The soluble phase of milk was separated at 20 and 80°C using ultrafiltration. The resulting permeates were then subjected to further ultrafiltration and dialysis at close to these two temperatures. It was found that pH, Ca2+ and soluble Ca decreased as the separation temperature increased both in original UF permeates and in dialysates obtained from these permeates, but P decreased only slightly. The major reason for these changes was due to the precipitation of calcium phosphate/citrate complexes onto the casein micelle with concomitant release of H+. The pH of both permeates and dialysates from milk at 20°C were slightly higher than for milk. When UF permeates collected at 20 and 80°C, were each dialysed at both these temperatures, the dialysate collected at 80°C showed much less temperature dependence for pH and ionic calcium compared with that collected at 20°C. This is in contrast to milk, which shows considerable temperature dependence for pH and ionic calcium. Further experiments revealed that the pH and Ca2+ concentration of permeates showed high temperature dependence above the temperature at which they were separated, but a much lower temperature dependence below that temperature. These findings suggest that dialysis and UF of milk at high temperature provide the best means yet for estimating the pH and ionic calcium of milk at that temperature.

Activity of the enzyme β-glucuronidase (EC 3.2.1.31) is found in milk from ruminants with mastitis. However, the use of this enzymic activity as an indicator of mastitis has gained little attention possibly because of its low activity when compared with other mastitis indicators. The determination may therefore be less precise and the analytical procedure very time consuming and labour intensive. The present study optimized the fluorometric determination of the β-glucuronidase activity with respect to substrate concentration, pH, incubation time etc., validated the assay, and developed it into large scale analyses. The assay performance is satisfactory regarding precision, linearity etc., and it appears comparable to analogous fluorometric assays for mastitis indicators in milk. From a local dairy herd, 825 milk samples were analysed for potential mastitis indicators, i.e. β-glucuronidase, lactate dehydrogenase (LDH), alkaline phosphatase (AP), and N-acetyl-β-d-glucosaminidase (NAGase) activity, and for somatic cell counts (SCC) and the variables were compared. Activity of β-glucuronidase was moderately but significantly correlated to SCC (r=0·21; n=768) as well as the other mentioned variables (r=0·25–0·43; n=825). Simple indices based on β-glucuronidase and LDH or NAGase activity were tested as indicators of mastitis (SCC), but were not found to improve the diagnostic value. Future studies may further verify whether β-glucuronidase can compete with well-established indicators of mastitis in cows such as LDH or NAGase as well as determine whether β-glucuronidase activity, in combination with other indicators of mastitis, has an advantage. Nineteen milk samples from subclinical and latent cases of mastitis (individual quarters) were identified for specific pathogens (PCR method) and measured for β-glucuronidase activity. The activity was tested at four different pH levels (5·5, 6·0, 6·5 and 7·0) in order to investigate the possibility of discrimination between pathogens. However, all milk samples (strains of pathogens) had the same pH optimum for β-glucuronidase activity; this may indicate that enzymic activity from mammary tissue and leucocytes dominates over enzyme activity from bacterial cells.

This study evaluated the effects of intraruminal administration of Megasphaera elsdenii on ruminal fermentation patterns, the profile of plasma metabolites, and milk yield and composition of mid-lactation dairy cows. Eight primiparous, ruminally cannulated Holstein cows were arranged in a paired 2×2 crossover design. Cows were randomly assigned to one of two treatments: 1) intraruminal inoculation of 35 ml suspension per day of M. elsdenii ATCC 25940 (MEGA), containing 108 cfu/ml of bacteria, dissolved in 35 ml of saline (0·15 m), or 2) carrier alone (35 ml saline; CTR). Both postprandial and preprandial rumen volatile fatty acids (VFA) and plasma metabolite measurements were analysed. Postprandial VFA patterns were affected the most, with butyrate (P<0·01) and valerate (P<0·01) proportions increasing, and acetate (P<0·01), isobutyrate (P=0·05) and isovalerate (P<0·01) decreasing in MEGA cows. Preprandial data measured at various days showed that MEGA dosage tended to increase the molar proportion of propionate (P=0·09) and lower the acetate to propionate ratio (P=0·07) in the rumen fluid. There was no effect of treatment on rumen pH and on the concentration of lactate in the rumen as well as on selected preprandial plasma metabolites. Postprandial plasma concentrations of cholesterol tended to increase (P=0·07) in MEGA cows compared with CTR. Concentrations of non-esterified fatty acids (NEFA) in the plasma were lower in MEGA cows after the morning feeding (P<0·01). Sampling hour also affected plasma NEFA in this study. Plasma β-hydroxybutyrate (BHBA) were not affected by the treatment (P>0·05); however, after the morning feeding BHBA concentration was increased in both groups of cows. Dry matter intake and milk yield and composition were not affected by treatment. In conclusion, results indicate that M. elsdenii has the potential to modulate the rumen fermentation profile in mid-lactation Holstein cows, but these effects were only slightly reflected in changes in plasma metabolites and milk composition.

