Dietary fibre and physicochemical properties of edible Spanish seaweeds

 Total dietary fibre content of five edible marine Spanish seaweeds: Fucus vesiculosus, Laminaria digitata (Kombu), Undaria pinnatifida (Wakame), Chondrus crispus (Irish moss), and Porphyra tenera (Nori) ranged from 33.6 to 50% of which 19.6 to 64.9% was soluble. For brown algae, the soluble fibre obtained by the AOAC method followed by dialysis, contained uronic acids from alginates and neutral sugars from sulphated fucoidan and laminarin. For red seaweeds, the main neutral sugars corresponded to sulphated galactans: carrageenan (Chondrus) or agar (Nori), respectively. Insoluble fibres (12–40%) were essentially made of cellulose, plus residual fucose-containing polysaccharides, except for the red seaweed Nori, which contained an insoluble mannan and xylan. Protein content in powdered algae was higher in red (20.9–29.8%) than in brown seaweeds (6.9–16%), although protein digestibility was apparently low as inferred from preliminary in vitro results with Fucus and Laminaria. Ashes (21–39.8%) and sulphate content (2.8–10.5%) were high in all seaweeds. Minor components were lipids (0.2–2.5%) and extractable polyphenols (0.4%). Regarding the physicochemical properties, oil retention was low, while swelling, water retention, and cation exchange capacity were higher in brown algae, related to their higher uronic acid plus sulphate content. Received: 2 May 2000 / Revised version: 13 June 2000     

Effect of the insoluble dietary fibre from oil palm fat-free flour on digestibility in rats

This work shows the results of comparing the effects of the insoluble dietary fibre from oil palm fat-free flour and cellulose on the growth, weight, humidity and composition of faeces in adult rats (Sprague–Dawley). Five groups of rats were fed for 4 weeks. The control group was fed with a diet free of fibre, and the remaining four groups with diets containing 50 or 100 g of either oil palm fat-free flour or cellulose, respectively. The adaptation period was 4 days. The evolution of growth and food intake did not vary significantly p<0.05 regardless of the type of diet. On the other hand, faeces excretion increased by 3.3–4.7 g/day in the groups of rats fed with oil palm fat-free flour, while it increased by only 3.1–4 g/day in diets based on cellulose. A higher content of water was observed in the faeces of rats fed with insoluble dietetic fibre from oil palm fat-free flour. The apparent digestibility of the insoluble dietary fibre of oil palm fat-free flour was low (35%), showing resistance to fermentation. The digestibility of the protein tended to decrease more with the insoluble dietary fibre of oil palm than with the cellulose, which may be related. ©     

Effect of fructooligosaccharide on nutritional parameters and mineral bioavailability in rats

The effect of fructooligosaccharide on protein digestibility and mineral absorption was studied in rats fed diets containing 5 g kg^?1 fructooligosaccharide, 5 g kg^?1 cellulose/fructooligosaccharide (1:1) or 5 g kg^?1 cellulose as a source of dietary fibre. Addition of cellulose/fructooligosaccharide or fructooligosaccharide to the diet did not significantly modify the daily food intake and food efficiency. However, the fructooligosaccharide‐fed group showed a significant decrease in body weight gain compared with cellulose‐fed groups. Faecal excretion was significantly lower when there was fructooligosaccharide intake, despite there being no significant differences in cellulose‐fed groups. Intake of fructooligosaccharide produced an increase in caecal content and an enlargement of the caecal wall. This trophic effect could be attributed to short‐chain fatty acids produced from the anaerobic fermentation of fructooligosaccharide by intestinal bacteria. Cellulose/fructooligosaccharide enhanced the apparent absorption and apparent retention of Ca, Mg, Zn and Fe. Fructooligosaccharide‐fed rats experienced an increase in apparent absorption and apparent retention of Mg compared with cellulose‐fed rats. Fructooligosaccharide intake at the lowest dose was enough to provide a desirable effect on mineral bioavailability in rats without any modification of nutritional parameters. © 2002 Society of Chemical Industry     

