Humans enjoy a select group of foods and supplements, as well as sunlight, to help boost vitamin D levels to ensure health and wellness. But for today’s pigs, meeting those nutritional needs is much more complex.
For starters, pigs receive only a little vitamin D, a fat-soluble substance needed for growth and bone development, from sow’s colostrum, and almost none from sow’s milk, explains Steve Henry, DVM, Abilene Animal Hospital.
Henry and colleagues at the Abilene (KS) Animal Hospital made these discoveries while investigating structural problems in pigs diagnosed with periweaning failure-to-thrive syndrome (PFTS).
Turns out these pigs are candidates for rickets along with health issues that impede their growth and performance. Some of these pigs heal naturally, but several in the groups the clinic has tested over time have had skeletal problems.
Clinic swine veterinarian Megan Potter made a startling discovery: serum concentrations of vitamin D levels in the PFTS piglets ranged from almost undetectable levels up to about 3 nanograms/ml. of blood. She and associates also bled pigs from 10 herds of normal, 3-week-old pigs and learned the readings were the same as those of the PFTS pigs. This suggested vitamin D deficiency may be widespread.
Recent analyses from serum samples collected by Abilene Animal Hospital and Iowa State University and analyzed at Heartland Assays (www.HeartlandAssays.com) confirmed that pigs have lower-than-expected concentrations of vitamin D at weaning. Those levels are considered inadequate for proper bone development and overall health in young pigs.
Those concerns spurred Henry to collaborate with researchers Ron Horst of Heartland Assays and Jesse Goff of Iowa State University to find a way to provide piglets with vitamin D. The pair developed an oral bolus dose that can be given to 2-3-day-old piglets to boost serum levels until pigs reach weaning and are placed on feed that can be supplemented with vitamin D as necessary. Henry reports the solution consists of vitamin D with peanut oil that enhances absorption by the pig.
To test the value of vitamin D supplementation in piglets, Kansas State University (KSU) graduate student Josh Flohr led a team of KSU researchers in reviewing product supplementation at two levels, 40,000 and 80,000 international units, against a control model. In a 52-day trial, 270 pigs from 29 PIC litters were dosed at two days of age. Pigs were weighed and bled at periodic intervals before weaning. On Day 20, pigs were weaned and placed in a nursery and fed standard diets. Thirty pigs were also necropsied — 18 preweaning and 12 postweaning.
Increasing oral vitamin D3 levels increased serum concentrations on Day 10, 20 and 30, compared to control group pigs, and treated pigs were 0.3 lb. heavier than control pigs whether dosed with 40,000 or 80,000 international units of vitamin D. But during the nursery phase (Day 20-52), no significant differences were seen in average daily gain, average daily feed intake or feed conversion. On Day 52, pigs previously dosed with vitamin D3 were 0.5 lb. heavier than control pigs.
However, the KSU research showed that oral vitamin D supplementation did not influence growth performance nor bone measurements. And surprising to Henry and colleagues, serum 25 (OH) D or 25-hydroxy
vitamin D in pigs treated preweaning had returned to values of untreated control pigs by Day 52.
Henry says at this point, the data is not conclusive as to actions that need to be taken in light of vitamin D deficiencies in piglets. But there’s no doubt that vitamin D supplementation producing a heavier weaned pig is a positive development. In his experience, preweaning mortality rates have declined, but that hasn’t been the case for everyone, he says.
“When you boil this all down, it appears to be very much like iron. When pigs are raised indoors, they are going to be vitamin D deficient,” he says. Ironically, pigs left out in sunshine are the most efficient at using sunlight to produce vitamin D in their skin of all of the domestic animals.
The biggest debate in veterinarians’ minds has focused on how to supplement pigs, Henry notes. Providing oral supplementation seems to be the best approach because the product is classified as a nutrient, not a pharmaceutical. This eliminates lengthy steps and added cost to license a product through the Food and Drug Administration. Oral nutritional products simply require state licensing. Mixing vitamin D with an iron product, a common request, won’t work because the oxidative properties of iron would destroy vitamin D.
Goff and associates developed a vitamin D product known as Wean-D manufactured by GlycoMyr, Inc. (www.glycomyr.com) that contains 40,000 international units of D3 available in a palatable mix to be given orally in a single dose to piglets in the first week of life. Product cost is $65 for 1,000 doses or an estimated
This issue has been casting a shadow over the swine industry ever since pigs were moved indoors, but recent events bear out production changes that have exacerbated this situation, Henry says.
He speculates that the vitamin D deficiency became clinically apparent with the swine industry’s move to 21-day weaning. “Genetics have improved and now instead of a 10- lb., 14-day-old weaned pig, we have a 21-day-old pig that weighs 16 lb. That pig started out as a 3-½-lb. pig, and in 21 days has increased its weight five-fold, on the same supply of vitamin D that it had before,” he explains.
Producers have tried to compensate by placing nursery pigs on diets supplemented with vitamin D. But with vitamin D, that doesn’t work. Once the vertebral bone damage is done in the young pig, it cannot be reversed, Henry says.
Important First Step
Vitamin D deficiency is much more than a vitamin nutritional issue; it’s a secosteroid encompassing all facets of pig biology, affecting all the cells in the body and playing a huge role in immunity, Henry explains.
Continuing concerns over PFTS and now vitamin D deficiency are being addressed in many fields by a research consortium Henry established at Kansas State University, Iowa State University, the University of Saskatchewan, the University of Guelph and USDA’s Plum Island Animal Disease Center. Funding has come from the Canadian government and the National Pork Board.
Oral supplementation is an important first step in producing normal weaned pigs that have an opportunity to thrive.
“I think we’ve made a huge step. I think if we have done nothing else, we have helped pigs to survive to weaning that are structurally more sound,” Henry asserts.
The next steps in figuring out how to solve related metabolic, physiologic and health issues will require the scientific collaboration of many colleagues, he adds.
Learn more details in the related story, "Vitamin D-Treated Pigs Perform Better."