Kefir is a dairy product popular in many countries in Central Europe, especially in Poland and other countries of Eastern and Northern Europe. This type of fermented milk is produced by a complex population of symbiotic bacteria and yeasts. In this work, conditions for DNA extraction, involving disruption of kefir grains and a cascade of cell lysis treatments, were established. Extraction procedure of total microbial DNA was carried out directly from fresh kefir grains. Using different lysis stringency conditions, five DNA pools were obtained. Genetic diversity of DNA pools were validated by RAPD analysis, which showed differences in patterns of amplified DNA fragments, indicating diverse microbial composition of all the analysed samples. These DNA pools were used for construction of genomic DNA libraries for sequencing. As much as 50% of the analysed nucleotide sequences showed homology to sequences from bacteria belonging to the Lactobacillus genus. Several sequences were similar to sequences from bacteria representing Lactococcus, Oenococcus, Pediococcus, Streptococcus and Leuconostoc species. Among homologues of yeast proteins were those from Candida albicans, Candida glabrata, Kluyveromyces lactis and Saccharomyces cerevisiae. In addition, several sequences were found to be homologous to sequences from bacteriophages.

Dietary estrogens may play a role in the etiology of hormone-dependent cancers like breast cancer. Cow's milk contains various endogenous estrogens and feed derived phytoestrogens that potentially contribute to an estrogenic effect of milk in consumers, and therefore we evaluated the effect of milk (whey) in a proliferation assay with estrogen-sensitive MCF-7 human breast cancer cells. Milk samples were obtained from 22 cows representing different stages of pregnancy (first and second half) and whey was produced from the milk. 0·1, 0·25 or 0·5% whey was included in the cell culture medium and after 6 days of treatment cell proliferation was assessed by a colorimetric method with a fluorometer. Whey induced significant (P<0·05) proliferative effects compared with control cells with no added whey at all concentrations tested. There was no difference in the proliferative effect of whey depending on the stage of pregnancy from which the milk was obtained. We did not observe anti-proliferative effects when whey was tested in the presence of 10 pm estradiol in the medium. In conclusion, these results indicate that whey, irrespective of the pregnancy stage from which the milk was obtained induced a significant proliferative response in MCF-7 cells and no anti-proliferative effect, which may be caused, at least in part, by estrogens present in milk. The implications of our findings in relation to for example breast cancer will have to be studied further in other model systems preferentially in vivo.

The objective of this study was to characterize the fatty acids (FA) in milk based on genetic and herd parameters to investigate the origin of the different FA in milk. Milk samples of 1912 Dutch Holstein-Friesian cows were analysed for 39 different FA including odd and branched-chain fatty acids. The proportion of variation caused by genetic and herd effects was calculated. In addition, genetic and herd correlations among the fatty acids were estimated and a clustering technique was used to visualise these correlations. The results indicated that in Dutch milk C12:0 is not completely synthesised de novo but also partly blood derived. It was suggested that C20:0 in milk is formed from the action of elongase enzymes on C18:0 and that the odd-chain FA C5:0–C13:0 and a part of C15:0 and C17:0 are synthesised de novo while the other part of C15:0 and C17:0 is blood derived. Furthermore, this work gives an overview of the opportunities to change the concentration of individual FA both by breeding and feeding. It is clearly shown that the extent to which the individual FA can be changed varies greatly and is dependent on the origin of the different FA in milk.

