PORCINE FOLLICLE-STIMULATING-HORMONE TREATMENT OF GILTS DURING AN ALTRENOGEST-SYNCHRONIZED FOLLICULAR PHASE - EFFECTS ON FOLLICLE GROWTH, HORMONE-SECRETION, OVULATION, AND FERTILIZATION

Porcine FSH (SUPER OV(R)), containing .03% LH activity, and equine cho rionic gonadotropin (eCG) were administered during an altrenogest-sync hronized follicular phase to determine their effects on follicle devel opment, estrus, ovulation, and fertilization. Treatments were made by i.m. injection starting on d 1 (24 h after the last feeding of altreno gest): 1) saline, once, n = 14; 2) eCG (1,200 to 1,500 IU) once, n = 3 2; 3) FSH 14 (n = 2) or 21 (n = 6) NIH-FSH-S1 units/100 kg BW, divided among six injections at 12-h intervals (FSH14/21); 4) FSH, 28 NIH-FSH -S1 units/100 kg BW, divided among six injections at 12-h intervals, n = 12; and 5) FSH, 28 NIH-FSH-S1 units/100 kg BW and 100 IU hCG, two o r six injections at 12-h intervals (FSH28+hCG), n = 13. Gilts were inj ected with 750 IU of hCG on d 5 to ensure ovulation. Twenty-eight eCG- and FSH-injected gilts (n = 6, 8, and 11 on treatments 3, 4, and 5, r espectively) were bred and laparotomized on d 7 to recover ova and rec ord ovulation rate. The mean number of ovulations and large (6- to 10- mm) follicles, respectively, on d 7 were as follows: saline (17, .7), eCG (43, .9), FSH14/21 (15, .6), FSH28 (12, 16), and FSH28+hCG (32, 21 ). Plasma FSH concentrations were at least threefold higher (P < .05) in gilts treated with FSH than in gilts not treated with FSH. The perc entage in estrus was higher(P < .05) for saline-and eCG-treated gilts (100 and 87%, respectively) than for FSH-treated gilts (53%). Proporti on of FSH28+hCG-treated gilts with fertilized ova (27%) was lower than for other groups (79 to 100%). In summary, the 3-d high dose FSH trea tment (FSH28 and FSH28+hCG) during an altrenogest-synchronized follicu lar phase increased the number of potentially ovulatory follicles, but this potential benefit was not realized because many follicles failed to ovulate. The co-injection of low doses of hCG (FSH28+hCG) increase d the ovulation rate and estradiol secretion but reduced ova recovery and fertilization rate compared with eCG and the other FSH treatments.