Why Corn Quality Makes or Breaks Feed

Feed quality variability is largely due to variations in raw material quality, both physical and chemical. This is normal because feed ingredients are agricultural products, some of which are agricultural waste, and some are derived from food industry waste. Variability is absolutely natural and cannot be eliminated, but it can be controlled and monitored to minimize its impact. It is important to consider the variability of corn, since most poultry feed here is corn-soybean meal-based. Corn accounts for 40-60% of poultry feed formulations. With this proportion, corn contributes 65% of the energy content (AME) and 20% of the protein content in broiler feed.

The Essence of Corn Quality in Feed

Farmers often assess feed quality by its physical color. Yellowish feed is considered of good quality and physical consistency due to its high corn content. A sufficient corn content will produce a golden yellow color due to its carotenoid content, especially lutein and zeaxanthin.  Corn is naturally preferred by poultry, increasing feed intake and supporting production performance. Also a primary energy source in poultry feed due to its high digestibility and good palatability. Corn relies entirely on local production because the government prohibits corn imports.

Corn’s nutritional components make it ideal as a primary raw material for poultry feed. Its relatively high starch content (65-72%) is easily digested, providing high metabolic energy (3300-3400 kcal/kg). The 3-5% fat content also contributes to corn’s high ME, and it is rich in unsaturated fatty acids, such as linoleic acid, which is essential for egg size and egg production. The crude fiber content is relatively low (<2%), which is advantageous because poultry have limited ability to digest large amounts of crude fiber, as corn in feed can reach >50%.

Corn protein content ranges from 7-9% with high digestibility (>85%), with zein being the main component (40-50%). Zein is low in essential amino acids, particularly lysine and tryptophan, but high in non-essential amino acids such as proline and glutamine. Corn protein is of low quality to meet essential amino acid requirements, but its high digestibility makes it a significant energy source. Other nutritional benefits of corn include its high content of several vitamins, such as vitamins A, E, and B complex. It is also rich in carotenoids, which support yellow pigmentation and also function as antioxidants.

Although corn is sourced locally, supply and demand factors cause price fluctuations. The presence of corn in the feed industry has become highly strategic, as price fluctuations directly impact feed prices. The main harvest season (contributing 50-60%) typically occurs between January and March, especially in the corn-growing regions of East Java, South Sulawesi, and Lampung. This is followed by a second harvest (30-35%) in April-June, primarily from the corn-growing regions of Central Java, West Nusa Tenggara, and Gorontalo. Smaller harvests (10-15%) occur between September and November in the corn-growing regions of West Java and Southeast Sulawesi. Despite its high price, corn’s nutritional advantages make it difficult to completely substitute alternative raw materials.

Causes of Corn Nutritional Variability

As an agricultural product with a long processing chain, from planting to harvesting, drying, and storage, corn is inherently variable. Many factors contribute to this variability, including genetics, the environment, cultivation, and post-harvest handling. The combination of these factors leads to differences in corn quality between regions of origin. The physical characteristics of imported corn (from the US and Brazil) differ significantly from those of local corn. Local corn also comes in wide varieties, such as hybrid corn, composite corn, and others.

The nutritional value of corn in poultry feed is largely determined by its chemical composition and physical characteristics. Environmental factors that influence this include rainfall, soil type, nutrient availability, altitude, sunlight intensity, and pest and disease burden.

Environmental Factors

Corn requires sufficient rainfall during the vegetative and flowering phases to support plant growth and seed formation. If water is scarce during these phases, the resulting seeds tend to be smaller, wrinkled, and have lower protein and starch content.

Sunlight intensity affects the photosynthesis process. During growth, corn requires sufficient light intensity to accumulate starch in the seeds. Lack of light reduces starch content and reduces yields.

Corn requires an ideal temperature of around 21-30°C for optimal growth. High temperatures cause heat stress and reduce seed quality by accelerating grain filling. Conversely, low temperatures slow the growth process and reduce yields.

Soil type, whether neutral, acidic, or alkaline, and soil water content will affect plant growth. These numerous factors clearly indicate that the quality and quantity of corn produced in one region can vary from another.

