Low levels of dietary selenium and vitamin E will lower a boar's semen quality, leading to a boar's failure to fertilize sows and gilts or small litters. Research conducted at Ohio State University by Don Mahan and other animal scientists bears this out.

In the research, boars fed a diet low in selenium were compared to boars fed a selenium-fortified diet. The selenium-fortified boars had 62% normal sperm. The selenium-deficient boars had less than 25% of their sperm with normal, straight tails.

The fertilization rate of the two boar types also was tested by inseminating gilts and measuring how many eggs were fertilized. The sperm from the selenium-fortified group fertilized nearly 99% of the eggs, compared to 74% by the unfortified group.

Selenium helps form the thick part of the tail in boar sperm. A strong, straight tail moves the sperm along the reproductive tract to the sows' and gilts' eggs. Low selenium may cause sperm with bent or hooked tails. These tails slow sperm movement, making fertilization difficult.

Low levels of vitamin E in a boar's diet also can affect sperm quality, but not nearly as much as selenium, Mahan said.

Research showed boars fed a diet fortified with vitamin E had nearly 45% normal sperm compared to unfortified diets with 42% normal sperm. Fertilization rates of the two groups were similar.

Most hogs are fed diets fortified with 0.3 ppm selenium, which is enough to maintain good sperm quality. If a selenium deficiency is suspected, it is easiest to feed a selenium-fortified diet. It will take 60 days for the deficiency to be corrected, Mahan said.

Researcher: Don Mahan, Ohio State University, (614)292-6987.