Effect of natural betaine on estimates of semen quality in mature AI boars during summer heat stress

Abstract Text: This study determined the effect of supplemental dietary betaine (BET) at three concentrations (0.0, 0.3 and 0.6%) on sperm and semen characteristics, quality of fresh semen and quality after storage on boars. The trial was conducted between July 22^nd and October 1^st, 2014 in a boar stud located in Oklahoma. Two genetic lines were used, a synthetic terminal line (n = 66) and a Large White line (n = 23) with an average age of 22.3 ± 10.2 months. Treatments were allocated within genetic line and age range. The BET diets were fed over 10 weeks, to ensure supplemental BET product (96% betaine) daily intakes of 16.3 and 32.7g, for BET 0.3% and BET 0.6%, respectively. Blood samples were collected from 89 boars at days 9, 45 and 73 after betaine supplementation started. Weekly ejaculates from 89 boars were evaluated (32, 27 and 30 boars of the control, 0.3 and 0.6% BET treatments). No significant differences were found for serum homocysteine concentration after 9 days of BET feeding. However, after 45 and 73 d of BET supplementation, serum homocysteine concentrations were reduced for boars receiving 0.3% and 0.6% treatments (42.3, 30.7, 35.2 at d 45 and 42.7, 33.1 and 39.3 μmol/l  at d 73 for the 0, 0.3 and 0.6 % BET treatments, P = 0.009 and P = 0.043, respectively). Rectal temperatures of the boars were unaffected by BET diets. There was a tendency for total sperm produced in the ejaculate to increase with BET supplementation (P = 0.093), the 0.3% treatment boars had 5.9% greater and the 0.6% BET boars had 12.9% greater total sperm than the control boars. Boars on 0.3% and 0.6% treatments had 59.2% and 54.5% greater seminal plasma BET concentrations than control boars (P = 0.046). Sperm morphology analysis showed a greater percent of sperm with distal midpiece reflex (P = 0.022) and tail (P = 0.091) abnormalities in BET 0.6% treatment. In conclusion, BET supplementation tended to increase total sperm production, increased BET seminal plasma concentration and decreased serum homocysteine concentration. 

Keywords: Betaine, homocysteine, boar sperm, semen analysis