sexing kit, HeiferPlus^™ (Emlab Genetics, Arcola, IL, USA), which claims to sway the bovine sex ratio in favor of female calves. Three trials included the insemination of hyperstimulated cows with control or HeiferPlus (HP)-treated semen, nonsurgical embryo collection on Day 7, and a novel combined PCR/Southern blot assay to determine 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 < 0.005) of female embryos than the 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 in the control versus the HP groups. Another trial involved the artificial insemination of cows synchronized via OvSynch^® (ABS Global, Deforest, WI, USA) followed by fetal sexing via ultrasonography between Days 55 and 58. Of the 152 cows inseminated, 51.3% 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 of gestation. Calving records confirmed the ultrasound sexing data and showed that three controls and one HP calf died after 58 days of gestation, and one control and one HP calf died within 2 weeks following birth. Chi-square analysis showed no significant difference in the sex ratio. Semen from six bulls was used in this trial, and pregnancy rates among bulls did not differ (P > 0.05). Computer-assisted semen analysis showed no significant difference in motility or progressive forward motility of control versus HP-treated sperm in any of the bulls. Results of these studies indicated that the HeiferPlus semen sexing kit did not sway the sex ratio in favor of females in either multiple- 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 manipulation on the sex ratio of cattle.