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DDT Residues in Beef Cows Fed Apple Pomace¹

U. S. Department of Agriculture, Beltsville, Md. and Virginia Polytechnic Institute, Blacksburg, Va.

Abstract

Two experiments were conducted to determine if apple pomace silage, containing DDT residues, could be fed to wintering pregnant beef cows without causing the accumulation of tissue residues above the legal tolerance of 7.0 ppm in the cows or their calves. Apple pomace silage, containing 1.2 ppm DDT residues on an as-fed basis, was fed to pregnant cows every other day and hay was fed on alternate days for 18 weeks. The pomace silage caused a residue accumulation of 13.7 ppm (P<.01) in the perianal fat of the cows. This level decreased to 4.2 ppm at 16 wk. postpartum. Residues in their whole milk were 0.18 ppm at 1 day postpartum and decreased (P<.05) to 0.07 ppm 16 wk. later and the elimination of these residues via the milk was reflected in the blood residue level of the calves. The DDT residue content in the perianal fat of the calves at 16 wk. of age was 7.2 ppm (P<.05) and decreased below 3.0 ppm at 26 weeks.

Apple pomace silage containing 0.6 ppm DDT residues caused an accumulation of 2.2 ppm residues in the perianal fat which decreased to 0.9 ppm at 16 wk. postpartum. Diluting this silage with an equal amount of corn silage reduced the maximum residue accumulation to 1.9 ppm. Changes in the residue content of whole milk and calves' blood were less, when the apple pomace containing the lower level of residue was fed and the perianal fat residues of the calves at 16 wk. of age were not different from the controls. These data would support the incorporation of apple pomace silage into the winter feeding programs of beef cow herds if (1) the DDT residue content of the silage is known and restricted accordingly and (2) if residues from pesticides other than DDT are not a problem.

¹ This study was conducted in cooperation with the Southern Regional S–10, The Improvement of Beef Cattle Through Breeding Methods.

² Research Animal Husbandman and Biological Laboratory Technician, A.R.S., Animal Husbandry Research Division, Beltsville, Maryland.

³ Associate Professor of Animal Science, VPI Division of Research, College of Agriculture and Life Sciences, Front Royal, Virginia.

⁴ Research Animal Husbandman, A.R.S., Animal Husbandry Research Division, Front Royal, Virginia.

⁵ The authors gratefully acknowledge assistance of Drs. M. L. Crandall and G. Samuelson in performing surgical biopsies for fat samples; Harold Heatwole and Peter Reid in the analytical laboratory; and National Fruit Products Company, Winchester, Virginia, for providing the apple pomace used in this study.