Nutritional variability in corn used in pig diets can be a common culprit affecting productive performance. Therefore, it is a factor that animal nutritionists must always consider when formulating pig diets.
Corn is one of the most widely used energy cereals worldwide in animal diets, with particular interest in the Americas, southern Europe and Asian countries (Figure 1).
Figure 1. Annual corn production (× 103 tonnes) for main producing countries. Source:USDA
Since its domestication, corn has proven to be a cereal with a great capacity to adapt to different environmental conditions. This has resulted in the development of almost 300 different biotypes capable of being cultivated in different places ranging from tropical regions to temperate zones of 3600 m.a.s.l.
However, this has also given way to differences in its nutritional content.
Corn is generally characterized by its high nutrient content, thus providing up to 65% metabolizable energy and 20% protein in monogastric diets.
Corn inclusion in diet formulation can vary between 50% to 70% of the total diet.
However, its nutritional value can be affected by certain characteristics such as:
In this sense, genetic variation has been shown to be a factor of considerable variation within the nutritional composition, particularly in regards to its energy value.
NUTRITIONAL VARIABILITY IN CORN
Multiple trials have shown that variation factors such as geographical reference, growing conditions and drying techniques can contribute to establish differences in corn’s metabolizable energy values. Generating differences of up to 304 kcal/kg in birds for example(Melo et al., 2021).
Under commercial conditions, the factors that increase nutritional variation are conjugated within storage silos where grains from different batches and origins are mixed. This is true for cereals such as:
|Therefore, the implementation of this commercial practice, makes it even harder to control the nutritional variations of corn when formulating diets and rations.|
In fact, the concentration of metabolizable energy corrected for nitrogen can vary by more than 400 kcal/kg between batches of corn in poultry diets (Cowieson, 2005).
A tool that can help control nutritional variability, and therefore contribute to adjust dietary nutrients, is the use ofNIRs to predict the proximal composition of raw materials.
However, the samples that are analyzed with this method may not be significantly representative of all the different variability factors. Which will lead to unbalanced diets in regards to nutritional composition. Having a negative impact on the farm’s productive parameters.
|Other components of corn such as non-starch polysaccharides (NSPs), lectins and resistant starches can also be modified by the aforementioned factors.
In fact, the concentration of components such as arabinoxylans (part of the NSPs) can modify the digestibility of nutrients such as protein and starch, affecting the productive performance of animals (Melo et al., 2021).
Although, traditionally, corn has been considered as a non-viscous cereal, due to:
The variability in the concentration of soluble arabinoxylans (between 2.2 and 5.3 g/kg) can cause certain genetic varieties to behave like wheat and lead to intestinal viscosity problems, thus complicating health management within the fam.
A trial conducted by Melo et al., (2021) showed that the genetic background of corn influenced the growth of broiler chickens fed with 8 iso protein diets, but formulated with 8 different genetic varieties of corn.
The authors concluded that the content and nature of NSPs are two of the main factors affecting the solubility and availability of nutrients within corn. Having potential negative effects on broilers’ growth performance.
In this sense, this article has evaluated the potential differences attributed to the genetic varieties of corn for metabolizable energy (DM) and NSPs concentration levels for pig diets.
|For such purpose, 16 genetic varieties of corn grown under the same agronomic conditions were analyzed. This assessment included fertilization, and pre and post harvest processes.|
In total, a sample of 10 cobs, for each variety, were obtained to be processed and then analyzed to determine their nutritional composition via NIRs. Figure 2 shows the nutritional differences attributed to each genetic variety.
In general, the concentration of DM for pigs may differ by 344 kcal/kg, while the concentration of NSPs may vary by 27 g/kg.
Additionally, a negative correlation was observed between DM and part of the NSPs (soluble arabinoxylans), which would indicate that the availability of energy is a function of the content of certain antinutritional factors.
A transcendental objective in pig production is to achieve the maximum growth rate along with efficiency in the use of nutrients.
However, the variations that genetic variety can bring , as well as other uncontrolled factors, could be influencing the digestibility of nutrients such as:
That added to the low values of lysine and tryptophan of corn could significantly exacerbate the decrease in productive yield.
In animal feed the proportion of some nutrients is key, as in the case of lysine concentration and energy. On the other hand , lysine is the first limiting amino acid while energy influences the voluntary consumption of food.
Therefore, it is necessary to maintain an optimal ratio of lysine to energy when increasing the amino acid or energy content of the diet.
|Thus, the imprecise assessment of energy in the diet, as a result of the variation in the composition of corn, will alter the consumption of the rest of the nutrients and consequently the productive performance of the animal.|
Extensive research in pigs has shown that weight gain and feed efficiency improves as the standardized ileal digestible lysine:EM ratio increases.
Figure 2. Metabolizable energy values for pigs (A) and correlation between MS and soluble Arabinoxylans (B) analyzed from 16 different genetic varieties of corn.
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