We have 8 acres mixed animals on fertile temperate New Zealand land. Average 5C minimum in winter - some frosts though!, We get 1000mm of rainfall (about 40 inches) a year - dry summers, but we have access to good unlimited bore water that went fine during the worst drought in 50 years. We have a mix of goats, sheep, pigs, chickens and cattle. Grass growth slows in winter, but does not die. We are putting in forage trees and vines to help deal with the winter and mid-summer lack of grass growth. Apart from some grain for the chickens, would we get more calories per acre by planting either wheat or sugar beets or by just managing our pasture well, and cutting hay in the times of increased growth?
I can't find a calorie per acre yield for pasture (I know it would differ according to rainfall) but surely the pasture and forage crop would increase at similar rates with improved fertility.
Personally, I'm a firm believer in creating a good herbal ley pasture. Not only does it give variety to the diet, it also provides the livestock with their own 'medicine chest'. They will 'self medicate' their way through almost any health issue (including worms).
To be most effective, it needs four basic components:
* Warm season grasses
* Cool season grasses
* Warm season broad leaves
* Cool season broad leaves
Simple metabolic physics seems to me to suggest that you will get more energy (calories in your case, but likely true of protein and fat also) the lower you eat on the food chain, and so using a given area to produce edible plant matter like wheat or sugar should be more productive than devoting it to fodder for an animal which you will later eat, or it's milk. The animal is obtaining it's own calorie needs from the area as well, and then you are taking it's surplus. Though maybe you are planning to feed the wheat or beets to animals as well. In that case you would need to think about the issue of energy in versus energy out. Annuals are often more productive in terms of short-term yield, but they take more inputs (including inputs of energy to prepare the soil, plant, harvest, etc.---whether fossil energy, human energy, or animal power); whereas perennials usually require less, and in the case of pastures the animal does the harvesting itself, unless you are making hay.
Companion Planting Guide by World Permaculture Association