ABSTRACT: Bioactive peptides derived from milk proteins have attracted increasing interest due to their potential as natural sweet-tasting compounds. In this study, an integrated in silico strategy was developed to identify sweet peptides from milk proteins. The approach combined machine learning models capable of predicting both sweet and bitter taste properties to improve the accuracy of peptide selection. Peptides generated from virtual enzymatic hydrolysis were screened using 3 machine learning models. Candidates predicted to be sweet and nonbitter were virtually screened to evaluate their binding affinity to the human sweet taste receptor T1R2/T1R3. Peptides with favorable docking scores were further evaluated for their pharmacokinetic properties using computational prediction tools. Based on the combined results of docking and an absorption, distribution, metabolism, excretion, and toxicity assessment, 5 peptides (MDG, MKG, TSG, CDSS, and DSTT) were selected for further analysis. Molecular docking interaction analysis revealed that hydrogen bonding and π–π stacking were the predominant interaction modes at the binding site. Molecular dynamics simulations confirmed the structural stability of the 5 complexes, with MDG, CDSS, and DSTT showing reduced binding fluctuation and minimal receptor conformational changes, suggesting stronger binding stability. Electronic tongue analysis validated the presence of detectable sweet taste signals for all 5 peptides. Among them, MDG, CDSS, and DSTT demonstrated particularly stable interactions and clear sweetness responses, highlighting their potential as candidates for natural sweetener development. This study presents a practical computational framework for the efficient screening and evaluation of sweet peptides from milk protein sources. The proposed strategy may support the discovery of dairy-derived sweeteners with potential applications in sugar-reduced or functional dairy products.
Elizabeth R. Russell, Marina A.G. von Keyserlingk, Daniel M. Weary
ABSTRACT: Decades of research have helped inform practices on how to care for calves, but little is known about how well these practices are adopted on commercial dairy farms. The primary aim of this study was to describe rearing practices of dairy calves in British Columbia, Canada. Measures of calf growth are sometimes used to assess success in calf rearing, so a secondary aim was to describe methods used to assess calf growth on these farms. All 437 dairy farms in the province were invited to participate in a survey distributed via email from the British Columbia Ministry of Agriculture and Food from June to December 2023. A total of 63 completed responses were received (i.e., 14.4% of those invited). Milking herd size averaged (± SD) 167 ± 172 cows, and the primary breed was Holstein for 84.1% of respondents. Most (63.5%) farms housed calves individually before weaning; the remainder used either just social housing (groups of 2 or more; 25.4% of farms) or a combination of individual and social housing (11.1% of farms). Maximum milk allowance averaged 9.5 ± 2.7 L/d, with 86.4% of respondents offering >8 L/d. Teat feeding was used on 71.6% of farms, and 13.1% of farms used automated milk feeders. Two participants reported feeding calves via the dam or nurse cows. Weaning age averaged 75.8 ± 16.3 d, with calf age being the primary criterion for weaning. About half (52.4%) of farms reported monitoring calf growth, and 31.7% of farms reported having a target growth rate. Our results suggest that rearing practices are changing, in that calves are now often fed higher milk rations via a teat, and many farms use social housing. However, individual housing remains prevalent, suggesting research is needed to understand the barriers to adopting social housing on farms. Our findings also suggest the opportunity to improve methods for monitoring calf growth; improved measures may facilitate evidence-based evaluations of calf rearing and weaning protocols on farms.
