The art in formulating is not to use only good ingredients but it is to do the best we can with the ingredients we have. In this month article, I propose to review for each major ingredients the recommended maximum to manage risks of the contamination and/or anti-nutritional factors. We will look at nine major raw materials.

Vietnamese version

Corn Corn is the dominant cereal used in pig diets across the world. It is high in energy, low in fibre and protein compared to other grains. The main limitation to the use of corn is the palatability of corn when used at high doses in the diets of pigs. Publish studies show that the flavour preference for corn in pig diets declines once the inclusion rate exceeds about 40%. The palatability can be enhanced by extruding the corn. The other consideration with corn is the risk of mycotoxins. In the case of corn, the most common mycotoxin of concern is aflatoxin. If corn is contaminated though, the application of clay-based toxin binders is very effective at eliminating the risk of toxicity. (Maximum level of aflatoxin in pig diets should not exceed 20ppb). At the opposite, for maintaining acceptable meat quality at slaughter, it is advisable to include a minimum of 15-20% corn in the finisher pig diet.

Wheat Wheat is another major cereal used in the diets of pigs. Its utilisation in SE Asia is depending generally on the value relative to corn and is therefore used opportunistically. Wheat has some noticeable differences to corn, in that it is dustier during the milling process, but produces a better-quality pellet (better starch gelatinisation) and is higher in functional fibre. When utilising wheat though, it is important to ensure the soluble xylans are eliminated through the proper use of a xylanase enzyme. The high content of insoluble or NDF fibre found in wheat also has a functional benefit which is not seen in corn. It provides a stable fermentation substrate for beneficial bacterial in the colon. This can benefit growing pigs in terms of gut health and sows in terms of both gut health and milk output. Wheat has similar palatability constraints to corn and should therefore be capped in the diet at 40%. Its also important to cap wheat in lactating sow diets to avoid the incidence of twisted bowel/sudden death. Mycotoxins are again a risk in wheat and wheat by products, by the fusarium mycotoxins coming from the field prior to harvest (e.g. DON, FUM, ZEN) are generally more a concern than aflatoxins, so a more premium toxin binder is required.

Cassava Cassava and cassava by-products are an economical source of energy for swine diets. For this reason cassava is often viewed as a partial replacement for corn in pig diets. However, cassava addition in the diets has been associated with reduced growth performance, appetite, and immunity in pigs. These complications are related to

  1. the anti-nutritional factor cyanogenic glucosides linamarin and lotaustralin found in cassava. The detoxification by the pig requires large amounts of sulphur amino acids (M+C). If the detoxifying process is insufficient the pancreas, liver, kidney and thyroid function can suffer.

The level of cyanogenic glucosides in cassava can be significantly reduced by sun-drying the cassava, soaking or boiling and/or by fermenting the cassava.

  1. the dusty/bulk natural of cassava reduces palatability.

This can be partly overcome by pelleting the feeds containing cassava, and ensuring the diet has generous levels of added molasses and fats to improve texture and flavour.

  1. Fibre structure and content of cassava and cassava by-products has been shown to reduce the overall digestibility of starch and other nutrients. This reduction can be partially overcome by conservative inclusion rates of cassava and/or the application of appropriate carbohydrase enzymes (e.g. amylase + pectinase).

As young pigs are born with an immature immune system, it would be wise to avoid/limit cassava and cassava by-products until there immune system has reach maturity (7-10 weeks of age). Chronic exposure can also have health effects, so caution should be taken in using cassava in breeding animals (sows and boars).

Rice bran / Defatted rice bran Rice bran and defatted rice bran are two common raw materials which are economically competitive in the diets of pigs. The main limitation to their use is related to the very high phytate bound phosphorous level, the risk of mycotoxins and for the full fat rice bran the risk of rancidity/oxidation needs to be considered. These limitations can be easily overcome by the optimal use of phytase (formulating diets to phytate bound phosphorous and adapting the level of phytase accordingly), testing for the level of mycotoxin contamination and taking the necessary insurance in the form of toxin binders and/or mould inhibitors, and ensuring full fat rice bran is bought and used fresh, or stabilised, and additional antioxidants are applied. The application of enzymes will enhance the nutrient digestibility within the rice bran by-products and also improve its ability to act as a prebiotic and support optimal gut health.