Progress Report 20 May, 1954 THE VALUE OF A COMBINATION OF ANTIBIOTICS VS. SINGLE ANTIBIOTICS FOR YOUNG DAIRY CALVES 5 C. A. .Lassiter, T. W. Denton and J. W. Rust Thirty-two Jersey and Holstein calves (20 Jerseys and 12 Holsteins) 2 to 3 W days old were raised on a limited milk—starter—hay system to evaluate a combination of aureomycin and terramycin versus the single antibiotics for young dairy calves. Milk was fed at the daily rate of 8 per cent of body weight for the first 21 days of life; thereafter, the amount of milk fed was gradually reduced until the calves were completely off of milk at 49 days of age. · The calves had all they wanted to eat of an excellent quality alfalfa hay, and one of the four calf starters shown in table l was fed up to a maximum of 4 pound daily beginning at 1 week of age. The antibiotic feeding supplements were fed at a rate to furnish 75 milligrams of crystalline antibiotic per calf daily for the first 49 days. The supplements were placed in the starters thereafter. The results are given in the following tables. Table 1. Composition of Experimental Starters l 2 3 4 (1b1 (lb) (lb) ) Soybean oil meal ·L~¢— 50 50 50 50 Crimped oats ··;··- 120 120 120 120 Ground yellow corn A - - 80 80 80 80 Wheat Bran . · · A · · 50 50 50 50 Distillers solub1es(72% corn) 100 100 100 100 Steamed bonemeal ···· 5 5 5 5 Vitamin A and D feed (grams) 200 200 200 200 Aurofac ZA (grams/lb.) · I — 3 - 1. 5 TM- (grams/lb.) · · · - - - 2.5 1.25 Analysis in percent .— Dry matter eis·»·· 92.8 91.3 91.8 91.9 Crude protein -··s·Ve 21.5 20.6 21.7 21.8 Ether extract . ..... 5.0 5.0 5.0 5.0 Crude fiber. . . . . . 6.0 5.9 5. 8 6.0 Nitrogen—free extract . . . 53.1 53.0 52.1 51. 8 . Ash. . . . . . . 7.2 6.8 7.2 7.3 Kentucky Agricultural Experiment Station University of Kentucky Lexington