Dairy Species Research Articles

Composition and aptitude for cheese-making of milk from cows, buffaloes, goats, sheep, dromedary camels, and donkeys

Bovines produce about 83% of the milk and dairy products consumed by humans worldwide, the rest represented by bubaline, caprine, ovine, camelid, and equine species, which are particularly important in areas of extensive pastoralism. Although milk is increasingly used for cheese production, the cheese-making efficiency of milk from the different species is not well known. This study compares the cheese-making ability of milk sampled from lactating females of the 6 dairy species in terms of milk composition, coagulation properties (using lactodynamography), curd-firming modeling, nutrients recovered in the curd, and cheese yield (through laboratory model-cheese production). Equine (donkey) milk had the lowest fat and protein content and did not coagulate after rennet addition. Buffalo and ewe milk yielded more fresh cheese (25.5 and 22.9%, respectively) than cow, goat, and dromedary milk (15.4, 11.9, and 13.8%, respectively). This was due to the greater fat and protein contents of the former species with respect to the latter, but also to the greater recovery of fat in the curd of bubaline (88.2%) than in the curd of camelid milk (55.0%) and consequent differences in the recoveries of milk total solids and energy in the curd; protein recovery, however, was much more similar across species (from 74.7% in dromedaries to 83.7% in bovine milk). Compared with bovine milk, the milk from the other Artiodactyla species coagulated more rapidly, reached curd firmness more quickly (especially ovine milk), had a more pronounced syneresis (especially caprine milk), had a greater potential asymptotical curd firmness (except dromedary and goat milk), and reached earlier maximum curd firmness (especially caprine and ovine milk). The maximum measured curd firmness was greater for bubaline and ovine milk, intermediate for bovine and caprine milk, and lower for camelid milk. The milk of all ruminant species can be used to make cheese, but, to improve efficiency, cheese-making procedures need to be optimized to take into account the large differences in their coagulation, curd-firming, and syneresis properties.

Distribution and variation in proteins of casein micellar fractions response to heat-treatment from five dairy species

Casein micelles (CMs) contribute to the physicochemical properties and stability of milk. However, how the proteome of CMs changes following heat treatment has not been elucidated. Here, changes in the proteins of CMs in samples of Holstein, buffalo, yak, goat, and camel milk following heat treatment were investigated using a LC-MS/MS approach. According to the hierarchical clustering results, Holstein, yak, and buffalo milk samples had similar CMs protein components, followed by goat and camel milk samples. Changes in lipoprotein lipase and α-lactalbumin in CMs were dependent on the intensity of heat treatment and were similar among the studied species, whereas changes in κ-casein, lactoferrin, and apolipoprotein A-I differed among different types of milk. These results provide information on the distribution and variations of the proteomes of CMs following heat treatment, which will assist in the identification of proteins that are dissociated and attached to CMs from different dairy species during heat treatment.

Expression profile of different classes of proteases in milk derived somatic cells across different lactation stages of indigenous cows (Bos indicus) and riverine buffaloes (Bubalus bubalis)

Proteases play a significant role in milk and its products by affecting flavor, texture and longevity. The expression of endogenous proteases varies across different stages of lactation. The study was conducted to understand the transcriptional pattern of different classes of protease-pathways associated genes (CTSB, CTSD, CTSH, CTSL, CTSK, CTSS, CTSZ, PLAU, PLAT) and potential protease inhibitors (SERPIN E2 and SERPIN F2) in 40 milk somatic cells (MSC) samples isolated during early, peak, mid and late lactation stages of Sahiwal cows and Murrah buffaloes – the two most important dairy breeds of India. In Sahiwal cows, except CTSK and PLAU, the expression of other proteases class was not affected significantly (p > 0.05) across lactation stages. However, in Murrah buffaloes, the expression of different proteases increased as the lactation progressed. Most of the proteases showed lower expression during early and peak lactation stages while their expression tends to increase during mid to late lactation stages. The overall trend was somewhat similar in both the dairy species albeit the level of expression was higher in buffalo MSC as compared to cow MSC. The study has provided valuable information on expression kinetics of different proteases in milk somatic cells of two major dairy breeds of India.

