High Oil Corn: What are the Risks?

Joe Lauer, Corn Agronomist

Poultry, swine and dairy cows require livestock feed with high calorie levels. High oil corn is an attractive possibility as a livestock feed because it has greater energy than normal corn. The calorie content of oil is approximately 2.25 times as great as that of carbohydrates (Alexander, 1988). Broiler diets regularly contain added oil. Dairy cows will more readily exploit bovine growth hormone to its fullest potential if energy is increased beyond that of regular corn rations. Swine treated with porcine growth hormone can expect similar advantages.

The first high oil corn varieties were selected in 1896 at the University of Illinois (Hopkins, 1899). Over the years genetic selection has steadily improved agronomic performance and yield of corn hybrids with higher oil contents (Dudley, 1974; 1977). Corn kernel oil concentration ranges between 1.2 and 21.3% on a weight basis (Alexander, 1988). Commercial hybrids grown in the Corn Belt typically contain 4 to 5% oil.

The relationship between oil level and grain yield has been evaluated many times. In general, hybrids with high oil content have lower grain yield. In the mid 1950's, hybrids derived from the Illinois high oil project yielded about 10% lower than the best available commercial hybrids (Glover and Mertz, 1987). In the mid 1970's, the "Alexho" synthetic hybrids yielded 2-10% below commercially available hybrids (Weber and Alexander, 1975). Recently, Miller at al. (1981) found corn yield was not depressed when intensely selected for high oil. Hundreds of hybrids have been tested over the last 20 to 30 years, but only a few have achieved commercial significance (Glover and Mertz, 1987).

Currently, much interest is being generated with new high-oil corn hybrids marketed under the "top-cross" brand. This method of producing high oil corn involves blending two types of hybrids. Between 3 and 8% of the plants are "pollinators," while the remaining 92 to 97% of the plants are adapted, high performing "male-sterile" commercial hybrids. Pollen from the pollinator transfers the high oil trait to the kernels on the male-sterile hybrid. This is commonly known as a xenia effect. Testing of the top-cross high-oil hybrids is difficult due to isolation requirements, ie. when "wild" corn pollen pollinates the male-sterile hybrid the high oil trait is not expressed in the kernel. No university tests have been published on agronomic performance of these new top-cross high oil corn hybrids.

Dairy feeding trials show greater dry matter intake of high oil corn silage, but lower digestibility when compared to silage of normal dent corn (R.D. Shaver, personal communication). Milk yield and composition and component yields are not different. When feeding high oil corn grain there is a trend for higher milk production. This is related to higher intake of dry matter for diets containing high oil grain. No livestock performance trials have been conducted using top-cross blend hybrids.

Producers should consider the following when making a decision about using high oil corn in their management system:

• Grain yield decreases of 5 to 10% (some reports as high as 20%) can be expected with high oil corn hybrids (Dudley, 1974; 1977).
• Calorie yield increases may be small. For example, a hybrid with 8% oil will produce approximately 3% more calories per acre than a hybrid with 4.5% oil when both have the same yield (Glover and Mertz, 1987).
• Marketing opportunities and prices must be known before planting. There are no established markets for high oil corn, so prices will fluctuate with regular dent corn prices. It may be difficult to justify the cost of contract growing and identity preservation if a hybrid has only a moderate increase of 2 to 3% in oil content
• With "top-cross" blends, if stress should occur around pollination, then the nick, or overlap of pollen drop from the pollinator and silking of the male sterile hybrid, could influence grain yield since 92 to 97 percent of the plants are male-sterile (do not produce pollen).
• How much isolation from other corn fields is required to adequately express the high oil trait associated with the "top cross" blend?
• High oil kernels tend to be slower in the dry-down process (Glover and Mertz, 1987).
• Yield differences for high oil corn silage or grain must be weighed against any potential improvements in animal performance. Producers should try high oil corn on 5 acres or less for a few years before incorporating it into their operation on a large scale basis.

Literature Cited

Alexander, D.E. 1988. Breeding special nutritional and industrial types. In G.F. Sprague and J.W. Dudley (ed.) Corn and corn improvement. Agronomy Monograph 18. ASA, Madison, WI. pp. 869-880.

Dudley, J.W. (ed.). 1974. Seventy generations of selection for oil and protein in maize. CSSA, Madison, WI.

Dudley, J. W. 1977. Seventy-six generations of selection for oil and protein percentage in maize. pp. 459-473. In E. Pollak et al. (ed.) Proc. Int. Conf. Quant. Genet., Iowa State University, Ames, IA. 16-21 Aug. 1976. Iowa State Univ. Press, Ames, IA.

Glover, D.V., and E.T. Mertz. 1987. Corn. In R.A. Olson and K.J. Frey (ed.) Nutritional quality of cereal grains: genetic and agronomic improvement. Agronomy Monograph 28. ASA Madison, WI. pp. 183-336.

Hopkins, C.G. 1899. Improvement in the chemical composition of the corn kernel. Illinois Agric. Exp. Stn. Bull. 55.

Miller, R.L., J.W. Dudley, and D.E. Alexander. 1981. High intensity selection for percent oil in corn. Crop Sci. 21:433-437.

Weber, E.J. and D.E. Alexander. 1975. Breeding for lipid composition in corn. J. Am. Oil Chem. Soc. 52:370-373.