Casein Concentration Research Articles

Casein Micelles as Nanocarriers for Benzydamine Delivery.

The aim of the present work was to optimize the process parameters of the nano spray drying technique for the formulation of benzydamine-loaded casein nanoparticles and to investigate the effect of some process variables on the structural and morphological characteristics and release behavior. The obtained particles were characterized in terms of particle size and size distribution, surface morphology, production yield and encapsulation efficiency, drug-polymer compatibility, etc., using dynamic light scattering, scanning electron microscopy, differential scanning calorimetry, and Fourier transformed infrared spectroscopy. Production yields of the blank nanoparticles were significantly influenced by the concentration of both casein and the crosslinking agent. The formulated drug-loaded nanoparticles had an average particle size of 135.9 nm to 994.2 nm. Drug loading varied from 16.02% to 57.41% and the encapsulation efficiency was in the range 34.61% to 78.82%. Our study has demonstrated that all the investigated parameters depended greatly on the polymer/drug ratio and the drug release study confirmed the feasibility of the developed nanocarriers for prolonged delivery of benzydamine.

Enhanced Anti-E. coli ST131 Metabolites Production by a Novel Streptomyces sp. CMB51 Strain Isolated from a Coal Mininig Soil Using Statistical Optimization

Actinobacteria strains isolated from coil mining soil of Bechar region, Algeria, were evaluated for their antimicrobial potential against pathogenic germs particularly against uropathogenic multiresistant Escherichia coli ST131. Of the 119 isolates, 82 exhibited potent antimicrobial properties. The strain that showed maximum inhibition against E. coli ST131 was further screened toward nine bacterial pathogens and identified based on morphological, physiological and 16S rRNA gene sequencing. The isolate was related to the genus Streptomyces with 99.46% sequence similarity to Streptomyces klenkii strain S2704T and assigned as Streptomyces sp. CMB51. To achieve maximum metabolites production, significant process parameters were optimized through response surface methodology employing Plackett–Burman and Central Composite designs. In PBD experiments, starch and casein concentrations, incubation time and initial pH value emerged as the most significant affecting the output of anti-E. coli ST131 activity. The composition of the final optimized medium was soluble starch concentration of 5.31 g/L, casein concentration of 0.45 g/L, 3 days incubation time and 8.41 initial pH value. The optimization resulted an antibacterial activity of 13 mm which was in close accordance with the predicted value of 13.60 mm recording 18.18% increase. The chosen method was efficient for further investigations of the production of anti-E. coli ST131 metabolites.

Growth rate and behaviour in separated, partially separated or non-separated kids and the corresponding milk production of their mothers.

We address the hypothesis that keeping kids and mothers together would have positive effects on the milk composition of the mother and the behaviour of the kids. Kids were either permanently separated (SEP), daily separated between 7.30 and 15 h (DAY-SEP) or kept with mothers 24 h/d (NON-SEP). The NON-SEP kids were only allowed to suckle one teat. All kids had similar growth rate throughout the study (lactation days 5-70). DAY-SEP kids spent 24% of their time with their mother at both ages. NON-SEP spent only 15% of the time with their mothers at 2 weeks of age and this increased to 28% at 2 months of age. NON-SEP kids showed more hiding behaviour at 2 weeks and SEP were more active alone, at both 2 weeks and 2 months, compared to the other treatments. The mean available milk yield and fat concentration were higher in DAY-SEP goats (2420 g ± 119 g and 4.9 ± 0.1%) compared with NON-SEP goats (2149 ± 79 g and 4.4 ± 0.1%). There were no differences between DAY-SEP and NON-SEP goats in total protein, lactose, or casein concentrations. Based on these data it was estimated that 7.1 kg milk was needed to produce 1 kg semi-hard cheese in DAY-SEP goats and 7.5 kg in NON-SEP goats, respectively. When comparing milk yield and composition between udder halves, the milk yield was, as expected, higher from the machine milked teat than from the suckled one in the NON-SEP goats but there was no difference between right and left udder halves in DAY-SEP goats. Milk fat concentration varied between teats at morning and afternoon milkings in NON-SEP goats, but there was no difference in milk fat between udder-halves in DAY-SEP goats. In conclusion, the kid growth rate was similar in all treatments, however, an altered behaviour was seen in permanently separated kids (SEP). The results show that it is possible to have a high milk yield and fat concentration with one kid together with the dam.

