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Effect of estradiol subsequent to induced luteolysis on development of the ovulatory follicle and interval to estrus and ovulation
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Theriogenology EFFECT OF ESTRADIOL SUBSEQUENT TO INDUCED LUTEOLYSIS ON DEVELOPMENT OF THE OVULATORY FOLLICLE AND INTERVAL TO ESTRUS AND OVULATION D.P. Ryan, S. Snijders, A. Aarts and K.J. O’Farrell Department of Dairy Husbandry, TEAGASC, Moorepark, Fermoy, County Cork, Ireland.
Estrus synchrony subsequent to prostaglandin induced luteolysis is highly variable in lactating dairy cattle. The objective of this experiment was to evaluate the effect of estradiol treatment subsequent to induced luteolysis on development of the ovulatory follicle and the interval to estrus and ovulation. Forty-six lactating dairy cows, calved greater than 40 d were allocated at random to 1 of 3 treatments groups; Tl: (n=16) prostaglandin im (Lutalyse@, Upjohn, Ireland; 25 mg) on Day 8 of the estrous cycle; T2: (n=15> prostaglandin on Day 8 of the estrous cycle and 1 mg estradiol benzoate i.m. 24 h later; T3 : (n=15) prostaglandin on Day 8 of the estrous cycle and 1 mg estradiol benzoate i.m. 48 h later. Follicular development was monitored at 8hour intervals by ultrasonography with a 5 MHz probe (Aloka 500 SD, Japan) from Day 8 through the time of ovulation or Day 14 of the estrous cycle if The ultrasound images were recorded on ovulation failed to take place. videotape and retrospectively analysed to measure the ovulatory follicle. Heat detection was performed at 4-hour intervals and the time of ovulation was identified by transrectal ultrasonography at 4-hour intervals from the time of estrous detection through the time of ovulation. Follicular development during the 64-hour period subsequent to prostaglandin treatment or relative to the time of ovulation was not affected (P~0.10) by estradiol treatment. There was an overall linear increase in follicle size from the time of prostaglandin treatment through 64-hour, when the earliest ovulation was identified (follicle diameter = 19.1 + 0.59x mm; where x = the number of 8-hour intervals from 1 to 8) and during the 64-hour period prior to ovulation (follicle diameter = 23.3 - 0.19x mm). Ovulation occurred by 144 h after prostaglandin treatment in 14/16, 15/15 and 13/15 cows for Tl, T2 and T3, respectively. The intervals from prostaglandin treatment to estrus and ovulation (mean f SEM) were reduced (P < 0.05) following estradiol treatment 24 h after induced luteolysis in the T2 group (50.1 f 1.9 h, 79.5 i 1.6 h, respectively) compared with control females in the Tl group (60.0 + 2.0 h, 90.8 + 1.8 h, respectively) and those treated 48 h after induced luteolysis in the T3 group (62.6 f 2.0 h, 91.0 + 1.8 h, respectively). In conclusion, 1 mg of estradiol benzoate administered 24 h after prostaglandin treatment on Day 8 of the estrous cycle reduced the mean interval to estrus and ovulation in lactating dairy cows.
Theriogenology EFFECT OF ESTRADIOL SUBSEQUENT TO INDUCED LUTEOLYSIS ON DEVELOPMENT OF THE OVULATORY FOLLICLE AND INTERVAL TO ESTRUS AND OVULATION D.P. Ryan, S. Snijders, A. Aarts and K.J. O’Farrell Department of Dairy Husbandry, TEAGASC, Moorepark, Fermoy, County Cork, Ireland.
Estrus synchrony subsequent to prostaglandin induced luteolysis is highly variable in lactating dairy cattle. The objective of this experiment was to evaluate the effect of estradiol treatment subsequent to induced luteolysis on development of the ovulatory follicle and the interval to estrus and ovulation. Forty-six lactating dairy cows, calved greater than 40 d were allocated at random to 1 of 3 treatments groups; Tl: (n=16) prostaglandin im (Lutalyse@, Upjohn, Ireland; 25 mg) on Day 8 of the estrous cycle; T2: (n=15> prostaglandin on Day 8 of the estrous cycle and 1 mg estradiol benzoate i.m. 24 h later; T3 : (n=15) prostaglandin on Day 8 of the estrous cycle and 1 mg estradiol benzoate i.m. 48 h later. Follicular development was monitored at 8hour intervals by ultrasonography with a 5 MHz probe (Aloka 500 SD, Japan) from Day 8 through the time of ovulation or Day 14 of the estrous cycle if The ultrasound images were recorded on ovulation failed to take place. videotape and retrospectively analysed to measure the ovulatory follicle. Heat detection was performed at 4-hour intervals and the time of ovulation was identified by transrectal ultrasonography at 4-hour intervals from the time of estrous detection through the time of ovulation. Follicular development during the 64-hour period subsequent to prostaglandin treatment or relative to the time of ovulation was not affected (P~0.10) by estradiol treatment. There was an overall linear increase in follicle size from the time of prostaglandin treatment through 64-hour, when the earliest ovulation was identified (follicle diameter = 19.1 + 0.59x mm; where x = the number of 8-hour intervals from 1 to 8) and during the 64-hour period prior to ovulation (follicle diameter = 23.3 - 0.19x mm). Ovulation occurred by 144 h after prostaglandin treatment in 14/16, 15/15 and 13/15 cows for Tl, T2 and T3, respectively. The intervals from prostaglandin treatment to estrus and ovulation (mean f SEM) were reduced (P < 0.05) following estradiol treatment 24 h after induced luteolysis in the T2 group (50.1 f 1.9 h, 79.5 i 1.6 h, respectively) compared with control females in the Tl group (60.0 + 2.0 h, 90.8 + 1.8 h, respectively) and those treated 48 h after induced luteolysis in the T3 group (62.6 f 2.0 h, 91.0 + 1.8 h, respectively). In conclusion, 1 mg of estradiol benzoate administered 24 h after prostaglandin treatment on Day 8 of the estrous cycle reduced the mean interval to estrus and ovulation in lactating dairy cows.