Induced and synchronized estrus in cattle: dose titration of estradiol benzoate in peripubertal heifers and postpartum cows after treatment with an intravaginal progesterone-releasing insert and prostaglandin F2alpha.

Abstract

Peripubertal beef heifers (n = 57) and postpartum multiparous cows (n = 52) were used to determine the optimal dose of estradiol benzoate (EB) to induce and synchronize estrus after treatment with intravaginal progesterone inserts (IVP4, EAZI-BREED CIDR). All females received an IVP4 for 7 d (d 0 = insertion day) with a 25-mg injection of PGF2alpha (Lutalyse) on d 6. At 24 to 30 h after IVP4 removal, females were randomly assigned to be injected subcutaneously with EB at the following doses: heifers 0, .2, .38, or .75 mg and cows 0, .25, .5, or 1 mg. Furthermore, seven heifers and seven cows from each dose group were bled every 4 h for 76 h starting at EB injection. Serum was collected and assayed for LH and estradiol-17beta (E2). Observations for signs of estrus were made twice daily for 21 d after removal of IVP4, and females were artificially inseminated 8 to 20 h after detection of estrus. The percentage of females showing estrous behavior was increased by EB (P < .04); the greatest response was at .38 mg in heifers (86%) and 1 mg in cows (100%). Dose x time interaction affected (P < .01) E2 concentrations in heifers and cows; the animals that received the higher doses of EB had greater E2 concentrations in a shorter time than those that received the smaller doses. The percentage of cows and heifers with an acute preovulatory LH release (peak LH) was affected by dose, with a linear (P < .01) and a quadratic (P < .01) response. Highest concentrations of LH during peak LH were affected by dose with a linear (P < .01) response in heifers and linear (P < .01) and quadratic (P < .08) responses in cows. Heifers receiving .38 mg and cows receiving .5 and 1 mg of EB had the highest peak LH. Time to LH peak had a linear (P < .03) response in heifers and had linear (P < .04) and quadratic (P < .05) responses in cows. Pregnancy rate was affected (P < .02) in heifers by whether or not they were anestrous before IVP4 treatment (those with estrous cycles = 52% vs those that were anestrous = 22%) and in cows by dose of EB (P < .01; 8, 23, 21, and 67% for 0, .25, .5, and 1 mg, respectively). In conclusion, in females treated with IVP4 and PGF2alpha to induce and synchronize estrus, an injection of EB increased concentrations of E2 and LH and increased number of animals showing estrus. Also, EB increased pregnancy rates in cows. Optimal responses were at .38 mg EB for heifers and at 1 mg EB for cows.

Comparison of an oestrus synchronisation protocol with oestradiol benzoate and PGF2α and insemination at detected oestrus to a timed insemination protocol (Ovsynch) on reproductive performance of lactating dairy cows

“…In another study Stevenson et al [27] detected only 40% of the cows in oestrus when using a similar synchronisation method. Administration of ODB one day after luteolysis may induce an LH surge and behavioural signs of oestrus in anoestrus cows [28]. Recent studies by Pancarci et al [29] and Stevenson et al [27] found that cows injected with 1 or 0.5 mg of ECP induced an LH surge in lactating dairy cows when given 24 h after a luteolytic dose of PGF 2α .…”

Estrous Synchronization using an Intravaginal Progesterone Device in Combination with GnRH or Estradiol Benzoate characterized by the Initial Ovarian Conditions in Japanese Black Cows

“…Presence of functional CL at CIDR insertion on d 0 correlated to a higher ovulation rate after CIDR removal on d 21 (with CL; 87.0% vs. without CL; 71.4%, P<0.05), but did not correlate to the conception rate (with CL; 45.2% vs. without CL; 39.0%). Lammoglia et al [9] reported significant differences in conception rates between CL presence (52%) and CL absence (22%) after 7 days of CIDR insertion with PGF 2α injection on d 6 and an additional EB injection at 24-30 hr after CIDR removal. On the other hand, there was another study which revealed no significant difference in pregnancy rates between cows with CL presence or CL absence (54% vs. 54%) [2].…”

“…Recently, various methods for estrous synchronization have been developed, such as single or double injection of PGF 2α [3], ovsynch program (GnRH -PGF 2α -GnRH) [11,13], and intravaginal progesterone with or without combination of other hormones [4,8,9,14]. Single or double injection of PGF 2α effectively regresses CL and induces estrus when injected into cows after d 5 of estrous cycle.…”

Synchronization of ovulation in crossbred dairy heifers using gonadotrophin-releasing hormone agonist, prostaglandin F2<FONT FACE=Symbol>a</FONT> and human chorionic gonadotrophin or estradiol benzoate

“…Estradiol benzoate in the absence of progesterone (<1.0 ng/ml) has been shown to induce an LH surge approximately 16 to 24 h after its administration (36). However, EB in the presence of a functional CL or when administered with exogenous progestagens decreases gonadotrophin secretion and induces atresia of the dominant follicle (37).…”