Mitochondrial function of dairy calf lymphocytes from birth to immunologic maturity.

The inability of dairy calves to fully respond to immune stimuli until they reach maturity at 6 mo of age severely limits the use of parenteral vaccines to protect calves against disease. Immune responses are metabolically demanding, and immune cells rely on mitochondrial metabolites for their functionality. Due to the essential role of mitochondria in driving T-cell responses necessary for vaccine efficacy, we hypothesized that the mitochondrial function of dairy calf lymphocytes changes with age, from birth to immunologic maturity. In this cross-sectional study, groups of dairy calves (n = 4/group) were blood sampled at birth before colostrum intake and at 1, 2, 3, 4, 6, 8, 16, and 24 wk of age. Mid-lactation adult cows (n = 4) were also sampled to reference fully mature immune cell populations. B, CD4+, CD8+, and γδ T lymphocytes were enriched using magnetic-activated cell sorting, and their mitochondrial function was assessed with an extracellular flux analyzer. Non-mitochondrial oxygen consumption, basal respiration, maximal respiration, spare respiratory capacity, proton leak, and the oxygen consumption rate (OCR) to extracellular acidification rate (ECAR) ratio were reported. Results were compared among groups using a Kruskal-Wallis test. The OCR to ECAR ratio is an indicator of the relative proportions of oxidative phosphorylation and aerobic glycolysis which is associated with effector functions in lymphocytes. The ratio was lower in 0 wk than adults in CD4+ T-cells. For CD8+ T-cells, the OCR to ECAR ratio for the 2 wk group was lower than the 3 wk group. A lower OCR to ECAR ratio indicates more reliance on glycolytic metabolism than oxidative phosphorylation. Maximal respiration is an indication of mitochondrial efficiency and is often associated with mitochondrial mass. For γδ T-cells, the 3 wk group had higher maximal respiration than the 16 wk group, whereas for B cells maximal respiration was higher in the 1 wk compared with the 16 wk group. Basal respiration indicates all cell functions that require oxygen and was lower in the 0 wk group than the 1 wk and 3 wk groups for CD4+ T-cells. γδ T-cells exhibited lower basal respiration in the 2 wk group than the 24 wk one. Although we found minimal differences in the mitochondrial outcomes reported from non-stimulated lymphocytes from birth through 6 mo of age and mid-lactation adults who served as mature immune cell populations, these results align with previous reports from weaning aged calf and adult CD4+ T-cells. In conclusion, there was insufficient evidence to suggest that the mitochondria in the lymphocytes of dairy calves from birth through immunologic maturity had functional changes associated with age. In conclusion, the capacity of unstimulated calf mitochondria to perform oxidative phosphorylation is not associated with age.

Zinc about it - zinc and calf immunity.

Micronutrients, such as vitamins and trace minerals, are critical for supporting growth, performance, health and maintaining redox balance. Zinc (Zn), an essential micronutrient, aids the functioning of innate and adaptive immune cells. This scoping review aims to assemble and evaluate the evidence available for the role of Zn within calf immunity. Relevant literature was identified within Web of Science, PubMed, and CABI using search terms specific to the major innate and adaptive immune cell populations. There was no evidence that Zn supplementation altered neutrophil, natural killer cell, or T-cell functions. However, there was limited evidence to support Zn supplementation with reduced monocyte numbers, but there was no evidence to associate the monocytopenia with improvements in monocyte function. There is moderate evidence to suggest that Zn supplementation was beneficial for maintaining epithelial barriers of integumental and mucosal surfaces. The evidence supports supplementation above the current industry recommendations for improving immunoglobulin (Ig) production, with the strongest results being observed for IgG and IgM. Moreover, Zn supplementation was associated with reduced proinflammatory cytokine production, which may reduce inflammation-associated hypophagia and warrants further investigation. Furthermore, Zn reduced the duration of clinical signs in animals facing respiratory disease and diarrhea. However, consensus is needed about the optimal dose, route, and Zn formulation most appropriate for supporting immunity. In conclusion, while the literature supports that Zn could enhance calf immunity, there is insufficient evidence to adequately determine the extent to which Zn impacts innate immune cell and T-cell functions. Determination of the immune cell functions susceptible to modification by Zn supplementation is an important knowledge gap for enhancing the understanding of Zn and calf immunity.

Effect of F-isoprostane class on cow peripheral blood neutrophil microbicidal function in vitro.

