The effects of F strain Mycoplasma gallisepticum, Mycoplasma synoviae, andthe dual infection in commercial layer hens over a 44-week laying cycle when challenged before beginning of lay. II. Egg size distribution

In each of two trials, 160 commercial pullers were separated into four trea tments with four replicates of 10 chickens in each treatment. Forty pullers were designated as controls and received no inoculation; 40 pullers receiv ed F strain Mycoplasma gallisepticum (FMG); an additional 40 pullers receiv ed Mycoplasma synoviae (MS); and the final 40 pullers were inoculated with both FMG and MS (dual). All inoculations occurred at 10 wk of age. Eggs fro m all treatments were collected daily, Monday-Thursday, and individually we ighed. No significant difference was observed among the treatments for percentages of jumbo, extra-large, medium, small, peewee, or undergrade eggs. As a per centage of eggs laid for the 4 days of each week over the 44-wk laying cycl e of each trial, the FMC hens laid significantly Fewer large size eggs (43. 2%) as compared with either controls (51.17%) or dual-infected hens (49.95% ). No significant difference was found in percentage of large eggs laid by FMG hens when compared with MS hens.