How did the large rod-shaped bacteria come about???

1. Environmental bacteria, including pathogenic E. coli and Shigella dysenteriae.

2. The presence of a sufficient number of pathogenic E. coli reaches a critical level.

3. The chicken's inherent resistance is capable of fending off attacks from pathogenic Escherichia coli. Under the current level of farm management, these two conditions are easily met.

Therefore, various stressors (such as excessive day-night temperature differences, deficiencies in certain nutritional substances in feed, severe excess of harmful gases in the air, humidity being too high or too low, and disease conditions, etc.)

Resistance to poultry vaccines can lead to decreased efficacy, allowing pathogenic bacteria to express their pathogenicity, causing infections!