1920.] 



Breeding Dairy Cattle. 



649 



progeny of characteristics possessed by their parents and the 

 variation of progeny from the characteristics of their parents as 

 antagonistic " forces," but a closer study of the problem has 

 made it clear that, except in very rare cases, variations from the 

 type, colour, &c, of the parents may be just as truly inherited 

 from some ancestor as are the exact repetitions of features pos- 

 sessed by the parents. Further, variations may be either away 

 from or toward the ideal aimed at. The former are undesirable 

 and disappointing, while the latter constitute an opportunity for 

 progress in the desired direction. The main problem for breeders 

 is how to transmit the maximum inheritance of the desirable 

 qualities possessed by the parents. The uncertainty as to the 

 results which will follow from the mating of any two animals is 

 one of the greatest hindrances to successful breeding. 



The application to stock breeding of the discoveries of Mendel 

 and his followers has thrown considerable light on the 

 inheritance of such easily identified characteristics as colour 

 of coat, colour of face, and presence or absence of horns, but little 

 progress has as yet been made with other and more important 

 characteristics, such as high and low milk yield, high and low 

 butter fat content, capacity for fattening and tendency to 

 leanness. Progress has been hindered by the absence of 

 clean-cut dividing lines and the difficulties of identification, 

 the slow rate of reproduction in cattle, the differentiation of sex 

 and the impossibility of directly assessing the dairy qualities of 

 bulls. These difficulties, however, should be overcome in time, 

 and there are doubtless many present-day breeders who would 

 be ready to co-operate in the collection of data on single or 

 related points if some lead were given them in this direction. 

 Mendelism may one day enable the dairy farmer to breed heavy- 

 milking stock with the same certainty as the breeder of 

 Aberdeen Angus cattle breeds black and hornless animals. 



Systems of Breeding. — The systems of breeding adopted are 

 usually described by one or other of the terms crossing, grading, 

 in-breeding, or line-breeding. 



Crossing usually describes the mating of animals of distinct 

 breeds, e.g., Shorthorn with Jersey. The first cross between 

 some breeds is often a popular and useful commercial animal, 

 combining to some extent the desirable characteristics of the 

 parents. At the same time, the introduction of the 

 characteristics of another breed must increase the uncertainty 

 as to the qualities which will appear in individual offspring, 

 particularly in the second generation. Crossing, therefore, by 



