The Rumen Microbiota Contributes to the Development of Mastitis in Dairy Cows.

Mastitis, a highly prevalent disease in dairy cows, is commonly caused by local infection of the mammary gland. Our previous studies have suggested that the gut microbiota plays an important role in the development of mastitis in mice. However, the effects of rumen microbiota on bovine mastitis and the related mechanisms remain unclear. In this study, we assessed the effects and mechanisms of rumen microbiota on bovine mastitis based on the subacute rumen acidosis (SARA) model induced by feeding Holstein Frisian cows a high-concentrate diet for 8 weeks. Then, the inflammatory responses in the mammary gland and the bacterial communities of rumen fluid, feces, and milk were analyzed. The results showed that SARA induced mastitis symptoms in the mammary gland; activated a systemic inflammatory response; and increased the permeability of the blood-milk barrier, gut barrier, and rumen barrier. Further research showed that lipopolysaccharides (LPS), derived from the gut of SARA cows, translocated into the blood and accumulated in the mammary glands. Furthermore, the abundance of Stenotrophomonas was increased in the rumen of SARA cows, and mastitis was induced by oral administration of Stenotrophomonas in lactating mice. In conclusion, our findings suggested that mastitis is induced by exogenous pathogenic microorganisms as well as by endogenous pathogenic factors. Specifically, the elevated abundance of Stenotrophomonas in the rumen and LPS translocation from the rumen to the mammary gland were important endogenous factors that induced mastitis. Our study provides a foundation for novel therapeutic strategies that target the rumen microbiota in cow mastitis. IMPORTANCE Mastitis is a common and frequently occurring disease of humans and animals, especially in dairy farming, which has caused huge economic losses and brought harmful substance residues, drug-resistant bacteria, and other public health risks. The traditional viewpoint indicates that mastitis is mainly caused by exogenous pathogenic bacteria infecting the mammary gland. Our study found that the occurrence of mastitis was induced by the endogenous pathway. Evidence has shown that rumen-derived LPS enters the mammary gland through blood circulation, damaging the blood-milk barrier and then inducing inflammation of the mammary gland in cows. In addition, a higher abundance of Stenotrophomonas in the rumen was closely associated with the development of mastitis. This study provides a basis for novel therapeutic strategies that exploit the rumen microbiota against mastitis in cows.

Intracellular Staphylococcus aureus inhibits autophagy of bovine mammary epithelial cells through activating p38α.

Staphylococcus aureus is a common pathogen of bovine mastitis which can induce autophagy and inhibit autophagy flux, resulting in intracellular survival and persistent infection. The aim of the current study was to investigate the role of p38α in the autophagy induced by intracellular S. aureus in bovine mammary epithelial cells. An intracellular infection model of MAC-T cells was constructed, and activation of p38α was examined after S. aureus invasion. Through activating/inhibiting p38α by anisomycin/SB203580, the autophagosomes, LC3 and p62 level were analyzed by immunofluorescence and western blot. To further study the detailed mechanism of p38α, phosphorylation of ULK1ser757 was also detected. The results showed that intracellular S. aureus activated p38α, and the activation developed in a time-dependent manner. Inhibition of p38α promoted intracellular S. aureus-induced autophagy flow, up-regulated the ratio of LC3 II/I, reduced the level of p62 and inhibited the phosphorylation of ULK1ser757, whereas the above results were reversed after activation of p38α. The current study indicated that intracellular S. aureus can inhibit autophagy flow by activating p38α in bovine mammary epithelial cells.

Dry cow therapy and early lactation udder health problems-Associations and risk factors.

Mastitis remains the most expensive disease of dairy cows, and antibiotic dry cow therapy (DCT) at dry-off is an important part of mastitis control. Regardless of the infection status, blanket DCT is administered to all quarters of all cows, which is controversial due to the worldwide problem of antimicrobial resistance. Even though selective DCT of only infected cows is a more sustainable approach, choosing animals for treatment is not always straightforward. Our aim was to evaluate whether the herd-level DCT approach is associated with early lactation udder health problems, taking into account the cow characteristics. The information source was 2015-2017 Dairy Herd Improvement data with 7461 multiparous cows from 241 Finnish dairy herds. Information on the herd-level DCT approach was obtained from farmers' questionnaire responses in 2017, and the three different approaches were selective DCT, blanket DCT, and no DCT. The statistical tool for the data analysis was a generalized linear mixed model with a random herd effect for binary outcomes and a linear mixed model with a random herd effect for a continuous outcome. The two binary outcomes were the odds of having high milk somatic cell count (SCC ≥ 200 000 cells/mL) on the first test-day within 5-45 days in milk (DIM) and the odds of mastitis treatment in early lactation up to 45 DIM. The third outcome was the mean milk lnSCC (× 1000 cells/mL) within 120 DIM. Selective DCT was the prevailing treatment practice in our data. Blanket DCT was associated with lower SCC after calving. Cows more likely to have high SCC after calving were older cows, cows with high average SCC during the previous lactation, and cows with high milk yield near dry-off. A mastitis treatment in the early lactation was more likely if, during the previous lactation, the cow had high average SCC, high peak milk production, or high milk yield near dry-off. Our findings indicate that DCT is still effective in mastitis control. Cows with high milk yield, especially near dry-off, and cows with persistently high SCC require attention when considering next lactation udder health.

