I suspect small amounts won't hurt cows, but unfortunately, there is
research regarding abortions/miscarriages/early delivery in cows from pine needles. Based on what it says, it seems that it is most common in harsh winters with little else for forage where they eat a fair amount & develop a 'taste for it'. [No, I am NOT jumping all over you...I've seen cows eat pine needles and cedar, too!]
Regarding chickens, there is
this study testing immunity & serum cholesterol levels, and
fermented pine needle powder on antioxidant/oxidative stress on broilers.
Additionally, there is a
study (with some positive effect) on hepatic cancer. (in humans)
So, it seems pine needles are fine for some animals, and not so much for other animals. (note the bovine study mentions 'no effect' on some other traditional livestock)