We had a thread on this, didn't we?
Domestic and wild animals often fare differently. War destroys commercial exploitation, which is usually the major threat to wild animals and the major source of support for domestic ones. In many regions, buffer zones between warring tribes serve ecologically as refuges, repopulating the hunted out regions. Some pros have speculated that that has been an important anthropological function of war, preventing humans from hunting game to extinction over large areas.
Anyway, the wars in Vietnam also (in addition to destroying much habitat and reducing human social controls on hunting etc) provided a refuge for many wild animals, large tracts where farming and hunting were too dangerous - they functioned like parks of a kind. New species of muntjac, many others, are being found as biologists take modern gear into wilderness regions not safe for research for fifty years or more.
The loss of draft animals in Vietnam, Laos, and Cambodia was severe - the US appears to have bomb-targeted them in some regions, to clear out civilians, and of course the mines still take their toll. There have been counts of this.
The slaughter of the bison on the Great Plains was deliberate, to starve the Reds off the land and into the reservations. They were almost extinguished - survivors in Canada repopulated south. The Woodland Bison of the east
was extinguished, for other reasons.
The greatest wartime animal loss in Iraq was probably when Saddam dried that big swamp at the mouth of the major river.
The wars in Africa have severely hurt the wild animal populations in some regions, as bushmeat hunters and crazy soldiers take to the wilds with automatic weapons and no social controls, and as minefields spread, but the spread of farming is as damaging.
After WWII, groups of Americans did a lot to repopulate the domestic stock of Europe, which had been eaten or starved itself - operations like the
Heifer Project were really important.
