Nutritional evaluation of low grade corn for ruminants



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Texas Tech University


Five samples of corn grain containing various percentages of TDK were obtained from a grain exchange in Amarillo, Texas along with a No. 1 grade corn from the Texas Tech Feed Mill and a sample grade (SG) corn from a grain elevator in Castro County. The primary form of kernel damage in all seven corn samples was described as "germ damage by heat" (germ discoloration). Grades and TDK contents represented by the corn samples were: No. 1 grade (2.0% TDK), No. 2 grade (4.8% TDK), No. 5 grade (11.8% TDK), SG (18.6% TDK, SG (20.1% TDK), SG (41.6% TDK) and SG (55.0% TDK). Neither ash, crude protein, pepsin digestible protein, acid detergent fiber, total starch nor readily available starch content of the corn samples exhibited a consistent increase or decrease as a reflection of TDK. Ether extract values (1.5 to 2.21%) were lower than the value for ground corn commonly reported. The ether extract content increased in a linear manner (P<.05) as TDK increased. Neither in vitro dry matter nor organic matter digestibility were affected by TDK in such a manner that would suggest that this grading factor (when represented by the form of kernel damage present in this study) can be used to predict these properties of corn samples. Differences in variety, agronomic background and storage history may have masked the effect of kernel damage in this experiment.