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931.
Gonadotropin releasing hormone (GnRH) treatment was examined as a means of improving the efficacy of embryo collection in the sheep following intrauterine insemination of frozen-thawed semen. In summary, treatment consistently improved fertilization rates and the number of fertilized ova collected per ewe was enhanced compared with untreated ewes. The yield of fertilized ova in ewes treated with follicle stimulating hormone (FSH) was maximized by administering GnRH 36 h after progestagen treatment; 24 h was the preferred time in ewes treated with pregnant mare serum gonadotropin (PMSG). There was a significant (P < 0.001) increase in the percentage of unfertilized ova in the former treatment when GnRH was given at 24 h. An examination of the time of insemination (0, 6, 12 and 18 h before the median time of ovulation) indicated that fertilization rates were highest when insemination occurred at 6 h in both GnRH-treated ewes and in untreated ewes. In GnRH-treated ewes, the recovery of ova was lowest when insemination occurred at the time of ovulation. The number of motile frozen-thawed spermatozoa required for fertilization following treatment was estimated to be approximately 20 x 10(6) per uterine horn. GnRH-treatment also improved the yield of fertilized ova in sheep that were naturally mated, although this yield was lower than that obtained with intrauterine insemination of frozen-thawed semen. It is concluded that fertilization failure, a major problem in sheep embryo collection, can be eliminated through judicious use of GnRH treatment and properly timed intrauterine insemination. 相似文献
932.
Luteolysis in the cow depends upon an interaction between prostaglandin F(2alpha) (PGF(2alpha)) and oxytocin. The objectives of our study were 1) to determine oxytocin concentrations in postpartum dairy cows and 2) to identify the temporal relationship between oxytocin and PGF(2alpha) release patterns during luteolysis in normal and abbreviated estrous cycles in the postpartum period. Serum oxytocin and PGF(2alpha) metabolite (PGFM) concentrations from nine cows which had short estrous cycles (< 17 d) were compared with those of six cows which had normal estrous cycles. Serum basal oxytocin concentrations in short estrous cycle cows (23.7 to 31.1 pg/ml) were higher (P<0.05) than those of normal estrous cycle cows (14.6 to 19.8 pg/ml). Oxytocin concentrations increased to peak values in both short and normal cycle cows, during luteolysis. Basal PGFM concentrations (112.2 to 137.4 pg/ml) were higher in cows with short cycle (P<0.05) than in cows with normal cycles (62.9 to 87.5 pg/ml). The increase in PGFM concentrations during luteolysis was significant in both normal cycle and short cycle cows (P<0.05). Increases in serum PGFM concentrations were always associated with increases in serum oxytocin concentrations in normal cycle and short cycle cows and the levels decreased simultaneously before the subsequent estrus. Results support the idea of a positive relationship between PGF(2alpha) and oxytocin concentration during the estrous cycle as well as a possible synergistic action of these hormones in the induction of luteolysis in dairy cattle. 相似文献
933.
Prepuberal gilts were treated with 750 IU pregnant mare serum gonadotropin (PMSG) followed 72 h later by 500 IU human chorionic gonadotropin (hCG) to induce follicular growth and ovulation. In this model, ovulation occurred at 42 +/- 2 h post hCG treatment. When 500 mug of cloprostenol was injected at 34 and of 36 h after hCG injection, 78% of the preovulatory follicles ovulated by 38 h compared with 0% in the control gilts. In addition, plasma progesterone concentrations were significantly higher in the cloprostenol-treated group than in the control group (P<0.01) at 38 h, indicating luteinization along with premature ovulation. These results suggest that prostaglandin F(2)alpha (PGF(2)alpha) or an analog can be used to advance, synchronize or induce ovulation in gilts. 相似文献
934.
Twenty multiparous Quarter Horse mares were assigned to one of two treatment groups at 40 to 75 d of pregnancy. Group 1 was the control group and the mares were fed to maintain a moderate degree of body fat (condition score 5.5 to 7). Group 2 was the obese group and the mares were fed to achieve (prepartum) and then maintain (post partum) an extremely high degree of body fat (condition score 9). Estrous intensity was evaluated using subjective teasing scores ranging from 0 (rejection) to 4 (maximum receptivity). Mares were artificially inseminated beginning with the second postpartum ovulatory cycle; the study was terminated after 63 d of pregnancy. Duration of estrus, maximum teasing score and the number of mares exhibiting overt estrus (teasing score > 2) did not differ between treatment groups during the first and second postpartum ovulatory cycles. The intervals from foaling to first cycle ovulation, foaling to second cycle ovulation, and first to second cycle ovulation were also similar between treatment groups. All mares in both treatment groups conceived and maintained pregnancy. The first cycle conception rate and the number of cycles per conception did not differ between treatment groups. A high degree of body fat produced by overfeeding during gestation did not adversely affect postpartum reproductive performance in the multiparous mare. 相似文献
935.
