EFFECT OF STRATEGIC GASTROINTESTINAL NEMATODE CONTROL ON GROWTH OF NDAMA CATTLE IN GAMBIA

From October 1989 to December 1994, a longitudinal study on the contro l of gastrointestinal nematodes was done on 1000 N'Dama cattle in 20 p rivate herds in Gambia. Each herd was divided into two groups with an even distribution of age and sex, One group received a single anthelmi ntic treatment of Fenbendazole, Panacur Hoechst Veterinar GmbH, 7.5 mg kg(-1) BW in October 1989, whereas the other group served as an untre ated control. In July 1990, the herds were subdivided into two differe nt treatment schemes, In the herds of the first scheme the treated ani mals (Treatment group I) were treated once (in August), whereas in the herds of the second scheme the treated animals (Treatment group II) w ere treated twice (in July and September). The same treatment schedule was used in the subsequent rainy seasons until December 1994. One gro up in every herd served as control (Treatment group 0) and received no anthelmintic treatment throughout the study, One annual fenbendazole treatment had no significant effect on liveweights, whereas two annual treatments significantly increased liveweights of the age group 12-24 and 24-36 months by 9.4%, and 17.5%, respectively, Animals less than 12 months old had 6.3% higher liveweights after two treatments, the di fference was statistically not significant (P < 0.06). Average weights of 3- and 4-year-old, twice-treated animals were 13.1% and 8.2%, resp ectively, higher compared with their controls. No effect of anthelmint hic treatment on liveweights was found in 5-year-old and older animals . Herd structure analysis demonstrated that overall male offtake rates ranged from 12 to 28% in the 3-, 4- and 5-year-old age categories. Th e age categories within which deworming improves liveweights thus coin cides with the age at which males are mainly sold. These results sugge st that biannual metaphylactic treatments (end of July and beginning o f September) of all animals from birth to an age of 4 years should be recommended, provided that the financial analysis demonstrates the pro fitability of this intervention.