Charles C. Love

The relationship of increased susceptibility of sperm DNA to denaturation and fertility in the stallion

The relationship between fertility and susceptibility of sperm DNA to denaturation was determined in a group of 84 actively breeding, clinically fertile stallions. Susceptibility of DNA to denaturation was determined using the sperm chromatin structure assay (SCSA). The SCSA measures, mean of alpha-t (mean alpha t), standard deviation of alpha-t (SD alpha t), and the COMP of alpha-t (cells outside the main population)] were significantly correlated with the percentage seasonal pregnancy rate (SPR; mean alpha t, r = -0.24, P < or = 0.05; % COMP alpha t, r = -0.27, P < or = 0.05); percentage pregnant per first cycle (FCP; SD alpha t, r = -0.30, P < or = 0.01; % COMP alpha t, r = -0.42, P < or = 0.0001); and the percentage pregnant per cycle (PC; mean alpha t, r = -0.31, P < or = 0.01; SD alpha t, r = -0.32, P < or = 0.01; % COMP alpha t, r = -0.41, P < or = 0.0001). This study describes detectable intrinsic variation in sperm chromatin structure among fertile stallions (SPR, mean = 83%; FCP, mean = 58%; PC, mean = 57%) in an active breeding population (number of mares bred/stallion/year, mean = 37), in the absence of overt reproductive abnormalities and apparent diseases such that an increase in the susceptibility of sperm DNA to denaturation is associated with reduced fertility, both in terms of efficiency of reproduction (FCP and PC) and seasonal pregnancy rate (SPR). Both COMP alpha t and mean alpha t were useful indicators of fertility, with COMP alpha t being the only SCSA value able to identify mean differences between fertility groupings for SPR and FCP, and overall it was the most reliable indicator of fertility in this group of stallions. The SCSA is able to evaluate a compartment of the spermatozoa which is different from that of traditional tests for sperm quality such as motility and morphology.

Xylazine-induced ex copula ejaculation in stallions.

This study is a part of ongoing work toward developing pharmacological methods of enhancing and inducing ejaculation in stallions with ejaculatory dysfunction. We evaluated ex copula ejaculatory response to treatment with the alpha-adrenergic agonist xylazine hydrochloride, with and without preliminary sexual stimulation. Twenty-eight mature stallions each received, in random order, one xylazine trial (0.3 mg/lb, i.v.) without preliminary sexual stimulation, one xylazine trial with 5 to 10 min of sexual prestimulation, and one control trial (equivalent volume sterile water injection). Trials were conducted in the animal stalls. Ejaculation occurred in 15 of 56 (27%) xylazine trials. No ejaculations occurred in the sterile water control trials. In trials with sexual prestimulation, ejaculation occurred in 39% compared with 14% in trials without prestimulation. This difference was significant (P<0.05). Xylazine-induced ejaculates were collected into a plastic bag attached to a girth and were similar to those obtained by artificial vagina. Nine of the 15 ejaculations occurred within 2 min of injection.

Manual stimulation collection of semen from stallions: Training time, sexual behavior and semen

Abstract In Experiment 1, 31 pony stallions of unknown breeding history were trained to either manual stimulation (n = 20) or traditional artificial vagina (n = 11) collection of semen. For manual stimulation, 45% achieved ejaculation on the ground during the initial training session. The remaining 55% achieved ejaculation by manual stimulation while mounted during the first or second training session. For artificial vagina training, 73% ejaculated during the first training session. The mean number of training sessions required was 1.15 for the manual stimulation technique and 1.18 for the traditional artificial vagina technique. Experiment 2 was conducted to compare sexual behavior and the semen obtained by manual stimulation and artificial vagina procedures. Six stallions which had been trained for manual stimulation collection of semen in Experiment 1 were used. Semen was collected from each stallion in two replicates of four collections per replicate, during which each stallion was exposed alternately on four successive days to manual stimulation or artificial vagina technique. There were no significant differences due to the method of collection in total collection time, number of mounts required, or mount to ejaculation latency. Manual stimulation required a mean of nine thrusts, while the artificial vagina method required only six. This difference was significant (P

Use of a semen extender containing antibiotic to improve the fertility of a stallion with seminal vesiculitis due to Pseudomonas aeruginosa.

