Proportion Of Casein Research Articles

Calibration of the near infra-red spectroscope for the casein content of Malagueña goats milk

In southern Spain the manufacture of goats milk cheese represents a large proportion of total the dairy production. Throughout the whole of Andalucia and the Malaga province the Malagueña breed of goat is of particular importance, due to its ability to produce high milk yields with a high protein content.The proportion of casein in milk is one of the most important factors determining the quantity and quality of cheese which can be made from that milk. It is therefore essential to be able to rapidly measure the milk casein levels prior to commencing the expensive process of cheese making.

Response of Lactating Cows to Methionine or Methionine Plus Lysine Added to High Protein Diets Based on Alfalfa and Heated Soybeans

Lactation diets based on wilted alfalfa silage and heated whole soybeans are common in the mid-western US. We examined the milk production response of multiparous Holstein cows to the addition of ruminally protected methionine at two percentages to a basal total mixed ration. An additional total mixed ration included both methionine and lysine supplementation. Sixteen Holstein cows in early lactation were used in a replicated 4 x 4 Latin square design with 21-d periods. Milk production, milk composition, and dry matter intake were determined for the last 5 d of each period. Milk production (41.5 kg/d), dry matter intake (25.9 kg/d), and milk fat concentration (3.26%) were unaffected by the supplementation of amino acids. The addition of methionine increased milk protein concentration and yield linearly. Each gram of methionine increased milk protein yield by 4g, and milk protein concentration increased from 2.89 to 2.99% with the addition of 10.5 g/d of methionine. The proportion of casein N in total milk N was unaffected by treatment. The addition of lysine did not elicit a response. Total mixed rations based on alfalfa haylage, heated soybeans, and animal proteins were clearly limited by their methionine content but were adequate in their lysine content.

Effects on Nutrient and Hormonal Profile of Long-Term Infusions of Glucose or Insulin Plus Glucose in Cows Treated with Recombinant Bovine Somatotropin Before Peak Milk Yield

Ten Holstein cows were treated with 30.9mg·d−1 of recombinant bST from 15 to 41 d of lactation. The Latin square design included three infusion periods of 6 d each with 3 d of rest between infusion periods. Infusions were physiological saline, glucose (50g·h−1), and insulin plus glucose (12.5IU·h−1 + 50g·h−1). Blood was collected continuously during the last 24h of each infusion period. Statistical analyses of data for energy balance, milk yield, and DMI were performed on the last 3 d of each infusion period. Production data before and after infusions (i.e., no recombinant bST) estimated that recombinant bST increased milk yield of cows infused with glucose and saline by 3.1 and 3.6kg·d−1, respectively. Net energy intake was not affected by infusion, but glucose infusion resulted in higher BW loss than did saline infusion (2.33 vs.0.08kg·d−1, respectively), and insulin plus glucose infusion resulted in BW gain (0.65kg·d−1). Milk yield was 39.9, 39.6, and 37.6kg·d−1 for cows infused with saline, glucose, and insulin plus glucose, respectively. The insulin plus glucose infusion increased milk protein 11 and 14% compared with response to saline and glucose infusions, respectively; no change occurred in the proportion of casein and whey proteins. Serum bST was increased 109% with exogenous recombinant bST. Serum IGF-I was lower for cows infused with glucose than for those infused with saline (21.03 vs. 27.44ng·ml−1) and increased to 46.55ng·ml−1 for cows infused with insulin plus glucose. Serum concentrations of insulin and glucose were 13.7 and 56.7, 18.5 and 61.9, and 30.5μIU·ml−1 and 39.4mg·dl−1 for cows infused with saline, glucose, and insulin plus glucose, respectively.The results of this study suggest that low concentrations of plasma insulin in early lactation may limit the IGF-I response to recombinant bST (uncoupling). Despite higher IGF-I, milk yield was lower, probably as a result of low blood glucose. These results suggest that, in early lactation, insulin is still anabolic because the BW gain of cows increased. However, milk yield was still higher than that for cows in late lactation with similar insulin concentrations.

Iodine metabolism in response to goitrogen induced altered thyroid status under conditions of moderate and high intake of iodine.

