Two Doses are Better Than One: Research Shows Value Lies in Iron

It's no secret pigs need supplemental iron at birth. That's a question nutritionists asked and answered years ago. So why is everyone talking about iron again? New research presented at the American Association of Swine Veterinarians (AASV) annual meeting shows a second iron injection has the potential for great added value in a pork operation.

"New information is now available about how much iron pigs should get," Merlin Lindemann, professor of swine nutrition and management at the University of Kentucky in Lexington, said during his presentation at AASV. "Pigs are a different animal today, with greater genetic potential. There are new thought processes and still some new questions in nutrition."

Piglets grow five times in size from birth to weaning. As they grow, hemoglobin drops down as the pigs get little to no iron in the sow's milk. Research clearly shows the benefits of faster growing pigs, and it also shows that bigger pigs have much lower hemoglobin levels than runt pigs because they are using that hemoglobin to help them grow and it is diluted out in their larger bodies.

It's long been known there's a potential iron gap that occurs when the pigs run out of iron stores from the injection at the first processing, but before weaning. This causes many pigs to enter the nursery to become iron-deficient or even anemic explains James Pierce, a nutritionist and owner of J.L. Pierce Consulting in Nicholasville, Ky.

"Giving an extra dose of iron gives producers extra performance, less morbidity and less mortality in the barn," Pierce says. But until now, very little research has existed to help us understand how many different biological processes in the pig are affected.

Lindemann and his team went to work to study the impact of a second iron injection. A total of 144 crossbred pigs (72 barrows and 72 gilts) with an average birthweight of 2.86 lb. were assigned to either a control or added-injection treatment group. All pigs received an initial 200 mg intramuscular iron injection less than 24 hours after birth. Pigs in the added-injection treatment received an additional 200 mg of iron between day 6 to day 8.

Once weaned, the pigs in both groups were fed a common diet for the duration of the experiment formulated to supply an added 100 mg/kg iron as ferrous sulfate. Pigs were moved from the nursery to a finisher about five weeks after weaning.

"Unlike some things, where we see an advantage in a certain period of life then things regress to a norm later on, the iron advantage continues to give more value throughout the pig's life," Lindemann says. "A second iron injection results in pigs hitting the nursery in better condition and continue to perform better in the nursery with higher exit weights. That difference grows all the way to the market."

A more vigorous pig has better vitality. It's going to go to the feeder more often and fight off disease better, he points out. People who have already adopted the two-dose iron treatment say the change is something they can see in the barn.

"And if you see it in the barn, then the whole team gets on board a lot better," Lindemann adds.

In addition to the study in the barn, Pierce's group conducted a differential gene expression study which looked at the difference in gene expression as a result of one injection versus two injections. In this study, 29,000 genes were annotated. He presented a poster on his research findings at the AASV annual meeting.

"We conducted a complete sequencing of the RNA that is expressed because of one or two iron injections. That gives us a picture of why the things are happening – that veterinarians and producers observe daily – without doing any clinical work," Pierce says.

The results showed one particular gene was upregulated 40-fold, and that gene is responsible for the production of a hormone that controls iron absorption and iron regulation in the liver.

"Because this study also looked at gene expression in pigs from the litter, we can say the improvement in feed efficiency is measurable and confirmed with changes in the expression of genes associated with energy metabolism," Pierce says. "That's perhaps 6 to 8 pounds less feed for that market hog. That's a major advantage."

Lindemann admits university studies typically don't push the pigs as hard as commercial production as pens aren't as crowded and there is likely less disease stress. But, the question remains: Will the results transfer to a normal production system?

"Gene expression studies help us see changes in genes that are related to hematology and changes related to feed efficiency. We also have gene change related to gut health. And as we continue to mine that data, we may find other things and say, there's a lot of things that we never realized from a health standpoint that could be related to the mineral status, and specifically the iron status, of these pigs," Lindemann says.

It's been widely known gut health suffers in anemic pigs, Pierce explains. But his research shows this isn't necessarily due to infection as the herd in the study was negative for everything, not vaccinated for anything and uses no antibiotics. This almost-medical grade herd gave him a very clean picture of what was happening biologically between the two treatment groups.

An interesting discovery from the gene expression study was the effect iron on a group of proteins called claudins. Claudin-1 was significantly upregulated with two doses of iron compared to one, Pierce notes.

"Claudin-1 is largely responsible for what's called tight junctions between the epithelial cells of intestine, skin and everywhere cells must stick together," Pierce says. "I found that Claudin-2, a claudin protein that is expressed when we have diseased or leaky guts, was significantly downregulated. That was an exciting discovery."

When looking at duodenal and liver samples, Pierce saw a complete biochemical pathway reduction in the production of glucose from amino acids in the sow's milk. Because they were using the amino acids in the milk more efficiently for growth rather than converting them to glucose for energy, as they often do when stressed or sick.

"That also reduces the amount of urea that has to be produced in the liver to get rid of the nitrogen from the amino acids that have been used for energy," he adds. "Those two findings come together and show us energetically why pigs have poorer feed efficiency with one dose of iron."

If you could put a quarter in a slot machine and get a $5 bill back, would you do it? "Every time," laughs Pierce.

The data suggests a second dose of iron will cost the producer about $0.25 per pig for product and labor for the extra injection.

"With the increased efficiency and a cost of $340 ton/feed, that saved about $5 per pig," Pierce says. "That's a great return on investment."

Lindemann encourages producers considering moving to two doses to think about when you are picking up the pig again. Although there may be an ideal timing of the second dose, he says there is some flexibility in that recommendation.

A second iron treatment not only covers any pigs that were missed or didn't quite get the full dose the first time, but it also gives the pigs that received the first dose of iron an added boost.

For Pierce, the takeaway is simple.

"Regardless of the quality of your health, management, facility or genetics, if the pigs don't have adequate iron, they simply can't perform to their maximum potential," Pierce says. "It literally distills down to that."

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