用sas软件建立模型如下：The experiment was a completely randomized design with goat as the experimental unit and Zn intake as the treatment. The data were analyzed by one-way ANOVA using the GLM procedure (SAS, 1988). Treatment means were compared using linear and quadratic orthogonal contrasts. The significance level was established at P<0.05. The model was as follows: Yij =μ+Ti+εij, where Yij is the dependent variables; μ is the overall mean; Ti is the effect of Zn supplementation (i=1, 4); εij is the random error.

老外意见：It would seem that linear and quadratic effects should be included rather than the overall treatment effect. 这句话什么意思？模型建的不对么？请高手帮忙解答一下，谢谢！