A breeding trial was conducted to determine if a semen extender containing polymixin-B sulfate would improve the fertility of a stallion with seminal vesiculitis due to Pseudomonas aeruginosa . Twenty-three mares were bred to the stallion by one of three methods: artificial insemination with raw semen (Group 1, n = 10), artificial insemination with semen mixed 1:1 with a nonfat dry skim milk/glucose extender containing 1000 units/ml polymixin-B sulfate (Group 2, n = 9), or natural service immediately following infusion of the uterus with 100 ml of the same extender (Group 3, n = 4). Artificial breedings contained a minimum insemination dose of 500 x 10(6) progressively motile spermatozoa. All mares were bred every other day while in estrus. Pregnancy status was determined by transrectal ultrasound examination 15 d after the last breeding. First-cycle pregnancy rate for Group 2 mares (78%) was greater (P < 0.01) than for Group 1 mares (10%). There was a tendency (P = 0.10) for the pregnancy rate of Group 3 mares (50%) to be greater than Group 1 mares. The use of a semen extender containing polymixin-B sulfate improved the fertility of this stallion.

Semen Collection Techniques

Semen collection techniques in the stallion have evolved considerably over the last 70 to 80 years and are used today primarily for artificial insemination. Semen can be collected from stallions that are otherwise unable to breed, allowing continued use of valuable animals. There are many options for collection of semen from stallions that present with ejaculatory dysfunction (see the article by McDonnell elsewhere in this issue.) Although there are many advantages to the use of artificial breeding, the collector must understand each step of the collection procedure as well as stallion preferences and proper use of an artificial vagina and mount source so that a representative semen sample is collected.

Ultrasonographic evaluation of the testis, epididymis, and spermatic cord of the stallion.

Ultrasonographic examination of the testis, epididymis, and spermatic cord of the stallion can be used to enhance the routine breeding soundness evaluation of the stallion. Normal ultrasonographic anatomy of the testes and associated structures are presented to aid the clinician in differentiating abnormalities of these structures.

Comparison of pregnancy rates achieved with frozen semen using two packaging methods

The pregnancy rate achieved with frozen semen using two packaging methods was compared in two separate experiments. The sperm-rich fraction of the semen was collected and immediately extended in an egg-yolk based extender to a final concentration of 100 x 10(6) sperm/ml. Half of each ejaculate was packaged in 4.0-ml plastic straws and the other half in 10-to 12-ml flattened aluminum tubes. After detection of a 35-mm follicle, mares were inseminated daily until ovulation. Pregnancy was detected, and embryonic vesicle size was measured by ultrasonic echography Days 14 to 26 after ovulation. The one-cycle pregnancy rate achieved using both packaging methods was 50% overall (23 46 ), with 46% (12 26 ) and 55% (11 20 ) rates achieved, respectively, using straws and aluminum tubes. These rates were not significantly different.

Phenylbutazone treatment in breeding stallions: Preliminary evidence for no effect on semen or testicular size

Abstract Effects of phenylbutazone treatment on semen and testicular size were evaluated using 6 mature stallions. Three stallions were given 1 g phenylbutazone orally in feed twice daily for 4 weeks, and 3 stallions remained untreated. Semen samples were obtained daily for 7 consecutive days once during a 2-week baseline period (Week 2), once after 4 weeks of treatment (Week 6), and once following 1 complete spermatogenic cycle (60 days) after treatment was discontinued (Week 16). During the remaining weeks (Weeks 1,3,4,5,7,8 and 9), semen was collected twice weekly. Semen samples were evaluated using traditional and computer-assisted techniques at the time of collection and at 24 and 48 hours of storage at 4°C. Testicular volume was estimated using ultrasonography once during each period of the study. Repeated measures analysis of variance revealed no significant measurable effects of phenylbutazone treatment on semen at the time of collection or after storage at 4°C for 24 or 48 hours. Similarly, no effect on testicular volume was found.