Enhancing Boar Reproductive Performance for Purposes of Artificial Insemination

The objectives were to: 1) determine if im treatments of Lutalyse expedited the training of sexually inexperienced boars for semen collection and increased spermatozoal output, and 2) determine the effects of dietary L-carnitine supplementation on boar libido, semen quality, sperm production, and maintenance of sperm motility during liquid storage. Experiment 1 utilized lean-type, terminal-line boars (National Pig Development, Roanoke Rapids, NC) (n = 40; 177.4 ± 2.4 d of age and 112.8 ± 2.0 kg body weight) that had not previously experienced natural mating. Boars were individually moved twice weekly for 6 weeks (total of 12 training sessions) to a semen collection room equipped with an artificial sow. Upon entering the semen collection room, boars received im treatments of either deionized water (4 mL, n = 10) or Lutalyse at doses of 5 mg (n = 10), 10 mg (n = 10), or 20 mg (n = 10), and subsequently received a libido score of 1 to 5 (1 = no interest in the artificial sow; 5 = mounting the artificial sow and allowing semen collection). The percentages of boars successfully trained for semen collection during the experimental period were similar (P > 0.05) for controls (20%) and boars receiving 5 mg (30%), 10 mg (20%), or 20 mg (10%) of Lutalyse. Average libido score for boars receiving 10 mg Lutalyse (2.35 ± 0.08) was greater (P < 0.05) than for controls (2.14 ± 0.06). Libido score for the 20 mg treatment group were (1.78 ± 0.06) lower (P < 0.05) compared to the other treatment groups. Characteristics of ejaculates (volume, gel weight, sperm concentration, total spermatozoa) from control boars and boars treated with Lutalyse at doses of 5, 10, or 20 mg were similar (P > 0.05). For Exp. 2, the same group of boars was utilized in two similar trials (Trial 1, 1a, 1b: n = 9 for control and Lcarnitine-treated boars; Trial 2, 2a, 2b: n = 10 for control and L-carnitine-treated boars). Boars were fed a fortified, corn and soybean meal-based diet at a rate of 2 kg/d. Boars that were randomly selected for L-carnitine treatment received the same diet mixed with L-carnitine to achieve supplementation of 500 mg/d. For 16 wk, semen was collected weekly via the gloved hand method and was analyzed for gel-free volume, gel weight, sperm concentration, sperm per ejaculate, and characteristics of sperm motility. Time to ejaculation (reaction time), duration of ejaculation, and number of false mounts were also recorded for each collection. Trials 1a and 2a were conducted during weeks 16 and 17 for each respective trial. Boars were collected once on 4 consecutive days, allowed 4 d of rest, and then collected again, to estimate daily spermatozoal production. At the end of 16 wk, a semen sample was also processed and extended in Beltsville Thawing Solution (BTS) to achieve a dilution of 3 x 10 spermatozoa/100 mL-dose for Trials 1b and 2b. The extended semen was stored in plastic bottles at 18°C and motility was evaluated daily for 7 d post collection. L-carnitine supplementation for 16 wk had no effects on semen volume, gel weight, total number of sperm cells per ejaculate, reaction time, or sperm motility (P > 0.1). Boars receiving the L-carnitine-supplemented diet displayed an increase in the number of false mounts before ejaculating and an increase in sperm concentration (P < 0.05) in Trial 2. A treatment by week interaction was detected for sperm concentration in Trial 2 (P < 0.005). Increased sperm concentrations in Lcarnitine-treated boars were demonstrated after only one week of feeding the respective diets. Given that the production of a mature sperm cell requires 7 to 8 wk in boars, it is therefore difficult to conclude that differences in sperm concentration were due solely to treatment. Daily spermatozoal production was similar between control boars and boars supplemented with L-carnitine (P > 0.1) for both Trials 1a and 2a. L-carnitine supplementation did not affect percent motility in Trials 1b and 2b or sperm progressive motility in Trial 2b during 7 d storage (P > 0.1). A treatment by day interaction was determined for sperm velocity (P < 0.05) in Trial 2b. L-carnitine supplementation decreased mean sperm velocity significantly after 2 d of storage. Overall, L-carnitine had no beneficial effects on boar libido, semen quality, sperm production, or maintenance of sperm motility during liquid storage. However, Lutalyse increased libido scores, but did not affect the number of boars trained for semen collection or number of spermatozoa ejaculated.