Milk metabolites as indicators of mammary gland functions and milk quality

Presence of pathogen DNA in milk harvested from quarters is associated to changes in cows' milk yield and composition

BACKGROUND

Intramammary infection is the result of invasion and multiplication of microorganisms in the mammary gland and commonly leads to mastitis in dairy animals. Although much has been done to improve cows' udder health, mastitis remains a significant and costly health issue for dairy farmers, especially if subclinical. In this study, quarter milk samples from clinically healthy cows were harvested to detect pathogens via quantitative PCR (qPCR) and evaluate changes in individual milk traits according to the number of quarters infected and the type of microorganism(s). A commercial qPCR kit was used for detection of Mycoplasma bovis, Mycoplasma spp., Staphylococcus aureus, coagulase-negative staphylococci (CNS), Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, Prototheca spp., Escherichia coli, Klebsiella spp., Enterococcus spp. and Lactococcus lactis ssp. lactis. Quarter and pooled milk information of 383 Holstein, 132 Simmental, 129 Rendena, and 112 Jersey cows in 9 Italian single-breed herds was available.

RESULTS

Among the cows with pathogen(s) present in at least 1 quarter, CNS was the most commonly detected DNA, followed by Streptococcus uberis, Mycoplasma bovis, and Streptococcus agalactiae. Cows negative to qPCR were 206 and had the lowest milk somatic cell count. Viceversa, cows with DNA isolated in ≥ 3 quarters were those with the highest somatic cell count. Moreover, when major pathogens were isolated in ≥ 3 quarters, milk had the lowest casein index and lactose content. In animals with pathogen(s) DNA isolated, the extent with whom milk yield and major solids were impaired did not significantly differ between major and minor pathogens.

CONCLUSIONS

The effect of the number of affected quarters on the pool milk quality traits was investigated in clinically healthy cows using a commercial kit. Results remark the important negative effect of subclinical udder inflammations on milk yield and quality, but more efforts should be made to investigate the presence of untargeted microorganisms, as they may be potentially dangerous for cows. For a smarter use of antimicrobials, analysis of milk via qPCR is advisable - especially in cows at dry off - to identify quarters at high risk of inflammation and thus apply a targeted/tailored treatment.

Intramammary administration of lipopolysaccharides at parturition enhances immunoglobulin concentration in goat colostrum

In newborn ruminants, transfer of passive immunity is essential to obtain protection against pathogens. This study aimed to increase the permeability of the blood-milk barrier using intramammary lipopolysaccharides (LPS) in goats at parturition to modulate colostrum composition. Twenty multiparous Majorera dairy goats were randomly allocated in one of the two experimental groups. The LPS group (n = 10) received an intramammary administration (IA) of saline (2 mL) containing 50 µg of LPS from Escherichia coli (O55:B5) in each half udder at parturition. The control group (n = 10) received an IA of saline (2 mL). Rectal temperature (RT) was recorded, and a blood sample was collected at parturition (before IA). In addition, RT was measured, and blood and colostrum/milk samples were collected on day (d) 0.125 (3 hours), 0.5 (12 hours), 1, 2, 4, 7, 15 and 30 relative to the IA. Goat plasma immunoglobulin G (IgG) and M (IgM) and serum β-hydroxybutyrate, glucose, calcium, free fatty acids, lactate dehydrogenase and total protein concentrations were determined. Colostrum and milk yields as well as chemical composition, somatic cell count (SCC), IgG and IgM concentrations were measured. The MIXED procedure (SAS 9.4) was used, and the model included the IA, time, and the interaction between both fixed effects. Statistical significance was set as P < 0.05. Goats from the LPS group showed higher RT on d 0.125, 0.5 and 4 relative to the IA compared to the control group (PIA×Time = 0.007). Goat serum biochemical variables and plasma IgG and IgM concentrations were not affected by the IA. Colostrum and milk yield as well as chemical composition were not affected by the IA, except for milk lactose percentage that was lower in the LPS group compared to the control group (4.3 ± 0.08 and 4.6 ± 0.08%, respectively PIA = 0.026). Colostrum SCC was higher in the LPS group than in the control group (3.5 ± 0.09 and 3.1 ± 0.09 cells × 106/mL, respectively; PIA = 0.011). Similarly, milk SCC increased in the LPS group compared to the control group (PIA = 0.004). The LPS group showed higher IgG (PIA = 0.044) and IgM (PIA = 0.037) concentrations on colostrum than the control group (31.9 ± 4.8 and 19.0 ± 4.8 mg/mL, 0.8 ± 0.08 and 0.5 ± 0.08 mg/mL, respectively). No differences in milk IgG and IgM concentrations between groups were observed. In conclusion, the IA of LPS at parturition increases RT, SCC and IgG and IgM concentrations in colostrum without affecting either yield or chemical composition.