Longitudinal study on the effects of intramammary infection with non-aureus staphylococci on udder health and milk production in dairy heifers.

We conducted a longitudinal study to evaluate the effect of non-aureus staphylococci (NAS) causing subclinical intramammary infections (IMI) on quarter milk somatic cell count (qSCC) and quarter milk yield (qMY). In total, 324 quarters of 82 Holstein Friesian heifers were followed from calving to 130 d in milk (DIM) and were sampled 10 times each at 14-d intervals. The IMI status of each quarter was determined based on bacterial culture results at the current and previous or next sampling day, or both. The qSCC was determined on each sampling day and the average qMY on sampling day was available through stored daily milk weight data in the management program of the automatic milking system. A transient IMI (tIMI) was defined as a case where a specific pathogen was isolated from a quarter on only one sampling day and not on the previous or next sampling day. When the same bacterial strain, as defined by random amplification of polymorphic DNA-PCR, was isolated from the same quarter on multiple sampling days, it was defined as a persistent IMI (pIMI) status on those sampling days; a pIMI episode was defined as the combination of multiple consecutive pIMI statuses with the same bacterial strain on different sampling days. During this study, 142 subclinical IMI with NAS occurred in 116 different quarters from 64 animals, yielding in total 304 NAS isolates belonging to 17 different species. The prevalence of NAS was highest in the first 4 DIM. Overall, the predominant species was Staphylococcus chromogenes (52% of the isolates), followed by S. epidermidis (9.2%), S. xylosus (8.2%), and S. equorum (5.9%). Staphylococcus chromogenes was the only species for which an effect on qSCC and qMY could be analyzed separately; the other NAS species were considered as a group because of their low prevalence. Eighteen out of 40 IMI (45%) caused by S. chromogenes persisted over at least 2 sampling days, whereas only 10 of 102 (9.8%) IMI caused by other NAS species persisted for at least 2 sampling days. The average duration of pIMI episodes was 110.4 d for S. chromogenes and 70 d for the other NAS species. Remarkably, 17 of the 18 pIMI episodes with S. chromogenes started within the first 18 DIM. The qSCC was highest in quarters having a pIMI with a major pathogen, followed by quarters having a pIMI with S. chromogenes, and a pIMI with other NAS. Transient IMI with other NAS or with a major pathogen caused a small but significantly higher qSCC, whereas the qSCC in quarters having a tIMI with S. chromogenes was not statistically different compared with noninfected quarters. No significant differences in qMY were observed between quarters having a pIMI or tIMI with S. chromogenes or with the other NAS species compared with noninfected quarters, despite the higher qSCC. Quarters having a pIMI with major pathogens showed significantly lower daily milk production. Surprisingly, quarters that cured from an IMI with S. chromogenes had a significantly lower qMY than noninfected quarters.

Effect of subclinical mastitis detected in the first month of lactation on somatic cell count linear scores, milk yield, fertility, and culling of dairy cows in certified organic herds.

