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CANNON BONES
SO DIME SIONS, HERITABILIT!ES AND
RELATIONSHI TO CARCASS ~UALITY
IN
ROMNEY WETHER Ll\MBS
A Thesis
MASSEY AGRICULTURAL COLLEGE LIBRARY PALMERSTON NORTH, N.Z.
Pre ented in Parti l Fulfillment or the Require eats for the Degree of
• Agr. Sc.
by
A.H. l!ughes 1957
I
'l'ABLE OF CONTEN.rS
Introduction Chapter
1 ~R~e~v~i~~o~f~L~~i~t~e~r~a~t~u~r~e
2
3
Development of Long Bones
Factors Effecting DevelQpment of the Cannon ..Bone
Carcass uality
Heritability of Body Characters Conclusions
Materials and thods Experimental Animal&
Ca ridge Block Test Data used in this Study
ethods of ~nalysis The athematical odel Estimation of Heritability
Estimation of Genetic Correlations Est i.mation of Enviromnental Eff'e-cts
4
ResultsEstimates of Environmental Effects Estimates of Heritability
1
4 13 22
23
24 30 32
36 43 46 48
49
59
Chapter Page 4 (Cont.)
5
Swmnary
Estimates ·of Phenotypic Correlations sti ates of Genetic Correlations l)iscussion
Effects of ovironmental Factors Gene·tical Variation
Genetical Covariation Conclusion
Bib liosrapb.v Appendices
.ACKNO JIDGMENTS
61
63
67 10 13 74
77
80
This study as prompted by Professor A.L. Rae to whom the au thor is sincerely grateful for1 1 thout his advice, help and continued enthusiasm,this thesis would not have been
written.
Thanks are also due to r. R.A. Barton for advice on carcass quality aspects, also to Miss M.G. Campbell and the Library Staff, Massey Agricultural College for their help in obtaining references fran interloan sources.
Finally the author tishes to acknowledge his gratitude to rs A.W. Warren for typing this thesis.
INTRODUCTION
In the past and to a certain extent at the present time sheep breeders have paid considerable $ttention to the d'imensions of the cannon bones of their animals in the
belief that this hone serves as a good indicator of the quality of the conformation and constitution of their
animals. Scientific orkers interested in meat and carcass quality have also attached considerable ~ ortance to the cannon bone as an i,ndex of carcass co osition and hence of carcass quality:
The origin of the sheep breeders beliefs is no doubt due to years of farmer observation sup orted to so e extent by the findings of the scientific orkers, ho of necessity, using relatively small numbe of an ala, have established relationshi s between the dimensions of the e nnon bone and other characters of' economic _ ortance.
The existence at assey Agricultural College of complete records, concerning cannon bone dimensions and c rc as
quality, collected tram a relatively large number of animals, prompted this present study hich was intended to yield
more accurate results than those prev1ousl repor ed. At the same time this study as designed to yield esti etes of the heritability of cannon bone di nsiona and their relat- ionship to carcass quality thus providing baei on 1hich breeders might decide hether or not they ould continae to place the present amount of emphasis on the cannon b~ne
in their selection praetices.
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