Coordinated response of milk bacterial and metabolic profiles to subacute ruminal acidosis in lactating dairy cows

BACKGROUND

Bovine milk is an important source of nutrition for human consumption, and its quality is closely associated with the microbiota and metabolites in it. But there is limited knowledge about the milk microbiome and metabolome in cows with subacute ruminal acidosis.

METHODS

Eight ruminally cannulated Holstein cows in mid lactation were selected for a 3-week experiment. The cows were randomly allocated into 2 groups, fed either a conventional diet (CON; 40% concentrate; dry matter basis) or a high-concentrate diet (HC; 60% concentrate; dry matter basis).

RESULTS

The results showed that there was a decreased milk fat percentage in the HC group compared to the CON group. The amplicon sequencing results indicated that the alpha diversity indices were not affected by the HC feeding. At the phylum level, the milk bacteria were dominated by Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes both in the CON and HC groups. At the genus level, the HC cows displayed an improved proportion of Labrys (P = 0.015) compared with the CON cows. Results of both the principal components analysis and partial least squares of discriminant analysis of milk metabolome revealed that samples of the CON and HC groups clustered separately. A total of 31 differential metabolites were identified between the two groups. Of these, the levels of 11 metabolites decreased (α-linolenic acid, prostaglandin E2, L-lactic acid, L-malic acid, 3-hydroxysebacic acid, succinyladenosine, guanosine, pyridoxal, L-glutamic acid, hippuric acid, and trigonelline), whereas the levels of the other 20 metabolites increased in the HC group with respect to the CON group (P < 0.05).

CONCLUSION

These results suggested that subacute ruminal acidosis less impacted the diversity and composition of milk microbiota, but altered the milk metabolic profiles, which led to the decline of the milk quality.

Rheological Properties of Goat Milk Coagulation as Affected by Rennet Concentration, pH and Temperature

Various factors affect rennet coagulation and consequently cheese yield, but the subject of research has been mainly the cow milk. For the purpose of goat cheese production optimization, this paper investigated the influence of enzyme concentration (0.01–0.054 g/L), pH (6.5–6.1) and temperature (27–35 °C) on rennet coagulation of goat milk. Coagulation time (RCT), aggregation rate (AR), and gel firmness (G’60 and GF), were measured by oscillatory rheometry. The decrease in rennet concentration extended RCT. At lower rennet concentrations, a lower AR was recorded, which ranged from 0.02 Pa/s to 0.05 Pa/s. The decrease in pH from 6.5 to 6.1 caused a two times shorter RCT, and a two times faster AR. There was no effect of pH on the firmness of the rennet gel. The increase in coagulation temperature from 27 °C to 35 °C reduced the RCT of pasteurized milk from 12.6 min to 8.6 min, and caused a linear increase in the AR, but did not significantly affect the firmness of the gel. The present study revealed that the optimization of the rennet coagulation process could be directed towards pH lowering, or temperature increase, since they accelerate the process, but do not alter the examined gel firmness parameters.

Evaluation of key miRNAs during early pregnancy in Kazakh horse using RNA sequencing

Background

miRNA has an important role in cell differentiation, biological development, and physiology. Milk production is an important quantitative trait in livestock and miRNA plays a role in the amount of milk produced.

Methods

The role of regulatory miRNAs involved in equine milk production is not fully understood. We constructed two miRNA libraries for Kazakh horse milk production from higher-producing (H group) and lower-producing (L group) individuals, and used RNA-Seq technology to identify the differentially expressed miRNAs between the two milk phenotypes of Kazakh horses.

