Milk Protein Fractions Research Articles

The Influence of Crossbreeding on the Composition of Protein and Fat Fractions in Milk: A Comparison Between Purebred Polish Holstein Friesian and Polish Holstein Friesian × Swedish Red Cows

Background/Objectives: In this study, the differences in protein and fat bioactive components between the milk from purebred Polish Holstein Friesian (PHF) cows and PHF cows crossbred with Swedish Red (SRB) were investigated. The objective was to assess the impact of genetic variation on the nutritional quality of their milk. Methods: This study was conducted at the Warsaw University of Life Sciences’ (WULS) experimental dairy farm in Warsaw, Poland, and involved 60 primiparous cows divided into two groups: 30 PHF×SRB crossbred cows and 30 purebred PHF cows. All cows were housed in a free-stall system with an average lactation yield exceeding 10,000 kg/lactation. The milk composition analyses included total protein, casein, whey protein, fatty acid profiles, and vitamin content. Results: Milk from the PHF×SRB hybrids showed a significantly greater total protein content (3.53%) compared to that from the purebred PHF cows (3.28%). The casein content was higher in the hybrids’ milk (2.90%) than the purebreds’ milk (2.78%), while the whey protein levels were lower in the purebred milk (0.50%) than in the hybrid milk (0.63%). The hybrids exhibited higher concentrations of certain saturated fatty acids in their milk, while the purebreds’ milk contained greater amounts of beneficial unsaturated fatty acids and fat-soluble vitamins—E, D, and K. Conclusions: These results indicate that genetic selection through crossbreeding can enhance the nutritional quality of milk. The differences observed in protein, fatty-acid, and vitamin content underscore the role of the genotype in milk composition, suggesting that breeding strategies can optimize dairy products’ health benefits.

Effect of pore size and temperature on the behaviour of alpha-lactalbumin and the A and B genetic variants of beta-lactoglobulin during protein fractionation microfiltration

The aim of this study was to investigate the influence of membrane pore size and filtration temperature on six individual milk protein fractions (αS-CN, β- CN, κ-CN, α-LA, β-LG A, β-LG A) during the protein fractionation microfiltration process. Pasteurised skimmed milk was microfiltrated using two different pore sizes of spiral-wound membranes, with pore sizes of 0.2 μm and 0.5 μm, at temperatures of 15 °C and 45 °C respectively. The microfiltration process was carried out with a final volume reduction of 66% and a diafiltration volume of 120% (300 L) of the original feed (250 L). It was observed that neither the pore size nor the filtration temperature significantly (p<0.05) affected the permeation of the α-LA fraction. However, the permeation of the β-LG A and β-LG B fractions can be influenced by membrane pore size and filtration temperature, and the behaviour of the three whey protein fractions, A and B genetic variants of the β-LG and α-LA fractions differs significantly during the microfiltration process. The results of this study could form the basis for the development of new, unique tailor-made milk protein ingredients.

Utilization of retentates for white brined cheese production: comparative evaluation of physico-chemical and sensory properties

The aim of the present study is (1) to enhance the protein fraction in cheese milk through membrane filtration and consequently (2) to separate the majority of whey as ‘ideal whey’ prior to the production of white brined cheese, and (3) to explore the potential utilization of retentates in the production of white brined cheese. The chemical, physical, textural and sensory properties of cheeses produced from microfiltration (MF) retentates were characterized to investigate the effects of cross-flow MF on white brined cheese. Polyether sulfone (MP005) membranes featuring a pore diameter of 0.05 μm and polyvinylidene fluoride (MV020) membranes with a pore diameter of 0.20 μm were utilized. The assessed quality parameters of cheeses derived from polyethersulfone membrane (MP005) retentates were similar to the control (p > 0.05), whereas the cheese obtained from polyvinylidene fluoride membrane (MV020) retentates exhibited notable differences (p < 0.05) from the control. The traditional whey generated after cheese-making, which typically requires substantial on-site processing and/or treatment, was reduced by 3.5–6.7 times using the MP005 retentates. Simultaneously, 58–70% of the cheese milk (w/w) was separated as ideal whey before the cheese-making process. MF shows potential as an eco-friendly technology suitable for use in cheese production processes. The potential utilization of MP005 for enriching the protein content in cheese milk holds promise for white cheese production.

