Effects of age and cold on pulmonary bacterial clearance in the young pig.

Young pigs (1, 6, 18, or 26 days of age) were exposed to an aerosol of a nonpathogenic strain of Escherichia coli and then held for a 3-hour clearance period in either a thermoneutral (32 C environmental temperature at 1 or 6 days of age, 24 C at 18 or 26 days of age) or a cold (6 C) environment. Pigs were then killed and pulmonary bacterial clearance was determined. There appeared to be an age dependent improvement in the capability of the pig to clear its lungs of the bacterial load. Cold appeared to inhibit pulmonary bacterial clearance, but this inhibitory effect became progressively less as the pigs became older. In a supplementary experiment conducted to assess the effect of age-within-litter (2 and 14 days of age) on pulmonary bacterial clearance, it was confirmed that young pigs were less able to clear nonpathogenic E coli from the lungs.