Results

A total of 341 known and 333 novel miRNAs were detected from the H and L groups, respectively. Eighty-three differentially expressed miRNAs were identified between the H and L group s, of which 32 were known miRNAs (27 were up-regulated, five were down-regulated) and 51 were novel miRNAs (nine were up-regulated, 42 were down-regulated). A total of 2,415 genes were identified. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses showed that these genes were annotated to mammary gland development, mammary gland morphogenesis, tissue development and PI3K-Akt signaling pathways, insulin signaling pathway and TGF-beta signaling pathway, among others. Five miRNAs (miR-199a-3p, miR143, miR145, miR221, miR486-5p) were identified as affecting horse milk production and these five miRNAs were validated using qRT-PCR.

Conclusions

We described a methodology for the transcriptome-wide profiling of miRNAs in milk, which may help the design of new intervention strategies to improve the milk yield of Kazakh horses.

Postpartum meloxicam administration alters plasma haptoglobin, polyunsaturated fatty acid, and oxylipid concentrations in postpartum ewes

Background

Postpartum inflammation is a natural and necessary response; however, a dysfunctional inflammatory response can be detrimental to animal productivity. The objective of this study was to determine the effects of a non-steroidal anti-inflammatory drug (meloxicam) on ewe postpartum inflammatory response, ewe plasma polyunsaturated fatty acid and oxylipid concentrations, and lamb growth.

Results

After lambing, 36 Hampshire and Hampshire × Suffolk ewes were sequentially assigned within type of birth to control (n = 17) or meloxicam orally administered on d 1 and 4 of lactation (MEL; 90 mg, n = 19). Milk and blood samples were collected on d 1 (prior to treatment) and d 4. Milk glucose-6-phosphate was not affected by MEL. Plasma haptoglobin (Hp) concentrations were less for MEL ewes; control ewes with greater d 1 Hp concentrations had elevated Hp on d 4, but this was not the case for MEL-treated ewes. Treatment with MEL increased plasma arachidonic acid concentration by more than 4-fold in ewes rearing singles but decreased concentrations of 9,10-dihydroxyoctadecenoic acid, prostaglandin F_2α, 8-iso-prostaglandin E₂, and 8,9-dihydroxyeicosatetraenoic acid. Nine oxylipids in plasma had interactions of treatment with d 1 Hp concentration, all of which revealed positive associations between d 1 Hp and d 4 oxylipid concentrations for CON, but neutral or negative relationships for MEL. MEL decreased 13-hydroxyoctadecadienoic acid:13-oxooctadecadienoic acid ratio and tended to increase 9-hydroxyoctadecadienoic acid:9-oxooctadecadienoic acid ratio (both dependent on d 1 values), indicating progressive metabolism of linoleic acid-derived oxylipids occurred by enzymatic oxidation after MEL treatment. Meloxicam reduced oxylipids generated across oxygenation pathways, potentially due to an improved redox state.

Conclusions

Postpartum MEL treatment of ewes decreased plasma concentrations of Hp and several oxylipids, with the greatest impact in ewes with biomarkers reflecting a greater inflammatory state before treatment. Anti-inflammatory strategies may help resolve excessive postpartum inflammation in some dams.

Physiological response of mammary glands to Escherichia coli infection:A conflict between glucose need for milk production and immune response

The mammary immune and physiological responses to distinct mammary-pathogenic E. coli (MPEC) strains were studied. One gland in each of ten cows were challenged intra-mammary and milk composition (lactose, fat, total protein, casein), biochemical (glucose, glucose-6-phosphate (Glu6P), oxalate, malate, lactate, pyruvate and citrate, malate and lactate dehydrogenases, lactate dehydrogenase (LDH), nitrite, lactic peroxidase, catalase, albumin, lactoferrin, immunoglobulin) and clotting parameters were followed for 35 days post-challenge. Challenge lead to clinical acute mastitis, with peak bacterial counts in milk at 16-24 h post-challenge. Biochemical and clotting parameters in milk reported were partially in accord with lipopolysaccharide-induced mastitis, but increased Glu6P and LDH activity and prolonged lactate dehydrogenase and Glu6P/Glu alterations were found. Some alterations measured in milk resolved within days after challenge, while others endured for above one month, regardless of bacterial clearance, and some reflected physiological responses to mastitis such as the balance between aerobic and anaerobic metabolism (citrate to lactate ratios). The results suggest that E. coli mastitis can be divided into two stages: an acute, clinical phase, as an immediate response to bacterial infection in the mammary gland, and a chronic phase, independent of bacteria clearance, in response to tissue damage caused during the acute phase.

