HYBRIDIZATION IN ANIMAL BREEDING 



511 



TABLE LXIX. COMPARATIVE RECORDS OF SCRUB DAIRY Cows AND THEIR GRADE 

 DAUGHTERS (Data of Kildee and McCandlish) 



which produced heifer calves to Guernsey bulls are compared with their 

 daughters, and in the third lot a Jersey grade cow is compared with her 

 scrub mother. 



This table must be interpreted with some care, because it suffers from 

 the same fault which mars a large proportion of agricultural data; things 

 are compared which are not directly comparable. In Table LXIX 

 have been presented the indices which would have made it possible to 

 evaluate these data with respect to milk production and butter-fat content, 

 but the evaluation has not been made in this case. The comparison of 

 scrub cows with their grade Holstein-Friesian daughters shows substantial 

 increases in milk production, butter-fat production, and net returns, and 

 this in spite of the fact that immature cows are compared with mature 

 ones. The increases here are due to several things. The scrub cows of 

 this lot were the most inferior of all, the Holstein-Friesian bull which 

 was used probably came from better producing lines within his breed than 

 did the bulls of the other breeds, and a more representative test has been 

 made of the grade Holsteins than of either of the other two lots of grades. 

 If proper allowance had been made for the immaturity of the Holstein 

 grades, they would compare even more favorably with their dams. In 

 the Guernsey class the average excellence seems to be somewhat lower 

 than that of the dams. The scrub cows of this lot, however, were better 

 producers than those of either of the other two lots. Moreover, the 

 immaturity of the grades in this test has had more effect than in the 

 Holstein class, because two of them are represented by first year records 

 only. Three of them were sired by a Guernsey bull which had been 

 loaned to the station, and he apparently was not a good sire of dairy 

 quality. The fourth member of the lot was sired by a Guernsey bull 

 belonging to the station and she showed an increase of over 100 per cent., 



