Somatic Cell Count Research Articles

Age at first calving and productive performance of primiparous Holsteins.

This study investigated the age at first calving in Holstein heifers and its impact on various production parameters. A sample of 737 Holstein heifers born between 2015 and 2018 and finishing their first lactations between 2018 and 2020 was included. Cluster analysis revealed three groups based on age at first calving: high precocity, medium precocity and low precocity. Medium-precocity group exhibited the highest 305-day milk yield and peak milk production. Additionally, the same group demonstrated superior mean production per lactation, 305-day milk protein content, and 305-day milk yield. The lowest somatic cell count was found in the low-precocity group. In conclusion, medium-precocity cows showed better results such as higher 305-day milk yield and peak milk production.

Evaluation of the Role of Veterinarians for Outcomes Related to the Health and Production of Dairy Small Ruminants in Greece

The objective of the present study was to evaluate the potential benefits of veterinarians in improving the health and welfare of dairy sheep and goats by studying the associations of management practices employed in the farms with production- or health-related outcomes in sheep and goat farms in Greece. This work explored associations with ‘professional relationship with a veterinarian’ at 444 small ruminant dairy farms in an investigation performed around Greece, where 106 variables, related to infrastructure, animals, production outcomes, health management, health problems and human resources, were assessed. In 384 (86.5%) farms, a professional relationship with a veterinarian was maintained. The median value of visits made annually by veterinarians to these farms was five. In farms with a professional relationship with a veterinarian, significant differences were found in 24 variables (35.8%) related to management practices and 6 (30.0%) production- or health-related outcomes. In multivariable analysis, the following emerged with a significant association: epg counts in faecal samples (p = 0.014), average annual milk production per ewe/doe (p = 0.015), somatic cell counts in bulk-tank milk (p = 0.037), and annual incidence of clinical mastitis (p = 0.044). Moreover, associations of the characteristics of veterinarians emerged with somatic cell counts in bulk-tank milk: the gender (p < 0.0001) and the age (p = 0.004) of the veterinarians. The results attest that the application of veterinary advice and clinical services in sheep and goat dairy farms contributes to the improved health, production and welfare of animals.

Assessing the relationship between somatic cell count and the milk mid-infrared spectrum in Chinese Holstein cows.

Milk produced by dairy cows is a complex combination of many components, but the effect of mastitis has only been investigated for a few of these components. Milk mid-infrared (MIR) spectra can reflect the global composition of milk, and this study aimed to detect the relationships between milk MIR spectral wavenumbers and milk somatic cell count (SCC)-a sensitive biomarker for mastitis. Pearson correlation analysis was used to calculate the correlation coefficient between somatic count score (SCS) and spectral wavenumbers. A general linear mixed model was applied to investigate the effect of three different classes of SCC (low, middle and high) on spectral wavenumbers. The mean correlation coefficient betweenthe 'fingerprint region' (wavenumbers 925-1582 cm-1 ) and the SCS was higher than that for other regions of the MIR spectrum, and the specific wavenumber with the strongest correlation with the SCS was within the 'fingerprint region'. SCC class had a significant (p < 0.05) effect on 639 spectral wavenumbers. In particular, some spectral wavenumbers within the 'fingerprint region' were highly affected by the SCC class. The data were collected from only one province in China, so the generalisability of the findings may be limited. SCC had close relationships with milk spectral wavenumbers related to important milk components or chemical bonds.

Effects of oral administration of lipopolysaccharide derived from Pantoea agglomerans on innate immunity of mammary glands in dairy goats

