HISTOLOGICAL FEATURES OF RESPIRATORY EPITHELIUM OF CALVES HELD AT DIFFERING TEMPERATURE AND HUMIDITY

Abstract

The effect of ambient temperature and humidity on the structure of respiratory epithelium of calves was studied. Four calves of each of 3 experiments were acclimatized to a nonoperational environmental chamber for 6 days and then exposed to constant extremes of temperature and relative humidity (30.degree. C, 35%; 27.degree. C, 92%; or 5.degree. C, 92%) in this chamber for 8 days each. Five calves (3 and 2) were similarly acclimatized then exposed to 1.degree. C, 40%. Nasal swabs were taken from all animals at regular intervals. Swabs of 3 animals yielded Mycoplasma spp. and 1 swab yielded infectious bovine rhinotracheitis virus. Detailed histological studies of respiratory epithelium of nose, trachea, major bronchus and terminal bronchioli were conducted at 4 sites. Goblet cells were least in calves held in hot and dry air; calves held in dry air had the least polymorphonuclear cells and the greatest prevalence of hypochromatic cell layers and vacuolation of epithelial cells. Differences between experiments were evident most for sites of trachea and major bronchus.