How to write this code when age and it's quadratic fitted as fixed covariates in model?

Dear friends:
I am estimating the heritability of body weight in catfish. In this
program, because there was difference between the birth date of
families, fish’s age and its quadratic were therefore fitted as fixed
covariates in the analysis models of body weight. I didn't find the
right function to finish this analysis, then I have to form a new
covariate Age2 , which raised the Age field to the power 2. In the
model, Age and Age2 were all fitted as the fixed covariates. My
question is: Is this analysis process right? Can anyone give me better
suggestions?

!RENAME !ARGS 1
 AnimalID !P
 SireID !P
 DamID !P
 FamilyID * !ALPHA
 Birthday * !ALPHA
 Wt
 Lg
 Age
 Age2 !=Age !^2
G0.dat !ALPHA !SKIP 1 !MAKE
!DOPATH $1
!PATH 1
G0.dat !SKIP 1 !MAXIT 150 !EXTRA 5
Wt ~ mu Age Age2 !r AnimalID

Luan sheng
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  Yellow Sea Fisheries Research Institute
  Chinese Academy of Fisheries Sciences
  Nanjing Road 106
  Qingdao 266071
  China
  luansheng_at_gmail.com
  luansheng_at_ysfri.ac.cn
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Received on Wed Dec 08 2009 - 08:24:08 EST