Consumption of raw and fried sardine (Clupea pilchardus) as protein source of diets: effects on iron metabolism in rats

The influence of fried fish consumption on dietary iron bioavailability in rats was studied. Sardines (Clupea pilchardus), raw and fried in olive oil, were used whole or defatted to prepare the samples. Five diets containing casein and the different samples as protein source were prepared. After in vitro digestion of the diets a greater proportion of soluble iron was found in the casein diet compared with the sardine diets. Five groups of rats were fed the diets over 28 days. Body weight and food intake were monitored weekly, and during days 21–28 an iron balance study was carried out. No significant differences were observed in food intake, body weight and protein efficiency ratio between groups. Absorbed and retained iron and apparent iron digestibility were higher in rats fed the sardine diets with respect to the control group, except in the whole fried sardine group. Metabolic efficiency and retention efficiency were increased in the four sardine groups. The frying process led to significant changes in the overall digestive and nutritive efficiency of dietary iron, which were different depending on whether the diets contained whole sardine or its protein. It was concluded that the consumption of sardines, whether raw or fried in olive oil, enhances dietary iron availability. © 2002 Society of Chemical Industry     

The influence of dietary fibre sources on growth,feed efficiency and digestibilities of dry matter and protein in rats

Hulls from Tower canola (TCH), Regent canola (RCH) and soya beans (SBH) were included at 10 or 20% in soya bean meal based diets for rats, to compare the effects of these fibre sources on growth, feed consumption, feed efficiency and dry matter and protein digestibilities. A soya bean meal based control diet and another diet containing a purified fibre source (Alphafloc) at a 10% level, were included for a further comparison. Each of the diets was fed to six rats in a 4-week feeding trial. The diets gave similar weight gain, feed consumption and feed efficiency values. The control diet had the highest mean coefficient of dry matter digestibility (80.8%) and the 20% SBH and Alphafloc diets had the lowest (72.4 and 72.2%). The canola hull and 10% SBH and Alphafloc diets had intermediate values (73.2–75.0%). There was a highly significant negative correlation between the dietary fibre content and the dry matter digestibility of the diets. The control and Alphafloc diets showed the highest and similar apparent (81.4 and 79.9%) and true (86.8 and 85.3%) digestibility values for dietary protein. The 20% canola and soya bean hull diets showed the lowest apparent (71.4–73.7%) and true (76.9–79.4%) digestibility coefficients. The 10% canola and soya bean hull diets had intermediate apparent and true protein digestibility values (73.2-75.3 and 78.4–80.6%, respectively). The chemical analysis of the fibre sources showed that Alphafloc had the highest cellulose content (88%) and the lowest lignin content (0.6%), while canola hulls had the lowest cellulose content (25.4–28.4%) and the highest lignin content (26.6–28.9%). Soya bean hulls had intermediate cellulose (50%) and low lignin (1.3%) contents. The results suggest that cellulose did not have a detrimental effect on the dietary protein digestibility but lignin and/or some other undetermined factors in the hulls had an adverse effect on protein digestibility.     

Effects of dietary fibre‐ and polyphenol‐rich grape products on lipidaemia and nutritional parameters in rats

The aim of this work was to evaluate the effects of three dietary fibre‐ and polyphenol‐rich materials obtained from grapes on serum cholesterol, lipoprotein and triglyceride concentrations as well as on body weight, fat and protein digestibility in adult Wistar rats fed on cholesterol‐free and 10 g kg⁻¹ cholesterol‐added diets. Dietary fibre content of materials ranged from 540 to 590 g kg⁻¹. Intake of grape products increased stool weight and the amount of fat and protein excreted in faeces, but did not affect negatively animal growth or protein efficiency of the diet in Wistar rats. Studied grape fractions lower serum total cholesterol and LDL cholesterol concentrations in hypercholesterolemic rats. These results could be taken into account in potential applications of these products as a food ingredient. © 2000 Society of Chemical Industry     

