The safety of moxidectin 1% injectable anthelmintic (0.6 mg/kg of body weight, 3 times the recommended dose) was evaluated in 145 reproductively sound, beef cows undergoing estrous cycle. Five treatment groups received moxidectin 1% injectable at specific times relative to a synchronized estrus (day 0): preovulatory treatment (day -2, treatment group 1), treatment at ovulation (day 0, group 2), and treatment after ovulation (days 7, 14, and 28, group 3, 4, and 5, respectively). Two groups of control cows received an injection of vehicle only at times corresponding to treatment in the other groups (6 at days -2, 7, and 28; 7 at days 0, 7, and 14). A final control group (8) received neither product or vehicle. Adverse clinical reactions were not observed in moxidectin- or vehicle-treated cows. Cows were bred by artificial insemination between days -2 and 25 and, subsequently, by breeding-sound bulls through day 65 of the study. Treatment and control groups did not differ in pregnancy rate or time to conception. Moxidectin (at 3 times the therapeutic dose) did not have deleterious effects on cow reproductive performance as examined (eg, at folliculogenesis, ovulation, and the early embryonic phase of development).

Immunoreactivity for 28 kd vitamin D-dependent calcium-binding protein (calbindin-D28k) has been localized in the germinal epithelium and cells surrounding oogonia and oocytes (future granulosa cells) of developing and growing ovaries of chicken embryos. The protein first appeared prominently in the germinal epithelium of the developing left ovary in 8-day embryos. At the twelfth day of incubation, cells surrounding oogonia and oocytes reacted intensely for calbindin-D28k. The number and intensity of calbindin-D28k-containing cells increased in both types of cells as the embryos further developed. Calbindin-D28k remained in the germinal epithelium throughout the study period observed (up to 10 weeks). However, the protein was present transiently in the future granulosa cells. It gradually decreased after hatching, and was virtually absent from granulosa cells in a 10-week old chicken. Compared with the known process of onset of sexual development, these results indicated possible involvement of calbindin-D28k in the early phases of oogenesis in chicken ovaries.

Histomorphometric and scanning electron microscopic analyses were performed on 74 embryos and fetuses and 20 sheep (early postnatal to adult age). Histologic differentiation of the omasum took place at 33 days of fetal life, with the appearance of first-order laminae. Second-, third-, and fourth-order laminae appeared at 39, 50, and 59 days, respectively. Neutral mucopolysaccharides first appeared in epithelial cells at 46 days of fetal life, decreasing quantitatively until birth, before subsequently stabilizing in postnatal life. Acid mucopolysaccharides, mucins, and mucoid compounds were not detected. Growth curves and formulas were constructed for each tissue layer. Initial tests involved multiplicative (y = axb), exponential (y = EXP [a + bx]), linear (y = a + bx), and polynomial models [y = a + bx + cx(2) + dx(3)].

Development of 1- to 2-cell in vivo fertilized equine embryos cultured with or without uterine tubal epithelial cells (UTEC) was studied. One- to 2-cell embryos (n = 26) were collected surgically from the uterine tubes of pony mares 1 day after ovulation. Four- to 8-cell embryos (n = 9) were collected 2 days after ovulation. Presumptive zygotes and 2-cell embryos were cultured with (n = 17) or without (n = 9) UTEC, and all 4- to 8-cell embryos were cocultured with UTEC as positive controls. Uterine tubal epithelial cells were used as cell suspensions within 2 weeks after initiation of cultures. Embryos were cultured to blastocysts or until the embryo had morphologic degeneration. Six presumptive zygotes failed to cleave in vitro. Development to blastocysts of 1-cell (4 of 11) and 2-cell (2 of 6) embryos cocultured with UTEC was similar. Coculture of 1- to 2-cell embryos with UTEC significantly (P = 0.05) improved development to blastocysts, compared with culture in medium alone (35 vs 0%, respectively); however, development to blastocysts of 1- to 2-cell embryos cocultured with UTEC was less (P < 0.025) than that of 4- to 8-cell embryos cocultured with UTEC (35 vs 89%, respectively).