ABSTRACT: Subclinical ketosis (SCK) is highly prevalent and easily overlooked, with insidious and slow progression of hepatic injury, often characterized by an imbalance in immune homeostasis. In nonruminants, macrophage polarization plays an important regulatory role in hepatic lipid accumulation, fibrosis, and inflammatory processes. Thus, we aimed to investigate the status of hepatic macrophage polarization in SCK cows and to corroborate its association with liver injury and inflammation. Twelve Holstein dairy cows (parity 2–4) were selected, and liver biopsy and blood were collected on the second week postpartum (10–14 d DIM). On the basis of serum beta-hydroxybutyric acid (BHBA) concentrations, selected cows were categorized into healthy (n = 6; BHBA <1.0 mM) and SCK (n = 6; 1.2 mM ≤ BHBA < 3.0 mM) groups. Serum biochemical parameters were measured using an automatic biochemical analyzer, which indicated higher serum levels of BHBA and nonesterified fatty acids and an upregulation of liver injury indicators (aspartate aminotransferase [AST], alanine aminotransferase [ALT], total protein, globulin) in SCK cows compared with healthy cows. The ELISA assays revealed that SCK cows displayed systemic low-grade inflammation, as demonstrated by increased serum levels of haptoglobin, serum amyloid A, TGF-β, IFN-γ, and IL-1β. Liver biopsies revealed pathological histological alterations, hepatic inflammation, and macrophage polarization status. Oil Red staining indicated steatosis, whereas Sirius red staining demonstrated mild extracellular matrix deposition in the liver of SCK cows. The expression of inflammatory response-related proteins (TLR4, p-NFκB, p-I-κB, NLRP3, and Caspase 1) was elevated in the liver of SCK cows, with the increased mean fluorescence intensity of NFκB further confirming the activation of the inflammatory pathway. Furthermore, the levels of pro-inflammatory factors, TNF-α and IFN-γ, were elevated in the tissue homogenate. Macrophage phenotypic changes in SCK cows were further explored based on the results of liver injury and inflammation. Compared with healthy cows, the protein and mRNA abundance of the macrophage marker CD68 in the liver of SCK cows was higher, along with an increased mean fluorescence intensity of CD68. The SCK cows also exhibited reduced mRNA expression of the Kupffer cell marker CLEC4F and elevated chemokine levels (CXCL1 and CCL2). As evidenced by greater protein and mRNA abundance of macrophage M1 polarization markers (iNOS, IL-1β, CD86, IL-6, IL-12b, and CCL3), higher fluorescence intensity of iNOS and CD86, and an increased number of CD68+/CD86+-positive cells observed via immunofluorescence, the macrophage polarization phenotype in the liver of SCK cows was predominantly M1. In contrast, the protein and mRNA abundances of M2 polarization markers (CD206, IL-10, and Arg1) were lower in SCK cows, accompanied by a reduced fluorescence intensity of CD206 and a lower number of CD68+/CD206+-positive cells. Overall, the present study revealed that the number of macrophages in liver is enhanced during subclinical ketosis and is dominated by pro-inflammatory macrophages (M1 macrophages). This could partly explain the increased risk of steatosis, fibrosis, and inflammatory response processes in these cows.
ABSTRACT: Accurate prediction of intestinal digestible flows of EAA (DigFlowEAA) is a crucial step for adequately balancing EAA supply to reduce the amount of CP fed to dairy cows, without compromising either milk production or the health status of the animals. The objective of this meta-analysis was to compare the performance of 3 dairy feed evaluation systems (FES) to predict DigFlowEAA (NRC; National Academies of Sciences, Engineering and Medicine [NASEM]; and Cornell Net Carbohydrate and Protein System version 6.5.5 [CNCPS]) in relation to observed net portal appearance (NPAobs) of EAA. Although the DigFlowEAA cannot be measured directly and none of the FES were designed to estimate the net portal appearance (NPA) of EAA, NPA could be predicted (NPApred) from estimations of DigFlowEAA minus the estimated metabolic fecal protein (MFP). This NPApred, however, would not include any oxidation for EAA or synthesis for Arg, a semi-EAA, occurring during the absorption process. Intuitively, the prediction errors should be smallest for the DigFlowEAA best predicted across the 3 FES and for the EAA not oxidized by the portal-drained viscera (PDV). The dataset included 83 NPAobs treatment means from 25 studies. To avoid type I error, mean and linear biases were considered biologically relevant if statistically significant and representing >5.0% of the observed mean (%obs.mean). The NPApred of branched-chain AA (BCAA) and Thr showed a similar pattern across the 3 FES, with all overpredicted relative to NPAobs (6%obs.mean to 27%obs.mean). The NPApred for the other EAA were more variable: (1) underprediction of Arg (9%obs.mean to 20%obs.mean) with NRC and NASEM, and Met (8%obs.mean) with NRC, (2) overprediction of Lys and Phe (5%obs.mean to 