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The Effect of Low to Normal Dietary Phosphorus Levels on Zinc Metabolism and Tissue Distribution in Calves^1,2,3,

University of Georgia, Athens 30602

Abstract

Sixteen 10-wk-old, phosphorus (P)-depleted Holstein bull calves were fed for 6 wk a control diet containing .08% P or P-supplemented diets containing .14, .20 or .32% P with supplemental P from two sources (GDP and Dynafos). The diets contained .45, .56, .66 and .87% Ca. After 5 wk of the experiment, the calves were dosed orally with ⁶⁵Zn, and daily total fecal collections were initiated. At the end of the experimental period, the calves were killed and tissue samples were taken for total Zn and ⁶⁵Zn analyses. Growth, feed intake and feed efficiency improved with increasing dietary P levels. Level of dietary P and Ca had little or no effect (P>.05) on total Zn content of rib, tibia, liver, heart, kidney, muscle or blood. Likewise, ⁶⁵Zn absorption and content in most tissues were not affected (P>.05). The results do not preclude the possibility of some minor effects of P levels on Zn metabolism. However, it is apparent that when adequate Zn is fed, any effects are likely to be of little or no practical importance.

¹ Supported by State and Hatch funds allocated to the Georgia Agricultural Experiment Stations, and in part by a grant from the AMAX Chemical Corp., 402 S. Kentucky Avenue, Lakeland, FL 33801.

² The authors wish to thank the following for their generous donations: AMAX Chemical Corp., Plant City, FL 34289 (lab analyses); American Cyanamid Co., Wayne, NJ (Aureomycin-50); International Mineral and Chemical Corp., Mundelein, IL, and Southeastern Minerals, Inc., Bainbridge, GA (minerals and trace minerals); Southeastern Feed Ingredients, Inc., Gainesville, GA (blood meal); Dawes Laboratories, Chicago, IL (vitamins A and D), and Kemin Industries, Des Moines, IA (Endox). Appreciation is extended to Jim Mitchell, Lena Cashion, and Scott Johnson for technical assistance, and to Ruth Harris for editing and typing assistance.

³ Dept. of Anim. and Dairy Sci.

⁴ To whom correspondence should be addressed.

⁵ Dept. of Large Anim. Med.