Investigation of exogenous gonadotropin treatment for prevention of non-infectious infertility and for embryo production using the prepubertal gilt as a model

Reliable methods for consistent prevention of non-infectious infertility and production of embryos are limited for swine. In many species, FSH is favored over chorionic gonadotropins for induction of estrus and ovulation, yet little data are available to indicate its value for use in pigs. Therefore, the objective of this dissertation is to determine the effective methodology for the use of porcine FSH (pFSH, Folltropin) in prepubertal gilts. Experiment 1 evaluated the effect of intramuscular (im) or subcutaneous (sc) administration of a more purified pFSH (Folltropin) with various doses of pLH (Lutropin) on fertility responses in prepubertal gilts. For experiment 1a, gilts were treatment with either saline, 100 mg FSH im, 100 mg FSH sc, 100 mg FSH and 0.5 mg LH im, or 100 mg FSH and 0.5 mg LH sc. Treatments were divided into 6 injections given every 8 hours. The proportion of gilts developing large follicles (-25%), expressing estrus (0%), and ovulating (∼14%) was similar (P>0.10) to saline. For experiment 1b, gilts were administered saline or FSH with hCG (100 IU) or 5 mg, 10 mg, or 20 mg of LH. FSH-LH was administered as previously described, whereas hCG was given twice at 24 hours intervals. Compared to saline, FSH-LH and FSH-hCG increased (P<0.05) estrus (0 vs. 79%), ovulation (10 vs. 100%), and ovulation rate (3 vs. 56 CL). However, incidence of follicular cysts (>6%) and poorly formed CL (>50%) were increased (P<0.01) in FSH-LH gilts compared to other treatments. Experiment 2 evaluated the effect of dose of FSH (25, 50 or 100 mg) with added LH (1.25, 2.5 or 5.0 mg) on fertility in prepubertal gilts. All treatments were given as previously described. Compared to saline (26%), the proportion of gilts developing large follicles was increased (P<0.05) for all FSH-LH treatments (38 to 100%). The proportion of gilts expressing estrus was not influenced (P>0.10) by treatment (13 to 63%). Regardless of FSH dose, 5 mg of LH increased (P<0.05) gilts ovulating (59%) compared to 1.25 mg (19%) and 2.5 mg (49%) LH, but only half of the gilts that developed large follicles ovulated. There was no effect of treatment (P>0.10) on ovulation rate, which varied from 3.4 to 39 CL and only the 100 mg FSH with 5 mg LH induced follicular cysts. Experiment 3 evaluated the effects of dose of FSH-LH compared to PG600 and saline in prepubertal gilts for fertility induction and embryo production. Gilts received saline, PG600, or either 25 or 50 mg of FSH with 5 mg of added LH. PG600 was given once on day 0 and FSH-LH and saline treatments were administered as previously described. The FSH-LH group also received 5 mg LH on day 4 to induce ovulation. A greater (P<0.0001) proportion of FSH-LH and PG600 gilts developed large follicles (>80%) compared to saline (20%). FSH-LH also increased (P<0.001) estrus (>73%) when compared to PG600 (62%) and saline (20%) but proportions of gilts that ovulated were similar between FSH-LH and PG600 (>77%) but greater (P<0.0001) than saline (26%). FSH-LH increased (P<0.05) ovulation rate (≥19 CL) compared to PG600 (10 CL) and saline (8 CL). FSH-LH increased (P<0.05) incidence of follicular cysts (>45%) compared to PG600 (14%) and saline (1%). Pregnancy rate (range: 55 to 75%) was similar (P>0.10) between treatments and number of embryos was increased (P<0.0001) for FSH-LH (>8) compared to PG600 (5) and saline (4). The within liter size variation was similar between 25F5L (0.25 SD), 50F5L (0.27 SD), and PG600 (0.28 SD) and less (P<0.05) than saline (0.76 SD). Overall, additional LH content is necessary when using Folltropin for induction of fertility responses in prepubertal gilts. Folltropin doses as low as 25 to 50 mg of FSH with 5 mg of Lutropin may be used for estrus and ovulation induction and embryo production in prepubertal gilts. The administration methodology should be altered for more practical application of Folltropin and Lutropin, such as in a slow release system, altered by duration, timing, or sequential administration of FSH and LH, which may further increase ovulation rate and thus embryo numbers and reduce the incidence of follicular cysts. Therefore, Folltropin (25 to 50 mg) with Lutropin (5 mg) may be used as alternative gonadotropin treatment in swine, but futures studies are needed for improved efficacy and practical application in swine.