Concomitant with intensive selection for increased milk yield, reproductive performance of dairy cows has declined in the last decades, in part due to an unfavourable genetic relationship between these traits. Given that the six main milk protein genes (i.e. whey proteins and caseins) are directly involved in milk production and hence have been a target of the strong selection aimed at improving milk yield in dairy cattle, we hypothesized that these genes could show selection footprints associated with fertility traits. In this study, we used an in-vitro fertilization (IVF) system to test genetic association between 66 single nucleotide polymorphisms (SNPs) in the four caseins (αS1-casein, αS2-casein, β-casein and κ-casein) and the two whey protein genes (α-lactalbumin and β-lactoglobulin) with fertilization rate and early embryonic development in the Holstein breed. A total of 6893 in-vitro fertilizations were performed and a total of 4661 IVF embryos were produced using oocytes from 399 ovaries and semen samples from 12 bulls. Associations between SNPs and fertility traits were analysed using a mixed linear model with genotype as fixed effect and ovary and bull as random effects. A multiple testing correction approach was used to account for the correlation between SNPs due to linkage disequilibrium. After correction, polymorphisms in the LALBA and LGB genes showed significant associations with fertilization success and blastocyst rate. No significant associations were detected between SNPs located in the casein region and IVF fertility traits. Although the molecular mechanisms underlying the association between whey protein genes and fertility have not yet been characterized, this study provides the first evidence of association between these genes and fertility traits. Furthermore, these results could shed light on the antagonistic relationship that exists between milk yield and fertility in dairy cattle.

Genomic selection is a new technology in which selection decisions are based on direct genomic values (DGVs) or genomic enhanced breeding values (GEBVs). The objective of this study was to evaluate the relations between DGVs and several milk traits important for both the nutritional value and processability of milk. This is a new approach and can be used to increase the knowledge on how genomic selection can be used in practice. Morning milk samples from Swedish Holstein cows were analyzed for milk composition and technological properties. DGVs were received for each cow for milk, protein and fat yield, milk index, udder health, Nordic total merit and a quota was calculated between fat and milk yield as well as protein and milk yield. The results show that linear correlations exist (P<0·10) between the studied DGVs and contents and yields of parameters in the protein (P=0·002–0·097), fat (P=0·024–0·055) and mineral profiles (P=0·001–0·099) as well as for cheese characteristics (P=0·004–0·065), thus making it possible to obtain detailed information on milk traits that are not registered in the milk recording scheme. Hence, genomic selection will be an efficient tool for breeding and dairy industry to select cows early in life for targeted milk production.

The objective of this study was to apply factor analysis to describe lactation curves in dairy buffaloes in order to estimate the phenotypic and genetic association between common latent factors and cumulative milk yield. A total of 31 257 monthly test-day milk yield records from buffaloes belonging to herds located in the state of São Paulo were used to estimate two common latent factors, which were then analysed in a multi-trait animal model for estimating genetic parameters. Estimates of (co)variance components for the two common latent factors and cumulated 270-d milk yield were obtained by Bayesian inference using a multiple trait animal model. Contemporary group, number of milkings per day (two levels) and age of buffalo cow at calving (linear and quadratic) as covariate were included in the model as fixed effects. The additive genetic, permanent environmental and residual effects were included as random effects. The first common latent factor (F1) was associated with persistency of lactation and the second common latent factor (F2) with the level of production in early lactation. Heritability estimates for F1 and F2 were 0·12 and 0·07, respectively. Genetic correlation estimates between F1 and F2 with cumulative milk yield were positive and moderate (0·63 and 0·52). Multivariate statistics employing factor analysis allowed the extraction of two variables (latent factors) that described the shape of the lactation curve. It is expected that the response to selection to increase lactation persistency is higher than the response obtained from selecting animals to increase lactation peak. Selection for higher total milk yield would result in a favourable correlated response to increase the level of production in early lactation and the lactation persistency.

Genes in the sterol regulatory element-binding protein-1 (SREBP1) pathway play a central role in regulation of milk fat synthesis, especially the de-novo synthesis of saturated fatty acids. SCD, a SREBP-responsive gene, is the key enzyme in the synthesis of monounsaturated fatty acids in the mammary gland. In the present study, we discovered SNP in candidate genes associated with this signalling pathway and SCD to identify genetic markers that can be used for genetic and metabolically directed selection in cattle. We resequenced six candidate genes in the SREBP1 pathway (SREBP1, SCAP, INSIG1, INSIG2, MBTPS1, MBTPS2) and two genes for SCD (SCD1 and SCD5) and discovered 47 Tag SNP that were used in a marker-trait association study. Milk and blood samples were collected from Holstein cows in their 1st or 2nd parity at 100–150 days of lactation. Individual fatty acids from C4 to C20, saturated fatty acid (SFA) content, monounsaturated fatty acid content, polyunsaturated fatty acid content and desaturase indexes were measured and used to perform the asociation analysis. Polymorphisms in the SCD5 and INSIG2 genes were the most representative markers associated with SFA/unsaturated fatty acid (UFA) ratio in milk. The analysis of desaturation activity determined that markers in the SCD1 and SCD5 genes showed the most significant effects. DGAT1 K232A marker was included in the study to examine the effect of this marker on the variation of milk fatty acids in our Holstein population. The percentage of variance explained by DGAT1 in the analysis was only 6% of SFA/UFA ratio. Milk fat depression was observed in one of the dairy herds and in this particular dairy one SNP in the SREBP1 gene (rs41912290) accounted for 40% of the phenotypic variance. Our results provide detailed SNP information for key genes in the SREBP1 signalling pathway and SCD that can be used to change milk fat composition by marker-assisted breeding to meet consumer demands regarding human health, as well as furthering understanding of technological aspects of cows' milk.

