Breyer: Little Bits / CollectA (roughly 1:18 - 1:20 scale)
Generally considered to be approximately 1:20 scale, Little Bits (name changed to Paddock Pals in the 1990s) average around 4" high, though each model is different. This scale was retired by Breyer in the mid-1990s, so finding them is getting harder every year.
In 2017, Breyer acquired the rights to CollectA models in the US, selling them as "Corral Pals... Breyer by CollectA." These models are vinyl (slightly flexible and safer for kids) and come in a huge variety of breeds, colors and positions. CollectA also makes other animals, and prides itself on realism for use in educational settings!