It is well established that subclinical mastitis (SCM), characterized by somatic cell count (SCC) >200,000 cells/mL, has a negative effect on the productivity, reproductive performance, and survivability of cows from conventional dairy herds. However, in organic herds, where the use of antimicrobial drugs is restricted for the treatment and control of intramammary infections (IMI) in dairy cows, little is known about the effect of SCM on performance and survivability. The objective of this study was to evaluate whether SCM diagnosed during the first month of lactation was associated with SCC linear score dynamics, milk production, fertility, and culling of dairy cows in USDA-certified organic herds. We collected data from 2 organic herds in New Mexico and Texas. A total of 1,511 cows that calved between June 2018 and May 2019 were included in the study and were followed until month 10 of the current lactation. Cows with SCC >200,000 cells/mL in the first month of lactation were considered to have SCM. We used mixed linear regression models accounting for repeated measures to assess the effect of SCM on monthly milk production and SCC linear scores. We used Cox proportional hazards models to evaluate the effect of SCM on the risk of pregnancy and culling. We considered parity, farm, previous gestation length, stillbirth, twinning, dystocia, and 2- and 3-way interactions as potential confounders. Cows diagnosed with SCM during the first month of lactation produced less milk than cows without SCM. Cows with SCM had elevated SCC linear scores during their previous lactation and throughout the subsequent months of lactation compared to cows without SCM. The effect of SCM on SCC linear scores was more pronounced in multiparous than primiparous cows. Subclinical mastitis during the first month of lactation did not affect the likelihood of pregnancy during the first 300 d in milk. Cows with SCM in the first month were more likely to die or be culled during the 300 d of lactation than cows without SCM. We observed that elevated SCC in the first month of lactation had detrimental effects on the milk yield and survivability of dairy cows in USDA organic herds, but it did not affect reproductive performance. We demonstrated that cows with SCM diagnosed in the first month of lactation continued to have elevated SCC linear scores throughout their entire lactation, and that elevated SCC was carried over from the previous lactation.

Investigation of dairy cow performance in different udder health groups defined based on a combination of somatic cell count and differential somatic cell count.

Mastitis is still the costliest disease in milk production. In particular, its subclinical form, which may spread unnoticeably within a herd, is a major challenge. Somatic cell count (SCC) is broadly used as an indicator for mastitis and thus the basis for udder health management programmes, e.g. through dairy herd improvement (DHI) testing. Since recently, differential somatic cell count (DSCC, representing the combined proportion of polymorphonuclear neutrophils and lymphocytes as a percentage of total SCC) is available in addition. Our study was aimed to investigate dairy cow performance in four newly defined udder health groups (UHG) based on SCC and DSCC results from DHI testing. In total, 961,835 test-day results generated in Austria, China, Estonia, Germany, and Spain between January 2019 and March 2020 were available for data analyses. Cows were categorised into four UHG depending on test day SCC and DSCC results (UHG A: healthy/normal, ≤200,000 cells/mL and ≤65 %; B: suspicious, ≤200,000 cells/mL and >65 %; C: mastitis, >200,000 cells/mL and >65 %; D: chronic/persistent mastitis, >200,000 cells/mL and ≤65 %). Linear mixed effect models were used to compare the performance of cows between the UHG based on the parameters milk weight, energy-corrected milk, fat, protein, lactose, and estimated milk value. Highest performance was found for cows in UHG A and ranged between 21.4 (Austria) and 38.3 kg per cow and day (Spain). Interestingly, cows in group B were significantly less productive (0.9-2.4% less daily milk production) compared to those in group A. Cows in groups C (6.0-9.8% less daily production compared to group A) and D were, as expected, even less productive with a particularly significant drop for cows in group D (17.5-38.5% less daily production). These trends could be observed in all countries involved in this study. Proportions of cows in the four different UHG differed between countries, changed slightly within countries depending on season, differed depending on parity and days in milk, and were seen to vary hugely between herds. In conclusion, this study demonstrates changes in performance of dairy cows depending on their udder health status as defined based on the combination of SCC and DSCC. In particular cows in UHG B and D are of interest as they cannot be identified working with SCC only. Nevertheless, the actual udder health management measures that could be taken based on the new UHG still require further investigation.

Pathogen effects on milk yield and composition in chronic subclinical mastitis in dairy cows.

This study aimed to evaluate the effects of chronic subclinical mastitis (CSM) on milk production and component yields in dairy cows. A total of six herds located in the Midwest area of São Paulo State, Brazil were selected. Herds were visited once every 2 weeks to measure milk yield and to collect milk samples from lactating Holstein cows. Milk samples were collected at two stages (1 and 2), and each stage comprised three milk samplings. In stage 1, a total of 117 of 647 cows were diagnosed with CSM based on at least two of three repeated somatic cell counts (SCC) > 2000,000 cells/mL and positive bacterial milk culture results (BC). Cows with CSM were selected for the second stage. In stage 2, selected cows had quarter sampling aseptically collected for BC analyses prior to milking, and quarter milk yield was measured. Milk components (total protein, fat, lactose, and total solids) were measured using mid-infrared spectroscopy. Mammary quarters were considered healthy if all three repeated SCC results were ≤ 200,000 cells/mL and no bacterial growth was detected on BC. All quarters with positive bacterial growth were classified as having (non-chronic) subclinical mastitis when only one of three SCC results were > 200,000 cells/mL, and CSM when at least two of three SCC results were > 200,000 cells/mL. The effects of CSM by type of pathogen on milk and components yield were assessed using a linear mixed model. Mammary quarters with CSM caused by major pathogens had milk loss of 1.1 kg/quarter milking in comparison to healthy quarters. Milk losses were 0.8 and 1.3 kg/quarter milking when CSM was caused by Staphylococcus aureus or environmental streptococci, respectively. In addition, healthy quarters produced more milk components than quarters with CSM caused by major pathogens. Minor pathogens causing CSM (non-aureus staphylococci and Corynebacterium spp.) had no effect on milk yield. Quarters with CSM had lower milk and component yields when compared with healthy quarters. Milk losses varied according to the type of pathogen and were higher when associated with major pathogens such as S. aureus and environmental streptococci compared with healthy quarters.

