Volume: 50 Issue: 1
Year: 2019, Page: 45-48,
Received: Feb. 26, 2018 Accepted: April 14, 2018 Published: Jan. 1, 2019
In most of the animal experiments, observations are taken from the animals at different points of time. Such data is known as repeated measures data and analysis of such data is to be carried out using mixed models. Determination of the most appropriate covariance structure is very importantwhile using mixed models. In present days, some of the journals like Canadian Journal of Animal Science accept only those papers which are reporting mixed procedure to analyse the data sets that include repeated measurements. Hence, a study was conducted about the use of mixed models for repeated measures data. In this paper the method is illustrated with milk yield data.It is recommended that the mixed model be used for analysis of repeated measures designs in animal studies.
Keywords: Mixed model, Repeated measures, Covariance structure
Goonewardene, L. A., Price, M. A., Stookey, J. M., Day, P. A. and Minchau, G. 2000. Handling, electric goad and head restraint: Effects on calves’ behaviour. J. Appl. Anim. Welfare Sci.3: 5–22.
Huynh, H. and Feldt, L.S. 1970. Conditions under which mean square ratios in repeated measurements designs have exact F-distributions. J. Am. Stat. Assoc.65: 1582-1589.
Huynh, H. and Feldt, L.S. 1976. Estimation of the box correction for degrees of freedom from sample data in the randomized block and split plot designs. J. Edu. Stat.1: 15–51.
Prasad, A. 2014. Climatic adaption and stress evaluation of cross breed cattle of Kerala. Ph. D. thesis, Kerala Veterinary and Animal Sciences University, Pookode, 134p
. SAS Institute, Inc., 1999. SAS/STAT user’s guide. Version 8. SAS Institute, Inc., Cary, NC.
Wang, Z. and Goonewardene, L.A. 2004. The use of mixed models in the analysis of animal experiments with repeated measures data. Can. J. Anim. Sci. 84: 1-11.
ZoBell, D. R., Goonewardene, L. A., Olson, K. C., Stonecipher, C. A. and Weidmeier, R. D. 2003. Effects of feeding wheat middlingson production, digestibility, ruminal fermentation and carcass characteristics in beef cattle. Can. J. Anim. Sci.83: 551–557.
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