Isoprostanes (isoP) are formed during conditions of oxidative stress (OS) through the oxidation of cell membrane fatty acids. Different classes of isoP are formed depending on the fatty acid being oxidized but the biological activity of these molecules in innate immune cells is poorly understood. Thus, the objective of this study was to compare in vitro the effects of F2- and F3-isoP on neutrophil microbicidal functions. We isolated neutrophils from 6 dairy cows and incubated them for 8 h at various concentrations of F2- and F3-isoP. Then, microbicidal function was assessed in terms of phagocytosis, respiratory burst, myeloperoxidase activity, and extracellular trap formation. In vitro supplementation with F3-isoP enhanced microbicidal capabilities whereas supplementation with F2-isoP decreased or did not impact these microbe killing functions. Hence, favoring the production of F3- over F2-isoprostanes may be a strategy to augment neutrophils' functional capacity during OS conditions. This should be tested in vivo.

Graduate Student Literature Review: Role of antioxidants in calf immunity, growth, and health.

The neonatal period for dairy calves is crucial for immune, metabolic, and physical development, which opens a window of disease susceptibility. Although the industry has relied on tools such as colostrum and vaccination to support early life immunity, there are several challenges when vaccinating neonatal calves: (1) the inability to mount an effective immune response, (2) interference with maternal antibodies, and (3) oxidative stress (OS). Oxidative stress, which is characterized as an imbalance of pro-oxidants to antioxidants, results in cellular oxidative damage or dysfunction, or both.. Oxidative stress has become a topic of interest in the neonatal period because it negatively affects lymphocyte function, which might affect vaccine response. Widely studied in mature cattle, antioxidant supplementation has the potential to improve reduction-oxidation balance and immune response. Evidence supporting the use of antioxidants such as vitamins and minerals in neonatal calves is far scarcer but necessary to optimize immunity and disease resistance. This review summarizes research on the effect of antioxidant supplementation on calf immunity, health, and productivity and highlights remaining gaps in knowledge. Overall, micronutrient supplementation, including vitamins and minerals, in preweaning and postweaning calves improved immune responses but there is conflicting evidence supporting the subsequent positive effect on calf health and growth performance.

Effect of parenteral micronutrient supplementation at birth on immunity, growth, and health in pre-weaning dairy heifers.

This randomized clinical trial aimed to determine the extent to which injectable micronutrient supplementation at birth can improve intranasal vaccine response by ameliorating oxidative stress in dairy calves from birth to weaning. For this, 120 Holstein heifer calves were enrolled at birth and randomly allocated into one of 4 groups. The 4 groups included 3 commercially available micronutrient supplements (Selenium, Copper, Zinc, and Manganese; Selenium & Vitamin E; and Vitamins E, A, and D) and one control (saline). Calves received an intranasal vaccine against the respiratory viruses parainfluenza 3, bovine herpesvirus type 1 (BHV-1), and bovine respiratory syncytial virus (BRSV) within the first wk of life. Weight (BW) and hip height (HH) were recorded, and a blood sample and nasal secretion sample were collected at birth before treatment and vaccine administration as well as weekly until weaning at 8 wk. Health scores, including thoracic ultrasound assessment, were recorded weekly from wk 1 to wk 8. Farm treatment records were collected after the completion of the study. Serum micronutrient concentrations were determined from birth to weaning to identify micronutrient status, and serum blood metabolites were analyzed as markers of nutrient utilization. Redox balance was determined in serum as a ratio of reactive oxygen and nitrogen species (RONS) to antioxidant capacity (AOP), known as the oxidant status index (OSi). Intranasal vaccine response was quantified as anti-BRSV and anti-BHV-1 immunoglobulin A (IgA) concentrations in nasal secretions. Linear mixed models with repeated measures were built for the following outcome variables: micronutrient concentrations, blood metabolites, redox balance, IgA concentrations, BW, and HH. Pre-planned contrasts of control vs supplemented were also built for the primary outcome of IgA concentrations. A logistic regression mixed model was built for health events and treatment of disease. Serum selenium concentrations were greater in calves receiving supplements containing Se throughout the first 4 wk of life. However, we did not observe any consistent differences in the other micronutrients. The metabolic biomarkers indicate that supplemented calves had better energy status, as suggested by lower BHB and nonesterified fatty acids (NEFA) concentrations. Supplemented calves showed improved redox balance, as indicated by lower OSi throughout the first wk of life. Calves supplemented with antioxidants at birth had higher anti-BRSV IgA than control calves. Our results indicate an improved immune response to vaccines in calves supplemented with antioxidants at birth. However, this did not translate to growth and health performance as there were no differences in average daily gain (ADG) or incidence of health events throughout the pre-weaning period. This study provides evidence that improving the antioxidant capacity might improve vaccine response, and further research is required to investigate the appropriate frequency and dose of supplementation to improve calf growth and health.

