A MENDELIAN EXPERIMENT WITH A BEI-~DEEN- ANGUS AND WEST HIGHLAND .

Br J. A. S. WATSON, B.Sc., M.C.

(With Pt;~o XII.)

WItILE Mendelian mlalysis has been very successfully ;~pplied to the study of the heredity of the smaller animals and of plants, very little progress has so fi~r been made in the investigation of the mode of in- hcritmme of the char~mters of the larger and more imporLant do,ncstieatcd ~mim~ls. This t~ct ix of course sufficiently explained by the obvious (lifticnlties--the large fimmeial outlay and the extended period of time necessary to obtain experimental results. It would appear, however, theft there is no alternative to the method of tedious breeding experi- ments it" the many and important problems connected with anim~l breeding ~re to be solved. A certain mnmmt of progress has indeed been made by the study of records conIa~ined in herd- ~md stud-books, but it is certain that the results of such investigations lack the scientific conclusiveness of those of earefi~lly planned and eritienl experiments. Thus such ml apparently simple question as that of the inheritance of the red, white and roan eolours in cattle, on which practically unlimited statistie~l evidence is available, has been investigated by sever~l workem, and three quite distinct Mendelian interpretations have been proposed--by Wilson (1), Laughlin (2), and Wentworth (3), respectively--no one of which gives a complete and satisfimtory expla- nt~tioH of the flints. The present experiment was commenced in 1910; the object laid down was to determine the mode of' inheritance, in crosses between -Angus and West Highland Cattle, of the horned and polled conditions, of eolour differences, of hair characters and of differences in eonformation. The two breeds may be briefly described. The Aberdeen- Angus is black in eolour, with the exception that a small amount of' white is permissible on the underline behind the umbilicus, and on the end of the bail. It is hornless, with a relatively short, smooth coaL, and is of the early-maturing type--i.e, short of leg, blocky, wide, heavily fleshed and small boned. With regard to the purity, in the Mendelian 60 Mendelian Expcrhne~t with Ccettle scllsc, of the colou,' and of bhe hornless condition, it is to be noted that red eah, es a,'e occasionally bo,'n li'om ])ure b,'ed black parents even in l)he most ea,'eft, lly selected he,'ds. White ,na,'ki,lgs, beyonil ~hose per- rail)ted by the b,'eed stand~u'd also occur al~ times, ,no,'e pa,'tieularly white feet. Ho,'ns, o,' ,no,'e gene,'ally what are called "sett,'s"--s,nall, firm or loose ho,'ny excrescences--were once eo,npa,'~ively common bu~ haw ~, now been all but eli,ninated by selecti~m. The general eha,'aete,' of West H ighl~md cattle is well known. They carry large sp,'eading ho,'ns, a long and shaggy coat, and a,'e of beef type, short~ of leg ~md blocky buI~ distinctly narrower in build ~md less hc~vily tleshed than the Aberdeen-Angus. They are also characteristically lal~er in reaching maturity and less readily ti~ttened. The eolom's are many-- red, black, yellow, dtm and brindled--'teeurate classification being some- what difficult in ~ percentage of eases. In the prescn~ experiment caLl;h; ot' only two eohmrs were ineluded--viz, red and dun. Four different pedigreed Angus were employed in the experi- ment, and were ma~ed to seven different pure bred West Highland cows. Apart from ~he latter, two cows, which happened to be available, were included, the result of a cross between the Char~ley (a white horned breed, with black "points") and the West, Highhmd. One t}enlale of l~lle Angus x Chartley-I:Iighhmd cross was ret;~ined fbr breeding. The in- heritance of the individual characters may now be considered.