Milk infrared spectra from multiple instruments improve performance of prediction models

Milk data predicted from infrared spectra are the basis of selection programmes for dairy species, but several factors influence the robustness of prediction models, e.g., (i) variability of collected samples, (ii) number and quality of reference data, and (iii) influence traits on milk spectral fingerprint. Use of single or multiple instruments spectra from the same set of samples to develop mid infrared calibration models was investigated. Fitting statistics for milk coagulation properties were low to fair. Better results were achieved for titratable acidity and cheese yield; coefficients of determination in cross validation ranged from 0.52 to 0.77, depending on the trait analysed and training set. Merging spectral data from two instruments did not improve calibration performance but provided the best fitting statistics in external validation for most of the traits on different validation sets. Merging spectral data from different instruments is a cost-effective method to improve calibration performance and robustness.

Recent Advances in Camel Milk Processing.

Simple SummaryThe camel milk market was limited for a long time by its almost exclusive self-consumption use in nomadic camps. Significant development has been observed for the past two or three decades, including internationally, boosted by its reputation regarding its health effects for regular consumers. Such emergence has led the stakeholders in the sector to offer diversified products corresponding to the tastes of increasingly urbanized consumers, more sensitive to “modern” products. Thus, traditionally drunk in raw or naturally fermented form, camel milk has undergone unprecedented transformations such as pasteurization, directed fermentation, cheese or yoghurt processing, and manufacture of milk powder for the export market. However, the specific characteristics of this milk (composition, physical properties) mean that the technologies applied (copied from technologies used for cow milk) must be adapted. In this review, some technological innovations are presented, enabling stakeholders of the camel milk sector to satisfy the demand of manufacturers and consumers.Camel milk is a newcomer to domestic markets and especially to the international milk market. This recent emergence has been accompanied by a diversification of processed products, based on the technologies developed for milk from other dairy species. However, technical innovations had to be adapted to a product with specific behavior and composition. The transformation of camel milk into pasteurized milk, fermented milk, cheese, powder, or other products was supported, under the pressure of commercial development, by technological innovations made possible by a basic and applied research set. Some of these innovations regarding one of the less studied milk sources are presented here, as well as their limitations. Technical investigations for an optimal pasteurization, development of controlled fermentation at industrial scale, control of cheese technology suitable for standardized production, and improvements in processes for the supply of a high-quality milk powder are among the challenges of research regarding camel milk.

Nutritional Regulation of Mammary Gland Development and Milk Synthesis in Animal Models and Dairy Species.

In mammals, milk is essential for the growth, development, and health. Milk quantity and quality are dependent on mammary development, strongly influenced by nutrition. This review provides an overview of the data on nutritional regulations of mammary development and gene expression involved in milk component synthesis. Mammary development is described related to rodents, rabbits, and pigs, common models in mammary biology. Molecular mechanisms of the nutritional regulation of milk synthesis are reported in ruminants regarding the importance of ruminant milk in human health. The effects of dietary quantitative and qualitative alterations are described considering the dietary composition and in regard to the periods of nutritional susceptibly. During lactation, the effects of lipid supplementation and feed restriction or deprivation are discussed regarding gene expression involved in milk biosynthesis, in ruminants. Moreover, nutrigenomic studies underline the role of the mammary structure and the potential influence of microRNAs. Knowledge from three lactating and three dairy livestock species contribute to understanding the variety of phenotypes reported in this review and highlight (1) the importance of critical physiological stages, such as puberty gestation and early lactation and (2) the relative importance of the various nutrients besides the total energetic value and their interaction.

Advances in Dairy Research

The Journal of Advances in Dairy Research is an international Journal of high-standing that publishes original scientific research on all aspects of the biology, wellbeing and technology of lactating animals and the foods they produce. The Journal’s ability to cover the entire dairy foods chain is a major strength. Cross-disciplinary research is particularly welcomed, as is comparative lactation research in different dairy and non-dairy species and research dealing with consumer health aspects of dairy products. Journal of Dairy Research: an international Journal of the lactation sciences.

