Antibiotics in Dairy Cattle Nutrition. IV. Comparative Effects of Different Levels of Crystalline Aureomycin and a Crude Aureomycin Fermentation Product (Aurofac 2A) on the Growth and Well-Being of Young Dairy Calves

Abstract

Since crude Aureomycin fermentation residues or products probably contain, in addition to known amounts of Aureomycin and vit. B12, other substances that could conceivably influence calf growth, this experiment was initiated to compare the effects of pure crystalline Aureomycin and a crude Aureomycin fermentation product (Aurofac 2A) on the growth and well-being of dairy calves. Employing a randomized block design 32 female calves of 4 breeds were divided into 4 groups. Calves in one group received Lederle''s Aurofac 2A in amounts calculated to supply 45 mg of Aureomycin daily for each 100 lb. of calf weight, and a 2d, group received 45 mg of pure Aureomycin HC1. A 3d group received 90 mg of pure Aureomycin HC1 and a 4th group of calves received no Aureomycin and served as a control. From birth to 25 weeks of age the growth rates of the 3 groups of calves receiving Aureomycin were significantly greater than the control calves. However, there appeared to be no difference in the growth of calves due to differences in antibiotic source. Furthermore, there appeared to be no advantage in the use of 90 mg of pure Aureomycin over 45 mg. However, from birth to 12 weeks the growth rate of the calves receiving 45 mg of Aureomycin from Aurofac was greater than the growth rate of the calves receiving 45 mg or 90 mg of pure Aureomycin. In an attempt to explain this it was postulated that there are factor(s) in the crude fermentation product which are not present in pure Aureomycin and which benefit calves until rumen synthesis provides these factors. The calves in the 3 groups receiving Aureomycin had a lower incidence of infection and made more efficient gains than the control calves. However, the differences among Aureomycin treatments were not significant.