(1) COAT AND CONFORMATION. Untbrtunately no data worth presenting were obtained with ,'egard to the inheritance of these characters. Attempts we,'e made dt,,'ing the earlier part of the experiment to reduce the descriptions of the coat to ~mtttal measurements of the length and dia,ne~e,' of the hai,'s. The main difllel,lty, apart from that of sampling, w'~s that the seasonal differences wu'ied greatly as between different anim'ds--e.g, an animal which had ~ relatively heavy winter co~t might have a relatively light summer cock Again the hal,' development is influenced by causes other than heredity, notably by the "condition" or degree of t~t,mss, and pregnancy. The value of' t,hese ,neast,,'ements was therefb,'e doubtful, but frequent mad regula,' exa,nination ,night still have yiehled something of interest. The ~mtho,', howeve,', was able to see the cattle only at ,'a,'e and i,','egula,' intervals du,'ing l~lle pe,'iod of the w'u', and this line of investigation w~ of necessity given t,p. The gene,'al imp,'ession ,nade by the cattle wa.s that the first hyb,'id generation w~ inte,',nediate with ,'ega,'d to coat. J. A. S. WATSON 61

The individuals were similar in coat cliaracter, with one exception ( ~ No. 8), which was distinctly shorter haired. In F. there was certainly some tbrm of segregation, individuals being obtained which approached somewhat the Highbred type and others which were almost or perhaps quite as smooth as the average Angus (cf. P1. XII, fig'. 2). The distribu- tion, however, suggested a ratio considerably more complex than the simple monohybrid one of 1 Rough:2 Intermediate :1 Smooth. With l'eg;~rd to conformation, certain of the F., suggested rai;hev strongly, in one or other point, one of the parental ~ypes; but no statement beyond this woukl be justifiable. (2) HoaNs .m) COLOUR. Below tbllows a descriptive lisb of all the animals bred during the course of l~he experiment. 60 1toms. The existing true breeding types of cattle arc either (a) horned in both sexes, or (b) polled in both. The third possible condition, which is fbund for example in certain breeds of , in which the males bear horns while the females arc hornless, is not known among living cattle, though Major (4) has described this condition in skulls fl'om the tertiary deposits in Italy. It"l Generation.

SIRE ~)A~I

Ref. B-ef. Breed and Itef. Breed and Date No, Sex No. description No. DeSel'|l)tiOll born Itorns Coh)ur I~elllarks le, 1 AA 1 Angus-Black- H 1 W. Highland Dec. 1911 Short Black Polled Dm'k Red, horns Horned 1,', 2 9 AA 3 ,, H, C 3 Highland x Feb. 1912 Polled Dun Charfley Reddish Dmb Horned F, 3 c? AA 3 ,. H, C 4 Highland x Apr. 1912 Polled Red Sold ~A 3 Chartley months old Reddish Dun, Hornet] F, 4 AA 1 ,, H 2 Highland Dark May, 1912 .9 Black.9 Still born Red, Horned F, 5 AA 2 ,~ H 5 Highland Jan. 1912 Polled Dun Yellow Dun, Horned Ft 6 AA 2 ,, H 6 Red Horned Dec. 1911 Polled Black F, 7 AA 2 ,, H 7 Red Itorned Jan. 1912 Polled Black I"1 8 AA 4 ,, H 9 ?* Horned Jmm, 19117 Polled 1]lack y, 9 AA 4 ,, H 9 ? ~ Horned Feb. 19127 Polled Black 1'~1 No. 8 and No. 9 were purchased its yearlings. Their deseenL from a pedigreed Angus and pure bred Highland cows was nnquesLionable, but their parLieular dams conld not be identified wifll certainty. The latter were probably red. 62 Mendelian Experiment with Cattle