Technical note: Repeatability and reproducibility of curd yield and composition in a miniaturized coagulation model

Miniaturized coagulation (MC) models have been proposed for the evaluation of curd yield (CY) in individual milk samples of different dairy species and breeds, and for the analysis of cheese microstructure and texture. It is still unclear if MC using less than 50 mL of milk is suitable to evaluate CY and chemical composition, and if preservative added to raw milk may interfere with MC process. Therefore, this study aimed at evaluating repeatability and reproducibility of CY, curd moisture, and fat and protein content on curd dry matter (DM) from MC trials using 40 g of milk. Miniaturized coagulations were performed by 3 different operators on 3 consecutive days, using raw milk (RM) and raw milk added with preservative (RMP). Repeatability of CY, calculated as relative standard deviation on 6 miniaturized curds obtained within a day by the same operator, was below 5% for MC carried out with both RM and RMP. The Horwitz ratio, which is the ratio between measured and expected reproducibility, highlighted good reproducibility for CY from RM and fair reproducibility for CY from RMP. The same ratio highlighted lower accuracies for curd moisture and fat and protein content on curd DM, especially for MC trials carried out with RMP. The z-test was performed to evaluate the similarity between curds manufactured with RM and RMP in terms of average yield and chemical composition; z-scores did not highlight significant differences between values obtained from MC carried out with RM and RMP. It can be concluded that preservative had negligible effects on MC, giving the opportunity to extend milk physical and chemical stability, to schedule laboratory trials on longer time span, and to broaden the sample size within a batch of analyses.

Survivability of Salmonella and Escherichia coli O157:H7 Pathogens and Food Safety Concerns on Commercial Powder Milk Products

Milk and dairy products are susceptible to the incidence of foodborne illnesses by numerous pathogens, including Listeria monocytogenes, Salmonella spp., Escherichia coli, enteropathogenic Campylobacter jejuni, Yersinia enterocolitica, Cronobacter (Enterobacter sakazakii) and Staphylococcus aureus. Annually Salmonella infections cause approximately 93.8 million cases of gastroenteritis and 155,000 deaths worldwide. Including meat and poultry, dairy products are the most commonly contaminated foods by Salmonella. Studies show that Salmonella, Escherichia coli O157:H7 and Listeria monocytogenes are among the top 5 pathogens causing hospitalization and life-threatening foodborne illnesses. The U.S. Centers for Disease Control and Prevention (CDC) estimated that annually around 1.2 million foodborne illnesses with more than 23,000 hospitalizations, 450 deaths and 130 outbreaks were attributed to Salmonella infection in the U.S. The Salmonella enteric in skim milk powder survived at three months storage, with water activity as low as 0.33. With respect to Escherichia coli O157:H7, it is capable of causing disease at a low dosage, ranging from 5–50 cells. Viable cells of Escherichia coli O157:H7 reportedly survive in infant formula powder for one year at 5 °C. The survivability of Escherichia coli in powder milk was significantly reduced with the synergistic effects of storage time and temperature. The U.S. Dairy Export Council recommends that milk powder should be stored in a cool and dry place, at a temperature not to exceed 27 °C, and a relative humidity not to exceed 65%. Reports have recommended that milk powder products need to be stored in light, oxygen, and moisture-proof containers. In this article, the survival of the major foodborne pathogens including Salmonella and Escherichia coli O157:H7 in powdered milk products from common dairy species such as cow and goats are reviewed.

Feed intake–dependent and –independent effects of heat stress on lactation and mammary gland development

With a growing population, a reliable food supply is increasingly important. Heat stress reduces livestock meat and milk production. Genetic selection of high-producing animals increases endogenous heat production, while climate change increases exogenous heat exposure. Both sources of heat exacerbate the risk of heat-induced depression of production. Rodents are valuable models to understand mechanisms conserved across species. Heat exposure suppresses feed intake across homeothermic species including rodents and production animal species. We assessed the response to early-mid lactation or late-gestation heat exposure on milk production and mammary gland development/function, respectively. Using pair-fed controls we experimentally isolated the feed intake-dependent and -independent effects of heat stress on mammary function and mass. Heat exposure (35°C, relative humidity 50%) decreased daily feed intake. When heat exposure occurred during lactation, hypophagia accounted for approximately 50% of the heat stress-induced hypogalactia. Heat exposure during middle to late gestation suppressed feed intake, which was fully responsible for the lowered mammary gland weight of dams at parturition. However, the impaired mammary gland function in heat-exposed dams measured by metabolic rate and lactogenesis could not be explained by depressed feed consumption. In conclusion, mice recapitulate the depressed milk production and mammary gland development observed in dairy species while providing insight regarding the role of feed intake. This opens the potential to apply genetic, experimental, and pharmacological models unique to mice to identify the mechanism by which heat is limiting animal production.

