The changing of seasons may result in seasonal Vitamin D deficiency in sows, according to research, which shows that supplementation of the “sunshine vitamin” becomes especially important in sow performance as the hours of natural sunlight dwindle into winter.

According to Dennis Short, Ph.D., swine nutritionist for Purina Animal Nutrition LLC, Vitamin D is one of the essential vitamins in sow rations year-round. Though the typical requirement for this micronutrient is only 0.004 pound of a vitamin D 500,000 International Units (IU) per gram premix per ton of swine finishing feed, adequate levels are necessary to promote herd health. As natural sunlight becomes less prevalent, ration supplementation of Vitamin D becomes even more important.

“From October through February, we don’t see as much Vitamin D available to the sow because of reduced photochemical conversion from the sun,” said Short. In addition, UVB (ultraviolet B, which converts 7-dehydrocholesterol in the animal’s skin to Vitamin D3) does not readily pass through glass for sows housed indoors even if windows are present.

As a result, sows are more prone to Vitamin D deficiencies in the winter months. Without proper levels of Vitamin D, sows can experience osteomalacia, higher levels of lameness, decreased feed intake, reduced nutrient absorption and produce lower quality colostrum. Meanwhile, pigs raised by Vitamin D-deficient sows may have more significant levels of lameness and locomotive disorders and a greater potential for hypocalcemia, rickets and mortality. 


When it comes to locomotion issues, Short said he has seen numbers increase steadily within the industry. In fact, the Iowa State University’s Veterinary Diagnostic Laboratory saw 10 cases of metabolic bone disease in 2003. The number grew to 40 in 2011. Mineral deficiencies may be a contributing factor to increased levels of sow lameness. 

“Many cases of metabolic bone disease are caused by low dietary mineral levels,” said Short. “To prevent metabolic bone disease, sows must be fed a mineral mix that provides the proper levels of calcium, phosphorous and Vitamin D.”

Vitamin D is also a key driver of colostrum quality. Because pigs are born with relatively low levels of the vitamin, high quality colostrum produced by the sow can help the pigs better reach their full potential. “Colostrum is a fairly rich source of Vitamin D,” said Short. “When we have larger litters, each pig receives less colostrum and may experience lameness and/or health issues later in life. Supplementing sows with Vitamin D can improve nutrient levels provided to the pigs through colostrum and through lactation.”

Many industry groups and researchers have recognized the need for additional attention to Vitamin D. The National Research Council of The National Academies recently increased their Vitamin D requirement fourfold for gestating and lactating sows to 800 international units per kilogram (IU/kg) (90 percent dry matter). When selecting vitamin and trace mineral supplementation, Short said he encourages producers to work with a nutritionist to create the proper combination and mixture of Vitamin D and other essential vitamins.