Factors related to early pregnancy recognition in the woman.

PURPOSE: While the precise timing of the maternal recognition of pregnancy is not known, it is known that the prevention of return to ovarian cyclicity relies on a conceptus-derived signal. METHODS: In an attempt to identify the first luteotropic signals detectable in the maternal circulation, a sensitive Leydig cell luteotropin bioassay was employed, and data were compared for nine clinically pregnant and nine nonpregnant patients in an in vitro fertilization program. Blood samples were drawn every other day for 10 days after embryo transfer (ET). RESULTS: The first detectable rise in bioactive luteotropin levels occurred between 6 and 8 days post ET. Serum E2 levels increased on the same days. Differences in luteotropin levels between pregnant and nonpregnant patients were significant between days 6 and 8 (P < 0.0001) and between days 8 and 10 (P < 0.002). CONCLUSIONS: Based on morphological studies reported by others, bioactive luteotropic signals identified in this study were detectable in the maternal circulation at about the time of trophoblast lacunae coalescing with maternal uterine blood vessels.

Superovulation of cattle with equine pituitary extract and porcine ESH.

Superovulation has been practiced in cattle for more than 50 years but the results have been highly variable. Scientists at six locations compared a horse pituitary extract (HAP) with a single batch of porcine FSH (pFSH) to determine the efficacy of these hormones to induce superovulation and to test for variability in the superovulatory response. Acetone-dried equine pituitaries were suspended in 40% ethanol containing 6% ammonium acetate, and the supernatant was mixed with 2.5 volumes of cold ethanol. The resulting precipitate was washed with cold ether and dried. Total doses of 18 mg of HAP and 36 mg of pFSH were injected intramuscularly (i.m.) over 4 days, two injections per day, and prostaglandin (PGF(2)alpha; 25 mg, i.m.) was administered on Day 3. Injections were begun on Days 6 to 13 of the estrous cycle. The overall ovulation rates (mean +/- SEM) for HAP and FSH were 8.8 +/- 0.7 and 15.1 +/- 1.0, respectively (n=231; P<0.01). Location interacted (P<0.01) with the type of gonadotropin for the ovulation rate. When expressed as a proportion of the number of corpora lutea, the total number of embryos recovered was greater (P=0.03) for pFSH than for HAP, but there was no difference in the number of Quality 1 and 2 embryos. The results show that HAP can induce a satisfactory superovulatory response, but there was no evidence of reduced variability of response to HAP compared with pFSH.

Nulliparous versus primiparous crossbred females for beef.

Feedlot and carcass traits of nulliparous and primiparous females representing eight breed types, including Bos taurus and Bos indicus x Bos taurus crosses, were evaluated. Nulliparous females (heifers) were in the feedlot for 4 mo; primiparous females (heiferettes) were fed for 2 1/3 mo after their calves were weaned at 6 mo of age. Heifers averaged higher (P less than .01) in dressing percentage, percentage of kidney fat, carcass grade (P less than .10), and color of lean (P less than .05) compared with heiferettes. Heiferettes exceeded the nulliparous group in feedlot ADG (P less than .01), fat thickness (P less than .05), and percentage of steak, roast, and bone (P less than .01). Parity effects on carcass weight, longissimus area, marbling, pH, and shear force value were not statistically significant. Dam breed types differed in several traits, including marbling (P less than .05) and percentage of steak (P less than .10), roast (P less than .01), and bone (P less than .01). Dam breed x parity interactions were nonsignificant. Results show that beef derived from heiferettes is competitive with heifer beef.

Life-cycle evaluation of Bos taurus and Bos indicus X Bos taurus breed types in a dry, temperate climate: performance of mature dams.

Mature dams representing Hereford, Red Poll, F1 Hereford x Red Poll, F1 Red Poll x Hereford, F1 Angus x Hereford, F1 Angus x Charolais, F1 Brahman x Hereford and F1 Brahman x Angus breed types were evaluated. All cows were bred to Limousin sires to produce two-way or three-way-cross progeny. Mature Brahman x Hereford dams produced a higher (P less than .05) percentage of live calves than Herefords, but dam breed differences in percentage of calves weaned relative to the number of cows exposed for mating were not statistically significant. Progeny of Angus x Charolais and Red Poll dams were outstanding in weaning weight, but Hereford and Brahman-cross calves were below average. Planned comparisons showed that Angus x Charolais calves were heavier (P less than .01) at weaning than Hereford (23.0 +/- 3.8 kg) or Angus x Hereford (9.6 +/- 3.2 kg) progeny. Mature Angus x Hereford mothers weaned heavier calves than did Brahman x Herefords (7.4 +/- 3.2 kg, P less than .05) or Brahman x Angus (10.9 +/- 3.0 kg, P less than .01). Analysis of the Hereford-Red Poll diallel showed evidence of maternal heterosis in calf weaning weight (4.0 +/- 2.6 kg, P less than .05), but there was no difference in the percentage of calves weaned by crossbred vs straightbred dams.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro fertilization (IVF) of mouse ova in HEPES-buffered culture media.

