is important becrulse her son Baron of Ben Lomond was popular; a large
proportion of the lines trace back to Fame through Baron of Ben Lomond .
Similarly, Flower owes her importance to the popularity of her son ,
Dean of Ben Lomond . Indeed , many of the animals appearing in the upper
part of Table 5 . 1 7 are ancestors of those in the lower half.
CHAPTER 6
BREED STRUCTURE
I t may be surmised from wha t has been wr i t te n (Lush , 1943 , 1946) tha t some f orm of ' func t ional s tratifica tion ' o f pure-bred herds
exists in mos t breeds of domes tic livestock . The theoretical implications o f this are summari zed oy Lush , who s tates tha t
" the reduc tion in ef f ective size of the populat ion which such s tratification causes , will largely increase the chanc e changes in gene frequency ins tead of the sys tema tic changes caused by selec tion , a l though there will be some o f the lat ter to the extent tha t stra t ifica t ion is based on the apparent mer i t of the animals in the herds . "
The me thod o f ana lysis adop ted in the present s tudy was tha t outlined by Wiener ( 1 9 5 3 ) and later modified by Barker ( 1 9 5 7 ) . I t
invo lves f o l lowing back the pedigrees o f regis tered animals t o find out i n which herds ances tors have been bred . · Data for this s tudy were abs trac ted from Volume 6 1 (which includes all New Zealand herds
r egis tering from 30th July 1968 to 31st July 19 69) o f the New Zealand
Aberdeen Angus Herd Book . All herds regis tering in this year were
l i s ted by their s tud pref ixes , toge ther wi th. the numbers of bulls and heifers regis terea by each , as well as the s tud prefixes of the bulls used in each .
From these data were ob ta ined the numb er o f herds that regis tered
(i) f emales only
( ii) males and f emales and
94 .
and usually conta ins small herd g or ones recently d ispersed . A further classif ica tion is used which to some extent cut s across the division of herds made above . Here the fate of the animals bred is the cri terion . The two maj or ca tegories of herds which resu l t are :
( a) Breeders ' Herds - herds which have bred bull s appear ing as sires in o ther pedigree herds in the data analysed .
( b ) Mul tipl iers ' Herds - herds whose bulls have no t appeared as s ires in o ther pedigree herds i n the data analysed . Bulls bred by these herds may have been used in the herd in which they were bred and have been used , presumab ly , in grade herd s .
The only real diff erence among the ca tegories ( to be d iscussed shor t ly) forming the lat ter group is tha t the mul tip lication process diff ers in intensity . The herds in each o f the two maj or ca tegories of pedigree herds can be placed into a number o f strata depending on their impor tanc e as a source o f br eeding material for the rest of the breed and also on their regis tration prac t ices . For examp le , the Breeders ' Herds can be subd iv ided into four stra ta . B . H . ( l ) are
thos e_ a t the top o f the s truc ture , . B . H . ( 2) and B . H . ( 3) are intermediate strata and B . H . (_4) are thos e tha t did no t have their bulls used in o ther Breed ers ' Herds but whose bulls were u sed by Mul tipl ier s ' Herds .
On the basis of the two categories as def ined earlier , the 483 herds ( in the 1969 Herd Book) can b e subdivided into 105 Breeders ' Herds
( compris ing the 4 categories outlined above) and 3 7 8 Mul tipliers ' Herd s . Of the 105 Breeders ' Herds , 80 o f them d id no t have their bulls
95 .
appear ing as sires in o ther Breeders ' Herds . However , these 80 herds d id contribu te sires to the Multipliers ' Herd s . These 80 herds comprise
the B . H . (4) stratum . The remaining 25 herds were analysed to f ind in which o ther Breeders ' Herds (wi thin tha t group o f 25) their bulls had b een used . I t was found that 11 o f these herds had their s ires used
by o ther Breeders ' Herds . Hence , 14 herds were assigned to B . H . ( 3) . The same process was repea ted on the remaining 11 herds to ob tain the herds in the two higher s trata , B . H . ( 1 ) and B . H . ( 2) (see Figure 6 . 1 ) . B . H . ( 1 ) was fur ther subdivided into two sec tions : B . H . (la) , the maj or breeder s ' herds , and B . H . (lb) - herds in this cat egory d iffer from those of
B . H . (la) in tha t their bulls were no t used in the nex t s tra tum B . H . ( 2) . There was , however , some reliance by B . H . (lb) on B . H . (la) herds for
sires .