The Aggregated and Micellar Forms of β-Casein Purified from Donkey and Bovine Milk Present Potential as Carriers for Bioactive Nutritional Compounds.

In recent years, there has been a growing interest in the pure casein fraction of milk protein, particularly β-casein due to its physicochemical properties as well as its bio- and techno-functional properties. The utilization of self-assembled β-caseins from bovine origin as nanocarriers for the delivery of nutraceutical compounds or drugs has increased dramatically. Concerning β-caseins from other milk sources, the use of hypoallergenic donkey β-caseins as a potential delivery vehicle for nutraceutical hydrophobic compounds is beginning to generate interest. The present review deals with casein micelles models, bovine and donkey β-casein molecular structures, as well as their physical-chemical properties that account for their exploitation in nutraceutics and pharmaceutics. This review work suggests the possibility of developing delivery systems for hydrophobic bioactive compounds using β-casein purified from hypoallergenic donkey milk, highlighting the potential of this protein as an innovative and promising vehicle for enhancing the enrichment and bioavailability of various bioactive substances in food products.

Impact of genetic κ-casein variants (A, B, E) on chymosin-induced milk coagulation properties: Application of a new LC–MS-based genotyping method

This study evaluated the impact of κ-casein (κ-CN) protein phenotype (AA (n = 18), AB (n = 18), AE (n = 5), BB (n = 3)) in the raw milk of 44 individual Holstein cows from a single farm on coagulation properties using diffusion wave spectroscopy. κ-CN variants were analyzed using a newly developed LC–MS method in individual milk samples, and relative milk protein fractions were quantified by LabChip-analysis. κ-CN fractions expressed in the percentage of total milk protein, total casein, and β- and κ-CN were then calculated. The gross composition of the individual milk samples and variation between individual cows was analyzed and was rather large, as expected. Traits were analyzed using an ANCOVA model with pH as a covariate.Our results showed that mean percentages of κ-CN fractions increased for κ-CN phenotypes in the order AA < AE < AB < BB. Rennet coagulation time was slightly affected, but curd firmness was significantly affected by κ-CN phenotype (BB > AE > AB > AA) when controlling for pH.

Optimizing Feed Formulation Strategies for Attaining Optimal Nutritional Balance in High-Performing Dairy Goats in Intensive Farming Production Systems

Abstract Genetic factors play a pivotal role in shaping feed formulation strategies for dairy goats, influencing milk production, composition, and overall productivity through the modulation of genetic parameters and polymorphisms associated with milk protein fractions and yield. Moreover, environmental challenges, including heat stress and feed availability fluctuations, pose significant hurdles in achieving optimal nutrition and performance, necessitating precision livestock farming and the utilization of local by-products to mitigate their impact on herd health and productivity. In addition, nutritional interventions, such as supplement utilization and alternative feed incorporation, offer promising avenues for addressing specific deficiencies and enhancing overall performance, from fatty acid supplementation to herbal feed additives, while balancing rations to meet evolving nutritional needs and ensuring long-term sustainability remains paramount for optimizing herd nutrition, health, and performance in intensive dairy goat production systems. The aim of this study was to explore the multifaceted influences of genetic factors, environmental challenges, and nutritional interventions on feed formulation strategies and overall herd nutrition, health, and performance in intensive dairy goat production systems.

