Three trials involving 128 heifers were conducted to determine whether norgestomet implants administered during the mid- and late luteal phases after breeding could be used to synchronize a second estrus in nonpregnant, inseminated heifers without adversely affecting pregnancy in pregnant heifers. All heifers were initially synchronized with Syncro-Mate B and artificially inseminated 47 h after...

Two experiments were conducted with bulls administered norgestomet and gonadorelin to determine if the gonadorelin-induced release of testosterone could be developed into a biological assay for quality assurance of gonadorelin. Implants containing norgestomet (0 to 36 mg) reduced the episodic release (r = -.81; P < .05) and mean concentrations of testosterone (r = -.82; P < .05). Gonadoreline-i...

In Exp. 1,101 suckled beef cows were administered two injections of prostaglandin F2 alpha (PGF2 alpha) 11 d apart. Cows in Group 1 received no additional treatment. Cows in Groups 2 and 3 received 250 micrograms of GnRH plus 47-h calf removal. Cows in Group 3 also received a norgestomet ear implant that was inserted 4 d after the first PGF2 alpha injection and left in situ for 8 d. The second ...

The objective of this study was to determine whether there were doses at which the synthetic progestin, norgestomet, could mimic midluteal phase concentrations of progesterone in regulating the secretion of LH and 17 beta-estradiol in bovine females. Heifers were randomly assigned to one of five groups to receive: 1) one (1Norg, n = 5), 2) two (2Norg, n = 5), 3) four (4Norg, n = 5), or 4) eight...

A remotely delivered contraceptive was developed that suppressed estrus and prevented pregnancy in deer with 100-percent efficacy. This contraceptive utilized norgestomet, a potent progestin that is approved by the Food and Drug Administration (FDA) for use in cattle. Although the needle-less norgestomet implant is not FDA approved for use in deer, it is safe for treated animals, humans, and th...

The induction of estrus during the non-breeding season was investigated in 100 Egyptian Baladi goats (Capra hircus). All animals assigned to treatments had low progesterone concentrations (<0.5 ng/ml) tested 2 times 10 days apart to confirm anestrous condition. Animals were assigned to three experimental groups. A group of animals received subcutaneous norgestomet ear implant for 11 days and a ...

Two experiments were conducted on postpartum suckled beef cows synchronized with Syncro-Mate B and artificially inseminated approximately 48 h after implant removal. In Exp. 1, cows (> or = 42 d postpartum at the timed AI) were randomly assigned to treated (n = 101) and control (n = 85) groups on d 12 after the timed AI. Treated cows received norgestomet/silicone implants that were left in situ...

Seventy-three multiparous beef cows (21 to 35 d postpartum) were used in an experiment with a 2 X 4 factorial design to test the effects of pretreatment with norgestomet and preovulatory gonadotropic stimulation on the life span of corpora lutea induced by human chorionic gonadotropin (hCG). Cows were implanted subcutaneously for 9 d with norgestomet (3 mg; 35 cows) or sham-implanted (38 cows)....

Our hypothesis was that conception in bovine females would be enhanced if the corpus luteum was present during the period of progestin treatment to synchronize estrus. In this study, 67 heifers (one replicate) and 124 cows (two replicates) were randomly assigned to one of two treatment groups. Seven days after estrus (Day 0), all animals were implanted with norgestomet and the implant remained ...

As experiment was conducted with 15 Angus X Hereford heifers that were 16 mo of age at the time the experiment was initiated. The heifers were assigned randomly in equal numbers to be fed low (L), maintenance (M) or high (H) energy diets for 191 d. Overall average weight for heifers at the time the experiment was initiated was 294 +/- 6 kg. All heifers were exhibiting estrous cycles at regular ...