Professor Robert Sitkoff of Harvard Law School, an expert on trusts and estates, points out two errors in my post and also suggests a further point about trust governance. He writes that the uniform act is styled the "Uniform Trust Code," not "Act," and that section 408(c) authorizes the court--not the trustee, as stated in the second to last paragraph of the post--to reduce a bequest for the care of an animal. Limiting the power to reduce the gift to the court is critical especially when the trustee is the remainder beneficiary, as it is easier to reallocate a bequest to oneself than to undertake the distasteful act of killing the animal.
But notice the governance problem posed by a trust for a pet animal. Normally a trust must be for the benefit of an ascertainable beneficiary. This rule, which the English call the "beneficiary principle," ensures that there is someone with an economic incentive to police the trustee's conduct. Contrast the world of charitable trusts, where the absence of such a person leaves supervision (such as it is) in the hands of the distracted (at best) state attorneys general. For a pet trust, the UTC addresses the enforcement problem by authorizing the donor or the court to name an enforcer. In functional terms, therefore, the Code treats dogs and other pet animals as if they were children. Both children and pets are permissible beneficiaries, but both require an alternate enforcement mechanism (albeit one that creates another agency relationship) because neither can bring suit themselves.