Effect of naloxone treatment on luteinizing hormone and testosterone concentrations in boars with high and low libido.

The objective was to determine the effects of the opioid peptide receptor antagonist, naloxone on circulating concentrations of luteinizing hormone (LH) and testosterone in boars characterized as having high (n=8) or low libido (n=8) based on the willingness to mount an artificial sow and allow semen collection. On the day of the experiment, blood was sampled every 15 min for 4 h before and 4 h after i.v. injection of naloxone (1 mg/kg body weight). After naloxone treatment, a libido status by time interaction was detected and concentrations of LH within 15 min after treatment were greater (p<0.05) for High-libido boars than for Low-libido boars. Concentrations of testosterone were highly variable amongst boars and there were no effects of libido status (p=0.66) or libido status by time (p=0.66). There was, however, an effect of time (p

Characteristics of sperm motility in boar semen diluted in different extenders and stored for seven days at 18 degrees C.

Although numerous extenders exist for diluting boar semen, little research has been conducted comparing commercial extenders with regard to maintaining sperm motility during storage. The objective was to use a computer- assisted sperm analysis system to assess motility of boar spermatozoa diluted in Beltsville Thawing Solution, Merck-III, Androhep-lite, Sperm Aid, MR-A, Modena, X-Cell, VSP, and Vital. Ejaculates from boars (n=10) were collected and sub-samples were diluted (35x10(6) spermatozoa/ml) in the different extenders and stored for seven days at 18 degrees. Extender by day interactions were detected (p<0.01) and on each day post collection, there were numerically small, but statistically significant differences in characteristics of sperm motility among extenders. For example, on day 7, the percentages of motile and progressively motile spermatozoa were highest (p<0.05) in X-Cell (90.7%) and Modena (63.9%), respectively. The average velocity measured over the actual point-to-point track followed by the sperm cell (VCL; 198.2 microm/s) and path velocity of the smoothed cell path (VAP; 106.4 microm/s) were highest (p<0.05) in Vital and Modena, respectively. Average velocity measured in a straight line from the beginning to the end of the track (VSL; 78.3 microm/s), average value of the ratio VSL/VAP (straightness; 73.2) and average value of the ratio VSL/VCL (linearity; 44.1) on day 7 were highest in Androhep-lite. In summary, changes in sperm motility during storage were affected by the extender utilized, but with the exception of Sperm Aid, all extenders maintained a high degree of sperm motility through 7 days of storage.

Effects of prostaglandins and prostaglandin synthesis inhibitors on sexual behavior in boars.

Experiments were conducted investigating the effects of prostaglandins and prostaglandin synthesis inhibitors on libido in boars. In Experiment 1, two prostaglandin products were compared with regard to expediting the training of boars for semen collection. On each of five consecutive days, boars received i.m. treatment with saline, dinoprost tromethamine or cloprostenol sodium (n=12/group). On each of day 1 (p=0.06), day 2 (p<0.05), and day 3 (p<0.05), but not on day 4 or 5 (p>0.1), the percentage of boars collected after dinoprost tromethamine, but not cloprostenol sodium, was greater than controls. In Experiments 2 and 3, libido in boars that were trained previously for semen collection was assessed after treatment with prostaglandin synthesis inhibitors, testing the hypothesis that endogenous release of prostaglandin is necessary for expression of sexual behaviors. In Experiment 2, boars treated with flunixin meglumine (n=12) had suppressed (p<0.01) levels of 15-ketodihydro-prostaglandin-F(2) (PGFM) in serum but characteristics of libido were similar (p>0.1) to controls (n=12). In Experiment 3, boars were administered indomethacin orally (n=12) or served as untreated controls (n=12). Indomethacin decreased (p<0.01) serum levels of PGFM, increased (p<0.05) the number of false mounts (mounting artificial sow but dismounting before an ejaculate was collected), and tended (p=0.09) to lengthen the interval between entering the collection pen and the start of ejaculation. These results suggest that prostaglandin synthesis and release is necessary for the complete display of normal sexual behaviors in boars.

Effect of P.G. 600 on rebreeding performance in sows limit-fed during lactation.

The objective was to determine whether treatment with 400 IU PMSG and 200 IU hCG (P.G. 600; Intervet America, Inc., Millsboro, DE, USA) at weaning improved rebreeding performance in sows that were limit-fed during lactation. Crossbred sows were allowed ad libitum access to feed or were limited to 3.2 kg of feed/day during an 18-day lactation. At weaning, limit-fed sows received im treatment with P.G. 600 (n = 16) or saline (n = 19) and ad libitum-fed sows received saline (n = 18). The percentage of sows in estrus by day 7 post-weaning was greater (p<0.05), and the weaning-to-estrus interval was shorter (p<0.05), for ad libitum-fed sows compared to limit-fed, saline-treated sows, with limit-fed, P.G. 600-treated sows having intermediate values that were not different from the other two groups. The percentage of sows pregnant and the numbers of corpora lutea and embryos at day 30 post-mating were not different (p>0.1) among groups. In summary, low feed intake during lactation decreased the percentage of sows that displayed estrus within 7 days after weaning and increased the weaning-to-estrus interval. These effects were at least partially remediated by gonadotropin treatment. Pregnancy rate, and litter size at day 30 of gestation, were similar for ad libitum- and limit-fed sows and not affected by P.G. 600 treatment in limit-fed sows.