This study aimed to evaluate the effect of orally administered lipopolysaccharide (LPS) derived from Pantoea agglomerans (LPSpa) on innate immune functions, including the concentrations of antimicrobial components and interleukin (IL)-10 in goat milk, for the prevention of goat mastitis. Twelve Tokara goats were divided into two groups of six goats. Goats in the LPSpa and control groups were orally administrated with 0.4 g/kg dextrin with or without 0.02 mg/kg LPSpa for 7 days (day 0–6), respectively. After treatment (i.e., day 7), 1 μg LPS from Escherichia coli O111 (LPSec) was infused into one side of the udder in both groups to induce mastitis. Milk from all sides of the udder, saliva, and feces were collected on days 0 and 7. After LPSec infusion into the udders, milk was collected from the infused side of the udder on days 8, 10, and 12. Milk yields and somatic cell counts were recorded during the examination period. The concentrations of immunoglobulin (Ig) A in saliva, feces, and milk and the concentrations of lactoferrin, goat β defensin-1 (GBD1), S100A7, and IL-10 in milk were measured. After LPSpa oral administration, the concentrations of GBD-1 and IL-10 in the milk of the LPSpa group were significantly higher on day 7 than those in the control group, and the concentration of IgA in the feces tended to be higher than that in the control group. After LPSec intramammary infusion, S100A7 concentration on day 12 was significantly lower in the LPSpa group than in the control group. These findings suggest that the oral administration of LPSpa may prevent mastitis by increasing the concentration of GBD1 in milk.

Utilizing intramammary Melaleuca alternifolia as an organic internal sealant for dry-off therapy in Murrah buffaloes.

The effects of intramammary dry cow therapy based on the administration of 5% Melaleuca alternifolia tea tree essential oil (TTO) as an internal teat sealant to Murrah cows were evaluated. A longitudinal prospective and retrospective negative control study was performed using 12 buffaloes from a total of 20 Murrah buffaloes on an organic farm, with the cow used as a control for herself. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for treatments with pure oil (TTO) and medication containing 5% TTO (O5) were determined. The buffaloes were clinically examined, and the teats were evaluated using thermography and ultrasound. Udder health was monitored during the first 100days in milk (DIM) using milk somatic cell count (SCC) and California mastitis test (CMT). Laboratory tests against standard strains Staphylococcus aureus ATCC®25,923™, Escherichia coli ATCC®25,922™, and wild bacterial strains showed maximum MIC values of 50 µL/mL for the TTO and O5 treatments. One wild-type S. aureus strain showed no MBC. No adverse effects were observed after the intramammary application of TTO. The CMT and SCC values were similar (P > 0.05) for all observations. The medication containing 5% TTO was effective in vitro and compatible with the intramammary tissue in vivo of Murrah buffaloes. TTO was safe, not inducing inflammatory processes or other modifications of the teat detectable by thermography or ultrasound. It was able to protect buffaloes during the dry period under field conditions, demonstrating potential use as a teat sealant for organic farms.

Effect of bovine subclinical mastitis on milk production and economic performance of Brazilian dairy farms

This review summarized the significant results from Brazilian studies published in peer-reviewed scientific papers about the effect of bovine subclinical mastitis (SM) on economic performance and milk production. Different approaches were considered for (i) disease detection (indirect measurement of somatic cell count (SCC) and directly using microbiological culture) and (ii) milk sampling strategy (mammary quarters, composite cow samples, and bulk milk tank). Globally, bovine mastitis is the most common disease of dairy herds, and the subclinical presentation is the most frequent. Dairy farmers usually underestimate the economic losses associated with SM because no visual changes in milk and quarters, udder, and systemic symptoms are observed. SM reduces milk yield and quality, reducing dairy herds’ profitability. The estimation of losses depends on the causative pathogen, the lactation stage, and the parity of affected cows. Thus, estimating the economic caused by SM in milk production and economic performance in dairy herds can be used to decide which mastitis control strategies to adopt. Mastitis control involves adopting specific measures associated with the characteristics of each herd, the period of the highest frequency of cases, the transmission form, and the profile of the pathogens involved in cases of intramammary infection. Thus, using individual SCC, the microbiological identification of pathogens causing SM, adopting efficient drying-off protocols, and other management practices are essential for mastitis control, improved milk quality, and greater profitability of dairy herds.

Increased Milk Yield and Reduced Enteric Methane Concentration on a Commercial Dairy Farm Associated with Dietary Inclusion of Sugarcane Extract (Saccharum officinarum).

