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Biomedical subjects

G H Kiracofe

Publications and source records attributed to G H Kiracofe.

At least 37 records · Page 2Linked to original sources
PubMed1988

Factors associated with shortened estrous cycles after abortion in beef heifers.

Forty-six crossbred Hereford heifers were allotted into five experimental groups. Fenprotalene, a prostaglandin analogue, was administered to induce abortion and (or) to regress the corpus luteum (CL) in four groups of heifers about 75 d after conception. The four groups were 1) pregnant heifers, 2) pregnant heifers with the ovary contralateral to the gravid uterine horn removed 24 h after fenprostalene injection, 3) same as Group 2 but with the ipsilateral, rather than the contralateral, ovary removed and 4) heifers with uterus removed (ovaries intact) about 35 d after conception. A fifth group of nonpregnant heifers received implants containing norgestomet from 10 to 76 d after estrus and were given fenprostalene 24 h before removal of the implant. Average length of the first estrous cycle after the fenprostalene injection was 11.2, 8.3, 9.7 and 19.1 for Groups 1, 2, 3 and 5, respectively. Estrous cycles were longer (P less than .05) in norgestomet-treated heifers. Hysterectomized heifers (Group 4) did not exhibit a second estrus by 50 d after fenprostalene treatment; otherwise, all first estrous cycles after the fenprostalene injection were either "short" (7 to 13 d) or "normal" (17 to 23 d). Twenty-two of 24 heifers that aborted had short estrous cycles and two had normal estrous cycles. Short estrous cycles occurred after abortion regardless of whether the ovary ipsilateral or contralateral to the previously gravid uterine horn ovulated. Early regression of the CL (short luteal phase) did not occur in nonpregnant heifers after long-term progestogen stimulation or after hysterectomy, but it did occur in heifers with a previously gravid uterus.(ABSTRACT TRUNCATED AT 250 WORDS)

Abortifacient Agents↗
PubMed1987

Effect of charcoal-extracted porcine follicular fluid and 17 beta-estradiol on follicular growth and plasma gonadotropins in gilts fed a progesterone agonist, altrenogest.

Thirty-four gilts in two experiments were fed altrenogest for 18 d to block spontaneous growth of ovulatory follicles after luteolysis. They were injected with estradiol or charcoal-extracted porcine follicular fluid (pFF) to determine 1) whether gonadotropin secretion could be depressed and 2) whether exposure to reduced levels of gonadotropins would result in decreased numbers of medium follicles (3 to 6 mm in diameter). Gilts in Exp. 1 received treatments in a 2 X 2 X 2 factorial arrangement starting 48 h before the last feeding of altrenogest. Corn oil or estradiol (2 micrograms/kg body weight), 5 ml of charcoal-extracted porcine serum (pS) or pFF were injected im four times at 8-h intervals and gilts were sacrificed 24 or 96 h after last feeding of altrenogest. In Exp. 2, gilts received one of four treatments consisting of 1) pS, injected iv nine times at 8-h intervals starting 48 h before the last feeding of altrenogest; 2) pFF, with injection protocol the same as for pS; 3) estradiol injected im three times and 4) four times at 8-h intervals starting 0 and 24 h, respectively, before the last feeding of altrenogest. Compared with pS or corn oil, estradiol increased (P less than .001) plasma estrogen and decreased (P less than .05) plasma luteinizing hormone (LH) without a significant effect on plasma follicle stimulating hormone (FSH). Estradiol, compared with corn oil, decreased (P less than .01) the number of medium follicles from 24.8 to 0/gilt and decreased (P less than .05) the weight of ovarian follicular fluid from 4.2 to 2.1 g/gilt at 72 h after the first injection. Five milliliters of pFF had no significant effect on plasma gonadotropins or number of medium follicles. However, 20 ml of pFF, compared with pS, decreased (P less than .05) plasma FSH from 45 ng/ml to 9 ng/ml 32 h after the first injection, had no effect on plasma LH, decreased (P less than .01) the number of medium follicles from 29.2 to 2.2/gilt and decreased (P less than .01) follicular fluid weight from 3.9 to 1.6 g/gilt by 72 h after the first injection. These results indicate that estradiol or a non-steroidal component of follicular origin can decrease secretion of gonadotropins and suppress recruitment of medium follicles in the pig.

