In addition to the bacteria in the rumen there are many larger (5–250/mm long) organisms which at various times have been designated protozoa Of these the ‘ovals’ (Quin’s and Eadie’s) are now known to be large bacteria (Orpin, 1976) and the ‘flagellates’ Neocallimastix frontalis, Piromonas communis and Sphaeromonas communis are the zoospores of phycomycete fungi (Orpin, 1977a, b) There are genuine flagellates in the rumen, eg Trichomonas spp, Monoceromonas sp and Chilomastix sp, but almost nothing is known about their metabolism (Jensen and Hammon, 1964) The largest, most obvious and most important protozoa are the ciliates, of which there are two groups both in the subclass Trichostomatia The so called ‘holotrich’ protozoa belong to the order Vestibuliferida and the entodiniomorphs to the order Entodiniomorphida, suborder Entodiniomorphina and family Ophryoscolecidae As the properties and metabolism of these two protozoal groups are different, they will be considered separately below

The Rumen Protozoa

Epidemiological studies have shown a positive relationship between dietary fat intake and obesity Since rats and mice show a similar relationship, they are considered an appropriate model for studying dietary obesity The present paper describes the history of using high-fat diets to induce obesity in animals, aims to clarify the consequences of changing the amount and type of dietary fats on weight gain, body composition and adipose tissue cellularity, and explores the contribution of genetics and sex, as well as the biochemical basis and the roles of hormones such as leptin, insulin and ghrelin in animal models of dietary obesity The major factors that contribute to dietary obesity - hyperphagia, energy density and post-ingestive effects of the dietary fat - are discussed Other factors that affect dietary obesity including feeding rhythmicity, social factors and stress are highlighted Finally, we comment on the reversibility of high-fat diet-induced obesity

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0954422410000168

High-fat diet-induced obesity in animal models

Influence of hydrogen on rumen methane formation and fermentation balances through microbial growth kinetics and fermentation thermodynamics

Glucose-dependent insulinotropic peptide (GIP) is a 42-amino acid peptide synthesized and secreted from endocrine cells in the small intestine. The role of GIP in coupling nutrient intake and insulin secretion, the incretin effect, is well known. We report that GIP receptor messenger RNA and protein are present in normal bone and osteoblast-like cell lines, and that high affinity receptors for GIP can be demonstrated by [125I]GIP binding studies. When applied to osteoblast-like cells (SaOS2), GIP stimulated increases in cellular cAMP content and intracellular calcium, with both responses being dose dependent. Moreover, administration of GIP results in elevated expression of collagen type I messenger RNA as well as an increase in alkaline phosphatase activity. Both of these effects reflect anabolic actions of presumptive osteoblasts. These results provide the first evidence that GIP receptors are present in bone and osteoblast-like cells and that GIP modulates the function of these cells.

Osteoblast-derived cells express functional glucose-dependent insulinotropic peptide receptors.

The urine-acidifying properties of food constituents depend on their content of non-oxidizable acids or precursors. Acidifying constituents such as animal proteins may negatively affect calcium metabolism and accelerate bone resorption, thus representing an aggravating factor for osteoporosis. This four-period, double-crossover study investigated whether a diet intervention specifically focused on acid load could modify calcium metabolism in humans. Eight healthy volunteers underwent a four-day metabolic preparation with two types of diets, one rich in acid ash-forming nutrients, and one providing base-forming nutrients (including bicarbonate-rich mineral water), both having similar contents of calcium, phosphate, sodium, proteins and calories. On the fourth day, a single oral dose of 1 g calcium was given, either as carbonate or as gluconolactate. Serial blood and urine samples revealed that the diet affected blood pH (average difference 0.014, p = 0.002) and urine pH (average difference 1.02, p<0.0001) in the expected direction, but had no influence on the absorption of the calcium supplement. The acid-forming diet increased urinary calcium excretion by 74% when compared with the base-forming diet (p<0.0001), both at baseline and after the oral calcium load, and C-telopeptide excretion by 19% (p = 0.01), suggesting a skeletal origin for the excess calcium output. This observation confirms that renally excreted acids derived from food influence calcium metabolism, and that alkalizing nutrients inhibit bone resorption. Further studies are needed to determine the clinical impact of dietary counseling for avoiding diet acids as a preventive measure against osteoporosis.