(1) Background: The purpose of this study was to assess the influence of a natural sugarcane extract (Polygain™) on milk production, milk composition and methane emissions on a commercial dairy farm. (2) Methods: A three-week baseline was established for lactating Holstein × Friesian animals. Following this baseline period, these animals were fed Polygain™ at 0.25% of their estimated dry matter intake for 3 weeks. Methane concentration in the feed bin was determined at each milking using the Gascard NG Infrared Sensor (Edinburgh Sensors LTD). (3) Results: During the intervention phase milk yield increased significantly from 26.43 kg to 28.54 kg per cow per day, whilst methane emissions and bulk tank somatic cell counts decreased significantly in the intervention phase. For methane concentration, an average of 246 ppm during the baseline periods reduced to an average of 161.09 ppm during the intervention phase. For the bulk tank somatic cell counts, the average was observed at 283,200 during the baseline and reduced to an average value of 151,100 during the intervention phase. (4) Conclusions: The natural sugarcane extract was shown to have the potential to mitigate enteric methane emissions while also increasing production and animal wellbeing outcomes in a commercial dairy setting.

Longitudinal Study of Subclinical Mastitis in Sheep in Greece: An Investigation into Incidence Risk, Associations with Milk Quality and Risk Factors of the Infection.

The objectives of this work were (a) to describe the incidence risk of subclinical mastitis in dairy flocks throughout the milking period, (b) to present potential associations of subclinical mastitis with the quality of milk and (c) to identify risk factors for high-incidence risk of the infection. A longitudinal study was performed in 12 dairy sheep flocks in Greece. Mammary secretion samples from 240 ewes and bulk-tank milk samples were collected in four repeated visits over a period of six months for bacteriological, chemical and cytological examinations. Overall, the incidence risk of subclinical mastitis throughout the study period was 51.7%, and it varied among farms from 25.0% to 75.0%. The respective figure for staphylococcal subclinical mastitis was 48.8%. The incidence risk of recurrence of subclinical mastitis among ewes in the flocks was 35.4%. The most frequently identified bacteria from cases of subclinical mastitis were S. aureus and S. simulans; of the mastitis-causing staphylococcal isolates, 65.4% were biofilm-forming. Somatic cell counts in bulk-tank milk progressively increased as the lactation period advanced, with significant increases seen on the third and fourth visits to the farms. Somatic cell counts in bulk-tank milk correlated well with prevalence of subclinical mastitis in flocks. A significant inverse correlation and a significant positive correlation were seen for prevalence of subclinical mastitis versus total protein content or added water in bulk-tank milk. During multivariable analysis, younger age of newborns when taken away from the dam and consequently delayed start of milking of ewes, omission of anti-mastitis vaccination of ewes and lack of employed staff on the farms emerged to be significantly associated (positively) with increased incidence risk of subclinical mastitis.

Bovine CD14 Gene Polymorphism and its Association with Milk Yield, Milk Constituents and Somatic Cell Count in Holstein Friesian Crossbred and Gir Cows

Bovine CD14 Gene Polymorphism and its Association with Milk Yield, Milk Constituents and Somatic Cell Count in Holstein Friesian Crossbred and Gir Cows

A Monoblock Light-Scattering Milk Fat Percentage and Somatic Cell Count Sensor for Use in Milking Systems.

A monoblock light-scattering sensor, which is capable of measuring the fat content of milk and indicating the excess by which the somatic cell count (SCC) is over the permissible level, has been developed for installation in dairy systems. In order for the sensor to perform measurements when the milking machine is working in the "milk plug" mode, a flow-through unit is designed in the form of a pipe with a lateral cylindrical branch, in which milk accumulates so as to eliminate large bubbles and achieve continuity of the milk flow. The operation of the sensor is based on the registration of the angular intensity distribution of light scattered in the transparent cylindrical segment of the tube branch. A semiconductor laser with a wavelength of 650 nm is used as a light source for determining scattering in milk. The angular distribution of the scattered light intensity (scattering indicatrix) is recorded using an axial photodiode array. The fat content is determined by the average slope of the measured scattering indicatrix in the range of scattering angles 72-162°. The SCC level is estimated from the relative deviation of the forward scatter intensity normalized to the backscatter intensity with respect to uninfected milk. The sensor has been tested on a Yolochka-type milking machine.

The Performance and Metabolism of Dairy Cows Receiving an Ultra-Diluted Complex in the Diet during the Transition Period and Early Lactation.

