Even within Deontology:

​Deontology strictly dictates that it is a moral wrong to intentionally use a sentient being purely as a means to an end. When you buy meat, you are financing the intentional slaughter of an innocent being for your sensory pleasure. Crop deaths, on the other hand, are an unintended, incidental byproduct of food production. In a duty-based framework, the moral gulf between an accidental byproduct (harvest deaths) and a deliberate, systematic execution (slaughter) is absolute. By participating in intentional slaughter, you are violating a core deontological principle.

​You claim that trying to include animals in deontology is bullshit because they aren’t rational human agents. But human infants, individuals with severe cognitive disabilities, and patients in advanced dementia also lack traditional rational moral agency. Yet, as a deontologist, you would agree it is a horrific violation of duty to slaughter and eat them.

​If you protect non-rational humans under your framework but exclude animals who possess the exact same capacity to suffer, feel pain, and experience life, your boundary isn’t rational agency’l at all. It is just arbitrary speciesism.