Incidence of milk leakage after dry-off in European dairy herds, related risk factors, and its role in new intramammary infections.

The incidence of milk leakage (ML) after dry-off (DO) and related risk factors was studied in 1,175 dairy cows from 41 commercial herds in 8 European countries: Belgium, Czech Republic, Denmark, France, Germany, Italy, the Netherlands, and Spain. Milk leakage was assessed twice for 30 s each during 3 visits at 20 to 24 h, 30 to 34 h, and 48 to 52 h after DO. Information related to dry-cow management and udder health was collected at herd and cow level, including individual somatic cell count (ISCC) from test-day controls and occurrence of clinical mastitis cases from DO until 30 d in lactation. Mixed-effect logistic regression analyses were used to identify possible risk factors for ML and to study the association between ML and new intramammary infections. Intramammary infections were defined as clinical mastitis cases during the dry period and in the first 30 d in lactation or a rise in ISCC from before to after the dry period (threshold: 200,000 cells/mL) or both. Milk leakage was observed in 24.5% of the cows between 20 and 52 h after DO, where the herd incidence varied between 0.0 and 77.8%. The reduction in number of milkings in the weeks before DO had statistically significant effect on the ML incidence. When the milking frequency was reduced from 3 times/d to 2 or maintained at twice a day, cows had 11 (95% CI = 3.43-35.46) or 9 (95% CI = 1.85-48.22) times higher odds of leaking milk, respectively, compared with cows where the milking frequency was reduced from twice to once a day. Also, the milk production 24 h before DO was associated with ML incidence. Hence, cows with a milk production between 13 and 21 L or above 21 L had 2.3 (95% CI = 1.48-3.53) and 3.1 (95% CI = 1.79-5.3) times higher odds of leaking milk, respectively, compared with cows with a milk production below 13 L. A higher ML incidence was present in the group of cows with an average ISCC in the last 3 mo before DO ≥200,000 cells/mL (odds ratio = 1.7; 95% CI = 1.13-2.41) compared with cows with an average ISCC <100,000 cells/mL. Quarters with ML tended to have 2.0 times higher odds of developing clinical mastitis compared with quarters not leaking milk. Cows with ML tended to have 1.5 times higher odds of intramammary infections (i.e., an increase of ISCC or clinical mastitis) compared with cows without ML.

Effects of clinical mastitis and puerperal diseases on reproductive efficiency of dairy cows.

The objective of this study was to evaluate the effects of clinical mastitis (CM) occurring before or after the first AI postpartum, and puerperal diseases (PD) on the pregnancy per artificial insemination (P/AI), number of AI/conception, and days open (DO) of two different dairy herds (Girolando and Holstein). The CM, PD (retained placenta and metritis), and reproductive data were collected from two dairy farms throughout 1 year. Both farms were located in the southern region of Minas Gerais State, Brazil. One herd was composed of Girolando cows and the other of Holstein cows. Cows were inseminated after estrus detection or submitted to timed AI. Only CM cases (clots in milk accompanied or not by udder inflammation) that occurred before or after first AI postpartum (from calving until 35 days after the first AI) were considered. There were no effects of CM, PD, or both diseases on the reproductive efficiency of the Girolando herd. In the Holstein herd, a reduce P/AI and prolonged DO were verified for those affected by ≥ 2 CM cases. Holstein cows with CM also required more inseminations to become pregnant. A decrease in the P/AI and an increase in the number of AI/conception and DO were observed in cows of the Holstein herd that developed only CM, only PD, and for those diagnosed with both diseases. In summary, considering that some management differences exist between the two dairy farms, CM occurrence (before or after the first AI postpartum) and puerperal diseases negatively affected the reproductive efficiency of the Holstein herd. However, these diseases did not compromise the reproductive efficiency of the Girolando herd.

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.

Symposium review: Real-time continuous decision making using big data on dairy farms.

