MaRGA Meeting, 2004: Abstracts

4: Nutrition

Effects of Energy Restriction on Gestation and Lactation

S. Tardif, D. Layne and D. Smucny

Affiliation: Southwest National Primate Research Center, San Antonio, TX

We report on the effects of energy restriction during gestation or lactation on maternal condition and reproductive outcomes. For all studies, females were restricted to 75% of expected ad lib energy consumption of a purified diet. Mid gestation restriction (day 66) reliably induced loss of pregnancy prior to term (mean delivery age = 92). Of the late (day 99) restricted pregnancies, 4 of 7 were normal term length while three were preterm deliveries, at 101, 117 and 132 days. Restriction reliably prevented the normal weight gains seen in control pregnancies. In late restricted females, higher daily weight loss was associated with earlier delivery age and females who began pregnancy at lower weights tended to have higher weight losses. Energy restriction during lactation for females of relatively high body weight did not, in and of itself, affect milk composition or infant growth rates - i.e., mothers did not sacrifice infant condition to protect their own reserves. Restricted mothers lost weight during lactation. The percent time spent nursing did not differ between energy restricted and control mothers, however the percent time that mothers carried infants while not nursing was lower for restricted females. Comparisons of maternal outcomes in the nonmanipulated population and in the energy restricted population both point to maternal weight loss during lactation as affecting not only maternal behavior but also milk output. These results suggest that maternal investment in lactation is affected by maternal condition in the most extreme cases (i.e., mothers with low reserves nursing the largest litter size). However, they also suggest that the impact of energy restriction upon reproductive function is strikingly different, dependent upon when in reproduction the restriction is imposed. Specifically, it appears that, as one might expect, the further along the female is in a given reproductive event, the more likely she is to continue to invest.