222 AGRICULTURE OF MAINE. 



was Herd A. Bringing both herds to the same basis of effi- 

 ciency (lOO per cent)', however, it is plain that the cozus in 

 Herd A are much better cows than those in Herd B, the 

 average production per cow on the same efficiency of operation 

 basis being about i6 pounds per day higher in the former than in 

 the latter. This is the fact. Herd A is one of the best herds 

 of pure-bred Holstein-Friesian cattle in the state, nearly every 

 cow having an A. R. O. record. Herd B is only a fair average 

 herd. 



Table 2 has many uses besides that of herd comparison here 

 illustrated. It may be used for the comparison of individual 

 cows. It forms a much more scientifically accurate basis for 

 the age correction of advanced registry records than do the 

 rules of entry to advanced registry of any association in this 

 country. 



(c) ANALYSIS OF BILTMORF RECORDS. 



This matter will be considered in a later section of this 

 paper (Cf. p. 240). 



II. The Study of Inbreeding in Dairy Cattle. 



During the past year the work on the theoretical side of this 

 problem has been extended along two lines. The first' deals 

 with the results which may theoretically be expected to follow 

 the continued mating of first cousins of dififerent types, and 

 also continued mating of the type uncle x niece. The second' 



^Of course any other percentage could have been taken instead of 100. 

 The essential thing is to compare both herds on the same percentage 

 basis of operation efficiency. One hundred per cent is as good, and in 

 some regards perhaps better than any other basis on which to make 

 the comparison. 



'Pearl, R. Studies on Inbreeding. VI. Some further considerations 

 regarding cousin and related kinds of mating. Amer. Nat., Vol. XLIX, 

 pp. 570-575, 1915- 



^Pearl, R. A System of Recording Types of Mating in Experi- 

 mental Breeding Operations. Science, N. S., Vol. XLII, pp. 383-386, 



1915- 



