Long-term stability of blood lymphocyte nuclear pocket prevalence in clinically normal adult dairy bulls.

A study on blood lymphocyte nuclear pocket (LNP) prevalence stability was made over a 2-year period on ten clinically normal adult Holstein-Friesian bulls. The design of the experiment included 3 categories of animals as follows: (a) 3 bovine leukosis virus (BLV)-seronegative bulls (N); (b) 4 BLV-seropositive bulls and initial low (less than 1.0%) blood LNP prevalence; and (c) 3 BLV-seropositive bulls with initial high (greater than or equal to 2.0%) blood LNP prevalence. Prevalences of LNP for individual animals in all three groups were stable as to category of initial designation during the 2-year period. All animals initially designated as seronegative or seropositive remained so throughout the experiment. Essentially, correspondence between LNP concentration and BLV serotiter was observed only in the seronegative group in which prevalence was low on all samples. Because increased LNP prevalence has been shown to be related to in vitro C-type BLV production and beacuse LNP prevalence appears to be stable, this measurement may be of discriminatory value in studies to develop criteria for the disposition of enzootic bovine leukosis seropositive cattle.