Composition and antioxidant capacity of low-salt meat emulsion model systems containing edible seaweeds

The study was designed to determine the influence of the addition of edible seaweeds, Sea Spaghetti (Himanthalia elongata), Wakame (Undaria pinnatifida), and Nori (Porphyra umbilicalis), on fatty acid composition, amino acid profile, protein score, mineral content and antioxidant capacity in low-salt meat emulsion model systems. The addition of seaweeds caused an increase (P < 0.05) in n-3 polyunsaturated fatty acids (PUFA) and a decrease (P < 0.05) in the n-6/n-3 PUFA ratio. The thrombogenic index significantly decreased (P < 0.05) in Nori and Wakame meat samples. Meat systems made with added seaweeds had lower (P < 0.05) sodium contents than control samples. In general, addition of seaweeds to products increased (P < 0.05) the concentrations of K, Ca, Mg and Mn. The presence of Nori caused an increase (P < 0.05) in levels of serine, glycine, alanine, valine, tyrosine, phenylalanine and arginine, whereas Wakame and Sea Spaghetti produced no significant changes in amino acid profiles in the model systems. The inclusion of Sea Spaghetti increased the sulphur amino acid score by 20%. The added seaweeds supplied the meat samples with soluble polyphenolic compounds, which increased the antioxidant capacity of the systems. The polyphenol supply and antioxidant increase were greatest (P < 0.05) in the samples containing Sea Spaghetti.     

Nutritional status affects the absorption and whole-body and organ retention of cadmium in rats fed rice-based diets

Staple grains such as rice, wheat and maize consumed by different societal groups differ greatly in their concentrations and bioavailability of the cadmium (Cd) antagonists, zinc (Zn), iron (Fe), and calcium (Ca). We hypothesized thatthe low nutritional status of rice consumers, which results from an inadequate supply of these minerals from rice, could contribute significantly to a higher apparent susceptibility to soil Cd contamination from rice than the higher nutritional status of those who consume other grains with higher mineral content. To test this hypothesis, a 2 x 2 x 2 factorial study was conducted. Rats were fed diets with adequate or marginal amounts of dietary Zn, Fe, or Ca. The basal diets contained 40% unenriched, milled rice fortified with 0.62 mg of Cd/kg as CdCl2 (0.25 mg of Cd/kg diet). Rat consumed the diets for 5 weeks and then were fed 1 g of a similar diet containing 10(9)Cd-labeled rice. After 2 weeks, whole-body (WB) retention of 109Cd was determine. Rats then were killed, and the organs were removed for total Cd determinations. Rats fed marginal concentrations of dietary Zn had slightly but significantly more WB retention of 109Cd than controls; however, rats fed marginal Fe or Ca had as much as 3-fold higher retention of the label. Rats fed marginal amounts of Zn, Fe, and Ca combined retained as much as 8 times more 109Cd than rats fed adequate minerals. The effects on Cd concentrations in liver and kidney were similar to the effects on 109Cd retention. These results support the hypothesis that populations exposed to dietary sources of Cd and subsisting on marginal mineral intakes could be at greater risk than well-nourished populations exposed to similar amounts of dietary Cd. Thus, different food crops can cause unequal Cd risk at equal Cd concentration if diets containing the food are not balanced to provide adequate interacting mineral concentrations.     

Effect of dietary inclusion of goat milk on the bioavailability of zinc and selenium in rats