We are developing a real-time, data-integrated, data-driven, continuous decision-making engine, The Dairy Brain, by applying precision farming, big data analytics, and the Internet of Things. This is a transdisciplinary research and extension project that engages multidisciplinary scientists, dairy farmers, and industry professionals. Dairy farms have embraced large and diverse technological innovations such as sensors and robotic systems, and procured vast amounts of constant data streams, but they have not been able to integrate all this information effectively to improve whole-farm decision making. Consequently, the effects of all this new smart dairy farming are not being fully realized. It is imperative to develop a system that can collect, integrate, manage, and analyze on- and off-farm data in real time for practical and relevant actions. We are using the state-of-the-art database management system from the University of Wisconsin-Madison Center for High Throughput Computing to develop our Agricultural Data Hub that connects and analyzes cow and herd data on a permanent basis. This involves cleaning and normalizing the data as well as allowing data retrieval on demand. We illustrate our Dairy Brain concept with 3 practical applications: (1) nutritional grouping that provides a more accurate diet to lactating cows by automatically allocating cows to pens according to their nutritional requirements aggregating and analyzing data streams from management, feed, Dairy Herd Improvement (DHI), and milking parlor records; (2) early risk detection of clinical mastitis (CM) that identifies first-lactation cows under risk of developing CM by analyzing integrated data from genetic, management, and DHI records; and (3) predicting CM onset that recognizes cows at higher risk of contracting CM, by continuously integrating and analyzing data from management and the milking parlor. We demonstrate with these applications that it is possible to develop integrated continuous decision-support tools that could potentially reduce diet costs by $99/cow per yr and that it is possible to provide a new dimension for monitoring health events by identifying cows at higher risk of CM and by detecting 90% of CM cases a few milkings before disease onset. We are securely advancing toward our overarching goal of developing our Dairy Brain. This is an ongoing innovative project that is anticipated to transform how dairy farms operate.

Comparing effects of bovine Streptococcus and Escherichia coli mastitis on impaired reproductive performance.

In 2 epidemiological studies, we evaluated the effect of mastitis induced by gram-positive Streptococcus and gram-negative Escherichia coli on impaired reproductive performance in lactating Holstein cows. In the first study, 52,202 cows from 178 dairy farms throughout Israel were divided into groups based on infection before first artificial insemination (AI) with Streptococcus or E. coli, 3 groups with elevated somatic cell count (SCC) without infection by those pathogens [low SCC (200-400) × 103 cell/mL; medium SCC (401-1,000) × 103 cell/mL; high SCC, >1,000 × 103 cell/mL], and uninfected controls. Pregnancy per first AI (P/1stAI) and pregnancy rate at 300 d in milk (PREG 300) were analyzed by the GLIMMIX procedure (SAS); number of AI per pregnancy (AI/P), days open, and rest days (calving to first AI) were analyzed by the MIXED procedure (SAS Institute Inc., Cary, NC). Values of P/1stAI were similarly low for Streptococcus and E. coli (27-28%) versus 42% in controls; PREG 300 was lower for Streptococcus (76%) than for E. coli (79%) versus 88% for uninfected controls and a mean 83% for the elevated SCC groups. Days open and number of AI/P were higher than in controls and similar in Streptococcus and E. coli groups. The second study included 778 cows on 6 dairy farms; the cows were infected before first AI by Streptococcus or E. coli or uninfected. Resumption of cyclicity was determined by an automated activity-monitoring system, and data were sorted by time of infection before or after cyclicity resumed. The Streptococcus group had lower P/1stAI before and after cyclicity (26 and 27%, respectively) than the E. coli group (31 and 34%, respectively) and uninfected controls (42%). Notably, PREG 300 in the Streptococcus group before (73%) and after (67%) cyclicity was much lower than for the E. coli group (85 and 93%, respectively) and the controls (95%). A marked rise in day of cyclicity resumption (∼80 d) was observed in cows that were infected early on. Number of AI/P was higher in the mastitic groups than in uninfected controls. Uterine disease postpartum, although more prevalent among Streptococcus cows, did not substantially alter the larger reduction in P/1stAI and PREG 300 in Streptococcus versus E. coli cows. Thus, long-term Streptococcus-induced mastitis disrupted fertility more than short-term acute E. coli-induced mastitis, resulting in a much higher percentage of Streptococcus cows in late lactation that did not conceive due to reproduction failure.

Associations between udder health and culling in dairy cows.