An attempt to identify milk protein fraction genotypes using unsupervised and supervised near-infrared spectroscopy methods

The aim was to evaluate near-infrared spectroscopy (NIRS) potential to discriminate among β-casein (CN), κ-CN and β-lactoglobulin (LG) genotypes to be used as an authentication method. A total of 168 milk samples with known genetic information for β-CN, κ-CN and β-LG were collected at the same farm and paired with the NIRS spectrum. Spectra were evaluated with an unsupervised method (principal component analysis, PCA) and a supervised method (partial least squares-discriminant analysis, PLS-DA). For the PLS-DA, data were split into a train (75%) and a test set (25%), and the variable in projection >1 criterion was applied to select informative wavelengths. Results obtained confirmed that milk quality was similar among genetic variants. For the PCA, the observed variance explained by the first two principal components was 94%, but samples were not clustered by their genotypes of β-CN (i.e. A1A2, A2A2), κ-CN (i.e. AA, AB, AE, BB, BE) and β-LG (i.e. AA, AB, BB). The best accuracy for the PLS-DA models was reached by β-CN (train and test set, 64%), followed by β-LG (train set, 56%; test set, 52%) and κ-CN (train set, 41%; test set, 36%). In conclusion, the PCA on milk spectra was not able to cluster β-CN, κ-CN and β-LG genotypes, but the PLS-DA models revealed promising results for β-CN and β-LG. It could be interesting to increase the number of samples to equilibrate genetic variants and to apply a sampling selection method before discarding the applicability of NIRS as an authentication method.

Changes in Milk Protein Functionality at Low Temperatures and Rennet Concentrations

This study aimed to evaluate the influence of low-concentration rennet on the chemical, rheological characteristics, and protein fractions of skim milk (SM) at 4 ± 1 °C. Skimmed milk (SM) was divided into four lots of 500 mL, and diluted rennet (1:10,000) was added at different levels at 4 ± 1 °C. The treatments included control (no rennet), T1 (0.001 mL/rennet), T2 (0.01 mL rennet), and T3 (0.1 mL rennet) treatments, which were incubated for 24 h. The sampling was performed at 0, 1, 2, 6, 12, and 24 h, and the SM after incubation time was heated to 73 °C/16 s to denature the rennet enzyme. Skim milk samples (SMS) (control and rennet-added samples) were evaluated for proximate composition, capillary gel electrophoresis (CGE), hydrodynamic diameter, zeta potential, and rheology at 0, 1, 2, 6, 12, and 24 h. Foaming ability, foaming stability, water-holding capacity (WHC), oil emulsifying activity (OEA), and emulsion stability (ES) were performed at 0, 12, and 24 h of incubation time. There was a significant (p &lt; 0.05) increase in non-proteins by 0.50% and in non-casein nitrogen by 0.81% as incubation progressed. The results showed that aggregation or curd was not formed during storage time. The CGE data indicated that increasing the rennet concentration had a significant (p &lt; 0.05) effect on decreasing κ-CN, and breakdown increased at higher levels of rennet usage. There was a significant (p &lt; 0.05) increase in the hydrodynamic diameter and a decrease in the zeta potential values in rennet-added samples at the end of the incubation time (24 h). The rheological results showed no changes in the storage modulus (G′), loss modulus (G″), or viscosity values. Increasing the rennet amount and storage time led to a significant (p &lt; 0.05) decrease in the foaming ability and foaming stability and a significant (p &lt; 0.05) increase in the oil emulsifying activity and emulsion stability of rennet-added SMS. This study concluded that milk protein functionality can be changed without aggregating or curd formation, and rennet milk can be processed.