Short communication: Diets supplemented with starch and corn oil, marine algae, or hydrogenated palm oil differently affect selected metabolite concentrations in cow and goat milk

The objective was to investigate the effects of species (cow vs. goat) and of various dietary lipid supplements, known to modulate milk fat content, on selected metabolites and enzymes in milk and to explore their correlations with performance traits. Twelve Holstein cows and 12 Alpine goats, all multiparous and nonpregnant, and at 86 ± 24.9 and 61 ± 1.8 DIM, respectively, were fed a basal diet (45% forage + 55% concentrate) not supplemented (CTL) or supplemented with corn oil plus wheat starch [COS, 5% of diet dry matter (DM)], marine algae powder (MAP, 1.5% of diet DM), or hydrogenated palm oil (HPO, 3% of diet DM) in a replicated 4 × 4 Latin square design with 28-d experimental periods. Intake, milk production and composition, milk fatty acid profile, and plasma metabolite concentrations were previously reported. Concentrations of 9 milk metabolites [β-hydroxybutyrate (BHB), glucose, glucose-6-phosphate, isocitrate, choline, glutamate, urea, cholesterol, and free amino groups] and 2 milk enzyme activities (alkaline phosphatase and lactate dehydrogenase) were measured on d 24 of each experimental period. Dairy performance data showed marked species and diet effects on milk fat content. Irrespective of diet, cow milk was richer in alkaline phosphatase and glucose compared with goat milk (16 and 3 times more, respectively), whereas goat milk had greater urea and glucose-6-phosphate concentrations compared with cow milk (1.9 and 5.3 times more, respectively). In cows, COS decreased milk BHB and choline (-25 and -43%, respectively) compared with CTL, whereas no effects were observed in goats. The COS and MAP diets increased milk isocitrate compared with CTL in cows, but COS decreased isocitrate concentrations in goat milk. Milk choline was correlated with milk fat content in cows (Spearman r, r_S = +0.73) and goats (r_s = +0.58), and lactate dehydrogenase activity was correlated with milk somatic cell count (r_s = +0.66) in cows but not in goats. We provide evidence of different milk metabolite responses according to species and diets. Metabolites and enzymes secreted in milk may be indicators of specificities of lipid metabolism among ruminant species and may contribute to a better understanding of mechanisms regulating milk fat secretion. Changes in the concentrations of some metabolites considered minor components of milk may be valuable diagnostic tools of mammary gland and animal metabolism as well as of milk processing characteristics.

chi-miR-143-3p Promotes Apoptosis of Mammary Gland Epithelial Cells from Dairy Goats by Targeting Ndfip1

The mammary gland is an important organ for lactation in dairy goats. Mammary gland development and lactation functions are primarily regulated by natural hormones and certain crucial regulatory factors. Nedd4 family-interacting protein 1 (Ndfip1) can specifically bind to neural precursor cell-expressed, developmentally downregulated protein 4 (Nedd4) family members to participate in ubiquitination, which in turn regulates a range of biological processes in the body. However, the effects of Ndfip1 expression regulation at the post-transcriptional level on the development of mammary gland cells have not been previously reported. To study the regulation of Ndfip1 at post-transcriptional level, the overexpression and interference vectors of Ndfip1 were constructed, and co-transfected into the primary mammary gland epithelial cells cultured in vitro with miR-143 mimics and inhibitor. Dual luciferase reporter gene system, real-time quantitative polymerase chain reaction, western blotting, cholecystokinin octapeptide assays, and flow cytometry were used to identify their regulation and function. As a result, Ndfip1 was targeted and regulated by miR-143, which influences the development of mammary gland epithelial cells in dairy goats cultured in vitro. This study will lay an experimental foundation for further understanding the functions of Ndfip1 and miR-143.

