Animal Husbandry Investigations in 1919. 265 



From these data it is possible to determine the expected 

 butter-fat of the first five lactations. First determine the ex- 

 pected milk yield and the expected butter-fat percentage of the 

 first five lactations. The product of these two constants will, 

 of course, give the expected butter-fat. 



The results above given are, of course, only strictly applic- 

 able to the Jersey and related breeds. They are further only 

 applicable to these breeds when the average milk production 

 and butter-fat percentage for the first eight months of lactation 

 equal or nearly equal the averages given in tables 2 and 4 for 

 the years under consideration. 



The Transmitting Qualities of Jersey Sires for Milk 

 Yield, Butter-fat Percentage and Butter-fat. 



A bulletin to be published shortly gives the detailed infor- 

 mation pertaining to this subject. These results may briefly be 

 summarized as follows. The objective of this study is a "Pro- 

 geny Performance" analysis of the American Jersey Registry 

 of Merit Sires, to ascertain the nature of their transmitting 

 qualities for milk production, butter-fat percentage and butter- 

 fat. Two hundred and twenty-five sires meet the requirements 

 of this test. One thousand eighty-one Registry of Merit daugh- 

 ters with their 810 test dams are included in these data. 



The milk production, butter-fat percentage and butter-fat 

 of these daughters in relation to that of their dams was studied 

 first as a whole and second to determine the transmitting quali- 

 ties of their sires individually. It was found that taking the 

 daughters as a whole the average corrected milk production was 

 9547.6zt44.75 the dam's milk production as a whole was 9391.9 

 ±51.5. The difference in favor of the daughters was conse- 

 quently i55-7±68.2. This difference is certainly not significant. 

 The daughters' average butter-fat percentage was 5.558+.011 

 and their dams was 5. 625 ±.013. The difference is therefore 

 against the daughters o.o67±.oi7 or the difference is 3.9 times 

 the probable error. These facts lead to the conclusions that the 

 mean milk production of the daughters of Registry of Merit 

 cows does not differ from that of their dams in milk production 

 and that to a small degree these same daughters are slightly 

 lower in butter-fat percentage than are the dams from which 

 they came. 



