M. C. Nesheim

The digestion of heat-damaged protein

I. The apparent digestibilities for chicks, operated on so as to allow separate collection of urine and faeces, of the nitrogen in a heat-damaged cod flour (C35) and of a control, freezedried cod muscle (Cz3) were 77 and 90 yo respectively. 2. The differences are similar to those found for rats in earlier work and considerably smaller than the differences found in nutritional value of the materials as sources of either lysine or methionine for chicks. 3. Chicks killed 3 h after a test meal containing C23 showed little more N in their small intestine than did those on a N-free diet; other chicks receiving C35 showed much more N remaining in the gut. 4. It is hypothesized that significant quantities of heat-damaged protein may remain undigested in the small intestine, but may then be de-aminated by fermentation in the caecum so that values for the digestibility of N and of individual amino acids may be misleadingly high. 5. This hypothesis is supported by the finding that in caecectomized chicks the apparent digestibility of the N of C35 was only 68 %, whereas the digestibility of Cz3 remained the same as in intact chicks.

Ascaris suum: Nutrient absorption, growth, and intestinal pathology in young pigs experimentally infected with 15-day-old larvae

Abstract Three-week-old pigs on high (HP) or low (LP) protein diets were infected with 15-day-old Ascaris suum larvae (W). Including noninfected pigs (C), the experimental groups were HPW, LPW, HPC, and LPC. After 8 weeks, worm burden in the intestine averaged 42 in LPW and 31 in HPW. Nitrogen balance during Week 4 showed nonsignificantly less nitrogen absorption and retention in LPW compared to LPC. A similar, nonsignificant decrease in fat absorption was recorded in LPW vs LPC and in HPW vs HPC. The weight of the small intestine was significantly greater in W than C pigs but did not differ because of protein level. The weight correlated positively to worm burden and the increase was due mainly to hypertrophy of the tunica muscularis (muscle layers).

Haemoglobin concentrations and concomitant infections of hookworm and Trichuris trichiura in Panamanian primary schoolchildren

The blood haemoglobin concentrations and intestinal helminth infections were surveyed in 658 children aged between 6 and 12 years attending 4 primary schools in Coclé Province, Panama, in November 1987. 147 (22.3%) of the children were judged to have haemoglobin concentrations indicative of iron-deficiency anaemia. Blood haemoglobin concentrations were significantly lower in children with heavier Trichuris trichiura infections (> 5000 eggs/g) (P = 0.014), and in children with dual infections of both hookworm and T. trichiura (P = 0.005). Children with concomitant T. trichiura and hookworm infections were also significantly more likely to have blood haemoglobin levels indicative of anaemia than children who were uninfected or had single infections with either of these helminths (P < 0.005). In a longitudinal study involving 171 children selected from the original 658, blood haemoglobin concentrations were measured again in November 1988. Children who were considered to show an improvement in both hookworm and T. trichiura infections over this 12 month period showed a significantly greater increase in blood haemoglobin concentrations than children who had remained uninfected with either of these helminths throughout the study period (P < 0.05).

Intestinal helminthiases in relation to the socioeconomic environment of Panamanian children.

A cross-sectional investigation was made into ascariasis and nutritional status in Panamanian preschool children from October 1983 to July 1984. Within this framework, an analysis was undertaken of possible relationships between a range of intestinal helminthiases and the socioeconomic status of the participants. Attention was paid to caregivers education, parental occupation, family earnings, quality of housing and sanitation in the assessment of socioeconomic status. On this basis, strong associations were established between the socioeconomic status of the children and infection with Ascaris lumbricoides, Trichuris trichiura and hookworm. In general, the prevalence of single and multiple helminth infections was significantly higher in children living in housing made of wood or bamboo than in those living in housing made of concrete blocks. The same pattern applied to levels of sanitation. Ascaris lumbricoides occurred more frequently in children of mothers with the least formal education and in children living in relatively crowded conditions. Evidence was also obtained to indicate that the intensity of the intestinal helminth infections was greater in the children from the poorer environment. Since children from poorer socioeconomic conditions might be more exposed to infective stages than those from a better environment, the possible role of socioeconomic factors in contributing to the predisposition of some individuals to harbour large worm burdens of intestinal helminths was briefly discussed.

Nutritional aspects of Ascaris infection in young protein-deficient pigs

Experiments were carried out to investigate the effects of Ascaris suum infection on the growth, food intake, nitrogen and fat utilization and intestinal function of young pigs receiving diets low in protein. An infection procedure was developed which provided relatively uniform and heavy infections in pigs under study. Ascaris -infected pigs showed statistically significant reduction in growth rate and food intake compared to uninfected controls. The reduction in growth rate was observed after the A. suum were mature and eggs were observed in the faeces of pigs. The degree of growth retardation was significantly correlated with worm burden. Infected pigs showed no consistent reduction in nitrogen and total solids digestibility compared to controls but fat digestion was reduced. The infected pigs showed reduced nitrogen retention compared to uninfected controls. Ascaris -infected pigs had heavier intestinal tracts with increased size of the tunica muscularis . Lactase activity in mucosa from infected pigs was significantly lower than in controls, whereas no consistent effect was observed in mucosal sucrase and maltase activity. When Ascaris -infected pigs were given an oral lactose load, blood glucose levels rose less than in control pigs, suggesting that the infection resulted in impaired lactose tolerance.

The potential for grass-fed livestock: resource constraints.