Effects of varying casein and pectin concentrations on the rheology of high-protein cultured milk beverages stored at ambient temperature

Shelf-stable cultured milk beverages that have high protein levels can be difficult to successfully manufacture. With increasing protein level, rapid phase separation and gel formation occur in cultured beverages, which may not be prevented even with the inclusion of stabilizers such as high methoxy (HM) pectin. To limit protein aggregation in cultured milk beverages we investigated micellar casein as an interesting alternative to milk, due to the absence of whey proteins, which can contribute to increased gel strength in cultured products. In this study, micellar casein dispersed in ultrafiltered milk permeate was fermented to pH 4.1, blended with HM pectin, homogenized, thermally processed, and bottled for storage at ambient temperature for 6 mo. Utilizing response surface methodology with a central composite rotatable design, the protein and pectin contents were varied between 5 and 9% and 0.0 and 1.0%, respectively. The elastic modulus, loss tangent, and yield stress of these beverages were measured during storage to observe the extent of bond restructuring, whereas particle size and visual phase separation were measured to determine stability. Response variables were measured initially after thermally processing the beverages, and after 1 and 6 mo of storage at ambient temperature. All samples quickly formed gels after homogenizing, regardless of the pectin level. The stiffness (elastic modulus) of all samples increased throughout storage and was determined mainly by the protein content; however, the growth of elastic bonds over time was slowed with high levels of pectin. At 6 mo of storage, yield stress values were significantly lower for beverages with <7.5% protein when they were stabilized with ≥0.85% pectin. Prediction models for visual phase separation in beverages stored for 6 mo were significantly affected by the protein content, with increasing instability at lower protein levels. Models were used to identify optimal protein (<7.5%) and pectin (≥0.85%) concentrations to minimize the stiffness of gels during ambient storage. Samples in this optimized region were predicted to have low yield stress values and were easily fluidized by gentle shaking of the bottle at 6 mo.

Viscosity changes and gel formation during storage of liquid micellar casein concentrates

Our objective was to determine the effects of temperature and protein concentration on viscosity increase and gelation of liquid micellar casein concentrate (MCC) at protein concentrations from 6 to 20% during refrigerated storage. Skim milk (∼350 kg) was pasteurized (72°C for 16 s) and filtered through a ceramic microfiltration system to make MCC and replicated 3 times. The liquid MCC was immediately concentrated via a plate ultrafiltration system to 18% protein (wt/wt). The MCC was then diluted to various protein concentrations (6-18%, wt/wt). The highest protein concentrations of MCC formed gels almost immediately on cooling to 4°C, whereas lower concentrations of MCC were viscous liquids. Apparent viscosity (AV) determination using a rotational viscometer, gel strength using a compression test, and protein analysis of supernatants from ultracentrifugation by the Kjeldahl method were performed. The AV data were collected from MCC (6.54, 8.75, 10.66, and 13.21% protein) at 4, 20, and 37°C, and compression force test data were collected for MCC (15.6, 17.9, and 20.3% protein) over a period of 2-wk storage at 4°C. The maximum compressive load was compared at each time point to determine the changes in gel strength over time. Supernatants from MCC of 6.96 and 11.61% protein were collected after ultracentrifugation (100,605 × g for 2 h at 4, 20, and 37°C) and the nitrogen distributions (total, noncasein, casein, and nonprotein nitrogen) were determined. The protein and casein as a percent of true protein concentration in the liquid phase around casein micelles in MCC increased with increasing total MCC protein concentration and with decreasing temperature. Casein as a percent of true protein at 4°C in the liquid phase around casein micelles increased from about 16% for skim milk to about 78% for an MCC containing 11.6% protein. This increase was larger than expected, and this may promote increased viscosity. The AV of MCC solutions in the range of 6 to 13% casein increased with increasing casein concentration and decreasing temperature. We observed a temperature by protein concentration interaction, with AV increasing more rapidly with decreasing temperature at high protein concentration. The increase in AV with decreasing temperature may be due to the increase in protein concentration in the aqueous phase around the casein micelles. The MCC containing about 16 and 18% casein gelled upon cooling to form a gel that was likely a particle jamming gel. These gels increased in strength over 10 d of storage at 4°C, likely due either to the migration of casein (CN) out of the micelles and interaction of the nonmicellar CN to form a network that further strengthened the random loose jamming gel structure or to a gradual increase in voluminosity of the casein micelles during storage at 4°C.

