Various species of animals, ranging from ordinary laboratory rats to some high-grade beef and dairy cattle, have been imported from the temperate regions of the world to Nigeria in recent years. Most favoured are Large White pigs and this breed of livestock is proving to have very great potential in the livestock production industry in this part of the tropics. Temperate breeds of livestock when introduced to the tropics are said to decline in their general performance, owing partly to direct effects of high ambient temperatures(Yousef & Johnson, 1965). Some generalized statements have also been made on the adverse effects of tropical climate on growth though very little objective field experimental evidence exists (Williamson & Payne, 1978).

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We have studied reports of new cases at 11 State Government Hospitals in the state of Borno, over a period of 9 years from 1976 to 1984. Urinary schistosomiasis was the second most common communicable disease, while intestinal schistosomiasis ranked sixth. The rise in prevalence of schistosomiasis since 1979 probably reflects increased public awareness of the beneficial role of hospitals. The decline in the number of cases seeking treatment in 1982 and 1983 may be due to the decline in rainfall and thus of agricultural and fishing activities involving contaminated irrigation ponds.

A total of 142 pigs, born at four different times of the year, were slaughtered between 1 and 9 months of age to study the effects of season of birth and sex on heart weight and body weight in the equatorial climate of southern Nigeria.Analysis of loge heart or body weight showed that season of birth influenced heart and body growth (P < 0·001). The differences occurred largely during the phase of rapid growth, with smaller differences at weaning and at 9 months. Pigs born during the high-rainfall period (May to September) showed stunted body and heart growth during the subsequent dry and warmer seasons. Those born during the dry seasons (November to March), but which passed their rapid-growth phase through the rainy, cooler seasons, were attaining market weights and adult heart weights earlier in life. However, all pigs with early growth reductions recovered, at least partially, later in life. The males had larger hearts at later ages than the females although the differences were not significant (P > 0·05). Allometric regression analyses for heart and body weight showed no seasonal effects but there was a small but significant sex effect (P < 0·001). The males had a smaller intercept and a larger slope when log, heart weight was fitted to log, body weight.Pigs reared in this equatorial climate appeared to have higher heart weights relative to body weights than those reared in temperate regions. The highest recorded proportional value of 0·0032 is outside the range of 0·0023 to 00028 recorded in temperate regions. This suggests a probable physiological adaptation to increased work load on the heart under warm tropical conditions.

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