not significant (P > 0.05), the treatment by time interaction was significant (P < 0.01). The OG mares tended (P ¼ 0.09) to expe- rience a brief surge in LH concentrations 12 h post-treatment while the VG mares demonstrated a more gradual increase in LH concentrations through 96 h post-treatment. The percentage of mares ovulating within 48 h post-treatment was not different (P > 0.05), with 56.3 and 28.6% of OG and VG mares ovulating, respectively. OvuGel may be a useful candidate for ovulation in- duction in the mare; however, additional research is needed to demonstrate its efficacy. A larger dose or multiple doses may be required to achieve ovulation rates comparable to those obtained with currently available products. Key Words: ovulation, mare, triptorelin 128 Comparison of prolactin responses to repetitive cabergoline treatments in two consecutive years in mares E.L. Oberhaus* 1 , D.L. Thompson, Jr. 1 , N.A. Valencia 1 , and R.M. Gilley 2 1 Louisiana State University Agricultural Center, Baton Rouge, LA, USA; 2 BioRelease Technologies, LLC, Birmingham, AL, USA Two studies, one year apart, were conducted to determine the efficacy of long-term treatment with cabergoline on suppression of prolactin (PRL). In Exp 1, 12 light horse mares were randomly assigned to treatment (n ¼ 6) or control (n ¼ 6). On February 4, 2013 (d 0) and every 10 d after until d 110, treatment mares received cabergoline (5 mg, IM) while control mares received vehicle only. On d 1 and every 4 d after until d 113, jugular blood was drawn for later determination of PRL concentrations. On d 29, 59, 79, 89 and 119, mares were challenged with IV sulpiride (0.01 mg/kg BW) and blood was drawn at 0, 5, 10 and 20 min relative to injection. Radioimmunoassay was used to assess PRL concentrations and data were analyzed by ANOVA. Plasma PRL concentrations in every-4-d samples revealed that PRL secretion was suppressed (P < 0.05) by cabergoline injections through d 61; thereafter, PRL concentrations in treated mares did not differ from controls. Prolactin response to sulpiride was sup- pressed in treated mares (P < 0.05) on all days of challenge. Cabergoline administration successfully inhibited PRL secretion only up through d 61 of the experiment. To determine if the eventual rise in PRL was due to refractoriness or perhaps another factor, 8 of the same 12 treated and control mares were used the next year to determine the repeatability of the PRL response to cabergoline. In Exp 2, treatment began on April 6, 2014. The date corresponded to the rise in PRL in treated mares from the pre- vious year. On d 0, and every 10 d after until d 60, mares were treated with cabergoline or vehicle exactly as in Exp 1. Blood was drawn in the same manner every other day from d 1 until d 69. On d 29 and 69, mares were challenged with sulpiride as in Exp 1. Plasma PRL varied (P < 0.05) considerably in control mares from year 1 to year 2; however, the PRL response to cabergoline did not. Prolactin was suppressed (P < 0.05) in mares treated with cabergoline and the pattern of suppression was similar for year 1 and year 2. Prolactin response to sulpiride was greatly suppressed (P < 0.05) in treated mares on both challenge days. In conclusion, prolactin is suppressed in mares treated with cabergoline; however, suppression appears to wane in early April. Interestingly, the PRL response to a low dose of sulpiride was still greatly suppressed in treated mares, even after PRL in daily samples had begun to rise. It seems that some seasonal factor is causing the rise in daily PRL concentrations, even in the face of exogenous dopaminergic activity. Key Words: prolactin, cabergoline, mare 129 Effects of feeding a yeast-based supplement containing selenized yeast, vitamin E and a DHA-rich microalgae on sperm motion characteristics L.D. Goedde* 1 , K.M. Brennan 2 , B.A. Ball 1 , L.M. Lawrence 1 , M.H. Troedsson 1 , and E.L. Squires 1 1 University of Kentucky, Lexington, KY, USA; 2 Center for Animal Nutrigenomics and Applied Animal Nutrition, Alltech Inc., Nicholasville, KY, USA The use of cooled and frozen stallion semen has become quite popular. However, there are some stallions that have sperm that are quite susceptible to cold shock. Thus, there is a need for a product that will alter sperm so that they can withstand the stress of cooling and freezing and thus improve pregnancy rates. Studies have shown that a diet high in omega-3 (n-3) fatty acids can improve the motility of cooled and frozen/thawed sperm. Many of the omega 3 fatty acid products for stallions have low levels of docosahexaenoic acid (DHA) and are based on fish oil, which may have reduced palatability. The objectives of this study were to determine if a DHA-rich microalgae meal would enhance the motility of fresh and cooled stallion sperm. Twelve stallions, 3 to 12 y old were used. Semen was collected every other day for 2 wks (July) and sperm motion parameters (total and progressive motility) were determined by computer assisted motility sperm analysis (CASA) on the last 3 ejaculates. These ejaculates were cooled to 5C (Equitainer, Hamilton Thorne) and held for 48 h. Stallions were then paired based on CASA values for fresh and cooled semen, age of stallion, sperm output and body condition. Stallions were fed one of 2 dietary treatments for 60 d: A basal diet, Control, 0.4% BW as concentrate and 1.8% BW as grass hay, and DHA, basal diet plus 160 g of a yeast-based supplement containing selenized yeast, vitamin E and a DHA-rich microalgae (Schizochytrium limacinum CCAP 4087/2; Alltech Inc., Nicholas- ville, KY) to provide 2 mg Se, 1000 IU vitamin E and 15 g DHA. Consumption of the supplement was accepted within a few days of feeding. Beginning on d 46, stallions were collected every other day until d 60. Sperm motion parameters were assessed with CASA. Data were averaged for the last 3 collections of the pre- treatment and post-treatment and log-transformed. A paired t-test was used to compare pre- and post-treatment values within control and treated stallions. There was an increase (P < 0.05) in total motility for DHA stallions at 0 (63.6, 68.4), 24 (51.6, 58.4), and 48 (45.9, 52.1), h of cooling from pre-treatment to post-treatment, whereas means for controls were similar between pre and post- treatment samples. Also, progressive motility increased (P < 0.05) in treated stallions between pre and post-treatment at 0 (59.2, 64.8), 24 (46.1, 52.7) and 48 (40.5, 47.3) h but not in controls. Based on these data, this dietary supplement was effective in improving motility of stallion sperm after 60 d of feeding. Key Words: DHA, stallion, sperm 130 Effect of dietary omega-3 supplementation on equine endometrial and embryonic gene expression R.D. Jacobs* 1 , A.D. Ealy 1 , P.M. Pennington 2, 3 , B. Pukazhenthi 2 , L.K. Warren 4 , A.L. Wagner 5 , A.K. Johnson 6 , T.M. Hess 7 , and R.K. Splan 1,8 1 Virginia Polytechnic Institute and State University, Blacksburg, VA, USA; 2 Smithsonian Conservation Biology Institute, Front Royal, VA, USA; 3 George Mason University, Fairfax, VA, USA; 4 University of Florida, Gainesville, FL, USA; 5 Cooperative Research Farms, Richmond, VA, USA; 6 Auburn University, Abstracts / Journal of Equine Veterinary Science 35 (2015) 437e445 438