11%obs.mean) with NASEM, and His, Met and Trp (8%obs.mean to 14%obs.mean) with CNCPS, and (3) linear biases for Arg (7%obs.mean) with NASEM, and for His, Lys, Met, and Phe (5%obs.mean to 14%obs.mean) with CNCPS. In our previously reported meta-analysis, the mean and linear biases between observed and predicted EAA postruminal outflow were related to the site of digesta sampling (duodenal vs. omasal) for some EAA, but it was not possible to determine which sampling site was representative of the true supply of EAA to the cows. In an effort to solve this issue, predictions of NPA (except Trp) were recalculated removing the mean and linear biases observed in duodenal and omasal studies of our previous meta-analysis (NPArec_duo and NPArec_oma). Compared with NPApred, the pattern of BCAA and Thr remained overpredicted in NPArec_duo and NPArec_oma across the 3 FES. This strongly suggests oxidation of Ile, Leu, Val, and Thr by the PDV averaging, respectively, 12% (range 6% to 18%), 16% (range 14% to 17%), 24% (range 18% to 27%), and 19% (range 13% to 23%) of NPAobs across the 3 FES. The magnitude of PDV oxidation, however, would be related to the ratio of DigFlowEAA to digestible energy intake. The negative mean biases for Arg NPApred would suggest synthesis by the PDV. For the BCAA, Thr, and Arg, because of the uncertainty on the biological quantification of the differences between NPAobs and NPApred, the relative performance of each FES could not be assessed. Assuming no oxidation of the other EAA (i.e., His, Lys, Met, and Phe) by the PDV and an adequate estimation of MFP, their NPAobs indicate that the DigFlow of (1) Met is underpredicted by NRC, (2) Lys is overpredicted by NASEM, (3) His and Met are overpredicted with CNCPS, and (4) His, Lys, Met, and Phe present a linear bias with CNCPS, supporting similar observations on the postruminal EAA outflows from our previous meta-analysis. Based on current NPAobs studies and our previous meta-analysis on postruminal outflows of EAA, sampling digesta at the duodenum appears to be more representative of the true supply of EAA to the cows than sampling at the omasum.
ABSTRACT: Our objective was to evaluate how feeding colostrum at different volumes at the first feeding affects IgG absorption, gastric emptying, and calf behavior. Female Holstein calves (n = 88) were enrolled in a randomized block design to receive a single colostrum volume corresponding to 6%, 8%, 10%, or 12% of birth body weight (BBW). A subset of animals in 8 blocks (n = 32 calves) also received a gastric emptying marker acetaminophen (Ac) at a dose of 150 mg/kg metabolic body weight (BBW0.75). Colostrum was administered within 2 h of birth via esophageal tube feeder. Blood samples were collected before (0 h) and 24 h after feeding. For the calves receiving Ac, plasma samples were also collected at 2, 4, 6, 8, 10, and 48 h after feeding. Colostrum and 24-h serum IgG concentrations were measured using radial immunodiffusion. Apparent efficiency of absorption (AEA) was calculated from 24-h serum IgG concentrations. Plasma Ac concentration was determined using an enzymatic colorimetric assay, and the proportion of Ac remaining in the stomach (Acs) at 8 h was modeled. Audio and video recordings of calf behavior during the first 2 h after feeding were analyzed with a custom ethogram. Data analysis was performed using mixed models or Fisher's exact tests as appropriate. Results are reported as LSM with 95% CI unless otherwise specified. The mean (range) BBW of calves was 40.0 (31.8–49.1) kg. Pooled colostrum had a median (range) Brix value of 24.2% (21.2%–29.6%) and IgG concentrations of 86.7 g/L (73.2–121.1 g/L). Calves in the 6%, 8%, 10%, and 12% groups were fed median (range) colostrum volumes (L) of 2.3 (2.0–2.8), 3.1 (2.5–3.9), 4.0 (3.5–4.5), and 4.8 (4.2–5.6), respectively. The 24-h serum IgG concentrations (g/L) were lowest in the 6% group (28.8 [25.8–31.8]), increased to 37.4 (34.4–40.4) in the 8% group, and were highest in the 10% and 12% groups (41.1 [38.1–44.1] and 43.4 [40.4–46.4], respectively). Group differences were observed for AEA (%), which gradually declined with an increasing feeding rate and was highest in the 6% and 8% groups (47.8 [44.9–50.7] and 46.2 [43.3–49.0], respectively), declined to 41.0 (38.1–43.9) in the 10% group, and was lowest at 36.3 (33.5–39.2) in the 12% group. At 8 h, Acs (%) was 50.4 (43.8–57.0), 55.3 (49.2–61.5), 57.9 (51.8–64.0), and 65.5 (59.2–71.8) of the original dose in the 6%, 8%, 10%, and 12% groups, respectively. Group differences in behavior were identified for kicking, a colic-like behavior, which was observed only in the 10% (n = 21 kicks total) and 12% (n = 40 kicks total) groups. Feeding a single colostrum meal equivalent to 8% or 10% of BBW within 2 h after birth offers a compromise in terms of IgG absorption, gastric emptying, and calf behavior. A larger volume (12% BBW) resulted in marginal improvement in serum IgG concentration, reduced AEA and gastric emptying, and was associated with increased colic-like behaviors.