Genetic Factors

Corn varieties have specific genetic characteristics. These varieties develop through natural selection or deliberate plant breeding to produce desired traits. These differences lead to morphological differences, as well as nutritional content and adaptability to environmental factors. Morphological differences lead to different kernel shapes and sizes, including kernel color, resulting in yellow, white, and even purple corn. Kernel texture is determined by the starch content and distribution within the kernel.

Kernel texture is a genetic morphological trait, and based on this, corn is divided into two groups: hard corn and soft corn. This characteristic affects its durability during subsequent processing and its nutritional quality. Hard corn has a higher protein content and lower starch content. During processing, these hard kernels are more difficult to grind, reducing grinding efficiency. Conversely, soft corn is easier to process but is more susceptible to pests, such as mold, during storage. Kernel hardness and kernel density (specific gravity) are not commonly measured in the laboratory but can vary significantly.

Physical Analysis of Corn Quality

In corn acceptance practices, examining physical characteristics is essential because they are closely correlated with chemical composition. Some of these physical parameters include broken corn (BC), foreign material contamination (FM), moldy kernels (moldy), water content, specific gravity, and mycotoxins (especially aflatoxin). Each feed mill may have different threshold values ​​for these parameters. Corn quality can be categorized into grades 1, 2, and so on based on physical parameters.

BC refers to corn kernels broken or damaged during harvesting, transportation, and storage. FM refers to foreign materials other than corn, such as soil, sand, dust, husks, stones, and others. The percentage of both in corn must be limited, as they will reduce corn quality. BC has a lower nutritional content due to fat oxidation, and physical damage reduces protein content. BC also facilitates fungal growth and pest infestations (aphids) by destroying the outer protective layer. FM does not contribute to nutritional value.

Moldy kernels are expressed as a percentage, i.e., the weight of corn kernels affected by mold divided by 100 grams of sample. This calculation method is highly subjective among analysts, leading in significant bias. Fungal infections consume essential nutrients such as starch, protein, and fat, thus reducing grain quality. If the infection is caused by fungi from the Aspergillus and Fusarium species, they can produce mycotoxins (aflatoxins and fumonisins) that are harmful to the health of poultry consuming the corn.

Corn moisture content must be measured before storage, during drying, and after drying. Corn dried traditionally (sun-dried) often has varying moisture content, especially since a single truckload may come from multiple locations. The ideal moisture content for corn is 12-14%. A moisture content exceeding 16% is not recommended for prolonged storage with poor ventilation, as it increases the risk of mold growth, microbial activity, and grain damage. Excessive dryness (<10%) makes the grain more brittle and increases the amount of fine material (dust).

Maize Vitreousness

This parameter refers to the hardness of the corn kernel’s endosperm, namely the relative proportion (ratio) of hard endosperm to soft endosperm. Corn with a higher proportion of hard endosperm than soft endosperm is classified as high vitreousness, and vice versa. This endosperm hardness parameter will vary depending on the corn’s origin, hybrid type, planting pattern, post-harvest handling, and other factors. Correa et al. (2002) compared five Brazilian and 14 US hybrid corn varieties and found that the hardness level of Brazilian hybrid corn was 73.1% (64.2-80.0%), while the hardness level of US hybrid corn was 48.2% (34.9-62.3%).

Generally, US hybrid corn kernels are of the dent cultivar, and Brazilian corn kernels are of the flint cultivar. Hard endosperm is dense and rich in zein protein, while soft endosperm is more brittle and rich in starch. Vitreousness is closely correlated with corn’s specific gravity. The higher the proportion of hard kernels, the higher the zein and amylose starch content. This type of corn has lower nutritional quality due to its more difficult-to-digest starch structure, resulting in slower energy production. It also has a 20-30% higher phytate content (Kaczmarek et al., 2013).

Main Nutrient Variability

Main nutrients in corn include starch, protein, and fiber. Amino acids (lysine and methionine) and anti-nutrients such as phytate and non-starch polysaccharides (NSP) are variables influenced by many factors. These nutritional parameters have a strong heritability and can therefore be controlled through genetic selection.

