INGREDIENT AND PROCESSING INTERRELATIONSHIPS IN SWINE FEEDS: III. EFFECTS OF WHEAT BRAN, PELLETING AND PROTEIN SOURCE ON RESPONSES TO DIETARY ANTIBIOTICS

Abstract

This is the third in a series of reports on the growth, feed consumption and digestibility responses of growing pigs (50 to 110 pounds in weight) involved in a 2 × 2 × 2 × 2 factorial study of 0 vs. 10 per cent wheat bran, meal vs. pellets, 0 vs. 33 p.p.m. mixed antibiotics and plant versus animal-plant-origin protein supplements. The antibiotic mixture contained penicillin, streptomycin and chlortetracycline in the ratio 5:15:10.The growth and feed consumption response to antibiotics was generally favourable (P = <.05), but the greatest effects were observed on meal-type rations devoid of both animal protein and bran. In some cases antibiotics promoted more efficient conversion of feed dry matter into weight gains but usually the increased gains were due to increased feed intakes. The possibility of enhanced B-vitamin supply or utilization is discussed.Antibiotics effected an increase in energy digestibility but had relatively little effect on digestibility of protein. As with gains and feed intake responses the most marked energy digestibility effects occurred with meal rations that were bran-free and animal protein-free. Thus energy digestibility increases and feed intake increases largely accounted for the increased gains on these diets.The failure of antibiotics to effect as good responses in pelleted as in meal rations, or in the presence of bran or with animal protein, is discussed in relation to the matter of encouraging maximum feed intake and particularly with reference to ingesta behaviour and characteristics in various parts of the gastrointestinal tract.