Some major drawbacks of a bicarbonate-buffered culture medium include the requirement of an elaborate incubator system able to maintain a 5% CO2 environment and the inability of the culture medium to maintain a physiological pH range (pH 7.3-7.4) in room air (0.03% CO2). This work resulted in the development of IVF culture media, BB (modified T6) and Hams-HEPES, which use HEPES-buffered systems not requiring the specialized CO2 environment to maintain a physiological pH range in room air. These media generate above-average cleavage rates in in vitro fertilized, superovulated B6CBAF1 mice ova. The effect of heparin and HEPES on cleavage was studied and neither had a significant effect at the concentrations used. Cleavage rates of nonfertilized ova (parthenogenic division) were 9 to 13%. There was no significant difference in parthenogenesis between any of the culture media and it appears to be a function of the strain of mice and the timing between human chorionic gonadotropin (hCG) injection and ovum collection. These results emphasize the need to account for parthenogenesis when determining cleavage rates of in vitro fertilized mouse ova. Also, the results suggest that because of individual mouse differences in cleavage rates, it is important to use an adequate number of mice per group to determine an accurate, average cleavage rate.

Sequential uterine horn versus simultaneous total uterine flush to recover bovine embryos nonsurgically.

Beef cows were superovulated with follicle stimulating hormone (FSH) to compare two nonsurgical methods of embryo recovery from the uterus. In the first method each uterine horn was independently flushed with physiological saline solution (PSS) through a Foley catheter passed through the cervix and into the uterine horn. In the second method both uterine horns were simultaneously flushed with PSS by passing the catheter into the uterine body. In both methods, the numbers of ovulations were determined after embryo collection by counting the corpora lutea (CL) on both ovaries of each cow through a flank incision. Independent flushing (n = 19) averaged 6.4 embryos and 16.1 CL per cow for a recovery rate of 40%. Simultaneous flushings (n = 22) averaged 5.4 embryos and 17.7 CL per cow for a recovery rate of 31%. This difference between the recovery rates of the two flushing methods was not significant (P>0.05).

Influence of follicular components on oocyte meiosis in vitro.

Oocytes and follicular components obtained from ovaries recovered from mature Hereford cows at slaughter were used to determine follicular influence on oocyte maturation. Some oocytes were fixed immediately to determine the stage of maturation. The remaining oocytes were cultured for 32 to 34 hr in various environments to determine the influences of the granulosum and follicular fluids on meiotic changes. All noncultured oocytes had dictyate nuclei except one in premetaphase. Oocytes cultured in 50 or 100% follicular fluid or in contact with stratum granulosum cells showed some meiotic inhibition both before and after germinal vesicle breakdown (GVB). The least resumption of meiosis occurred in oocytes cultured in their intact follicles.

Maternal characteristics of young dams representing Bos taurus and Bos indicus x Bos taurus breed types.

Reproductive traits and preweaning growth of progeny from young Hereford, Red Poll, Hereford X Red Poll, Red Poll X Hereford, Angus X Hereford, Angus X Charolais, Brahman X Hereford and Brahman X Angus dams were evaluated. First-calf heifers were mated with Red Angus bulls; Santa Gertrudis sires were used for each cow's second and third breeding season. Herefords, Red Polls and Hereford-Red Poll crosses were below average in percentage of calves weaned, whereas Angus-sired and Brahman-sired dams exceeded the overall mean. Angus X Charolais (P less than .10), Brahman X Hereford (P less than .01) and Brahman X Angus (P less than .10) dams weaned a higher percentage of calves than straightbred Herefords. None of these breed types differed from young Angus X Hereford females in reproductive performance. Angus X Charolais calves ranked highest in 180-d calf weight, exceeding progeny from both Hereford (P less than .01) and Angus X Hereford (P less than .10) dams. Brahman X Hereford dams weaned heavier (P less than .05) calves than Herefords, but their progeny did not differ at weaning from those reared by Angus X Herefords. Calves from Brahman X Angus dams weighed 12.7 kg less (P less than .01) than Angus X Hereford progeny. Analysis of the Hereford-Red Poll diallel showed evidence of (P less than .10) maternal heterosis in 180-d calf weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Onset of puberty in heifers of diverse beef breeds and crosses.

Puberty traits of straightbred and crossbred heifers (n = 301) were evaluated under pasture conditions. Breed groups represented were straightbred Hereford and Red Poll, reciprocal crosses of these two breeds, Angus X Hereford, Angus X Charolais-Cross, Brahman X Hereford and Brahman X Angus. Breed group was an important (P less than .01) source of variation in heifer weights and in age at puberty. Straight-bred Red Poll and Red Poll cross heifers were youngest at puberty, Angus X Hereford and Angus X Charolais-Cross were intermediate, and straightbred Hereford and Brahman crosses were oldest at the onset of puberty. At the beginning of their first mating season at 19.5 mo of age, 96% of the straightbred Red Polls, 95% of Red Poll crosses, 81% of Angus X Herefords, 89% of Angus X Charolais-Crosses, 68% of straightbred Herefords, 48% of Brahman X Herefords and 74% of the Brahman X Angus had attained puberty. Results of a diallel analysis of Hereford-Red Pool matings indicated that maternal influence of the Red Poll breed was superior (P less than .01) to Herefords for body weight up to 24 mo of age and incidence of puberty at 11.5 mo. Red Polls also exceeded Herefords in direct effects for puberty percentage at 11.5, 15 and 19.5 mo of age. Heterosis was significant for puberty percentage and weight. Breed group differences in pregnancy rate at 24 mo were not significantly.