The effects of high pressure (HP) treatment (100–400 MPa at 10–60°C) on the solubility of milk protein concentrate (MPC) powders were tested. The solubility, measured at 20°C, of fresh MPC powders made with no HP treatment was 66%. It decreased by 10% when stored for 6 weeks at ambient temperature (∼20°C) and continued to decrease to less than 50% of its initial solubility after 12 months of storage. Of the combinations of pressure and heat used, a pressure of 200 MPa at 40°C applied to the concentrate before spray drying was found to be the most beneficial for improved solubility of MPC powders. This combination of pressure/heat improved the initial cold water solubility to 85%. The solubility was maintained at this level after 6 weeks storage at ambient temperature and 85% of the initial solubility was preserved after 12 months. The improved solubility of MPC powders on manufacture and on storage are attributed to an altered surface composition arising from an increased concentration of non-micellar casein in the milk due to HP treatment prior to drying. The improved solubility of high protein powders (95% protein) made from blends of sodium caseinate and whey protein isolate compared with MPC powders (∼85% protein) made from ultrafiltered/diafiltered milk confirmed the detrimental role of micellar casein on solubility. The results suggest that increasing the non-micellar casein content by HP treatment of milk or use of blends of sodium caseinate and whey proteins are strategies that may be used to obtain high protein milk powders with enhanced solubility.

Bovine mastitis is the most important infectious disease on dairy farms. Conventional antibiotic therapy is often unsatisfactory and alternative treatments are continually under investigation. Lactobacillus (Lb.) perolens CRL 1724 and Lactobacillus plantarum CRL 1716 were previously isolated from milk of dairy cows and selected according to their potential probiotic properties. In the present work the in-vitro capacity of Lactobacillus strains to adhere to bovine teat canal epithelial cells (BTCEC) and to inhibit and co-aggregate 14 mastitis-causing pathogens (MCPs) was investigated. The effect of Lb. perolens CRL 1724 after intramammary inoculation in lactating cows was evaluated through determination of clinical signs of mastitis, milk appearance, somatic cell counts and Lb. perolens CRL 1724 recovery from milk. Lb. perolens CRL 1724 was able to inhibit 12 of 14 MCPs (85·7%) in vitro, especially those considered to be major pathogens. In addition, Lb. perolens CRL 1724 co-aggregated with all of them. Lb. plantarum CRL 1716 was able to inhibit 7 of 14 MCPs (50%) in vitro and showed co-aggregation ability similar to Lb. perolens CRL 1724. Lb. perolens CRL 1724 showed a higher efficacy of adhesion to BTCEC (values of percentage of adhesion and adhesion index of 75% and 14·4, respectively) than Lb. plantarum CRL 1716 (37% and 7·4, respectively). Lb. perolens CRL 1724 was recovered from all mammary quarters and no clinical signs or teat damage were observed after the inoculation of 106 cfu/ml. The udders presented a normal aspect and there were no changes in the appearance of the milk. The results obtained will serve as the basis for further trials to evaluate the potential of Lb. perolens CRL 1724 to be included in a non-antibiotic formulation for the prevention of bovine mastitis.

