Copper deficiency in pregnant ewes: its influence on the course of pregnancy and the health status of the offspring

ABSTRACT

Swayback disease (SD) which affects young sheep and a number of other animals is caused by the unavailability of metabolizable copper during the last half of pregnancy. In an effort to increase the present understanding of the development of SD and related human disorders we induced copper deficiency in pregnant ewes and studied its effects on pregnancy and the offspring. Nineteen pregnant ewes were rendered copper deficient by injection of ammonium tetrathiomolybdate (ATM), at 1mg/Kg during (I)the last 8-11 weeks, (II)the last 4-6 weeks and (III)the last 1-2 weeks of pregnancy. Treatment was continued until the lambs were weaned and sacrificed. Atomic absorption spectroscopy revealed that prolonged ATM treatment causes unpredictable changes in serum copper levels in the pregnant ewes, varying from large increases of 133 percent to large decreases of 65 percent. An unusually high number of treated ewes (29 percent) died during pregnancy. Neonates from ewes of the 1-2 week treatment group had normal serum copper levels, while 86 percent of the lambs from the 4-8 week group displayed subclinical serum copper levels (<0.5 ppm). Lambs from ewes in the 8-11 week group had serum copper levels ranging from moderate, 0.6 ppm to very high, 3.4 ppm. Nine of the 22 offspring showed signs of SD none of these were from ewes receiving ATM treatment for the shortest period 44 percent of the lambs from the intermediate group and 63 percent of those from the group receiving the longest ATM treatment were diseased. We conclude that while copper deficiency occuring in the last two weeks of pregnancy appears to have no effect, acute deficiency occuring at earlier stages, particularly the last 8-11 weeks, is likely to precipitate swayback disease in the offspring. Finally, it has been suggested that the early postnatal development stage of the human, corresponds to the final prenatal stage of the lamb, the present findings therefore suggest that the human foetus might be susceptible to copper deficiency even during the final weeks of pregnancy (AU)