Metabolic experiments in rats were undertaken to relate excretory pattern of iodine and thiocyanate, with thyroid weight and the circulating levels of thyroxine, in response to moderate and high intake of iodine and under conditions of goitrogen induced altered thyroid status. On a moderate intake of iodine (by depriving diet of KI) 25 mg of thiocyanate or substitution of 1/3rd proportion of casein based diet with dry cabbage, could significantly reduce plasma thyroxine level by 60 days. Neither body weight nor the weights of liver, kidney, heart or spleen were affected due to exposure to goitrogens. A significant increase in thyroid weight as well as higher excretion of iodine and thiocyanate were evident in goitrogen-fed rats. Presence of high amounts of KI, to a certain extent, offered protection from adverse effects of the goitrogens. Semi quantitative assessment of thyroid, indicated hypofunctioning of thyroid with follicular hyperplasia in thiocyanate fed rats. These alterations were of moderate degree in response to cabbage feeding. These results emphasize that, moderate intake of iodine, adequate to meet iodine requirement, may not ensure normal functioning of thyroid in the presence of goitrogens.

Comparative study of proteins, peroxidase activity and N-acetyl-β-D-glucosaminidase activity in llama milk

Increased rearing of llamas in the USA has been associated with a need to supplement milk to orphaned or undernourished llama neonates. Ruminant milks and milk replacers are used, but there are few data comparing the nutrient composition and protective factors of llama milk to those of ruminant milks. We compared proteins in llama milk with those in cow, sheep, and human milks. Proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and visualized by Coomassie blue. Caseins were the predominant proteins in llama milk, as in cow and sheep milks. A considerably lower proportion of casein was identified in human milk. α-Lactalbumin was present in similar amounts in llama, sheep, and cow milks, with proportionately more α-lactalbumin in human milk. β-Lactoglobulin, the major whey protein of cows and sheep, was not detectable by this method in either llama or human milk. Gel profiles of llama milk contained a relatively higher proportion of a protein band co-migrating with lactoferrin compared with cow or sheep milk, but not as much as in human milk. We also compared the activities of peroxidase and N-acetyl-β-D-glucosaminidase in milks of the four species. Peroxidase activity in llama milk was more than ten times less than in cow or sheep milk. Activity of N-acetyl-β-D-glucosaminidase was more than 20-fold higher in llama milk than in milks of the ruminants. Activities of both enzymes in llama milk more closely resembled activities in human milk. Results of this study suggest that llama milk differs from cow and sheep milk in protein composition, and that the relative importance of protective factors, such as lactoferrin, peroxidase, and N-acetyl-β-D-glucosaminidase, in milk may be different for llamas compared with ruminants.

Extracellular matrix and mouse mammary cell function: Comparison of substrata in culture.

Cultured mammary cells depend on interaction with a substratum for functional differentiation, even in the presence of lactogenic hormones. Protein synthesis and secretion by mouse mammary epithelial cells on floating collagen gels and (EHS) matrix were compared. Cells were prepared by collagenase digestion of tissue from mid-pregnant mice. Protein synthesis was consistently greater in cells attached to EHS matrix, and was associated with proportionately higher rates of protein secretion into culture medium. Cells on EHS secreted protein into a luminal space formed within multicellular alveoluslike structures. Luminal secreted protein, extracted by EGTA treatment of cells in situ, constituted up to 40% of total secreted radiolabeled protein for cells on EHS matrix. The EGTA extract contained a higher proportion of casein and lactoferrin, whereas transferrin was predominately in the medium. This indicated that cells on EHS matrix had become polarized and were secreting proteins vectorially. In contrast, EGTA treatment of cells on floating collagen gels released virtually no radiolabeled protein, showing that mammosphere formation was a property of cells on EHS. These biochemical observations were supported by ultrastructural evidence. In EHS cultures, the proportion of secreted protein in the luminal fraction, but not the distribution of secreted proteins, changed with time. This suggests that there may be leakage out of the lumen, or intraluminal degradation of protein after secretion. Nevertheless, the results suggest that cellular organization into mammospheres on EHS matrix promotes synthetic and secretory activity. This system provides a useful model for investigation of the regulation of milk secretion.

