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| Estimating and Predicting Feed Conversion in Broiler Chickens by Modeling Covariance Structure |
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M.F. Rosario,
M.A.N. Silva,
A.A.D. Coelho and V.J.M. Savino |
Abstract:
Modeling covariance structure was used to estimate and to
predict feed conversion in broiler chickens from one experiment under
repeated-measures design. Eight treatments that consisted in a combination
of four strains (Arbor Acres, Ag Ross 308, Cobb and RX) and two sexes were
evaluated at six ages (7, 14, 21, 28, 35 and 42 d) in two blocks with
three replicates per block. Feed conversion was subjected to a
mixed model, MIXED procedure in SAS® software, where was modeled
covariance structure using ten types. Also, it was obtained a correlogram
and analyses of variance for each structure. Means±standard errors were
estimated and polynomial trends were assessed using linear, second- and
third-order to predict the trait over ages. First-Order Autoregressive
Moving-Average was chosen the best covariance structure that is extremely
important to obtain more accuracy of estimate (from 1.048 at 7 days to
1.703 at 42 days for Cobb) and predicted (from 1.061 at 7 days to 1.577 at
42 days for Cobb) means on feed conversion, which is better predicted when
linear effect is used because it presented very closely both estimate and
predicted means at all ages, except at 14 days. Modeling covariance
structure allowed us to choose the best model to estimate and to predict
feed conversion, opening the windows to understand a little more about its
trend over ages and also to purpose nutrition managements that may be
adopted to maximize growth and to minimize total cost of poultry
production.
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How to cite this article:
M.F. Rosario, M.A.N. Silva, A.A.D. Coelho and V.J.M. Savino, 2007. Estimating and Predicting Feed Conversion in Broiler Chickens by Modeling Covariance Structure. International Journal of Poultry Science, 6: 508-514.
DOI: 10.3923/ijps.2007.508.514
URL: https://scialert.net/abstract/?doi=ijps.2007.508.514
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