Insulin secretion and glucose uptake in hypomagnesemic sheep fed a low magnesium, high potassium diet

Hyperglycemic and euglycemic clamp experiments were conducted to evaluate insulin secretion and glucose uptake in the hypomagnesemic sheep fed a low magnesium (Mg), high potassium (K) diet. Five mature sheep were fed a semipurified diet containing 0.24% Mg and 0.56% K (control diet) and five were fed 0.04% Mg and 3.78% K (low Mg/high K diet) for at least 2 weeks. In the hyperglycemic clamp experiment, plasma glucose concentrations were raised and maintained at a hyperglycemic steady-state (approximately 130 mg/100 ml) by variable rates of glucose infusion during the experimental period (120 minutes). The insulin response in the sheep fed the low Mg/high K diet (31.0 microU/ml) were significantly (P < 0.01) lower than those (111.7 microU/ml) of the sheep fed the control diet. In the euglycemic clamp experiment, insulin was infused at rates of 5, 10, 15, or 20 mU/kg/min, each followed by variable rates of glucose infusion to maintain a euglycemic steady-state (basal fasting levels). Hypomagnesemic sheep fed the low Mg/high K diet had significantly (P < 0.01) lower mean glucose disposal (3.72 mg/kg/min) across the insulin infusion rates compared with those of the sheep fed the control diet (5.37 mg/kg/min). These results suggest that glucose-induced insulin secretion and insulin-induced glucose uptake would be depressed in hypomagnesemic sheep and are caused by feeding the low Mg/high K diet.     

Responses to dietary starch or sucrose on protein and glucose kinetics in goats fed a high-concentrate diet

Abstract

Responses of whole body protein synthesis (WBPS) and glucose irreversible loss rate (ILR) were compared between dietary starch and sucrose in four male goats. Diets were fed at 1.2 times maintenance requirements of ME and CP with 30% of the ME as starch, starch plus sucrose or sucrose, twice daily. The diets consisted of 33, 32, 11 and 24% of alfalfa hay, corn, soybean meal and the carbohydrates, respectively. The WBPS and glucose ILR during 5 – 7 h after feeding were determined by an isotope dilution method of [²H₅]phenylalanine, [²H₂]tyrosine, [²H₄]tyrosine and [¹³C₆]glucose. Sucrose elevated ammonia nitrogen and lowered acetate concentrations in the rumen, but did not differ from starch in nitrogen retention. Glucose ILR and WBPS were similar between the carbohydrates. It was concluded that dietary sucrose would have effects similar to starch on WBPS and glucose kinetics in the absorptive state in goats fed a high-concentrate diet.     

Responses to dietary starch or sucrose on protein and glucose kinetics in goats fed a high-concentrate diet

Responses of whole body protein synthesis (WBPS) and glucose irreversible loss rate (ILR) were compared between dietary starch and sucrose in four male goats. Diets were fed at 1.2 times maintenance requirements of ME and CP with 30% of the ME as starch, starch plus sucrose or sucrose, twice daily. The diets consisted of 33, 32, 11 and 24% of alfalfa hay, corn, soybean meal and the carbohydrates, respectively. The WBPS and glucose ILR during 5-7 h after feeding were determined by an isotope dilution method of [2H5]phenylalanine, [2H2]tyrosine, [2H4]tyrosine and [13C6]glucose. Sucrose elevated ammonia nitrogen and lowered acetate concentrations in the rumen, but did not differ from starch in nitrogen retention. Glucose ILR and WBPS were similar between the carbohydrates. It was concluded that dietary sucrose would have effects similar to starch on WBPS and glucose kinetics in the absorptive state in goats fed a high-concentrate diet.     

