Reproduction and Early Postnatal Growth of Progeny in Swine Fed a Protein-free Diet during Gestation

Abstract

Studies were made to ascertain the effect of a “protein-free” diet containing 0.5% protein supplemented with vitamins and minerals on swine reproduction and subsequent growth and serum protein of their progeny. Litter size and individual pig birth weight were normal in gilts fed the all-corn diet. In experiment 1, gilts were introduced to dietary treatment before breeding; in experiment 2, 24 to 28 days after breeding. Two of three pregnant gilts fed the protein-free diet in experiment 1 died of perforated gastric ulcers on days 67 and 101 of gestation. The uterus of these 2 gilts contained, respectively, 10 and 11 grossly normal, viable fetuses at time of death. One gilt successfully completed gestation and farrowed 9 normal pigs averaging approximately 80% of the birth weight of pigs from control and all-corn fed gilts. When the protein-free diet was introduced on day 24 to 28 of pregnancy in experiment 2, body weight and total serum protein of pigs at birth were not significantly lower than those of pigs from control gilts. Milk production of gilts fed protein-free diets during pregnancy was adversely affected as indicated by the significantly lower 6-week body weight of their own and of pigs transferred to them at 2 days of age from control sows as compared with that of pigs nursing control sows of their own or from reciprocal transfer. Serum protein of pigs from gilts fed the protein-free diet was significantly lower than that of pigs from control gilts only at week 4. Pregnancy can apparently be maintained in the gilt deprived of dietary protein by dependence on maternal tissue stores of amino acids for growth of the fetus. Inception of the protein-free regimen at day 24 to 28 of pregnancy in the gilt appears to have far less adverse effect than inception before breeding. Part of this effect is probably related to the longer depletion period in the latter case, but the interruption of the estrous cycle in the absence of dietary protein seems to be a more immediate and specific endocrine effect.