This study evaluated the effects of feeding an ultra-diluted complex to dairy cows during the transition period and early lactation. Thirty multiparous pregnant dairy cows were blocked and randomly assigned to either a placebo control (CON) group or ultra-diluted complex (UD) group. The CON group received a placebo (basal diet + 40 g/cow/day of expanded silicate), while the UD group received the ultra-diluted complex (basal diet + 40 g/cow/day of PeriParto Transição-RealH, composed of ultra-diluted substances + vehicle: expanded silicate). Cows were evaluated from 30 days before the expected calving date until 60 days in milk (DIM) for sample and data collection. Post-partum dry matter intake (DMI) was not affected by the treatment. Cows fed UD had higher DMI relative to BW. Feeding UD increased milk lactose content and decreased milk protein content. Cows fed UD had lower somatic cell counts in the third and fourth week of lactation. Cows fed UD showed a tendency for higher liver health index. Using UD during the transition period and early lactation may benefit liver and udder health of dairy cows with no detrimental effect on milk performance.

Recording of culling reasons in Danish dairy cows

Culling in dairy cows has major impacts on production economy and animal welfare, and has been described and evaluated in many studies. Information about why a cow is culled (culling reason) may be useful for many different purposes. Still, the present study is the first to evaluate explanatory factors for recording of culling reasons. Danish dairy farmers are required to report the culling mode (slaughter, unassisted death, or euthanasia) to the Danish Cattle Database. Further, the reporting of one or two culling reasons – from a list of options – is possible but not mandatory. Data from 281,682 cows culled in Danish dairy herds in 2020 and 2021 were analyzed. The mean age at culling was 1,845 days, 83.3 % of the culled cows were slaughtered, 10.2 % died unassisted and 6.5 % were euthanized. In 66.8 % of the culled cows, the farmer had reported at least one culling reason. The most frequent culling reasons for slaughtered cows were milk production (29 % of all culling reasons reported), followed by reproduction (25 %), and udder health (16 %). For unassisted dead cows, metabolic/digestive disorders were most frequently reported (25 %), followed by unknown reasons (18 %), and udder health (15 %). For euthanized cows, accidents were most frequent (29 %), followed by locomotor disorders (18 %), and metabolic/digestive disorders (17 %). Culling mode, as well as culling reasons, differed by parity and breed. Results from a logistic regression model showed that the odds of at least one culling reason being reported was significantly higher in Jersey cows compared to other breeds. Compared to Holstein cows, the odds of a reason being reported was 2.5 times higher in Jersey cows. The odds increased with increasing parity of the cow. In herds with a high mean milk yield and a low somatic cell count, the odds of reporting a culling reason was higher than in herds with lower milk yield and higher somatic cell counts, and the odds of reporting a culling reason increased with an increasing number of disease treatments recorded per cow per year.

Quantitative Associations between Season, Month, and Temperature-Humidity Index with Milk Yield, Composition, Somatic Cell Counts, and Microbial Load: A Comprehensive Study across Ten Dairy Farms over an Annual Cycle.

This current study addresses the knowledge gap regarding the influence of seasons, months, and THI on milk yield, composition, somatic cell counts (SCC), and total bacterial counts (TBC) of dairy farms in northeastern regions of Iran. For this purpose, ten dairy herds were randomly chosen, and daily milk production records were obtained. Milk samples were systematically collected from individual herds upon delivery to the dairy processing facility for subsequent analysis, including fat, protein, solids-not-fat (SNF), pH, SCC, and TBC. The effects of seasons, months, and THI on milk yield, composition, SCC, and TBC were assessed using an analysis of variance. To account for these effects, a mixed-effects model was utilized with a restricted maximum likelihood approach, treating month and THI as fixed factors. Our investigation revealed noteworthy correlations between key milk parameters and seasonal, monthly, and THI variations. Winter showed the highest milk yield, fat, protein, SNF, and pH (p < 0.01), whereas both SCC and TBC reached their lowest values in winter (p < 0.01). The highest values for milk yield, fat, and pH were recorded in January (p < 0.01), while the highest protein and SNF levels were observed in March (p < 0.01). December marked the lowest SCC and TBC values (p < 0.01). Across the THI spectrum, spanning from -3.6 to 37.7, distinct trends were evident. Quadratic regression models accounted for 34.59%, 21.33%, 4.78%, 20.22%, 1.34%, 15.42%, and 13.16% of the variance in milk yield, fat, protein, SNF, pH, SCC, and TBC, respectively. In conclusion, our findings underscore the significant impact of THI on milk production, composition, SCC, and TBC, offering valuable insights for dairy management strategies. In the face of persistent challenges posed by climate change, these results provide crucial guidance for enhancing production efficiency and upholding milk quality standards.