To study the anabolic aspects of lactation in cows in connection with the intensity of ketogenesis in the new body period

The article discusses the results of a study of the milk productivity of cows in connection with the content of beta-hydroxybutyric acid in the blood during the new calving period. The studies were carried out on highly productive full-aged cows of the second and third lactation. The animals were divided into three groups according to the content of beta-hydroxybutyrate - up to 1.0 mmol/l; from 1.0 to 2.0 mmol/l and over 2.0 mmol/l. It has been established that an increase in the content of ketones in the blood is associated with hypoglycemia. Cows with increased levels of beta-hydroxybutyric acid at the beginning of lactation showed higher daily milk yields over a five-month period of observation. In the fourth and fifth months of lactation, the milk yield of these cows was higher than in groups 1 and 2 by 14.6-15.8% and 18.5-20.1%, respectively. In addition, the total yield of fat in this group is greater than in the first and second - by 12.8% and 10.7%, protein - by 9.7% and 11.2%, and lactose - by 8.5% and 13.5%, respectively. A calculation indicator was proposed - the lactation anabolism index, which is calculated using daily milk yield, mass fraction of milk protein and urea concentration. An increase in this index indicates the activation of anabolic reactions, a decrease indicates a surge in catabolic processes. An increase in the lactation anabolism index was found in cows of the third group at 4-5 months of lactation with a significant increase of 44.8-45.8% in comparison with groups 1 and 2. A high metabolic potential for further productive lactation was established in cows that had increased concentration of beta-hydroxybutyric acid in the new calving period.

Molecular binding mechanism and novel antidiabetic and anti-hypertensive bioactive peptides from fermented camel milk with anti-inflammatory activity in raw macrophages cell lines.

The investigation was to determine the effect of camel milk fermented with Limosilactobacillus fermentum KGL4 (MTCC 25515) on ACE-inhibiting, anti-inflammatory, and diabetes-preventing properties and also to release the novel peptides with antidiabetic and anti-hypertensive attributes with molecular interaction studies. Growth conditions were optimised on the basis of total peptide production by inoculating the culture in camel milk at different rates (1.5, 2.0, and 2.5%) along with different incubation periods (12, 24, 36, and 48h). However, after 48h of fermentation with a 2.5% rate of inoculum, the highest proteolytic activity was obtained. Reverse phase high-pressure liquid chromatography (RP-HPLC) was used to calculate the % Rpa from permeates of 3kDa and 10kDa fractions. Molecular weight distributions of fermented and unfermented camel milk protein fractions were compared using SDS-PAGE. Spots obtained from 2D gel electrophoresis were separated on the basis of pH and molecular weight. Spots obtained from 2D gel were digested with trypsin, and the digested samples were subjected to RP-LC/MS for the generation of peptide sequences. The inhibition of tumour necrosis factor alpha, interleukin-6, and interleukin-1 during fermentation was studied using RAW 264.7 macrophages. In the study, fermented camel milk with KGL4 (CMKGL4) inhibited LPS-induced nitric oxide (NO) production and pro-inflammatory cytokine production (TNF-α, IL-6, and IL-1β) by the murine macrophages. The results showed that the peptide structures (YLEELHRLNK and YLQELYPHSSLKVRPILK) exhibited considerable binding affinity against hPAM and hMGA during molecular interaction studies.

Increasing Performance of Spiral-Wound Modules (SWMs) by Improving Stability against Axial Pressure Drop and Utilising Pulsed Flow.

Spacer-induced flow shadows and limited mechanical stability due to module construction and geometry are the main obstacles to improving the filtration performance and cleanability of microfiltration spiral-wound membranes (SWMs), applied to milk protein fractionation in this study. The goal of this study was first to improve filtration performance and cleanability by utilising pulsed flow in a modified pilot-scale filtration plant. The second goal was to enhance membrane stability against module deformation by flow-induced friction in the axial direction ("membrane telescoping"). This was accomplished by stabilising membrane layers, including spacers, at the membrane inlet by glue connections. Pulsed flow characteristics similar to those reported in previous lab-scale studies could be achieved by establishing an on/off bypass around the membrane module, thus enabling a high-frequency flow variation. Pulsed flow significantly increased filtration performance (target protein mass flow into the permeate increased by 26%) and cleaning success (protein removal increased by 28%). Furthermore, adding feed-side glue connections increased the mechanical membrane stability in terms of allowed volume throughput by ≥100% compared to unmodified modules, thus allowing operation with higher axial pressure drops, flow velocities and pulsation amplitudes.

