Forty years of achievement in French research on digestive physiology in the pig.

The contribution of the research group set up by Rérat in the early 1960s in Jouy-en-Josas, and then expanded to Rennes, is summarised. As digestive processes are a major key to the nutritional status of monogastric animals, original methodologies based on advanced experimental surgery were developed in the pig to quantify the digestion and absorption yield, to know their factors of variation, and to understand their physiological and nutritional consequences. The group also extended its expertise to the control of food intake, the role of the nervous system and regulatory peptides, and several biomedical gut-related topics.

Effect of the source of dietary fat on postweaning lipogenesis in lean and fat pigs.

Twenty-four male piglets weaned after 21 days, 12 of the Large White lean breed (LW) and 12 of the Alentejano fat breed (AL), have been used to compare the effects of genotype and source of dietary fat on the activities of enzymes involved in lipogenesis and on the composition of selected fatty tissues. During 4 weeks the piglets were fed isoenergetic and isonitrogenous experimental diets, containing 5 % of either olive oil or tallow. In AL piglets the acetylcoenzyme A carboxylase activity was three- and ninefold higher, the malic enzyme activity six- and fivefold, and the glucose-6-phosphate dehydrogenase activity was four- and fivefold higher in the dorsal subcutaneous and in the perirenal fat, respectively, than in LW piglets. In general, fatty tissues of the AL piglets contained a higher proportion of saturated fatty acids. Olive oil induced a significant increase in the activities of malic enzyme and glucose-6-phosphate dehydrogenase in both tissues, but only slightly increased the acetylcoenzyme A carboxylase activity in perirenal fatty tissues (p < 0.05). The fatty acid profile of the subcutaneous and of the perirenal fat was strongly affected by the composition of dietary fat. These observations showed that the source of dietary fat influenced markedly lipid metabolism and body composition since a very early age.

Diet modifies elastase I and II activities and mRNA levels during postnatal development and weaning in piglets.

Little information is available on the expression of pancreatic elastase I and II, despite their role in protein milk digestion. We studied the developmental changes and the effects of diet composition on both elastase I and II expression in suckled and weaned piglets. We measured their activities and levels of their corresponding mRNA. Forty-two piglets were assigned to seven groups according to age and diet. Piglets were slaughtered at birth (Group 1), or suckled up to 13 d (Group 2) or 21 d (Group 3), fed a milk substitute from 14 to 21 d (Group 4) or to 56 d (Group 7), suckled up to 21 d and then fed a dry starter up to 56 d (Group 5), or fed a milk substitute from 14 to 21 d and then a dry starter up to 56 d (Group 6). At 21 d pancreatic function was not modified by the source and the form of milk consumed. The specific activity of elastase II was maximum at birth and declined sharply thereafter, whereas that of elastase I markedly increased after weaning. The presence of milk protein in the diet did not prevent the sharp decrease in elastase II activity observed with age. During the 13 d period of suckling sow's milk, the mRNA patterns indicated that the regulation was at the mRNA and post-transcriptional levels, whereas after weaning and depending on the source of dietary protein, it was essentially translational and/or post-translational. Taken together, our results provide evidence of the early expression of elastase I and II genes that could enhance protein digestion. It seems that elastase II might be a predominant pancreatic protease during the milk-feeding period, whereas elastase I might be related to weaning.

Method of measurement of pancreatic elastase II activity and postnatal development of proteases in human duodenal juice and bovine and porcine pancreatic tissue.

A specific method for pancreatic elastase II activity analysis was developed. True elastase II activity could be discriminated from that of elastase I and chymotrypsin. The postnatal development of four pancreatic proteases in the duodenal juice of children and in the pancreatic homogenates of calves and piglets was measured. The study was carried out on patients without (14 children) and with (5 children) pancreatic insufficiency. Calves and piglets were either milk-fed or weaned until slaughter at different ages. Profiles of enzyme development were globally similar in milk-fed piglets and calves, while in children without pancreatic insufficiency, no significant change was observed between 4 and 168 months. In children with pancreatic insufficiency, enzyme activity was low. In animals, elastase II and chymotrypsin activities were maximal at birth, decreased with age, and probably were associated with the digestion of milk protein. In contrast, elastase I and trypsin activities increased markedly after weaning in connection with the intake of solid food.

