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The practical application of age conversion factors to dairy cattle production (butterfat) records

Published online by Cambridge University Press:  27 March 2009

A. H. Ward  and
J. T. Campbell
A. H. Ward
Affiliation:
Technical Officer, Herd Recording Council, New Zealand Dairy Board
J. T. Campbell
Affiliation:
Lecturer in Mathematics, Victoria University College, Wellington
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Extract

1. From an analysis of the records from 702 cattle of predominating Jersey type tested for at least six consecutive years under normal and average herd conditions in New Zealand, the authors have attempted a detailed study of the nature of the increase in production according to age.

2. They are unable to find any evidence supporting the theory that increase in production for dairy cattle operates as a percentage addition from early age to maturity.

3. The evidence secured from an analysis of 702 Jersey records of six consecutive lactations commencing at 2 years of age, strongly suggests that the increase in production according to age can be summarized neither by a percentage addition nor a constant addition alone, but is best represented by a regression formula of the nature X = aY + b, where X equals the maturity production and Y the immature production.

4. The strict regression formula will probably change according to the interpretation of “maturity equivalent”, but in general its application should lose little of the simplicity of the ratio form of conversion.

Type
Research Article
Information
The Journal of Agricultural Science , Volume 28 , Issue 4 , October 1938 , pp. 509 - 522
Copyright
Copyright © Cambridge University Press 1938

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References

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