Six very superior pure-bred black-faced horned ewes, belonging to Mr. H. Shaw, of Leochel, Cushnie, were served by a white-faced hornless Leicester ram. The lambs were crosses. The next year they were served by a ram of exactly the same breed as the ewes themselves, and their lambs were, without an exception, hornless and brownish in the face, instead of being black and horned. The third year they were again served by a superior ram of their own breed; and again the lambs were mongrels, but showed less of the Leicester characteristics than before; and Mr. Shaw at last parted from these fine ewes without obtaining a single pure-bred lamb.
To account for this result—seemingly regarded by most physiologists as inexplicable—Mr. James McGillivray, V. S., of Huntley, has offered an explanation, which has received the sanction of a number of competent writers. His theory is, that when a pure animal of any breed has been pregnant by an animal of a different breed, such pregnant animal is a cross ever after, the purity of her blood being lost, in consequence of her connection with the foreign animal, and herself becoming a cross forever, incapable of producing a pure calf of any breed.
To cross, merely for the sake of crossing, to do so without that care and vigilance which are highly essential, is a practice which cannot be too much condemned, being, in fact, a national evil, if pushed to such an extent as to do away with a useful breed of animals, and establish a generation of mongrels in their place—a result which has followed in numerous instances amongst every breed of animals.
The principal use of crossing is to raise animals for the butcher. The male, being generally an animal of a superior breed, and of a vigorous nature, almost invariably stamps his external form, size, and muscular development on the offspring, which thus bear a strong resemblance to him; while their internal nature, derived from the dam, well adapts them to the locality, as well as to the treatment to which their dams have been accustomed.
With sheep, where the peculiarities of the soil, as regards the goodness of feed, and exposure to the severities of the weather, often prevent the introduction of an improved breed, the value of using a new and superior ram is often very considerable; and the weight of mutton is thereby materially increased, without its quality being impaired, while earlier maturity is at the same time obtained. It involves, however, more systematic attention than most farmers usually like to bestow, for it is necessary to employ a different ram for each purpose; that is, a native ram, for a portion of the ewes to keep up the purity of the breed, and a foreign ram, to raise the improved cross-bred animals for felting, either as lambs or sheep. This plan is adopted by many breeders of Leicester sheep, who thus employ South-Down rams to improve the quality of the mutton.
One inconvenience attending this plan is the necessity of fattening the maiden ewes as well as the wethers. They may, however, be disposed of as fat lambs, or the practice of spaying (fully explained in “Cattle and their Diseases”) might be adopted, so as to increase the felting disposition of the animal. Crossing, therefore, should be adopted with the greatest caution and skill, where the object is to improve the breed of animals. It should never be practised carelessly or capriciously, but it may be advantageously pursued, with a view to raising superior and profitable animals for the butcher. For the latter purpose, it is generally advisable to use males of a larger breed, provided they possess a disposition to fatten; yet, in such cases, it is of importance that the pelvis of the female should be wide and capacious, so that no injury may arise in lambing, in consequence of the increased size of the heads of the lambs. The shape of the ram’s head should be studied for the same reason.
In crossing, however, for the purpose of establishing a new breed, the size of the male must give way to other more important considerations; although it will still be desirable to use a large female of the breed which is sought to be improved. Thus, the South-Downs have vastly improved the larger Hampshires, and the Leicester, the huge Lincolns and the Cotswolds.