Diet acids and alkalis influence calcium retention in bone.

Influence of Protozoa upon Rumen Acid Production and Liveweight Gains in Lambs

An agent for bloat-prevention or -treatment which is useful for preventing or treating bloat caused by feeding large quantities of legume pasture or concentrate feed to ruminants comprises a mixture of a saccharide fatty acid ester and fatty acid salt.

Saccharide fatty acid ester for bloat-prevention or bloat-treatment

The present study was undertaken to investigate the effects of dietary medium and long chain triglycerides (MCT and LCT) on fat deposition and fatty acid composition of adipose tissues of rats. Twen-ty-seven Wistar strain male rats were divided into three groups and fed semisynthetic experimental diets: Basal (AIN 76), MCT (basal+C8:0 10%), LCT (basal+corn oil 10%). Feed intake was measured every day and body weight was measured once a week. At the beginning, 4th and 8th week of experimental feeding, 3, 12, 12 rats were slaughtered, respectively. Liver, perirenal and epididymal adipose tissue pads were weighed and their fatty acid composition was determined. Chemical composition of wholebody carcass was measured. Body weight gain was greater in rats fed the LCT diet than in rats fed the basal and MCT diets. Feed intakes were decreased in rats fed the MCT and LCT diets compared to that of the basal group. Subsequently, when compared to the basal group rats, feed efficiencies in rats fed the MCT and LCT diets were improved at the level of 6 and 14% for 4 weeks, and then 17 and 24% for 8 weeks, respectively. The weight of perirenal and epididymal adipose tissue pads tended to be larger in rats fed the MCT and LCT diets than in the basal group, although not significant. There were not significant differences in wholebody composition among the three groups. But it appeared that in rats fed the MCT diet, moisture content tended to be decreased and crude protein content increased compared to the LCT group rats. Fatty acid composition of the rats fed the LCT diet showed a good reflection of dietary fatty acid composition. Unlike LCT, little of medium chain fatty acid (MCFA) itself were incorporated into liver or adipose tissues. However, it seems that fat deposition of the MCT group was accomplished not by incorporation of dietary fatty acids but by de novo fatty acids synthesis.

The influence of dietary medium and long chain triglycerides on growth performances and fat deposition in growing rats.

The experiment was conducted to study the relationships among glucose, insulin, potassium, magnesium and calcium concentrations in the blood plasma following intravenous glucose or epinephrine injection. Plasma concentrations of potassium and magnesium were lowered after the respective injection of glucose and epinephrine. When compared to epinephrine injection, an injection of glucose solution decreased potassium and magnesium concentrations in plasma more rapidly. Moreover, the recovery of the concentration levels of these minerals was faster when the animals were injected with glucose rather than epinephrine. These changes were inversely related to those of plasma insulin concentrations. The results may indicate that increased insulin secretion caused by glucose or epinephrine injection results in decreases of the plasma magnesium as well as potassium concentration in sheep.

Effects of intravenous glucose or epinephrine injection on plasma concentrations of potassium, magnesium and insulin in sheep.

The effects of protein and/or energy deficiency on long bone growth were studied using rats of an average weight 100g. Four groups of Wistar rats were respectively fed on a normal diet, a low-energy diet, a low protein-diet, and a low-protein and low-energy diet for 45 days. Both energy and protein deficiency restricted gains of body weight and femur length and the activity of alkaline phosphatase in the tibia to the same extent. The epiphyseal growth plates of the femur in protein-deficient rats were as thin as those in energy-deficient rats. On the other hand, femur width and activity of acid phosphatase in the tibia were lower in protein-deficient animals than those in energy-deficient ones. Serum calcium concentrations and calcium content of bone were the same among all groups.

Ryoji Kawashima

Papers

Influence of Protozoa upon Rumen Acid Production and Liveweight Gains in Lambs

Saccharide fatty acid ester for bloat-prevention or bloat-treatment

The influence of dietary medium and long chain triglycerides on growth performances and fat deposition in growing rats.

Effects of intravenous glucose or epinephrine injection on plasma concentrations of potassium, magnesium and insulin in sheep.

The influence of protein and/or energy deficiency on the growth of long bone in rats.