How should we apply the command in Lev. 19:19, "Thou shalt not let thy cattle gender with a diverse kind..."?
In the beginning, God created animals and birds by kinds (Gen. 1:21, 24-25). He intended that men should follow His perfect example of purity by breeding according to kinds, but not necessarily according to breeds as men have subdivided them. There are three good reasons for God's command against mixing livestock: (1) God is not the author of confusion (I Cor. 14:33); (2) God desires that His servants should have the best quality livestock (Deut. 7:14 and 32:12-14); and (3) God expects us to be concerned for the welfare of our animals (Prov. 12:10 and 27:23). The prohibition against crossing different kinds means that we should not cross those of different types, different sizes, and different skeletal proportions. Let us consider a few examples that will help to make the command very clear. A Brahma should not be crossed with any of our other types of cattle because they are altogether of a different kind — in appearance, in bone structure, and in temperament. One of many detrimental points is that a calf from a Brahma bull will have heavy shoulder bones and a bone support for his hump. Other types of cows are not built to bear such calves. A giant male should not be bred to A tiny female animal, even if they are of the same general breed. An offspring from such a mating would cause injury and excessive birth pain to the dam, thereby violating one of the principles for which God gave this command. By the same principle, a male of excessive width of head and frame should not be bred to a female of narrow head and a small-boned, narrow frame: she is built for bearing only her own type of offspring. God's command does not expressly prohibit the mating of two similar and related families that men artificially call breeds, if such a mating does not harm the dam or produce offspring of inferior quality. From a financial standpoint, however, it is usually wiser to raise animals that are subject to registration if they are intended for the market. As Paul said in I Corinthians 6:12, things that are lawful are not always expedient. The crossing of different milk and beef breeds is usually unwise, also, although not expressly forbidden. Offspring from such a cross are often poor producers of both beef and milk. But milking and beef types within a breed, such as the Shorthorns, may be mixed, if desired. There is little difference in them — they were only recently bred out from the same parent stock. One must be careful of complications however. If a cross of this type is run on the range and produces too much milk for her calf, she might develop udder trouble or the calf could become a victim of "scours." One who wants a breed that is good for both bed and milk can find several well-established breeds-small, medium, and large — for this purpose. The more common breeds for this purpose are (from small to large) Kerry, Devon, Brown Swiss, Holstein, Milking Shorthorn, and sometimes Brahmas. Use one of these dependable breeds rather than risk financial loss and herd degrading by uncertain, experimental crosses. It is permissible to continue breeding a mixed-breed herd of good quality type if they are normal in giving birth and in other significant attributes. The reason is that most of our prominent breeds, in all types of livestock, are descended from stock that originated as crosses within a kind in the British Isles and Europe. These crosses within a kind have become established man-supervised breeds. It is usually wise to "breed out" unestablished crosses-those that have not been standardized as breeds — by using pure bred males. These same basic principles would apply to the crossing of all types of animals. Now consider the application of these principles in the case of poultry. Many breeds differ artificially only in color and may be crossed. Sometimes such crosses are more hardy and profitable Khan some of the nervous, high-strung inbred color patterns that are foolishly considered to be separate breeds. Also, since the size of the egg is not determined by the size of the male bird, and since the males of some types of fowl, such as turkeys and chickens, are frequently two to four times as large as the females, difference in size is not as important in breeding poultry as in animals. This command from God in Leviticus 19:19 was given for our good, and for the good of our livestock, so that we might learn from God those principles that we might not be able to discover for ourselves.