In the past G.H. Kiracofe has collaborated on articles with M.E. King and W.J. McGuire. One of their most recent publications is Effect of stage of the estrous cycle on interval to estrus after PGF2α in beef cattle☆. Which was published in journal Theriogenology.

More information about G.H. Kiracofe research including statistics on their citations can be found on their Copernicus Academic profile page.

G.H. Kiracofe's Articles: (5)

Effect of stage of the estrous cycle on interval to estrus after PGF2α in beef cattle☆

AbstractEffect of stage of the estrous cycle at the time of prostaglandin F2α (PGF2α) (b) 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 PGF2α 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 PGF2α 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 PGF2α injection on either day 7 or day 14 declined linearly (P<.05) through 36 hours. Day of the estrous cycle at PGF2α 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 PGF2α injection were treated on days 5 through 8 of the cycle, indicating that PGF2α was less effective in regressing the corpus luteum between days 4 and 9 of the cycle than later in the cycle.

Synchronization of estrus in cyclic beef heifers with the prostaglandin analog alfaprostol☆

AbstractSeventy-eight Hereford-Angus crossbred heifers were injected intramuscularly twice with 6 mg of alfaprostolb in 6 ml of propylene glycol. On each representative day of a 20-day estrous cycle (estrus = Day 0), either three or four heifers received their first injection. The second injection was given 12 days after the first, regardless of the response to the first injection. Thirty-nine heifers were not treated. The first alfaprostol injection reduced serum progesterone to less than 1 ng/ml in all heifers injected after Day 4. A total of 79.5% (6278) of the heifers exhibited estrus by five days after the first injection. Average interval from injection to estrus was 63 hours. The second injection occurred on Days 6 through 16 for all but one heifer, with 75.6% (5978) falling on Days 8 through 11 of the estrous cycle. Estrus was detected in 93.6% (7378) of the heifers within five days after the second injection, with an average interval to estrus of 66 hours.Day of cycle at second injection did not affect the interval to estrus. Conception occurred in 79.4% (5873) of the heifers inseminated in the five days after the second injection. Occurrence of estrus and conception was no different in treated heifers after five days of the insemination period than in nontreated heifers after 21 days of the insemination period, where 94.9% (3739) were observed in estrus and 83.8% (3137) conceived. Overall percent conception for a 55-day insemination period was 89.7 (7078) for treated and 87.2 (3439) for nontreated heifers. Day of cycle at first or second injection did not affect conception after the second injection. Some signs of estrus were observed in 11 of the 16 heifers injected before Day 5.A second trial to determine if alfaprostol induced luteolysis early in the cycle was conducted. Twenty purebred Angus, Hereford, or Simmental heifers received either one or two injections of alfaprostol on either Day 1, 2, 3, or 4. Only five heifers showed any signs of estrus, and the three that were inseminated did not conceive. Subsequent cycle length indicated that luteolysis occurred in only one heifer.Data suggest that alfaprostol is an effective luteolytic agent in cyclic beef heifers after Day 4 and that two injections 12 days apart will effectively synchronize estrus in heifers when distributed throughout the cycle at the first injection without affecting conception rate.

Syncro-mate B® induces estrus in ovariectomized cows and heifers

AbstractEleven ovariectomized Hereford × Simmental cows and 10 ovariectomized crossbred heifers (primarily Angus and Hereford) were given the Syncro-Mate B (SMB) estrous synchronization treatment. The SMB treatment consisted of a 2 ml i.m. injection containing 5 mg of estradiol valerate and 3 mg of norgestomet plus a hydron ear implant containing 6 mg of norgestomet. The ear implant was removed 9 d later. Cows and heifers were considered in estrus only if they stood for mounting by a herdmate or a bull. Observations for estrus were made four or six times each day for 3 d after implant removal. The 21 animals were used in eight trials. Each trial involved 9 or 11 cows or 5 or 10 heifers. Four days to three weeks elapsed between implant removal and implant insertion for the next trial. No ovariectomized cow or heifer was observed in estrus for 21 d before treatment with SMB. In the eight trials, 3 of 9, 7 of 9 and 6 of 11 cows exhibited estrus, whereas 5 of 10, 1 of 5, 3 of 5, 3 of 5 and 5 of 5 heifers exhibited estrus after treatment. When data were pooled, 16 of 29 (55.2%) cows and 17 of 30 (56.7%) heifers exhibited estrus after treatment. Our data indicate that the SMB treatment can induce estrus in cows and heifers, independently of the ovaries.

