In Chapter 9 of Animal Farm, what species of animal is increasing and which is decreasing?

Pigs are the obvious animals that are increasing thanks to Napoleon.

"In the autumn the four sows had all littered about simultaneously, producing thirty-one young pigs between them."

The species that are decreasing are horses and chickens. There were only three horses on the farm and in Chapter 9, Boxer the most loyal and steadfast horse is worn out, he hurts his lung working too hard. He is looking forward to retirement, but instead Napoleon has him sent to the Knacker's to be slaughtered. Chickens have been decreasing ever since Napoleon demanded that they surrender all their eggs to be sold so that the farm would have money for supplies.