Guillermo Martinez-Boggio, Hugo F. Monteiro, Fabio S. Lima
et al.
ABSTRACT: The rumen microbiome is crucial for converting feed into absorbable nutrients used for milk synthesis, and the efficiency of this process directly affects the profitability and sustainability of the dairy industry. Recent studies have found that the rumen microbial composition explains part of the variation in feed efficiency traits, including dry matter intake, milk energy, and residual feed intake. The main goal of this study was to reveal relationships between the host genome, the rumen microbiome, and dairy cow feed efficiency using structural equation models. Our specific objectives were to (1) infer the mediation effects of the rumen microbiome on feed efficiency traits, (2) estimate the direct and total heritability of feed efficiency traits, and (3) calculate the direct and total breeding values of feed efficiency traits. Data consisted of dry matter intake, milk energy, and residual feed intake records, SNP genotype data, and 16S rRNA rumen microbial abundances from 448 mid-lactation Holstein cows from 2 research farms. We implemented structural equation models such that the host genome directly affects the phenotype (GP → P) and the rumen microbiome (GM → P), and the microbiome affects the phenotype (M → P), partially mediating the effect of the host genome on the phenotype (G → M → P). We found that 7% to 30% of microbes within the rumen microbial community had structural coefficients different from zero. We classified these microbes into 3 groups that could have different uses in dairy farming. Microbes with heritability <0.10 but significant causal effects on feed efficiency are attractive for external interventions. On the other hand, 2 groups of microbes with heritability ≥0.10, significant causal effects, and genetic covariances and causal effects with the same or opposite sign to feed efficiency are attractive for selective breeding, improving or decreasing the trait heritability and response to selection, respectively. In general, the inclusion of the different microbes in genomic models tends to decrease the trait heritability rather than increase it, ranging from −15% to +5% depending on the microbial group and phenotypic trait. Our findings provide more understanding to target rumen microbes that can be manipulated, either through selection or management interventions, in order to improve feed efficiency traits.
ABSTRACT: The purpose of this study was to investigate the effects of early castration and eucalyptus oil (EUC) supplementation on dry matter intake (DMI), growth performance, and immune response of Holstein calves. Fifty-six male Holstein calves 52 d old and with an initial body weight (BW) of 63.5 ± 5.27 kg were used. The animals were blocked by BW and randomly assigned into 1 of the 4 treatment groups in a randomized complete block design with a 2 (no castration vs. castration) × 2 (without vs. with EUC) factorial arrangement of treatments. The treatments were (1) uncastrated calves fed without EUC, (2) uncastrated calves fed 0.5 g/d EUC (EUC group), (3) castrated calves (steers) fed without EUC (castrated group), and (4) steers fed with 0.5 g/d EUC (castrated + EUC). The experiment was 8 wk long, including pre- and postweaning (weaned at 72 d). The EUC × castrated interactions were not significant for DMI, growth performance, nutrient digestibility, and immune response. Castration did not affect the DMI, final BW, average daily gain (ADG), or feed efficiency, except that the ADG was greater for bull calves than for steers at postweaning. Supplementation with EUC increased DMI pre- and postweaning and increased the ADG of weaned calves. Digestibility in the total digestive tract was not affected by castration (except for organic matter digestibility), whereas adding EUC improved the digestibility of dry matter, acid detergent fiber, and crude protein. Blood concentration of IL-6 at d 94 was decreased by feeding EUC. These results indicate that the EUC could be fed to either intact or castrated dairy calves to promote growth and health postweaning; castration before weaning may reduce ADG and cause inflammatory stress without affecting feed intake or feed efficiency.