High concentrations of casein proteins exacerbate radical chain reactions and increase the extent of oxidative damage

The co-existence of proteins, lipids and riboflavin (RF) in milk together with the harsh conditions encountered during processing (e.g. high temperatures, light exposure) results in oxidative damage. Proteins represent ~30 % of the dry mass of milk, with caseins accounting for ~80 % (28 g L−1). Due to their high abundance and amphiphilic nature, caseins are targets for both hydrophilic and lipophilic oxidants. Although caseins are key milk components, and highly abundant, most previous work has employed non-biological dilute solutions. In this work we have investigated oxidative modification of αs-, β- and κ-caseins elicited by AAPH-derived oxygenated radicals, or RF-mediated photo-oxidation, at both low and high protein concentrations, to determine whether and how oxidative damage and resulting structural modifications are modulated by the protein concentration. The data obtained demonstrate that the pathways leading to casein modification are dependent on both the protein concentration and the oxidant employed. AAPH-mediated oxidation was more efficient than RF-induced photo-oxidation, in respect to the number of moles of amino acid side-chains consumed per mole of oxidant generated, the extent of damage detected by SDS-PAGE, and immunoblot detection of oxidation products. Quantification of amino acid consumption and product generation, using UPLC and LC/MS, demonstrates the occurrence of short chain reactions, with the chain-length dependent on the protein concentration. LC/MS peptide mass mapping analyses provide data on the sites of modification. Molecular crowding, arising from high casein concentrations and casein-casein interactions, therefore favors the occurrence of radical chain events that enhance the extent of protein oxidative damage.

Acid-induced mixed methylcellulose and casein gels: Structures, physical properties and formation mechanism

In this study, caseins and methylcellulose (MC) were selected as building materials to prepare a class of mixed gels by adding glucono-δ-lactone (GDL) to induce the gelation of composite MC/casein systems, where the casein concentration was fixed at 8.0% (w/v) and the MC concentration varied from 0 to 1.0% (w/v). It was found that with increasing amount of MC addition (0–0.4%), the mixed gels exhibited a structural conversion from a casein-dominant gel network to a “water-in-water emulsion structure”, with the caseins as the continuous gelling phase and the MC as the dispersed phase; further MC addition (0.4–1.0%, w/v) caused a more significant phase separation phenomenon. The structural conversion was in consistent with the determination result of gel hardness. Furthermore, by a combination of confocal laser scanning microscope (CLSM) and rheological studies, the structural evolution process of the mixed gels was revealed to explore the underlying formation mechanism of the mixed gels.

Functionality of MC88- and MPC85-Enriched Skim Milk: Impact of Shear Conditions in Rotor/Stator Systems and High-Pressure Homogenizers on Powder Solubility and Rennet Gelation Behavior.