The effects of dietary inclusion of freeze-dried goat and cow milk on the utilization of zinc and selenium, and on the metabolic fate of zinc, were studied in transected (control) and resected rats (resection of 50% of the distal small intestine). Intestinal resection reduced the apparent digestibility coefficient and zinc retention in the cow milk diet, whereas these biological indices were similar in transected (control) and resected rats with standard (without milk) and goat milk diets. The apparent digestibility coefficient and retention of selenium were not affected by intestinal resection in the animals fed with the three diets studied. In transected (control) and resected rats, the apparent digestibility coefficient and retention of zinc and selenium were higher for the goat milk diet than for the other two diets. Zinc deposits in the organs, expressed as microg/g dry weight were in order of decreasing concentrations: femur, testes, sternum, liver, kidney, heart, spleen, longissimus dorsi muscle and brain. Deposits were greatest with the goat milk diet, followed by the standard diet and were lowest for the rats given the cow milk diet, both for transected (control) and resected animals. We conclude that consumption of the goat milk diet produces a greater bioavailability of zinc and selenium and a greater deposit of zinc in key organs, for both the transected (control) and the resected rats, with respect to the standard diet and the cow milk diet.     

Influence of different types and proportions of added edible seaweeds on characteristics of low-salt gel/emulsion meat systems

The effects of three different types of edible seaweeds, Sea Spaghetti (Himanthalia elongata), Wakame (Undaria pinnatifida), and Nori (Porphyra umbilicalis) added at two concentrations (2.5% and 5% dry matter) on the physicochemical and morphological characteristics of gel/emulsion systems were evaluated. The addition of seaweeds improved (P<0.05) water- and fat-binding properties except in the case of Nori added at 2.5%. Hardness and chewiness of the cooked products with added seaweed were higher (P<0.05), and springiness and cohesiveness were lower (P<0.05) than in control samples. Colour changes in meat systems were affected by the type of seaweed. The morphology of sample differed depending on the type of seaweed added, and this is the result of differences in physical and chemical characteristic of the seaweed powder used. In general, products formulated with the brown seaweeds (Sea Spaghetti and Wakame) exhibited similar behaviour, different from that of products made with the red seaweed Nori.     

Improvement in food intake and nutritive utilization of protein from Lupinus albus var. multolupa protein isolates supplemented with ascorbic acid

The protein quality of protein isolates from lupin (LPI) (Lupinus albus var. multolupa), prepared by isoelectric precipitation, was assessed by chemical analysis of protein and amino acids and biological analysis of digestive and metabolic utilization of protein by growing rats. The animals were fed isonitrogenous and isocaloric diets adjusted to meet their nutrient requirements, in which lupin protein isolate was the only protein source, complemented with 0.5% methionine. Different LPIs were prepared with addition, or not, of ascorbic acid as antioxidant. Protein isolates had a protein content of 87.8–98.1%. Manganese content of protein isolates was reduced by 72.8–89.5% compared to the raw seed flour. Results from in vivo experiments showed that addition of 0.5% ascorbic acid to LPI incorporated into diets led to a 82.8% increase in daily food intake, when compared to the non-supplemented LPI, reaching similar values to those obtained with a casein–methionine control diet. Digestive and metabolic utilization of protein from LPI, assessed by nitrogen absorption or apparent digestibility coefficient, and by nitrogen balance or percentage of retained to absorbed nitrogen, respectively, was high, when the dietary intake of animals fed the LPI diets was adequate after addition of 0.5% ascorbic acid, although slightly inferior to the values obtained with a casein–methionine control diet. The high nutritive utilization of protein was reflected in excellent growth and nutritional indices assayed. In conclusion, ascorbic acid supplementation led to an improvement in the palatability of the LPI diets and, therefore, in daily food intake, which was reflected in a higher nutritive utilization of protein and improvement in weight gain and the food transformation index.     

Iranian Flat Breads: Relative Bioavailability of Zinc

The effect of flour extraction rate, type and length of fermentation and baking conditions on relative bioavailability of zinc of five distinctly different Iranian flat breads and their unfermented doughs, was determined using weanling rats fed low (5.5 ppm) levels of dietary zinc. When breads rather than unfermented doughs were used for preparation of diets, with one exception, bioavailability of Zn significantly (P < 0.05) improved. Rats on the barbari-bread-based diet showed the highest weight gain and femur zinc content. There was no significant difference in weight gain among rats on dough-based diets. High correlation of weight gain and femur zinc with feed intake and low or no correlation with fiber or Zn:phytate molar ratio of the diets was observed.     

