The Perinatal Pig in Pediatric Gastroenterology

Immature intestinal development is a predisposing factor to enteric disease in the newborn. Hence, in the present study, the effects of colostrum and birth on the development of intestinal enzymes were investigated in the fetal and neonatal pig. In the first experiment, 30 fetal pigs from 10 litters (99 to 102 da of gestation; term = 114 ± 2 da) were prepared with chronic oesophageal and intravascular catheters. Through the oesophageal catheters, fetuses were infused with saline (n = 6), amniotic fluid (n = 8), milk whey (n = 6) or colostrum whey (n = 10) into the fetal stomach in utero, 4 times daily for 6 da. In a further 3 fetuses, the oesophagus was ligated to prevent the fetal gut from receiving any fluids. Blood gases, blood haemoglobin and plasma Cortisol values were measured to monitor the fetal well being in utero. At the end of the experiment, infused and ligated fetuses were removed by caesarean section and small intestine collected for enzyme analyses. Treatment did not affect sucrase or lactase activity but maltase, aminopeptidase and dipeptidylpeptidase IV activities were altered. Mean activities of these enzymes were highest in colostrum infused fetuses and lowest in ligated fetuses. Maltase and aminopeptidase A activities in the colostrum group were 100% higher than in the amniotic fluid group. In the second experiment, 73 newborn pigs from 6 litters were born either by caesarean section or by the vaginal route after induction of parturition with a prostaglandin analogue. Newborn pigs were born prematurely (106 to 108 da of gestation) or close to normal term (113 to 115 da of gestation); small intestine was collected for enzyme analyses at birth or after 2 da of colostrum feeding. Most enzyme activities were lower for newborn, premature piglets than term piglets. Vaginal birth inhibited sucrase activity and stimulated aminopeptidase A activity. For 2 da old pigs, vaginal birth was associated with increased activities of sucrase, lactase, aminopeptidase N and dipeptidylpeptidase IV. Consistent with findings in fetal pigs, colostrum feeding for 2 da induced a large (2 to 3 fold) increase in maltase and aminopeptidase A activities; whereas, the other enzyme activities were similar at birth and at 2 da of age. The fetal and neonatal pig is a useful model to investigate the effects of luminal factors (nutrients, hormones, growth factors) on immature intestine. In addition, time of birth (preterm or term), delivery type (caesarean section or induced vaginal birth) and diet (milk or colostrum) have pronounced effects on the development of intestinal function.