A.R. NJOGU, A.A. ISMAEL, R.B. DOLAN, G. OKECH, P.D. SAYER, EA. OPIYPO and H. ALUSHULA
Boran cattle (Bos indicus) originated from the highlands of Ethiopia and migrated with pastoralists South and East about 500 years ago. One group which settled in the tsetse-free Kenya Highlands has been selected over the last 100 years for growth and now forms the major beef breed in Kenya. A group of these animals was sent to Galana Ranch, in southeastern Kenya, in 1964 and are designated "Galana Boran". Other pastoralists migrated with Boran cattle to the tsetse-infested Tana River Delta of Kenya where they settled. These cattle have been selected for milk production and are known as the Tana-land Boran but for this study are designated the "Orma Boran". Studies by the Kenya Trypanosomiasis Research Institute (KETRI) on Galana ranch in 1980 indicated that the Orma Boran had a degree of resistance to African trypanosomiasis and further studies summarized below were carried out in the laboratory and in the field to compare it with that of the Galana Boran.
Under needle challenge with T. congolense and T. vivax the mortality of Orma Boran was about 20% compared with mortalities of 68 to 75% for the Galana Boran. Under fly challenge with T. congolense and T. vivax in the laboratory the mortality of the Orma Boran was 10-20% compared with 38-60% for the Galana Boran. Of the surviving animals, the PCV of the Orma Boran never dropped below 20% while that of the Galana Boran was generally lower. Under T. congolense challenge, 60% of the surviving Orma self-cured compared with 80% self-cure under T. vivax. None of Galana animals self-cured.
During the experiments in the laboratory, which lasted three months, the Orma Boran had a net gain in body weight while the Galana Boran had a net loss.
Studies in the field under medium-to-high tsetse fly challenge (medium challenge: 13.6 flies per unbaited biconical trap per day; high challenge: 36.9 flies per unbaited biconical trap per day) were carried out on steers and breeding herds of both Orma and Galana Borans. The two breeds were managed together. Results show that under medium challenge the Orma Boran experienced 0.6 infection per animal per annum compared with 1.5 infections for Galana. Under high tsetse challenge the Orma Boran experienced two infections per animal per annum compared to four infections per animal per annum in the Galana Boran. Generally the Galana Boran gained more weight under medium challenge and lost more weight under high challenge. The Galana Boran required more drug treatments than the Orma Boran leading to higher drug costs.
The breeding herds of Orma and Galana Borans were started in 1983. By the end of June 1987 the herds comprised 182 Orma and 162 Galana Boran. Selection is being carried out using packed cell volume and trypanosome susceptibility (number of infections per annum) as markers.
To date the Orma Boran have a mean calving interval of 514 days compared with 533 days for the Galana Boran. The mean birth and weaning weights for the Orma Boran are 18 and 105 kg, respectively and 21 and 137 kg respectively for the Galana Boran. The Orma Boran have a pre-weaning mortality of 8% compared to 17% for the Galana Boran. Analysis of the causes of pre-weaning deaths shows that 21% of the Orma were due to trypanosomiasis compared to 60% in the Galana Boran.
These studies indicate that the Orma Boran can be productive under tsetse challenge with minimum drug intervention. There have been reports both in Kenya and Sudan of other cattle breeds and strains being maintained under tsetse challenge. A survey should therefore be made to identify these breeds and strains demonstrating trypanotolerance with a view to utilizing them to develop more productive beef cattle for tsetse-infested areas.