Metabolic Factors at the Crossroads of Periparturient Immunity and Inflammation.

Periparturient cows have the highest risk for disease and culling in the adult dairy herd. This risk is compounded by the multiple physiological changes of metabolism and immune function occurring around calving that alter the cow's inflammatory response. In this article, the authors summarize the current knowledge on immunometabolism in the periparturient cow, discussing major changes in immune and metabolic function around parturition that will facilitate the assessment of periparturient cow management programs.

Association of maternal late-gestation lipid mobilization and their offspring's disease risk during the pre-weaned period and performance through first lactation: A cohort study in a dairy herd.

Introduction: Excessive maternal lipid mobilization in late gestation may impact the immune function of the newborn. However, the long-term effects remain unknown. The objective was to explore associations between excessive maternal lipid mobilization in the last 2 weeks of gestation with offspring health and performance. Methods: A retrospective study was performed including 1,511 calves (heifer = 692, bull = 819) born between 2015 and 2020 in one MI farm. Plasma non-esterified fatty acids (NEFA) was measured from cows 7 to 14 d before calving. Calves were categorized in 2 groups based NEFA concentration: physiological lipid mobilization (PLM = 1,373; NEFA <0.3 mM) and excessive lipid mobilization (ELM = 138; NEFA ≥0.3 mM). Calf records were obtained from the herd's management software. Outcomes of interest were the hazard of pre-weaned digestive and respiratory disease, pre-weaned ADG, age at first breeding and calving, first lactation 305 d mature equivalent milk yield (305ME), and survival until first calving. Statistical models included dam NEFA category adjusted by year and season of birth, parity of the dam, and sex of the calf. Cox proportional analysis was used to determine the hazard of a pre-weaned health event, first breeding, and first calving. Linear regression was used to evaluate ADG and 305ME. The survival until first calving was analyzed with logistic regression. Results and discussion: No difference was detected in the hazard of diarrhea (HRPLM vs. ELM = 1.06; 95% CI = 0.82-1.38) and respiratory disease (HRPLM vs. ELM = 1.29; 95% CI = 0.79-2.10) by NEFA category in the pre-weaned period. Also, no difference was detected for the LSM (±SE) of pre-weaned ADG (PLM = 0.77±1.55, ELM = 0.72±2.76 kg/d). In heifers, the hazard for first breeding favored the PLM group (HRPLM vs. ELM = 1.59; 95% CI = 1.18-2.12), with a reduced median age at first breeding (PLM = 400 d, 95% CI = 397-402; ELM = 412 d, 95% CI = 404-421). However, NEFA category was not associated with the hazard of first calving (HRPLM vs. ELM = 0.94; 95% CI = 0.69-1.27), first lactation 305ME (PLM = 16,665±165 kg; ELM = 16,256±532), the odds of presenting at least 1 health event in the first lactation (ORPLM vs. ELM = 0.78; 95% CI = 0.41-1.49), or the odds of leaving the herd before first calving (ORPLM vs. ELM = 1.21; 95% CI = 0.56-2.02). Overall, dam ELM affected the hazard of first breeding but no other indicators of health or long-term performance. However, associations between maternal lipid mobilization and calf outcomes cannot be excluded, as the NEFA cut-off used has not been established as a predictor of offspring health and performance.

The effect of heat treatment on colostral and newborn calf redox status and oxylipid biomarkers.