Dietary supplementation of Scutellaria baicalensis extract during early lactation decreases milk somatic cells and increases whole lactation milk yield in dairy cattle

Systemic inflammation is common in early lactation dairy cows and is associated with decreased milk production. The Scutellaria baicalensis plant contains flavonoids with anti-inflammatory and anti-oxidative properties, which may counteract the inflammatory state in early lactation dairy cows. The objective of this experiment was to determine whether Scutellaria baicalensis extract (SBE), a source of bioactive flavonoids, would alter the adaptation to lactation. Multiparous Holstein cows (n = 122) were used in a randomized block design to determine the effect of short-term and long-term postpartum administration of SBE on 305-d milk yield, 120-d milk component yield, and early lactation milk markers of inflammation and metabolic function. Treatments were 1) control, 2) short term (5-d) administration of the SBE (SBE5), and 3) long term (60-d) administration of the SBE (SBE60). Treatments were included in a treatment pellet that was identical to a control pellet in ingredient source and composition except for the extract (10 g/d SBE providing 3.3 g/d of the flavonoid baicalin), both provided via an automated milking system beginning on d 1 of lactation. Milk samples were collected on d 1, 3, and once during d 5–12 of lactation, followed by weekly sampling until 120 days in milk (DIM). Milk samples collected in the first 2 wk were used for biomarker analysis (haptoglobin, β-hydroxybutyrate [BHB], and glucose-6-phosphate [G6P]), and all samples were used for composition analysis. Cows were body condition scored every 2 wk prepartum and postpartum. Milk production, programmed pellet allocation, and actual provision of both pelleted feeds were recorded daily. Treatment effects were evaluated by contrasts between control and SBE5 and control and SBE60 for both the treatment (TP; wk 1–9) and carryover periods (CP; wk 10–37). Total pellet offered was greater for SBE60 in both the TP (P < 0.01) and CP (P = 0.02) but was not different for SBE5 during either period (P ≥ 0.13). No treatment effects were observed for body condition score (BCS), milk haptoglobin, BHB, or G6P. SBE5 did not alter milk yield or milk components. SBE60 increased whole-lactation milk yield by 1,419 kg (13%; P = 0.03). SBE60 increased milk lactose and fat yields (P ≤ 0.04) and tended to increase milk protein yield (P = 0.09) during TP, and each increased during CP (P ≤ 0.04). Somatic cell count decreased by 10% in SBE60 during TP (P = 0.02) but not CP (P = 0.13). Mastitis incidence tended to differ by treatment, being lesser for both SBE5 and SBE60 vs. control (14 and 15% vs. 33%). SBE supplementation did not impact time to pregnancy or hazard of leaving the herd. In conclusion, despite no detected treatment effects on BCS or milk biomarkers of inflammation and metabolic status, supplementation of postpartum dairy cows with Scutellaria baicalensis extract for 60 d was effective at increasing whole lactation milk yield.

D-lactate-selective amperometric biosensor based on the mitochondrial fraction of Ogataea polymorpha recombinant cells

During the recent decades, a lot of data about the significance of D-lactate determination in food technology and quality control have been accumulated. Nowadays, the development of new methods for the determination of D-lactate is very relevant, especially with regard to biosensors. To construct a D-lactate-selective biosensor, we suggest using the mitochondria of recombinant yeast cells of Ogataea (Hansenula) polymorpha "tr6" (gcr1 catX/Δcyb2, prAOX_DLDH) overproducing D-lactate: cytochrome c-oxidoreductase (DLDH, EC 1.1.2.4) and lacking an L-lactate-specific enzyme (flavocytochrome b₂ , E.C. 1.1.2.3). The usage of the pure enzyme is problematic due to the complexity of its isolation and stabilization because of the intramembranous localization of DLDH. The enzyme catalyzes D-lactate oxidation to pyruvate coupled with ferricytochrome c reduction to ferrocytochrome c. The constructed biosensor is characterized by high sensitivity (18.5 А·М^-1 ·m^-2 ), a low detection limit (3 μM of D-lactate), wide linear ranges, good selectivity, and sufficient stability. The real samples' analysis of D-lactate in dairy products was performed, and high correlation of the obtained results with the reference approach (0.7 < r < 1) and literature data was demonstrated.

