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

• Betaine supplementation reduced serum homocysteine concentration in boars.
• Betaine tended to increase total sperm production at summer months in boars.
• The 1.26% betaine level supplementation increased percentage of sperm cells with DMR.

This study evaluated the effect of supplemental dietary betaine at three concentrations (0.0%, 0.63% and 1.26%) on semen characteristics, quality and quality after storage on boars. The trial was conducted between 22 July and 1 October 2014 in a boar stud located in Oklahoma. Boars were blocked by age within genetic line and randomly allotted to receive 0% (CON, n (line T) = 22, n (line L) = 10), 0.63% (BET-0.63%, n (line T) = 21, n (line L) = 6) or 1.26% (BET-1.26%, n (line T) = 23, n (line L) = 7). The diets containing betaine were fed over 10 weeks, to ensure supplemental betaine product (96% betaine) daily intakes of 16.34 and 32.68 g, for the BET-0.63% and BET-1.26% diets, respectively. Serum homocysteine concentrations were less for animals with betaine treatments (P = 0.016). Rectal temperatures of the boars were unaffected by betaine diets. Betaine tended to increase total sperm in the ejaculates when collectively compared with data of the control animals (P = 0.093). Sperm morphology analysis indicated there was a greater percent of sperm with distal midpiece reflex (P = 0.009) and tail (P = 0.035) abnormalities in boars fed the BET-1.26% than boars fed the BET-0.63% diet. Betaine concentration in the seminal plasma was greater in boars with betaine treatments, with animals being fed the 0.63% and 1.26% diets having 59.2% and 54.5% greater betaine concentrations in seminal plasma as compared with boars of the control group (P = 0.046). In conclusion, betaine supplementation at 0.63% and 1.26% tended to increase sperm concentration in the ejaculates by 6% and 13%, respectively, with no negative impacts on semen quality when 0.63% of betaine was included in the diet.