The dog looks like a Great Pyrenees. Herding dog with herding instincts. I’ve seen them at some sheep ranches in the Texas Hill Country, and they are very protective around sheep.
...we have three on our farm...
... the oldest, "Winry", went missing one day, couldn't find her all day...
...finally she came up from the woods in our back goat pasture, barked and trotted back into the woods...
...(it was her Lassy imitation "follow me, Timmy's fallen into the well!")...
...when I followed her down, she was curled up around a fawn that must have been born in the back pasture but unable to follow mom back out...
...our GP didn't leave that little deers side for months...
...that was 6 years ago and the deer, "Holly" still hangs out with our goats in that back pasture to this day...
...we have 15 dogs on our farm, from little muts, to hounds to labs, but the GP's amaze me every day...