Milk Metabolomics Data Reveal the Energy Balance of Individual Dairy Cows in Early Lactation

In early lactation, dairy cows typically have a negative energy balance which has been related to metabolic disorders, compromised health and fertility, and reduced productive lifespan. Assessment of the energy balance, however, is not easy on the farm. Our aims were to investigate the milk metabolic profiles of dairy cows in early lactation, and to obtain models to estimate energy balance from milk metabolomics data and milk production traits. Milk samples were collected in week 2 and 7 after calving from 31 dairy cows. For each cow, the energy balance was calculated from energy intake, milk production traits and body weight. A total of 52 milk metabolites were detected using LC-QQQ-MS. Data from different lactation weeks was analysed by partial least squares analysis, the top 15 most relevant variables from the metabolomics data related to energy balance were used to develop reduced linear models to estimate energy balance by forward selection regression. Milk fat yield, glycine, choline and carnitine were important variables to estimate energy balance (adjusted R²: 0.53 to 0.87, depending on the model). The relationship of these milk metabolites with energy balance is proposed to be related to their roles in cell renewal.

Considerações sobre o tratamento das mastites

RESUMO: A mastite é considerada o maior problema dos animais destinados à produção de leite. Altera a sua composição e aumenta a contagem de células somáticas (CCS). Os micro-organismos envolvidos na doença podem ser origem infecciosa, como Staphylococcus aureus, ou ambiental, tal como Escherichia coli. A cultura bacteriana é uma ferramenta de diagnóstico e auxilia na detecção do patógeno causador da mastite. No entanto, fatores como fagocitose podem desencadear um resultado negativo. Quando estabelecido um programa de controle de mastite, o diagnóstico precoce e o início do tratamento adequado dos casos clínicos são fundamentais para se atingir os objetivos e seu sucesso, está relacionado com o patógeno envolvido. A indicação do tratamento de longa duração, ou terapia estendida, tem melhorado a resposta ao tratamento em casos de mastite por S. aureus, no entanto, com 30-50% de cura. Do ponto de vista do manejo dos animais, devido a alta contagiosidade deste patógeno, sua persistência no rebanho e custo em função ao tratamento, muitas vezes, o descarte do animal tem sido priorizado a fim de controlar os casos de mastite em propriedades. As medidas de controle são muito importantes para contribuir com a redução de casos de mastite por este patógeno. A indicação do tratamento intramamário associada com sistêmico tem poder efetivo em casos de mastite por E. coli, cujos casos agudos apresentam-se com sepse e toxemia. São abordados ainda aspectos de tratamentos alternativos das mastites, utilizados principalmente no processo orgânico de produção leiteira.

Effects of photoperiod modulation and melatonin feeding around drying-off on bovine mammary gland involution

The risk for a dairy cow to acquire new intramammary infections is high during the transition from lactation to the dry period, because of udder engorgement and altered immune functions. Once the gland is fully involuted, it becomes much more resistant to intramammary infections. Therefore, strategies to depress milk yield before drying-off and accelerate the involution process after drying-off could be beneficial for udder health. The objective of this study was to assess the effect of photoperiod manipulation and melatonin feeding from 14 d before to 14 d after drying-off on the speed of the involution process. Thirty Holstein cows in late lactation were randomly allocated to one of the following treatments: (1) a long-day photoperiod (16 h of light: 8 h of darkness), (2) a short-day photoperiod (8 h of light: 16 h of darkness), and (3) a long-day photoperiod supplemented by melatonin feeding (4 mg/kg of body weight). Milk and blood samples were collected on d -26, -19, -12, -5, -1, 1, 3, 5, 7, 10, and 14 relative to the last milking to determine concentrations of mammary gland involution markers and serum prolactin. Additional blood samples were taken around milking on d -15, before the start of the treatments, and on d -1, before drying-off, to evaluate the treatment effects on milking-induced prolactin release. The short-day photoperiod slightly decreased milk production and basal prolactin secretion during the dry period. The milking-induced prolactin surge was smaller on d -1 than on d -15 regardless of the treatments. Lactoferrin concentration, somatic cell count, and BSA concentration as well as matrix metalloproteinase-2 and -9 activities increased in mammary secretions during the first 2 wk of the dry period, whereas milk citrate concentration and the citrate:lactoferrin molar ratio decreased. The rates of change of these parameters were not significantly affected by the treatments. The long-day photoperiod supplemented by melatonin feeding did not affect milk production, prolactin secretion, or mammary gland involution. Under the conditions in this study, photoperiod modulation and melatonin feeding did not appear to affect the rate of mammary gland involution.

