The gut capacity of mammalian herbivores increases linearly with body weight. This relationship, coupled with the change in basal metabolism with weight, produces an MR/GC ratio (metabolic requirement/gut capacity) that decreases with increasing body size. Since the retention of a food particle within the gut is proportional to this ratio, the extent to which food particles are digested will be related to body size. Plant material is made up of chemical components that react differently to digestive enzymes. The fiber fraction of plant material (i.e., cell wall) is digested slowly and exclusively by microbial symbiotes. A positive relationship probably exists between the fiber content of plant parts and their biomass in the environment. This relationship is used to describe a resource axis on which digestion rate is the scaling variable. In response to this resource axis and metabolic requirements, the fiber content of the diet of herbivores increases with body size. Ruminants are the predominant medium-s...

A Nutritional Explanation for Body-Size Patterns of Ruminant and Nonruminant Herbivores

A number of researchers have discussed the importance of the relationship of metabolism and gut capacity to body size to explain diet composition in animals that consume primarily plant material (Short 1963; Prins and Geelen 1971; Janis 1976; Parra 1978; Hanley 1980; Demment 1983). The kinetics of food-particle passage in the gut determines the digestibility of the diet and is dependent upon gut volume and food intake (Van Soest 1982). Gut volume is a constant proportion of body weight (Parra 1978; Demment 1982), while maintenance metabolism (a prime determinant of intake) is a fractional power of body weight (Kleiber 1975). Since these two factors influence retention times of food particles and hence affect the extent of digestion of the diet, body size has been considered as a possible mechanism for interspecific differences in diet (Bell 1970; Hanley and Hanley 1980; Sinclair 1977; Demment 1980; Van Soest 1982). In this paper, the relationship between body size and digestive capacity is used in conjunction with the relationship between abundance and quality of plant food to discuss the relative efficiencies of ruminant and nonruminant digestion at different body sizes. The relative efficiencies of digestion are used as a basis to explain the number of species of ruminant and nonruminant herbivores relative to body weight. While arguments are presented about physiological constraints on extant animal species, the principles discussed are considered as factors that have shaped the evolution of body size in these groups.

A nutritional explanation for body-size patterns of

Nutritional associations with bone loss during the menopausal transition: evidence of a beneficial effect of calcium, alcohol, and fruit and vegetable nutrients and of a detrimental effect of fatty acids

Calcium inhibits the damaging and compensatory proliferative effects of fatty acids on mouse colon epithelium.

Objective: This study investigated which aspect of energy balance was responsible for the decrease in body fat content of rats fed a high-calcium, high—dairy protein diet.



Research Methods and Procedures: Male Wistar rats were fed a control diet (25% kcal fat, 14% kcal protein from casein, 0.4% by weight calcium) or high-calcium diet (25% kcal fat, 7% kcal protein from nonfat dry milk, 7% kcal protein from casein, 2.4% calcium) for 85 days. Body weights, digestible energy intakes, energy expenditures, rectal temperatures, body composition, and serum glucose, insulin, free fatty acids, triglycerides, and 1, 25-dihydroxyvitamin D were measured.



Results: Rats fed high-calcium diet gained significantly less weight than controls and had 29% less carcass fat. Gross energy intake was not significantly different between groups, but digestible energy was 90% of gross energy in the high-calcium diet compared with 94% in the control diet because of increased fecal excretion of dietary lipid. The difference in digestible energy intake accounted for differences in carcass energy. Body temperatures and energy expenditures of the rats were not different. The high-calcium diet reduced serum triglycerides by 23% and serum 1, 25-dihydroxyvitamin D by 86%.



Discussion: These results confirm that a high-calcium diet decreases body weight and fat content due to a lower digestible energy intake caused by increased fecal lipid and a nonsignificant reduction in gross energy intake.

https://onlinelibrary.wiley.com/doi/pdf/10.1038/oby.2003.52

High Dietary Calcium Reduces Body Fat Content, Digestibility of Fat, and Serum Vitamin D in Rats

Interrelationship of Triglycerides with Calcium, Magnesium and Phosphorus in the Rat

Role of Coprophagy in Utilization of Triglycerides, Calcium, Magnesium and Phosphorus in the Rat

SummaryTracer study showed that 25% dietary triolein caused better absorption of calcium than 25% tripalmitin, 80% as compared to 50%. Including 4% L-phenylalanine in the diet, however, did not influence calcium absorption significantly, regardless of the nature of triglyceride.

Effects of Dietary Triolein, Tripalmitin, and L-Phenylalanine on Calcium Absorption in the Rat

SummaryIncreased fat asborption led to increased lymph, total serum, and L-phenylalanine-sensitive “intestinal” alkaline phosphatases activities. Triolein, which is almost completely absorbed, increased the activity of this enzyme, whether ftd alone or in combination with tristearin or tripalmitin. Dietary levels of calcium or phosphorus had no effect on the total serum or “intestinal” alkaline phosphatase activities of normal, growing rats.

Bahram Tadayyon

Papers

Interrelationship of Triglycerides with Calcium, Magnesium and Phosphorus in the Rat

Role of Coprophagy in Utilization of Triglycerides, Calcium, Magnesium and Phosphorus in the Rat

Effects of Dietary Triolein, Tripalmitin, and L-Phenylalanine on Calcium Absorption in the Rat

Effects of dietary fats, calcium, and phosphorus on rat serum alkaline phosphatases.