NSP is a component of crude fiber that cannot be digested by the poultry digestive system. The main component of NSP is arabinoxylan, a major constituent of plant cell walls. The total NSP content in corn ranges from 8-12%, with arabinoxylan accounting for 5-8%. NSP is classified as an anti-nutrient because it inhibits the mixing of enzymes with feed compounds, thereby reducing the effectiveness of digestion and nutrient absorption.

NSP content varies by region of origin. Corn from subtropical regions has a low NSP content, while tropical corn has a higher NSP content. Hybrid corn has lower NSP levels than local varieties because it has been selected to increase protein and starch content. In their study comparing 16 corn hybrids, Melo-Duran et al. (2021) found variations in total NSP content ranging from 5.56 to 1.56%. 8.13% and soluble NSP 0.1-0.85%. NSP content is also influenced by the position of the corn kernel on the cob. Kernels at the base of the cob tend to have lower NSP content but higher protein and starch content.

Cultivation practices that add nitrogen fertilizer also affect NSP levels. Adding N fertilizer to the soil will increase protein and starch levels, resulting in low NSP. Corn crude protein content varies approximately 5%, ranging from 8 to 13%, while starch content varies around 2%. Starch consists of amylose, which is slowly digested and has linear glucose chains, and amylopectin (which provides energy more quickly with a branched structure). The amylose/amylopectin ratio plays a larger role in energy and nutrient supply. Protein and starch influence the hardness of the endosperm of the corn kernel and protein solubility.

Drying Process Factors

In animal feed, corn is classified as wet or dry. While on the plant, corn’s moisture content begins to dry naturally at 30-40°C. 35°C. Wet corn is usually harvested directly from the field when the kernels are physiologically mature, and the moisture content is 22-24% or lower. It is then shelled and sent to feedmills. Only feedmills, large farmers, or collectors with drying facilities accept wet corn for drying.

Some farmers extend their harvest period (1-2 weeks) when the weather is favorable to further reduce the moisture content. Natural drying with corn cobs still on the plant can be done in two ways. The first method involves trimming the stalks above the cobs and the leaves below the cobs to speed up drying. The second method is similar to the first, but the corn husks are opened so they are exposed to direct sunlight.

Traditional drying in the sun is safer but takes longer (7-8 days) and requires additional work. After the corn is shelled, it is dried on a drying floor in the sun until the moisture content reaches <15%. Corn sent directly to poultry farmers can have a moisture content of 17% with a limited shelf life.

The high-temperature drying process negatively impacts the physical quality of corn kernels. Rapid drying at high temperatures can cause stress cracking on the kernel surface, making kernels prone to breakage during storage or milling. Excessive moisture loss causes the kernels to wrinkle, resulting in uneven size. The shiny color of the corn kernels, which was originally bright yellow, can become dull, giving the impression of old or low-quality corn. The color can also darken due to the Maillard reaction between proteins and sugars.

Drying temperature interacts with corn’s moisture content at harvest. Higher moisture content also negatively impacts starch content and protein denaturation, which, in turn, reduces digestibility. Starch damage occurs as retrograded starch, in which heating causes gelatinization. Upon cooling, the amylose and amylopectin molecules revert to a semi-crystalline form, which is more difficult to digest. Research using dried corn at 100-105°C did not reduce energy digestibility. In another study, drying corn at 140°C reduced its AME energy by 100 kcal/kg, due to reduced starch and protein digestibility.

High drying temperatures (120°C) increased the amylose content in starch by 25.5% compared to 35°C (21.5%). In hard corn (hard endosperm), drying at 120°C increased the amylose content more (21.3 to 26.7%) compared to corn with average hardness (21.7 to 24.2%). In another experiment, drying at 80°C or 120°C decreased corn kernel hardness (vitreousness), protein solubility index, increased starch damage, total and insoluble NSP, and total and insoluble arabinoxylan, compared to drying at 35°C. In contrast, hard corn (63.61% vitreousness) dried at high temperatures had no effect on vitreousness and NSP levels.