Using pasture and grazed forest-range for a system of producing live-stock by feeding grass alone reduces the inputs of energy about 60 percent and land resources about 8 percent, but also reduces by about half the production of animal protein in the United States. Under a system in which only grass was fed, livestock would be restricted to beef, milk, and lamb production. The amount of grain fed to U.S. livestock is about 135 million tons (metric) or about ten times the amount consumed by the U.S. population.

Dietary requirements for essential branched-chain amino acids by lake trout

Abstract In a 12-week growth study of the dietary requirements of young lake trout Salvelinus namaycush for essential branched-chain amino acids, the leucine requirement was between 2.74 and 3.66%, and the isoleucine requirement between 1.54 and 2.06%, of dietary protein (as-fed basis). These ranges are substantially lower than those published and widely used in formulation of salmonid feeds. On the basis of both growth criteria and concentration of free amino acids in blood plasma, the valine requirement was within the range of 1.77 to 2.23% of dietary protein. The upper value of this range is substantially lower than the requirement reported for chinook salmon Oncorhynchus tshawytscha. Plasma valine concentrations in lake trout responded to dietary supplements of valine above the requirement level; the concentrations increased sharply once the requirement was exceeded. This finding is similar to observations recorded in other animals. Received February 4, 1983 Accepted August 7, 1983

Dietary Relations between Moniliformis (Acanthocephala) and Laboratory Rats

Aspects of the course of infection of Moniliformis dubius in male rats fed on four purified, isocaloric diets (A, B, C and D) were investigated. Diet A contained no digestible carbohydrate, diet B contained glycerol as a potential source of glucose, diet C contained 3.6 % starch and diet D contained about 59 % starch. After a rat had been adapted to one of the diets, it was infected orally with 20 cystacanths of Moniliformis and allowed to continue feeding on the same diet for periods varying from 1 to 18 weeks. A group of 4 rats was studied in this way on each of the diets for 11 weeks and on diets C and D for a further 7 weeks. The effects of the dietary treatments on the rats were studied by measuring their food intake, growth rate and liver glycogen. At the end of each experimental period, the rats were killed and the numbers, location, dry masses and state of reproduction of the worms were recorded. The composition of the diet appeared to have no effect on the establishment of Moniliformis in the small intestine and the populations of worms emigrated against the direction of gastrointestinal flow during the first month of the course of infection irrespective of the diet of the host. Worms from the rats fed on diets A and B hardly grew, their survival in their hosts did not appear to continue after 11 weeks and they showed no evidence of reproductive activity. Worms from rats fed on the low starch diet (C) did not grow as rapidly as those from rats fed on the high starch diet (D) during the first few weeks of the infection, but eventually they grew much larger and lived longer than worms from the hosts feeding on the high starch diet. Worms in the rats fed on diet C appeared to remain in a precise location in the anterior part of the small intestine from 4 weeks after infection of the host until the end of the experimental period. Worms in the rats fed on diet D had begun to move posteriorly in the small intestine from about 7 weeks after the infection of the host. The results of an experiment involving the transfer of rats with established infections of Moniliformis from a standard laboratory diet to diets A, B, C and D supported the conclusion that the survival, growth and reproduction of Moniliformis are dependent on the availability of glucose liberated during digestion in the host. Another experiment demonstrated that Moniliformis can survive periods of at least 14 days during which the host is deprived of an essential amino acid.

What is the research base for the use of dietary supplements

The market for dietary supplements in the USA was estimated as about 11.8 billion dollars in 1997 with a growth rate of 10-14% projected in the next 3 years. Data from the Food and Drug Administration collected in 1995 indicate that over 55% of adults surveyed used some type of dietary supplement. The marketing of dietary supplements in the USA has been essentially deregulated by the passage of the Dietary Supplement Health and Education Act of 1994 (DSHEA). This legislation defined dietary supplements, made manufacturers responsible for the safety of supplements and allowed certain statements of nutrition support to be made on supplement labels. The US Congress in passing the DSHEA indicated that supplements should be available on the market so that consumers could make decisions about their use for themselves and their families. Unfortunately, information about the research base for supplement claims is not readily accessible to health professionals and consumers. There is a need for authoritative reviews of the data underlying supplement claims to assist public health professionals in their role of providing advice to the public about dietary supplements.

Host-Parasite Relationships in the Alimentary Tract of Domestic Birds

Publisher Summary This chapter discusses host–parasite relationships in the alimentary tract of domestic birds. The functioning of the digestive system justifies assigning the status of a habitat to the alimentary tract and, therefore, that of a community to the organisms living therein. The chapter presents the aspects of the nutrition of domestic birds, including chemical nutrients, energy requirements, and nature of diet. The results of studies on the distribution, process of infection, and nutrition of organisms living in the alimentary tract of domestic birds have demonstrated, in a relatively superficial manner, something of the complexity of the various host–parasite relationships. Many parasites are dependent on the digestive physiology of their hosts, and some of the inhabitants of the tract also appear to be dependent on the activities of others, although it is not clear whether this dependence is direct or mediated through the host or some other environmental factor. The nature of the alimentary tract as an environment needs further investigation, and more studies should be undertaken to discover how the digestive physiology of the host, and the intraluminal conditions of the tract are affected by dietary changes and by parasites. Information of this type will facilitate both the design of experimental studies of host–parasite relationships and the in vitro cultivation of protozoan and metazoan parasites under chemically defined conditions. Satisfactory methods for in vitro cultivation are a prerequisite of the direct nutritional studies of parasites.