George A. Everett

Dietary zinc deprivation affects parturition and outcome of pregnancy in the ewe

Abstract Low Zn intake by the pregnant rat and pig results in prolonged gestation and difficult delivery whereas in the guinea pig and ewe premature delivery occurs without unusual stress. Less stressful delivery may be related to the ability to maintain pregnancy without the ovary, a characteristic of the human; or it may be due to the small size of premature fetuses. To determine whether difficult parturition would result if a full-size fetus were delivered at term, 14 ewes were given a low Zn diet for the last half of pregnancy. Each restricted-intake ewe (+ZnRI) received Zn-supplemented drinking water and diet proportional to that eaten by a weight-matched unsupplemented ad libitum-fed ewe (ZnD). One ZnD ewe delivered day 143; the remaining ewes delivered at term (approximately 150 days). Two of 5 ZnD single lambs survived compared to 3 of 3 +ZnRI. One of 4 ZnD twin lambs survived compared to 3 of 8 +ZnRI. Problems of ZnD included prolonged labor, pregnancy toxemia, meconium in airways, and retained placentas. Activities of plasma angiotensin-converting enzyme and α -D-mannosidase with added Zn in vitro were significantly greater in ZnD and may be useful as indicators of Zn status.

The guinea pig as a model for effects of maternal nutrition on pregnancy outcome

Abstract The guinea pig has several characteristics which make it a useful model for the effects of nutrition on reproduction, but the nutrient requirements of the pregnant guinea pig have received little study. Since, in our experience, diets that support good growth in young animals may not be adequate for pregnancy, we compared the outcome of pregnancy in guinea pigs fed a purified diet (Cas) with that of animals fed a commercial “natural foods” diet (Com). To determine the effects of decreased feed intake which frequently accompanies nutritional deficiencies, the diets were fed either ad libitum (AL) throughout pregnancy or at a restricted level (RI) during the last half. Feed restriction was increased from 20 to 50% to mimic the effect of an animals becoming increasingly deficient. Females fed the two diets did not differ in weight gain during pregnancy, number per litter, or birth weight of the pups. ComAL had a larger percentage of young born alive than did CasAL and better survival of the young. All CasRI and two-thirds of ComRI delivered one to two weeks before term. Comparison of the purified diet with other purified diets and with the Recommended Nutrient Allowances suggested that while adding arginine and additional calcium to the diet might help females with reduced feed intake, some other factor is probably responsible for the differences in survival of neonates of ad libitum-fed females. Nonetheless, the purified diet can be used satisfactorily for studies of the effects of maternal nutrition on pregnancy outcome.