In this study, the physicochemical properties of a low-fat dried yogurt paste (kashk) were determined, and the effects of different concentrations (0, 0·1, 0·3 and 0·5% w/w) of gum tragacanth exudates from Astragalus gossypinus on the stability and texture of the samples were investigated by measuring amount of syneresis, turbidity, particle size distribution (PSD), flow behaviour and viscoelastic properties. The flow behaviour index was not very sensitive to the concentration of gum, while a remarkable concentration dependency of the power-law consistency coefficient and Herschel–Bulkley yield stress was observed. The initial increase in the gum concentration at 0·1 and 0·3% levels led to a higher degree of syneresis, which was related to the depletion flocculation mechanism. However, the reduced amount of syneresis in samples containing 0·5% gum tragacanth was attributed to the significant increase in viscosity of the continuous phase, which is also accompanied by trapping of the aggregated casein particles. The presence of 3% salt in the samples may have led to the neutralization of charges on the surface of gum tragacanth; consequently, the non-adsorbing behaviour of high-ionic-strength polysaccharides inhibited the formation of electrostatic protein–polysaccharide complexes. Furthermore, maximum values of polydispersity, syneresis and tan δ at high frequencies were found in samples containing 0·1% gum tragacanth.

The distribution of the volatile components in four regions, Rind, Exterior, Intermediate, and Interior, of hand-made Idiazabal cheese which had been ripened for two months was studied in detail. It is proved that the headspace of this ripened sheep cheese is non-homogeneous in the different cheese regions. The Rind is the richest region in volatile compounds, followed by the Exterior region. A large number of compounds with different functional groups have their greatest abundances in the Rind with negative abundance gradients towards the interior regions. Many of these are undetectable in the Intermediate and Interior regions. Other compounds such as aldehydes having a great number of carbon atoms, and most of the acids have their greatest abundances in the Exterior region. Alcohols, ketones and esters of small size have their greatest abundances in the Intermediate region. And finally, a reduced number of compounds are distributed homogeneously in all cheese regions. The origin of the compounds, the conditions that favour their formation, their functional groups, size, shape and reactivity could be factors involved in their distribution in the cheese, which in turn is associated with the microbial ecology, chemical reactions and physical effects.

The relations between cow genetics and milk composition have gained a lot of attention during the past years, however, generally only a few compositional traits have been examined. The aim of this study was to determine if polymorphisms in the leptin (LEP), leptin receptor (LEPR) and acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1) genes as well as genetic polymorphism of β-casein (β-CN), κ-CN and β-lactoglobulin (β-LG) impact several bovine milk composition traits. Individual milk samples from the Swedish Red and Swedish Holstein breeds were analyzed for components in the protein, lipid, carbohydrate and mineral profiles. Cow alleles were determined on the following SNP: A1457G, A252T, A59V and C963T on the LEP gene, T945M on the LEPR gene and Nt984+8(A-G) on the DGAT1 gene. Additionally, genetic variants of β-CN, κ-CN and β-LG were determined. For both the breeds, the same tendency of minor allele frequency was found for all SNPs and protein genes, except on LEPA1457G and LEPC963T. This study indicated significant (P<0·05) associations between the studied SNPs and several compositional parameters. Protein content was influenced by LEPA1457G (G>A) and LEPC963T (T>C), whereas total Ca, ionic Ca concentration and milk pH were affected by LEPA1457G, LEPA59V, LEPC963T and LEPRT945M. However, yields of milk, protein, CN, lactose, total Ca and P were mainly affected by β-CN (A2>A1) and κ-CN (A>B>E). β-LG was mainly associated with whey protein yield and ionic Ca concentration (A>B). Thus, this study shows possibilities of using these polymorphisms as markers within genetic selection programs to improve and adjust several compositional parameters.

Twelve Lactobacillus isolates from Brazilian starter-free ovine cheeses were evaluated for their probiotic potential. The strains were identified by 16S rDNA sequencing as Lactobacillus plantarum (7), Lb. brevis (2), Lb. casei (2) and Lb. parabuchneri (1). All strains showed variable resistance to gastric juices and relative tolerance to pancreatin and bile salts. Only five strains of Lb. plantarum could not deconjugate the sodium salt of taurodeoxycholic acid. Autoaggregation ability after 24 h was above 50% and hydrophobicity was higher than 60% for most strains. All lactobacilli could inhibit linolenic acid oxidation, except Lb. parabuchneri strain, whereas none of them could scavenge DPPH radical. β-Galactosidase activity ranged from 47·7 to 2503 Miller units. Inhibition of food pathogens Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, Escherichia coli and Salmonella typhimurium was demonstrated and the production of organic acids could be associated with this effect. The Lactobacillus strains from Brazilian regional ovine cheese showed interesting functional characteristics, mainly the strains Lb. brevis SM-B and Lb. plantarum SM-I. Both presented high acid tolerance. In addition, Lb. brevis SM-B also displayed remarkable antioxidant activity and Lb. plantarum SM-I was the highest β-galactosidase producer, exhibited high autoaggregation and hydrophobicity properties.