Evaluation of a rosette inhibition test for pregnancy diagnosis in pigs

A rosette inhibition test was developed using pig lymphocytes and sheep red blood cells. Antilymphocyte serum (ALS) in the presence of complement inhibited rosette formation by greater than 95% at 1/250 declining to no inhibition at 1/8000. Sera obtained from a total of 14 pregnant sows before and 1, 2, 3 and 4 wk after mating were tested for their ability to augment the rosette depression caused by ALS. In one experiment in which the responses of 4 pregnant sows were compared to 4 non-pregnant sows by discriminant analysis, sera were classified correctly in 83% of the samples taken from either pregnant or non-pregnant sows. When the more usual method of calculating the rosette inhibition titre was used, the responses of sera from pregnant pigs were classified with 31% accuracy and those from non-pregnant pigs with 80% accuracy. In a second experiment, sera from 10 pregnant sows were classified with 25% accuracy using the rosette inhibition titre. Thus 4 of these pigs were classified as non-pregnant by this method. Data from the second experiment were not suitable for discriminant analysis. It was concluded that there was some factor present in the sera of pregnant pigs, particularly by 3 or 4 wk post-mating, which could be detected by the rosette inhibition test. However, the test is not sensitive enough to allow specific diagnosis of early pregnancy in pigs.