Effect of chemotherapy on elevated ejaculation time and deteriorated semen characteristics consequent to trypanosomosis in zebu x Friesian crossbred bulls

The effect of the trypanocide Novidium® on elevated ejaculation time and deteriorated semen characteristics was studied in zebu x Friesian crossbred bulls infected with Trypanosoma vivax or T. congolense. The bulls were divided into three groups, A, B and C. Groups A and B comprised four bulls each, while group C had two bulls which served as control. Groups A and B were infected with 2 x 106 T. vivax or T. congolense, respectively, while group C served as uninfected control. Blood samples from treated bulls were all negative for trypanosomes four days postchemotherapy. The body temperature of the animals normalized. Clinical signs associated with trypanosomosis, such as anemia, cachexia and ruffled hair coat, disappeared gradually in treated bulls. There was only a marginal improvement in the semen characteristics of a bull infected with T. vivax at 24 weeks postchemotherapy. However, all bulls infected with T. vivax or T. congolense irrespective of chemotheraphy still had poor semen characteristics manifested by all or some of the following: decreased volume of semen, oligospermia, azoospermia and elevated incidence of sperm morphological abnormalities. They were thus unfit for breeding. T. congolense was more pathogenic than T. vivax in the study. Therefore, chronic trypanosomosis either due to T. vivax or T. congolense could be an important causative agent of infertility or sterility in zebu x Friesian crossbred bulls.