Energy metabolism and protein balance in growing rats fed different levels of dietary fibre and protein

A study was performed to investigate the effect of different levels of dietary fibre (DF) and dietary protein on visceral organ size, digestibility, nitrogen balance and energy metabolism in rats. Thirty-six male Wistar rats, initial body weight about 76 g, were used in a factorial design consisting of three levels of DF (low, 100 g/kg DM; medium, 250 g/kg DM and high, 290 g/kg DM) and two levels of dietary protein (low, 120 g/kg DM and high, 223 g/kg DM). The added fibre source was soybean hulls and Danish fish meal was used as sole source of dietary protein. Measurements of gas-exchange were done on six rats (one group) while urine and faeces were collected individually. The ratio of food/empty body gain increased (P < 0.05) with increasing DF and decreasing levels of dietary protein. The weight of the digestive tract was larger (P < 0.05) in rats fed the high fibre diet than in those fed the low fibre diet. The digestibility of nutrients and energy decreased linearly with increasing level of soybean fibre (P < 0.05). An increased intake of DF was associated with a concomitant loss of protein and energy to faeces. The microbial degradation of NSP and other unabsorbed carbohydrates caused considerably changes in N metabolism of the colon. In rats fed the low protein diets increased levels of DF decreased N excretion in urine and increased N excretion in faeces, while the ratio of retained/digested protein remained constant. When rats were fed the high protein diet protein retention dropped in response to DF both absolute and relative to digested amount, indicating that energy intake could be a limiting factor. Heat production as a percentage of metabolizable energy (HP/ME) was higher (P < 0.05) in rats fed the low protein diet than in rats fed the high protein diet, but no significant difference was found among DF levels.     

The influence of dietary fibre on protein digestion and utilization in monogastrics

Current knowledge of the effects of dietary fibre and associated components on protein digestibility and utilization are discussed. Based on the literature it could be shown that the implications and mechanisms behind the effect of soluble and insoluble dietary fibre on protein digestibility and utilization are quite different. Insoluble dietary fibre will increase faecal bulk and faecal nitrogen excretion is primarily due to and increased excretion of cell wall bound protein. Contrary to this, soluble dietary fibre increase faecal bulk and faecal nitrogen due to an increased excretion of microbial nitrogen. A matter of controversy is the influence of dietary fibre on endogenous nitrogen excretion and factors affecting the losses of nitrogen in this way. It is not known if fibre acts as a secretogogue.     

Relation between feeding behaviour and energy metabolism in pigs fed diets enriched in dietary fibre and wheat aleurone

Feed intake and its daily pattern are regulated both at a short and a long term by several control pathways, including energy balance regulation. This trial aimed to determine the effect of dietary fibre (DB) (mix of wheat, soy and sugar beet pulp fibres) and aleurone supplementation and their interaction on energy and nitrogen balances in growing pigs with ad libitum access to feed. Forty pigs (BW: 35 kg) were fed diets differing by fibre concentration (NDF concentration: 10% or 14% DM) and aleurone supplementation (0, 2 or 4 g/kg) during 3 weeks. Pigs were housed individually in a respiration chamber during the last week to record feeding behaviour and measure energy and nitrogen balances (n = 36). Glucose oxidation was studied on the 6th day with an injection of [U-¹³C] glucose and measurement of ¹³CO₂ production. There was no significant interaction between DB inclusion and aleurone supplementation on any variables characterizing feeding behaviour. Pigs had less but longer meals with high level of DB, with an increased interval between two meals without effect on daily feed intake. The meal frequency significantly decreased when aleurone supplementation increased. Total tract apparent digestibility coefficient of DM, organic matter, ash, nitrogen and gross energy decreased when pigs received high DB level. Dietary fibre level increased significantly faecal excreted nitrogen. Aleurone supplementation decreased nitrogen retention. Free access to the feed induced a great individual variability not only in feed intake level (from 784 to 2290 g/day) but also in feeding behaviour (from 5.5 to 21.5 meals per day). This variability can be linked with the importance of underlying feed intake regulation pathways and difference in energy balance and metabolism efficiency. Several profiles of metabolism efficiency can be discriminate, thanks to a clustering based on feeding behaviour and pre-prandial concentrations of metabolites and hormones. In conclusion, DB inclusion decreased meal frequency, increased average meal size, decreased total tract apparent faecal digestibility coefficient of nitrogen and gross energy. Supplementation of aleurone decreased average daily feed intake with a reduction of the meal number per day, without modification of average meal size. Aleurone supplementation decreased nitrogen retention and nutrient deposition. Independently of experimental diets, the high individual variability permitted discriminating different profiles with different metabolic strategies. Efficient pigs with a high energy retention as protein and lipid seem to be able to adapt their metabolism according to energy sources.     