Composition, Structure, and Digestive Dynamics of Milk From Different Species-A Review.

Background: The traditional dairy-cattle-based industry is becoming increasingly diversified with milk and milk products from non-cattle dairy species. The interest in non-cattle milks has increased because there have been several anecdotal reports about the nutritional benefits of these milks and reports both of individuals tolerating and digesting some non-cattle milks better than cattle milk and of certain characteristics that non-cattle milks are thought to share in common with human milk. Thus, non-cattle milks are considered to have potential applications in infant, children, and elderly nutrition for the development of specialized products with better nutritional profiles. However, there is very little scientific information and understanding about the digestion behavior of non-cattle milks.Scope and Approach: The general properties of some non-cattle milks, in comparison with human and cattle milks, particularly focusing on their protein profile, fat composition, hypoallergenic potential, and digestibility, are reviewed. The coagulation behaviors of different milks in the stomach and their impact on the rates of protein and fat digestion are reviewed in detail.Key findings and Conclusions: Milk from different species vary in composition, structure, and physicochemical properties. This may be a key factor in their different digestion behaviors. The curds formed in the stomach during the gastric digestion of some non-cattle milks are considered to be relatively softer than those formed from cattle milk, which is thought to contribute to the degree to which non-cattle milks can be easily digested or tolerated. The rates of protein and fat delivery to the small intestine are likely to be a function of the macro- and micro-structure of the curd formed in the stomach, which in turn is affected by factors such as casein composition, fat globule and casein micelle size distribution, and protein-to-fat ratio. However, as no information on the coagulation behavior of non-cattle milks in the human stomach is available, in-depth scientific studies are needed in order to understand the impact of compositional and structural differences on the digestive dynamics of milk from different species.

Understanding seasonal weight loss tolerance in dairy goats: a transcriptomics approach

BackgroundSeasonal weight loss (SWL) is a very important limitation to the production of ruminants in the Mediterranean and Tropical regions. In these areas, long dry seasons lead to poor pastures with low nutritional value. During the dry season, ruminants, particularly those raised in extensive production systems, lose around 30% of their body weight. Seasonal weight loss has important consequences on animal productive performance and health. In this study, RNA sequencing was used to characterize feed restriction effects in dairy goat of 2 breeds with different SWL tolerance: Majorera (tolerant) and Palmera (susceptible). Nine Majorera and ten Palmera goats were randomly distributed in a control and a restricted group: Majorera Control (adequately fed; MC; n = 4), Palmera Control (adequately fed; PC; n = 6), Majorera Restricted (feed restricted; ME; n = 5) and Palmera Restricted (feed restricted; PE; n = 4). On day 22 of the trial, mammary gland biopsies were collected for transcriptomics analysis.ResultsFrom these samples, 24,260 unique transcripts were identified. From those, 82 transcripts were differentially expressed between MC and ME, 99 between PC and PE, twelve between both control groups and twenty-nine between both restricted groups.ConclusionsFeed restriction affected several biochemical pathways in both breeds such as: carbohydrate and lipid transport; intracellular trafficking, RNA processing and signal transduction. This research also highlights the importance or involvement of the genes in tolerance (ENPP1, S-LZ, MT2A and GPNB) and susceptibility (GPD1, CTPS1, ELOVL6 and NR4A1) to SWL with respectively higher expression in the Majorera restriced group and the Palmera restricted group in comparison to the control groups. In addition, results from the study may be extrapolated to other dairy ruminant species.

The Milk Microbiota of the Spanish Churra Sheep Breed: New Insights into the Complexity of the Milk Microbiome of Dairy Species.

