Most nursery diets exceed the iron requirements prescribed by the National Research Council (NRC).
In fact, postweaning diets often have high iron concentration in dicalcium phosphate, limestone, blood meal and other compounds used in diet supplements.
However, not all of the iron is absorbable. The NRC iron requirements are based on research from the 1960s.
Scientists at Michigan State University decided to evaluate the iron needs of today's young pigs.
A total of 225 pigs were weaned at 19 days of age weighing an average of 14 lb. They were placed on one of three dietary phases:
Base diets were supplemented with one of five treatments: 0, 23, 45, 91 or 136 g. of iron/ton of diet as ferrous sulfate, a highly available source of iron.
Performance was recorded. Pigs were bled to measure iron levels. Whole-body and liver mineral concentrations were analyzed at the start and end of the 35-day feeding trial.
Overall, iron supplementation improved the gain-to-feed ratio, average daily gain, average daily feed intake and iron levels (Table 1).
Baseline iron liver scores reflected pigs being injected with iron dextran at 1-2 days of age (Table 2).
After the feeding trial, the liver iron levels increased in pigs in response to dietary supplementation. But the liver iron concentration of all pigs killed on Day 35 was less than the baseline iron levels in pigs (Table 2).
In summary, even though feed ingredients provided iron levels in excess of the NRC requirements for nursery pigs, levels were not sufficient to sustain the iron status of these pigs.
Therefore, nursery diets must be supplemented with 91 g. of iron/ton of diet from a highly available source of iron such as ferrous sulfate.
Researchers: Mike Rincker, Gretchen Hill, Jane Link, Jason Rowntree and Allison Meyer, Michigan State University. Contact Hill by phone (517) 355-9676; fax (517) 432-0190; or e-mail email@example.com.
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