The influence of age and health status on the serum alpha 1-acid glycoprotein level of conventional and specific pathogen-free pigs.

Serum alpha-1-acid glycoprotein (alpha 1AG) was measured in 212 Landrace White pigs between birth and finishing age. The alpha 1AG level of healthy pigs five to ten months of age was 338 +/- 79 micrograms/mL, and the upper normal limit in mature swine has been established as 500 micrograms/mL. In both specific pathogen-free (SPF) and conventional pigs, the alpha 1AG level within one day of birth was 14,263 +/- 2,393 micrograms/mL, 40 times the normal adult value, but rapidly decreased to 699 +/- 186 micrograms/mL by four weeks of age. In conventional pigs, alpha 1AG began to increase after four weeks, averaged 1,428 micrograms/mL by eight weeks, but gradually decreased to adult levels by 20 weeks of age. In comparison, alpha 1AG of SPF pigs was only 800 micrograms/mL at eight weeks and decreased more rapidly to normal by 16 weeks of age. The conventional pigs had a high incidence of clinical pneumonia and specific antibodies to Actinobacillus pleuropneumoniae and Mycoplasma hyopneumoniae at the age of eight weeks. As the clinical pneumonia disappeared, serum alpha 1AG level also gradually declined. In contrast, SPF pigs had little clinical illness, low alpha 1AG, and little serological evidence of microbial infection. Conventional pigs with nonrespiratory infections, encephalitis, or with hernias had increased alpha 1AG. While the very high alpha 1AG level of the neonatal pig may be due to genetic influences, increases later in life are likely in response to stimuli from its external environment. Monitoring of serum alpha 1AG in several herds aided in the recognition of disease processes and may have potential use in swine herd health management.