IT STARTS FROM GOOD RAW MATERIALS
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.
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
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.
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.
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.
DDGS DDGS commonly from corn but also available from wheat and other cereals is another economical raw material which can be used in the diets of pigs. DDGS is however a highly variable by-product and should be bought wisely and used cautiously. Energy values can range from 3600 to 4300kcal ME/kg DM, while protein and lysine can range from 25-35% and 0.6 to 1.1% respectively. Its important to know the nutrient content of the product you are using and to also ensure the product is not over cooked (as this will make the nutrients especially protein unavailable to the pig). The colour should be light and the smell should be pleasant. Mycotoxins are also a risk with this type of commodity. The raw material can produce bitter flavours when used at high levels. Feeding high levels (e.g.30% DDGS) in finishing pig diets can negatively affect carcass quality through reduced dress percentage, softer fat (associated with corn oil) and an increased iodine value. These negative effects can be avoided by put pigs onto a low DDGS diet 3 weeks prior to slaughter.
Canola Canola is a modern genetic version of rapeseed and can be used more generously for feeding pigs. In countries like Canada and Australia, it is the dominant protein meal used. Canola is grown for oil production and the canola meal is the normal by-product available for use in pig diets. The oil can be extracted using cold press, expeller or solvent extraction methods, with the latter being the most efficient and therefore giving a by-product with higher crude protein and lower fat (and better stability and flowability). Challenges with canola relate to the glucosinolate level (a bitter toxin) found in the seed and the dark colour of the product. Glucosinolate levels are generally low in modern canola varieties compared to rapeseed meal. In markets where the colour of feed is important canola addition may need to be limited. The total glucosinolate tolerance level for pigs is 0.78 umol/g of diet. Iodine (1mg/kg) can be added into the diets of pigs as insurance against negative consequences when high levels of canola are being used.
Rapeseed meal Rapeseed meal is not an ideal raw material for use in pig diets due to the high levels of glucosinolates. When buying rapeseed meal, you need to know the level of glucosinolates in the product so you can adjust the inclusion rate accordingly. However, generally rape seed meal can only be used at low levels in the diets of growing pigs and is best avoided in the nursery feeds and sow feeds. The dark colour of the seed can also be an issue in some markets where feed colour is important.
Soya bean meal Soya bean meal is the most common protein meal used in pig diets. In mature pigs (>30kg live weight), the protein in soya bean meal is highly digestible (around 88%) and has a good amino acid profile. However, in younger pigs, there are some anti-nutritional aspects to soya bean meal which need to be taken into account. Young pigs (<30kg) lack the ability to excrete adequate digestive enzymes to fully utilise soya bean meal. In addition to this, soy bean meal contains trypsin inhibitors which limit the digestion of protein. The overall net effect is that the protein in soya bean meal in young pigs is estimated to be only 80% digestible. These constraints can be managed by gradually introducing the soya bean meal inclusion rate over the nursery phase. Ideal maximums would be around 5% in creep, 8% in prestarter and 12% in starter. Other soya based ingredients like full fat soya bean meal, soy protein concentrates and soy protein isolates can be used in conjunction with soya bean meal though as these are more digestible and generally contain less trypsin if prepared well.
Broken rice Broken rice is a good source of rapidly digestible carbohydrates which can be used in the diets of young pigs. Relative to other grains, broken rice is low in fibre and fat and high in starch and high in lysine relative to protein. There are no major constraints to using broken rice in the swine diets. Typically, price is the constraining factor. Unlike maize, there is no advantage to precooking (extruding) rice when being used in young pig diets. The table below is summarizing the constraints for optimisation. These values are not recommendation of incorporation but only maximum when setting the formulation software. The resulting incorporation will depend on other parameters as prices and nutritional requirement of the animal. The values may need to be adjusted depending the contamination or not of the source of raw materials, namely mycotoxins. We are recommending to regular analyse mycotoxins contents in raw materials to adjust these constraints.
To reduce contamination risks and exposure to price variability, it is actually recommended to use a mix of all these ingredients rather than focusing only on one materials.