They are opt out....did you chevk mo substituions?
From the mcmurray site:
Substitutions: Occasionally we will have breeds which did not hatch as well as expected. When this happens, we would like to substitute extra chicks of equal or greater value of breeds similar to what you had ordered. If you indicate no substitutions, we will either delay your order or ship it short those birds and refund you. We have discovered that our customers usually prefer to have the original total number of chicks they ordered rather than a refund. If you phone in your order we will ask you about substitutions. If you mail your order, please indicate your substitution preference on the order blank.