ABSTRACT: Cow milk is an important source of food protein for children; however, it could lead to allergy, especially for infants. α-Lactalbumin (α-LA) and β-lactoglobulin (β-LG) from whey protein make up a relatively high proportion of milk proteins and have received widespread attention as major allergens in milk. However, few studies have identified the epitopes of both proteins simultaneously. In this study, ImmunoCAP and indirect ELISA were first used for detection of sIgE to screen sera from allergic patients with high binding capacity for α-LA and β-LG. Subsequently, the mimotopes was biopanned by phage display technology and bioinformatics and 17 mimic peptide sequences were obtained. Aligned with the sequences of α-LA or β-LG, we identified one linear epitope on α-LA at AA 11–26 and 5 linear epitopes on β-LG at AA 9–29, AA 45–57, AA 77–80, AA 98–101, and AA 121–135, respectively. Meanwhile, the 8 conformational epitopes and their distributions of α-LA and β-LG were located using the Pepitope Server. Finally, glutamine and lysine were determined as common AA residues for the conformational epitopes both on α-LA and β-LG. Moreover, we found the addition of mouse anti-human IgE during the biopanning process did not significantly affect the identification of the epitopes.
M. Zhou, P.W.G. Groot Koerkamp, T.T.T. Huynh
et al.
ABSTRACT: The effects of ambient temperature (AT) on total evaporative water loss from dairy cows at different relative humidity (RH) and air velocity (AV) levels were studied. Twenty Holstein dairy cows with an average parity of 2.0 ± 0.7 and body weight of 687 ± 46 kg participated in the study. Two climate-controlled respiration chambers were used. The experimental indoor climate was programmed to follow a diurnal pattern with AT at night being 9°C lower than during the day. Night AT was gradually increased from 7 to 21°C and day AT was increased from 16°C to 30°C within an 8-d period, both with an incremental change of 2°C/d. The effect of 3 RH levels with a diurnal pattern were studied as well, with low values during the day and high values during the night: low (day, 30%; night, 50%), medium (day, 45%; night, 70%), and high (day, 60%; night, 90%). The effects of AV were studied during the daytime at 3 levels: no fan (0.1 m/s), fan at medium speed (1.0 m/s), and fan at high speed (1.5 m/s). The medium and high AV levels were only combined with medium RH. In total, there were 5 treatments with 4 replicates each. The animals had free access to feed and water. Based on the water balance principle inside the respiration chambers, the total evaporative water loss from dairy cows at a daily level was quantified by measuring the mass of water in the incoming and outgoing air, condensed water, added water from a humidifier, and evaporative water from a wet floor, drinking bowl, manure reservoir, and water bucket. Water evaporation from a sample skin area was measured with a ventilated skin box, and water evaporation, through respiration with a face mask. The results show that RH/AV levels had no significant effect on total evaporative water loss, whereas the interaction effect between RH/AV with AT was significant. Cows at a high RH had a tendency for a lower increasing rate of evaporative water loss compared with cows at a low RH (0.61 vs. 0.79 kg/d per 1°C increase of AT). Cows at medium and high AV levels had a greater increasing rate than cows at low AV (0.91 and 0.95 vs. 0.71 kg/d per 1°C increase of AT, respectively). The increase of evaporative heat loss from dairy cows was mainly a result of the increase in evaporation (of sweat) from the skin. The skin water evaporation determined with the water balance method (less evaporation from respiration) and the ventilated skin box method showed no significant difference. The implication of this study is that cows at a high AT depend mainly on evaporative cooling from the skin. The ventilated skin box method, measuring only a small part of the skin during a short period during the day, can be a convenient and accurate way to determine the total cutaneous evaporative water loss from cows.
Robert Charles Schell, Ece Bulut, Hannah Padda
et al.