Newborn calves experience altered redox balance upon transition to extrauterine life. In addition to its nutritional value, colostrum is rich in bioactive factors, including pro- and antioxidants. The objective was to investigate differences in pro- and antioxidants as well as oxidative markers in raw and heat-treated (HT) colostrum and in the blood of calves fed either raw or HT colostrum. Eleven colostrum samples (≥8 L) of Holstein cows were each divided into a raw or HT (60°C, 60 min) portion. Both treatments were stored for <24 h at 4°C and tube-fed in a randomized-paired design at 8.5% of body weight to 22 newborn female Holstein calves within 1 h after birth. Colostrum samples were obtained before feeding, and calf blood samples were taken immediately before feeding (0 h) and at 4, 8, and 24 h after feeding. All samples were analyzed for reactive oxygen and nitrogen species (RONS) and antioxidant potential (AOP), from which the oxidant status index (OSi) was calculated. In 0-, 4-, and 8-h plasma samples, targeted fatty acids (FA) were analyzed using liquid chromatography-mass spectrometry, and oxylipids and isoprostanes (IsoP) using liquid chromatography-tandem mass spectrometry. Results for RONS, AOP, and OSi were analyzed by mixed-effects ANOVA or mixed-effects repeated-measures ANOVA, for colostrum and calf blood samples, respectively, whereas FA, oxylipid, and IsoP were analyzed using false discovery rate-adjusted analysis of paired data. Compared with control, HT colostrum showed lower RONS [least squares means (LSM) 189, 95% confidence interval (95% CI): 159-219 vs. 262, 95% CI: 232-292) relative fluorescence units] and OSi (7.2, 95% CI: 6.0-8.3 vs. 10.0, 95% CI: 8.9-11.1), but AOP remained unchanged (26.7, 95% CI: 24.4-29.0 vs. 26.4, 95% CI: 24.1-28.7 Trolox equivalents/µL). Changes in colostrum oxidative markers due to heat treatment were minor. No changes in RONS, AOP, OSi, or oxidative markers were detected in calf plasma. In both groups of calves, plasma RONS activity declined considerably at all postfeeding time points compared with precolostral values, and AOP reached its maximum 8 to 24 h after feeding. Generally, oxylipid and IsoP plasma abundance reached nadirs at 8 h post-colostrum in both groups. Overall, effects due to heat treatment on redox balance of colostrum and newborn calves and on oxidative biomarkers were minimal. In this study, heat treatment of colostrum reduced RONS activity but did not lead to detectable changes in calf oxidative status overall. This indicates that there were only minor changes in colostral bioactive components that could alter newborn redox balance and markers of oxidative damage.

Development of a bovine continuing education program for early-career veterinarians to address clinical service shortage.

There is currently a shortage of production animal veterinarians worldwide. Access to adequate continuing education (CE) increases retention of health-care workers in rural areas. However, little information is available about the preferences of bovine veterinarians in their first years after graduation. Our objective was to design a readily available CE program tailored for recent veterinary graduates working in bovine medicine. For this, we conducted a cross-sectional survey to identify early-career bovine veterinarian needs and their preferences to access CE conducted while practicing full time. Subsequently, we conducted a second survey to triangulate their responses with the opinions of experienced veterinarians, where the experienced veterinarians ranked the relevance of the CE topics that resulted from the early-career veterinarian survey. We received a total of 132 valid responses from US veterinarians in their first 5 years after graduation, and 32 responses associated with bovine veterinarians with 10 or more years of experience. Our results showed that a combination of distance education and workshops to practice hands-on skills was the preferred method for accessing CE among early-career veterinarians. Furthermore, recent graduates were willing to commit 1 to 2 h/wk to distance education. From the list of 20 topics identified by early-career veterinarians, the experienced veterinarians ranked "calf/heifer management" and "immunology and vaccinology" as the most relevant ones for practice. With the information gathered from these surveys, we designed, implemented, and piloted a 180-h CE program on bovine health management that is delivered over 2 yr through asynchronous distance education and annual hands-on workshops. Participant feedback has been very positive. Overall, the survey results will serve to develop CE programs targeted to bovine veterinarians in their first years of practice. Future research is needed to evaluate this program's success in retaining the bovine veterinary workforce within the United States, particularly in rural underserved areas.

Comparison of calf morbidity, mortality, and future performance across categories of passive immunity: A retrospective cohort study in a dairy herd.