Evaluation of an On-Farm Culture System (Accumast) for Fast Identification of Milk Pathogens Associated with Clinical Mastitis in Dairy Cows

The present study aimed evaluate an on-farm culture system for identification of milk pathogens associated with clinical mastitis in dairy cows using two different gold standard approaches: standard laboratory culture in study 1 and 16S rRNA sequencing in study 2. In study 1, milk from mastitic quarters (i.e. presence of flakes, clots, or serous milk; n = 538) was cultured on-farm using a single plate containing three selective chromogenic media (Accumast—FERA Animal Health LCC, Ithaca, NY) and in a reference laboratory using standard culture methods, which was considered the gold standard. In study 2, mastitic milk was cultured on-farm and analyzed through 16S rRNA sequencing (n = 214). In both studies, plates were cultured aerobically at 37°C for 24 h and read by a single technician masked to gold standard results. Accuracy, sensitivity, specificity, positive (PPV) and negative predictive value (NPV) were calculated based on standard laboratory culture in study 1, and PPV was calculated based on sequencing results in study 2. Overall accuracy of Accumast was 84.9%. Likewise, accuracy for identification of Gram-negative bacteria, Staphylococcus sp., and Streptococcus sp. was 96.4%, 93.8%, and 91.5%, respectively. Sensitivity, specificity, PPV, and NPV were 75.0%, 97.9%, 79.6%, and 97.3% for identification of E. coli, 100.0%, 99.8%, 87.5%, and 100.0% for S. aureus, 70.0%, 95.0%, 45.7%, and 98.1% for other Staphylococcus sp., and 90.0%, 92.9%, 91.8%, and 91.2% for Streptococcus sp. In study 2, Accumast PPV was 96.7% for E. coli, 100.0% for Enterococcus sp., 100.0% for Other Gram-negatives, 88.2% for Staphylococcus sp., and 95.0% for Streptococcus sp., respectively. In conclusion, Accumast is a unique approach for on-farm identification pathogens associated with mastitis, presenting overall sensitivity and specificity of 82.3% and 89.9% respectively.

Milk glucose-6-phosphate dehydrogenase activity and glucose-6-phosphate are associated with oxidative stress and serve as indicators of energy balance in dairy cows

Schematic model to explain the changes in milk G6P/glucose ratio in early lactation.

Reduced use of glucose by normoxic cow's mammary gland under acute inflammation: an example of homeostatic aerobic glycolysis

The concentration of glucose and glucose-derived carbons in milk reflect their concentrations in the mammary epithelial cell cytosol.

Influence of intramammary infection of a single gland in dairy cows on the cow's milk quality

Intramammary infection (IMI), comprises a group of costly diseases affecting dairy animals worldwide. Many dairy parlours are equipped with on-line computerised data acquisition systems designed to detect IMI. However, the data collected is related to the cow level, therefore the contribution of infected glands to the recorded parameters may be over estimated. The present study aimed at evaluating the influence of single gland IMI by different bacteria species on the cow's overall milk quality. A total of 130 cows were tested 239 times; 79 cows were tested once and the others were examined 2-8 times. All of the analysed data refer to the number of tests performed, taking into account the repeated testing of the same cows. Of the cows tested ~50% were free of infection in all 4 glands and the others were infected in one gland with different coagulase negative staphylococci (CNS), Streptococcus dysgalactiae, or were post infected with Escherichia coli (PIEc), i.e., free of bacterial infection at the time of sampling but 1-2 months after clinical infection by E. coli. Overall, infection with bacteria had significant effects on somatic cell count (SCC) and lactose concentration. Examining each bacterium reveals that the major influence on those parameters was the sharp decrease in lactose in the PIEc and curd firmness in PIEc and Strep. Individual gland milk production decreased ~20% in Strep. dysgalactiae- and ~50% in PIEc-infected glands with respect to glands with no bacterial findings. Significant differences were found in lactose, SCC, rennet clotting time and curd firmness in the milk of infected glands and among those, these parameters were significantly higher in Strep. dysgalactiae and PIEc than in CNS infected cows. The current results using quarter-milking reinforces the importance of accurate IMI detection in relation to economic and welfare factors, and moreover, emphasises the need for technical sensing and constant reporting to the farmer about changes in the milk quality of every animal.

The intracellular source, composition and regulatory functions of nanosized vesicles from bovine milk-serum

A hypothesis that the source of milk-serum derived vesicles (MSDVs) is the Golgi apparatus (GA) was examined.