Detection of the β-lactoglobulin genotype in zebu cattle (Gangatiri) milk using high-resolution accurate mass spectroscopy.

We studied the genetic polymorphism of beta-lactoglobulin (β-Lg) whey protein in Gangatiri zebu cows for this Research Communication. The polymorphic nature of milk protein fractions and their association with milk production traits, composition and quality has attracted several efforts in evaluating the allelic distribution of protein locus as a potential dairy trait marker. Genetic variants of β-Lg have highly significant effects on casein number (B > A) and protein recovery (B > A) and also determine the yield of cheese dry matter (B > A). Molecular techniques of polyacrylamide gel electrophoresis and high-resolution accurate mass-spectroscopy were applied to characterize the β-Lg protein obtained from the Gangatiri breed milk. Sequence analysis of β-Lg showed the presence of variant B having UniProt database accession number P02754, coded on the PAEP gene. Our study can provide reference and guidance for the selection of superior milk (having β-LgB) from this indigenous breed that could potentially give a good yield of β-Lg for industrial applications.

In vitro and in silico studies for the identification of anti-cancer and antibacterial peptides from camel milk protein hydrolysates.

Today, breast cancer and infectious diseases are very worrying that led to a widespread effort by researchers to discover natural remedies with no side effects to fight them. In the present study, we isolated camel milk protein fractions, casein and whey proteins, and hydrolyzed them using pepsin, trypsin, and both enzymes. Screening of peptides with anti-breast cancer and antibacterial activity against pathogens was performed. Peptides derived from whey protein fraction with the use of both enzymes showed very good activity against MCF-7 breast cancer with cell viability of 7.13%. The separate use of trypsin and pepsin to digest whey protein fraction yielded peptides with high antibacterial activity against S. aureus (inhibition zone of 4.17 ± 0.30 and 4.23 ± 0.32 cm, respectively) and E. coli (inhibition zone of 4.03 ± 0.15 and 4.03 ± 0.05 cm, respectively). Notably, in order to identify the effective peptides in camel milk, its protein sequences were retrieved and enzymatically digested in silico. Peptides that showed both anticancer and antibacterial properties and the highest stability in intestinal conditions were selected for the next step. Molecular interaction analysis was performed on specific receptors associated with breast cancer and/or antibacterial activity using molecular docking. The results showed that P3 (WNHIKRYF) and P5 (WSVGH) peptides had low binding energy and inhibition constant so that they specifically occupied active sites of protein targets. Our results introduced two peptide-drug candidates and new natural food additive that can be delivered to further animal and clinical trials.

β-Casein A1 and A2: Effects of polymorphism on the cheese-making process

Of late, "A2 milk" has gained prominence in the dairy sector due to its potential implications in human health. Consequently, the frequency of A2 homozygous animals has considerably increased in many countries. To elucidate the potential implications that beta casein (β-CN) A1 and A2 may have on cheese-making traits, it is fundamental to investigate the relationships between the genetic polymorphisms and cheese-making traits at the dairy plant level. Thus, the aim of the present study was to evaluate the relevance of the β-CN A1/A2 polymorphism on detailed protein profile and cheese-making process in bulk milk. Based on the β-CN genotype of individual cows, 5 milk pools diverging for presence of the 2 β-CN variants were obtained: (1) 100% A1; (2) 75% A1 and 25% A2; (3) 50% A1 and 50% A2; (4) 25% A1 and 75% A2; and (5) 100% A2. For each cheese-making day (n = 6), 25 L of milk (divided into 5 pools, 5 L each) were processed, for a total of 30 cheese-making processes. Cheese yield, curd nutrient recovery, whey composition, and cheese composition were assessed. For every cheese-making process, detailed milk protein fractions were determined through reversed-phase HPLC. Data were analyzed by fitting a mixed model, which included the fixed effects of the 5 different pools, the protein and fat content as a covariate, and the random effect of the cheese-making sessions. Results showed that the percentage of κ-CN significantly decreased up to 2% when the proportion of β-CN A2 in the pool was ≥25%. An increase in the relative content of β-CN A2 (≥50% of total milk processed) was also associated with a significantly lower cheese yield both 1 and 48 h after cheese production, whereas no effects were observed after 7 d of ripening. Concordantly, recovery of nutrients reflected a more efficient process when the inclusion of β-CN A2 was ≤75%. Finally, no differences in the final cheese composition obtained by the different β-CN pools were observed.