ABSTRACT: Concerns about antibiotic resistant infections in the United States have called for reduction of antibiotic use in livestock, including dairy cattle. Although effective in curbing antibiotic use, universal organic dairy farming would be impractical and unattainable due to its high land and premium demands. The US Department of Agriculture's organic certification, which completely eliminates antibiotic use in milk production, also raises animal welfare concerns, as it could discourage the use of antibiotics even to treat indicated diseases. Therefore, a proposed alternative for US consumers is a label indicating the responsible antibiotic use (RAU) – not complete elimination – that would minimize antibiotics more than conventional (unlabeled) milk and maximize animal welfare more than organic milk. Our goal was to determine consumers' (1) self-reported preference and (2) willingness to pay for this hypothetical RAU label of milk relative to existing substitutes in organic and unlabeled fluid milk. We conducted (1) a nationally representative survey of US adults and (2) a randomized non-hypothetical experimental Becker-Degroot-Marschak auction with real money and real milk. Although almost half of the survey participants (48.5%) responded that they would buy a RAU-labeled milk, consumers in the experimental auction refused to pay a significant premium for the milk compared with unlabeled milk (mean willingness to pay (95% confidence interval) per half-gallon: $1.92 ($1.65–$2.19) for RAU-labeled milk versus $1.86 ($1.58–$2.13) for unlabeled milk). These results suggest that consumers' survey-identified preferences for RAU-labeled milk could reflect either social desirability bias or a genuine preference for which, however, consumers simply will not pay a significant premium. The study provides preliminary data for future exploration of marketability of the proposed RAU label in the United States and demonstrates the benefits of using complementary survey and experimental auction approaches to understand the potential market for a new dairy product.
ABSTRACT: The demand for commercially available human breast milk has significantly increased in recent years. For various reasons, a significant amount of commercially available human breast milk is being adulterated with other types of milk. This fraudulent practice poses a threat to consumers' health due to potential adulterants such as cow milk, which may put the infant at risk due to intolerance or allergy. A direct sandwich anti-bovine IgG ELISA has been developed for the sensitive and specific detection of cow milk in adulterated human breast milk. This assay uses polyclonal anti-bovine IgG antibody as a capture antibody and monoclonal anti-bovine IgG-alkaline phosphatase antibody as a detection antibody. Once optimized, the assay was found to be highly sensitive, and specific to bovine IgG. The assay had no significant cross-reaction with human breast milk, indicating that it was highly specific. The anti-bovine IgG ELISA was able to detect the presence of cow milk in adulterated human breast milk with a detection limit of 0.001% cow milk. The developed assay was highly reproducible (coefficient of variation <10%). The developed direct sandwich anti-bovine IgG ELISA is simple, reliable, and reproducible, making it an ideal test for this purpose.
Martin Ptáček, Michal Milerski, Tereza Michlová
et al.
This study aimed to determine the potential of Wallachian sheep in quantitative and qualitative indicators of milk production under extensive conditions of the Western Beskids mountains. Milk samples were collected from the group of 38 non-dairying sheep selected from the basic 120-head flock. Ewes were monitored during four control days (from 27th April, the average 42nd day of lactation to 4th August, the average 142nd day of lactation) to cover the whole lactation period. Ewes were investigated for their milk production and for milk quantity parameter. Milk quality indicators included percentage estimation of milk components (fat, protein, casein, lactose, dry matter), somatic cell count (103 cells/ml), vitamin A and E content (mg/kg), and K, Mg, Ca, Zn, Cu (mg/kg) content. Milk production ranged from 1 017.37 g (early stage of lactation) to 416.87 g (late stage of lactation period). The milk contained high fat (6.06-8.44%) and protein (4.68-5.68%) percentages, low somatic cell count and favourable distribution of minerals and vitamins. In general, results of this study indicate a possibility for low-productive traditional grazing system with extensive sheep breeds not only for cultivating the area but also for the purpose of high nutritional food with beneficial aspect on human health.
