supplements are available and frequently used in formulating rations. A list of commonly used supplements is shown in Table 1 . MAJOR MINERALS AND VITAMINS
Considerable research has been done to establish the mineral needs of high producers and to define the role of minerals in nutritional biochemistry. Table 2 shows the current levels of the major or macro minerals recommended for dairy cattle
rations. TRACE MINERALS AND VITAMINS
The addition of trace minerals and certain vitamins to dairy cattle
rations is usually considered to be good nutritional insurance. However, the question arises: which trace minerals to add and how much of each. The trace minerals deserving some consideration as possible additions to dairy rations are shown in Table 3 . Trace minerals are needed by the dairy animal in very small quantities (parts per million). For this reason, salt is commonly used as a carrier for all the trace minerals.
Trace minerals should not be added to dairy rations indiscriminately. Many rations will contain adequate levels with or without their addition. If a trace mineral problem is suspected, examine the situation carefully and make appropriate adjustments in the mineral mixture. Too much of a particular mineral could further antagonize the situation.
Vitamins deserving consideration under Florida conditions are vitamins A, D and E. A 1400 lb cow consuming 40 lbs of dry matter daily needs about 65,000 USP units of vitamin
A, 18,000 units of Vitamin D and 280 units of vitamin E. Dry cows should receive about 50 to 100,000 units or more of vitamin A per day when green forage is not available and 20,000 units or more per cow per day if green forage is available.
Certain stress factors, such as hot climate, nitrate in feeds, disease, and lactation may increase the vitamin A requirements of the animal. In order to avoid a vitamin A deficiency in reproduction, the dairy ration should provide from 40,000 to 80,000 USP units of vitamin A. Some dairymen feed little vitamin A during the green forage feeding period and about 100,000 to 150,000 units per cow during hot weather. TABLESTable 1. Mineral supplements and their mineral composition.
To enlarge the image click hereTable 2. Major mineral and vitamin content recommended in ration for high producers (dry matter basis).
To enlarge the image click hereTable 3. Suggested trace mineral content of rations (DM) for lactating dairy cattle (NRC-1988).
This document is DS41, one of a series of the Animal Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date August 1992. Reviewed June 2003. Visit the EDIS Web Site at http://edis.ifas.ufl.edu.2.
Professor, Dairy Science Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville.