CHAPTER XXIX 

 MENDELISM IN DOMESTIC ANIMALS 



Although there is a lamentable dearth of specific cases of Mendelian 

 inheritance in domestic animals, there is evidence enough to indicate that 

 Mendelian principles are of general validity. The difficulty is merely 

 a practical one consequent upon the long time and great financial ex- 

 penditure which are necessary for collecting critical data in animals. 

 Thus far we may state confidently, however, that none of the known facts 

 of heredity in farm animals, or in man himself for that matter, is in 

 conflict with Mendelian interpretation. Such an interpretation cannot, 

 however, be applied satisfactorily until more detailed knowledge has been 

 collected of the relation of various characters to one another. Thus far 

 practically all Mendelian data in farm animals are from herdbook 

 records, and we have gone about as far as it is possible to go with such 

 material. Henceforth it will be necessary to depend almost entirely 

 upon experimental breeding, if any progress is to be made. This chapter 

 is designed to give a record of about the present status of our knowledge 

 of Mendelian heredity in farm animals. 



Mendelism in Horses. Practically all the Mendelian data for the 

 horse thus far collected deal with coat color. About the only additional 

 data we have is that for the trotting character as opposed to pacing in the 

 Standard bred. However, in addition to the characters just mentioned, 

 Hurst lists the following contrasted characters as allelomorphic : concave 

 and convex faces; straight and curved thighs and hocks; prick-ear, 

 drooping ear, forward droop and outward droop of ears; sprinters and 

 stayers; liability to cataract blindness, breaking blood-vessels and para- 

 lytic roaring (contrasted with normal conditions) ; long-back and short- 

 back. The natural trotting gait appears to be a simple dominant to 

 pacing, although there is still considerable doubt as to these characters. 

 The records in Table LXIV are of interest in this connection for they 

 show that of these ten stallions only one, Electioneer 125, was 

 homozygous for the trotting character. It is true that two pacers 

 are credited to him, but this may possibly be accounted for by training, 

 for it is often possible to change the gait of a horse by proper attention. 



Of coat colors, chestnut appears to be the simplest one. Chestnut 

 includes a series of colors varying in depth from dark liver to light sorrel. 

 Chestnut mated to chestnut produces only chestnut. Of 14,131 matings 

 30 465 



