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Use of an improved technique to analyse repeated measurements of live weight from an experiment involving sequential weaning treatments

Published online by Cambridge University Press:  02 September 2010

V. S. Shanmugalingam ,
M. J. Gibb  and
T. T. Treacher
V. S. Shanmugalingam
Affiliation:
Grassland Research Institute, Hurley, Maidenhead, Berkshire SL6 5LR
M. J. Gibb
Affiliation:
Grassland Research Institute, Hurley, Maidenhead, Berkshire SL6 5LR
T. T. Treacher
Affiliation:
Grassland Research Institute, Hurley, Maidenhead, Berkshire SL6 5LR
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Abstract

A new technique was used to analyse data from an experiment involving sequential measurements on the same experimental units. Results may be inconclusive if analysed in several univariate analyses of variance, one for each occasion, because the successive measurements contain the cumulative effect of treatments.

An experiment was carried out in which two pre-weaning herbage allowances and four ages of weaning were applied to 80 lambs and their live weights recorded twice-weekly until 25 weeks of age. The direct and residual treatment contrasts were evaluated over time using a response surface equation. The continuous variation of treatment effects over time was demonstrated simply by plotting the treatment contrasts and fitting the most appropriate equations to them. Treatment effects were tested by analyses of orthogonal regression coefficients over time, evaluated within each sex of each treatment group by multivariate analysis of variance.

Fitted equations of treatment contrasts were used to demonstrate the continuous variation of effects of pre-weaning herbage allowance on live weights of unweaned lambs, the residual effect of pre-weaning allowance on the weights of weaned lambs, and, separately, the effects of weaning and weaning age on live weights of the lambs.

All the live-weight data recorded in the experiment were used in the analyses. The assumptions made for the application of the method were satisfied and the results were much more informative than those of several univariate analyses of variance.

Type
Research Article
Information
Animal Production , Volume 33 , Issue 3 , December 1981 , pp. 233 - 239
Copyright
Copyright © British Society of Animal Science 1981

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References

REFERENCES

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