Analysis of genotyping features of bovine cattle individuals at the CSN2 locus using ACRS-PCR methods

In the context of solving the problem of obtaining high quality dairy products from livestock, the issue of determining the type of beta-casein (A1 and A2) in the protein fraction of milk becomes essential. Purpose – to analyse the use of ACRS-PCR methods for differentiation of A1 and A2 alleles of bovine beta-casein locus. Genotyping features were analysed using the artificially created restriction site polymerase chain reaction method utilising TaqI and DdeI restriction endonucleases. The electrophoretic distribution of DNA fragments in agarose gels of various concentrations was used to analyse restriction patterns. Based on the results of bioinformatic analysis of the nucleotide reference sequences of the experimental fragment of the beta-casein gene, it was found that the primer system for the ACRS-PCR DdeI method is characterised by higher parameters of flanking efficiency of the target DNA site compared to the ACRS-PCR TaqI system due to significantly greater effectiveness of hybridisation of oligonucleotides on the target DNA. Based on the results of laboratory tests of both methods, it is proposed to use an additional procedure for analysing the fluorescence intensity of individual elements of restriction patterns, which allows reducing the number of false genotyping that occurs in both cases (based on the results of using both methods) due to the appearance of non-specific amplification/restriction fragments within the size of target restrictions. The application of the ACRS-PCR DdeI method provides more differentiated patterns of the corresponding genotypes in agarose gel compared to the ACRS-PCR TaqI method, but leads to higher material costs for conducting research. These disadvantages of using primer systems for ACRS-PCR of the beta-casein locus determine the relevance of developing alternative methods for typing A1 and A2 alleles which include allele-specific PCR. The use of results is promising for solving the problems of genotyping cattle individuals of different breeds by A1 and A2 alleles of the beta-casein locus

Peculiarities of growth and further productivity of purebred and crossbred cows

Use of genetic specifics of pure breeding in animal husbandry allows cross breeders to produce herds that are completely of high breeding value, and also improve genetic potential of the best breeds. A relevant issue is determining the efficiency of crossbreeding of dairy breeds by analyzing the growth intensity of young bovine cattle, their reproductive ability and dairy productivity. We performed an analysis of experimental studies of using effective methods of selection, carried out a theoretical analysis, formulated hypotheses, used genealogical, biometrical and statistical methods, and assessed the productive properties of animals. We determined that the heifers from cross of the Ukrainian Red-Spotted cows with the sires of the Montbeliard breed – compared with the heifers from the Holstein bulls – had higher growth intensity and greater live weight during all the age periods. From birth until the age of one year, the Ukrainian Black-Spotted dairy heifers from the Holstein and Norwegian Red sires had no significant difference in weight. The heifers that resulted from cross of the Montbeliard and Ukrainian Red-Spotted dairy breeds had advantages over the purebred animals during all age periods, namely in the measurements of chest width, hook bone width, chest girth, ring metacarpal length. Body measurements of the replacement heifers, derived from the Norwegian Red and Holstein sires, varied within insignificant ranges depending on genotype, without significant difference. The animals were compact and proportionate; having received sufficient and complete diets, they had satisfactory weight categories. We determined that increase of the age of first insemination and first pregnancy was followed by decrease in the dairy productivity of cows. It ranged 0.021 to 0.064 in the bred heifers of different genotypes and breeds. There was observed an insignificant direct relationship between the abovementioned factors and the contents of fat and protein in milk. The shares of influence of age when the animals were first inseminated on milk yield accounted for 7.1% to 11.4%, 5.4–6.9 on fat content in milk, and 8.0–12.2% on protein fraction in milk. Crossbreeding can efficiently decrease the percentage of complicated deliveries and stillbirth rate, which in turn decreases the expenses for treatment of consequences of difficult calving, including the risk of decline in milk productivity and longer calving interval. However, there should be a careful approach to the selection of a breed, sire (preferably, its evaluation should be taken into account according to calving ease, especially when using the Montbeliard breed) and analysis of dams that are to be crossed with. Upgrading by mating to the Montbeliard and Norwegian breeds resulted in the crossbred cows that produced the greatest profit due to their heightened productivity. We should note that the estimated prices of extra products per cow give us grounds to state a positive effect from crossbreeding with the Montbeliard and Norwegian Red breeds. The performed studies confirm the benefits of identifying the efficiency of crossbreeding dairy breeds by an analysis of growth intensity of young bovine cattle.

