Digestive enzymes in the germ-free animal

Abstract

Summary.The digestive physiology of the germ-free animal has a number of characteristics (cecal hypertrophy, slower small intestine cell renewal, slower gastric emptying and intestinal transit) which distinguish it from that of the conventional animal. If the germ-free model is to be used to determine the role of gastrointestinal microflora in the nutrition of the conventional animal, it is essential to complete the study of these characteristics by data on digestive enzymes in the germ-free. The present paper analyzes these data.There In general, the germ-free animal has some characteristics which should permit better utilization of the diet ingested. Measurements of apparent digestibility do not confirm this hypothesis since results obtained in germ-free and conventional animals of the same species are contradictory.The germ-free animal is certainly a very useful tool for studying the role of gastrointestinal microflora in the nutrition of its host. The large intestine contains the largest bacterial population (1 to 3.10 10 bacteria/g fresh contents) and the greatest number of microbial species in the gut (Ducluzeau and Raibaud, 1975 ;Schaedler, 1973). In some cases, bacteria may efficiently intervene in the digestive utilization of the diet ingested by the animal (R6rat, 1978).However, a number of experiments in the germ-free animal have shown that it cannot be considered simply as a conventional animal, deprived of gastrointestinal microflora, since certain characteristics of its digestive physiology distinguish it from the conventional animal (see reviews by Gordon et al.,1966 ;Combe et al., 1976). A knowledge of these characteristics is essential when determining the part due to bacteria in the digestion of an ingested diet.The germ-free state in rodents and lagormorphs leads to a substantial increase in cecal sac contents and size (Glimstedt, 1936 ;Wostmann and Bruckner-Kardoss, 1959 ;Wostmann, Bruckner-Kardoss and Knight, 1968 ;Pleasants, 1959 (Guenet et al., 1970). In the chicken, the rate of epithelial cell migration is lower in the germ-free than in the conventional state, but the relative differences are greater in the lower than in the upper intestine (Rolls, Turvey and Coates, 1978).Gastric emptying and small intestinal transit of the ingested food were found to be slower in the germ-free than in the conventional state. Six hours after a labelled test-meal, the cecum of the germ-free mouse retained a greater percentage of radioactivity than the cecum of the conventional animal, and the passage of the marker into the feces was slower (Abrams and Bishop, 1967). Gastrointestinal transit was also slower in the germ-free than in the conventional rat (Sacquet, Garnier and Raibaud, 1970 ;Riottot et al., 1980), and tended to be longer in germ-free rats fed irradiated diets than in those fed autoclaved diets (Riottot et al.,1980). The aim of the present review is to complete our knowledge of the characteristics of germ-free animal digestive physiology by analyzing data on digestive enzymes. These enzymes (p...

Incorporation of galactomannans in the diet of newly weaned piglets: Effect on bacteriological and some morphological characteristics of the small intestine

“…It has been proposed that the underlying mechanisms for the growth promoting effect of antibiotics are related to interventions in the gastrointestinal tract and more particular in the small intestine, at the bacteriological, physiological and immunological level (Visek 1978, Vervaeke et al 1979, Corring et al 1981, Anderson et al 1999, Hillman 2001, Verstegen & Williams 2002, Gaskins et al 2002. Based on these considerations, several substances as possible alternatives for nutritional antibiotics have been put forward: probiotics, non-digestible oligosaccharides (NDO) with or without prebiotic properties, organic acids, enzymes (proteases, NSP-ases), herbs, bacteriocins, antimicrobial peptides and bacteriophages (Partanen & Mroz 1999, Hillman 2001, Dierick et al 2002Reid & Friendship 2002, Verstegen & Williams 2002, Joerger 2003, Ricke 2003, Montagne et al 2003.…”

The Genetic Background Is Shaping Cecal Enlargement in the Absence of Intestinal Microbiota

“…The large intestine of GF mice contains increased levels of digestive enzymes, the accumulation of which could also be responsible for the cecal dilatation [ 35 ]. Thus, we hypothesized that GF C3H mice in comparison with GF B6J mice show decreased levels of digestive enzymes.…”

Comparative biology of germ-free and conventional poultry

“…Interestingly, urinary ammonia dropped when sodium bicarbonate was included in the feed suggesting that acid:base balance may influence volatility of N in poultry waste streams. Corring et al (1981) reported that pancreatic and gastric output is similar in GF and CV animals but the absence of a microbiome in GF animals increases the persistency of endogenous enzyme activity in the intestine and loss of endogenous N from the gut. In CV animals more of the host-derived N is metabolized by bacteria and then either absorbed by the host where it is used to synthesize nonessential amino acids or is converted into microbial biomass.…”

“…These microbiome-related differences are particularly important for retention of unsaturated fatty acids such as palmitic and stearic whereas unsaturated fatty acids such as oleic or linoleic are less affected. Corring et al (1981) reported that bacterial hydrolases can split the bond between bile salts and taurine and glycine which is why GF animals have more primary, unmodified bile salts in the intestinal tract. Liver bile biosynthesis in GF animals is also lower than in CV animals and GF animals also have lower rates of catabolism of hepatic cholesterol, which explains the higher liver fat concentration in GF animals ( Furuse and Yokota, 1984a ).…”

“…However, GF chicken research was not widely used until the pioneering research of Reyniers and colleagues from the University of Notre Dame ( Reyniers et al, 1950 ). Subsequently, the GF chick model has been used extensively to explore the mode of action of antibiotics ( Forbes and Park, 1959 ; Coates et al, 1963 ), nutrient digestion and absorption ( Edwards and Boyd, 1963 ; Boyd and Edwards, 1967 ; Campbell et al, 1983 ), coccidiosis ( Radharkrishnan and Bradley, 1973 ; Gaboriaud et al, 2021 ), gastrointestinal development ( Cook and Bird, 1973 ; Ford, 1974 ; Corring et al, 1981 ; Philips and Fuller, 1983 ; Furuse and Yokota, 1984a ; Furuse and Okumura, 1994 ), protein metabolism ( Salter and Coates, 1971 ; Salter et al, 1974 ; Coates et al, 1977 ; Okumura et al, 1978 ; Furuse and Yokota, 1985 ; Furuse et al, 1985 ; Muramatsu et al, 1985 ; Muramatsu et al, 1987 ; Yokota et al 1989 ; Muramatsu et al, 1993b ), metabolic rate ( Harrison and Hewitt, 1978 ; Muramatsu et al, 1988 ), energy metabolism ( Coates et al, 1981 ; Hedge et al, 1982 ; Furuse et al, 1991b , c ; Muramatsu et al, 1992 ) and feed additive efficacy ( Furuse et al, 1991a ; Muramatsu et al, 1993a ; Langhout et al, 2000 ; Drew et al, 2003 ; Cheled-Shoval et al, 2014 ). The entire body of work from 1950 to 2022 (approximately 40 independent studies) on germ-free chickens gives considerable insight into the role of the microbiome in development of the intestine and support organs, the ability of the chick to extract nutrients from the feed, development of immune function, retention of protein and nonprotein nitrogen ( N ), energy metabolism, metabolic rate, and disease resilience.…”