Effect of sulfur supplements on cellulolytic rumen micro-organisms and microbial protein synthesis in cattle fed a high fibre diet

AIM: To examine the effect of sulfur-containing compounds on the growth of anaerobic rumen fungi and the fibrolytic rumen bacteria Ruminococcus albus, Ruminococcus flavefaciens and Fibrobacter succinogenes in pure culture and within the cattle rumen. METHODS AND RESULTS: The effect of two reduced sulfur compounds, 3-mercaptopropionic acid (MPA) or 3-mercapto-1-propanesulfonic acid as the sole S source on growth of pure fibroyltic fungal and bacterial cultures showed that these compounds were capable of sustaining growth. An in vivo trial was then conducted to determine the effect of sulfur supplements (MPA and sodium sulfate) on microbial population dynamics in cattle fed the roughage Dichanthium aristatum. Real-time PCR showed significant increases in fibrolytic bacterial and fungal populations when cattle were supplemented with these compounds. Sulfate supplementation leads to an increase in dry matter intake without a change in whole tract dry matter digestibility. CONCLUSIONS: Supplementation of low S-containing diets with either sodium sulfate or MPA stimulates microbial growth with an increase in rumen microbial protein supply to the animal. SIGNIFICANCE AND IMPACT OF THE STUDY: Through the use of real-time PCR monitoring, a better understanding of the effect of S supplementation on discrete microbial populations within the rumen is provided.     

The effect of dietary inclusion of starch,sucrose and xylose on the utilization of dietary energy in sheep

A calorimetric experiment of 4 × 4 Latin square design was undertaken to study the effect of sugar-beet pulp (SBP), maize starch, sucrose and xylose on energy metabolism in sheep. The four diets comprised a diet (A) of dried grass, soya-bean meal and SBP (450, 50 and 500 g kg⁻¹ on dry matter (DM) basis) and corresponding diets in which 400 g kg⁻¹ of SBP was replaced by maize starch (B), sucrose (C) or xylose (D); all diets were offered at a level of 600 g DM day⁻¹. After the Latin square was completed, energy value of the basal diet of dried grass and soya-bean meal (900 and 100 g kg⁻¹ DM; 600 g day⁻¹) was determined in the same four sheep.Treatment differences in organic matter, gross energy, nitrogen (N) and neutral detergent fibre (NDF) digestibility were non-significant. Differences in N retention were not significant.Digestible energy (DE) contents (MJ kg⁻¹ DM) were 13.27, 13.22, 13.21 and 13.21 MJ kg⁻¹ for diets A, B, C and D, respectively. Energy loss in methane was higher (P < 0.05) for Diet A than for other diets. Metabolizable energy (ME) contents for the diets A-D were 11.25, 11.22, 11.32 and 11.40 MJ kg⁻¹ DM, respectively. Metabolizability (q) of the diets averaged 0.642 and was not significantly affected by the diet given. There was a trend for heat production to be higher in sheep given the sucrose-containing diet (C) than in those given other diets (6.34 versus 6.04 MJ day⁻¹) and as a result, energy retention was lower (0.38 versus 0.64 MJ day⁻¹), but the difference did not reach statistical difference. Efficiencies of utilization of ME for maintenance and fattening (k_mf) averaged 0.67 and were in good agreement with those predicted from equations of the Agricultural Research Council (1980) excepting the lower k_mf (0.63) for Diet C.The mean ME content of SBP calculated by difference was 13.05 MJ kg⁻¹ DM and the corresponding values for mixtures of SBP + starch, SBP + sucrose and SBP + xylose (600 and 400 g kg⁻¹ DM) were 12.98, 13.16 and 13.36 MJ kg⁻¹ DM, respectively.     

