The importance of uniform development of blastocysts was examined by comparing the effects of asynchronous superinduction (Day 6 embryos into Day 7 pregnant recipients and Day 7 embryos into Day 6 pregnant recipients) on the range of embryo development at Days 12 and 13 to subsequent survival to Day 30. Twenty gilts were used to produce five Day 7 recipients that received Day 6 embryos and five Day 6 recipients that received Day 7 embryos. Embryos from the Day 7 and Day 6 recipients were examined 6 days later. Recovered embryos ranged morphologically from spherical to filamentous blastocysts. This range of embryos was within the limits of that previously observed for naturally mated sows. However, recovered blastocysts from the Day 6 embryos transferred into Day 7 recipients were morphologically more variable and proportionately less developed than the blastocysts from the Day 7 embryos transferred into Day 6 recipients. Forty additional gilts were subsequently utilized to generate 20 recipients (10 recipients per transfer group) that were examined on Day 30. More Day 7 embryos transferred into Day 6 recipients survived (p less than 0.05) than Day 6 embryos transferred into Day 7 recipients. These experiments suggested that greater variation in early development of embryos, within litters, subsequently resulted in greater mortality of embryos.
Forty crossbred gilts were used in three experiments to examine the effects of estradiol on embryo migration. Small, spherical beads of Silastic glue containing either cholesterol or estradiol-17 beta were used to mimic embryo migration. In the first experiment, 10 cholesterol- and 10 estradiol-impregnated beads were injected into the tip of the uterine horns, either on the same side (n = 5) or opposite from each other (n = 5). The second experiment consisted of a localized release of cholesterol or estradiol and observing migration of cholesterol-containing beads inserted 10 cm anterior and posterior to this site (n = 5). In the third experiment, 10 cholesterol-impregnated beads were injected into either the tip or base of one uterine horn. Additionally, these gilts were exposed to vehicle or exogenous estradiol in a 2 X 2 factorial arrangement of treatments (n = 5). Results of these experiments indicated that cholesterol-impregnated beads migrated further (P less than .05) when adjacent to estradiol-containing beads than when in an opposite uterine horn. Localized release of estradiol failed to induce movement of beads away from the site of steroid release. Finally, beads inserted at the base of the uterus moved anteriorly following treatment of gilts with estradiol. We suggest from these experiments that the porcine uterine horn cannot discriminate between estradiol- and cholesterol-releasing beads and, further, lacks a coordinated ability to displace adjacent beads. A site-dose dependent mechanism(s) of estrogenic induction of migration may exist such that porcine embryos become bilaterally intermixed following posterior, then anterior, waves of uterine contractions.
Thirty-two cows were inseminated near the uterotubal junction at various stages of the estrous cycle and slaughtered 16 h later to determine the effects of stage of the estrous cycle and tubal site of sperm recovery on the frequency of acrosome-reacted bull spermatozoa. Slaughter times were 46, 70, 144, or 168 h after each cow was injected with prostaglandin (PG) F 2 alpha or during the luteal phase of the estrous cycle. Sperm were recovered from the upper uterus and the isthmus and ampulla of the oviducts and stained for both viability and acrosome reaction. The highest frequency of acrosome-reacted sperm was found in the ampulla ipsilateral to a dominant follicle (largest follicle present) or recent ovulation and primarily at 70 h after PGF2 alpha (P less than 0.05). Also, fewer sperm were acrosome reacted prior to (46 h post-PGF2 alpha) and well after (168 h post-PGF2 alpha) estrus than during or immediately postestrus (70, 90, and 144 h post-PGF2 alpha; P less than 0.05). Except for two cows, one at 46 h and one at 70 h, all cows with more than 50% acrosome-reacted sperm in the ampulla had ovulated before slaughter. These data suggest that capacitated sperm become localized in the ampulla of the oviduct of the ovulatory side around the time of ovulation.
Forty-eight sows were partially hysterectomized on day 10 (day 0 = 1st day of oestrus) of the oestrous cycle such that the isolated-contralateral ovary received either an ovarian or an ovarian and uterine blood supply. These two treatments were examined for their ability to affect corpora lutea (CL) function when 10,
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