Culling is an important management tool in dairy herds, as it affects herd economics and animal welfare. In relation to health, culling is usually studied as a consequence of health disorders, but it can also be regarded as a tool to manage health in the herd by making strategic culling decisions. In this study, we used data from the Danish Cattle Database in herd-wise survival analyses to investigate factors associated with culling, in relation to udder health, in 1,452 dairy herds. The data included milk yield, somatic cell counts (SCC), parity, and different disease related factors with a special focus on udder health. In each herd, observations and survival analyses were divided into five groups: mid lactation heifers, late lactation heifers, early lactation cows, mid lactation cows, and late lactation cows. The results showed that a high average milk yield reduced the culling hazard, and a number of risk factors (e.g., parity, a high SCC or treatment of mastitis) were associated with an increased hazard for culling. Importantly, the strength and direction of many of these associations was dependent on the lactation stage. The resulting coefficients were further analysed by principal component analysis and clustering to explore variations in culling risk factors amongst herds. In some herds, parity was an important factor for culling, while in other herds, average milk yield, SCC, or udder health were more important factors. However, clusters were substantially overlapping, indicating that the decision making process underlying culling is complex and multifactorial.

A cohort study of the effect of Streptococcus agalactiae on milk yield and somatic cell count in Norwegian dairy cows.

The primary objective of the present study was to estimate the effect of Streptococcus agalactiae intramammary infection on milk production and somatic cell count (SCC) in Norwegian dairy cows. A secondary objective was to assess differences in the effect of common Strep. agalactiae sequence types (ST) found in Norwegian dairy herds. We performed a cohort study combining registry data with sequence-type data from Strep. agalactiae isolates. Herds in which Strep. agalactiae had been detected in individual animals (bacteriological culture or quantitative PCR) between 2012 and 2015 were included. We accessed monthly test-day milk yield records for the entire period to compare milk yield and SCC between cows that were Strep. agalactiae positive and all other cows, within each herd. The study sample consisted of 150 herds, 15,757 cows, 30,850 lactations, and 204,126 test days. We evaluated the effects of Strep. agalactiae on test-day milk yield and SCC using mixed linear regression models, controlling for clustering by herd, cow, and lactation. Multilocus sequence typing of Strep. agalactiae was available for isolates from 86 herds. Additional models were fit to a subset of herds (n = 59) in which ST1, ST23, ST103, and ST196 had been found, to compare the effects of ST on milk production and SCC. In the period 3 to 2 mo before diagnosis, Strep. agalactiae-positive cows produced an average of 1.3 kg more DIM-adjusted milk/d than their negative herd mates. At the time of diagnosis, production was on average 0.13 kg less DIM-adjusted milk/d in Strep. agalactiae-positive cows than in negative cows; 2 to 3 mo after diagnosis, they produced 1.24 kg less DIM-adjusted milk/d than negative cows. Losses persisted for the rest of the investigated period. Cows with ST23, ST103, and ST196 followed a similar pattern as the overall analysis with respect to milk production, whereas ST1-affected cows produced similar amounts of milk before diagnosis as the negative cows. Cows with ST1 experienced the largest milk loss 1 to 2 mo after diagnosis but then recovered to some extent; for cows with ST103, the severe milk loss persisted for the rest of the investigation period. The cow-associated ST103 elicited a lower response in peak SCC compared with ST23, ST103, and ST196. The results indicate an effect of Strep. agalactiae on milk production and SCC. Production was lowest 2 to 3 mo after a positive sample. Peak SCC was reached the month before diagnosis, with notable differences between sequence types.

Estimating the impact of clinical mastitis in dairy cows on greenhouse gas emissions using a dynamic stochastic simulation model: a case study.

The increasing attention for global warming is likely to contribute to the introduction of policies or other incentives to reduce greenhouse gas (GHG) emissions related to livestock production, including dairy. The dairy sector is an important contributor to GHG emissions. Clinical mastitis (CM), an intramammary infection, results in reduced milk production and fertility, increases culling and mortality of cows and, therefore, has a negative impact on the efficiency (output/input) of milk production. This may increase GHG emissions per unit of product. Our objective was to estimate the impact of CM in dairy cows on GHG emissions of milk production for the Dutch situation. A dynamic stochastic simulation model was developed to simulate the dynamics and losses of CM for individual lactations. Cows receive a parity (1 to 5+), a milk production and a calving interval (CI). Based on the parity, cows have a risk of CM, with a maximum of three cases in a lactation. Pathogens causing CM were classified as gram-positive bacteria, gram-negative bacteria, or other. Based on the parity and pathogen combinations, cows had a reduced milk production, discarded milk, prolonged CI and a risk of removal (culling and mortality) that reduce productivity of dairy cows and therefore increase GHG emissions per unit of product. Using life cycle assessment, emissions of GHGs were estimated from cradle to farm gate for processes along the milk production chain that are affected by CM. Processes included were feed production, enteric fermentation, and manure management. Emissions of GHGs were expressed as kg CO2 equivalents per ton of fat-and-protein-corrected milk (kg CO2e/t FPCM). Emissions of cows with CM increased on average by 57.5 (6.2%) kg CO2e/t FPCM compared with cows without CM. This increase was caused by removal (39%), discarded milk (38%), reduced milk production (17%) and prolonged CI (6%). The GHG emissions increased by 48 kg CO2e/t FPCM for cows with one case of CM, by 69 kg CO2e/t FPCM for cows with two cases of CM and by 92 kg CO2e/t FPCM for cows with three cases of CM compared with cows without CM. Preventing CM can be an effective strategy for farmers to reduce GHG emissions and can contribute to sustainable development of the dairy sector, because this also can improve the income of farmers and the welfare of cows. The impact of CM on GHG emissions, however, will vary between farms due to environmental conditions and management practices.