Effects of added dietary taurine on erythrocyte lipids and oxidative stress in rabbits fed a high cholesterol diet

Lipid peroxidation leads to damage of polyunsaturated fatty acids of membrane phospholipids. The contribution of oxidative stress to hypercholesterolemia-induced hemolytic anemia and the effects of addition of taurine on erythrocyte lipid composition, oxidative stress, and hematological data were studied in rabbits fed on a high cholesterol (HC) diet (1%, w/w) for 2 months. The effects of taurine on erythrocyte hemolysis and H2O2-induced lipid peroxidation were investigated in normal rabbit erythrocytes in vitro. The HC diet resulted in increases in plasma lipids and lipid peroxide levels as well as increases in cholesterol levels and the cholesterol:phospholipid ratio in the erythrocytes. This diet caused a hemolytic anemia, but lipid peroxide levels remained unchanged in the erythrocytes of the rabbits. Taurine (2.5%, w/w) added to the food has an ameliorating effect on plasma lipids and lipid peroxide levels in rabbits fed on a HC diet. This treatment also caused decreases in elevated erythrocyte cholesterol levels and cholesterol:phospholipid ratio due to the HC diet, but it did not prevent the hemolytic anemia and did not change erythrocyte lipid peroxide levels. In addition, in an in vitro study, taurine did not protect erythrocytes against H2O2-induced hemolysis or lipid peroxidation. These results show that the HC diet causes hemolytic anemia without any changes in erythrocyte lipid peroxidation, and taurine treatment was not effective against hemolytic anemia caused by the HC diet.     

The 16S rRNA and mcrA gene based comparative diversity of methanogens in cattle fed on high fibre based diet

In the present study, the diversity of rumen methanogens in crossbred Karan Fries cattle was determined by constructing 16S rRNA and mcrA (methyl coenzyme-M reductase α subunit) gene libraries using specific primers. All thirteen OTUs or phylotypes from 16S rRNA library clustered with order Methanobacteriales, twelve of which aligned with Methanobrevibacter spp., whereas one OTU resemble with Methanosphaera stadtmanae. Out of eighteen OTUs identified from mcrA gene library, fifteen clustered with order Methanobacteriales, two resemble with Methanomicrobiales and remaining one grouped with Methanosarcinales. These results revealed that Methanobrevibacter phylotype was predominantly present in Karan Fries crossbred cattle fed on high fibrous diet containing wheat straw. Compared to 16S rRNA gene, mcrA gene OTUs clustered in three orders providing better insights of rumen methanogens diversity in cattle.     

The necessity of niacin in rats fed on a high protein diet

It is known that niacin itself is not necessary in rats when tryptophan is given in adequate amounts, because rats can biosynthesize niacin from tryptophan. In our experiment, young rats were fed on a 20%, 40%, 60%, or 70% casein diet with or without niacin. The rats fed on the 20%, 40%, and 60% casein diets did not require niacin for growth, but the rats fed on the 70% casein diet needed it. This phenomenon was attributed to the supposition that liver aminocarboxymuconate-semialdehyde decarboxylase activities increased according with the dietary casein levels. The conversion ratio of tryptophan-niacin in rats fed on the 70% casein diet became extremely low, and then the rats needed niacin.     

Development of the gastrointestinal tract and digestibility of dietary fibre and amino acids in young chickens, ducks and geese fed diets with high amounts of barley

The experiment comprised of 50 chickens, 40 ducks and 30 geese fed a diet containing 40% barley. Birds were kept in metabolic cages from 1 to 42 days of age. A balance trial was carried out during the last week of the bird's life and the apparent digestibility of nutrients was determined. At 21 and 42 days of age 12 animals per species were killed. The absolute length of intestines followed the live weight (LW) of the animals. In relation to metabolic LW (kg(0.67)), the total length was significantly higher in chickens and geese than in ducks at 21 days of age, but identical in the three species at 42 days of age. The absolute and relative weights of intestines were smaller in ducks than in chickens and geese both at 21 and 42 days of age. Dietary fibre was digested better by chickens than by ducks and geese (P<0.01). Ileal digestibility of total amino acids amounted to 76% in chickens, 69% in ducks (P>0.05) and only 56% in geese (P<0.01) with relatively low digestibility of methionine (70, 44 and 52%) and lysine (72, 57 and 41%), respectively. The overall tract-faecal digestibility of total amino acids was evaluated on the level of 86% for all three species and indicates a substantial hind gut synthesis of amino acids.     