Albendazole, administered orally at a dose rate of 25 mg/kg of body weight to presumed pregnant cows or heifers on days 21, 31, 41, 51, and 61 of gestation, did not induce toxicosis in embryos or fetuses, and all calves born were structurally normal. Albendazole administration at a rate of 25 mg/kg to cows at 7 and/or 14 days of gestation decreased the apparent conception rate (ie, embryolethality), but did not have a teratogenic effect. Apparent embryolethality was greater in cows administered 25 mg/ kg only on day 14, compared with those administered the drug only on day 7. Single dosage of 25 mg/kg given in the final 3 months of gestation did not induce abortion. There were no adverse effects of albendazole at a dosage of 10 or 15 mg/kg on developing embryos or fetuses when administered to presumed pregnant cows at various times in early gestation.

Histomorphometric and scanning electron microscopic analyses were carried out on 74 embryos and fetuses and 20 sheep (early postnatal to adult age). Histodifferentiation of the rumen took place at 33 days of fetal fife. Ruminal pillars were observed at 42 days, and at 61 days, ruminal papillae appeared as evaginations of the epithelial stratum basale. Neutral mucopolysaccharides first appeared in epithelial cells at 46 days of fetal life; thereafter, numbers decreased gradually and subsequently stabilized in postnatal life. Acid mucopolysaccharides, mucins, and mucoid compounds were not detected. Age and diet were recognized as factors that determine the structure of the ruminal mucosa. Growth curves and formulas were set out for each tissue layer.

Ultrasonography was used to determine whether there is embryo reduction in mares iwth unilaterally fixed twins when a major portion of the vascularized area of the wall of one of the embryonic vesicles is in apposition with the wall of the adjacent vesicle, rather than with the endometrium (deprivation hypothesis). In addition, the effect of ovulatory pattern (synchronous and asynchronous) on the incidence of embryo reduction was studied. Twin vesicles were ultrasonically detected on days 11 to 15 (ovulation = day 0) and were examined daily until there was embryo reduction or until day 40. In 31 mares with twin embryonic vesicles, unilateral fixation (71%) was more frequent (P less than 0.05) than was bilateral fixation (29%). In 28 mares with known ovulatory patterns, synchronous ovulations did not affect the type of fixation (9/17 unilateral and 8/17 bilateral); however, for asynchronous ovulators the frequency of unilateral fixation (10/11) was greater (P less than 0.01) than the frequency of bilateral fixation (1/11). The incidence of embryo reduction was greater (P less than 0.01) for unilateral fixation (14/19) than for bilateral fixation (0/9) and was greater (P less than 0.05) for asynchronous ovulators (9/11) than for synchronous ovulators (5/17). In mares with embryo reduction, the reduction was complete before detection of both embryo propers (early reduction) in 10/14 and after detection of both embryo propers (late reduction) in 4/14. For 17 synchronous ovulators, fewer underwent early embryo reduction (0 mares) than late reduction (5 mares) or no reduction (12 mares; 4 unilateral and 8 bilateral), whereas in the 11 asynchronous ovulators, more underwent early reduction (8 mares) than late reduction (1 mare) or no reduction (2 mares; 1 unilateral and 1 bilateral; P less than 0.01). In mares with early embryo reduction, the orientation and spatial relationship of one vesicle relative to the other was not determinable until the embryo proper was detected. In the 2 mares in which the embryo proper of the survivor was detected before embryo reduction was complete, the embryo proper was located opposite to the site of reduction, ie, the vesicle that was to be eliminated impinged on the thin-walled area of the yolk sac wall of the survivor. The position of the embryo proper and its emerging allantoic sac seemed to determine whether a given conceptus survived or underwent late embryo reduction. The embryo proper, the vascularized wall of the yolk sac adjacent to the embryo proper, and the emerging allantoic sac were exposed to the endometrium (uterine lumen) in the surviving vesicles; in the vesicles that underwent reduction, much of the corresponding area of the vesicle wall was covered by the wall of the adjacent survivor. The results supported the deprivation hypothesis.