High impact information on MELENGESTROL ACETATE

• In experiment 3, one half of the cows in each group (CON and NOR) were fed melengestrol acetate (MGA) beginning on Day 4 after estrus and continuing until Day 35 [1].
• Synchronized conception and pregnancy rates (61/100 [61%], 61/109 [56%], MGA Select; 71/101 [70%], 71/111 [64%], 7-11 Synch), and final pregnancy rates (94/109 [86%], MGA Select; 99/110 [90%], 7-11 Synch) did not differ between treatments [2].
• Mean days postpartum for MGA and control cows at the initiation of treatment were 39.6 and 38.9 d for herd 1; and 51.9 and 50.9 d for herd 2, respectively (P > 0.70 within herds) [3].
• Pregnancy rates (P < 0.25) were 44.8% (39/87: Co-Synch), 47.8% (43/90; Co-Synch + MGA), and 60.7% (54/89: EB/P4 + MGA) [4].
• The use of GnRH or estradiol to facilitate fixed-time insemination in an MGA-based synchronization regimen in beef cattle [5].

Biological context of MELENGESTROL ACETATE

• These data identify differences in follicular and endocrine response when cows were estrus synchronized with MGA versus PGF prior to superovulation [6].
• Parturition was blocked more effectively as dose of MGA increased (P = .075), but only parturition was blocked rather than the effects of PN [7].
• Control of the bovine estrous cycle with melengestrol acetate (MGA): a review [8].
• Pregnancies were not observed in the five animals implanted with MGA during anestrus [9].

Anatomical context of MELENGESTROL ACETATE

• Non-invasive screening for treatment of heifers with the anabolic steroid melengestrol acetate (MGA) by feces analysis [10].
• In the study, uterus, liver and muscle tissue from 24 cycling heifers were taken after the animals were treated either with Melengestrol Acetate (MGA), Finaplix-H (200 mg Trenbolone Acetate) or Ralgro (36 mg Zeranol) for 56 days [11].

Associations of MELENGESTROL ACETATE with other chemical compounds

• More MGA-treated heifers (P < 0.01) expressed estrus in a 3-d period than the controls [12].
• However, a proportion of heifers treated MGA 10% 4 36 and norgestomet 3% 1 36 expressed behavioral estrus during second estrus even though they were diagnosed as pregnant from first service by elevated P(4) levels on Day 21 [12].
• Compared to the respective control treatment at each location, prepubertal heifers assigned to the MGA Select protocol at Location 1 had longer intervals to estrus, whereas at Location 2, prepubertal heifers assigned to the MGA-PGF2alpha protocol had longer intervals to estrus [13].
• Effects of 21-day treatment with melengestrol acetate (MGA) with or without subsequent prostaglandin F2 alpha on synchronization of estrus and fertility in beef cattle [14].
• Ovarian follicular dynamics and steroid secretion patterns were monitored in postpartum beef cows that were synchronized for estrus with melengestrol acetate (MGA) or prostaglandin F(2alpha) (PGF) prior to superovulation [6].

Gene context of MELENGESTROL ACETATE

• The affinity of these three compounds and of MGA to the hSHBG was much lower compared with DHT [15].

Analytical, diagnostic and therapeutic context of MELENGESTROL ACETATE

• Four duplicate treatments were randomly assigned to pens as follows: (1) intact-control (n = 19), (2) intact + melengestrol acetate (MGA, n = 20), (3) hysterectomy (n = 17) and (4) ovariectomy (OVX, n = 19) [16].
• The objective of this experiment was to determine whether treatment with MGA prior to a GnRH-PG-GnRH protocol would improve pregnancy rates resulting from fixed-time artificial insemination (AI) [3].
• A sensitive enzyme immunoassay (EIA) for the determination of melengestrol acetate (MGA) in adipose and muscle tissues [17].
• In Experiment 2, heifers (n = 651) were TAI (Day 0) and 13 days later randomly assigned to one of seven groups (n = 93 per group) to receive a once-used CIDR (three groups; Days 13-20), MGA (three groups; Days 13-19), or no treatment (control group) [18].

References