18 MASS. EXPERIMENT STATION BULLETIN 327 



Inheritance of High Milk Production in the May Rose Family of 

 Guernsey Cows. (V. A. Rice.) A study was made of the Guernsey bull, 

 May Rose King, through all his male offspring. The production of the daughters 

 of this bull was ascertained, then the production of the 186 daughters of his 

 15 sons, then the production of the 746 daughters of his 86 grandsons, etc. 

 The study comprises 1624 bulls and 10,406 cows having a total of 12,741 

 records. The 21 daughters of May Rose King averaged 14,068 pounds of 4 

 percent milk, while the weighted average for all the descendants of May Rose 

 King is 13,598 pounds of 4 percent milk. These figures indicate that there has 

 been no increase in average production in this family of Guernseys in the last 

 35 years, May Rose King having been born in 1901. The distribution of these 

 10,406 cows follows very closely the normal curve, indicating the results of a 

 lack of selection for increasing milk production. 



When these facts are plotted, it becomes possible immediately to locate 

 the best bulls in the family. Within the same general line of breeding, there 

 will be found bulls whose charts show a continual rise through six or eight 

 generations, while other bulls in the same strain show a continual decrease. 



The coefficient of inbreeding (Wright's Path Coefficient ) for a group of high- 

 transmitting bulls was 3.62 percent; for the medium-transmitting bulls, 2.73 

 percent; and for the low-transmitting bulls, 1.75 percent. It would seem that 

 more rapid improvement might be made by the judicious and intelligent use of 

 a greater amount of inbreeding on the part of our better breeders whose 

 animals are selected for superiority in every respect. 



A Fertility Test for Boars. (Ralph W. Phillips.) Observations on the 

 semen of a number of boars have been made to determine the relation between 

 the morphology of the spermatozoa and the fertility of the animal. Boars of 

 good fertility have had as many as 172 abnormal spermatozoa per thousand. 

 The maximum numbers of abnormalities found in any one part of the sper- 

 matozoon are as follows: abnormalities of the head, 50; of the neck, 120; of 

 the middle piece, 12; and of the tail, 62. These last four figures all represent 

 different animals. Abnormalities in the semen of boars of low fertility exceeded 

 one or more of the above counts. Thus a boar might have no more than a nor- 

 mal number ol all abnormalities except for an excess of those of the middle piece 

 or of the neck; and this might be the only morphological indication of low 

 fertility. 



Development of the Testes and Scrotum in Farm Animals. (Ralph 

 W. Phillips and Fred N. Andrews.) A study is being made of the testes of 

 animals of various ages. Results to date show that spermatozoa are first 

 formed in the testes of the ram at about 21 weeks of age, and in the bull between 

 25 and 32 weeks of age. 



The tunica dartos muscle in the ram, which provides the mechanism for 

 temperature regulation in the scrotum, develops a reaction to temperature 

 changes at about nine weeks of age. This is the same time at which rapid 

 development of the geminal epithelium of the testes begins. 



Observations on a limited number of bulls indicate that a similar relation 

 exists between the development of the tunica dartos and the testes. 



Lambs that are castrated before the tunica dartos becomes sensitive to 

 temperature changes fail to develop this sensitivity later. If castrated after 

 the scrotum has become sensitive, the sensitivity tends to be lost. 



Injections of 60 cock units or more of testicular hormone ("Hombreol") into 

 a few lambs has resulted in some precocious development of the tunica dartos. 

 Smaller doses gave negative results. 