The subclassif ica tions o f the Mul tiplier Herds (378 a l toge ther) are more arb i trary and are based mainly on regis tra tion prac t ices . They
are as f o l lows :
(_i) M . H . (H) - herds tha t registered males , but whose bulls were used onl;r in the herd in \vhich they were bred , and presumab ly , in grade herds .
(ii) M . H . (N) - herds tha t regis tered males , but who s e bulls did no t appear as sires in any pedigree herd , thus d i s t inguishing them from the B . H . and M . H (}I) clas sificat ions .
( iiil M . H . (S l - herds tha t d id no t regis ter males , and tha t d id no t appear among the B . H . OR M . H . (H) .
( iv ) M . H . (M) - herds tha t regis tered males only .
Excep t for the home-bred bulls used in M . H . (H) , the sires used in the Mul tiplier ' s Herds were bul l s purchased f rom one or more of the
FI GURE 6 . 1
Diagramma tic r epresentation o f breed s truc ture based on regis tration data in volume 61 of the New Zealand Aberdeen Angus Herdbo ok .
The figures in each block are the number o f herds in tha t s tra tum tha t registered animals in the volume analysed . The
top s tra tum is B .H . (la) and B .H . (lb) , the second is B .H . ( 2) , e tc . The f igures o n the lines from Impor ted s ires are the numbers of herds in each s tratum us ing thes e s ires .
IMPORTED SIRES 2
B,H. 1
4
B.H. 1 (b)
2 5 B . H. ( 2)4
BREEDERS ' HERDS14
B.H. ( 3)
31
80
B . H.(4)
'58
'4
I 78 I I - - --1- - - - MULTIPLIERS ' HERDS 6 290 GRADE HERDS (NON-PEDIGREE) �91 .
Breeders ' Herds . Sires u s ed in the Breeders ' Herds wer e home-bred or purchased from ano ther Breeders ' Herd in the same or a higher s tratum .
The breed s truc ture ob tained is shown in Figure 6 . 1 . Brief ly , the top s tra tum c onsis ts of a small self-contained group of herds supplying sires to each o ther and to herds in any stra tum b elow i t . The second s tra tum ob tains sires from the top s tra tum only , but supplies sires to herds in any s tratum below i t . Likewise , the third stra tum ob tains
sires from ei ther of the top two s trata and suppl ies to any below i t ,
and so on. Differences between herds in the top and lower s trata are largely determined by the number of s trata through which genes have passed . Many b reeders of grade ca t tle purchase their sires from the
top group of herds and thi s shor t-circui ting may well resul t in many o f the bulls i n high grade herds being genetically superior t o many of thos e born in herds i n the lower pedigree s trata . Because of changes over
t ime , it is unlikely tha t the ac tual struc ture of the breed is as rigid as the diagram sugges ts ; in fac t , there are some herds which would be difficul t to place exac tly . Ther efore , ' s tratification ' of herds in the Angus breed should no t be visual i zed as a hard and fas t d ivision , but rather as s everal func tional s tages wi thin the one popula t ion.
I t should be s tressed that the breed s tructure as indica ted in no way reflec t s the ac tual genetic differences b e tween herds . For exampl e ,
the s tra tum into which any herd falls will depend on whether the breeder is able (or prepared) to t urn his herd into a '"breeders ' herd ' . I t mus t also depend o n the willingnes s o f o ther breeder s to recognize the
98 .
S ince many sires are bought from o ther herds and l i t tle improvemen t is pos s ib le by cul ling females , it follows that the great maj ority o f breeders are relying o n somebody else t o d o the j ob f o r them . So , each s tra tum d epends on those above i t to effec t genet ic impr ovement and the who le breed is therefore graded to the top s tratum . Consequently , unles� the top herds are cons tantly improving , wha tever gene tic
superior i ty they may possess at any t ime is being continual ly reduced by the use of their bulls in the lower s trata .
