What is significant about how the animals arrange themeselves as they gather to hear major

The arrangement of the animals as they listen to Old Major's speech reveals that there already exists a distinct hierarchy on the farm. Old Major is a widely respected figure, and, comfortably ensconced on a bed of straw, his elevated status is reflected by his position upon a raised platform. The seating arrangements are significant for the additional reason that they foreshadow how society will eventually look when Mr. Jones has been sent packing and Animalism is established on Manor Farm. The dogs and the pigs take up positions nearest the platform. Come the revolution, they'll be in charge of things. They regard themselves as the smartest and hardest working animals on the farm; it's only right and proper that they should be in charge, irrespective of the ideology of Animalism with its formal equality.
Among the last animals to enter the barn are the gentle, docile horses. They, like the pigeons, the hens, the sheep, and the cows, are a breed apart from their future masters, the pigs and the dogs. In the sunlit uplands of the Animalist utopia they will be the workers, expected to toil for the revolution under the wise, paternal guidance of their intellectual superiors.