Forages in Swine Diets
Forages in the form of pasture, as part of a complete feed, or silage, can
be used successfully in pork production. Prior to 1950, pasture was considered
a vital component in most swine feeding programs because it provided vitamins,
minerals, and unidentified growth factors. Forages may have special applications
in diets for organic swine production. Forage species, maturity, growing conditions,
and grazing habits of pigs all influence the nutritional value of the forage
consumed. Unfortunately, there are few data available to estimate the quantity
of forage consumed by pigs and the nutritional value of that forage. Consequently,
most nutritionists give little or no nutritional credit to the forage when
formulating diets for pastured pigs. Stored forage used in the diet or fed
as silage can be analyzed for nutrient content. Nutrient content of the forage
can be considered in diet formulation realizing that digestibility of those
forage nutrients generally is lower than that of grains. Pork Industry Handbook
(PIH-126), Forages for Swine, outlines some specifics on utilizing forages
for swine. Some observations from that document include:
- Due to high fiber content and low energy density, forages have only limited
use for young pigs (especially those weighing less than 40 pounds) and lactating
sows.
- Forages are best utilized at an early stage of maturity.
- Pigs absorb more nutrients from forages after an adaptation period of at
least two months.
- If forages make up more than 25% of the total diet, the crude protein content
of the complete feed should be slightly higher than typical corn-soybean
meal diets due to the lower protein digestibility of forages.
- When pastures are the forage source, pasture rotation should be used to
prevent heavy parasite and bacterial contamination of pigs.
- Forages can be heavily damaged by grazing swine, especially with rooting
in the spring and fall. Reduced stocking density will protect pastures and
support greater persistence. Ringing of sow snouts can reduce damage, but
ringing may be considered mutilation and may not be allowed under some market
certification standards.
- Hogs on pasture may grow slower and require more feed per unit of gain due
to high fiber intake and increased exercise compared with confinement-raised
pigs.
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