Which of the following is NOT a clinical sign of macadamia nut toxicity?

In the context of macadamia nut toxicity in dogs, abdominal pain is generally not a recognized clinical sign. The most common signs of macadamia nut poisoning include tremors, hyperthermia, lethargy, weakness, and ataxia.

Tremors can occur because the toxins in macadamia nuts affect the central nervous system. Hyperthermia may be observed as an increase in body temperature due to muscle activity or metabolic changes caused by the toxin. Lethargy is also a common symptom as affected animals may exhibit decreased activity and responsiveness.

While abdominal discomfort can occasionally be experienced by pets in various types of toxicities or gastrointestinal disturbances, in the specific case of macadamia nut toxicity, it is not a prominent or widely reported symptom, which distinguishes it from the other options that are clearly associated with this type of poisoning.