Effects of different floor types on milk yield and its components and somatic cell count in Akkeci goats

Amaç: Bu araştırmada, Akkeçilerde farklı zemin tiplerinin (ızgara, kauçuk ve beton) laktasyon süt verimi ve bileşenleri ile somatik hücre sayısı üzerine etkisinin incelenmesi amaçlanmıştır. Materyal ve Metot: Araştırmanın materyalini 2-4 yaşlı, 11 baş dişi Akkeçi oluşturmuştur. Keçilerden kontrol sağımıyla elde edilen verilerden Trapez II yöntemiyle laktasyon süt verimi ve süresi hesaplanmıştır. Laktasyon dönemi boyunca alınan süt örneklerinde, sütte yağ (%), protein (%), laktoz (%), yağsız kuru madde (%), elektriksel iletkenlik (µS/cm), donma noktası (°C), yoğunluk (kg/m3) ve pH içerikleri ile somatik hücre sayısı (SHS) araştırılmıştır. Araştırmada zemin tipi, sağım zamanı ve laktasyon dönemleri arasındaki farklılıklar, faktöriyel düzende tekrarlanan ölçümlü varyans analizi tekniği ile değerlendirilmiştir. Araştırma Bulguları: Süt bileşenleri bakımından, pH hariç, üzerinde durulan tüm özelliklerde laktasyon dönemleri arasındaki farklılıklar istatistik olarak önemli bulunmuştur (p&amp;lt;0.05). Sütteki yağ (%) ve yağsız kuru madde oranı (%) bakımından yapılan varyans analizinde sağım zamanı x laktasyon dönemi interaksiyonu istatistik olarak önemli (p&amp;lt;0.05), pH değeri bakımından da zemin tiplerinin ortalamaları arasındaki farkların istatistik olarak önemli (p&amp;lt;0.05) olduğu bulunmuştur. Sonuç: Araştırmada uygulanan farklı zemin tiplerinin Akkeçilerde süt verimi ve bileşenleri ile somatik hücre sayısı üzerine istatistik olarak önemli bir etkisi bulunmamıştır (p&amp;gt;0.05). Sonuç: Araştırmada uygulanan farklı zemin tiplerinin Akkeçilerde süt verimi ve bileşenleri ile somatik hücre sayısı üzerine istatistik olarak önemli bir etkisi bulunmamıştır (p&amp;gt;0.05).

The effects of an inactivated vaccine against Staphylococcus spp. on udder health in primiparous dairy goats: A randomized controlled trial

Staphylococci are the primary pathogens causing clinical and subclinical mastitis in dairy goats. This randomized controlled trial (RCT) evaluates the impact of vaccination with VIMCO® (Hipra, Girona, Spain) on clinical mastitis (CM), gangrenous mastitis (GM), the occurrence of udder asymmetry, somatic cell count (SCC), total bacterial count (TBC) and 10-day average milk yield (10dMY) in primiparous goats. The RCT was performed on a commercial dairy goat farm with 3000 mainly Saanen goats from February to April 2022. A group of 350 pregnant primiparous goats (12 – 16 months of age) was randomly divided into a control group and a vaccinated group. The goats were followed from kidding until on average 72 days in milk (DIM). At on average 20 DIM, all primiparous goats were mixed into a group with 1600 non-vaccinated adult goats. At the first milking after kidding (T = 0), all primiparous goats were scored for clinical mastitis and udder asymmetry. After that, udder asymmetry was scored on T1 (on average 12 DIM) and T2 (on average 62 DIM). Gangrenous mastitis cases were recorded from the start of complete vaccination and during the entire trial period. In addition, individual daily milk yield was recorded automatically by the milking system, and somatic cell count (SCC) was determined once at T2. The prevalence of CM was significantly higher in the control group (5.6%) than in the vaccinated group (0.6%). There was a significantly higher prevalence of udder asymmetry in the control group (7.8%) compared to the vaccinated group (1.2%) at T0 and during the entire study period (16% in control group versus 7.6% in the vaccinated group). Dried-up udder halves and GM were rare and did not differ significantly between both groups. Also, the SCC measurement and the milk yield did not differ between the vaccinated and the control group. Altogether, we show that the VIMCO® vaccine prevents clinical signs of mastitis at the first milking after kidding and udder asymmetry during the first three months after kidding in primiparous goats. Therefore, the vaccine may contribute to udder health control. Effects on SCC, milk yield, the prevalence of dried-up udder glands and GM remain to be demonstrated.

