Comparison of the effects of gonadotropin-releasing hormone, human chorionic gonadotropin or progesterone on pregnancy per artificial insemination in repeat-breeder dairy cows.
ABSTRACT Three different treatments were compared to improve pregnancy per artificial insemination (P/AI) in repeat-breeder (RB) dairy cows. All cows (n=103) were assigned to one of four groups: (1) gonadotropin-releasing hormone (GnRH); (2) human chorionic gonadotropin (hCG); (3) once-used controlled internal drug release (CIDR) device; and (4) control. All treatments performed 5-6days after artificial insemination (AI) and milk samples were collected just before treatment for progesterone assays. There were no significant differences in milk fat progesterone concentration among trial groups. Cows were observed for estrus signs thrice daily. Pregnancy per AI on day 45 in hCG and CIDR groups were significantly higher than GnRH and control groups (60.0% and 56.0% vs. 26.9% and 29.6%, respectively), but there were no differences in P/AI between GnRH and control groups. There were also no significant differences between hCG and CIDR groups. Milk fat progesterone concentrations were compared between pregnant and non-pregnant cows in each group and only in the hCG group it was significantly lower in pregnant cows. In conclusion, treating repeat-breeder cows with hCG or once-used CIDR 5-6days after AI improved P/AI.
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ABSTRACT: This experiment was conducted to investigate the effects of different exogenous progesterone sources administrated after artificial insemination (AI) on serum progesterone (P(4) ) concentration and pregnancy rates in Holstein lactating cows. Sixty-four lactating Holstein dairy cows were allocated to four different treatments (n = 16 per treatment): the cows 1) were injected with physiological saline on days 5 and 13 after AI (control group); 2) were injected with progesterone on days 5 and 13 after AI (P group); 3) received controlled internal drug releasing device (CIDR) for a period from day 5 to 19 after AI (CIDR group); and 4) were injected with gonadotropin-releasing hormone (GnRH) agonist on days 5 and 13 after AI (GnRH group). Blood samples were collected on days 0 (AI day), 5, 13, 16 and 19 after AI to determine serum P(4) concentration. The results revealed a significant difference among treatment groups for serum P(4) concentration on days 13, 16 and 19 with the lowest concentration of serum P(4) for the control group. The pregnancy rate was also positively affected by all the treatments with CIDR having the greatest effect on pregnancy rate. Overall, the results indicated that CIDR has the greatest effect on serum P(4) concentration and pregnancy rate, although the administration of P and GnRH during days after AI increased serum P(4) concentration in lactating dairy cows as well.Reproduction in Domestic Animals 05/2011; 47(1):131-4. · 1.39 Impact Factor
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ABSTRACT: This study was designed to test the treatment with prostaglandin F2α (PGF2α) plus equine chorionic gonadotrophin (eCG) and GnRH 48 h later (PEG protocol) followed by fixed-time AI (FTAI) in dairy cows with silent ovulation (cows with a mature corpus luteum and no signs of estrus detected in the preceding 21 days). In Experiment I, ovulation following the PEG protocol monitored in 24 cows with silent ovulation was recorded in 83% of the cows 36 h after GnRH treatment. In Experiment II, control cows were artificially inseminated during spontaneous estrus (4615 AI), while cows in the PEG group (1266 AI) were subjected to FTAI 24 h after GnRH treatment. Binary logistic regression revealed a significant effect of the interactions of treatment by season, by parity or by repeat breeding syndrome (>3 AI) on the conception rate. The conception rate was negatively affected by the warm season and age in controls but not in treated cows, whereas repeat breeder cows in the control and PEG groups were less (by a factor of 0.7) or more (by a factor of 1.5) likely to become pregnant, respectively, than the remaining animals. Moreover, the likelihood of twin pregnancy was lower in multiparous PEG (by a factor of 0.4) cows than in the remaining cows. This protocol, besides overcoming the negative effects of heat stress and age on the conception rate, increased fertility in repeat breeder cows compared with spontaneous estrus. Moreover, this treatment regimen reduced the twin pregnancy rate in multiparous cows.Journal of Reproduction and Development 05/2013; · 1.76 Impact Factor