[Characterization of the nutritional status of wild boars in forest surroundings on the basis of mesenteric fat and blood parameters]. / Caractérisation de l'état trophique du sanglier, en milieu forestier, à partir du gras mésentérique et des paramètres sanguins.

Blood samples as well as mesenteric fat for measurement of biochemical parameters were taken from 51 wild boars (36 males, 15 females) slaughtered over a period of one year. The relative weight of the mesenteric adipose tissue as well as its lipid content showed a maximum in the autumn and regularly decreased until the end of the next summer. The lipid content thus ranged from 39 to less than 10% at the end of the summer. Variations in the blood levels of some metabolites measured in the plasma were compared with the nutritional status of the animals. The values showed a high glycaemia (158 mg/dl) that varied little with the season. In contrast, the cholesterol level decreased from the autumn till late winter with a minimum value in March (89 to 50 mg/dl). The level of total proteins, which was low from February to September, increased during the autumn-winter period, independently of the albumin content which seemed to be constant. The urea content was highly variable thus masking possible seasonal variations. The creatinine level showed a minimum in the autumn (2.0 mg/dl) and a maximum in the summer (2.9 mg/dl), a period with little abundant food supplies. Thus, the wild boar exhibits large seasonal variations of its metabolism and constitutes body reserves which are mobilised during periods of reduced food availability. The mesenteric fat weight as well as the blood levels of cholesterol and creatinine seem to characterize rather well the nutritional status of this animal.

[Influence of the environmental temperature on the metabolic use of dietary energy and nitrogen in the growing rat]. / Influence de la température ambiante sur l'utilisation métabolique de l'énergie et de l'azote alimentaires chez le rat en croissance.

Sixty-seven male rats of the Wistar CF strain were used in two trials to study the effect of ambient temperature on nitrogen and energy balances (experiment 1) and on the variations of certain biochemical parameters of metabolism (experiment 2). In both cases, the rats, housed individually in metal cages and fed ad libitum, were kept under three different temperatures : 21 degrees C (control), 3 degrees C (cold), 31 degrees C (hot). Compared to the controls, the rats at 3 degrees C showed a significant increase (P less than 0.01) in food intake and a significant decrease (P less than 0.01) in daily growth rate and feed efficiency ratio; body fat content was unchanged. Compared to the controls, the rats at 31 degrees C showed a decrease (P less than 0.01) in food intake and growth rate, a better feed efficiency ratio (P less than 0.01) and a significant increase in carcass lipid content. When compared to rats at 21 degrees C, those at 3 degrees C had a much lower nitrogen retention; at 31 degrees C this retention was only slightly lower. The urinary nitrogen excretion, increased by the cold temperature, reflected higher nitrogen catabolism, while its increase at a high temperature was probably due to a decrease in protein synthesis, and a subsequent degradation of excess ingested nitrogen. Energy retention increased (P less than 0.01) as the ambient temperature increased from 3 to 31 degrees C, and wide variations in the amounts of fixed energy in the form of proteins or lipids were observed. The balance results obtained have been discussed in relation to the variations of some biochemical parameters of metabolism such as free fatty acids, free glycerol, lipoprotein-lipase activity and in vitro utilization of labelled glucose.

Improvement of piglet survival rate in relation to farrowing systems and conditions.

Two experiments were carried out in the same farrowing house with the aim of comparing the efficiency of two types of floors and in order to estimate the effect of bedding material on the performance of newborn piglets. In addition, the productivity data of our sow herd as well as those of the national herd, were analysed in order to study the effect of the farrowing system and piglet maturity at birth on the survival rate of the newborn. The main results clearly show the detrimental effect on piglet survival of using slatted floors at farrowing. Furthermore the mode of sow tethering during parturition directly affects the piglets losses between birth and weaning, i.e. 2.03 piglets/litter for tethered sows, 2.17 for caged sows, 2.30 piglets when using farrowing rails. Use of a bedding material has a positive influence on the survival rate: 83.1% for straw, 78.5% for shredded paper versus 68.5% in the case of an insulated concrete floor. Rearing of newborn piglets in a cold environment leads to a drop in the rectal temperature, a poor body carbohydrate utilization and a decrease in colostrum intake. This results in a poor immunity, a low survival rate and a growth rate depression. Search for optimal environmental conditions for the newborn piglet is more important than for the sow. An adequate management of farrowing houses is recommended involving tethering of the sows, extra heating of the pens when the piglets are born and during their first 3 weeks of life.

