Sequential changes in erythrocyte volume distribution and microcytosis associated with iron deficiency in kittens.

Hemograms, erythrocyte volume distribution curves, serum iron and percent transferrin saturation determinations were done on samples from 50 kittens to characterize feline erythrocytic responses between one and ten weeks of age. At one week of age, all kittens had marked macrocytosis and anisocytosis. Most of the macrocytic cells no longer were present by five weeks. Macrocytes were replaced by erythrocytes of normal volume in 30% of the kittens. At five weeks of age, 70% of the kittens had produced microcytic cells which correlated with significantly lower packed cell volume values (p less than 0.02) and mean corpuscular volume values (p less than 0.001). By seven weeks of age, kittens with microcytosis were producing normocytic erythrocytes. Between two and four weeks of age, kittens with microcytosis had significantly lower serum iron and percent transferrin saturation values (p less than 0.01) compared to kittens without microcytosis. Between five and seven weeks of age, all kittens had very high iron values which were significantly greater than those of healthy adult cats (p less than 0.01). Six kittens with low iron values received an iron dextran injection at two to three weeks of age. At five weeks, these kittens had significantly greater mean corpuscular volumes, packed cell volumes (p less than 0.01) and lower percentage of microcytic cells (p less than 0.001) than littermate controls. These data demonstrate that transient microcytosis and anemia observed in kittens is attributable to iron deficiency. It also was demonstrated that erythrocyte volume distribution curves were more sensitive than the mean corpuscular volume in detecting microcytosis in kittens.