It'.. Generation. Ref. Nc~ Sh'e Dam Calved Sex 11ortm Colour F2 1 Fl 1 I"1 2 1914 Female Polled Black 1",, 6 .... 1915 Female Horned Dun 1;2 iI .... 1916 Female Polled Dun I; 2 17 .... 1917 Female Polled Silver Dun I; 2 23 .... 1918 Female Polled Bed I,'~ 2 1"1 1 1,"1 5 1914 Female Polled Black 1,'., 7 .... 1915 Female Polled Dun I,',~ 12 .... 1916 Male (east.) Polled Red I,'~ 18 .... 1917 Female Polled Dun 1,'~ 3 Fx 1 1"1 6 1914 Female Polled Black 1,',, 13 .... 1916 Male (east.) Horned Black I,',, 19 .... 1917 Femlfle Horned Red I"2 24 .... 1918 Female Polled lled 1,'., 4 1"1 1 1"1 7 1914 Male (cast.) Hardseurs Bh~ck under hair 1,'., 8 .... 1915 Male (east.) Horned Black 1,'., 14 ,, ,, 1916 Female Horned Black F., 20 ,, ,, 1917 Fenmle Polled Red 1,~ 25 ,, ,, 1918 Female Polled Black 1,'., 5 l,'l 1 1"1 8 1914 Female Polled Black 1,'., 9 .... 1915 Male (cast.) Horned Black F~ 15 .... 1916 Male (cast.) Horned Black I; 2 21 ,, ,, 1917 Female Polled Black 1,',, 22 .... 1918 Male Polled Black F., 10 l"l 1 1"1 9 1915 Female Polled Black I,'~ 16 .... 1916 Female Polled Black Note. There is some doubt about the respective dams of F2 13 and 14 and 19 and 20. It is possible that the dams are reversed in either case or both, i.e. 13 and 19 may be from 1,'j 7 and 14 and 20 fl'om 1"1 6. In the present experiment the F~ generation females were all "clean polled," i.e. without any trace of development. F~ No. 3, a bull calf, was sold for slaughter at three months of age, at which time no horn development had occurred. The bull F~ No. 1 (PI. XII, fig. 1) developed peculiar short stout horns, which grew at an abnormally slow rate. At 18 months they were about 4 ins. long. At 6 years they measured 10 ins. There can be no doubt that this animal, like the other F~ crosses, w~ heterozygous for the polled character. We should therefore conclude that the polled condition is completely dominant in the female, while in the hybrid male the horn development is inhibited, but at least not always completely suppressed. These results are in accord with those of Gowen (5) who obtained the following in first hybrids between Aberdeen- Angus and various horned breeds. IIornod llard sours Loose sours Polled

Male Female M~tle FemMo Mlflo Fomttle Male Female 2 0 3 0 7 1 2 10 J. A. S. WhTSON 63

On the other hand, Lloyd Jones and, Evwu'd (6), in crossing the Galloway (polled) and Shorthorn obtained l~he following in 78 F~ : 70 Clean l?ollcd, 6 Scuffed, 2 Horned. Unfortmla~ely the sexes of ~be eight exceptional animals are not givcn, but the two horned animals are attributed by the autho~, with nmch reasonableness, to the probably impure condition (with regard to horn- lessness) of certain "grade" Galloway cows which were included in the expcrimcnt; and they found "no cvidcnce that sex is in any way con- nected with the inheritance of these characters." Against this it may be mentioned that among crosses between Red Polls and Ayrshircs aI, present being bred in Dmnfi'icsshire, a largc proportion of the lt~ males bear horns. It al)l)ea~ certain that th ~ degree ofdominance of thc pollcd character in the male varies according to the particnlar breeds employed, and wu'ics ~oo a.~ bctwcen different individuals of the same cross. In the present experiment the distribntion of horus in F..~ was as fbllows : Polled llarll 'lselll'.~I" Nornlal lll}l'lls Females ...... 15 -- 3 Males (castrated) ... 2 1 4

Totals ...... 17 1 7

Including the male with "scurs" as polled, we obt:~in the numbers 18 polled, 7 horned, which agrees very closely with the simple Men- delian ratio of 3D : 1R. As the numbers arc small, it is probably worth while to combine them with those obtained by Lloyd-Jones and Ew, ard in the F,, of the Galloway x Shorthorn cross above referred to, thus : Female Male 'I'ot,~tls

Polled Itorne~! Pollell IIorned I'olled Horned Present Experiment 15 3 3 4 18 7 Lloyd Jones and Evvard i~.' 9 4 7 1 16 5

Totals ...... 24 7 10 5 34 12 Expectation (3D : 1R) 23"25 7"75 11"25 3"75 3-'1.'5 11"5

The numbers are again in very close agreemenL with the hypothesis, originally advanced by Batcson and Saundels (7) and Spi]]man (8 and 8a), that the horned and polled conditions form a shnplc pair of Men- delian characters. To revert to the question of dominance in the male, Wood (9) and Arkell (10) have fonnd that in crosses between horncd and lmrnlcss 64 Mendelian Experiment with Cattle breeds of sheep, the heterozygous, males are horned, while the hetero- zygous females are hornless. The horn development in the hybrid male has been shown to be dependent on a hormone secreted by the testis, and horn growth is stopped (again in the hybrid) by castration. The analogous experiment has not been performed with cattle. It is to be noted that the F,, males were all castrated.