'
CHAPTER 7
REGISTRATION PRACTICE S
I n a rapidly expanding br eed such as this , it would b e expec ted tha t prac t ically all fema les reared would be regis tered . This is n o t
the case f o r males , and there is s ome selec tive regis tra t ion o f bull calves which is essen tially cull ing of males f rom the pedigree breed . Over the per iod of time cons idered obj ective measures were seldom , i f ever , employed b y ped igree breeders i n the selec tion o f br eeding animals . Moreover , the selec t ion of males f or regis tration would have largely been subj ec tive , det ermined by conformi ty with breed type . Never theless ,
it does represent selec tion be ing applied by the breeder s ; animals cons idered of insuff icient desirabil ity being elimina ted f rom the pedigree sec tion of the breed . The ratio of females /males regis tered is then a direc t measure of the d egree of this selec tive registration of males .
The r egistration prac tices o f the various s trata are shown in
Table 7 . 1 . The average number o f females regis tered per herd is an
indication of herd s i ze , as mo s t f emales born probab ly will be registered . The mos t impor tant herds (B . H . ( la) l are also , on the average , the larges t herds , and average herd size decreases in order of decreas ing impor tance of the s tra ta . In the breed as a whole , over nine- tenths of the males born are not regis tered . The ra t io of f emales to males r egistered is lowes t f o r B . H . ( la) herds , which implies tha t these herds can d ispose of �o s t of their male progeny as regis tered animals . This is to be
TABLE 7 . 1
Herd and o f herds in volume 61 of the New Zealand
Ab erdeen Herd Book
Type of Herd Herds Males Regis tered Females Regis tered Average No . Average No
o f males of f emales
r egis tered r egis tered
% of No. regis ter- No . (%) No . ( % ) per herd per herd
total ing females
only
Breeders ' Herds (la) 2 0 . 41 -- 4 2 6 . 9 2 114 1 . 7 7 21 5 7 . 0
Breeder s ' Herds ( lb ) 4 0 . 83 -- 2 2 3 . 6 2 133 2 . 07 5 . 5 3 3 . 3 Breeders ' Herds ( 1 ) 6 1 . 24 -- 64 10 . 54 247 3 . 84 10 . 7 4 1 . 2 Breeder s ' Herds ( 2) 5 1 . 04 -- 26 4 . 28 1 24 1 . 9 3 5 . 2 24 . 8 Breeders ' Herds ( 3) 14 2 . 90 -- 48 7 . 91 243 3 . 7 8 3 . 4 1 7 . 4 Breeder s ' Herds ( 4 ) 80 1 6 . 5 6 1 ' 277 4 5 . 6 3 1568 24 . 40 3 . 5 19 . 6
Mul tiplier Herds (H) 4 0 . 8 3 -- 5 0 . 8 2 5 5 0 . 8 6 1 . 3 13 . 8
Multiplier Herd s (N) 78 16 . 15 -- 178 29 . 3 2 1094 1 7 . 03 2 . 3 14 . 0
Mul tiplier Herds ( S ) 290 60 . 04 290 - -- 3094 4 8 . 1 6 -- 10 . 7
Mul tiplier Herds (M) 6 1 . 24 -- 9 1 . 4 8 0 0 1 . 5 --
To tal 483 100 291 607 100 6425 lOO Average 1 . 3 1 3 . 3 Ra tio females/ males r egis tered 2 . 7 6 . 0 3 . 9 4 . 8 5 . 1 5 . 7 11 . 0 6 . 1 -- -- 10
. 6
_. 0 0 .1 0 1 .
expec ted as thes e are the maj or herds , tha t is , they are the mo s t
popular herds , and consequently their animals are sough t af ter by o ther pedigree breeder s . The average ratio increases wi th decreas ing order of impor tance among the breeder s ' herds , exc ept for B . H . (lb) which has the highes t ratio . Over all s trata , the highes t ratio is shown by M . H . (H) . The M . H . (S) herd s , regi s ter ing no males , are mainly sma ll herds no t cons id ered of impor tance by o ther breeder s . Presumably , they sell bulls to commercial herds , and do no t consider it wor thwhile to reg i s ter these animal s .
