The cow will be slaughtered and only part of the body will be consumed (gut, head, for example, make for a huge part and are not usually eaten), some of the eatable parts will be wasted in the food chain.
If you count for everything, the amount of land and resources used to produce a gallon of cow's milk is always going to be much higher than anything done with a crop directly, because you cut out the middleman, the animal.
For the specific case of almonds, why not use soy milk instead for a better comparison. I'm sure you will agree that you can produce a lot more soy milk by using the soy directly then by feeding to a cow, impregnate it, shooting the calf on birth if its male, etc. the whole process.
Not to mention the copious amount of cow excrement produced and the impact on global warming due to methane emissions of the cows intestines.
You can make plant milk with soy too, its a very versatile crop. With it, you can feed the same amount of people with a fraction of the land, water, and pollution.
Some barley is purposefully grown for feed rather than aiming for the higher price that malting or milling will get. Yields on such variants can be as much as 3 times that of a nice malting or milling variant.
Given that a chicken can convert 1.5 grams of barley protein into 1 gram of meat protein, you can see how it be more environmentally efficient to "eat" barley by running it through a chicken first.
It's a bit insane if we think about it. I doubt that conversion from barley to chicken is so efficient. There is more nutrition in barley than the protein, there are carbs as well and fiber and micro nutrients that would be good for humans, besides only the protein.
A better comparison would be in calories, considering the waste of slaughtering the chicken and all the parts with don't eat, plus all the waste produced by the chicken and the water used.
And if you want to use calories instead of grams of protein, be my guest. It'll just help my argument. Chickens eat unhulled barley; the hull is almost half the weight of the kernel. Humans eat hulled barley and still a good chunk of its calories are indigestible fiber. That may help your digestive system but you're not extracting any energy from it.