The cockerel marching in front of Napoleon is significant because it represents the way that propaganda can be used to control people. Squealer is able to use his words to make the animals believe anything, and this allows Napoleon to maintain his power. The cockerel is a symbol of the power of propaganda and the dangers of allowing someone to control the information that you receive.
In the book, Squealer uses his gift of gab to convince the animals that Napoleon is always right, even when he is clearly wrong. For example, when Napoleon changes the rules of the farm to give himself more power, Squealer convinces the animals that this is actually for their own good. He also convinces the animals that the pigs are working harder than everyone else, even though they are actually doing less.
Squealer's propaganda is effective because he is able to play on the animals' emotions. He makes them feel guilty about not working hard enough, and he makes them believe that Napoleon is the only one who can save them. This allows Napoleon to maintain his power, even though he is not actually doing anything for the animals.
The cockerel marching in front of Napoleon is a reminder that propaganda can be a powerful tool for controlling people. It is important to be aware of the dangers of propaganda and to think critically about the information that you receive.