Six ovariectomized gilts were given zearalenone (Z), estradiol benzoate (EB) or vehicle in a replicated 3 x 3 Latin square design. Zearalenone was added to 2.3 kg of a corn-soybean ration at a dose of 1 mg Z/kg body weight; EB was given intramuscularly at 0.1 mg EB/kg body weight. Control gilts received vehicle solvent for both Z and EB. Blood samples were collected from indwelling jugular cannulas at 6-h intervals for 48 h before Z, EB or vehicle was given. After treatment, blood samples were drawn at 6-h intervals for an additional 84 h. Serum concentrations of luteinizing hormone (LH) decreased (P<0.001) from 4.67 ng/ml to 0.29 ng/ml within 6 h of EB. From 54 to 84 h after EB, serum concentrations of LH rose to 15.60 ng/ml (P<0.001). Serum concentrations of LH were reduced (P<0.001) in a similar pattern after Z (3.70 ng/ml to 0.49 ng/ml), but a rise in serum LH was not observed 54 to 84 h after Z (1.30 ng/ml). Serum concentrations of LH remained unchanged (P=0.55) in gilts given vehicle. Serum concentrations of follicle stimulating hormone (FSH) were suppressed (P<0.03) at 6 h in EB (19.10 vs 11.35 ng/ml) and Z gilts (16.16 vs 11.41 ng/ml) but remained unchanged in vehicle gilts. Serum concentrations of FSH did not change in EB or Z gilts during the next 36 h. These data indicate that the suppressive action of Z on serum concentrations of LH and FSH was similar to that of EB, while the biphasic stimulatory effect of EB for LH was not manifested by Z. 相似文献
936.
In a study of the time of ovulation following synchronization of estrus in the ewe, the effect of time of treatment with GnRH (24 vs 36 h after pessary removal) and dosage (6.25 to 100 ug per ewe) were examined. All treatments synchronized the time of ovulation irrespective of when untreated ewes commenced to ovulate. As part of an evaluation of GnRH treatment in artificial insemination programs, an assessment was made of the quality of eggs obtained from control ewes and ewes treated with GnRH at either 24 or 36 h after pessary removal. Treatment at 24 h increased the number of retarded embryos (P < 0.01) and unfertilized ova (P < 0.01) collected per ewe, reduced the number of embryos collected per ewe (P < 0.01), and reduced (P < 0.05) the percentage of pregnant ewes compared with other groups. However, there were no differences between control ewes and ewes treated with GnRH at 36 h. GnRH treatment at 36 h was consequently examined as a means of improving conception rates following the intrauterine insemination of frozen-thawed semen. Insemination of GnRH-treated ewes 8 to 12 h before the median time of ovulation resulted in a nonsignificant increase (range 5.7 to 7.3%) in the percentage of ewes of mature age which became pregnant. Insemination 0 to 4 h before the median time of ovulation resulted in a nonsignificant decrease in the percentage of pregnant ewes. GnRH treatment did not influence the number of fetuses per ewe. Reasons for the failure of this treatment to significantly improve ewe fertility are discussed. 相似文献
937.
938.
939.
940.
A total of 101 sows was used to examine postpartum progesterone levels and litter performance following administration of 15 mg prostaglandins F(2alpha) (PGF(2alpha) n = 48) given within 12 h after farrowing. Daily blood samples and rectal temperatures were taken from all sows during the first 3 d post partum. Plasma progesterone (P(4)) concentrations were determined by radioimmunoassay (RIA). Regardless of treatment, plasma P(4) levels for all sows decreased in a similar fashion over the 3 d sampled. Mean (+/- SEM) P(4) on Day 2 (0.55 +/- 0.06 ng/ml) and Day 3 (0.38 +/- 0.04 ng/ml) were lower (P<0.01) than on Day 1 (0.98 +/- 0.08 ng/ml). Rectal temperature did not differ between PGF(2alpha) treated and nontreated sows nor was it different over the days measured. Litter characteristics, including survival rates on Day 7 and at weaning, and body weight on Days 3 and 35, were not affected by treatment. It was concluded that PGF(2alpha) administration to sows within 12 h post farrowing had no affect on the rate of luteal regression, as determined by P(4) concentration, nor on subsequent litter performance. 相似文献