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摘要
The objectives were to evaluate the effect of human chorionic gonadotropin (hCG) administration 7 days (d) after insemination on the induction of accessory corpora lutea (ACL), the concentration of progesterone (P-4) in plasma, and on fertility of Holstein cows. Two hundred and four lactating Holstein cows were randomly assigned into two treatments: the cows in Ti (n=102) received 1,000 IU of hCG 7 d after insemination and the cows in T2 (n=102) received 2 mL of saline solution. On d 7 and 14 after insemination, blood samples from the jugular vein were collected to determine the concentration of P4 in plasma and on d 14, ovaries were scanned through ultrasound to evaluate the incidence of ACL, their diameter, perimeter, and area. P4 was determined using radioinmunoassay. The diagnosis of pregnancy was conducted by ultrasound on d 35 and 60 after insemination in cows that did not return to estrous. The incidences of ACL and pregnancy rates were analyzed through multiple logistic regressions whereas the diameter, perimeter, and area of corpora lutea and P4 concentration were analyzed through mixed models. P4 concentration on d 7 and 14 after insemination was similar (P>0.05) between treatments. The incidence of ACL was higher (P<0.01) in Ti (76.5%) than in T2 (8.8%). There were no differences (P>0.05) in the diameter, perimeter and area of ACL between Ti and 12(17.1 +/- 0.3 vs 17.4 +/- 0.8 mm; 65.9 +/- 1.3 vs 66.2 +/- 3.4 mm; and 299.9 +/- 10.9 vs 293.9 +/- 29.7 mm2, respectively). Similarly, there were no differences (P>0.05) in pregnancy rate between treatments on d 35 (53.9 vs 43.1%) and 60 (43.1 vs 35.3%), respectively. In conclusion, the administration of hCG 7 d after insemination induces the formation of ACL, without affecting their morphological characteristics, P4 concentration and the fertility of Holstein cows.
- 出版日期2015-10
