Multi-criteria assessment of pea protein quality in rats: a comparison between casein, gluten and pea protein alone or supplemented with methionine.

The objective of this study was to assess the nutritional quality of pea protein isolate in rats and to evaluate the impact of methionine (Met) supplementation. Several protein diets were studied: pea protein, casein, gluten, pea protein-gluten combination and pea protein supplemented with Met. Study 1: Young male Wistar rats (n 8/group) were fed the test diets ad libitum for 28 d. The protein efficiency ratio (PER) was measured. Study 2: Adult male Wistar rats (n 9/group) were fed the test diets for 10 d. A protein-free diet group was used to determine endogenous losses of N. The rats were placed in metabolism cages for 3 d to assess N balance, true faecal N digestibility and to calculate the Protein Digestible-Corrected Amino Acid Score (PDCAAS). They were then given a calibrated meal and euthanised 6 h later for collection of digestive contents. The true caecal amino acid (AA) digestibility was determined, and the Digestible Indispensable Amino Acid Score (DIAAS) was calculated. Met supplementation increased the PER of pea protein (2·52 v. 1·14, P < 0·001) up to the PER of casein (2·55). Mean true caecal AA digestibility was 94 % for pea protein. The DIAAS was 0·88 for pea protein and 1·10 with Met supplementation, 1·29 for casein and 0·25 for gluten. Pea protein was highly digestible in rats under our experimental conditions, and Met supplementation enabled generation of a mixture that had a protein quality that was not different from that of casein.

Caseina em sistemas de produção de São Luis de Montes Belos, GO / Caseine in production systems in the São Luis de Montes Belos, GO

A caseína é encontrada no leite de vaca, perfazendo cerca de 80% do conteúdo proteico desse alimento, possuindo alto valor econômico para a indústria láctea. Objetivou-se avaliar o teor de caseína no leite de propriedades rurais que pertencem ao Arranjo Produtivo Lácteo (APL) de São Luís de Montes Belos, Goiás. Coletaram-se 158 amostras de leite de tanques de expansão de propriedades da região do APL. A determinação da composição de caseína foi realizada pelo método de infravermelho. Com os resultados obtidos foi determinada a frequência absoluta e relativa de amostras com teor de caseína consideradas em acordo ou desacordo com o preconizado pela literatura. Observou-se que 35,45% das amostras coletadas estavam em desacordo. Conclui-se que há necessidade da adoção de medidas relacionadas ao manejo nutricional e ou sanitário dos rebanhos para que se consiga um leite com qualidade.

Separation and determination of denatured alpha(s1)-, alpha(s2)-, beta- and kappa-caseins by hydrophobic interaction chromatography in cows', ewes' and goats' milk, milk mixtures and cheeses.

Caseins alpha(s1)-, alpha(s2)-, beta- and kappa- from raw cows', ewes' and goats' milk were separated and determined by hydrophobic interaction chromatography (HIC) by using a Propyl column (Eichrom) in the presence of 8.0 M urea in the mobile phase. The method is based on fast and easy solubilization of real raw samples by 4.0 M guanidine thiocyanate followed by the HIC analysis, without any preliminary precipitation or separation of the casein fraction. Elution conditions have been optimized by analyzing commercial single bovine standard caseins and their mixture. In the optimized chromatographic conditions the four casein fractions were separated in less than 45 min. A linear relationship between the concentration of casein and peak area (UV absorbance detector at 280 nm) has been obtained over the concentration range of 0.5 to 40 microM. The detection limit for alpha-, beta- and kappa-caseins ranged between 0.35 and 0.70 microM. The precision of the method was evaluated, the coefficient of variation for alpha-, beta- and kappa-casein determination ranging between 3.0 and 6.0%. The method has been validated by the analysis of reference skim milk powder (BCR-063R) certificated for total nitrogen content. The method was applied to commercial casein mixture and to the qualitative and quantitative analysis of casein fractions in unprocessed, raw cows', goats' and ewes' milk (10 samples analyzed for each species), in one sample of unprocessed buffalos' milk and in commercial cheeses (mozzarella, robiola, ricotta and stracchino). Binary mixtures of milk (cow/goat and cow/ewe) were also analyzed and the ratio between casein peak areas (alpha(s1)/kappa, alpha(s2)/beta, beta/kappa and alpha(s2)/alpha(s1)) of the HIC chromatograms was proposed and discussed in order to evaluate a possible application of this method to detect milk adulteration.