Influence of dietary amino acid composition on thyroid function of juvenile rainbow trout, Oncorhynchus mykiss

The acute (3 days) and chronic (21 days) effects of dietary protein quality on thyroid function and growth parameters were studied in immature rainbow trout held at 12°C on a LD 12:12 light cycle. Five isocaloric (∼17.2 MJ digestible energy/kg dry diet) and isonitrogenous (45.1% protein) diets varying in amino acid composition were fed by hand once daily. The ration across all groups was consistent and varied between 1.0 and 1.5% of wet body wt. The dietary amino acid profiles mimicked that within the rainbow trout egg protein (EP), or whole-body protein (WBP), or they were varied widely by altering the proportions of casein and gelatin, i.e. HC/LG (high casein/low gelatin); MC/MG (medium casein/medium gelatin); LC/HG (low casein/high gelatin). Since these diets contained a chemo-attractant (FinnStim) to enhance food intake, a sixth diet, EP/NF (EP but lacking FinnStim), was used to ascertain FinnStim effects. Thyroid function was assessed from plasma levels of T 4 (L-thyroxine) and T 3 (3,5,3′-triiodo-L-thyronine), and from the activity of the hepatic microsomal T 4 5′-monodeiodinase (5′D) which converts T 4 to the more active T 3 form. After 3 days, plasma T 3 and T 4 titres were unaffected by diet, but 5′D activity was depressed by FinnStim and lowered in fish fed diets WBP and LC/HG relative to those fed diet MC/MG. After 21 days, plasma T 3 was uninfluenced by diet, but plasma T 4 was elevated in trout ingesting diet MC/MG. The 5′D activity was lower in fish fed diet WBP than in those receiving diets MC/MG and LC/HG. Final body weight was greater for fish fed diet EP/NF than for those fed diet LC/HG. Fork length was uninfluenced by diet, but the condition factor was depressed in fish fed diet LC/HG. Feed efficiency and percent protein deposited were depressed, whereas hepatosomatic index was elevated in fish fed diet LC/HG. It is concluded that thyroidal status, as judged primarily by hepatic 5′D activity, is influenced in trout both acutely and chronically by the profile of dietary amino acids. The diet high in gelatin content exerted the most consistent effects by depressing growth, condition factor, feed efficiency, and protein conversion into body protein, while simultaneously increasing both the mass of the liver and its 5′D specific activity. Further study is required to identify the particular amino acid(s) responsible for increasing hepatic 5′D potential under conditions of reduced growth.

Effects of abomasal protein and energy supply on wool growth in Merino sheep

The relative importance for wool growth of energy-yielding nutrients compared with amino acids required for incorporation into wool proteins was assessed in an experiment in which most nutrients were supplied via the abomasum. Nine nutritional treatments, providing three levels of protein (53, 99 and 145 g/day) to the intestines at three levels of energy (5.2, 7.5 and 9.7 MJ/day), were given to 12 Merino sheep during three consecutive periods of 3 weeks in a balanced lattice design. Abomasal nutrients consisted of varying proportions of casein, whole milk, glucose and glycerol. There was a large effect of protein supply on all components of wool growth, but there was no significant effect of energy. There was a significant interaction between the effects of protein and energy supply on diameter, length growth rate and volume of wool, but it was small relative to the main effect of protein. Extra energy appeared to enhance wool growth at the highest level of protein but reduce it at the lowest level of protein. The concentration of urea, cystine, methionine and other essential amino acids in plasma increased with protein level. Increasing energy supply reduced the concentration of urea and essential amino acids in plasma but not that of cystine or methionine. The experiment confirmed the major role of amino acid supply in controlling wool growth but indicated that there may be a small interaction with energy supply.

