One of the earliest indications that not all animals are truly equal comes when the animals discover that the pigs are keeping the cow milk for themselves instead of sharing it out. They are annoyed with this seeming betrayal of Old Major's total equality philosophy, but are tempered by Squealer and his gift for spinning the truth:
"Comrades!" he cried. "You do not imagine, I hope, that we pigs are doing this in a spirit of selfishness and privilege? ...We pigs are brainworkers. The whole management and organisation of this farm depend on us. Day and night we are watching over your welfare. It is for YOUR sake that we drink that milk and eat those apples. Do you know what would happen if we pigs failed in our duty? Jones would come back!"
(Orwell, Animal Farm, george-orwell.org)
Squealer uses the tactic of uniting the animals against a common enemy to excuse the breach of justice, and the other animals cannot reason well enough to fully comprehend the situation. By pretending that the unequal distribution of food -- food that should be considered common property by the laws of Animalism -- is actually a selfless act of compassion, Squealer appears to be sharing in their hard work, even though he and the other pigs do far less work. His appeal is not to reason, but to emotion; share the milk equaly and the animals will bring their oppressor back! This conveniently hides the fact that the pigs are on their way to replacing and surpassing Jones in the role of supreme ruler.
Napoleon is always right
It was when the pigs became the leaders of the farm. This is an early indication of the animals not being treated equally as "the pigs did not actually work, but directed and supervised the others. With their superior knowledge it was natural that they should assume leadership" suggests that the pigs were starting to form a hierarchy among the animals and themselves, with them at the top. Furthermore, it suggests that the pigs were being authoritive when they directed and supervised the others instead of working with them.
Not only that, the incident where the apples and milk were from then on reserved for the pigs also indicates inequality among all the animals. "Our sole object in taking these things is to preserve our health. Milk and apples contain substances absolutely necessary to the well-being of a pig. We pigs are brain-workers." This suggests that the pigs had taken advantage of their position as leaders to manipulate the truth into lying to the animals. This indicates even further inequality between them and the animals and suggests that this may also occur in the future.
the early indications orwell give to show is the scene When the pigs take the milk and apples.