A recurrence of mulberry heart disease (MHD) is likely due to a whole new set of factors. Linked to oxidative imbalance, changes in sow diets may be responsible for the damage to heart muscle that leads to sudden death in weaned pigs.
Veterinary consultant Roy Schultz of Avoca, IA, believes the mulberry heart that’s dropping pigs may be related to distiller’s dried grains with solubles (DDGS) in sow diets. And there’s good theory behind the relationship, he says.
High levels of oxidative fatty acids and sulfur in some distiller’s grains “tie up” fat-soluble vitamin E and selenium in sows, Schultz points out, leading to deficiencies in the colostrum. Without the vitamin E and selenium transfer in the sow’s milk, pigs become more susceptible to oxidative imbalance and reduced performance.
Research led by University of Minnesota swine nutritionist Jerry Shurson is measuring the level of lipid oxidation in a variety of fat sources, including DDGS.
“We’re looking at the connection,” Shurson says. “If we’re feeding diets high in oxidative fats to sows or growing pigs, we may not be providing enough vitamin E and perhaps selenium to counteract compounds like free radicals, peroxides and other things that cause cell damage and lead to increased mulberry heart disease.”
DDGS contain 10% corn oil, which in turn contains a high amount of linoleic acid, a long-chain poly unsaturate that is susceptible to oxidation and a likely contributor to oxidative imbalance. DDGS are going into sow diets at levels as high as 50% in Minnesota studies. That’s a heavy dose of corn oil for animals that never received such high-fat diets before, Shurson notes. The amount of oxidative fats depends on the source of DDGS, he adds.
Shurson’s preliminary research found that of the 32 ethanol plants tested, the highest oxidative sample was five times greater than the lowest.
“It gives an idea of the range in oxidation levels,” Shurson says. “Feeding high levels of DDGS for a continuous period with marginal vitamin E could theoretically contribute to some of these mulberry heart problems.”
Vitamin E is a natural antioxidant, but is expensive to use at high levels. Shurson is seeking funding to compare synthetic antioxidants to alpha tocopheral, the preferred and most active form of vitamin E.
Schultz suggests his clients feed synthetic antioxidants to offset any oxidation imbalance. He uses a product from Novus International called Agrado Plus. Used at a half pound per ton of feed, the product costs $1.65 to $1.70/ton of finished feed and claims to enhance oxidative balance by neutralizing free radicals.
Heart muscle is particularly sensitive to oxidizing agents, notes Chad Hagen, swine nutritionist and vice president of Value-Added Science and Technologies (VAST), a Mason City, IA, company he co-founded in 2007.
“It’s possible the increased incidence of mulberry heart could be due to high levels of DDGS being used in sow diets,” Hagen says. “Some sources have elevated levels of oxidized fatty acids. That said, we work with many producers who add high levels of DDGS in sow diets and are not experiencing problems with mulberry heart, which indicates there are other factors involved.”
Sulfur levels are another factor, and it is antagonistic to selenium absorption, Hagen says. VAST offers a trademarked tool called Illuminate Services that shows wide variation in sulfur levels in DDGS sources.
Illuminate is a DDGS analysis service that uses a proprietary technique to determine accurate nutrient profiles. Those profiles are added to a growing VAST database that contains thousands of samples from over 70 ethanol plants. Rations are formulated using the nutrient compositions at least cost (see http://nationalhogfarmer.
Hagen offers the following advice to counter sudden death from MHD:
• Select a high-value source of DDGS.
• Use organic selenium in diets.
• Make sure vitamin E and selenium levels are optimum in both sow and nursery diets. Injectable vitamin E is not necessary.
• Consider using an antioxidant product like Agrado Plus in diets containing high levels of DDGS.
With or without mulberry heart, colostrum management is critical.
“We believe it is more critical in herds with mulberry heart,” Hagen says. “Split suckling and hot boxing are important tools to ensure adequate colostrum management. We also believe that farrowing induction can reduce colostrum quality and are in favor of minimizing its use. There are also tools available to improve colostrum quality.”
If MHD is suspected, Schultz says it’s important to differentiate the malady from diseases like Strep suis, Hemophilus parasuis and gut edema. A good pathologist will see the gross lesions on the heart.
Debra Neutkens is a freelance writer from White Bear Lake, MN.
Assessing Supplementation for Mulberry Heart
While it is true vitamin E and selenium supplementation are involved with mulberry heart disease (MHD), new research at Iowa State University (ISU) points to other risk factors.
Steve Ensley, DVM, a toxicologist at ISU’s Veterinary Diagnostic Lab, says increased incidence of MHD prompted a study in 2008 that just now is being published. The investigation was triggered by the fact that MHD was not responding to vitamin E/selenium supplementation as in the past. “We had a lot of questions, including whether it was due to DDGS in sow diets or infectious agents,” Ensley says.
Production sites involved in the ’08 study were high-health herds that did everything right, he explains. Tissue samples from 83 pigs from 38 farms were analyzed for vitamin E, selenium and 13 other minerals. The farms had a history of increased MHD cases with 1 to 10% affected by sudden death.
Results of the study, “Assessment of vitamin E levels, selenium levels and presence of viral pathogens as the etiology of mulberry heart disease,” were presented at the 2010 American Association of Swine Veterinarians annual meeting. Ensley and his co-authors reported no new infectious agents were found in MHD, nor did they see a vitamin E/selenium deficiency associated with MHD.
“Mulberry heart is responsive to vitamin E and selenium, but it’s not related to a deficiency in the pig. That is pretty new information,” Ensley notes. Experimental diets had adequate selenium and sometimes levels double and triple the legal limit of 0.3 parts per million.
“We think it’s more of an antioxidant condition in rapidly growing animals,” he continues. “The reason selenium and vitamin E worked in the past was they were natural antioxidants that protected pigs from oxidative intermediates present during rapid growth.
“Now the biggest risk factor to non-responsive MHD is high-health herds — herds that did not have porcine reproductive and respiratory syndrome (PRRS), were on a good circovirus vaccination program and did not have disease pressure. When infectious agents that could potentially slow growth are removed, those were herds with high incidence that we couldn’t control, he says.”
Ensley says the window is narrow after weaning, with MHD hitting pigs at 5 to 21 days of age. Once pigs have adjusted to feed and their growth rate has stabilized, the risk is much lower.
Iron dextran injections, too, can be a risk factor, Ensley adds. Iron is an oxidant and uses some of the antioxidant capabilities of the pig.
“We don’t want to discourage anyone from increasing vitamin E levels,” he continues. “We still think it’s an antioxidant condition. But boost only vitamin E. Selenium has a narrow safety margin, so we have to be very careful. We saw selenium concentrations in the liver that approached toxicosis in this study.”
Ironically, the highest risk producer for MHD is the one doing the best job, Ensley points out. “Genetics are so high, disease control and nutrition are so good, and then boom, the animal can’t compensate for rapid growth, and we’ve got a pig that has outgrown our ability to provide nutrition.”