Nutrition disorders and immunologic parameters: study of the thymus in growing rats.

OBJECTIVES: We studied the effect of a low-quality dietary protein on cellular proliferation and maturation in the thymus of growing rats over time. METHODS: After weaning Wistar rats were fed a diet containing 6.5 g/100 g of corn flour for 6, 10, 18, and 45 d (M groups). For comparison, other rats were fed a diet containing 6.5 g/100 g of casein (Cas groups), and well-nourished age-matched control rats were fed a commercial laboratory diet (C groups). Food intake, body weight, thymus weight, total number of thymocytes, and the percentages of CD43(+) and Thy1(+) thymocyte phenotypic antigen determinants were measured. RESULTS: M versus Cas and C groups showed significant differences (P < 0.01) in body and thymus weights after 6 d of feeding, and the total number of thymocytes and the percentages of CD43(+) and Thy1(+) were significantly lower after 10 d of feeding. The results indicated that consuming a cereal diet for short or long periods causes thymus atrophy in growing rats, with significant reductions in the total number of T-cells concomitant with increases in the number of immature thymocytes. CONCLUSIONS: The data showed that, in addition to low-protein concentration, low-quality dietary protein is a limiting factor in certain steps of cellular intrathymic pathways, probably related to the requirement of specific amino acids for optimal immune response.

Thrice-daily milking throughout lactation maintains epithelial integrity and thereby improves milk protein quality.

Cows managed for extended lactations of 16 months duration were milked on a half-udder basis twice or thrice daily, commencing in lactation week 9. Mammary epithelial integrity (assessed by milk sodium : potassium ratio) was greater in the half-udder which was milked thrice daily. This difference was evident throughout the lactation but became greater after week 41. Milk protein composition was assessed during late lactation (52+/-3 weeks). Casein number (casein as a proportion of total protein) was significantly higher in half-udders milked thrice daily, as were the relative amounts of alpha- and beta-caseins, whilst those of kappa- and- caseins were reduced. Two days of inverted milking frequency (i.e. thrice-milked udder halves now milked twice, and vice versa) only partly reversed these differences. We concluded that thrice-daily milking will help to prevent or ameliorate the usual decline in milk processing quality associated with late lactation. Part of this effect is due simply to reduced exposure to proteolytic enzymes as a result of decreased storage time in the udder, but part is due to a better maintenance of epithelial tight junction integrity as lactation advances, which restricts leakage of proteolytic enzymes from serum into milk.

[The effect of different high riboflavin supplements during pregnancy and lactation on performance and erythrocyte glutathione reductase activity of rats]. / Zum Einfluss einer Unterschiedlich hohen Riboflavinversorgung in der Gravidität und Laktation auf Leistungsparameter und die Aktivität der erythrozytären Glutathion-Reduktase von Ratten.