Simple SummaryIn the last decade, the number of studies focused on the study of the microbiota of different tissues, organs, or physiological fluids has considerably increased. The milk of dairy species is an important and continuous source of commensal, mutualistic and potentially probiotic bacteria. Second-generation sequencing technologies have been applied to characterise the milk microbiota of dairy cows, whereas the study of the sheep milk microbiota is scarce. In the present study, we aimed to explore the bacterial diversity and composition of milk samples from the Churra sheep breed, a rustic autochthonous breed from the region of Castilla y León (Spain). Moreover, this study tries to clarify the complex bacterial composition of sheep milk comparing the results presented here with previous research on the milk microbiota of the Assaf sheep breed. This assessment has shown that the milk microbiota of ewes from one flock of the Assaf breed is more diverse than the milk microbiota reported here for two different flocks of Churra sheep. The study also provides a step into a better understanding of the link between the bacterial milk composition in these two sheep breeds and somatic cell count, an indicator trait of subclinical mastitis resistance in dairy sheep.Milk from healthy animals has classically been considered a sterile fluid. With the development of massively parallel sequencing and its application to the study of the microbiome of different body fluids, milk microbiota has been documented in several animal species. In this study, the main objective of this work was to access bacterial profiles of healthy milk samples using the next-generation sequencing of amplicons from the 16S rRNA gene to characterise the milk microbiome of the Churra breed. A total of 212 samples were collected from two Churra dairy farms with a different management system. The core milk microbiota in Churra ewes includes lesser genera (only two taxa: Staphylococcus and Escherichia/Shigella) than studies reported in other dairy species or even in a previous study in Assaf sheep milk. We found that diversity values in the two flocks of Churra breed were lower than the diversity of the milk microbiota in Assaf. The non-metric multidimensional scaling (NMDS) ordination using Bray-Curtis distance separates samples based on their microbiota composition. The information reported here might be used to understand the complex issue of milk microbiota composition.

Exosome cargo in milk as a potential marker of cow health.

Recent advances on milk exosomes (EXO), cargoes in cell-cell communication, explored their role within and between individuals, including in dairy species. The potential use of EXO as biomarkers of disease and metabolic conditions adds significant interest to the study of EXO in milk. Although several researches have been carried out on circulating miRNA in the milk, less information is available about milk-derived exosomal miRNAs, which are stable over time and resistant to digestion and milk processing. EXO are taken up by recipient cells through specific mechanisms, which enable the selective delivery of cargoes. This suggests that EXO cargoes can be used as biomarkers of health. Nevertheless, methodological limitations and potential applications of milk EXO in dairy ruminants must be considered. The paucity of studies that associate the EXO cargo to specific challenges deserves further investigations to unravel the variation of miRNA and proteins cargo in relation to metabolic imbalance and infectious disease of the mammary gland.

Milk Products from Minor Dairy Species: A Review.

Simple SummaryDairy products represent an important food source for worldwide people. The milk used for their manufacturing is mostly supplied from the four major ruminant species (cow, goat, sheep, and buffalo), on which the research has been focused for long time. In recent years, the social transformation underway in poor and developing countries, climatic changes, and increased attention to animal welfare are shining a light on some minor animal species that have a “local dairy importance” such as equines, camels, and yaks. Even though not specifically reared for milk production, they are sometimes regularly milked for the manufacturing of a series of dairy products such as fermented milk, cheese, butter, and other fat- and non-fat-based specialties. The investigations on their manufacturing processes, and on their chemical-nutritional and microbiological properties, are now rapidly increasing, and a robust set of scientific data is beginning to form. These information will help to improve the quality of these products and to spread the knowledge about them all over the world. In the near future, they could represent a source of innovative and functional foods for a wider number of people, supplying an income to farmers and enhancing food biodiversity. Milk processing is one of the most ancient food technologies, dating back around 6000 BC. The majority of dairy products are manufactured from cows, buffaloes, goats, and sheep; their production technologies are mostly standardized and have been widely investigated. Milk and dairy products from minor species are less important under the economic point of view, but they play a fundamental social role in many marginal and poor areas. Due to scarce interest of the dairy industry, their technological characteristics and related issues have been investigated less. Recently, the increasing interest toward ethnic foods and food biodiversity is helping these minor products to emerge from the “darkness” in which they have remained for long time. Some of them are increasingly seen as useful for the valorization of marginal areas, while others are recognized as innovative or healthy foods. The present review aims to resume the most recent knowledge about these less-known dairy products. The first part summarizes the main technological properties of equine, camel, and yak milk with a view to processing. The second is a survey on the related dairy products, both the traditional ones that have been manufactured for a long time and those that have been newly developed by food researchers.

