Clinical examination of weanling rats with early zinc deficiency.

In order to gain experience about the detection of adverse effects during a scientific procedure, we carried out a clinical examination of rats with zinc deficiency. In weanling rats fed a zinc-deficient diet (30 mumol zinc/kg) for 10 days, the mean tibial concentration of zinc was reduced by 53% and body weight gain by 73% when compared with rats fed a diet containing an adequate amount of zinc (150 mumol zinc/kg). In a small open field on day 9 of the experiment, the deficient rats more frequently displayed the posture standing upright with elevated heels. On day 10 of the experiment a clinical examination was carried out at random and 'blind' by three independent assessors. Out of 20 variables scored quantitatively on each individual animal, only body size differed between normal and deficient rats. Other classical signs of zinc deficiency, such as alopecia, dermatitis and diarrhoea, were not detected. It is concluded that in this rat model of zinc deficiency, no evidence for extreme discomfort can be demonstrated.