Varietal variation in the anti-nutritive effects of field beans (Vicia faba) when fed to rats.

Testa and cotyledons were separated from white and coloured flowered varieties of field beans (Vicia faba) and incorporated into complete diets for rats. Diets containing 10% testa from the coloured variety caused a 15% reduction in live weight gain compared with the diets containing testa from the white flowered variety. This was accompanied by a reduction in the true digestibility of nitrogen and the apparent digestibility of carbohydrates and lipids. The protein efficiency ratio and the net protein utilisation were also reduced but the biological value of protein was not significantly affected. The efficiency of utilisation of ingested feed dry matter was significantly reduced for the diets containing coloured flower testa but when live weight gain was expressed as a fraction of ingested digestible dry matter there were no significant differences. Live weight gain and digestibility of organic matter components were highly negatively correlated with the total phenolic content of the diet. It was concluded that the reduction in live weight gain of animals fed diets containing testa of a coloured variety compared with that of a white flowered variety was caused mainly by the reduction in digestibility of organic matter brought about by the complexing of dietary and digestive enzyme proteins by the high content of phenolic compounds present in the testa of the coloured variety. A 10% reduction in live weight gain was recorded for animals consuming diets containing cotyledons of coloured varieties compared with those consuming white flowered cotyledons. This reduction was not accompanied by any change in the digestibility of organic matter components and the true digestibility of nitrogen and protein efficiency ratio were not significantly different. There was, however, a significant reduction in the biological value which was a result of increased urinary nitrogen output. It was concluded that the cotyledons of the coloured flowered variety contained an anti-nutritive factor which was not a tannin-like compound and which had an effect on the protein metabolism of the animal.     

Effect of high-fat diets supplemented with okara soybean by-product on lipid profiles of plasma,liver and faeces in Syrian hamsters

The main components of okara, a by-product from soybean, are dietary fibre and protein. In this study we fed okara based diets with different amounts of fibre, protein and isoflavones to determine their effect on the lipid profile in the plasma, liver and faeces of an animal model. Male golden Syrian hamsters were fed high-fat diets supplemented with okara for 3 weeks. The supplemented diets contained 13% or 20% of okara fibre (OK-13 and OK-20), low-protein okara with 13% of fibre (OK1-13), and isoflavone-free okara with 13% of fibre (OK2-13). Okara supplemented diets did not produce significant differences in the feed intake or body weight gain (p > 0.05). The plasma levels of triglycerides, VLDL- plus LDL cholesterol and total cholesterol in hamsters fed OK-20 decreased significantly (p < 0.05) with respect to the 20% control group (C-20). However, no significant differences (p > 0.05) were found in LDL- and HDL-cholesterol plasma levels in all experiments. Total lipids, triglycerides, total and esterified cholesterol concentrations in liver were reduced by OK-20 diet. Regarding the hamsters fed OK-13 diets, the mean values of the total lipid, triglyceride and cholesterol in the plasma and liver decreased as compared to the control (C-13), but the differences were not statistically significant. All of the okara diets assayed increased the faecal excretion of total lipids, triglycerides, free cholesterol and total nitrogen (p < 0.05) compared to their respective controls. Our results suggest that the main components of okara, dietary fibre and protein, could be related with the total lipids and cholesterol decrease in the plasma and liver, as well as with the faecal output increase in high-fat fed hamsters. Okara might play an interesting role in the prevention of hyperlipidemia and could be used as a natural ingredient or supplement for functional food preparation.     

