Season variations in the blood picture of white fulani calves naturally exposed to helminthiasis

Measurements of the red cell values of Nigerian white fulani calves 0–12 months old naturally exposed to helminthiasis were carried out during three periods of the year— early rainy season (May), late rainy season (October) and late dry season (March). The lowest values (overall mean PCV, 28.9 ± 5.7%) were recorded in the late rainy season when helminth egg counts were highest, and the highest values (35.8 ± 7.1) were recorded in the early rainy season when egg counts were moderate but nutritional values of pasture were very high. Although dry season egg counts were the lowest, the red cell values were just within normal limits at this time (31.9 ± 3.6) probably as a result of the low plane of nutrition at this time. The PCV values of calves 0–3 months old were always higher than those between 3–12 months.Treatment with pyrantel tartarate always reduced helminth egg counts (except for Strongyloides sp. in calves 0–3 months old); while this was more effective in the dry season than in the early rainy season, the improvement of blood values was more pronounced in the latter period.These results indicate that the low haematological values previously reported for African cattle could not be an inherited characteristic, but is rather due to the seasonal effects of parasitism and nutrition inherent in the indigenous husbandry practices. Establishment of ‘normal’ haematological values of these animals demands that these deleterious factors be removed.