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Experimenting with cereals

This article does not deal with any new cereals; instead, it deals with using them in pig formulas. These cereals have always been on the sidelines, due to tradition, availability, or lack of information.

Of course, what might be a ‘common’ cereal for one place, could easily be an ‘exotic’ in another place. A prime example is the case of wheat versus maize. In areas, wheat is the major cereal grown, producers, nutritionists, and feed mills are all accustomed using formulas based on this cereal, and rather apprehensive when presented with maize-based formulas. The opposite is true in areas where maize is the common cereal. To this end, information on all cereals is presented here to enable those less familiar with other cereals to consider using them in their formulas. Naturally, this resurgence of interest in alternative cereals is nothing but a response to the on-going crisis in the market of cereals that has created a gap in the supply of feed-grade cereals. And, according to market authorities, this crisis will continue as long as a substantial part of global cereal production is diverted for biofuel production.
Below is a list of cereals that can be used to replace common cereals in times of crisis. As a general advice, it pays to be conservative in the beginning when using a novel ingredient. So, as a rule of thumb, do not replace more than 50% of existing cereal source with a new one until more experienced is gained with the new ingredient. Not only animal performance must be monitored (and formulas adjusted as required), but also the grinding-mixing-pelleting characteristics of the new cereal must be studied and adjustments made to the process. Only then, should higher levels of inclusion be attempted.
Maize (or corn as it is called in the Americas) is certainly an excellent source of energy for pigs. It is the cereal, along with rice, that causes the least, if any, problems from a nutritional point of view. It can be said only that maize is so low in fibre that most diets require an additional source of fibre, in the form of wheat bran or soy hulls, especially for gestating sows. In general, maize can be the only cereal in a pig formula. It should be noted, however, that maize produces softer and more yellow fat than wheat and barley, and because of that, its inclusion level may need to be monitored in the final diet before market, depending on slaughterhouse requirements. Maize contains less protein (amino acids) than wheat and barley, but more energy. Nevertheless, maize-based diets properly balanced in these nutrients provide comparable growth performance to that achieved with existing diets based on wheat and barley.
Wheat is the grain of choice for nursery diets in many countries around the world, even where maize is locally available. Apart from a slightly lower energy content than maize, wheat has always supported good performance in pig diets (see Table). Actually, taste preference studies demonstrated that wheat is the cereal of choice for piglets, when compared to corn, barley, and oats. However, there is a great amount of variability among wheat varieties, and even within batches of the same variety, and this has been hypothesised as the cause of variable performance in many studies. Fine grinding (less than 600 μm) of wheat will improve nutrient utilisation (and potentiate ulceration causative factors) but it will also cause feeder bridging when diets are fed in meal form. On the other hand, coarse grinding (greater than 1200 μm) will result in lower digestibility and increased nutrient excretion – a waste of nutrients and money.
Thus, medium grinding (between 600 and 800 μm) seems to be the option preferred for the above reasons. Soft and hard varieties have been shown to support equal performance in nursery pigs, when of equal quality. In a few words after considering cost, quality is the key word in feeding wheat to pigs. To this end, it has been clearly demonstrated that using the correct enzyme (xylanase) can increase the nutritive value of wheat. As mentioned above in the case of maize, wheat produces white lard, which is preferred in many areas of the world.
Sorghum is also an excellent cereal, especially the variety Milo (which is the one cultivated in the Americas). Sorghum contains about as much energy as wheat and in protein quality it resembles maize. Most modern Milo strains are very low in tannins (anti-nutritional factors that depress feed intake). In general, yellow varieties are safer than dark-seeded varieties. A simple tannin analysis should always be performed in new batches. With levels below 0.5% tannins, few if any problems should surface even if sorghum is used as the only cereal in pig formulas. As a precaution, however, it is best to begin with levels up to 50% of total cereal participation, and even less (25% of cereals) for diets given to very young pigs. Sorghum is also best ground to a particle size similar to maize.
Rice is grown mainly for human consumption and as a result its use in pig diets is rather limited. However, when good quality rice flour (no hulls) is available, performance can be equal or even better when compared to the performance of maize-fed pigs. Brown rice, rice bran, and rice hulls are not recommended for young pigs, but they can be used for older pigs up to covering their requirements for crude fibre (about 3-5% crude fibre in the final diet for most pig formulas). Oil rancidity may be a problem in diets containing rice products inclusive of the germ (like brown rice and rice bran). In conclusion, besides price and quality, no real problems should arise from the use of white rice in pig diets even if rice is used as the only cereal. Of course, cooked rice is a choice ingredient for piglet diets, but this is rather a specialty than a ‘bargain’ cereal.
Oats are high in fibre and consequently low in energy. This fact has been reflected in many studies where dietary levels of up to 30% markedly reduced post-weaning performance of piglets offered simple diets. As a consequence, oats should be limited to 10% in diets for young animals. Older animals can tolerate up to 30% oats without problems, but oats should not be offered to hyper-prolific lactating sows (which require a high feed intake that is not possible with high-fibre diets). Higher inclusion levels (up to 50%) are tolerated well when diets are thermally processed (for example, pelleted or extruded diets).
Barley is also high in fibre and has a high β-glucan content (anti-nutritional factor), which altogether make it rather unsuitable for nursery diets. Enzyme (β-glucanase) supplementation has been shown to enhance growth performance in some studies, but its effects are less evident in pigs compared with broilers. This is definitely an issue of barley quality, as varieties with a higher level of ß-glucans are more likely to respond favourably to enzyme supplementation. Hulless barley is another option but its nutritional value is still not comparable to corn because of the high β-glucan concentrations present specifically in hulless barley. Also, two-row cultivars have been shown to have a lower nutritional value than six-row varieties. A small amount of barley (about 10%) is often used in low-complexity diets to enhance their palatability, but this is commercial practice without much scientific background. All in all, barley is better held off from post-weaning diets. In later nursery diets (above 10 kg of body weight) a growth performance drop should be anticipated from feeding too much barley. Naturally, no such problems occur with older pigs assuming fibre and energy concentrations are monitored carefully. Barley is the choice cereal for producing the most white lard as preferred by certain local markets.
Triticale has been often blamed for unpalatability, ergot infestation, and high pentosan (anti-nutritional factor) concentration that made early cultivars undesirable for pigs. However, modern varieties have been used with more success in all types of pig diets. It is suggested that triticale replace no more than 25% and 50% of the cereal portion of the diets for young and older (finishing and sows) pigs, respectively. It is also suggested to use a wheat-specific enzyme when high levels of triticale are incorporated in pig diets. Being a hybrid of wheat and rye, all precautions (and problems) of these two cereals should be taken into consideration when using triticale.
Rye is extremely high in pentosans and other anti-nutritional factors. Feeding weaners with rye-based diets has produced variable results, with feed intake depression as the most common finding. Dustiness in the pig house is a common problem from feeding high-rye diets in meal form.
Supplementation with wheat-specific enzymes has been shown to somewhat increase pig performance but not to the levels supported by maize- or wheat-based diets. Ergot infestation is a major concern in rye and great care should be taken for such batches not to reach diets of young pigs and lactating sows. In general, it is best to restrict rye inclusion to 10% in diets for young pigs and 20% in diets for finishing pigs and gestating sows.


By Dr Ioannis Mavromichalis

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