Hematologic values in hypothermic and rewarmed young calves.

Hematologic values were determined in cold-stressed and rewarmed 1- to 7-day-old Holstein bull calves. The animals were anesthetized and then cold-stressed by immersion in water until their core body temperature (colonic) had decreased by 10 C. They were kept at the hypothermic state for an additional 1 hour and then were rewarmed by 1 of 3 external rewarming methods or by natural (unassisted) recovery. Changes observed in the hematologic values of the cold-stressed calves during cooling represented a trend, rather than a direct effect of cold exposure because the values did not differ (P greater than 0.05) from those obtained from the noncold-stressed animals. Nevertheless, a linear decrease (P less than 0.05) in the total number of leukocytes was observed in the cold-stressed calves during cooling when compared with preimmersion values. The leukopenia resulted primarily from a neutropenia (P less than 0.05) and secondarily from decreases in the number of other leukocytes. Minor increases were noticed in the total number of erythrocytes, hemoglobin concentration, and PCV, whereas mean corpuscular values generally remained unchanged during cooling. A rapid and linear increase in the total number of leukocytes was noticed in all cold-stressed calves during recovery. The increase in total leukocytes occurred in all types of leukocytes and particularly in segmented and nonsegmented neutrophils.