Quantifying the effects of mastitis on the reproductive performance of dairy cows: A meta-analysis.

The objective of this study was to conduct a meta-analysis to quantitatively characterize the effects of mastitis on the reproductive performance of dairy cows as well as to identify factors that interact with this relationship. A total of 29 publications were identified that contributed 24, 41, 27, 38, and 13 trial results to the meta-analysis of how mastitis is related to time to first service (TFS), days open (DO), services per conception (SPC), pregnancies per insemination at first service (FSP/AI) and pregnancy loss (PL), respectively. The meta-analyses were conducted using multilevel linear mixed-effects models. Overall, high levels of heterogeneity were present and meta-regression models only explained a small amount of heterogeneity. Results suggest that cows with mastitis pre-first insemination experience, on average, an additional 13.29 d to first service [95% confidence interval (CI): 6.64, 19.95] when compared with cows with no mastitis in the same time period. Moreover, in relation to cows with no mastitis in the same time period, 22.34 additional DO (95% CI: 12.89, 31.79) were estimated, on average, for cows with clinical mastitis at pre-insemination leading to conception. Additionally, 32.41 added DO (95% CI: 20.58, 44.25) were estimated, on average, for cows with clinical mastitis at pre- or post-insemination leading to conception compared with cows with no mastitis in the same time period. Finally, 20.03 additional DO (95% CI: 3.11, 36.95) were estimated, on average, for cows with subclinical mastitis pre- or post-insemination leading to conception compared with cows with no mastitis in the same time period. Effect size estimates from the meta-regression models for SPC, in relation to cows with no mastitis in the same time period, suggest that, on average, SPC increases by 0.46 inseminations (95% CI: 0.30, 0.62) for a cow experiencing mastitis pre-insemination leading to conception. When mastitis occurs either pre- or post-insemination leading to conception, SPC is expected to increase, on average, by 0.72 inseminations (95% CI: 0.48, 0.95) compared with cows with no mastitis in the same time period. The estimated effect sizes for FSP/AI suggest a risk ratio of conceiving at first insemination of 0.90 (95% CI: 0.82, 0.99) for cows with mastitis diagnosed pre-first insemination with respect to cows with no mastitis in the same time period, and a risk ratio of 0.79 (95% CI: 0.72, 0.86) for cows diagnosed with mastitis either pre- or post-first insemination with respect to cows with no mastitis in the same time period. Publication bias was identified in 4 of the meta-analysis models (TFS, DO, SPC, and FSCR), but no influential trials were identified in any models; the reliability of the meta-analysis results should be interpreted carefully keeping these limitations in mind. Further meta-regression analysis would be valuable as additional studies are published that report other potential sources of heterogeneity.

Influence of bovine sub-clinical mastitis and associated risk factors on calving interval in a population of crossbred lactating cows in Sri Lanka.

A study was carried out to identify prevalence and risk factors for bovine subclinical mastitis (SCM) in crossbred lactating cows within the Kurunagala district of Sri Lanka. In this study, 283 crossbred cows (Jersey x Shahiwal) from randomly selected medium- and relatively large-scale dairy farms were screened for SCM. The Californian mastitis test (CMT) plus microbiological analyses were employed for screening. A pre-tested questionnaire was used to collect information on the cows and their management. When screening was based only on CMT, the prevalence of SCM was 49%, and it was 44% if based on both CMT and pathogen isolation. The isolated pathogens were Staphylococcus spp. (80%, 98/123), Escherichia coli (14%, 17/123), Streptococcus spp. (3%, 4/123) and Pasteurella multocida (3%, 4/123). The age, parity and milk yield showed positive correlations with SCM (p < 0.05). The prevalence of SCM was relatively high after the fifth parity (p = 0.03, odds ratio = 9.49). A positive correlation of increase in calving interval (more than 18 months) with SCM was observed. The prevalence of SCM on the dairy farms can be reduced by implementing more hygienic management practices.