Milk protein concentrate (MPC) and micellar casein (MC) powders are commonly used to increase the protein concentration of cheese milk. However, highly-concentrated milk protein powders are challenging in terms of solubility. The research question was whether and how incompletely dissolved agglomerates affect the protein functionality in terms of rennet gelation behavior. For the experiments, skim milk was enriched with either MC88 or MPC85 to a casein concentration of 4.5% (w/w) and sheared on a laboratory and pilot scale in rotor/stator systems (colloid mill and shear pump, respectively) and high-pressure homogenizers. The assessment criteria were on the one hand particle sizes as a function of shear rate, and on the other hand, the rennet gelation properties meaning gelling time, gel strength, structure loss upon deformation, and serum loss. Furthermore, the casein, whey protein, and casein macropeptide (CMP) recovery in the sweet whey was determined to evaluate the shear-, and hence, the particle size-dependent protein accessibility. We showed that insufficient powder rehydration prolongs the rennet gelation time, leading to softer, weaker gels, and to lower amounts of CMP and whey protein in the sweet whey.

Edible film characteristics at different casein concentrations

The edible film is a coating material in the form of a sheet that is used as packaging to wrap a food product. The concentration of casein given as a base material can affect the characteristics of the edible film produced. The research objective was to determine the characteristics of the yield value, thickness and tensile strength of the edible film made using different casein concentrations. The study used 3 treatments of casein concentration, i.e., 7.5%; 8.5%, and 9.5%, respectively, and 3 replications each. The results showed that higher casein concentrations had significantly increased the edible file yield from 10.59% to 13.38. This measure was followed by the increase of thickness value of edible film produced ranging from 0.0534 to 0.0611 mm. Moreover, the high-level concentrations of casein used as material for the edible film produced a higher tensile strength value, reach 22.51 N at 9.5% casein. In conclusion, the use of casein as a material up t0 9.5% can increase the yield, thickness, and tensile strength of the edible film produced.

Structural characteristics of gluconic acid δ-lactone induced casein gels as regulated by gellan gum incorporation

The co-gelation phenomenon of caseins and gellan in yogurt-related products is usually observed, highlighting the possibility of developing mixed casein/gellan systems as a new type of food gels. In this study, mixed gellan/casein gels were prepared by adding different amounts of gluconic acid δ-lactone (GDL) to acidify gellan/casein mixtures at a fixed casein concentration (8.0%, w/v) and varying gellan concentrations (0–0.6%, w/v). It was found that both the gellan concentration and the GDL addition amount affected the gel microstructures and gel strength; with increasing gellan concentration, the mixed systems gradually exhibited a significant phase separation, accompanied by a structural transition from homogeneous, casein-dominant gel structure to a “water-in-water” emulsion structure (where the casein-enriched phase acted as the continuous phase and the gellan-enriched phase as the dispersed phase). A higher level of GDL addition slightly retarded but did not abolish the phase separation by inducing a quicker gelation process. Moreover, based on the prepared gel matrices, composite gellan/casein emulsion gels were successfully developed. Conclusively, our results indicate that gellan can be used to regulate the microstructures of casein-based gels, which may further pinpoint the possibility of using mixed gellan/casein systems to diversify food gel design strategies.

Low temperature structure tunability of zinc oxide nanostructures using milk protein casein

Spherical, flower and rod-like zinc oxide nanostructures have been successfully biosynthesized at 70 °C in the presence of milk protein casein through a simple precipitation method. The concentration of casein in an alkaline medium determines the structure of zinc oxide. The chemical synthesis of highly crystalline zinc oxide nanostructures is accomplished at relatively low processing temperature using casein. X-ray diffraction studies confirm the phase purity and crystalline nature of zinc oxide nanostructures. Morphological changes in the samples were identified through electron microscopic images. Casein linkage with the ZnO nanostructures was confirmed by Fourier Transform Infra-red spectroscopy. The role of casein on the morphological features has been explained on the basis of its self-assembling nature, copolymerization, and secondary structure formation. The effects of morphological change in the optical properties are studied using a UV-visible absorption and photoluminescence spectroscopy. The results indicate that casein is a good mediator for the morphology-controlled growth of nanostructures at moderately low temperatures.

A quantitative calcium phosphate nanocluster model of the casein micelle: the average size, size distribution and surface properties.