The effects of Lactobacillus-fermented milk on lipid metabolism in hamsters fed on high-cholesterol diet

The objective of this study was to evaluate the effects of local Lactobacillus strains (NTU 101 and 102) on cholesterol-lowering effects in vivo. Thirty male hamsters were housed, divided into five groups, and fed on a cholesterol diet (5 g/kg diet) to induce hypercholesterolemia. Milk fermented by Lactobacillus paracasei subsp. paracasei NTU 101, Lactobacillus plantarum NTU 102, and Lactobacillus acidophilus BCRC 17010 was administrated for this study. After treatment with different fermented milk, blood was taken and liver was removed for the determination of lipoproteins, including total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglyceride. Lactobacilli and bifidobacteria decreased (10⁵) in the control group; when hamsters were fed on fermented milk, the number of lactobacilli (10⁷–10⁸) and bifidobacteria (10⁵–10⁷) was increased. Serum and liver total cholesterol levels were significantly reduced by about 26.4, 23.5, and 30.1% and by about 17.7, 15.9, and 13.4% when hamsters were given fermented milk. However, serum HDL-C and LDL-C were also reduced. The results of this study showed that the hypocholesterolemic effect of local Lactobacillus strains was attributed to its ability to lower serum and liver total cholesterol levels. Thus, local Lactobacillus strains could significantly increase probiotic count.     

Effect of dietary cholesterol on plasma cholesterol concentration in subjects following reduced fat,high fibre diet.

One hundred and sixty eight subjects participated in a randomised crossover study to determine whether halving or doubling the present dietary cholesterol intake from eggs had any influence on blood cholesterol concentration in people following current dietary recommendations. During the first eight weeks all participants were advised to follow a reduced fat diet (26% total energy for hyperlipidaemic patients, 35% total energy for normolipidaemic volunteers) with an increased ratio of polyunsaturated to saturated fatty acids. This background diet was continued throughout the 16 week experimental period, during which participants ate either two or seven eggs a week. A small but significant increase in total cholesterol was seen after four weeks in the group eating seven eggs a week compared with that in the group eating two eggs a week, but this was no longer apparent after eight weeks. Previous studies suggesting that dietary cholesterol has a greater effect on the serum cholesterol concentration either have been carried out against a background of a higher fat intake or have contrasted extreme cholesterol intakes. A further reduction in dietary cholesterol seems to be unnecessary in those people who have already reduced their intake of saturated fat and increased the ratio of polyunsaturated to saturated fatty acids and fibre rich carbohydrate.     

The influence of dietary protein on ascorbic acid metabolism in rats

1. d-Glucuronolactone reductase, l-gulonolactone oxidase, uronolactonase, dehydroascorbatase, l-gulonate dehydrogenase and l-gulonate decarboxylase have been measured in the tissues of rats fed on diets containing variable amounts of protein. Rats fed on a protein-free or a 2% casein diet for 15 days showed a marked decline in the activities of d-glucuronolactone reductase, l-gulonolactone oxidase, uronolactonase and dehydroascorbatase in the liver, and no change in l-gulonate dehydrogenase and l-gulonate decarboxylase activities in the kidney when compared with rats fed on diets containing 9%, 18% or 25% casein. Giving diets containing 60% or 88% casein to rats did not appreciably alter the activities of uronolactonase, dehydroascorbatase, l-gulonate dehydrogenase and l-gulonate decarboxylase, but inhibited considerably the activities of d-glucuronolactone reductase and l-gulonolactone oxidase in the liver, resulting in decreased synthesis of ascorbic acid. 2. Rats fed on a 25% casein diet showed maximal weight gain, higher tissue reserve of ascorbic acid and higher urinary excretion of both ascorbic acid and glucuronic acid when compared with rats fed on diets containing lower or higher amounts of protein.