By Dr. Hans H. Stein

May, 2011

In the April newsletter, opportunities for using high-fiber feed ingredients in diets fed to pigs were discussed and recommended inclusion rates for a number of high-fiber ingredients were provided. It is assumed that if high-fiber ingredients are included in the diets at the recommended inclusion rates, pig growth performance will not be affected. There are, however, other consequences of using high-fiber ingredients that also need to be considered before these ingredients are included in the diets.

More bulk and reduced flowability

All high fiber ingredients add more fill and more bulk to the diet than corn and soybean meal. As a rule of thumb, the bulk of the diet will increase by 2-3% for every 10% inclusion of a high-fiber ingredient. That means that a feed bin that can hold 12 ton of a corn-soybean meal based diet can hold only 11.7 ton of a diet containing 10% of a high-fiber ingredient such as wheat middlings or DDGS. If the inclusion rate of the high-fiber ingredient is 20 or 30%, the bin can hold only approximately11.4 or 11.1 ton of feed. At the same time, most diets containing high-fiber ingredients have poorer flowability than corn-soybean meal diets. Depending on the design and dimensions of the bin, this may result in difficulties in getting the diet out of the bin. The reduced flowability may also become an issue in the feeders where diets containing high-fiber ingredients may not flow as well as corn-soybean meal diets.

Reduced pellet quality

If diets are pelleted, the quality and durability of the pellets may be reduced if high-fiber ingredients are used. The extent of this reduction depends on the other ingredients in the diet, the type of pellet mill that is used, the pellet die thickness, and the dimensions of the pellets. In general, the smaller the diameter of the pellets is, the more difficult it is to produce a pellet of a high quality if high-fiber ingredients are used. There is no definitive way of predicting the effects of high-fiber ingredients on pellet quality, but the general rule is that the greater the concentration of high-fiber ingredients is, the more difficult is it to produce a pellet of a high quality.

Increased manure production

Because the digestibility of fiber is less than that of other nutrients, more dry matter is excreted in the manure of pigs fed diets containing high-fiber ingredients. The total production of manure will, therefore, increase if high-fiber ingredients are included in diets fed to pigs and manure pits will fill up faster. Depending on the design of the pit, manure with a greater dry matter concentration may also flow less easy than manure with less dry matter and it may become more difficult to completely empty the pit. It has also been speculated that manure pits more easily will create foam if high-fiber ingredients are used in the feed, but this hypothesis has not been conclusively confirmed at this time.

Reduced dressing percentage

It has been suggested that the dressing percentage of pigs fed high-fiber ingredients is less than that of other pigs. This effect may be due to increased gut fill and possibly also to increased weight of the intestinal tract. However, in a review of 18 experiments in which DDGS was used by up to 30% in the diets, it was concluded that in most cases, DDGS, which is a high-fiber ingredient, has no influence on the dressing percentage of pigs. It therefore appears that it is not always that high-fiber diets will result in reduced dressing percentage of pigs and more research in this area is clearly needed to elucidate the impact of high-fiber ingredients on dressing percentage of the animals.

The advantage of reduced diet costs

As appears from the above, there may be some difficulties associated with the use of high-fiber ingredients in diets fed to pigs. However, the cost of high-fiber ingredients is usually less than that of other ingredients and diets are, therefore, usually less expensive to produce if they contain one or more high-fiber ingredient. This is usually the reason high-fiber ingredients are used. However, it is important that the issues discussed above are acknowledged and taken into consideration before high-fiber ingredients are included in the diets. If that is done, solutions can usually be identified and use of high-fiber ingredients does not have to create problems.