Effects of alkaline,hydrogen peroxide-treated fibres on nutrient digestibility,blood sugar and lipid profile in rats

Three diets containing different sources of dietary fibre, wheat bran, faba bean testas and rice hulls, were tested to determine the effects of alkaline, hydrogen peroxide (AHP)-treated fibre at 10% substitution level of dextrose corn flour on apparent digestibility, faecal characteristics, and levels of plasma glucose and lipid profile in rats. A fourth non-fibrous diet was used as a control. The results showed that, although AHP treatment of fibres resulted in reduction of their weight after washing, it caused an increase in their water absorption and in their swollen volume when mixed with an excess of water (up to three fold) as in the case of wheat bran. Rats consuming diets containing dietary fibres showed a significant loss of body weight but no significant effects on heart weight or liver weight were found. Faeces of rats fed on dietary fibre diets showed an increase in weight and volume, which resulted in reduction of faecal density. The consumption of the treated fibre significantly reduced total cholesterol, plasma triglycerides and blood sugar; wheat bran was the most effective followed by rice hulls and faba bean testas. On the other hand, it effected an increase in the plasma content of high-density lipoprotein HDL-C but this increase was only significant in rats fed with wheat bran. Alkaline hydrogen peroxide-treated fibres showed a great improvement in their absorbency, making them equal to or even better than untreated fibre in lowering blood lipids and sugar levels, in addition to their excellent effect on the physiological function of the intestinal tract.     

High apparent ileal digestibility of amino acids in raw and germinated faba bean (Vicia faba)‐ and chickpea (Cicer arietinum)‐based diets for rats

The effects of germinated faba bean (Vicia faba minor var Alameda)‐ and chickpea (Cicer arietinum kabuli var Athenas)‐based diets on performance, N utilisation, amino acid ileal digestibility and plasma concentrations were studied in growing male Wistar rats. Raw and germinated faba bean and chickpea seed meals were incorporated in essential amino acid‐supplemented and energy‐equalised diets as the only sources of protein. A lactalbumin‐based diet equalised in protein (100 g kg^?1) and digestible energy (15.5 kJ g^?1) with the test diets was used as control. Weight gains, gain/feed ratios, N retention and NPU values of animals fed raw or germinated legumes were lower than those of rats given the control (lactalbumin) diet, while faecal dry weights were higher. However, N retention and NPU values of rats fed germinated faba bean diets were higher and faecal dry weights lower than those of animals fed non‐germinated faba bean diets. Liver and thymus fresh and dry relative weights were lower than controls for all legume diets, whilst small intestine, caecum and colon relative weights were higher than controls for non‐germinated faba beans and chickpeas either germinated or not. Caecum and colon fresh and dry relative weights of rats fed germinated faba bean seeds were lower than those of rats fed non‐germinated faba beans and not different from controls. Except for aspartic acid and proline in rats fed raw faba bean diets, apparent ileal digestibilities of amino acids were not different or higher in rats fed legume diets as compared with controls. Except for arginine, apparent ileal amino acid digestibility was higher for germinated than for non‐germinated faba bean seeds. The amounts of glycine, arginine and ornithine in plasma significantly increased whilst those of threonine, alanine, leucine and lysine decreased with respect to controls in faba bean‐ or chickpea‐fed rats, either germinated or not. We conclude that (a) germination of faba bean seeds gave rise to a significant (P < 0.01) but limited improvement in performance, N retention and apparent ileal digestibilities of some amino acids in growing rats compared with non‐germinated seeds, while there was no detectable effect in the case of germinated chickpea seeds, and (b) the apparent ileal amino acid digestibility of essential amino acid‐supplemented diets based on faba bean or chickpea meals, either germinated or not, is similar or even higher than controls. © 2002 Society of Chemical Industry     

The effect of dietary antibiotics on protein and energy metabolism in rats: possible significance of the gut microflora.

The influence of the intestinal microbial activity on protein metabolism was tested in rats with three diets fed without and with antibiotics (Nebacitin). True protein digestibility, biological value, net protein utilisation, true amino acid digestibility and apparent digestible energy were measured. The intestinal microbial activity was on average reduced to one-fifth by antibiotics. On a diet low in crude fibre (2.5%) but high in crude protein (17.6%), this reduction had only a minor influence on the parameters for protein quality that were measured. However, true digestibilities of histidine and cystine were strongly reduced by the antibiotic treatment. The digestibility of energy was also significantly reduced (5%). For diets higher in crude fibre and lower in protein, the influence of the microbial activity was more pronounced. Digestibility of protein and energy were severely reduced by the dietary antibiotic treatment. In general, antibiotic supplementation decreased the parameters that were measured.     