Bovine Milk Proteome: Milk Fat Globule Membrane Protein Is the Most Sensitive Fraction in Response to High Somatic Cell Count.

The impacts of high milk somatic cell count (SCC) on different milk fractions are not well understood. In this study, proteins in milk exosomes, milk fat globule membrane (MFGM), and whey from cows with low (<105 cells/mL, CG) and high SCC (>5 × 105 cells/mL, HSG) were identified using a tandem mass tag proteomic approach. In total, 1568, 2160, and 1002 proteins were identified, with 65, 552, and 98 proteins being altered by high SCC in exosomes, MFGM, and whey, respectively. With high SCC, the exosome marker (ACTB) was increased in the exosomes of HSG. The main MFGM proteins (BTN1A1, PLIN3, FABP3, and MFGE8) and functional proteins (MUC1, IGSF5, TLR5, and CD36/14) were decreased, while the lipid/energy metabolism-related proteins were increased in the MFGM of HSG. The glycolysis-related proteins were increased in the whey of HSG. Also, the host defense/inflammation-related proteins were changed in three fractions under high SCCs. MFGM was the most sensitive fraction to a high SCC, followed by whey. These findings provide guidance for the early detection of unhealthy mammary glands.

Blood metabolic pattern and somatic cells dynamic in Achai and Holstein Friesian cows during transition period.

This study focused on assessing blood metabolites and somatic cell count (SCC) during the transition period in Achai and Holstein Friesian cows. Blood samples were collected from cows of both breeds on days -21, -14, -7 (pre-partum period), on day 0 (parturition day) and then on days 7, 14 and 21 (post-partum period). Additionally, milk samples were obtained on the day of parturition and on days 7, 14 and 21 post-partum for SCC assessment. Among Holstein cows, blood glucose levels showed a significant increase on day -21 before calving, and a decrease on the 14th and 21st days post-partum. Similarly, the blood triglycerides concentration exhibited a significant rise in Holstein cows 21 days before calving, while Achai cows experienced a significant decline in blood triglycerides on the day of parturition and throughout the entire post-partum period. Comparing Holstein and Achai cows, blood cholesterol was significantly higher in Holstein cows on day -21 before calving, whereas Achai cows had significantly lower blood cholesterol levels on the day of parturition. Regarding blood protein, Holstein cows exhibited significantly higher levels on day 14 post-partum, while Achai cows had lower protein levels 7 days before calving. The results further demonstrated that SCC was significantly elevated in Holstein cows on day 21 of parturition and lower on the day of parturition in Achai cows. Overall, the metabolic profile trend and SCC were comparable, yet the studied parameters were more pronounced in Holstein Friesian compared to Achai cows.

Relationship of Temperament during Milking with Milking Behavioural Features, Milk Yield and Udder Health of Crossbred Jersey Cows in Tropical Climate

Background: Milking behaviour of milch cows has notable impacts on their production efficiency. The present investigation is designed to explore the relationship of temperament while milking with other milking behavioural features, milk yield and udder health in crossbred Jersey cows. Methods: The study was done on crossbred Jersey cows (N=94) kept at ICAR-National Dairy Research Institute, Eastern Regional Station, Kalyani, West Bengal. The cows’ temperament score (TS) was judged on 5 points scale (1-docile, 5-aggressive). Calmer cows (TS-1 and 2) covered relatively higher (75.24%) proportions and no observation had shown for TS-5. Result: The temperament score was positively associated (P less than 0.01) with stepping/milking (0.72), flight speed (0.43) and exit score (0.33), while it was negatively associated (P less than 0.01) with milk yield (-0.64), milking duration (-0.61) and milk flow rate (-0.65). It was concluded from the above study that milking behavioural features are directly correlated with each other and production parameters. Dairy animals of calmer temperament were significantly high-yielders. The temperament of dairy animals did not significantly impact udder health as assessed through MCMT and somatic cell counts in milk.

