Cows are natural: they belong on the land
Modern cattle are a product of centuries of selective breeding, at a scale and density with no natural precedent. And 'natural' does not settle whether something should continue.
Cattle have lived alongside people on pasture for thousands of years, and grazing animals belong on grassland in a way that fits the land rather than fighting it. Many grasslands evolved with large herbivores and depend on them, and much grazing land is too steep, dry or poor to grow crops, so cows turn it into food while keeping the landscape healthy. Removing them would break a long-standing relationship between people, animals and land that is part of how the countryside is meant to work.
Today's cattle breeds were shaped deliberately for yield and growth rate, and exist in numbers no wild population of comparable animals ever approached. Grazing land accounts for roughly a quarter of the world's ice-free land surface, which is a function of human agriculture rather than of any natural distribution.
There is a serious version of this argument: that well-managed grazing on land unsuitable for crops has ecological value, and that some grassland ecosystems co-evolved with large herbivores. That case is worth engaging with on its merits. It is not the same as the claim that cattle farming is natural and therefore acceptable, which does not follow even where the ecology is favourable.
Treating 'natural' as evidence of 'good', or 'unnatural' as evidence of 'bad'. Whether something occurs in nature tells you nothing about whether it is beneficial or right: hemlock, malaria and infant mortality are all perfectly natural.
How it applies here: Offers naturalness as the justification. The scale, density and genetics of the current cattle population are in any case human products, so the premise is doubtful before the inference is even assessed.
Moving from a description of how things are to a claim about how they ought to be, without supplying the moral premise that would connect the two. Identified by David Hume.
How it applies here: Moves from a claim about where cattle belong to a conclusion about what we should do, without the premise that would connect the description to the obligation.