The Effect of Experimental Turkey Embryo Infection with Mycoplasma meleagridis on Weight, Weight Gain, Feed Consumption, and Conversion

SUMMARY Turkey poults were obtained from an earlier trial where hatchability performance of a group of embryos experimentally infected with Mycoplasma meleagridis [MM(+)] was compared with that of a group of uninfected cohorts [MM(-)]. In the present trial, post-hatch production parameters compared were weight, weight gain, feed consumption, feed conversion, culling, and mortality. Both toms and hens were monitored for 16 weeks, and a group of randomly selected toms was monitored for 22 weeks. Final liveweights and dressweights of hens were compared at 17 weeks, and those of the toms were compared at 23 weeks. Hens showed no significant (P < 0.05) differences in the measured parameters during the 16-week period, nor did the initial population of toms, except in weight gain during the final period (weeks 12-16) and in final weight at week 16, which were significantly (P < 0.05) greater in the MM(+) toms than in their MM(-) cohorts. Dressweights at slaughter of MM(+) hens were significantly greater than those of MM(-) hens, but liveweights of hens at slaughter and both liveweights and dressweights of toms at slaughter did not differ significantly. This inability of MM(-) turkeys to demonstrate a comparative advantage over MM(+) birds agrees with an earlier trial (4), in which MM(+) poults had weights superior to those of MM(-) cohorts during the first 3 to 4 weeks of life (4). These data indicate that the theory of superior performance in association with MM(-) birds must be reevaluated before the benefits derived from an M. meleagridis eradication program can be measured.