1. REFERENTES TEÓRICOS
3.3. REFLEXIONES EN TORNO AL PIC REALIZADO EN UNA INSTITUCIÓN
3.3.2. POSIBLES DIFICULTADES Y EXIGENCIAS PARA LA IMPLEMENTACIÓN DE
4
� P r-l +> ..c: til .... <lJ s:: <lJ () <lJ3
Q) r-l tl:. � til III <lJ � 02
45
50
55
F l e e c e We i ght - Bo dy We i ghtRe l a t lc neh 1 pB f'o r Lamb e
c!
+ +6 0
6 5
70
Body We ight( lb )
S i n g l e l amb s75
l ambsX Me a ns f'o r �- type regre s s i o n s
flI + +
No t e : The me a ns o f' s exes a re s hown fo r tw i n l a mb s o nly
Source
To tal
T ab le 4 8
Ana lys i s of Cova r i ance of Ho gge t Fleece
Weights Co rrected fo r Body We i ght
d. f. Res idua l Mean S quar e F
p
Wi thin groups D iffe rence 65 64 1 1 29 . 61 6 1 2 3. 71 8 5 . 89 8 1 . 9 0 3 5 . 89 8 3. 1 0 < 0 . 1 Regres s io n co effi c i en t wi thi n gro ups 0. 094 + 0 . 0048 All meas ureme nts are in po und s .
Tab l e 49
Hogge t Fleece We ights Clas s ified by Geno type
Geno type NN N+
Fleece we ight -- - -- ---- -
9 . 44
Fleece we ight at the same body we i ght
9 . 87
AIr measurements are in po unds .
The means ro r male a nd remale lambs have been plo tted ro r the d iffere n t geno types in the twin groups and the se show
tha t there was a consi s tent tenden cy fo r ewe lambs to have a higher fleec e we i ght ro r the i r body we ight . Thi s i s sho wn by the po s i tion of the me ans rel a t i ve to the appro pr i a te
regres s i o n line ; the means fo r females are above and tho s e fo r mal es b elow the regres s ion l ine i n e a c h c ase. The reaso n for thi s i s obs cure at thi s s ta ge.
2. Ewe ho gge ts.
Only a rew o rdinary hogge ts could be kept to 1 5 mon ths of age and i t was cons idered tha t the n umbers of e ach b i rth
rank group were insuff i c i ent to est ima te regression coeff i c i ents wi thin these groups. S i ngl e s and twins have therefo re been taken to ge ther fo r thi s ana lys i s .
The observed and co rre c ted means o f the fleece we ight are sho wn in Table 49 , where the correc tio n i s fo r body we ight.
I t can be s een that the d ifferenc es are b e tween N- type and
N+)
and the o rdinary hogge ts . The value of the regre s s i o ncoefr i c i ent wi thin the se two groups w a s used t o ob tain the
correc ted values . There i s a d ifference of about 0. 7 lb
(
Tab le 48 ) in favour o f the �- type she ep at cons tant bo dy we i ght. I ti s po s s ib le tha t di fferen ce s i n the yield of c lean woo l could a c co un t fo r a par t of thi s , but the yi eld of a coarse woo l 1 s
likely to b e greater than a finer one in whi ch case the c lean fleece we ight dirferenc e s would be grea ter.
Fra ser
(
1 95� b)
reports no differen ce in fle ece w e i ghtbetween �- type and ordinary sheep, thi s be ing reQui red fo r his
theory o f compe ti tion b e tween fo ll i cles ; however , no corre c t
ions were made for body we i ght and de tails of the plan of experime n t are no t g i ven. From the regre s s ions and means
86
shown in F ig ure 7 i t can be s een how cons ider ation of fleece we i ght alone could lead to the conclus ion tha t no di fferences exi s ted ; s in ce the difference in bo dy weight compensates fo r the difference i n fle ece we i ght . I t could be argued tha t thes e differences d i s appear when the an imals are o lder , b ut by thi s time the e wes will have been ma ted and lamb i ng performance would have to be taken into account. Becaus e of the effects of lambing o n wo o l growth , the cons idera tion o f fleece w e ights prior to the firs t ma ting i s a b e tter guide to fundamental re lationshi ps b e tween fleece type and fleece we ighte.
Figure 7 a lso shows the means o f the different geno types
and b i r th ranks and i t can be s een that the twin lambs sti ll tend to show large r geno typi c differences than the s ingle lamb s . The N + twin lamb s which were reared as s ingles ( 4 ani mals)
appear to be complete ly anomalous as they had a far hi gher co rrec ted fleece weaght va lue than any of the o ther groups.
As all the a n imals were ewe s , s ex d ifference s canno t .e inve s ti ga ted but o therw i s e the resul ts are s imi lar to tho se ob tained for the fleece wei ghts o f the lambs only wi th smaller d i fferences rel a tive to the greater average fleece wei ghts. Summary of Section V, A.
( 1 ) The �- type she ep showed a greater greasy fle e ce wei ght a t cons tan t bo dy w� ight than the o rdinary she ep.
( 2 )
There was a greater diff erenc e b e tween the twi n than be twe en the s in gle lamb s and po ssible reasons fo r thi s ared i s cu s s ed.
( 3 ) I t is cons idered tha t real diffe renc e s in clean woo l wei ght
were like ly to have o c curred.
( 4 ) I t i s po s s ible tha t ewe lamb s had a greater f leece wei ght