Lanolin is the difference.
Sheep fur has lanolin which acts as both a lubricant and a topical calming agent. When the Montana cops have their way with the sheep lanolin from the fur acts as a lubricant to make the experience more pleasant for cop and sheep but also rubs off on the Montana cops and helps keeps them calm for hours or even days.
Cows do not have this lanolin so when the Wyoming cops and cows get together there is no such lubrication nor calming effect. In fact, the lack of lube makes the experience unpleasant for cow and cop which tends to aggravate both, and this is exacerbated by the lack of any calming agent.
If you could get more Wyoming cops to appreciate the benefits of boinking sheep instead of cattle, they would be more like Montana cops. Of course the old anti-sheep cowboy traditions run deep in Wyoming so that might be an uphill battle.
