Livestock (in this case referring to cattle) usually don't eat pine trees, particularly if they have all the nutritional requirements of their diet met. In this case, it doesn't sound like a particular nutrient has been met, hence their need or want to strip bark off of trees or, if you have wood fences, chew on the wood boards. This particular mineral is Phosphorus, and is usually not found in most mineral blocks purchased at your local farm store. Most mineral blocks are "trace mineral" blocks, which means they have 95% salt and 5% micro-minerals consisting of elements like copper, iron, iodide, cobalt, molybdenum, magnesium, manganese, and sometimes selenium if they're advertised or labelled as selenium blocks. Phosphorus is a macro-mineral, along with calcium, nitrogen, potassium and sodium.
Without knowing what sort of "diet" your cattle are on, (though I assume it is grass-fed with no grain, from the sounds of what they have access to), it is hard to pin-point or let you know what exactly can be done to curb the problem of your animals consuming and killing your trees. However, what can be suggested is to add in another supplement that has phosphorus in it, such as loose mineral, or find a mineral block that has higher levels of phosphorus than the one you have always been feeding. I mentioned before how TM (trace mineral blocks) are not enough to satisfy your animals' needs, but that isn't exactly truthful because cattle actually need a lot more salt than minerals, even though some producers claim that cattle will lick and lick away at the block and not get much from it except a lot of salt. You can still opt to feed them the TM block and add some sort of supplement that is high in phosphorus (such as grain), or you can switch your mineral program and feed loose mineral with salt in it. Depending on the mix of the loose mineral and what your cattle have access to, loose mineral mixes usually come in a 2:1 or 1:1 calcium:phosphorus ratio. The first is for cattle with little access to feeds or forage high in calcium, the former for those who have lots of access to feeds high in calcium but little phosphorus. You will need to check with your local feed supplier to see what mineral supplement is right for you and your animals.
They are fleshy
it is fleshy
fleshy
it's fresh fruit
vegetables with fleshy cover
The fleshy top root develops when primary root grow rapidly it becomes thick and fleshy
fleshy roots are for storage of food and water.
Fruit like peaches and nectarines are "fleshy".
Considering we are mamals with soft fleshy lips, I would say that most mammals have soft fleshy lips.
My stomach and buttocks because they are fat (fleshy) and round (plump)
it the acene i.e fleshy thalamus
why are limb leads placed on fleshy parts of the body