Rapid animal species identification of feta and mozzarella cheese using MALDI-TOF mass-spectrometry

The correct labelling of foodstuffs with regard to the value-determining ingredients is decisive for the consumer. Therefore, one of the main topics of official food control for meat, seafood and milk products is the inspection of the declared animal species. The use of unlabeled cow's milk products to substitute highly-priced sheep's or buffalo's milk cheese has concerned consumer protection laboratories for many years. Recently, matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) has been demonstrated to identify the animal species of milk used for production of cheese and some other dairy products. The identification was conducted by comparison of mass spectra resulting from samples with those in a corresponding reference database. In this study, a MALDI-TOF MS database for animal species identification of dairy products was created using Bruker's MALDI Biotyper-system in combination with a simple extraction method without a tryptic digestion step. The database contains more than 150 reference spectra of milk and cheese from different dairy species. Using feta/white cheese as well as mozzarella, two of the most consumed cheeses from goat, sheep, cow's or buffalo's milk, we demonstrated MALDI-TOF MS to be an easy, fast and specific tool to identify the animal species of the milk these cheeses were made from. This method has been validated and established in the routine analysis of official food control. Exchange of reference spectra generated and used in this study is facilitated by the MALDI-user platform (https://maldi-up.ua-bw.bwl.de).

Lipid metabolic differences in cows producing small or large milk fat globules: Fatty acid origin and degree of saturation

This study compared cows that consistently produce milk with small (volume-weighted mean diameter of 2.92-3.83 µm, with an average diameter of 3.29 µm) or large (volume-weighted mean diameter of 4.58-5.67 µm, with an average diameter of 4.92 µm) milk fat globule (MFG) size distributions in terms of the fatty acid (FA) composition of the MFG core. Selected cows fell into the respective size group over at least 3 independent measurements, including an observation period before the experiment. Further selection criteria were similar milk production traits between cows (milk yield, fat yield, fat/protein ratio) and established lactation (>50 d in milk). However, the selected groups differed in parity (parity 1-3 and 3-5 in the small and large MFG groups, respectively), and the small MFG group was an average of 25 d in milk later in their lactation period. All cows were under the same nutritional management and environmental conditions. Here, we show that cows with the small or large MFG phenotype differed in their lipid metabolism in terms of the FA composition of the MFG core. Our results indicate that cows with the small MFG phenotype produced milk with higher concentrations of unsaturated FA despite being fed the same diet. We suggest that this characteristic of the small MFG phenotype is the result of increased uptake of long-chain FA from the blood circulation. A relationship between the degree of unsaturation and MFG size was also identified in preliminary studies across other species-namely, camels, sheep, and goats. These findings show the potential for on-farm selection of cows (and potentially other dairy species) based on MFG size to produce milk with improved nutrient composition. This could lead to purpose-specific separation of milk based on MFG size and FA profile, both known to alter the technological properties of milk.

Effects of indirect indicators of udder health on nutrient recovery and cheese yield traits in goat milk

In dairy goats, very little is known about the effect of the 2 most important indirect indicators of udder health [somatic cell count (SCC) and total bacterial count (TBC)] on milk composition and cheese yield, and no information is available regarding the effects of lactose levels, pH, and NaCl content on the recovery of nutrients in the curd, cheese yield traits, and daily cheese yields. Because large differences exist among dairy species, conclusions from the most studied species (i.e., bovine) cannot be drawn for all types of dairy-producing animals. The aims of this study were to quantify, using milk samples from 560 dairy goats, the contemporary effects of a pool of udder health indirect indicators (lactose level, pH, SCC, TBC, and NaCl content) on the recovery of nutrients in the curd (%REC), cheese yield (%CY), and daily cheese yields (dCY). Cheese-making traits were analyzed using a mixed model, with parity, days in milk (DIM), lactose level, pH, SCC, TBC, and NaCl content as fixed effects, and farm, breed, glass tube, and animal as random effects. Results indicated that high levels of milk lactose were associated with reduced total solids recovery in the curd and lower cheese yields, because of the lower milk fat and protein contents in samples rich in lactose. Higher pH correlated with higher recovery of nutrients in the curd and higher cheese yield traits. These results may be explained by the positive correlation between pH and milk fat, protein, and casein in goat milk. High SCC were associated with higher recovery of solids and energy in the curd but lower recovery of protein. The higher cheese yield obtained from milk with high SCC was due to both increased recovery of lactose in the curd and water retention. Bacterial count proved to be the least important factor affecting cheese-making traits, but it decreased daily cheese yields, suggesting that, even if below the legal limits, TBC should be considered in order to monitor flock management and avoid economic losses. The effect of NaCl content on milk composition was linked with lower recovery of all nutrients in the curd during cheese-making. In addition, high milk NaCl content led to reductions in fresh cheese yield and cheese solids. The indirect indicators of the present study significantly affected the cheese-making process. Such information should be considered, to adjust the milk-to-cheese economic value and the milk payment system.

