The Effects of Dietary Flaxseed on Fresh and Stored Boar Sperm Parameters.

Abstract

Storage of fresh liquid boar semen for artificial insemination is associated with decreased sperm fertility, viability and motility over time. Boar sperm plasma membranes contain approximately 60% long chain poly-unsaturated fatty acids (PUFA) and the omega-3 (n-3) and omega-6 (-6) fatty acids are essential PUFA which cannot be synthesized by the animal. It has been proposed that mammals evolved on a dietary n-3 to n-6 ratio of 1:1, but the ratio in typical boar diets is 1:6, risking sub-optimal supply of long chain n-3 fatty acids for spermatogenesis. This study evaluated dietary flaxseed as a source of n-3 fatty acids on fresh and stored boar sperm. Three boars were fed for 3wk according to NRC (1998) recommendations for breeding boars, followed by an iso-caloric and iso-nitrogenous diet containing 15% flaxseed for 9 weeks. Semen was collected 2× per week and analyzed for concentration, volume, and function (motility, viability, morphology, membrane fluidity and capacitation status) during weeks 1-3 (W1/3), weeks 6 and 7 (W6/7), and weeks 10 and 11 (W10/11). Sperm function was also assessed after 5 and 7 days of storage (BTS, 17°C) at weeks 3, 7 and 11. Ejaculate volume increased through the 12 wks for each boar while concentration increased for only one boar; total sperm per ejaculate differed among periods. Total motility increased from W6/7 to W10/11 for one boar, but not the others. The percent motile sperm declined from day 0 to 5 of storage at all times, but there was significantly less loss of motility at W10/11 (p < 0.05). Mean number of viable sperm was greater at W6/7 and W10/11 than W1/3, and viability after 5 and 7 days of storage also was significantly better at W6/7 and W10/11 than W1/3 (p < 0.06 and p < 0.05 respectively). Dietary flaxseed increased the percent of morphologically normal sperm, and decreased of percent of sperm with tail abnormalities. Fluidity of the sperm plasma membrane as assessed by flow cytometry increased with the flax diet. Diet did not affect the acrosome reaction in fresh or stored sperm. These results indicate that the magnitude of the loss in sperm motility and viability following storage are reduced following dietary flax supplementation and the fluidity of the sperm plasma membrane is increased. (poster)