1998, Number 3
Effect of hCG treatment at the time of artificial insemination on the corpus luteum function and the fertility of repeat-breeder Holstein cows
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ABSTRACTTwo experiments were conducted to evaluate whether the administration of human chorionic gonadotropin (hCG) at the time of artificial insemination (AI) influences the corpus luteum function and the conception rate in repeat-breeder Holstein cows. In Experiment 1,17 repeat-breeder cows were selected by the next criteria: these cows had to have been unsuccessfully inseminated at least 3 times, and should not have genital abnormalities. At the time of AI, the cows were divided in two groups, 8 cows were intramuscularly injected with 2 500 IU of hCG. Nine cows constituted the control group which was not treated with hCG. All animals were bled daily from day of insemination (day 1) to day 16 for progesterone determination. Progesterone concentrations were compared between groups by a variance analysis for repeated measures. In experiment 2, the results of 2538 inseminations of repeat-breeder cows, selected by the same criteria of experiment 1, were checked. Conception rates were compared by the X2 test between 211 cows treated with 2 500 UI of hCG at the time of AI, and with 2327 non treated cows. There were no statistical differences (P›O.O5)in progesterone concentrations between cows treated with hCG and the control ones on none of the evaluated days. Likewise, there were no differences (P›0.05) in the conception rate between cows treated with hCG (40.8%; 86/211) and the controlones (34.2%; 795/2327). It is concluded that the treatment with hCG at the time of insemination does not improve the Corpus luteum function nor the conception rate in repeat-breeder Holstein cows.
Ryan DT, Snijders S, Condon T, Grealy M, Sreenan J, O'Farrell KJ. Endocrine and ovarian responses and pregnancy rates in dairy cows following the administration of a gonadotrophin releasing hormone analog at the time of artificial insemination or at mid-cycle post insemination. Anim Reprod Sci 1994;34:179-191.