Pig colostrum and milk composition:comparisons between Chinese Meishan and US breeds

The composition of colostrum and milk from Chinese Meishan and American Yorkshire gills was characterized at farrowing (d 0), 24 h after farrowing (d 1), and on d 7 and 21 of lactation. Lactose concentrations were lower for Meishan vs. Yorkshire gills on d 0, 1, and 7, but not on d 21. Fat concentrations were higher for Meishan than for Yorkshire gilts at each sampling time, particularly on d 1 and 7. Total protein concentrations were similar on d 0 and 1, but lower for Meishan than for Yorkshire gilts on d 7 and 21. Milk proteins from Meishan gilts, Yorkshire gilts, and crossbred sows (Yorkshire × Hampshire × Landrace) were compared by polyacrylamide gel electrophoresis. Differences in size or relative proportion of caseins and the major whey proteins were not observed. Several high molecular weight whey proteins and a minor casein band were observed to segregate among breeds. These protein differences among breeds may be valuable markers in studies on lactating Mei-shan × Yorkshire crossbred animals. Results of this study suggest that colostrum and milk composition should not be a major limiting factor in survival and growth of piglets born to Meishan × Yorkshire crossbred gilts.

Relations entre les caractères physico-chimiques des laits et leur aptitude fromagère

cheese-making properties. In view of the increasing difficulties encountered in cheese-making, and with the intention of improving cheese yield and quality, the dairy industry and dairy research are determined to better investigate coagulation mechanism and better define parameters which determine the cheese-making quality of milk. A bibliographie review has been presented which shows the primordial influence on renneting properties of certain physico-chemical characteristics in milk. Forty-eight individual milk samples were taken and their physico-chemical composition, rennet and acid coagulating properties and cheese-making behavior in soft and fresh micro-cheese-making determined. Statistical analysis of data confirmed that cheese-making properties are mainly lniluenced by casein and calcium content, but are also influenced by lesser known factors such as casein proportion and micel/ar structure. Final/y, linear equations have been established for prediction of cheese yield.

Effect of Rumen-Protected Methionine and Lysine on Casein in Milk When Diets High in Fat or Concentrate are Fed

To examine the effect of supplying methionine and lysine on milk N composition, isoenergetic, isonitrogenous diets containing 50:50 with 3,9% added fat or 25:75 forage to concentrate with no added fat were fed with or without rumen-protected methionine and lysine to four primiparous and four multiparous early lactation (36 d in milk) Holstein cows in two 4 x 4 Latin squares. Diets contained 1.7 Mcal NE1 and were fed for ad libitum intake. Periods were 21 d. Rumen-protected methionine and lysine increased total N and casein N percentage with the 3.9% fat, but did not increase total N and casein N percentage with the diet without fat. Whey N percentage was greater with the no fat than with the 3.9% fat diet. Whey N percentage was not affected by adding amino acids. Nonprotein N percentage was greater for the diet with the 3.9% fat than with no fat. Proportions of casein N or whey N to total N were unaffected by treatments. Adding methionine and lysine to diets did not increase yields of total N and casein N. The 3.9% fat diet increased proportions of long-chain (C18:0 and C18:0) and decreased proportions of short- to medium-chain fatty acids (C8 to C16) in milk fat. Plasma nonesterified fatty acids and triglyceride concentrations were greater with the 3.9% fat as compared to the no fat diet. Methionine and lysine decreased plasma triglyceride concentrations with the 3.9% fat diet. Milk yields, DM intakes, and plasma glucose concentrations were unaffected by treatment.

Regulation of intracellular casein degradation by secreted milk proteins

Intracellular degradation of newly synthesised casein was measured by a pulse-chase method in freshly prepared goat mammary explants. After incubation in medium containing l-[5- 3H]proline, explants were washed and cultured again in unlabelled medium containing 5 mM proline; at intervals up to 24 h the amount of radiolabel incorporated in casein was measured. Tissue was obtained in week 33 of lactation after goats had been milked incompletely in one gland (the test gland) for 24 weeks; the contra-lateral (control) gland was milked normally. In explants from the control gland, casein was not degraded during or after secretion: l-[5- 3H]proline incorporated in casein increased to a maximum value which was maintained through the chase period. For four out of five goats, explants from the test gland showed a decrease in total [ 3H]casein radiolabel at 0–4 h of the chase, indicating that a proportion of casein was degraded during secretion. Intracellular casein degradation was also observed when control gland explants were cultured in chase medium containing a goat whey fraction known to inhibit casein production and milk secretion (Wilde, C.J. et al., (1987) Biochem. J. 242, 285–288). This suggests that the greater volume of residual milk left by incomplete milking reduced secretory efficiency, rendering casein susceptible to intracellular degradation, and that this occurred through the action of a secreted milk constituent, which acts as a chemical feedback inhibitor of milk secretion.