Association between the GHR, GHRHR and IGF1 gene polymorphisms and milk coagulation properties in Sarda sheep.

We investigated whether variation of the sheep Growth Hormone Receptor (GHR), Growth Hormone Releasing Hormone Receptor (GHRHR) and Insulin-Like Growth Factor 1 (IGF1) genes were associated with milk coagulation properties (MCP) in sheep. The GHR, GHRHR and IGF1 genes are part of the GH system, which is known to modulate metabolism, growth and reproduction as well as mammogenesis and galactopoiesis in dairy species. A total of 380 dairy Sarda sheep were genotyped for 36 SNPs mapping to these three genes. Traditional MCP were measured as rennet coagulation time (RCT), curd-firming time (k20) and curd firmness at 30 m (a30). Modeling of curd firming over time (CFt) was based on a 60 m lactodynamographic test, generating a total of 240 records of curd firmness (mm) for each milk sample. The model parameters obtained included: the rennet coagulation time as a result of modeling all data available (RCTeq, min); the asymptotic potential value of curd firmness (CFP, mm) at an infinite time; the CF instant rate constant (kCF, %/min); the syneresis instant rate constant (kSR, %/min); the maximum value of CF (CFmax, mm) and the time at achievement of CFmax (tmax, min). Statistical analysis revealed that variation of the GHR gene was significantly associated with RCT, kSR and CFP (P < 0.05). No other significant associations were detected. These findings may be useful for the dairy industry, as well as for selection programs.

Characterization of a Novel Porcine CSN2 Polymorphism and Its Distribution in Five European Breeds.

Simple SummaryPolymorphisms in genes encoding major milk proteins have been intensely studied, and are used, worldwide, in marker-assisted selection in dairy species: αS1-casein in goats—associated with milk protein content and flavor; κ-casein and β-lactoglobulin in cattle—associated with milk quantity and quality; bovine β-casein—associated with human health, etc. This aspect has scarcely been investigated in pigs. Using an electrophoretic technique, we previously identified a novel porcine β-casein (encoded by CSN2) polymorphism. Here, we fully characterize it at protein and DNA level, propose a genotyping protocol, and investigate its distribution in five European porcine breeds. In brief, a G/A point mutation in position 647 of the porcine CSN2 cDNA leads to an arginine/glutamine substitution in position 201 of the protein. This mutation can be typed via a StyI PCR-RFLP assay. The frequency of the G allele was 0.965 in the investigated Landrace population (number of individuals genotyped n = 67), one in the Pietrain (n = 40), 0.705 in the Large White (n = 36), 0.885 in the Bazna (n = 13), and 0.555 in the Mangalita population (n = 11). Considering that milk protein content still varies widely within (and between) porcine breeds, this and/or other similar polymorphisms may have implications for the dynamics of piglet growth during suckling.Here, we describe a novel porcine β-casein (CNS2) polymorphism, initially identified using the isoelectric focusing (IEF) technique, and provide its distribution in five European breeds. Porcine CSN2 cDNA samples, from sows identified using IEF as carriers of polymorphic variants, were sequenced, and based on the sequence alignments, a genotyping assay was developed. The distribution of the polymorphism was investigated by genotyping 167 sows. Population genetic indexes were computed using POPGENE32 version 1.32. Sequence alignments revealed that the mutation which caused the different β-casein IEF migration profiles was c.647G>A, a substitution located in exon 7, which modifies the amino acid from position 201 of the mature protein from arginine to glutamine. The frequency of the G allele was 0.965 in the investigated Landrace population (number of individuals genotyped n = 67), one in the Pietrain population (n = 40), 0.705 in the Large White population (n = 36), 0.885 in the Bazna population (n = 13), and 0.555 in the Mangalita population (n = 11). For all breeds, except Pietrain (monomorphic), the genotype distribution was in accordance with the Hardy–Weinberg equilibrium. Given that β-casein is the most important protein in sows’ milk, a polymorphism like the one described here may prove interesting for marker-assisted selection.