[Effect of yogurt ingestion on the intestinal lactase activity in axenic or holoxenic mice]. / Influence de l'ingestion de yogourt sur l'activité lactasique intestinale chez des souris axéniques ou holoxéniques.

Two sets of mice just weaned (germ-free or conventional) were fed ad libitum with three different diets: a 5% lactose solution, yogurt at a 3/5 dilution in this lactose solution, and heated yogurt at the same dilution in the same solution. Total lactase activity (TA) and specific lactase activity (SA) of the small intestine were measured after 14, 28 and 42 days of these diets. The results led to the following conclusions. 1) TA and SA were always significantly greater in germ-free and gnotobiotic animals than in conventional ones, whatever the diets and age of the animals. 2) TA and SA were significantly greater at the three times of measurement in the gnotobiotic and conventional animals fed with unheated yogurt than in the animals fed with heated yogurt. The 5% lactose solution gave intermediate results. 3) In conventional and gnotobiotic animals fed with yogurt, TA increased with time compared to the initial value at weaning. With the two other diets, TA remained constant or decreased. With yogurt, SA varied only weakly with time compared to weaning values, when it decreased in greater proportions with the two other diets.

Influence of birth prematurity on colostrum composition and subsequent immunity of piglets.

Two groups of seven pregnant sows were farrowing either naturally after 111-114 days of gestation or prematurely after 109 days following an injection of 125 micrograms/animal of a prostaglandin analogue. Colostrum intake was controlled individually on piglets during the first 24 h of life. Measurements of IgG, IgA and IgM were performed on 3 samples of colostrum after 0, 12 and 24 h following the birth of the first piglet, then in the serum of the piglets, sampled at 4, 12 and 42 days of age. Then, we calculated the total amount of Ig intake during the first 24 h of life and an estimation of the Ig stores of each piglet on the basis of weight, blood volume, and hematocrit at different ages. Results showed a marked average difference in the birth weight in favour of mature piglets as well as an increased colostrum intake: 315 vs an average of 213 g for premature piglets. Considerable variations between sows were found in the initial level of colostral IgG, independently of the gestation length. Two thirds of the IgG intake by piglets occurred during the first 12 h. Total Immunoglobulin intake in the first day was respectively 15.8 g vs 25.1 g for premature or mature piglets. Total estimated Ig content in the serum of 4 day-old piglets was also lower for premature ones (2.55 vs 3.2 g/animal), representing 10 to 27% of the total amount of Igs ingested during the first day of life.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of environmental temperature on heat production, energy retention, protein and fat gain in early weaned piglets.

1. Six experiments, each involving two groups of six piglets, were designed to study the influence of environmental temperature on heat production, energy retention and protein and fat gain in early weaned piglets. Immediately after weaning, at a mean age of 25 d, the animals were raised in two open circuit respiratory chambers. Each chamber was equipped with a totally wired cage. The piglets were paired-fed and maintained at environmental temperatures of 20, 24 or 28 degrees. Four replicates were used for each temperature. Metabolizable energy, heat production and nitrogen balance were measured during two consecutive periods (A and B), each of 6 d duration. 2. Heat production was higher at 20 degrees than at 24 and 28 degrees during periods A and B. Energy retention was negative during period A, it was positive during period B and increased with temperature. 3. Protein deposition was always positive and independent of environmental temperature. The net efficiency of protein utilization was 0.77. 4. Body fat was mobilized during period A at a higher rate at 20 degrees than 28 degrees. During period B, fat gain increased with increase in temperature. 5. The calculated ME requirement for maintenance amounted to 411 kJ/kg body-weight 0.75 per d at 28 degrees. 6. The critical temperature of early weaned piglets raised in intensive modern housing and fed at about 90% of the ad lib, intake is close to 28 degrees during the first 12 d after weaning.

Nutritional importance of colostrum in the piglet.

