Browsing by Subject "ovulation"
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Item Effects of GnRH and prostaglandin combined with a short progestin regimen on the synchrony of estrus and ovulation in ewes during the breeding season(2012-08-10) Calhoun, Andy Kyle; Calhoun, Andy Kyle; Dickison, Will J.; Salisbury, Micheal; Scott, Cody; Keith, Susan; Angelo State University. Department of Agriculture.The lack of effective, consistent synchronization protocols for ewes is a barrier to the use of artificial insemination in sheep. This study compared the estrus and ovulation percentage and window of synchrony of estrus and ovulation for ewes synchronized with three experimental protocols. The industry’s current standard protocol using PG600, an 11 d CIDR and PGF2a was compared to two alternative protocols utilizing GnRH, a 7 d CIDR and PGF2a. Forty Suffolk ewes were divided into 5 groups and each group was placed on a different protocol. Blood sampling began 18 h following CIDR removal and samples were collected every 2 h for 19 consecutively collections. Mean serum concentrations of LH differed between groups (P<0.05) from 22-42 h following CIDR removal. The two protocols using the shorter 7 d progestin regimen and GnRH to control follicular dynamics resulted in higher estrus and ovulation rates and an acceptable window of synchrony.Item Efficacy of oral altrenogest for postponing ovulation in the mare(Texas A&M University, 2004-09-30) Murrell, Sandra LeeThe horse industry relies heavily on the breeding manager's ability to get a large number of mares bred each season. Therefore, it is beneficial to optimize use of the stallion and number of cycles per conception, both of which are related to the time of ovulation. Currently, methods exist to induce ovulation of a Graafian follicle; however there is no widely accepted method for delaying ovulation. Considering the main factors that lead to ovulation it could be hypothesized that the short-term administration of a progestin, such as altrenogest, would have the potential to postpone ovulation of a follicle that has reached ovulatory size. Twenty-six mares ranging in age from three to 23 y were paired by age and randomly assigned to a 2X4 blocked experiment. The factors were 1) stallion (Groups A-D) and 2) hormonal treatment (.044mg/kg BW altrenogest for 2 d) or control (Neobee M5 oil for 2 d). Hormonal administration for each mare was initiated upon detection of a follicle with a 35 mm or greater diameter. Mares were artificially inseminated starting on the first day of treatment and continuing every other day until ovulation was confirmed by ultrasonography. Blood samples were collected daily throughout the estrous cycle and at 12 h intervals from the detection of a 35 mm follicle until three days post-ovulation. Samples were analyzed for luteinizing hormone using a double antibody RIA, for progesterone and estradiol using RIA kits (Coat-A-Count? and double antibody, DPC?). Short-term altrenogest administration increased the number of days to ovulation (P<0.05). Mean days to ovulation from d 1 of treatment for the control versus treated mares were 3.15 d and 6.12 d, respectively. There was no difference (P=0.65) between control and treated groups with respect to size of follicle at the time of ovulation. Luteinizing hormone, progesterone and estradiol concentrations were analyzed during treatment until 3 d post-ovulation. Altrenogest treatment had no effect on LH, progesterone and estradiol concentrations as demonstrated by the lack of difference between control and treated mares (P=0.27, P=0.56, P=0.67). There was no difference in pregnancy rates (P=0.62) between the control 10/13 and treated 11/13 mares.Item Utilizing body temperature to evaluate ovulation in mature mares(Texas A&M University, 2006-08-16) Bowman, Marissa CoralThe equine breeding industry continues to be somewhat inefficient, even with existing technology. On average, foaling rates are low when compared with that of other livestock. One major contributor is the inability to accurately predict ovulation in mares, which ovulate before the end of estrus, leaving much variability in coordinating insemination. A more efficient, less invasive method that could replace or reduce the need for constant teasing and ultrasonography to evaluate follicular activity is needed. In both dairy cattle and women, a change in body temperature has been shown to occur immediately prior to ovulation. Research on horses has been limited, although one study reported no useable relationship between body temperature and ovulation in mares (Ammons, 1989). The current study utilized thirty-eight mature cycling American Quarter Horse mares, and was conducted from March-August 2004. Each mare was implanted in the nuchal ligament with a microchip that can be used for identification purposes, but is also capable of reporting body temperature. Once an ovulatory follicle (>35mm) was detected using ultrasonography and the mare was exhibiting signs of estrus, the mare's follicle size and temperature were recorded approximately every six hours until ovulation. Not only was the temperature collected using the microchips, but the corresponding rectal temperature was also recorded using a digital thermometer. A significant effect (p<0.05) on body temperature was noted in relation to the presence or absence of an ovulatory follicle (>35mm) under different circumstances. When evaluating the rectal temperatures, no significant difference was found in temperature in relation to the presence or absence of a follicle. However, in the temperatures obtained using the microchip, temperature was higher (p<0.05) with the presence of a follicle of greater than 35mm. This may be due to the extreme sensitivity of the microchip implant and its ability to more closely reflect minute changes in body temperature.