Research Note

Sows & Piglets:

Bending the Iron-Bound Challenge

Among the supplementary trace minerals in modern sow diets, iron stands out for its confounding challenge. Conventional diet supplementation — typically using ferrous sulfate — already is some 30% above current recommendations (per NRC 2012). Going higher risks serious adverse effects.

Yet despite high iron supplementation, reports in the U.S. and other countries suggest around half of gestating sows still are likely to be anemic. Sow anemia correlates with prolonged farrowing, more stillborn pigs, and increased sow deaths and culls.

Breaking this “iron-bound” challenge seems unlikely in the near term. How about bending it a little?

“Keep in mind that current mineral requirement estimates are based on studies conducted more than 30 years ago,” says South Dakota State’s Dr. Crystal Levesque. “Today’s ‘hyper-prolific’ sows are significantly heavier and farrowing and feeding more pigs.”

Levesque notes that the “direct cause” of sow anemia remains unknown. But, considering current diet supplementation levels, it’s probably not related to dietary iron supply. She points out that work with additional iron supplementation of sows — both oral and injection — had limited impact on their blood hemoglobin levels (HbC).  

“Some degree of anemia may be expected following parturition,” she adds, “considering blood loss during farrowing. However, recent studies indicate that the incidence of sow anemia increases with increasing parity. Recovery of sow blood hemoglobin appears to decline prior to, and during, the subsequent pregnancy.”

“Moreover, duration of farrowing also increases with anemia across the range of parities, which correlates with increases in piglets stillborn and sows removed.”  

Thus this research by Katlyn McClellan at SDSU raises key questions: Does the greater prevalence of anemia in older parity sows also result in a decline in iron status of the offspring? If so, is that decline caused by an increase in the sow’s iron requirements and a subsequent deficiency over time?

It’s important to note that other dietary components — especially other minerals and certain other compounds — can inhibit or possibly enhance iron uptake. On the uptake side, various phytase compounds can increase iron absorption from cereal meals, which could affect sow hemoglobin levels and overall iron status.

“From my perspective,” Levesque says, “the most critical time for adequate sow hemoglobin is just prior to farrowing. So, a strategy that can boost hemoglobin in the short term may help.”

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