(b) Colour. The F1 generation, with the sole exception of the red calf F1 3, were either dun or black. With regard firstly to the bchaviour of black and red, we should conclude that black is dominant, red recessive. Matings of the heterozygous F~ blacks inter se (F~ females 6, 7, 8 and 9) produced 16 F., of which 13 were black, 3 red, against an expectation of 12 and 4~. These results may be regarded as in complete accord with the accepted view, originally advanced by Spillman (11) that red behaves as a simple recessive to black. The red calf F~ 3 calls for further explanation, but a highly probable explanation is at hand, namely that its Aberdeen-Angus sire AA 3 was heterozygous for black. The appearance of the recessive reds in pure bred Angus herds, already referred to, renders such an explanation inherently probable. Moreover the bull in question was in use by a local farmer for crossing with heifers of mixed colours, and with them he begot a large proportion of red and red-roan calves. In this connection it may be said that the sires AA 2 and AA 4 left no red calves in the herds where they were used on cattle of various colours. AA 1 cannot be regarded as having been tested. The dun x black matings constitute a more complex problem. The hypothesis thus far proposed must first be considered. Wilson (12 and 13) has proposed a series of Multiple allelomorphs or "polygamous factors," any one of which behaves as a Mendelian alternative to any other. In so far ~ the present experiment is concerned, three factors would be concerned, viz. B (black), R (red), and L (Light Dun). The following are the colours allotted by Wilson to the various possible factor combinations : BB Black (homozygous) BR Black (heterozygous) BL Dun RR Red IEL Yellow LL Light Dun J. A. S. WATSON 65

According to this the dun F~ females 2 and 5 would be BL and the F~ male of course BR. The chances of the various combinations would be IBB Black (homozygous) IBR Black (heterozygous) I BL Dun [ RL Yellow We should therefore expect a ratio of 2 Black : 1 Dun : 1 Yellow. The obtained results: 2 Black: 5 Dun: "2 Red, not only suggest a different ratio, but give a colour which is not pro- vided for by the scheme. As h~ already been pointed out by Babcock and Clausen (1r Lloyd Jones and Evvard in the expel'iment, already alluded to, obtained 6 reds out of 26 F2 ill crosses of White Shorthorn and Galloway, which again are inexplicable on Wilson's theory. The lattel', in its present form, must thel.'efore be regarded ~s inadequate. Wright (15), on the contrary, has proposed a system of ordinary unit factom, only two of which would be concerned in the present case, viz. : E, black, its absence e giving red, and D, a dominant pigment dilution factor, in whose presence black is modified to dun, and red to yellow. The nine possible factor combinations give the following respective eolom's : ddEE Black, homozygous ddEe Black, heterozygous ddee Red DdEE Dun (homozygous for black factor) DdEe D ttl~ (hete~'ozygous for blaclcf~tcto~') Ddee Yellow DDEE Cream dun (homozygous for black factor) DDee Cream (light dun) On this hypothesis the male F~ 1 wo-ld be ddEe, and both dun females, F~ 2 and F~ 5, DdEe ~. The possible combinations and the probable fi'equency would then be:

1 No. 5 might conceivably have been DdEE, although the chances are slight, black being a comparatively rare eolour among Higlfland cattle. The fac~ that she produced a red calf, however, shows definitely that she was heterozygous for the black factor. Journ. of Gen. xl 5 66 Mendelian Experiment with Cattle

1 Dd~l~iT ,'~ (du,~), 2 DdEe (dun) = 3 dun 1Ddee (yellow) = 1 yellow 1 ddEE (black), 2 ddEe (black) = 3 black 1 ddee (red) = 1 red. The results obtained, 5 dun, 2 black, 2 red, while not agreeing closely with expectation, contain nothing that is definitely opposed to Wright's hypothesis. It is obvious, however, that, so far as concerns the present experiment, a third explanation is possible, which has the merit of greater simplicity, viz. that the factor D is not a colour dilution factor, modifying both black and red, but an independent factor for dun colour, epistatic to E (black), and producing dun whenever present. This hypothesis would give an expected ratio of ~ dun, 3 black, 1 red, which is comparatively near to the ratio obtained. The numbers are, however, obviously too small to furnish any definite proof of such an hypothesis.

