A recent study by I'.wis et £;!. (ISiSO) indicated that B. 

 abortus can infect cs'tle and bison to the same degree. 

 Serologic tests only indicate presence of the antibody (i.e. 

 that the aniral has been exposed) ; it does not indicate 

 whether the animal actu=.lly can transmit and has symptoms of 

 the disease. According to Jubb et al. 1985... "Once infection 

 is established in sexually mature animals, females especially, 

 it tends to persist indefinitely. Some, perhaps many, animals 

 will recover completely, but which ones will, and when they 

 will, cannot be predicted." A significantly higher percentage 

 of males (61%) tested positive to the brucella antibody than 

 females (44%) (p<.05). This could be related to male 

 courtship behavior which exposes them to greater potential 

 contact with the organism. 



AGE STRUCTURE OF HARVESTED BISON 



Ages of harvested bison determined by the three 

 techniques used are shown in Table 4 and Fig. 2. 



A total of 131 teeth was submitted for cementum aging 

 (Appendices A and B) . Ages varied from 1 to 15 years, with a 

 mean age of 4.96 years. 



A total of 312 animals was aged in the field (Appendices 

 C and D) , Calves were included, giving a more complete 

 harvest age structure. However, the older age segment (>12 

 years old) was not represented, biasing the results toward a 

 younger age structure. 



The modified or assigned aging technique provided the 

 most comprehensive sample of the harvested population (Figs. 

 3 and 4) . This method provided an assigned age for 382 

 animals or 67% of the total harvest. 



The modified method was tested on individual animals that 

 were aged by both of the other techniques (n=59) using the 

 Wilcoxon's Signed Rank Test. Field and cementum methods did 

 not differ significantly (P>.05) when a half year was 

 subtracted from the cementum age (cementum age overestimated 

 field age by six months) . June 1 was assumed as the birth 

 date for bison by the laboratory conducting the cementum 

 aging. Age assignment was complicated by the fact that 

 calving can occur from nid April to early August. 