I · S I ZE
The B . H . � ) , (2) , ( 3 ) and (4) are analyzed in detail in Table 7 . 2 , us ing the number o f female regis tra t ions per herd as an ind ic a t ion of herd s i z e . Some allowance mus t of cour s e be made for year- to-year f luc tuations in numbers regis tered and for the fac t tha t herds
signif icant some years ago may have been d ispersed or become less fashionable or popular by 1969-the year to which the las t two tables
refer . The impor tance of the 105 breeder s ' herds ( 21 . 7 per cent of all herds) is shown by the fac t tha t they regis tered 68 . 5% o f all males and 34 . 0% of all females . The distribu tion o f herd si zes is also no t very d i f f erent from that shown in previous analyses of pedigree c a t tle breeds . In the present s tudy the maj ority of herds have been shown to fall wi thin the l imi tat ions of 1-20 c ows (representing 1 3 . 6% of total breeders ' herd s ) . A disconcer t ing f eature among thos e herds regis tering 10 o r less
TABLE 7 . 2
o f Breeders ' Herds ( 3 ) , and (4) numbers o f females in volume 61 o f the New Zealand Aberdeen Herd Book
Average Average
Female Herds No . o f No . o f · No . of males No . of f emales
regis tra tions males regis tered Females regis tered regis tered regis tered p er per herd No . % o f and per cent and per cent per herd herd
to tal 51 and over 8 1 . 7 88 ( 14 . 5 ) 625 ( 9 . 7 ) 11 . 0 7 8 . 1 4 1-50 2 0 . 4 1 3 ( 2 . 1) 9 8 ( 1 . 5 ) 6 . 5 4 9 . 0 3 1-40 6 1 . 2 17 ( 2 . 8) 211 ( 3 . 3) 2 . 8 3 5 . 2 21-30 23 4 . 8 84 ( 1 3 . 8) 568 ( 8 . 8 ) 3 . 7 24 . 7 1 1-20 34 7 . 0 135 ( 2 2 . 2) 513 ( 7 . 9) 3 . 9 15 . 1 0-10 3 2 6 . 6 7 9 ( 1 3 . 0) 1 7 1 ( 2 . 7 ) 2 . 5 5 . 3 Total 105 21 . 7 416 ( 6 8 . 5 ) 2186 ( 34 . 0) Average
3 - 9
20 . 8
Ratio females /males regis tered 7 . 1 7 . 5 1 2 . 4 6 . 8 3 . 8 2 . 25 - 3
... 0 I\) .'
1 0 3 .
are two pos s ible reasons for these small breeders regis tering such
a h igh propo r t ion of bull s to heifers . Many smal l herds belong to "new" breeders who endeavour to recover inves tments in their f ounda tion
p ed igree s t o ck as quickly as possible by the sale of pure bred bulls . O ther small herds may belong to breeders of long s tanding , but they need to sell as many bulls as possible because o f the high co s t of their herd sires . The small breeder ' s selec tion diff iculties are thus
accentua ted by f inanc ial considerations .
Donald and I triby ( 1 9 4 5 ) , in d iscussing the signif icance of herd
s i ze in cat tle , point out tha t sma ll herds are ser ious ly hindered in cons tructive breeding . The impor tance of random gene fr equency f luc tua tions - one of the maj or diff icul ties in selective breeding varies inversely as the number o f breeding animal s . Moreover , the smaller the herd , the more difficul t it becomes to progeny test and to use the info rma tion ob tained to bes t advan tage . In one or two s ire herds , as is o f ten the case in the maj ority o f pedigree herds , it is also hardly possible to discrimina te p romp tly agains t an unsuccessful sire by
d i sposing of all his pro geny . So , it. is clear that the maj ority o f
ped igree herds in New Zealand cannot fo llow any c ons is tent breeding policy o f their own , but act as mul tipliers of bulls bought from a very few impor tant herds - mul t iplication being a necessary func t ion of a propor tion o f herds in any breed o f animals with a low reproduc t ive rate .
I t mus t also be rea l i zed that '"hen the bree d is struc tured into s o many very small herds , and where A . I . i s no t prac tised , then a great ly increased number o f bulls is needed for purebreeding with a consequent
1 04 .
reduc t ion in the ir quality (by wha tever cri terion quality i s j udged) . While the exis tence of many small mul t ip lier herds (they compr ise
some 78% of total herds in the 1969 regis trations ) , each with its own bull , does no t reduce the rate of genet ic progress in the breed , it does
lower the average qual ity of those sold by increas ing the improvement lag within the breed ( Bichard , 1 9 7 1 ) .
Wi thin the smaller herds ( those regis tering 3 0 o r less females) shown in Table 7 . 2 , it was found tha t selective regis tration increases
as herd s i ze increases . However , the relat ionship be tween herd s i ze and the ra tio females /males regis tered is no t as s imp le for the larger herds