Section 14 — Animal Genetics and Breeding 



It is supposed that the imported bull, the 

 grandfather of the calves, is the carrier of the 

 semilethal hairlessness factor, that has been 

 transmitted to his descendants. Through in- 

 breeding, this hereditary recessive defect has 

 finally become obvious. 



Observations upon the descendants of this 

 bull are being continued. 



14.39. Gene-Hormone Interactions on Hair Pigmen- 

 tation in Cattle. L. O. Gilmore and N. S. 

 Fechheimer ( Wooster, U.S.A.). 



Blackish Pattern is a sex-influenced trait with 

 the responsible gene being found in Ohio Ayr- 

 shire and Jersey cattle in the respective frequencies 

 of 0.44 and 0.54. It is assumed to modify Bs 

 although an insufficient number of test matings 

 has been made to eliminate the alternate hy- 

 pothesis of allelism. All eighteen bulls in a 

 castration experiment lost blackishness in hair 

 on the body proper but fewer did so in the area 

 of the crest and head and none on the legs, ears 

 or switch. The difficulty involved precludes 

 establishing that the bulls were heterozygotes. 

 This opens to consideration the possibility of 

 hormone action overriding that of both genes 

 present in homozygotes. Testosterone replace- 

 ment by administration has been found to re- 

 store the pattern although not with complete 

 duplication of the original phenotype. 



To further test the validity of the premises 

 underlying the theoretical considerations an 

 effort was made to superimpose the administra- 

 tion of testosterone on the heterozygous cow 

 with intact gonads. Heterozygosity was establish- 

 ed by inference from observed phenotypes of 

 dam and/or daughters. Several such cases point 

 to the validation of the original concept. To 

 date no attempt has been made to test the re- 

 sistance of the homozygous genotype in the 

 female. 



It has now been shown that this is a likely 

 system for studying a simple phenotype resulting 

 from the combined action of gene and hormone. 



14.40. Investigations into the Hereditary Origin of 

 the Double Cervix Condition in the Meuse- 

 Rhine-IJssel (MRY) Breed. A. van Loen 

 (Geleen, The Netherlands). 



In a long-term project of research on bovine 

 fertility within the Meuse-Rhine-IJssel breed 

 (Netherlands) it was examined whether the dou- 

 ble cervix condition (DC) is inheritable and, 



if so, how it is inherited under normal conditions 

 of farm-management. 



A total of 607 DC-cases recorded as cervix 

 duplex was encountered among 16,375 cows, i.e. 

 3.7 per cent. 



DC is regarded as a gross genital abnormality 

 and is characterized on vaginal examination by 

 two ora uteri externa. The occurrence of this 

 malformation has to be considered a result of 

 arrested development of the Miillerian ducts. 



The population under study is a random- 

 mating population, the influence of inbreeding 

 and assortative mating being negligible. No selec- 

 tion has taken place according to DC. SC (single 

 cervix) and DC cows do not differ in reproductive 

 efficiency. 



Heredity is the most obvious cause of the 

 manifestation of DC in the female offspring of 

 a relatively large number of sires. The sires 

 definitely influence the incidence of DC in 

 their daughters (P<0.0001). Affected dams 

 produce relatively more affected daughters than 

 normal ones (/ > <0.01). 



Regarding the mode of inheritance there are 

 strong indications that the pre-disposition to 

 DC is due to an autosomal dominant gene (or 

 gene-complex) (p = 0.17) with incomplete, and 

 possibly strongly environmental, penetrance 

 (z = 0.13). For the period in which cattle are 

 moved from pasture to cowhouse and the period 

 in which they are inside notably affect the critical 

 stage of development of the Miillerian ducts 

 following which normal development is arrested. 



14.41. Genetical Study of "Tete de mouton" Cattle. 



J. J. Lauvergne and B. Vissac (Jouy-en-Josas, 

 France). 



The abnormality called "Tete de mouton" was 

 observed for the first time in France in the prog- 

 eny of a Limousin bull (Charmant) used by 

 the A.I. Center at SOUAL (Tarn) from Novem- 

 ber 1957 to January 1960. 



The abnormals have a typical appearance: 

 fronto-nasal trench, convex profiled nose, 

 brachygnathia of the lower jaw, exorbited eyes 

 and marked macroglossia. Ossification defects of 

 skull and abnormalities of the heart (persistent 

 Botal hole) and of the omasum are equally 

 established. 



Charmant was apparently normal. Both sexes 

 are equally frequently affected by the abnor- 

 mality, which had a total incidence of 5.4 per 

 cent among 81 1 of his progeny, born or aborted. 

 There was no relationship, either between the 

 mothers of the abnormals or between the mothers 

 and Charmant, who was used for beef production 



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