Nutritional quality of storage proteins during germination of Indian bean (Dolichos lablab. var. lignosus) seeds

The dry Indian bean seed composed of starch is the major component (33%) and protein accounted for 25% of dry weight. The ability of germination to increase the nutritional quality of storage proteins was studied by germinating the Indian bean seeds for 0, 8, 16, 24 and 32 h and evaluated the nutritional quality through an in vitro protein digestibility (IVPD), protein efficiency ratio (PER), apparent and true digestibility. The IVPD of raw Indian bean seeds by pepsin alone was 60.12% and the digestibility by pepsin and trypsin together improved to 64.24%. The in vitro digestibility by both processes increased appreciably with germination and marked increase was noticed in the early stage of germination. The PER values followed the same pattern as the value of weight gain of rats fed with diets containing raw and germinated Indian bean. The lowest PER values were observed with raw bean diet. However, the value increased in rats fed with diets of Indian bean germinated for different intervals of time, reaching comparable PER values with the group maintained on casein diet. The true and apparent nitrogen digestibility of raw bean low being only 82 and 72%, respectively observed with casein diet. Diets with germinated bean protein showed a marked increase in both parameters, although the values were still less than that displayed by the casein fed rats. Germination is a simple biochemical enrichment tool and significantly improves palatability, digestibility and the nutritive utilisation of proteins in Indian bean seeds.     

Potassium carbonate as a potassium source and dietary buffer for lactating Holstein cows during hot weather

Twenty-four lactating Holstein cows were offered diets containing .93, 1.29, and 1.53% potassium during hot weather. Cows fed 1.53% potassium consumed more dry matter than cows fed either .93 or 1.29% potassium. Milk production and composition were not different. Potassium intake and fractional excretion increased, and fecal output as a percentage of intake declined with diets containing 1.29 and 1.53% potassium. Magnesium fractional excretion was least and fecal output greatest in cows fed 1.29% potassium. Fecal sodium output and fecal output as a percentage of intake was reduced by 1.53% dietary potassium. During comparison period 2, potassium carbonate at 0, .5, or 1.0% had no effect on feed consumption or milk yield, but buffered diets increased milk fat percentage and depressed milk protein percentage. No effects of buffers on ruminal pH, volatile fatty acids, or digestibility of dry matter or fiber were noted. Cows responded favorably during hot weather to potassium supplementation at 1.53% of the diet, but with high dietary potassium, effects on other minerals must be considered. Chloride, although present above requirements in all diets, was greater in the highest potassium diet.     

Fat digestion in veal calves fed milk replacers low or high in calcium and containing either casein or soy protein isolate

The hypothesis tested was that the inhibitory effect of dietary soy protein versus casein on fat digestion in veal calves would be smaller when diets were fed with high instead of low calcium content. Male calves, 1 wk of age, were fed 1 of 4 experimental milk replacers in a 2 x 2 factorial design. There were 19 animals per dietary group. The milk replacers contained either casein or soy protein isolate as variable protein source and were either low or high in calcium. Body weight gain was not significantly affected by the experimental diets. Soy protein isolate versus casein significantly reduced apparent fat digestibility. High versus low calcium intake also depressed fat digestion. The protein effect was smaller (2.9% units) for the high than the low calcium diets (3.6% units), but the interaction did not reach statistical significance. Soy protein isolate versus casein raised fecal bile acid excretion and so did high versus low calcium intake. The difference in bile acid excretion between the soy and casein containing diets was significantly greater for the high than low calcium diets. The absorption of phosphorus, calcium, and magnesium was higher for the casein diets than for the soy-containing diets. This study shows for the first time that soy protein isolate versus casein depressed fat digestion and raised fecal bile acid excretion in veal calves.