Specific and non-specific effects of Mycobacterium bovis BCG vaccination in dairy calves.

Bovine tuberculosis (bTB) is a chronic disease mainly caused by Mycobacterium bovis, a zoonotic pathogen with economic significance as it leads to reduced milk and meat production, and high costs for control measures. The Bacillus Calmette-Guérin (BCG) vaccine, primarily used to prevent tuberculosis in humans, has also been studied for controlling bTB. While showing effectiveness in preventing M. bovis infection and disease in cattle, the BCG vaccine can induce non-specific effects on the immune system, enhancing responses to infections caused by unrelated pathogens, and also having non-specific effects on lactation. The aim of this study is to describe both the specific and non-specific effects of BCG vaccination in calves from a commercial dairy herd in central Chile. Diagnosis of M. bovis infection was performed through the IFNγ release assay (IGRA) using ESAT6/CFP-10 and Rv3615c antigens. The records of milk production, somatic cell count (SCC), clinical mastitis (CM) and retained placenta (RP) during the first lactation were compared between vaccinated and non-vaccinated animals. The breed (Holstein Friesian [HF] v/s HF × Swedish Red crossbred [HFSR]) and the season (warm v/s cold) were also analyzed as categorical explanatory variables. Results of IGRA showed significant differences between vaccinated and control groups, indicating a vaccine efficacy of 58.5% at 18 months post vaccination in HFSR crossbred animals. Although milk production did not vary, SCC and CM showed differences between groups, associated to the breed and the season, respectively. When analyzing CM and RP as a whole entity of disease, BCG showed protection in all but the cold season variables. Overall, the BCG vaccine induced protective specific and non-specific effects on health parameters, which may be influenced by the breed of animals and the season. These results provide new features of BCG protection, supporting initiatives for its implementation as a complementary tool in bTB control.

Serum metabolome differences associated with subclinical intramammary infection caused by Streptococcus agalactiae and Prototheca spp. in multiparous dairy cows

Mastitis is one of the most significant diseases in dairy cows and causes several economic losses. Somatic cell count (SCC) is often used as an indirect diagnostic tool for mastitis, especially for subclinical mastitis (SCM) where no symptoms or signs can be detected. Streptococcus agalactiae is one of the main causes of contagious mastitis, while Prototheca spp. is an alga inducing environmental mastitis that is not always correlated with increased milk SCC. The aim of this study was to evaluate the changes in the metabolomic profile of blood in relation to subclinical intramammary infection (sIMI) in dairy cows. In addition, differences due to the etiologic agent causing mastitis were also considered. Forty Holstein-Friesian dairy cows in mid and late lactation were enrolled in this study with a cross-sectional design. Based on the bacteriological examination of milk, the animals were divided into 3 groups: Group CTR (control group; n = 16); Group A (affected by SCM with IMI of Streptococcus agalactiae; n = 17); and Group P (affected by SCM with IMI of Prototheca spp.; n = 7). Blood samples were collected in tubes containing clot activator from jugular vein. The serum aliquot was stored until metabolomic analysis by 1H-NMR. Statistical analysis was conducted fitting a linear model with the group as fixed effect and SCC as covariate. Forty-two metabolites were identified and among them, 10 were significantly different among groups. Group A and P showed greater level of His and lactose, and lower level of acetate, Asn, and dimethylamine compared with Group CTR. Group A showed high level of Val, while the Group P showed also high level of Cit and methylguanidine, and lower level of 3-hydroxybutyrate, acetone, allantoin, carnitine, citrate, and ethanol. These metabolites were related to ruminal fermentations, energy metabolism, urea synthesis and metabolism, immune and inflammatory response, and mammary gland permeability. These results are suggestive of a systemic involvement of sIMI and that the metabolic profile of animals with SCM undergoes changes related to the etiological agent of mastitis.