Bioavailability of lysine in milk-based infant formulas as determined by rat growth response method

Bioavailability of lysine in smaples of different forms (powder, liquid concentrates, ready-to-use, premature and/or hypoallergenic) of infant formulas (involving varying degrees of heat processing during preparation, and containing different proportions of casein and whey proteins) obtained from four manufacturers was determined by the rat growth response method using regression analysis (weight gain vs. lysine consumed). A wheat gluten basal diet adequate in all nutrients for rat growth except lysine (0.26%) was supplemented with graded levels of crystalline lysine (0.08, 0.16, 0.24, 0.32, 0.40, 0.48 and 0.64%, standard diets), or infant formulas providing 0.16% supplemental lysine (test diets). These diets were fed to weanling Sprague-Dawley rats for a period of 3 weeks. Bioavailability of lysine was determined after 1 and 3 weeks of test. Values for bioavailability of lysine in the infant formulas after 1 and 3 weeks of test were 78–95 and 84–97%, respectively. Diets containing liquid concentrate form of infant formulas had the lowest lysine bioavailability values. It is suggested that protein quality of liquid concentrates may be lower than that of powder and/or other forms of infant formulas prepared by the same manufacturer.

Relationships Between Milk Protein Polymorphisms and Major Milk Constituents in Holstein-Friesian Cows

Milk samples from 1,908 Holstein Friesian cows were phenotyped for genetic variants of αs1 -casein, β-casein, κ-casein, and β-lactoglobulin. The relationships between milk protein polymorphism and test day milk yield and composition were investigated. After adjustments were made for environmental effects of herd, parity number, month of test, stage of lactation, age of sample at testing, and somatic cell count, milk protein phenotypes were found to be associated with milk yield; concentrations in fat, protein, casein, and whey protein; and proportion of casein in protein. Higher test-day milk production was associated with αs1-casein BB, β-casein A1A3, κ-casein AA, and β-lactoglobulin AA phenotypes. Fat and protein concentrations were highest in milk from cows of αs1-casein BC, β-casein A1B, and κ-casein BB phenotypes. β-Lactoglobulin BB milk was associated with higher percentages of fat and casein and with lower percentages of total protein and whey protein. Based on desirable fat and casein contents of milk for cheese production, it would be advantageous to select for cows bearing κ-casein BB and β-lactoglobulin BB phenotypes.

Degradation of newly-synthesised casein in mammary explants from pregnant and lactating goats

1. 1. Casein degradation was measured by a pulse-chase method in explants from freshly-prepared from goat mammary tissue. 2. 2. An initial increase in l-[5- 3H]proline radioactivity incorporated in casein during the chase period was followed in some conditions by a decrease resulting from intracellular degradation of the major casein polypeptides. 3. 3. Differences in the proportion of casein degraded in explants cultured with or without prolactin suggested that the process was under hormonal control. 4. 4. Greater degradation of casein by explants obtained in late pregnancy and early lactation suggested that the process may affect net casein production in vivo.

Growth, digestion, and protein metabolism in neonatal pigs given diets containing whey as the predominant or only source of milk protein.

Milk substitutes containing ratios of casein/whey protein ranging from 80:20 to 0:100 were given to neonatal pigs. A ratio of 60:40 gave maximum growth rate, efficiency of feed utilization and nitrogen retention, and the lowest concentration of urea in blood plasma. This ratio is close to that in sow's milk, suggesting the hypothesis that in each species the milk may be adapted to the protein requirements of their young; by analogy, a casein/whey protein ratio of 20:80 in humanized milk formula might lead to more efficient protein utilization by the infant. In general, changes in the proportion of casein and whey proteins in the diet produced similar effects on the free amino acids in blood plasma as were found in clinical studies reported in the literature, providing further evidence of similarities in the protein metabolism of infants and neonatal pigs. The amount of nitrogen in the digesta remaining in the stomach at 1 h after a meal indicated that whey proteins empty from the stomach more rapidly than casein.