Suckling of colostrum by piglets is very important in order to improve the survival rate. Colostrum provides maternal antibodies, energy and protein. Rearing piglets suckling an artificial milk of a similar chemical composition to that of sow's milk failed when the animals were housed in conventional conditions although numerous research workers succeeded in rearing 90% of animals delivered and fed in sterile conditions. Studies on the chemical analysis of colostrum showed a high dry matter content (30-40% higher than that of milk) in particular a high protein level (twice that of milk). The high proportion of globulins, i.e. 38% during farrowing, drops to 12% of the protein 4 days later; conversely the casein content rather low at birth doubles over the same period. Colostrum proteins are not used to proved energetic nutrients; some of them are absorbed without hydrolysis and have a special physiological rôle. The transmission of maternal immunity by gamma globulins is well known; lactotransferrin plays an important rôle as a transporter and a bacteriostatic factor. Enzymatic proteins such as lyzozyme govern the metabolism of glycoproteins. Hydrolyzed albumins, casein and proteose-peptone fraction provide the essential amino acids for de novo protein synthesis. The fat content is relatively low during the first 24 hours and increases threefold in the 4 days after farrowing. It provides the majority of the energy required by the young animal. A high proportion of some fatty acids, mostly oleic and linoleic acids, are used preferentially as sources of energy. Other components, including enzymes of the mammary cells, were found, but their particular rôle has not been explained. Colostrum contains in addition numerous vitamins (vitamins A and E) and some particular trace elements (iodine and selenium), and their transfer from the maternal diet to the young is particularity efficient by colostrum suckling. The nutritional rôle of those nutrients is important and their levels could affect the survival rate of the piglets. Hypotheses concerning the digestion and absorption of nutrients and antibodies are summarized, and finally, recommendations are made for further research and for the minimum amount of colostrum required by each piglet for survival and efficient postnatal growth to be assessed.

Development of digestive enzymes in the piglet from birth to 8 weeks. II. Intestine and intestinal disaccharidases.

The changes with age of intestinal mucosa, protein, lactase, maltase and sucrase were followed in the piglet between day 105 of gestation and 8 weeks after birth. Lactase and maltase activities appeared during fetal life in the whole of the small intestine. Activity of sucrase was recorded after the 1st postnatal week. Lactase activity was high at birth and reached a maximum at 1 week (X 2.5); maltase activity which was low at birth increased to the 8th week (X 143). Activities of all enzymes were low in the duodenum; lactase was most active in the jejumum. Similar activities of maltase and sucrase were found in the two distal parts of the small intestine. Specific activity (related to protein content) of lactase reached a maximum at the end of the 1st week after birth and decreased afterwards. Specific maltase and sucrase activities were higher in the 2nd week, decreased between the 2nd and 4th week and increased afterwards (maltase) or decreased to the 6th--8th week (sucrase).

Development of digestive enzymes in the piglet from birth to 8 weeks. I. Pancreas and pancreatic enzymes.

The development of pancreatic tissue (fresh weight, total proteins, RNA and DNA) and of the level of pancreatic enzymes (trypsin, chymotrypsin, lipase and amylase) of the piglet has been followed from birth to the age of 8 weeks in 10 animals at each of 7 stages. There was an increase with age and body weight of the total fresh weight of the exocrine pancreas. From birth until 4 weeks the development of the pancreatic gland was due to hyperplasia; from the 4th week till the 8th week of age, it was due both to hyperplasia and hypertrophy. There was a specific period, at the age of 3--4 weeks, from which total enzymatic activities markedly increased. Furthermore, from the 4th week of age there was a rise in the intake of total dietary proteins, fat and carbohydrates, due to the intake of solid food.

[Influence of dietary lactose on the development of lactase activity in the digestive tract of the pig]. / Influence du lactose alimentaire su la développement de l'activité lactasique dans l'appareil digestif du porc.

Lactase activity has been measured in the pancreas, the small and large intestine of 79 pigs varying in age from 6-7 months. The endogenous enzyme level fluctuated along the small intestine but the activity did not vary according to the level of lactose fed in the diet either just after weaning or from 25 to 100 kg of live weight. Measurements performed in the content of the intestine showed that lactose could be digested by the enzymes of the microflora mostly active in the ileum, the caecum and the large intestine.