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H D Hafs

Publications and source records attributed to H D Hafs.

At least 37 records · Page 2Linked to original sources
PubMed1978

Estrus in relation to time of administration of prostaglandin F2alpha to heifers.

Holstein heifers (95) were given two injections of prostaglandin F2alpha, the first on day 0 and the second either at 0600 h or 1800 h on day 12. Interval from the second treatment to first observation of estrus did not differ between heifers treated during the morning (69.8 +/- 4.4 h) or evening (72.7 +/- 5.2 h). However, estrus was detected sooner after treatment of heifers during July 1975 (49 +/- 2 h) than after treatment during June 1976 (85 +/- 8 h). Estrus began at 64 +/- 5, 73 +/- 7, and 76 +/- 7 after the second injection during August 1975, October 1976, and December 1975. Heifers treated during the morning in October were detected in estrus sooner (57 +/- 3 versus 95 +/- 13 h) than those treated during the evening. An interaction of season by time may affect interval from prostaglandin F2alpha treatment to onset of estrus.

Animals↗
PubMed1977

Response of cyclic and post-partum suckled cows to injections of synthetic LH-RH.

Doses of 125, 250 or 500 micrograms LH-RH were injected i.m. into suckled beef cows on approximately Day 11 of an oestrous cycle synchronized by prostaglandin treatment. There was a positive linear relationship between dose of LH-RH and the area under the measured LH peak. Administration of 500 micrograms LH-RH as a single injection to suckled cows 13-32 days post partum resulted in LH release but failed to induce normal ovarian activity. A small transient rise in plasma progesterone for 6--9 days occurred at the expected time after injection in 50% of animals. Administration of 500 micrograms LH-RH to suckled beef cows approximately 20--30 days post partum and a second injection approximately 10 days later at the time when the resulting transient rise in plasma progesterone had returned to basal values induced normal cyclic activity (as shown by progesterone concentrations and observed oestrus) at 35 days compared with 70 days for untreated controls. Pituitary responsiveness to LH-RH, as assessed by LH levels, was found to increase up to 20 days post partum.

Animals↗
PubMed1977

Estrus, ovulation, and serum progesterone, estradiol, and LH concentrations in mares after an increased photoperiod during winter.

On December 11, 1974, 15 seasonally anestrous mares were assigned at random to 1 of 3 experimental groups: outdoor-control, indoor-control, or indoor light-treated (a 16-hour photo-period). This experiment was terminated on April 21, 1975. The five mares in the indoor light-treated group ovulated 59.0+/-6.9 days later, which was 74 days earlier (P less than 0.01) than 2 of the 5 outdoor-controls (the other 3 ovulated after April 21 during a subsequent experiment) and 50 days earlier (P less than 0.05) than the indoor-controls. Durations of the 1st estrus for the 3 groups of mares were 13.3+/-3.6, 8.4+/-2.0, and 6.0+/-1.0 days for the indoor light-treated, indoor-control, and outdoor-control groups, respectively. The indoor light-treated mares averaged 4.2 estrous cycles before April 21, the indoor-control mares averaged 1.4 estrous cycles, and 2 of 5 outdoor-control mares ovulated 1 time during the experiment. The peripheral blood luteinizing hormone (LH), estradiol, and progesterone concentrations were minimal during winter anestrous. The hormone changes normally associated with estrous cycle activity in mares--maximal estradiol and luteinizing hormone concentrations near ovulation and maximal progesterone concentration during diestrus--were observed in all mares beginning at the 1st estrus. Hair loss was observed earlier in the light-treated mares, than in either of the other groups. In conclusion, a 16-hour photo-period initiated in early December for anestrous brood mares caused endocrinologically normal estrous cycles to begin within 2 months. This may allow breeding and foaling considerably earlier than normally expected.

Anestrus↗
PubMed1976

Increased blood LH and testosterone after administration of prostaglandin F2alpha in bulls.

Two types of experiments were conducted to determine the relationship of changes in blood luteinizing hormone (LH) and testosterone in bulls given prostaglandin F2alpha (PGF2alpha). Episodic surges of LH and testosterone occurred in tandem, apparently at random intervals, on the average once during the 8-hr period after bulls were given saline. In contrast, after sc injection of 20 mg PGF2alpha, blood serum testosterone increased synchronously to a peak within 90 minutes four-fold greater than pre-injection values, and the testosterone surges were prolonged about three-fold compared to those in controls. Each of the PGF2alpha-induced surges of testosterone was preceded by a surge of blood serum LH which persisted for about 45 minutes and peaked at about 3 ng/ml. In a second experiment, PGF2alpha was infused (iv, 0.2 mg/min) for 20 hr; blood plasma testosterone increased from 7.0+/-0.6 to 16.0+/-1.5 ng/ml within 2.5 hr and remained near this peak for 10 hr. Then testosterone gradually declined to about 9 ng/ml at the conclusion of the 20-hr infusion. These changes in testosterone were paralleled by similar changes in blood plasma LH, although LH declined 3 hr earlier than testosterone. Random episodic peaks of blood plasma LH and testosterone typical of untreated bulls resumed within 8 hr after conclusion of PGF2alpha infusion. In both experiments, the surge of testosterone after PGF2alpha was preceded by increased blood LH. We conclude that increased LH after administration of PGF2alpha probably caused the increased testosterone. However the mechanisms of these actions of PGF2alpha remain to be determined.

Animals↗
PubMed1976

Some assay restrictions on inferences made from determining hormones in horses, cows, and their fetuses.

Often in developing hormone assays, hormones that may interfere with the assay by cross-reaction are not available for testing the validity of the assay. For example, horse TSH was unavailable to test for cross-reaction in an LH radioimmunoassay (RIA). The authors devised an indirect means of accomplishing the same goal, and the evidence from the indirect test of cross-reaction was at least as persuasive as a direct test might have been. Other examples are given of experiments where extensive effort was devoted to validation of steroid RIA, but there were substantial quantitative differences in the results among experiments and among laboratories. Differences of this kind probably would be intolerable in an assay used to monitor hormone residues in food-producing animals.

Animals↗