THE HETEROGENEITY OF BOVINE IGG2 .7. THE PHENOTYPIC DISTRIBUTION OF THE A1 AND A2 ALLOTYPES OF IGG2A AMONG BEEF-COWS WITH KNOWN CLINICAL HISTORY

Al and A2 are allotypes of bovine IgG2a which differ significantly in their primary structure, allotope expression and the products of pepsi n digestion. An analysis of 754 beef cows from 14 different breeds at the Meat Animal Research Center (MARC), Clay Center, NE, demonstrated a significant difference in the distribution of Al and A2 among breeds but failed to find any correlation between the clinical disease histo ry of the animals tested and their A-allotype. The proportion of all a nimals with either a history of infectious or respiratory disease (43. 3 +/- 3.5 and 17 +/- 0, respectively) was the same among A1/A1, A1/A2 and A2/A2 animals. Similarly, there was no preferential association be tween allotype and clinical disease within any one breed. A very high incidence of Al homozygotes was found among Angus (84%), Brown Swiss ( 100%), Limousin (87%), MARC I (87%) and Pinzgauers (88%). In contrast, Herefords had a high incidence of A2/A2 homozygotes (41%) as did Brah mans (46%) and Gelbveih (34%). The distribution of A1/A1, A1/A2 and A2 /A2 animals within any breed was totally consistent with the concept t hat Al and A2 represent Mendelian co-dominant alleles. These data sugg est that, among vaccinated female beef cattle in a normal environment, A-allotypy plays no role in the propensity for clinical disease as de fined in this study. It does not rule out such an association in non-v accinated, severely stressed animals and in calves exposed to severe o utbreaks of an infectious agent.