Caseins (αS1, αS2, β and κ) are the main protein fraction of bovine milk. Together with nanoclusters of amorphous calcium phosphate (CaP) and divalent cations, they combine to form a polydisperse distribution of particles called casein micelles. A casein micelle model is proposed which is consistent with the way in which intrinsically disordered proteins interact through predominantly polar, short, linear, motifs. Using the model, an expression is derived for the size distribution of casein micelles formed when caseins bind to the CaP nanoclusters and the complexes further associate with each other and the remaining mixture of free caseins. The result is a refined coat-core model in which the core is formed mainly by the nanocluster complexes and the coat is formed exclusively by the free caseins. Example calculations of the size distribution and surface composition of an average bovine milk are compared with experiment. The average size, size distribution and surface composition of the micelles is shown to depend on the affinity of the nanocluster complexes for each other in competition with their affinity for free caseins, and on the concentrations of free caseins, calcium ions and other salts in the continuous phase.

Effect of Temperature, Added Calcium and pH on the Equilibrium of Caseins between Micellar State and Milk Serum.

Micellar casein and casein monomers in milk serum are in a dynamic equilibrium. At temperature below 15–20 °C a considerable amount of casein monomers, β-casein in particular, is released from the casein micelle into the aqueous serum phase. This study investigates the effects of added calcium and related variations of pH on this peculiar equilibrium in order to minimize the amount of caseins in the serum and to better understand the casein permeation during microfiltration. The pH was varied in the range of 6.3 to 7.3 and the content of calcium was increased up to 7.5 mM by adding CaCl2. Upon equilibration, the milk was separated by ultracentrifugation and the amounts of protein in the supernatant were analyzed. It was shown that the addition of low amounts of calcium shifts the equilibrium towards the micellar casein phase and can, thus, lower the serum casein content induced at low temperatures. Relative to that, the adjustment of pH separately from the CaCl2 addition had a minor effect on casein concentration and composition in the serum.

Preparation and structural characteristics of composite alginate/casein emulsion gels: A microscopy and rheology study

Composite polysaccharide-protein emulsion gels are ubiquitous in real food systems, but the underlying formation mechanism has not been well understood. In this study, binary alginate/casein systems were selected as a template to prepare four types of composite gels, where the casein concentration was 8.0% (w/v) and the alginate (Alg) concentration varied (0.2, 0.4 & 0.75%, w/v). Based on the composite gel systems, the Alg/casein emulsion gels with 20% oil phase fraction (v/v) were further prepared by dispersing emulsified oil droplets into the binary polymer systems, followed by adding glucono-δ-lactone (GDL) to induce gelation. It was found that irrespective of the polymer types that were used to prepare and/or stabilize emulsions, the oil droplets were always located into the casein-dominant regions. At low Alg concentrations, the emulsion gels featured a casein-dominant network with small Alg-enriched liquid droplets entrapped inside; with increasing Alg addition, the emulsion gels tended to converse into a bicontinuous phase structure, as in the case of composite Alg/casein gel matrices (without oil droplets). Depending on emulsion preparation strategies, the incorporation of oil droplets also affected the phase separation rate and extent between the Alg and the caseins. Moreover, with increasing Alg concentration, the gelation time of the composite emulsion gels was shortened, possibly because a higher concentration of Alg exerted a more pronounced effect on promoting casein aggregation. Overall, our study is anticipated to not only give an insight into the formation of composite polysaccharide-protein emulsion gels, but also to offer a methodology for developing novel emulsion-gel related foods.