Growth, Digestion, and Protein Metabolism in Neonatal Pigs Given Diets Containing Whey as the Predominant or Only Source of Milk Protein

SummaryMilk substitutes containing ratios of casein/ whey protein ranging from 80:20 to 0:100 were given to neonatal pigs. A ratio of 60:40 gave maximum growth rate, efficiency of feed utilization and nitrogen retention, and the lowest concentration of urea in blood plasma. This ratio is close to that in sow's milk, suggesting the hypothesis that in each species the milk may be adapted to the protein requirements of their young; by analogy, a casein/whey protein ratio of 20:80 in humanized milk formula might lead to more efficient protein utilization by the infant. In general, changes in the proportion of casein and whey proteins in the diet produced similar effects on the free amino acids in blood plasma as were found in clinical studies reported in the literature, providing further evidence of similarities in the protein metabolism of infants and neonatal pigs. The amount of nitrogen in the digesta remaining in the stomach at 1 h after a meal indicated that whey proteins empty from the stomach more rapidly than casein.

Evaluation of the neonatal pig as a model for infant nutrition: effects of different proportions of casein and whey protein in milk on nitrogen metabolism and composition of digesta in the stomach.

Neonatal pigs were evaluated as a model for protein metabolism of infants. Milks were given in which the protein (15 or 30 g/liter) was supplied by casein and whey in the proportions of 80:20 or 40:60. Severe or moderate restriction of feed intake was also compared. Whey-predominant milks reduced the concentration of urea N in blood plasma and the proportion of urea N in urinary total N. These effects are consistent with most previously reported data from infants, particularly those of low birth weight. The efficiency of N retention was improved at the higher concentration of dietary protein. Whey-predominant milks also reduced the amount of N retained in the stomach. The magnitude of some of these effects was influenced by the level of feed intake. Total N retention reflected protein intake but was not affected by protein source. N retention determined by a balance procedure exceeded that calculated from carcass analysis, but the effect of protein intake was similar from either procedure.

Environmental Influences on Protein Content and Composition of Bovine Milk

A total of 24,405 individual milk samples from approximately 2,800 Holstein-Friesian cows in 63 dairy herds enrolled in the Quebec Dairy Herd Analysis Service program were analyzed monthly for protein, serum protein, casein, and somatic cell counts during 17 mo. Unadjusted means for protein, serum protein, and casein were 3.396%±.002, .687%±.001, and 2.708%±.002. Least squares analyses showed significant effects of calendar month of test, stage of lactation, age of cow, and somatic cell count on milk protein content and composition. Total protein, casein, and serum protein contents of milk showed a generally increasing trend from July to December. These components were highest during the first 10 days in lactation when means were 3.81%, 3.05%, and .76% and reached a minimum at 2 mo in lactation to give corresponding means of 3.08%, 2.46%, and .62%. The proportion of casein in milk protein decreased as cows became older. For every unit of increase in log somatic cell count there was an increase in protein content of .099%, mainly from change in the serum protein fraction. The same change in somatic cells would decrease ratio of casein to protein by 2.79%.

The Hypocholesterolemic Effect of Dietary Soy Protein in Rats

The serum cholesterol-lowering effect of dietary soy protein was examined in hypercholesterolemic rats. The inclusion of soy protein in a diet containing cholesterol and casein brought about a reduction in the serum cholesterol levels. A further cholesterol-lowering effect was achieved by increasing the proportion of soy protein in the diet. Conversely, the incorporation of increasing proportions of casein in the diet resulted in an elevation of the serum cholesterol concentration. Changes in serum cholesterol were predominantly reflected in different cholesterol concentrations in the very low density lipoproteins (VLDL). The concentrations of liver cholesterol paralleled the concentrations of cholesterol in the serum. Thus, this study clearly demonstrates that dietary soy protein is able to reduce the levels of cholesterol in the serum and the liver, whereas dietary casein has the opposite effect. Moreover, the cholesterolemic properties of both casein and soy protein can be enhanced by the incorporation of higher proportions of these proteins in the diet.casein soy protein serum cholesterol lipoproteins liver cholesterol rats