Animals↗
PubMed1986

Effect of forty-eight-hour calf removal, once- or twice-daily suckling and Norgestomet on beef cow and calf performance.

Trials were conducted in 1980 and 1981 to evaluate the effects of once-daily suckling, twice-daily suckling, 48-h calf removal, and Norgestomet on performance of spring-calving cows and their calves. Eighty-three and 73 Polled Hereford and 29 and 42 Simmental-cross cows were utilized in 1980 and 1981, respectively. Cows were allotted by age, breed, calving date and winter nutrition treatment to one of four groups: 1) once-daily suckle for 24 d starting 11 d before the beginning of the breeding season, 2) twice-daily suckle (same time frame as 1), 3) 48-h calf removal ending immediately before the breeding season, 4) calves remained with cows (controls). One-half.of each group was implanted with Norgestomet from 11 until 2 d before the start of the breeding season. Once- and twice-daily suckling increased (P<0.05) the percentage of noncycling cows showing estrus the first 3 wk after the start of treatment. Pregnancy rates for the breeding season were higher (P<0.1) in the once-daily suckle and 48-h calf removal groups for cows that had not exhibited estrus before the beginning of treatment. Norgestomet increased (P<0.05) the percentage of cows showing estrus within 3 wk after the start of treatment within the 48-h calf-removal and control groups. Milk production was not affected (P>0.1) by suckling treatment. Calf weight gains during suckling treatment were greater (P<0.05) in control and twice-daily suckled calves than in 48-h calf removal or once-daily suckled calves. Suckling treatment did not affect (P>0.1) adjusted weaning weights of calves or frequency and duration of suckling recorded 2 wk after the end of suckling treatment.

Journal Article↗
PubMed1986

Effect of energy intake after weaning on the sexual development of beef bulls. II. Age at first mating, age at puberty, testosterone and scrotal circumference.

Simmental and Hereford bulls were individually fed varying levels of the same diet to determine the effect of energy intake after weaning on rate of sexual development. For 200 d, 29 Simmentals were fed an average of 14.6, 19.2 or 23.8 Mcal and 27 Herefords were fed 13.4, 17.5 or 22.2 Mcal metabolizable energy per bull daily. Higher energy did not hasten sexual development, as measured by serum testosterone, age at first mating or age at puberty. As energy level increased, weight at puberty increased (P less than .05) for both breeds, and scrotal circumference at puberty increased (P less than .05) for Simmentals. When adjusted for breed and energy level, bulls that were heavier at 1 yr of age had larger scrotal circumference (P less than .05) and were younger at puberty (P less than .01). Bulls that had higher serum testosterone at 1 yr of age reached puberty earlier (P less than .01). At a constant age there was no relationship between testosterone and scrotal circumference. Although higher levels of energy increased scrotal circumference of Simmentals, it did not hasten sexual development for either breed.

Age Factors↗
PubMed1985

Suckling behavior in range beef calves.

The number and duration of suckling incidences were recorded during eight 24-h observation periods in a herd of spring-calving Polled Hereford and percentage Simmental cows in 1980 and 1981. The average number of suckling events per calf in 24 h was 5.0 +/- .1 and the average time spent suckling in 24 h was 46 +/- 1 min. Peaks in suckling activity occurred from 0500 to 0700, 1000 to 1300 and 1700 to 2100 h. The most suckling events in a single hour occurred between 0500 and 0600 h and the least between 2200 and 2300 h. Day of the estrous cycle did not influence the number or duration of suckling events. Cows that gave more milk nursed less frequently and heavier calves suckled less frequently (P less than .01). Age, breed and sex of the calf did not influence (P greater than .1) suckling frequency or duration.

