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Non-parametric lactation curves

Published online by Cambridge University Press:  02 September 2010

D. A. Elston ,
C. A. Glasbey  and
D. R. Neilson
D. A. Elston
Affiliation:
Scottish Agricultural Statistics Service, University of Edinburgh, King's Buildings, Edinburgh EH9 3JZ
C. A. Glasbey
Affiliation:
Scottish Agricultural Statistics Service, University of Edinburgh, King's Buildings, Edinburgh EH9 3JZ
D. R. Neilson
Affiliation:
Edinburgh School of Agriculture, West Mains Road, Edinburgh EH9 3JG
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Abstract

Lactation curves are fitted to data as a preliminary to estimating summary statistics. Two widely quoted curves are atbe-ct (Wood, 1967) and a(1 - e-bt) - ct (Cobby and Le Du, 1978), each of which has three parameters. Restriction to either of these curves imposes limitations on the fit to the data and can result in biased estimation of summary statistics. Alternatively, lactation curves can be generated by the use of a non-parametric method which requires only weak assumptions about the signs of derivatives of the curves. Because the non-parametric curves are more flexible, estimates of summary statistics are less likely to be biased than those based on parametric models. Use of the non-parametric curves is particularly advantageous around the time of peak yield, where the curves of Wood and Cobby and Le Du are known to fit data poorly.

Type
Papers
Information
Animal Production , Volume 48 , Issue 2 , April 1989 , pp. 331 - 339
Copyright
Copyright © British Society of Animal Science 1989

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References

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