In an investigation on the effect of position of deposition of the egg within the uterus, surgical transfer of single eggs to the tip of the horn resulted in a significantly higher pregnancy rate than transfer to the base. To determine embryo survival at differing times after transfer single eggs were transferred non-surgically to the base of the uterine horn. The highest pregnancy rate occurred in a group of heifers slaughtered 16 to 17 days after oestrus followed by heifers slaughtered on days 24 to 26. The lowest pregnancy rate occurred in a group where pregnancy diagnosis was on day 42 by rectal palpation. The pregnancy rates of the highest and the lowest groups were significantly different. The pregnancy rate was increased in a group of heifers which were treated with human chorionic gonadotrophin from day 13 to 24 and palpated per rectum on day 42 to determine pregnancy. The presence or absence of penicillin and streptomycin in the medium and of passing differing volumes into the uterus after non-surgical transfer of single eggs using a glass pipette had no effect on pregnancy rate and there was no significant difference in pregnancy rate and there was no significant difference in pregnancy rate between the groups using different volumes of transfer media. The position of the egg within the uterine lumen after transfer contributes to the reduced pregnancy rate achieved after nonsurgical transfer when compared with the surgical method. The greatest proportion of embryonic death after non-surgical transfer occurs after day 17 and there is some evidence that human chorionic gonadotrophin treatment can improve embryo survival. The use of comparatively small volumes of medium to eject the egg into the uterus may be preferable to achieve maximum pregnancy rates.
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