In two experiments with 160 female Sprague-Dawley rats the influence of various dietary riboflavin supplementations during lactation and during pregnancy and lactation were examined on food intake, body mass, reproduction, hematologic profile and the erythrocyte glutathione reductase activity coefficient (EGR-AC). In the first trial rats were fed a semisynthetic, riboflavin-deficient diet, based on casein and corn starch with various riboflavin supplementations during lactation (0, 2, 4, 6, 8, 10, 12, 40, 400, 4000 mg riboflavin/kg diet). In the second experiment the rats received supplements of 1 and 20 mg riboflavin/kg diet, respectively, during pregnancy. After parturition each group was divided into three sub-groups with riboflavin supplementations during lactation of 1, 5 and 20 mg/kg diet, respectively. Both investigations ended at the 14th day of lactation. Food intake was decreased significantly by 25% and 11% in the groups without riboflavin supplementation or 1 mg riboflavin/kg diet. In the same groups body mass was reduced by 11% and 4%, respectively. With regard to the reproduction parameters the riboflavin supply influenced only the litter mass at the 14th day of lactation and only lactational supply was relevant. In both trials the results of the hematologic profile showed no differences. In riboflavin deficiency (0 or 1 mg riboflavin/kg diet, respectively) the EGR-AC was increased significantly to 1.9 and 1.8, respectively. At the supplementation of 4-5 mg riboflavin/kg diet EGR-AC reached a plateau of 1.45, which was not improved by higher supplements. Concerning the whole reproduction cycle (trial II) there was a stronger influence of the actual lactation-supply on EGR-AC, on the other hand a riboflavin deficiency in pregnancy could be compensated only partially by an optimal supply in lactation. Therefore, based on the parameter EGR-AC an optimal riboflavin supply is recommended for each part of the reproduction cycle. By means of EGR-AC also the riboflavin requirement for lactating rats was derived. Feeding a semisynthetic diet (17.4 MJ ME/kg DM, 20.8% crude protein in DM) a supplementation of 5-6 mg riboflavin/kg or a total content of 6-7 mg/kg diet is recommended.

Dairy proteins protect against dimethylhydrazine-induced intestinal cancers in rats.

The impact of different dietary protein sources (whey, casein, soybean, red meat) on the incidence, burden and mass index of intestinal tumors induced by dimethylhydrazine in male Sprague-Dawley rats was assessed. A purified diet (based on AIN-76A) with a fat concentration of 20 g/100 g and other proteins substituted for casein (20 g/100 g) was used. Whey and casein diets were more protective against the development of intestinal tumors than were the red meat or soybean diets, as evidenced by a reduced incidence of rats affected (P = 0.15), fewer tumors per treatment group (burden, P < 0.005), and a reduced pooled area of tumors (tumor mass index) that formed (P = 0.39). Intracellular concentration of glutathione, an antioxidant and anticarcinogenic tripeptide, measured in liver, was greatest in whey protein- and casein-fed rats and lowest in soybean-fed animals (P < 0.001). For other tissues (spleen, colon, tumor) the differences were not significant, although the whey-fed animals had the highest concentrations of glutathione (P = 0.8). Whey is a source of precursors (cysteine-rich proteins) for glutathione synthesis and may be important in providing protection to the host by stimulating glutathione synthesis. A positive correlation was observed between mean fecal fat concentrations for rats in each treatment group and large intestinal tumor burden (r2 = 0.898, P = 0.05). Fecal fat could be involved in aiding initiation and/or promotion of carcinogenesis. Whatever the mechanism(s), dairy proteins, and whey proteins in particular, offer considerable protection to the host against dimethylhydrazine-induced tumors relative to the other protein sources examined.

Hatchery waste: nutritional evaluation of non-hatched eggs.

Hen's non-hatched eggs were processed by boiling for 30 minutes, milling in a meat grinder, and drying at 60 degrees C with continuous ventilation. The product contained 36% of protein, 27% of ether extract, 17% of ash, 10% of calcium, and 0.6% of phosphorus. The quality of the protein was comparable to that of a reference casein and of fresh egg meal, as determined by protein efficiency ratio and apparent net protein utilization.

Effect of water of hydration on the measurement of the protein efficiency ratio of casein and soybean protein with rats.

The hydration of soybean protein or casein prior to mixing of the diet improves the apparent protein efficiency ratio (PER). The PER of soybean protein was improved more than that of casein, so that an increase in adjusted PER of soybean protein was observed also. The improvement did not appear to be associated with digestibility. It is theorized that some diets with dry protein isolates may be less acceptable to the rat due to the dusty nature of the isolate. Consequently, diets with such isolates may have a lower PER. The effect can be overcome by hydrating the protein isolates prior to mixing the diet.