Ahmed R.A. Hammam, Steven L. Beckman, Lloyd E. Metzger
ABSTRACT: Concentrated micellar casein (CMC) is a high-protein ingredient that can be used in process cheese product formulations. The objectives of this study were to develop a process to produce CMC and to evaluate the effect of sodium chloride and sodium citrate on its storage stability. Skim milk was pasteurized at 76°C for 16 s and cooled to ≤4°C. The skim milk was heated to 50°C using a plate heat exchanger and microfiltered with a graded permeability (GP) ceramic microfiltration (MF) membrane system (0.1 μm) in a continuous feed-and-bleed mode (flux of 71.43 L/m2 per hour) using a 3× concentration factor (CF) to produce a 3× MF retentate. Subsequently, the retentate of the first stage was diluted 2× with soft water (2 kg of water: 1 kg of retentate) and again MF at 50°C using a 3× CF. The retentate of the second stage was then cooled to 4°C and stored overnight. The following day, the retentate was heated to 63°C and MF in a recirculation mode until the total solids (TS) reached approximately 22% (wt/wt). Subsequently, the MF system temperature was increased to 74°C and MF until the permeate flux was <3 L/m2 per hour. The CMC was then divided into 3 aliquots (approximately 10 kg each) at 74°C. The first portion was a control, whereas 1% of sodium chloride was added to the second portion (T1), and 1% of sodium chloride plus 1% of sodium citrate were added to the third portion (T2). The CMC retentates were transferred hot to sterilized vials and stored at 4°C. This trial was repeated 3 times using separate lots of skim milk. The CMC at d 0 (immediately after manufacturing) contained 25.41% TS, 21.65% true protein (TP), 0.09% nonprotein nitrogen (NPN), and 0.55% noncasein nitrogen (NCN). Mean total aerobic bacterial counts (TBC) in control, T1, and T2 at d 0 were 2.6, 2.5, and 2.8 log cfu/mL, respectively. The level of proteolysis (NCN and NPN values) increased with increasing TBC during 60 d of storage at 4°C. This study determined that CMC with >25% TS and >95% casein as percentage of TP can be manufactured using GP MF ceramic membranes and could be stored up to 60 d at 4°C. The effects of the small increase in NCN and NPN, as well as the addition of sodium chloride or sodium citrate in CMC during 60 d of storage on process cheese characteristics, will be evaluated in subsequent studies.
Sine Ozmen-Togay, Gunnur Gulkun, Nurcan Degirmencioglu
et al.
Probiotic dairy products must contain a certain level of live probiotic microorganisms at the time of consumption. The number of live microorganisms in kefir culture, which is a mixture of different microorganisms, may change during storage due to various factors. In this study, the effects of adding a novel ingredient coffee bean membrane (CSS-coffee silverskin), on the viability of microorganisms contained in kefir culture were investigated. For this purpose, CSS obtained from 2 different coffee varieties (Arabica and Robusta) was added to kefir samples at 3 different concentrations (0.5, 0.75 and 1.0%) at the beginning of fermentation. It was observed that especially the addition of CSS belonging to the Robusta variety significantly increased the viability of lactic acid bacteria (lactobacilli and lactococci) which accounted for 88-94.10 and 82.37-92.44% respectively. During the storage period of 28 days at 4 °C; it could be observed that kefir enrichment with CSS of both coffee varieties increased the viability of lactobacilli and lactococci after in-vitro digestion, depending on the rate of supplementation. Number of yeasts was decreased during the storage.
