Browsing by Subject "Stallions"
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Item Effects of short-term oral altrenogest dosages on behavioral and testicular parameters of post-pubertal stallions(Texas Tech University, 2000-12) Vartorella, Heather A.Overly sexual/aggressive stallions within the performance horse industry create a hazardous working environment and several training challenges To suppress these behaviors without surgical castration, many trainers are currently administering oral altrenogest (Regu-Mate®, Intervet International B V., Boxmeer, Netherlands) to stallions in an off-label apphcation. Though few studies have been performed on stallions, previous work suggests the effectiveness of altrenogest in reducing the levels of reproductive hormones, spermatogenesis, and sexual/aggressive behavior varied depending on the dosage size, the duration of treatment, and the age of the stallion. However, to date no one has examined the efficiency of a short term, repetitive dosage with practical application, such as when behavior is unwanted only for a temporary period (during a performance presentation; i.e., show or race). Therefore, the objective of this study was to evaluate the testicular, hormonal, and behavioral parameters of three year old stallions receiving a short term, repetitive dosage of oral altrenogest. Further objectives were to etermine if the sexual/aggressive behavioral could be suppressed while reducing the longterm negative effects on reproduction. Nine, three-year-old Quarter Horse stallions were initially blocked by sire, and then randomly designated to two groups, treatment (n=5) and control (n=4). The treatment group received an oral daily dose of 0.088 mg/kg BW Regu-Mate® followed by ten days of recuperation (no treatment). This process was repeated for a total of three times over 60 days, followed by a recovery period of 36 days. The altrenogest dosages had no significant effects on body weight, but did increase body condition scores (P=0.052). Body condition scores remained higher after Day 30. Of the testicular parameters analyzed on Day 96, scrotal width and gross testicular parameters were unaffected, however, mean spermatid counts were decreased (P<0.05). While no differences were due solely to treatment for either estrogen or testosterone concentrations, there was a significant time by treatment interaction involving estrogen levels(P<0.05). No significant differences were seen for any of the behavioral actions analyzed based on frequency, latency, or duration, at any point of the study. Several traits assessed in this study showed large variations between individual stallions. Further research of altrenogest in the stallions is needed to determine a practical dosage amount and sequence to produce a manageable animal, which takes age and fertility effects into consideration.Item Effects of Strenuous Exercise on Stallion Sperm Quality(2012-10-19) Rosenberg, Jennifer L.Some stallions are expected to perform athletically and breed contemporarily. Athletic activity has the potential, especially during the summer months, to induce thermal stress to the testes, resulting in reduced reproductive capability due to decreased sperm quality and libido. There is concern in the horse industry about what level of exercise, if any, affects the reproductive capability of a stallion. Thermal stress associated with training and exercise may impact sperm quality and the future reproductive capability of the stallion. The goal of this study was to determine the effect of strenuous exercise on stallion sperm quality. The objectives were to measure changes in body and scrotal temperatures following strenuous exercise and sperm quality following strenuous exercise. Miniature Horse stallions (n = 7), implanted with subdermal thermosensory devices in the subcutaneous neck and scrotal tissue, were assigned to treatment group based on age and semen quality. Exercising stallions (EX; n = 3) were exercised 4 d/wk for 90 min for 12 wk, while non-exercising stallions (CN) were tied in the shade. Semen was collected from stallions for 5 consecutive days every 4 wk to evaluate semen quality (raw, 24 h and 48 h cooled). Subcutaneous scrotal (SQST), rectal (RT) and neck (NT) temperatures were recorded along with heart rate. Spermatozoa data were normally distributed; therefore, they were subjected to parametric analysis by repeated measures (wk) using the PROC MIXED procedure (SAS v 9.1; SAS Inst. Inc., Cary, NC). Model included treatment (CN or EX), time (wk 0, 4, 8, or 12), and stallion as the subject of the repeated measures. Compared to the CN group, EX stallions had elevated temperatures (avg RT 39.27 vs 37.07 degrees, NT 39.77 vs 37.44 degrees C, and SQST 34.90 vs 33.40 degrees C; P < 0.0001). There was no difference in sperm quality between treatment groups (P > 0.05). In this study, strenuous exercise in Miniature Horse stallions, did not affect sperm quality. This suggests that anecdotal reports of reduced sperm quality in stallions in training may have other causes other than elevated scrotal and body temperature. While previous studies have illustrated that prolonged insulation of the testes reduces semen quality, strenuously exercising stallions for up to 90 min under hot and humid ambient conditions may not be harmful to spermatogenesis.Item The effects of oral altrenogest on two-year-old stallions in training(Texas Tech University, 1999-12) Heninger, Noah L.Despite widespread use of oral altrenogest (Regu-Mate®, Hoescht-Roussel Vet, Warren, NJ) by trainers throughout the performance horse industry to suppress sexual/aggressive behavior in the stallion, few studies have been performed to document both short and long term physiological effects. Further, variable doses of altrenogest are currentiy in extra-label use, including 0.044mg/kg BW per day (current label dose for the suppression of estrus in mares) and 0.088 mg/kg BW per day. This study examined the suppressive effects of the single mare dose of altrenogest (0.044 mg/kg BW daily) on the steroidal hormone profiles, seminal quality, and sexual/aggressive behavior in two-yearold stallions. Ten two-year-old Quarter Horse stallions in early training were exercised in a training protocol consistent with methods to produce a working ranch horse. Prior to the study, horses were put through a training period for semen collection behavior. Horses were stratified across treatments according to breeding performance and sire, then randomly assigned to treatment (n=5) and control (n=5) groups. The treatment group was administered a daily oral dose of 0.044 mg/kg BW daily for a period of 67 days. No significant differences were found between treatment groups in weight or body condition scores at the experimental dose given. Altrenogest also had no significant effect on any behavioral parameters measure by standardized teasing tests or at time of semen collection. No significant differences were seen for any seminal parameter, at any point in this study. Averages of total scrotal width (TSW) across control and treatment groups were lower (P<. 03) for treatment animals at the end of treatment time period (d 67). By day 157 mean TSW for both treatment and control stallions were not different from each other; however, both were significantiy higher from pre-trial and end of treatment period values. At castration, comparisons of trimmed testicular weight (testicle minus the epididymis) between control and treatment groups were not different. Histological analysis of testicular tissue revealed no significant difference between treatment groups for the average number of spermatids per seminiferous tubule. Altrenogest treatment significantly reduced serum level estrogen (estradiol 17-P) by day 67. Estrogen levels remained suppressed (P = .02) after three months of recovery in these treatment animals. There were no effects on serum testosterone levels throughout the trial. Data from the current study suggest that a daily dose of 0.044 mg/kg BW of altrenogest suppressed estrogen production and scrotal width in the two-year-old stallions, however, stallion sexual/aggressive behavior and seminal parameters were not significantly affected by treatment. This study also showed large variation in libido and sexual/aggressive behavior between these young stallions. Further research is needed to determine various doses and age effects of altrenogest in the stallion.