Supplementing for Semen Quality

Cooling and freezing equine semen damages cell membranes, which results in loss of motility and general viability known as "cold shock." Most domestic species have high concentrations of polyunsaturated fatty acids (PUFAs) in the semen, but the amounts of these PUFAs, particularly DHA, an omega-3 fatty acid, and DPA, an omega-6 fatty acid, vary by species. These variations influence susceptibility of semen to cold shock. Unfortunately, boar and stallion semen have a low DHA:DPA ratio, which is associated with increased susceptibility to cold shock and decreased fertility.

Animals get the precursors for PUFAs in their diet. The problem is that most commercial horse feeds are high in precursors for DPA, but not DHA. This led researchers from Texas A&M University, including Steven Brinsko, DVM, PhD, Dipl. ACT, in conjunction with Minitube of America, to design an experiment to determine if adding a DHA-rich nutraceutical (supplement) to stallions' diets could increase the DHA:DPA ratio and improve the quality of fresh, cooled, or frozen-thawed semen.

Eight breeding stallions were randomly assigned to treatment or control groups. For 14 weeks the treatment group received 250 grams of a commercial boar nutraceutical designed to increase DHA concentration. Stallions were then examined and semen collected for analysis. After a 14-week "washout" period, horses in each group were switched and the trial was repeated. Semen samples from treatment and control groups were analyzed for DHA and DPA concentrations. The remaining semen from each sample was divided for fresh, cooled, and frozen semen analysis.

The results indicated that stallions fed the nutraceutical had an average sperm concentration that was 1.8 times higher than stallions fed the control diet. The concentration of DHA per billion sperm was almost three times higher in stallions fed the nutraceutical. In addition, when examining the DHA:DPA ratio, stallions fed the nutraceutical experienced a 1.5-fold increase in the ratio compared to control stallions. Finally, stallions fed the nutraceutical experienced significant improvements in sperm motility for fresh, cooled, and frozen semen samples. "Motility, especially progressive motility, is commonly used to assess viable numbers of sperm," explains Brinsko. "The increased percentage of motile sperm in the cooled semen from the stallions fed the nutraceutical means that increased DHA in the semen also increased the number of sperm capable of fertilizing an egg."

Brinsko, S.P.; Varner, D.D.; Love, C.C.; et al. Theriogenology, 63: 1519-1527, 2005.

About the Author

Susan Piscopo, DVM, PhD

Susan Piscopo, DVM, PhD, is a free-lance writer in the biomedical sciences. She practiced veterinary medicine in North Carolina before accepting a fellowship to pursue a PhD in physiology at North Carolina State University. She lives in northern New Jersey with her husband and two sons.

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