Effects of dietary supplementation with omega-3 polyunsaturated fatty acids on some reproductive characteristics in gilts.

The main objective of this study was to determine the effects of dietary supplementation with omega-3 polyunsaturated fatty acids on ovulation rate and litter size at day 27 post-mating in gilts. Estrous cycles were synchronized in crossbred gilts (n=48) using a progestin (Matrix; Intervet America Inc., Millsboro, DE, USA), fed at a rate of 15 mg/day for 18 days. Following progestin withdrawal, gilts were checked for estrus twice daily and mated by artificial insemination. At 27 days post-mating, gilts were killed and reproductive tracts collected and examined. Beginning 17 days before the initiation of progestin therapy and continuing until slaughter, gilts were fed 2.27 kg of a basal diet (n=24) or the basal diet supplemented with 1% Fertilium (JBS United, Inc., Sheridan, IN) (n=24), a source of omega-3 polyunsaturated fatty acids. All gilts in the treatment and control groups were pregnant as evidenced after examination of dissected reproductive tracts at approximately 27 days post-mating. Ovulation rate (17.5 vs. 17.9; SEM=0.5; p=0.61), number of embryos (14.5 vs. 14.3; SEM=0.6; p=0.77), embryo weight (1.11 vs. 1.14 g; SEM=0.02; p=0.45), and crown-rump length (26.4 vs. 26.9 mm; SEM=0.27; p=0.28), were similar for control and Fertilium-fed gilts, respectively. Backfat thickness at day 27 post-mating was greater (p<0.01) for Fertilium-fed gilts (14.0+/-0.5 mm) compared with controls (12.3+/-0.5 mm). The present treatment with Fertilium for the period of approximately 61 days did not alter ovulation rate and litter size at day 27 post-mating in gilts.

Effects of dietary L-carnitine supplementation on semen characteristics in boars.

In some species, dietary supplementation with L-carnitine has been reported to increase sperm concentration and sperm motility. The objective of these experiments was to test the hypothesis that L-carnitine supplementation improves the semen characteristics of boars. In Experiment 1, boars (258 days of age) were fed daily a control diet (n = 9) or the control diet plus L-carnitine (500mg per day; n = 9 ). Semen was collected weekly from Weeks 0 to 15 and on 4 consecutive days during Week 16. Experiment 2 was similar to Experiment 1 except boars ( n = 10 per treatment) were 504 days of age. For the weekly and intensive collections there were no consistently positive effects of treatment on semen volume, sperm concentration, total spermatozoa, or sperm motility. Spermatozoa from L-carnitine-treated boars did not display an enhanced ability to maintain motility during 7-day liquid storage. In conclusion, indicators of semen quality were not enhanced by dietary supplementation of L-carnitine in boars.

The effect of lutalyse on the training of sexually inexperienced boars for semen collection.

The objective was to determine if i.m. treatments of lutalyse (PGF2alpha; dinoprost tromethamine salt) expedited the training of sexually inexperienced boars for semen collection. Lean-type, terminal-line boars (n = 40; 177.4 +/- 2.4 day of age and 112.8 +/- 2.0 kg body weight) that had not previously experienced natural mating were utilized. Boars were moved individually 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 i.m. 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 1-5 (1 = no interest in the artificial sow; 5 = mounting 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). In summary, lutalyse increased libido scores, but did not affect the number of boars trained for semen collection.

Circulating concentrations of luteinizing hormone, testosterone, and growth hormone after naloxone treatment in sexually mature boars.

The effects of naloxone, an antagonist of opioid peptides, on circulating concentrations of luteinizing hormone (LH), testosterone, and growth hormone (GH) were determined in sexually mature boars. Blood samples were collected at 15-min intervals for three hr from five crossbred boars. Two hr after initiation of blood sampling, boars received an i.v. challenge of naloxone (1 mg/kg body weight; n=2) or 0.9% saline (n=3). Twenty-four hr later the experiment was repeated, but boars that previously received naloxone received saline and vice versa. A time by treatment interaction (p=0.09) was detected for concentrations of LH in serum, and levels of LH were greater (p<0.03) after treatment with naloxone compared to saline. Concentrations of testosterone in serum were affected by time (p<0.01), but not treatment (p= 0.59) or treatment by time (p=0.74). A treatment by time interaction (p=0.02) was detected for serum GH concentrations. Levels of GH increased in saline-treated boars (p<0.01), but not in boars receiving naloxone (p>0.1). Our results are consistent with the theory that opioid peptides suppress LH secretion and stimulate GH release in sexually mature boars.