Intestinal Flora of the Pig as Influenced by Diet and Age

Studies have been conducted on the intestinal and rectal microorganisms of the pig to determine how they vary with diet, age, pre-experimental environment and management. The influences of diet and management were studied using 48 pigs weaned at two weeks of age and fed to 6 weeks of age, at which time half of the pigs were sacrificed and bacteriological examinations made on duodenal, ilial, cecal and rectal contents. The organisms studied were the total aerobes, total anaerobes, lactobacilli, coliforms, streptococci, staphylococci and molds and yeasts. With respect to gain and efficiency of feed utilization, lactose was far superior to raw corn starch, and individual feeding resulted in faster gains than group feeding. All rectal organisms, with the exception of the total anaerobes and lactobacilli, were lower in numbers when lactose, as compared with starch, was the carbohydrate fed. In each section of the intestinal tract sampled, the coliforms, streptococci, staphylococcus and molds and yeasts were also lower in numbers with lactose feeding. Counts of most organisms increased sharply from the duodenum to cecum and only slightly from the cecum to rectum. Pigs fed in groups of 6 generally had higher counts with less variation than those individually-fed. Also, a significant difference between litters was observed. The intestinal tract of the newborn pig is relatively devoid of microbial growth, but within 24 hours these populations reached their greatest density in terms of viable cells. Most of the organisms studied showed a general decline in numbers from one day of age up to weaning (2 weeks of age), at which time they increased in numbers to a level just below that attained at one day of age. The counts then remained fairly stable to market weight. The coliforms, however, seem to follow a general tendency to decline in numbers from one day of age to market weight. Of the groups of organisms studied, the lactobacilli generally predominated in numbers, with the streptococci, coliforms, staphylococci and molds and yeasts usually following in that order. These relationships were influenced to a certain extent by age and also by location in specific sections of the intestinal tract.