|Hall, Mary Beth|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2008
Publication Date: 11/26/2008
Citation: Hall, M., Mertens, D.R. 2008. Effect of sample processing procedures on measurement of starch in corn silage and corn grain. Journal of Dairy Science. 91:4830-4833. Interpretive Summary: How a feedstuff is processed before analysis can sometimes affect the results of nutrient analyses on a feed. Because these analyses are used to balance diets to meet the nutrient requirements of animals, errors or variation in the analyses can lead to overfeeding or underfeeding of needed nutrients. That can result in reduced production, or the animal may become ill, or increased amounts of nutrients may be excreted into the environment. We evaluated effects of the temperature at which corn silage samples were dried (55°C or 100°C) and method of grinding corn silage and grain samples (through a 1-mm screen of abrasion or cutting mills) on starch analysis of corn silage and grain. Drying corn silage at the hotter temperature tended to decrease starch values. Grinding through an abrasion mill gave higher starch values for dry rolled corn grain than grinding with a cutting mill, but high-moisture corn and corn silage were largely unaffected by mill type. Results from corn silage ground through the cutting mill tended to vary slightly more than for samples ground with an abrasion mill. To reduce variability and to achieve greater starch values with corn silage and corn grain, we recommend drying samples at cooler temperatures (55°C) in forced-air ovens and grinding through the 1-mm screen of an abrasion mill or its equivalent.
Technical Abstract: Methods for processing feedstuffs before analysis can affect analytical results. The effects of drying temperature and grinding method on starch analysis of corn silage and of grinding method on corn grain were evaluated. Corn silage samples dried at 55°C or 105°C and grain samples dried at 55°C were ground to pass the 1-mm screen of an abrasion mill or cutting mill and analyzed for free glucose and starch corrected for free glucose. Starch analyses were performed in triplicate, and variability of the values evaluated. Drying at 105°C decreased free glucose, did not affect the variation in starch values, and tended to decrease starch detected in corn silage. Reduced free glucose and starch values in silages dried at 105°C may have been caused by the destruction of glucose and production of Maillard products through nonenzymatic browning. Maillard products with reducing activity could potentially interfere with the glucose oxidase - peroxidase glucose detection method used. Measured starch values were greater for corn grain ground with an abrasion mill than with a cutting mill, with the difference greater for dry rolled than for high-moisture corn. Compared to the cutting mill, grinding samples through the abrasion mill gave lower standard deviation values for measured starch content of silage. The reduced variability related to grinding was likely due to the finer particle size produced by the abrasion mill. For starch analysis of corn silage and corn grain, drying at cooler temperatures (55°C) in forced-air ovens and grinding through the 1-mm screen of an abrasion mill or its equivalent is recommended.