Impact of Corn Quality on Feed Formulation

In poultry feed and nutrition formulations, corn is classified as the primary energy source. Generally, the amount of energy, in the form of metabolizable energy (AME), is calculated from proximate analysis results: protein, fat, crude fiber, starch, and ash. This estimation method does not guarantee accurate results, as it also accounts for the presence of anti-nutritional compounds and the corn’s characteristics. Energy variations between different corn batches can range from 100 to 150 kcal/kg.

Table 1. Total content of NSP, NDF, ADF, Starch, AX and A:X in corn and its by-products

Raw material	Total NSP (g/kg)	NDF (g/kg)	ADF (g/kg)	Starch (g/kg)	AX (g/kg)	A:X
Corn	81	85	24	625	38	0,81
Corn gluten meal	49	121	70	120	20	1,22
Corn bran	370	406	105	211	221	0,56
Corn bran with soluble	171	227	51	190	95	0,58
Cooked corn DDGS	204	345	92	28	108	0,83
Corn DDGS reduced oil	250	387	143	29	143	0,79
Uncooked DDGS	220	308	79	52	113	0,77
High protein DDG	219	311	118	82	92	0,80
Corn germ meal	444	462	115	164	292	1,18
Corn gluten feed	287	275	84	111	145	0,69
AX = arabinoxylan, A:X = ratio arabinose to xylan
Sources: Amy L. Petry and John F. Patience, 2020

The nutritional quality of corn is determined not only by its nutrient content (protein, starch, and fat) but also by its anti-nutrient content (NSP and phytate). The interaction between these anti-nutrients and nutrients will affect their availability during digestion. Given the numerous factors that cause variability in nutrient content, particularly proximate and anti-nutrient components such as NSP and phytate, enzyme additions are commonly used to reduce corn nutrient variability. The addition of xylanase, amylase, phytase, and protease enzymes not only helps reduce the negative impacts of corn variability but also the drying and processing of corn during production (grinding).

Amylase improves starch digestibility by breaking it down into simpler sugars that are more readily absorbed. The use of protease enzymes aims to improve protein digestibility by helping break down proteins into more easily absorbed peptides and amino acids.

Corn, characterized by hard kernels, has a cell wall dominated by arabinoxylan, which forms a physical barrier that prevents endogenous enzymes from acting on the endosperm. This inhibits nutrient availability, requiring the addition of xylanase and beta-glucanase to break down the structure to make energy more available.

The increased feed viscosity caused by high-fiber corn can be reduced by adding xylanase and beta-glucanase enzymes. The enzyme dosage must be precise, adjusted to the feed formulation (raw material combination) and corn quality. Combining several types of enzymes can provide more optimal results if the feed contains many raw materials with high fiber/anti-nutrient content.

Implications for Poultry Performance

An experiment (3 x 2 x 2 factorial) on Cobb 500 broiler chickens raised to 42 days of age involved a combination of three types of hybrid corn (two semi-hard grain hybrids and one semi-dent/semi-soft grain hybrid), drying at 80 and 110°C, combined with the addition of an enzyme mixture (amylase, xylanase, and protease). Chickens fed a feed supplemented with an enzyme mixture showed greater weight gain from days 1 to 21 and a higher digestibility coefficient at 42 days. Chickens fed corn dried at 80°C had better feed conversion between days 1 and 42.

Table 2. Broiler performance was measured across different treatments: hybrid corn, drying temperature, and the addition or absence of an enzyme mixture.

Treatment	1-7 days			1-21 days			1-42 days
	BWG,g	FI, g	FCR	BWG, g	FI, g	FCR	BWG, g	FI, g	FCR
Hybrid
1	117.5	153.2	1.306	797.3	1087.4	1.364	2832.9	4575,4ab	1,615
2	117.7	152.2	1.295	793.4	1079.7	1.362	2806.4	4552,4b	1,623
3	117.2	151.8	1.297	801.4	1095.5	1.367	2862.6	4640,4a	1,622
Temperature
80 oC	117.6	153.0	1.305	800.9	1096.2a	1.370b	2838.5	4603,9	1,622
110 oC	117.3	151.7	1.294	793.9	1078.7b	1.359a	2829.9	4575,3	1,617
Enzyme
With enzyme	119.4a	151.2	1.267b	812.3a	1091.1	1.343b	2843.6	4591,6	1,615
Without enzyme	115.4b	153.5	1.332a	782.3b	1083.0	1.386a	2824.7	4587,9	1,625
SEM	0.460	0.842	0.009	2.653	2.968	0.004	9.749	14,541	0,003
Sources : Franciele C.N. Giacobbo, et al., 2021

