What term describes a decrease in red blood cells or hemoglobin concentration in the blood?

The term that describes a decrease in red blood cells or hemoglobin concentration in the blood is anemia. Anemia results from various factors, including blood loss, reduced red blood cell production, or increased red blood cell destruction. It is characterized by symptoms such as fatigue, weakness, and pale skin, which occur due to insufficient oxygen supply to the body's tissues.

Understanding anemia's significance in veterinary medicine is crucial, as it can indicate underlying health issues that require attention. Anemia can result from conditions such as nutritional deficiencies, chronic diseases, or parasitic infections, making it an important diagnostic consideration in clinical pathology.

The other terms relate to different blood component deficiencies: hemorrhage refers to blood loss; leukopenia indicates a decrease in white blood cells, which can compromise the immune system; thrombocytopenia signifies a low platelet count, affecting clotting ability. Therefore, in the context of the question, anemia is the correct choice as it specifically addresses the deficiency of red blood cells or hemoglobin concentration.