Effect of Spiramycin on Growth and Feed Utilization of Young Pigs

Two experiments involving 615 pigs were conducted to study the effect of varying levels (0, 12.5, 25 and 50 gm./ton) of spiramycin on rate of gain and feed conversion by young growing pigs, and also to compare the highest level with similar levels of chlortetracycline and oxytetracycline. In each of the experiments, maximum gains were obtained with the highest level of spiramycin fed. However, the statistically significant quadratic regression of gains on spiramycin levels is indicative of a plateauing of the response above levels of 25 to 50 gm./ton. Similar quadratic regressions of feed/gain on spiramycin levels were observed. Differences in response (gain and feed/gain) to the 50 gm./ton level of spiramycin and the same level of chlortetracycline in one experiment and oxytetracycline in the other were not statistically significant.