About 18 months ago, we at the Abilene Animal Hospital stumbled across some information while researching PFTS (porcine failure to thrive syndrome) that made us think that perhaps there was a link between failure to thrive and vitamin D deficiency.
Research in other species, especially dairy, but also including humans, reminded us of the importance of vitamin D in bone development, growth and immune response.
In 2010, University of Wisconsin scientists presented a poster at an animal science meeting showing that vitamin D deficiency caused kyphosis (commonly referred to as a “humpback pig”). A follow-up trial found the same thing.
This evidence helped spur frenzy in the pork industry of supplementing baby pigs with vitamin D to solve all sorts of issues. We were just as excited as everyone else with the prospect of solving some fairly complex issues such as PFTS, immune challenges and kyphosis with something as simple and inexpensive as vitamin D, so we embarked on a journey to find the answers.
Research on Vitamin D
Background research revealed the normal vitamin D levels to have ranges of 25-30 ng/ml serum 25(OH) D for 3- to 4-week-old pigs. We found that most pigs reared in confinement systems had levels below 10ng/ml. Literature states that <15ng/ml would be considered deficient and cause bone deformation. Pigs reared outdoors (a rarity in large-scale production these days) had high levels (>50ng/ml) of 25(OH)D. Many veterinarians, animal scientists and researchers collaborated to find answers.
A 2,000-sow, farrow-to-finish farm weans 900 pigs per week into nurseries. The herd was known to be negative for porcine reproductive and respiratory syndrome and Mycoplasma pneumonia. Piglets were vaccinated for circovirus at weaning and again three weeks later. Incidence of kyphosis (“humpback” pigs) in the nursery varied from 0.1% to 6.7%. The alarming problem was four months of greater-than-3% cases.
Multiple attempts were made to necropsy the affected pigs and find the cause. No infectious or physical causes were found. The flare-ups were extremely frustrating.
After reading the University of Wisconsin studies, we wanted to try vitamin D. A plan was implemented to dose the piglet orally at processing (Day 1) with 40,000 IU vitamin D. The initial results reduced the incidence of kyphosis by half, but not consistently to levels that were acceptable.
During further investigation, we learned that there is an interaction between vitamin D and rotavirus diarrhea. In the piglet’s body, vitamin D is normally cycled through the liver, secreted in the bile that enters the small intestine and reabsorbed by the pig, so it can continue to be used.
When pigs have rotavirus diarrhea, the absorption rate is significantly reduced because of the destruction of the intestinal villi, so the vitamin D is not reabsorbed and the supply is depleted.
We could now correlate the problems with diarrhea to the problems with kyphosis. Now the question still remains if pigs need supplemental vitamin D to prevent kyphosis, or is it just cheap insurance against variable levels of malabsorbtive diarrhea?
Multiple growth trials done in the last 18 months to measure the growth benefit of adequate vitamin D levels in growing pigs have produced variable results. But the overriding conclusion is that there seems to be no great advantage to pig growth by supplementing otherwise-healthy piglets with oral vitamin D at processing.
Growth trials are a great deal of work, because all the pigs must be weighed individually. But the results are fairly black and white. The pigs given additional vitamin D either grew better than their non-supplemented cohorts, or didn’t.
Several trials measuring the piglets’ ability to respond to various vaccination and disease challenge protocols are underway. They are measuring immune function by monitoring titer response to vaccine and perhaps more importantly, piglet survival and performance post-disease challenge. These trials are both expensive and time-consuming. Hopefully, the reward for the collaborators will be results that lead the way to producing healthier pigs in a cost-effective manner.
We are continuing to learn more about vitamin D. Research abounds in human medicine as well. In addition to bone health and improved immune health, vitamin D is purported to help prevent depression and wrinkling in people. We have no work in progress to measure the mental health of the piglet, or whether our older sows are less wrinkled. For now we have our hands full just tackling the measuring of immune response.