Age Factors↗
PubMed1983

The effect of rearing environment on sexual behavior of young beef bulls.

Fifty-eight Polled Hereford bull calves were weaned at an average age of 196 d. They were penned individually after weaning and contact was limited to fenceline exposure to bulls in adjacent pens, except when grouped for weighing every 28 d. Six months after weaning they were allotted to one of the following 10-wk rearing treatments: 1) individually penned; 2) individually penned, but exposed to a heifer in estrus for 30 min every 2 wk; 3) group penned; 4) group penned, but each bull exposed to a heifer in estrus for 30 min every 2 wk. The week after allotment was designated wk 0. All 58 bulls, penned together after wk 12, had single-bull mating tests during wk 10, 22 and 32 and multi-bull mating tests during wk 12, 24 and 34. Mean serving capacity and mean serving efficiency were both greater (P less than .05) for individually-penned bulls than for group-penned bulls during the first single-bull and the first multi-bull mating test. No significant serving-capacity differences were present in subsequent single-bull or multi-bull mating tests, but serving efficiency was greater (P less than .05) for group-penned bulls in all subsequent tests, except the last multi-bull mating test. Mean serving capacity was greater (P less than .05), as was mean serving efficiency (P less than .01), for bulls in single-bull mating tests than for those in multi-bull tests. Exposure to heifers during rearing did not affect libido or mating ability.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Evidence for ovulation and fertilization in beef cows with short estrous cycles.

Calves were weaned from 15 Polled hereford anestrous cows 25 to 42 days after calving. In eight cows the uterus was flushed on day 6 or 8 after the first postweaning estrus (day 0), and in seven cows the oviduct ipsilateral to the ovary containing an ovulation papilla was removed and flushed on day 3. One ovum (morula) was recovered from the eight uterine flushings, while six ova were recovered from six of the seven oviductal flushings. Of the six, three were fertilized (4 to 8 cells), two unfertilized and only the broken zona pellucida of one was recovered. An ovulation papilla was observed in all cows at the time of oviduct removal. Six of the 15 cows had cycles less than 12 days, and from four of those six fertilized ova were recovered. The data indicate that previously anestrous cows ovulate at their first postweaning estrus and the ova released are capable of being fertilized. Failure to maintain pregnancy appears to be due to early corpus luteum regression.

Journal Article↗
PubMed1982

Effect of stage of the estrous cycle on interval to estrus after PGF(2alpha) in beef cattle.

Effect of stage of the estrous cycle at the time of prostaglandin F(2alpha) (PGF(2alpha)) injection on subsequent reproductive events in beef females was studied in four trials involving 194 animals. Cycling animals were given two injections of 25 mg PGF(2alpha) 11 days apart or, in some cases, the interval was altered to allow the second injection to fall on a specific day of the cycle. Day of estrous cycle at time of the second injection was determined by estrous detection. Interval from the second PGF(2alpha) injection to the onset of estrus (interval to estrus) was shorter (P<.01) in heifers than in cows. Both cows and heifers injected on days 5 to 9 (early cycle) had a shorter (P<.01) interval to estrus (estrus = day 0) than did those injected on days 10 to 15 (late cycle). Conception rate was lower (P<.05) for early-cycle heifers than for late-cycle heifers inseminated by appointment at 80 hours. There was no significant difference in conception rate of early-or late-cycle heifers or cows inseminated according to estrous detection or early- or late-cycle cows inseminated at 80 hours. Progesterone concentrations in blood samples collected in heifers at 4-hour intervals after the second PGF(2alpha) injection on either day 7 or day 14 declined linearly (P<.05) through 36 hours. Day of the estrous cycle at PGF(2alpha) injection had no effect on rate of progesterone decline, even though heifers injected on day 7 had a shorter (P<.05) interval to estrus. All animals whose cycle length was not affected by the second PGF(2alpha) injection were treated on days 5 through 8 of the cycle, indicating that PGF(2alpha) was less effective in regressing the corpus luteum between days 4 and 9 of the cycle than later in the cycle.