Biochemical changes in saliva of cows with inflammation: A pilot study.

Saliva contains a variety of compounds that can change in local and systemic pathologies including inflammation. Although changes in acute phase proteins and markers of oxidative stress in saliva during inflammation in humans and different animal species have been described, no data exist about possible changes during inflammation in analytes in saliva of cows. The aim of the present study was to evaluate changes in selected salivary biomarkers of stress, inflammation and immune system, and oxidative stress in cows with inflammation. For this purpose, bovine mastitis was used as model. Saliva and serum from 18 clinically healthy cows and 18 cows with clinical mastitis were used in the study. A panel of analytes integrated by alpha-amylase, cortisol, haptoglobin, adenosine deaminase, cholinesterase, total antioxidant capacity, lactate, and uric acid was measured in all samples and differences between the two groups of animals were evaluated. Significant increases in cortisol, alpha-amylase, uric acid, lactate and significant decreases in cholinesterase were detected in saliva of cows with mastitis. These results indicate that that cows with mastitis show changes in salivary biomarkers that reflect presence of stress, inflammation and oxidative stress in the animals.

Bovine fetal mesenchymal stem cells exert antiproliferative effect against mastitis causing pathogen Staphylococcus aureus.

Staphylococcus aureus is the most commonly isolated pathogen from clinical bovine mastitis samples and a difficult pathogen to combat. Mesenchymal stem cells (MSC) are multipotent progenitor cells equipped with a variety of factors that inhibit bacterial growth. The aim of the present study was to evaluate the in vitro antibacterial potential against S. aureus of conditioned medium (CM) from MSC derived from fetal bovine bone marrow (BM-MSC) and adipose tissue (AT-MSC). BM-MSC, AT-MSC and fetal fibroblasts (FB) cultures were activated by infection with S. aureus. Bacterial growth was evaluated in presence of CM, concentrated CM (CCM), activated CM (ACM) and concentrated ACM (CACM) from BM-MSC, AT-MSC and FB. Gene expression of ß-defensin 4A (bBD-4A), NK-lysine 1 (NK1), cathelicidin 2 (CATHL2), hepcidin (HEP) and indoleamine 2,3 dioxygenase (IDO) and protein expression of bBD-4A were determined in activated and non-activated cells. The majority of BM-MSC and AT-MSC expressed CD73, Oct4 and Nanog, and were negative for CD34. Growth of S. aureus decreased when it was exposed to CM from BM-MSC, AT-MSC and FB. Moreover, growth of S. aureus in CCM, ACM and CACM was lower compared to controls of CM from BM-MSC and AT-MSC. Activated AT-MSC increased mRNA levels of bBD4A and NK1, and protein levels of bBD4A in CM. Thus, CM from fetal bovine BM-MSC and AT-MSC has the capacity to reduce in average ~30% of S. aureus relative growth under in vitro conditions. The in vitro antibacterial effect of fetal bovine MSC may be mediated by bBD4A and NK1 activity.

Effect of intramammary infection with non-aureus staphylococci in early lactation in dairy heifers on quarter somatic cell count and quarter milk yield during the first 4 months of lactation.

A longitudinal study was conducted to assess to what extent intramammary infection (IMI) with non-aureus staphylococci (NAS) within the first 4 d after calving in dairy heifers affects quarter milk yield (qMY) and quarter milk somatic cell count (qSCC) during the first 4 mo of lactation. In total, 324 quarters from 82 Holstein Friesian heifers from 3 commercial dairy herds equipped with an automatic milking system were included and followed from calving up to 4 mo in lactation. The automatic milking system allowed us to precisely determine the daily qMY. A milk sample from each quarter was collected in early lactation (between 1 and 4 d in milk) for bacteriological culturing and measurement of the qSCC. Subsequently, milk samples were taken on a biweekly basis for measurement of the qSCC. The milk prolactin level in early lactation was measured, and the relation with NAS IMI was determined. Overall, NAS IMI in early lactation caused only a slight but significant increase in qSCC compared with milk from noninfected quarters during the first 4 mo in lactation, whereas no significant difference in daily qMY was present between NAS-infected and noninfected quarters. The milk prolactin level in early lactation did not differ between NAS-infected and noninfected quarters either. Our data suggest that IMI with NAS (as a group) present shortly after calving do not have an adverse effect on later production. The milk prolactin concentrations were not dissimilar between NAS-infected and noninfected quarters and thus cannot explain why NAS-infected quarters do not produce less than noninfected quarters.