These observations extend over lengthened periods, on the same animals, of from thirty to upwards of fifty weeks. A cow, free from calf, and intended for fattening, continues to give milk from ten months to a year after calving, and is then in a forward state of fatness requiring but a few weeks to finish her for sale to the butchers.
It will thus appear that my endeavors to provide food adapted to the maintenance and improvement of my milch cows have been attended with success.
On examining the composition of the ordinary food which I have described, straw, roots, and hay, it appears to contain the nutritive properties which are found adequate to the maintenance of the animal, whereas the yield of milk has to be provided for by a supply of extra food; the rape-cake, bran, and bean-meal, which I give, will supply the albumen for the caseine; it is somewhat deficient in oil for the butter, whilst it will supply in excess the phosphate of lime for a full yield of milk. If I take the class of cows giving less than twelve quarts per day, and take also into account a gain of flesh of seven to nine pounds per week, though I reduce the quantity of extra food by giving less of the bean-meal, yet the supply will be more in proportion than with a full yield; the surplus of nitrogen and phosphoric acid, or phosphate of lime, will go to enrich the manure.
I cannot here omit to remark on the satisfaction I derive from the effects of this treatment on the fertility of the land in my occupation. My rich pastures are not tending to impoverishment, but to increased fertility; their improvement in condition is apparent. A cow in full milk, giving sixteen quarts per day, of the quality analyzed by Haidlen, requires, beyond the food necessary for her maintenance, six to eight pounds per day of substances containing thirty or twenty-five per cent. of protein. A cow giving on the average eight quarts per day, with which she gains seven to nine pounds per week, requires four to five pounds per day of substances rich in protein, beyond the food which is necessary for her maintenance. Experience of fattening gives two pounds per day, or fourteen pounds per week, as what can be attained on an average, and for a length of time. If we considered half a pound per day as fat, which is not more than probable, there will be one and a half pounds for flesh, which, reckoned as dry material, will be about one third of a pound, which is assimilated in increase of fibrin, and represents only one and one third to two pounds of substances rich in protein, beyond what is required for her maintenance.
If we examine the effects on the fertility of the land, my milch cows, when on rich pasture, and averaging a yield of nine quarts per day, and reckoning one cow to each acre, will carry off in twenty weeks twenty-five pounds of nitrogen, equal to thirty of ammonia. The same quantity of milk will carry off seven pounds of phosphate of lime in twenty weeks from each acre.
A fattening animal, gaining flesh at the rate I have described, will carry off about one third of the nitrogen (equal to about ten pounds of ammonia) abstracted by the milch cow, whilst if full grown it will restore the whole of the phosphate.
It is worthy of remark that experience shows that rich pastures, used for fattening, fully maintain their fertility through a long series of years, whilst those used for dairy cows require periodical dressings to preserve their fertility.
If these computations be at all accurate, they tend to show that too little attention has been given to the supply of substances rich in nitrogenous compounds in the food of our milch cows, whilst we have laid too much stress on this property in food for fattening cattle. They tend also to the inference that in the effects on the fertility of our pastures used for dairy purposes we derive advantage not only from the phosphate of lime, but also from the gelatine of bones used as manure.
On comparing the results from my milch cows fed in summer on rich pasture, and treated at the same time with the extra food I have described, with the results when on winter food, and whilst wholly housed, taking into account both the yield of milk and the gain of weight, I find those from stall-feeding full equal to those from depasture. The cows which I buy as strippers, for fattening, giving little milk, from neighboring farmers who use ordinary food, such as turnips with straw or hay, when they come under my treatment increase their yield of milk, until after a week or two they give two quarts per day more than when they came, and that too of a much richer quality.