Plasma LH and FSH after estradiol, norgestomet and Gn-RH treatment in ovariectomized beef heifers

AbstractPlasma luteinizing hormone (LH) first decreased then increased in a preovulatory-like fashion after administration of estradiol-17β (E) in ovariectomized heifers. However, in heifers implanted with norgestomet (N), a synthetic progestogen, an injection of E caused no preovulatory-like surge in plasma LH; only the suppression in plasma LH was noted. Injections of luteinizing hormone releasing hormone/follicle-stimulating hormone releasing hormone (Gn-RH) increased serum LH when given alone and in combination with either E, N, or N plus E. There was no evidence that the exogenous steroids blunted the ability of the pituitary to release LH in response to exogenous Gn-RH. Estradiol administered alone or in combination with N depressed plasma FSH. The implant of N alone had no significant effect on plasma FSH. Injections of Gn-RH stimulated only small increases in plasma FSH compared to LH, and no increase in plasma FSH was observed after E; rather, E alone or in combination with N depressed plasma FSH. The progestational block of E-induced LH release appeared to be the result of reduced endogenous secretion of gonadotropin releasing hormone because N did not blunt the ability of the pituitary to release LH in response to exogenous Gn-RH.

Reproductive characteristics of cyclic beef heifers treated with the prostaglandin analog luprostiol*

AbstractOne hundred and twenty crossbred Angus heifers, after exhibiting a 17- to 23-d estrous cycle, were placed into six groups of 20 heifers each and administered 2 ml i.m. propylene glycol containing either 0 (controls), 3.75, 7.5, 15.0 or 30.0 mg of luprostiol, or saline containing 0.5 mg cloprostenol (Groups 1 through 6, respectively). Heifers were observed for estrus every 6 h and all treatments were given 6.5 to 8.0 d after heifers were observed in standing estrus. Blood samples were collected after treatments from 10 heifers in each groups. Blood serum was assayed for progesterone. The synchronization period was considered to be 120 h after administration of luprostiol or cloprostenol. There were 0, 16, 17, 18, 20 and 18 heifers observed in estrus during the synchronization period in Groups 1 through 6, respectively. Progesterone concentrations in blood serum dropped below 1 ng/ml in 0, 8, 9, 10, 10 and 10 of the heifers from which blood samples had been taken in the six groups. All heifers observed in estrus were artificially inseminated. During the synchronization period, 0, 12, 14, 15, 16 and 10 heifers conceived in Groups 1 through 6, respectively. The interval from injection to estrus for the 89 heifers that exhibited estrus in the synchronization period averaged 49.0 h and was not different among the luprostiol and cloprostenol treated groups. Control heifers returned to estrus an average of 13.2 d after the treatment. The number of heifers that conceived at first insemination, regardless of when estrus occurred, was 16, 15, 16, 16, 16 and 12, and the total number that conceived at the first and second inseminations was 18, 18, 17, 19, 19 and 16 for Groups 1 through 6, respectively. Based on serum progesterone concentration and/or interval from treatment to estrus, 15 and 30 mg of luprostiol effectively regressed corpora lutea (100%) when administered between 6.5 and 8.0 d after estrus, and the estrous response and conception rate for these two groups equalled or exceeded that of the control and cloprostenol groups.

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