Predicting milk protein fractions using infrared spectroscopy and a gradient boosting machine for breeding purposes in Holstein cattle

In recent years, increasing attention has been focused on the genetic evaluation of protein fractions in cow milk with the aim of improving milk quality and technological characteristics. In this context, advances in high-throughput phenotyping by Fourier transform infrared (FTIR) spectroscopy offer the opportunity for large-scale, efficient measurement of novel traits that can be exploited in breeding programs as indicator traits. We took milk samples from 2,558 Holstein cows belonging to 38 herds in northern Italy, operating under different production systems. Fourier transform infrared spectra were collected on the same day as milk sampling and stored for subsequent analysis. Two sets of data (i.e., phenotypes and FTIR spectra) collected in 2 different years (2013 and 2019-2020) were compiled. The following traits were assessed using HPLC: true protein, major casein fractions [αS1-casein (CN), αS2-CN, β-CN, κ-CN, and glycosylated-κ-CN], and major whey proteins (β-lactoglobulin and α-lactalbumin), all of which were measured both in grams per liter (g/L) and proportion of total nitrogen (% N). The FTIR predictions were calculated using the gradient boosting machine technique and tested by 3 different cross-validation (CRV) methods. We used the following CRV scenarios: (1) random 10-fold, which randomly split the whole into 10-folds of equal size (9-folds for training and 1-fold for validation); (2) herd/date-out CRV, which assigned 80% of herd/date as the training set with independence of 20% of herd/date assigned as the validation set; (3) forward/backward CRV, which split the data set in training and validation set according with the year of milk sampling (FTIR and gold standard data assessed in 2013 or 2019-2020) using the "old" and "new" databases for training and validation, and vice-versa with independence among them; (4) the CRV for genetic parameters (CRV-gen), where animals without pedigree as assigned as a fixed training population and animals with pedigree information was split in 5-folds, in which 1-fold was assigned to the fixed training population, and 4-folds were assigned to the validation set (independent from the training set). The results (i.e., measures and predictions) of CRV-gen were used to infer the genetic parameters for gold standard laboratory measurements (i.e., proteins assessed with HPLC) and FTIR-based predictions considering the CRV-gen scenario from a bi-trait animal model using single-step genomic BLUP. We found that the prediction accuracies of the gradient boosting machine equations differed according to the way in which the proteins were expressed, achieving higher accuracy when expressed in g/L than when expressed as % N in all CRV scenarios. Concerning the reproducibility of the equations over the different years, the results showed no relevant differences in predictive ability between using "old" data as the training set and "new" data as the validation set and vice-versa. Comparing the additive genetic variance estimates for milk protein fractions between the FTIR predicted and HPLC measures, we found reductions of -19.7% for milk protein fractions expressed in g/L, and -21.19% expressed as % N. Although we found reductions in the heritability estimates, they were small, with values ranging from -1.9 to -7.25% for g/L, and -1.6 to -7.9% for % N. The posterior distributions of the additive genetic correlations (ra) between the FTIR predictions and the laboratory measurements were generally high (>0.8), even when the milk protein fractions were expressed as % N. Our results show the potential of using FTIR predictions in breeding programs as indicator traits for the selection of animals to enhance milk protein fraction contents. We expect acceptable responses to selection due to the high genetic correlations between HPLC measurements and FTIR predictions.