CONCLUSIONS. (1) The polled and horned conditions form a simple Mcndeliall pair. The polled condition is completely dominant in the female, while in the heterozygous male horn development is inhibited but not always sup- pressed. (2) Black is dominant to red, and the colours behave as a simple Mendelian pair. (3) The hypothesis of multiple allelomorphs for colour, proposed by Wilson, is not in agreement with the results obtained. (4,) Dun is dominant to black, but whether as a simple epistatic, o1" whether produced by a dilution factor capable of modifying colours other than black, does not appear from this experiment. The author desires to express his thanks to the Fund for Research, University, and to the Board of Agriculture for , for the necessary funds; to Lord Forteviot of Dupplin for providing facilities for the work, and to his lordship's agent, Mr J. J. Simpson; to Mr Win. Bruce, B.Sc., Edinburgh and East of Scotland College of Agriculture, who supervised the experiment during the greater part of the period 1914-1918 ; and to Prof: J. Cossar Ewart of Edinburgh University, and Sir R. B. Greig of the Scottish Board, for assistance and advice. JOURNAL OF GENETIC8, VOL. XI. NO. 1 PLATE XI

Fig. 1. li'i Bull at 2 years 9 months old.

Fig. 2. F,, Yearling heifers showing extreme types of coat. Of similar age, and from the same lot.

Fig. 3. Dun Fx Cow with Black//',, Calf. J. A. S. WATSON 67

EXPLANATION OF PLATE Xll. :Fig. 1. Yl ~ (No. 1) at 2 years 9 months old. Fig. 2. Two F2 yearling heifers shewing extreme types 0f coat. Fig. 3. Dun Yl cow with black F2 calf.

LITERATURE CITED. 1. WILSON,JA~IES. "Mendelian Characters among Shorthorn Cattle." Sci. Prec. RoTj. Dub. See. 11. (1908.) 2. LAU(~nLIN,H.H. "The Inheritance of Colour in Shorghorn Cattle." Am~'. 5raturalist, Vol. v. 45. No. 540. (1911.) 3. WENTWORTH, E. N. "Colour in Shorthorn Cattle." American Breeders Magazine, Vol. v. No. 4. (1913.) 4. MAJOR, C. F. J. "On the Mammalian Fauna of the Val D'Arno." Quart. Jour. Geol. Soc. Long. Vol. v. No. 41. (1885.) 5. GowE.~, J. W. "Studies in Inherit~nce, of cel~ain characters of Cross(~s between and Beef Breeds of Cattle." Jour. Agrlc. Research, WasMngtou, xv. 1. (1918.) 6. LLOYDJONES, O. and EVVARD, J.M. "Inheritance of Oolour and Horns in blue-grey cattle." Iowa Sta. Research Bull. 30, Ames, Iowa, 1916. 7. BATESONand Saum)Eas. "Experimental Studies in the Physiology of Here- dity." Royal Society (London). Repts. Evolution Committee, No. 1, footno~, p. 160. (1901.) 8. SPILL~AN,W. J. "Mendel's Law in Relation to Animal Breeding." Repts. Amer. Breederg Association. (1905.) 8a. SPILLMAN, W. J. "A Mendelian Character in Cattle." Sdence, N.S. 23, No. 588, p. 549. (1906.) 9. WOOD,T.B. "No~e on the Inheritance of Horns and Face Colour in Sheep." Journal Agric. Science, Vol. I. pt. 3. (1905.) 10. ARKELL,T.R. "Some Data on the Inheritance of Horns in Sheep." ttamps. A.qr. E~Tt. Sta. BTdl. No. 160. (1912.) 11. SPILL~IAS,W.J. Sc~nce, N.S. 25, :No. 634. (1907~) 12. WILSON,J. "The Colours of Highland Cattle." Sci. Prec. Roy. Dublin 5'oc. Vol. XlI. (N.S.). (1909.) 13. WILSON,J. A Manual of Mendelism. London. (1916.) 14. B-CBOOOKand CLA.USEN. Genetics i~ Relaffon to Agric~dture. (1918.) 15. Wamn% SEWALL "Color Inheritance in Mammals." (VI. Cattle.) Journal of Heredity, Vol. vHI. 11. (1917.)

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