The addition of amylase, xylanase, and protease enzymes has a positive effect on jejunum (digestive tract) morphology, supporting an increase in the population of beneficial microbes and, conversely, reducing the population of harmful Clostridia. This effect (enzyme addition) is thought to play a greater role in shaping digestive processes and nutrient utilization in broilers, thereby improving chicken performance, compared to the effects of corn type or drying temperature.

In another experiment, M.P. Williams et al. (2018) measured the effects of six corn hybrids, with or without xylanase enzymes, on broiler performance. The experiment lasted 41 days, with three phases: starter (days 1–18), grower (days 19–31), and finisher (days 20–41). On day 18, body weight was significantly affected by corn source, ranging from 724 to 764 g (p = 0.001), whereas the effect of xylanase was inconsistent.

Conversely, xylanase in the grower phase interacted with the corn source and reduced FCR. In the finisher phase, xylanase decreased the FCR (1.943 vs. 1.992). Different hybrid corn sources showed variations in AME energy values, with differences of 176 kcal/kg on day 18 and 194 kcal/kg on day 41. This study shows that variations in corn nutritional profiles (across different hybrids) affect nutrient utilization and chicken growth.

Solutions to Address Variability of Corn Quality

NIRS analysis, which can quickly and efficiently predict (proximate) nutrient content, is a key tool for determining the overall quality of corn batches to be used. The distribution of nutrient content values ​​obtained provides the basis for determining safe and economical nutrient values ​​for use in formulation calculations. It also provides a comprehensive overview of corn quality (chemical), enabling the addition and selection of the necessary enzymes to optimize feed quality.

For corn of poor physical quality, whether due to prolonged storage, inadequate storage conditions, or uneven drying, several measures can be taken to minimize the risk. By diluting it to reduce the percentage, avoiding feeding it to young chickens, and using it only as pelleted feed to improve digestibility. It’s also important to implement strict, thorough receiving inspections to reduce the influx of poor-quality corn that could contaminate the entire corn in the silo.

References

1. Amy L. Petry and John F. Patience. Xylanase supplementation in corn-based swine diets: a review with emphasis on potential mechanisms of action. Journal of Animal Science 98(11). September. 2020
2. Correa, C.E.S., R.D. Shaver, M.N. Pereira, J.G. Lauer, and K. Kohn. Relationship between corn vitrousness and ruminal in situ starch degradability. J. Dairy Sci. 85:3008-3012. 2002.
3. Edgar O. Oviedo-Rondon. Understanding corn variability. Proceedings of the Arkansas Nutrition Conference : Vol 2021,  Article 11. 2021.
4. Diego Melo-Duran, et al. Using in feed xylanase or stimbiotic to reduce the variability in corn nutritive value for broiler chickens. Poultry Science 103:103401. 2024
5. Jose I. Vargas, et al. Effect of corn origin on broiler performance, processing yield, and nutrient digestibility from 1 to 35 days of age. Animals, 13, 1248. 2023.
6. Melo-Duran, et al. Maize nutrient composition and the influence of xylanase addition. J. Cereal Sci. 97:1031555. 2021
7. Franciele C.N. Giacobbo, et al. Influence of enzyme supplementation in the diets of broiler chickens formulated with different corn hybrids dried at various temperature. Animal, 11, 643. https://doi.,org/10.3390/ani11030643. 2021
8. Williams, M.P, H.V. Masey O’Neill, T. York and J.T. Lee. Effects of nutrient variability in corn and xylanase inclusion on broiler performance, nutrient utilisation, and volatile fatty acid profiles. Journal of Applied Animal Nutrition. Vol 6. 2018