ABSTRACT: We evaluated the effects of supplemental calcium ammonium nitrate (CAN) fed to dairy cows on dry matter (DM) intake, nutrient digestibility, milk quality, microbial protein synthesis, and ruminal fermentation. Six multiparous Holstein cows at 106 ± 14.8 d in milk, with 551 ± 21.8 kg of body weight were used in a replicated 3 × 3 Latin square design. Experimental period lasted 21 d, with 14 d for an adaptation phase and 7 d for sampling and data collection. Cows were randomly assigned to receive the following treatments: URE, 12 g of urea/kg of DM as a control group; CAN15, 15 g of CAN/kg of DM; and CAN30, 30 g of CAN/kg of DM. Supplemental CAN reduced DM intake (URE 19.0 vs. CAN15 18.9 vs. CAN30 16.5 kg/d). No treatment effects were observed for apparent digestibility of DM, organic matter, crude protein, ether extract, and neutral detergent fiber; however, CAN supplementation linearly increased nonfiber carbohydrate digestibility. Milk yield was not affected by treatments (average = 23.1 kg/d), whereas energy-corrected milk (ECM) and 3.5% fat-corrected milk (FCM) decreased as the levels of CAN increased. Nitrate residue in milk increased linearly (URE 0.30 vs. CAN15 0.33 vs. CAN30 0.38 mg/L); however, treatments did not affect nitrite concentration (average: 0.042 mg/L). Milk fat concentration was decreased (URE 3.39 vs. CAN15 3.35 vs. CAN30 2.94%), and the proportion of saturated fatty acids was suppressed by CAN supplementation. No treatment effects were observed on the reducing power and thiobarbituric acid reactive substances of milk, whereas conjugated dienes increased linearly (URE 47.6 vs. CAN15 52.7 vs. CAN30 63.4 mmol/g of fat) with CAN supplementation. Treatments had no effect on microbial protein synthesis; however, molar proportion of ruminal acetate and acetate-to-propionate ratio increased with CAN supplementation. Based on the results observed, supplementing CAN at 30 g/kg of DM should not be recommended as an optimal dose because it lowered DM intake along with ECM and 3.5% FCM, although no major changes were observed on milk quality and ruminal fermentation.
ABSTRACT: Our objectives were to determine the level of milk-derived whey protein (MDWP) removal necessary to achieve no detectable sulfur/eggy flavor in ultrapasteurized fat-free micellar casein concentrate (MCC) beverages (6.5% protein) and in the same beverages containing 1 and 2% milk fat. Micellar casein concentrate with 95% MDWP removal was produced from skim milk (50°C) with a 3×, 3-stage ceramic microfiltration (MF) process using 0.1-µm pore size graded permeability membranes (n = 3). In experiment 1, MCC-based beverages at about 6.5% (wt/wt) true protein were formulated at a fat content of 0.15% fat (wt/wt) at 4 different levels of MDWP removal percentages (95.2%, 91.0%, 83.2%, and 69.3%). In experiment 2, a similar series of beverages at 3 MDWP removal percentages (95.2%, 83.2%, and 69.3%) with 0.1, 1, and 2% fat content were produced. The purity (or completeness of removal of whey protein by MF) of MCC was determined by the Kjeldahl method and sodium dodecyl sulfate (SDS)-PAGE. Sensory properties of beverages were documented by descriptive sensory analysis, and volatile sulfur compounds were evaluated using solid-phase microextraction followed by gas chromatography-triple quadrupole mass spectrometry. The purity of MCC measured by the Kjeldahl method (casein as a percentage of true protein) was higher after thermal treatment than before, whereas MCC purity evaluated by SDS-PAGE was unchanged by heat treatment. The purity of MCC had an effect on the flavor profile of thermally processed beverages at 6.5% protein made with fresh liquid MCC. No sulfur/eggy flavor was detected in MCC beverages when 95% of the MDWP was removed (MCC purity about 93 to 94%) from skim milk by microfiltration at 0.1, 1, and 2% fat. As the fat content of 6.5% protein beverages produced with MCC increased, sulfur/eggy flavor intensity and hydrogen sulfide concentration decreased. However, the effect of increasing milk fat on reducing sulfur/eggy flavor in MCC-based beverages at 6.5% protein was less than that of increasing MDWP removal from MCC. Sulfur off-flavors in neutral-pH dairy protein beverages can be mitigated by use of high-purity MCC or by incorporation of fat in the beverage, or both.
Birutė Šlyžienė, Lina Anskienė, Evaldas Šlyžius
et al.
The aim of this study was to estimate the relation between milking traits and somatic cell count with electrical conductivity of goat milk during different milking phases. The research was carried out in the herd of Czech White Shorthaired and Saanen goat breeds (n=323) with the help of the electronic milk flow meter LactoCorder®. The milk yield, milking duration, milking flow rate and electrical conductivity of milk in the different phases of milking showed the significant mean differences between the breeds. Almost all (except electrical conductivity during the initial time) investigated indicators of electrical conductivity had a significant positive correlation with SCC. The bimodality of milk flow was determined in 9.69 % of goats and associated with milk yield decrease and SCC increase (P<0.05). The results confirm that the milk flow curve data is a good tool to control milking traits of goats, to predict the prevalence of mastitis and, thus, to improve the health of the udder of goats.