We previously reported that ovulation rate, but not pregnancy rate or litter size at d 30 post-mating, was enhanced by gonadotropin treatment (P.G. 600; Intervet America Inc., Millsboro, DE) in gilts fed a progestin (Regu-mate; Intervet America Inc.) compared with gilts receiving progestin alone. We hypothesized that P.G. 600 altered the timing of ovulation, therefore mating gilts 12 and 24 h after first detection of estrus, as is common in the swine industry, may not have been the most appropriate breeding regimen. The objective of this study was to determine the effect of P.G. 600 on the timing of ovulation in gilts treated with Regu-mate. Randomly cycling, crossbred gilts (5.5 m of age, 117 kg BW, and 14.7 mm BF) were fed a diet containing Regu-mate to provide 15 mg/d for 18 d. Twenty-four h after Regu-mate withdrawal, gilts received i.m. P.G. 600 (n = 25) or saline (n = 25). Gilts were checked for estrus at 8 h intervals. After first detection of estrus, trans-rectal ultrasonography was performed at 8 h intervals to determine the time of ovulation. Gilts were killed 9 to 11 d after the onset of estrus to determine ovulation rate. All gilts displayed estrus by 7 d after treatment with P.G. 600 or saline. Compared with saline, P.G. 600 increased (P = 0.07) ovulation rate (14.8 + 1.1 vs. 17.5 + 1.0, respectively). The intervals from injection-to-estrus (98.4 + 2.7 vs. 110.9 + 2.7 h; P < 0.01) and injection-to-ovulation (128.6 + 2.8 vs. 141.9 + 3.2 h; P < 0.01) were decreased in gilts treated with P.G. 600 compared with gilts treated with saline. Estrus duration (54.4 + 2.3 vs. 53.7 + 2.5 h; P = 0.83), estrus-to-ovulation (30.2 + 2.0 vs. 31.7 + 2.2 h; P = 0.62) and time of ovulation as a percentage of duration of estrus (55.8 + 2.7 vs. 57.5 + 3.0%; P = 0.67) were similar for the P.G. 600 and saline-injected gilts, respectively. In summary, P.G. 600 advanced the onset of estrus and ovulation following termination of Regu-mate treatment and increased ovulation rate. However, treatment of gilts with P.G. 600 had no effect on the timing of ovulation relative to the onset of estrus. / Master of Science

The U.S. hog industry's shift to vertically-integrated, intensively-managed operations brought about a variety of management systems for breeding herds, including batch farrowing. In this system, groups of sows are weaned in 2- to 5- week intervals, making estrus synchronization of new gilts and sows critical to maintaining reproductive efficiency in the herd. The use of commercially available hormones to synchronize estrus in this system has not been extensively studied. This experiment was conducted to determine whether the use of commercially available hormones (MATRIX® and P.G. 600®; Merck Animal Health, De Sota, KS) in a 5-week batch management system had a positive impact on reproductive efficiency in gilts and sows over the course of 3 parities. Gilts were allocated to an Entry Group (A, B, or D) and then assigned to a treatment, Hormone-Assisted (HA) (5 mL P.G. 600 injection 5 days and/or fed 15 mg/day of MATRIX for 14 consecutive days prior to the breeding week) or Control (no exogenous hormones). Gilts and sows were checked daily for estrus with a mature boar, and a group was bred using AI during a 7-day breeding period every 5 weeks and allowed to farrow up to 3 parities. Among groups, there was a tendency (P = 0.08) for more HA than control gilts to display estrus and be mated on schedule. For gilts within Group A, more (P < 0.01) HA than control females displayed estrus and were mated. Body weight at first service for gilts in Groups A and B were higher than Group D (P < 0.01). Overall, there was no effect of treatment on (P = 0.20) non-productive days. There was a strong tendency for HA sows to have a greater (P = 0.07) number of parities completed than control sows; Total pigs born (P < 0.05) and total pigs born alive (P < 0.05) were greater for HA sows than control sows. In Parity 1, Group D sows had a lesser number of pigs born (P < 0.01) and pigs born alive (P < 0.02) than Groups A and B; The number of pigs weaned differed between entry groups (P < 0.05) (Group B > Group A > Group D); Control sows weaned more pigs (P < 0.02) and had a greater litter weaning weight (P < 0.01) than HA sows; HA sows had a lower (P < 0.05) wean-to-estrus interval than control sows. No significant effects of group or treatment were observed in Parities 2 and 3. The use of exogenous hormones to synchronize estrus had a positive impact on reproductive efficiency in HA gilts/sows in a 5-week batch management system. / Master of Science

Developing a single fixed-time artificial insemination (FTAI) protocol would benefit small-scale and niche market pork producers by decreasing semen costs and labor associated with detection of estrus. The objective of this study was to test the efficacy of an artificial insemination (AI) breeding system using triptorelin acetate, a GnRH agonist (OvuGel®; JBS United Animal Health, LLC, Sheridan, IN) that induces ovulation. A total of 96 sows (parity, 3.5 ± 0.2; body condition score (BCS), 2.5 ± 0.07) were weaned (h 0) after a 24.8 ± 0.6 d lactation on five participating small swine farms and allocated to one of four treatment groups: 1) TRT1: (n = 24) OvuGel applied intravaginally at h 96 and AI at h 120; 2) TRT2: (n = 24) P.G. 600® (400 IU eCG and 200 IU hCG, Merck Animal Health, Inc., De Sota, KS) injected intramuscularly at weaning, OvuGel at h 96 and AI at h 120; 3) TRT3: (n = 24) P.G. 600 at weaning, and AI at 0 and 24 h after first detection of estrus; and 4) TRT4: (n = 24) AI at 0 and 24 h after first detection of estrus. Treatments 1 and 2 were FTAI protocols with sows being inseminated without regard to estrus onset. Treatments 3 and 4 were consistent with current industry AI practices. The proportion of females displaying estrus by d 7 post-weaning was greater (P < 0.05) for sows that received OvuGel (94.5 %) compared to sows that did not receive OvuGel (82.2 %). There were no effects (P > 0.05) of P.G. 600 or P.G. 600 x OvuGel on females displaying estrus by d 7 or d 10 post-weaning. Weaning to estrus interval was decreased (P < 0.05) for sows that received P.G. 600 (4.9 ± 0.4 d) compared to sows that did not receive P.G. 600 (5.4 ± 0.4 d). There were no effects (P > 0.05) of OvuGel or P.G. 600 x OvuGel on the weaning-to-estrus interval. There were no effects of P.G. 600, OvuGel or P.G. 600 x OvuGel (P > 0.1) on pregnancy rate (total sows pregnant/inseminated) (61.2 %), total litter size (11.3), number born dead (1.0) or number of mummies (0.2). There was an effect (P < 0.05) of P.G. 600 x OvuGel on total born live (10.2). Sows treated with OvuGel had a greater number of live piglets born per semen dose (5.4) compared to sows that did not receive OvuGel (3.2) (P < 0.05). These results suggest that FTAI protocols may be employed on small-scale pig farms without compromising reproductive performance. / Master of Science