Comparison of the Quality of Mountain Sheep Milk Obtained from Animals Kept on a Natural and Organic Mountain Pasture

Abstract The purpose of this study was to evaluate the quality of mountain sheep milk obtained from animals kept on mountain pastures: natural and organic. The experimental procedure was conducted under production conditions, during annual grazing of mountain sheep on two mountain pastures in the region of the Polish Carpathians: on organic pasture certified for organic farming and natural mountain pasture belonging to the National Park. This study showed greater plant species diversity in the organic mountain pasture, but its yielding was lower than that of the natural pasture. The sward of the natural pasture was characterised by lower dry matter and fibre content but contained more total protein. The type of pasture did not affect the basic composition of the milk of mountain sheep, while differences were found in terms of acidity, alcohol number, fatty acid profile of fat and milk protein fractions. Milk obtained from sheep grazed on organic pasture was characterised by a higher proportion of medium chain fatty acids, as well as polyunsaturated fatty acids, and also essential unsaturated fatty acids, both linoleic acid, α-linolenic acid, γ-linolenic acid and arachidonic acid. In milk originating from the natural mountain pasture, a higher proportion of monounsaturated fatty acids, docosahexaenoic acid and the CLA c9-t11 isomer was found. The composition of milk protein fractions varied according to the location of grazing: milk from sheep grazing on natural pasture had a higher content of whey fractions, important for consumer health, milk from organic pasture had a higher content of κ-casein, of greatest importance in dairy processing technology. The floral composition of the pasture had an influence on the quality of sheep milk in relation to the fatty acid profile of fat and protein fractions of milk, which is important in terms of both the health-promoting and technological aspects of the raw material and may affect the quality of products made from it.

Identification of CSN1S1 Gene Variations Between Dairy Goat Breeds and its Influence on Milk Protein Fractions in Indonesia

Identification of CSN1S1 Gene Variations Between Dairy Goat Breeds and its Influence on Milk Protein Fractions in Indonesia

Efeitos de um hepatoprotetor e diferentes fontes de energia na dieta sobre a composição do leite e a partição dos nutrientes em vacas lactantes

ABSTRACT The present study aimed at assessing the effects of hepatoprotective agents in diets that contain sources of energy on milk production, milk composition, and nutrient partition in lactating cows. Sixteen Holstein x Gir crossbred mid-lactation cows with an average body weight of 553 ± 85 kg were used in this study. These animals were allocated in a 4x4 Latin square design. A 2x2 factorial arrangement was employed in this feeding experiment. In each treatment, cows received diets with or without a hepatoprotective agent and variable in ground corn grain or citrus pulp as energy sources. Evaluated parameters included nutrient intake and digestibility, milk production, milk composition, energy balance, and nitrogen balance. Performance and nutrient balance variables were assessed and no interaction was observed between the hepatoprotective compounds and the dietary sources of energy. Dry matter intake, milk production and net energy for lactation were higher in corn as an energy source whereas milk fat content was higher in citrus pulp diets. There was a reduction in protein and casein contents in the milk of cows that was supplemented with an hepatoprotective agent. In this study, the hepatoprotective agent improved nitrogen balance in dairy cows. The use of the hepatoprotective compounds in the diet of these lactating cows in confinement reduced the milk protein fraction and favored a higher nitrogen balance in these animals. Retention of nitrogen compounds in the metabolism of lactating cows under confinement is influenced by hepatoprotective agents.