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Dissecting corn

The soaring price of grains in 2008, most of all corn, hit poultry producers hard. The sector is desperately looking for alternatives or ways to deal with the problem. However, the industry may be neglecting the very eye of the hurricane: corn itself. Researcher Dr Gustavo J. M. M. de Lima and co-authors* recently presented a paper where they examined the issue. They believe that although corn is the most important feed component, we are not paying it due attention. Time has come for a change.

By Dr Rogério G. T. da Cunha, Sao Paulo, Brazil

Everyone knows that corn is the most important feed component for livestock producers. What is less known, though, is that the grain we call corn is currently almost an abstractentity. According to Dr Gustavo J. M. M.de Lima, a researcher at Embrapa/CNPSA, Brazilian Agricultural Research Corporation-Swine & Poultry Research Centre, there is such a huge variation in its nutritional composition that the extremes barely resemble each other. Surprisingly enough, he states that we are neglecting the issue, much to the detriment of the sector. The problemacquires more relevance nowadays, giventhe high corn prices (and the prospects to remain high), the decreasing profit margins, and the impact of feed prices on production costs. Producers should be aware of various aspects of corncomposition and pay the required attention.

Sources of variation
Almost every aspect one can think of exerts some influence on the variation of the nutritional composition of maize. Starting from the most specific to the more generic ones, Dr Lima recalls the influence of genetics, soil fertilisation and quality, environmental conditions, and the attack of insects and plagues. From the several studies reviewed and conducted by him and his team, they found extremes of oil percentage of 1.77% and 7.02% of the dry matter. In terms of gross protein, the values varied from 5.5% to 13.66% (dry matter). Gross energy fluctuated from 3,045 to 3,407 Kcal/kg (natural basis). The variation extends to the figures for carbohydrates,fibres, minerals, amino-acid composition,and moisture content.
  So, every single component varies quite substantially. In normal situations, however, the range of values was a bit more restricted than those extremes, but it was still large nonetheless. “To make matters worse, variation does not occur only between lots. There are also substantial differences within lots. Here other factors come into play, such as location in the crop field, handling and storage conditions, and even position in the cob. Not to mention that there may be mixture of lots,” says Dr Lima.
  He reminds that corn is the only feed ingredient that is not processed. Thus, all the variation goes straight to the poultry farm. “Despite that, when technicians are formulating the diets,they do not make adjustments accordingto the differences in the nutritional composition matrix of different lots,” he says. As a consequence, many prefer to “err” on the side of caution, he adds. This means that they are conservative and formulate the feeds based on minimum values. The consequence is that producers may not be making the most of the nutrients, and can thus be wasting money.

Advice and tips
Poultry producers can not do much to control or influence the quality of the grain, unless they grow it themselves. However, what they can and should do is to constantly check the quality of maize, handle it properly, and know how to deal with the variation. For all these issues, Dr Lima has a series of useful hints.
  Although some may find this strange,he is emphatic in stating that gross protein content is not important.“Maize is an energy source. The sourceof amino-acids is soy bran. Besides, we have availability of commercial amino-acids to correct protein level and composition. Excess of protein increases nitrogen in waste matter, making the faeces more fluid, and so on,” explains Dr Lima. Thus, he advises focusing on oil content, given the high energy density of oil. For one to have an idea, in his calculations he uses a figure of 50 Kcal of metabolisable energy/kg for every 1% of variation in oil content.
  He also directs attention to another important point: “Proximal composition analysis, per se , is not good enough to know the nutritional quality of the corn lot. There is variation in the digestibility of the different fractions, which is not captured by the analysisand which interferes in the performanceof the animals.” Thus, the advice here is to focus on the digestibility of corn components, and then use these values in the formulations whenever possible.


Insects, fungi and rotting
The hints followed on some possible quality checks. Although producers can not directly interfere with the production quality, Dr Lima mentions some aspects that do interfere with the quality and which producers should therefore pay attention to. An example here would be attack by maize weevils. One may think that they just eat a little bit, but that this is compensated because feeds are supplied to the animals on a weight basis. According to him, this would be a wrong assumption. “Weevils have their preferences for different parts of the grain, thus changing the profile of the composition of maize. In initial infestation stages, there is reduction of the non-nitrogenous extract. In more severe infestations, the oil and gross protein levels are also reduced,” Dr Lima states. “Insect attacks also decrease density and thus calories. For every extra densityunit, there are a further 18.12 calories.”
  When the topic goes to the rotten grains, another surprise: Dr Lima does not condemn them blindly. “I’veseen excellent lots of rotten grains, with high oil and protein content. Thus, they should not be discarded without furtherattention. We justhave to be careful with the mycotoxins,”he says.
  Dr Lima believes mycotoxins are the second largest problem in relation to maize, the first being its reduced supply. However, he warns that there is a lot of commercial information, but very little qualified scientific data. “This becomes even more relevant if we consider that sequestering agents answer for 1% of the cost. Inany case, producers need to be attentiveto them."

Fragile: handle with care
In summarising his recommendations on handling corn at the farm, Dr Lima speaks of separation, classification, sieving and cleaning. “Separating and classifying the lots allow us to deal with differences adequately. As for sieving and cleaning, the largest concentration of aflatoxins is on the powdery fraction, which should be ruthlessly discarded. Broken grains also hold large amountsof these substances, and should be givenonly to those animals, or age-classes,that have less trouble with mycotoxins,”Dr Lima explains.
  If poultry farmers could have more impact on corn production issues, there are some practices that could reduce mycotoxins in maize. “It has been saidthat the no-tillage cropping system is thegreat culprit, but that is not completely true. If we rotatecultures, the problem is greatly reduced. Another factor that increases mycotoxinsis that production cycle times are becoming shorter and shorter,” says Dr Lima.

Impact on the pocket
If, at this point, one was still doubtful about taking composition variation into consideration, Lima gives a definite reason: costs. His team calculated the impact of the variation on feed costs if one formulates the feed properly, that is, according to the composition. “By far, the parameter with the largest impact on final cost was oil percentage. It answered for more than 80% of thevariation. In other words, more oil meantlower final prices. Only for starterfeeds was the gross protein content also important. Here, 75% of its value was explained by the amino-acids leucine,lysine, valine, tryptophane and methionine,”says Dr Lima. Using 2005 prices, he statesthat one could reach 3-4% saving in the feed costs. Today, this is a reduction not to be despised.
  Following his reasoning, he proves to be a fan of the high-oil corn varieties.“Unfortunately, I believe there won't bemuch investment in genetics and in theproduction of high-oil varieties. In the US,for example, the harvested area of such varieties has decreased in recent years.”
  Another negative aspect of the cornworld, according to him, is that producersare focusing only on agronomic indexes, but do not care much about quality. The bad news here is that one usually comes at the expense of the other. “For example, maize landrace varieties commonly have better quality, given their lower productivity. Overall, usmeat producers do not demand quality.” Food for thought.

* Dr Adsos A. Passos, from Tortuga, and Dr Eduardo S. Viola, from Bunge Alimentos S.A.


World Poultry vol 25 nr 1, 2009

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