Journal Article↗
PubMed1982

Endocrine patterns in the postpartum beef cow associated with weaning: a comparison of the short and subsequent normal cycles.

Levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), progesterone and estradiol-17 beta were measured in five Polled Hereford cows. Blood samples were collected once or twice daily for 5 d, then every 6 h from 1 d before weaning (d 28 to 38 postpartum) until 10 d after the second postweaning estrus. Blood samples were again collected at daily intervals until the third postweaning estrus. All cows exhibited estrus within 4 d after weaning, a second estrus 8 to 10 d after the first and a third estrus 16 to 23 d after the second. All cows had peaks in serum concentrations of LH during the first (22.6 to 81.7 ng/ml) and second (4.4 to 149.0 ng/ml) postweaning estrus. Mean levels of LH in serum during the peak and the area under the LH curve during the first and second postweaning estrus did not differ. Serum levels of LH and FSH during the first 4 d of the short cycle did not differ from LH and FSH levels the first 4 d of the subsequent normal cycle. Levels of LH in serum for 4 d before the first LH surge, associated with the first postweaning estrus, did not differ from levels of LH found 4 d before the second Lh surge, associated with the second postweaning estrus. However, serum levels of FSH during the 4 d before the first ovulatory LH surge were lower (P = .05) than those observed during the 4-d period before the second ovulatory surge of LH. Progesterone levels were similar the first 6 d after the first and second estrous periods, but were lower after d 6 of the first (short) cycle than after d 6 of the second (normal) cycle. Estradiol peaks of 1.2 to 2.8 pg/ml were detected during the first postweaning estrus and 1.4 to 12.5 pg/ml during the second postweaning estrus, but due to the variability among cows mean levels of estradiol during first estrus did not differ from second estrus. These data agree with previous reports that postpartum anestrous cows had short cycles if they exhibit estrus in response to weaning. The early decline of progesterone after the first estrus apparently did not stem from lack of LH in serum, but the lower levels of FSH observed before this first ovulation may have been an important factor contributing to the reduced life span of the subsequent corpus luteum.

Animals↗
PubMed1980

Short estrous cycles and associated serum progesterone levels in beef cows.

Short estrous cycles in beef cows were investigated in two experiments. In trial 1, breeding dates from 2,854 fall-calving Angus cows were used to determine the incidence of short estrous cycles. Of 198 cycles of less than 17 days, 170 were between the first and second detected estrus. Estrous cycles of 7 to 10 days occurred more frequently (P<.005) than other short estrous cycles. Eight-day estrous cycles were most frequent. In the second experiment, calves were weaned from 25 of 33 anestrous spring-calving, crossbred Simmental cows. Compared to herdmates still nursing calves, an increased percentage of cows which had calves weaned were observed in estrus within 10 and 25 days after the date of weaning (P<.005) and a higher percentage had 7- to 10-day estrous cycles. Cows that were observed in estrus within 10 days after weaning were inseminated with Angus semen at their first estrus and with Simmental semen at their second estrus. No cows conceived on the first estrus of 7- to 10-day estrous cycles; 61.5% conceived on the second estrus. Serum progesterone was higher (P<.01) before the second estrus than the first.

Journal Article↗
PubMed1980

Effect of growth rate through 30 months on reproductive performance of beef heifers.

The effect of growth rate from birth through 30 months of age on the reproductive performance of Polled Hereford heifers calving as 2-year-olds was examined. Heifers with high gains during the first winter as weanlings had higher breeding efficiency when bred as year-lingins, had larger pelvic areas as 2-year-olds, gave birth to larger calves, had less calving difficulty at first parturition and had higher breeding efficiency at the subsequent breeding. Calf growth to weaning was positiviely related to first winter (weaning to yearling) gain of the dam. Heifers with high second winter gain had less calving difficulty at first parturition, slightly higher milk production and slightly higher breeding efficiency when rebred. Second winter gain of the dam had a high negative relationship with calf growth to weaning. Adequate growth from weaning to yearling was important for future production and reproduction through second breeding as 2-year-olds.

