Vitamin D in swine diets: What’s the scoop?

Over the past 20 years, vitamin D is not a topic that has gotten much attention in the swine industry – at least not until very recently. The industry has asked a lot of questions about vitamin D this past year and, depending on who you ask, you can get very different answers. Vitamin D is not an easy vitamin to define simply because it isn’t just a vitamin. It is a steroid hormone derived from cholesterol and plays a role in many areas of the body, such as calcium, phosphorus and magnesium absorption, maintenance of calcium-to-phosphorus ratios, immune function, and regulation of calcium levels for bone formation. Because it has such a wide range of functions around the body, there are still a lot of “unsolved mysteries” surrounding vitamin D. Recently, we’ve seen an increase in metabolic bone disease around the country.  Because vitamin D plays an important role in bone formation, it has been further investigated to potentially combat this issue.  Additionally, vet groups claiming to see an improvement in nursery pigs given oral supplemented D₃ (the form of vitamin D most readily used by the pig’s body) have further compounded questions as to whether modern pigs raised in confinement are receiving enough dietary vitamin D₃. When considering such questions for your farm, it is important to remember your reference point for comparing serum D₃ levels. Much of our industry standard D₃ levels were established back when pigs were raised outside with exposure to natural sunlight. Today’s confined pigs, raised indoors, will have lower serum D₃. However, this does not necessarily mean that today’s lower levels are low enough to cause the pig growth or performance problems. For relatively inexpensive insurance against potential vitamin D deficiency issues, Vita Plus and most of the industry has supplemented D₃ at levels above dietary NRC and swine nutrition guide recommendations.  Therefore, before we limit our view to one issue, it may be important to ask, “What else may have changed?” If all of the pigs that are measured today have low D₃ levels, then it may be time to reevaluate the definition of “low” and  “normal” to better match today’s production practices. Many supplemental vitamin D products have been popping up the last year and a recent Kansas State study evaluated what this can mean for 25(OH)D₃ serum levels, bone formation, and growth performance. In this study, researchers saw increased serum levels as more D₃ was supplemented. However, they saw no statistical difference in bone formation or growth performance. In conclusion, there are still many unknowns about the basic biology of vitamin D₃ function that still need to be answered before assumptions can be made as to the potential benefits vitamin D₃ supplementation.  We need to more information to determine if the additional costs really will result in guaranteed performance gains. This information was originally presented at Vita Plus Swine Summit 2012.

About the author:  Julie Salyer previously provided technical support for Vita Plus field and sales staff and conducted nursery research trials as a swine nutritionist.  Salyer received her bachelor’s degree at The Ohio State University and master’s degree in swine nutrition at Kansas State University.  She is originally from southwest Ohio, where she raised and showed livestock for the county 4-H fair. She was also a student worker at Ohio State’s swine farm and completed an internship in North Carolina for Murphy Brown LLC, which she says was instrumental to where she is today.  Salyer is active in church and enjoys hunting, kayaking, hiking and spending time with her husband, Brandon, and their two dogs.