Gelation mechanism and physical properties of glucono-δ-lactone induced alginate sodium/casein composite gels

Designing composite food gels with polysaccharide-protein mixtures as building materials has recently attracted increasing attention in the food industry. By this way, it is feasible to produce the composite gels with hierarchical microstructures and desired physical properties. In this study, we fabricated a class of glucono-δ-lactone (GDL)-induced composite gels with a fixed casein concentration (8.0%, w/v) and varying alginate addition amounts (Alg, 0–1.0%, w/v). As the Alg concentration increased, the gel hardness was initially increased, but followed by a decreasing trend, which was corresponding to the structural transition of the composite gels. At low Alg concentrations (e.g., 0.1% Alg), the composite gel featured casein-dominant network; with increasing Alg addition (e.g., 0.2–0.5%), the caseins acted as the continuous gelling phase and the Alg served as the dispersed phase. When the Alg concentration was further increased (e.g., 0.75–1.0%), a bicontinuous phase structure was observed. In addition, it was found that with increasing Alg addition, the gel-setting time (Tgel) was monotonously decreased. Despite this, however, the structural evolution of the gels was still observed even after reaching the gelation point, which was dominantly ascribed to the electrostatic attraction between the two polymers that occurred at a pH range below the isoelectric point (pI) of the caseins. Overall, the composite Alg/casein systems may emerge as a promising template for designing novel gel-related foods.

The effect of nutritional management in early lactation and dairy cow genotype on milk production, metabolic status, and uterine recovery in a pasture-based system

High levels of milk production coupled with low feed intake cause negative energy balance in early lactation, especially in the first month postpartum (PP). Therefore, specific nutritional management at this time may improve nutritional and metabolic status with the possibility of contrasting genotypes responding differently. Thus, the objective of this study was to compare the effects of nutritional management strategies and dairy cow genotype on milk production, metabolic status, and some fertility parameters during early lactation in a pasture-based system. Sixty Holstein Friesian cows were blocked on parity and genotype [low-fertility high-milk (LFHM) and high-fertility low-milk (HFLM)] and were randomly assigned to 1 of 2 treatments in a 2 × 2 factorial arrangement, in a randomized complete block design based on calving date, previous 305-d milk yield, and precalving body condition score (BCS). The nutritional management treatments were: (1) ad libitum access to fresh pasture plus an allowance of 3 kg of concentrates per day (CTR, n = 30); and (2) ab libitum access to a tailored total mixed ration (TMR, n = 30). These diets were offered for the first 30 d PP. Following the first 30 d PP, cows fed TMR joined the CTR treatment and were managed similarly until 100 d PP. Blood samples were taken at d 7, 14, 21, and 28 PP to determine metabolic status. Milk samples for composition analysis were collected weekly and BCS assessed every 2 wk. Genotype had a significant effect on milk output, whereas LFHM had increased fat (+0.28 kg/d) and fat-plus-protein (+0.17 kg/d) yield in the first 30 d PP compared with HFLM cows. The LFHM group also exhibited higher protein and lactose yields over the first 100 d PP. Nutritional management did create significant differences in milk composition in the first 30 d: TMR cows had lower protein, milk urea nitrogen, and casein concentration and higher lactose concentration than CTR cows. Over the first 100 d PP, TMR cows had higher fat-plus-protein and lactose yields. Feeding TMR reduced concentrations of nonesterified fatty acids (-0.12 mmol/L) and β-hydroxybutyric acid (-0.10 mmol/L) compared with the CTR group. Cows fed TMR had smaller BCS losses from calving to 60 d PP. There was no effect of any treatment on uterine recovery. Cows in the LFHM group demonstrated greater milk production in the first 30 and 100 d in milk. These results demonstrate that feeding cows a TMR for the first month of lactation has positive effects on milk output, metabolic status, and BCS profile.

High concentrations of caseins in milk propitiate the occurrence of chain reactions, and propagation of oxidative damage

High concentrations of caseins in milk propitiate the occurrence of chain reactions, and propagation of oxidative damage

Enhancement of the Mechanical and Drug-Releasing Properties of Poloxamer 407 Hydrogels with Casein.