Animals↗
PubMed1980

Uterine involution: its role in regulating postpartum intervals.

An involuting uterus is a temporary barrier to fertility in cows, ewes and sows. Parturition is followed by a period when conception is not possible: about 1 week in sows and about 3 weeks in cows and ewes. Estrus and ovulation seldom occur together during this period and, if fertilization occurred and the embryo reached the uterus, placentation would be virtually impossible. The period of no fertility is followed by 2 to 3 weeks when fertility is possible, but not optimal. The extent to which the involuting uterus contributes to infertility during the second period is difficult to determine. Embryonic mortality in sows bred during this latter period appears to be a major cause of reduced litter size, so changes in uterine environment associated with involution may be essential for optimum fertility. Conception rate is lower up to 40 days after parturition than later in cows and ewes. Uterine involution appears not to be a barrier to fertility after 3 to 4 weeks postpartum in sows or 5 to 6 weeks postpartum in cows and ewes unless delayed by inflammation or infection.

Anestrus↗
PubMed1979

Synchronization of estrus in beef heifers with a norgestomet implant and prostaglandin F2alpha.

In a 5-year study (1973-1977), 281 cycling beef heifers were treated with a 7-day norgestomet (SC21009) ear implant and an intramuscular injection of prostaglandin F(2alpha) (PGF(2alpha)) at the time of implant removal or 24 hr before implant removal. Percentages of heifers in estrus by 36, 48, 60, 72, and 120 hr after implant removal were 32.4, 52.7, 71.6, 80.1, and 93.2, respectively. Onset of estrus occurred an average of 49.8 +/- 4.7 hr after treatment. Percentages of heifers in estrus 36 hr after treatment were 5.7 and 51.7 for those with a corpus luteum and those without a corpus luteum (or determined regressing by palpation) at implant removal, respectively. When PGF(2alpha) was injected 24 hr before implant removal, 55% of the heifers were in estrus by 36 hr after implant removal compared to 30% when PGF(2alpha) was injected at the time of implant removal; however, by 60 hr after implant removal the difference was 76% vs. 71%. First-service conception rates for synchronized and nonsynchronized heifers were 62.2% and 59.6%, respectively. During 1976 and 1977 heifers were checked for estrus every 4 hr and inseminated 2, 6, 10, 14, 18, 22, 26, or 30 hr after first detected to be in standing estrus. Conception rate was not significantly affected by time of insemination but tended to be higher for heifers bred 26 and 30 hr after first being detected in standing estrus (78.9% and 70.0% vs. average 59.2%). Treatment with a 7-day norgestomet implant plus a single injection of PGF(2alpha) 24 hr before or at implant removal appears to be a practical technique for synchronizing estrus in cycling heifers without affecting conception.

Journal Article↗
PubMedDate not supplied

Effects of heat-stress in rats, III. On pregnant rats, maternal organs and foetal tissues.

Exposure of intact and ovariectomized rats to high ambient temperature (34.4 degrees C, 60-65% relative humidity) resulted in reduction of their body weight, increased water consumption. The feed consumed which was lowered by 25% initially, did not alter later. Intact rats were also subjected to a still higher ambient temperature of 36.6 degrees C and 70 to 75% RH and the effects were observed. When compared with 'controls' no significant changes in the weights of ovaries or pituitary gland were seen due to heat stress in intact rats. But, the latter weighed heavier in ovariectomized rats. Adrenal glands were found enlarged and weighed more both in intact and ovariectomized rats. The average foetal weight due to high ambient temperature in intact rats was lower, but in ovariectomized rats it weighed more. Similarly, the average weight of the placenta was lower in intact rats but higher in ovariectomized rats due to thermal stress.

Adrenal Glands↗