Topical therapy of local disease (e.g. skin) is advantageous over oral therapy since there is less systemic drug distribution (so fewer side-effects), no first-pass effect, etc. However, patient compliance with topical therapy can be poor as it may require many applications a day and can last months. Here we propose a topical controlled release formulation with thermoresponsive gelation at body temperature and improved adhesiveness, making it easier to remain in contact with the body. The formulation contains two excipients, poloxamer 407 (P407) and casein. Casein can modify the properties of the hydrogel through molecular entanglement. In addition, tissue reaction and drug release profile were evaluated. Changes in casein concentration affected adhesive strength, viscosity, mechanical properties and drug release, presumably by hydrophobic interactions between casein and P407. Two different concentrations of P407 were tested with two different concentrations of casein. Formulations containing 5% and 10% casein released 80% of model drug in 48h, while formulations without casein released the same fraction in around 24hhours. Formulations with 10% casein had almost twice the adhesive strength of those without casein. Addition of casein modified the mechanical properties and drug release rate of the hydrogel. There was no inflammation or injury after brief exposure in vivo.

Amino acid digestibility in corn distillers’ dried grains with solubles in pigs at different dietary levels of casein and test ingredient

Digestibility of amino acids (AA) in feed ingredients for pigs has been generally determined by feeding experimental diets containing test feedstuffs as a sole source of N, which may lead to the deficiency or imbalance of AA and hinder an accurate determination of digestibility values. Therefore, the addition of casein in experimental diets may ameliorate the potential negative effects of deficiency or imbalance of AA. In addition, the concentration of test feedstuffs in experimental diets may affect the digestibility of AA in test feedstuffs. Two experiments were conducted with corn distillers’ dried grains with solubles (DDGS) as the test feedstuff to determine the effects of increasing concentrations of casein in experimental diets on standardized ileal digestibility (SID) of AA in DDGS (experiment 1) and to investigate the effects of two concentrations of DDGS in experimental diets with or without the addition of casein on SID of AA in DDGS (experiment 2). In experiment 1, 20 barrows (initial BW = 45.3 ± 1.80 kg) surgically fitted with T-cannulas at the distal ileum were allocated to a quadruplicate 5 × 2 incomplete Latin square design with five diets and two periods. Four isonitrogenous diets containing increasing concentrations of casein from 0 to 165 g/kg with decreasing concentrations of DDGS from 466.8 to 0 g/kg and a N-free diet were prepared. The SID of AA, except for arginine, cysteine, and glycine, in DDGS linearly decreased (P < 0.05) with increasing concentrations of casein in experimental diets. Quadratic response (P = 0.023) was observed in the SID of lysine in DDGS when the concentration of casein in experimental diets increased. In experiment 2, the same 20 barrows (initial BW = 52.8 ± 2.99 kg) and experimental design as experiment 1 were used with different diets, which were prepared as a 2 × 2 factorial arrangement with the concentration of DDGS at 466.8 or 155.6 g/kg and that of casein at 0 or 110 g/kg. Regardless of the addition of casein, pigs fed experimental diets containing 466.8 g/kg DDGS had greater (P < 0.01) SID of indispensable AA, except for tryptophan, in DDGS than those fed diets containing 155.6 g/kg DDGS. In conclusion, the addition of casein in experimental diets did not affect the SID of AA in DDGS, whereas the SID of AA in DDGS decreased as the concentration of DDGS in diets decreased.

Effects of genotype and concentrate supplementation on milk composition and selected milk processability parameters in late-lactation spring-calving grazing dairy cows

A 2 × 2 factorial design experiment was conducted to investigate effects of cow genotype and concentrate supplementation (CS) on milk composition and processability. Four treatment groups (n = 12) were: (i) lower milk genotype (LM) offered no CS; (ii) LM + 2.7 kg dry matter (DM) CS; (iii) higher milk genotype (HM) offered no CS; and (iv) HM + 2.7 kg DM CS. Cows were +208 d in milk, grazed full time, and were offered 17 kg DM pasture cow-1 d-1. Increased milk yield resulted from HM cows and offering CS. The HM cows had decreased fat, protein and casein concentrations, while offering CS also decreased fat, protein and casein concentrations. Milk from cows offered CS had increased ethanol stability compared with cows offered pasture-only. In conclusion, HM cows and offering CS increased milk yield at the expense of components, but offering CS increased milk colloidal stability.