Four categories of transfer of passive immunity (TPI) were recently proposed in response to the widespread high preweaning morbidity and mortality risks in calves with adequate TPI when a dichotomous classification was used. Hitherto, however, the risks of preweaning morbidity and mortality and future performance among these TPI categories have not been compared. Thus, the objective of this retrospective cohort study was to compare dairy calf morbidity, mortality, growth until weaning, and reproductive efficiency until first calving among the categories of poor (<5.1 g/dL total protein), fair (5.1-5.7 g/dL), good (5.8-6.1 g/dL), and excellent (>6.2 g/dL) TPI. For this, the records from 4,336 dairy calves (2,272 female, 2,064 male) born January 2014 to April 2017 on a commercial dairy farm in Michigan were analyzed. These calves had been randomly selected for weekly serum total protein determination on calves 2 to 7 d old. Data from both sexes were used to evaluate preweaning health and mortality, whereas only the female's data were used to investigate average daily gain (ADG), reproductive performance, and first-lactation milk yield. For each calf, data regarding disease status, growth, and reproductive parameters were obtained from the farm's software database. Associations of TPI categories with disease events (diarrhea or pneumonia), reproduction indices (age at first insemination, successful insemination, and calving, and number of inseminations), first-lactation milk yield and ADG at weaning were evaluated by survival analysis and mixed models. Compared with calves with excellent TPI, calves in the inferior TPI categories showed increased risk of diarrhea: poor [hazard ratio (HR) = 1.49; 95% CI: 1.22-1.82], fair (HR = 1.32; 95% CI: 1.16-1.51), good (HR = 1.14; 95% CI: 1.02-1.29). However, the risk of pneumonia differed only between the calves in the poor and excellent TPI groups (HR = 1.39; 95% CI: 1.05-1.84). The preweaning mortality risk was also higher in calves with poor TPI (HR = 4.29; 95% CI: 1.98-9.27) compared with excellent TPI. However, mortality risks were not statistically different between calves with fair or good TPI and those with excellent TPI. Similarly, calves with poor TPI had a 64, 55, and 24% lower risk of reaching first insemination, successful insemination, or first calving, respectively. However, there were no differences in ADG, number of inseminations, or first-lactation 305-d mature equivalent milk production across TPI groups. Our results confirm the positive effects of optimal TPI in calf preweaning health and postweaning reproductive efficiency. The 4 proposed categories of TPI can assist in decreasing the incidence of diseases that occur in the first weeks of life (i.e., diarrhea), but their effect on other diseases or future performance might be more limited. Although conducted in one herd, this study can be used to illustrate the effect of TPI on future calf performance.

Case-control exercise challenge study on the pathogenesis of high serum gamma-glutamyl transferase activity in racehorses.

BACKGROUND: High serum γ-glutamyl-transferase (GGT) activity syndrome in racehorses has been associated with maladaption to exercise. Investigation of affected horses before and immediately after standard exercise may provide critical insight into the syndrome's pathophysiology. OBJECTIVES: To investigate blood biomarker changes in actively competing racehorses with high GGT activity associated with an exercise challenge. STUDY DESIGN: Case-control study. METHODS: High GGT case (age: 2-3 years) and normal GGT control (age: 2-7 years) pairs (3 Thoroughbred, 4 Standardbred pairs) at least 3 months into their training/racing season were included. Horses with a recent history of high GGT activity (≥50 IU/L) without additional biochemical evidence of liver disease were identified by veterinarians. Horses were tested again in the week prior to a planned exercise challenge to confirm persistent increases in GGT activity. Controls from the same stable with similar training/racing intensity and serum GGT activity ≤36 IU/L were matched with each case. Blood samples were obtained immediately before, 15 and 120 min after exercise. Pre-exercise serum samples were analysed for baseline select serum chemistries, selenium and vitamin E concentrations. Cortisol concentration and markers of oxidative status were measured in serum or plasma for all time points. Individual serum bile acid and coenzyme Q10 concentrations, plasma lipid mediator (fatty acids, oxylipids, isoprostanes) concentrations and targeted metabolomics analyses were performed using liquid chromatography-mass spectrometry. Serum viral PCR for equine hepaci- and parvovirus was performed in each animal. RESULTS: Cases had higher baseline concentrations of total glutathione, taurocholic acid, cortisol and cholesterol concentrations and higher or lower concentrations of specific oxylipid and isoprostane mediators, but there were no case-dependent changes after exercise. MAIN LIMITATIONS: Small sample size. CONCLUSIONS: Results indicated that glutathione metabolism was altered in high GGT horses. Enhanced glutathione recycling and mild cholestasis are possible explanations for the observed differences.

Changes in biomarkers of metabolic stress during late gestation of dairy cows associated with colostrum volume and immunoglobulin content.

The objective of this observational study was to compare the metabolic status of dairy cows during the last 6 wk of gestation based on colostrum volume and immunoglobulin content. For this, healthy Holstein cows were randomly selected from 3 commercial herds in Michigan. In each farm, 4 cohorts of 21 cows (1 per season), stratified by parity, were enrolled (n = 228). Cows were blood sampled weekly during the last 6 wk of gestation, and biomarkers related to nutrient utilization, oxidant status, and inflammation were quantified in serum. Cows were milked within 6 h of calving, and the volume of colostrum produced was recorded and an aliquot collected. Concentration of IgG, IgA, and IgM were measured by radial immunodiffusion. Cows were grouped into high or low colostrum producer, high or low IgG, high or low IgA, and high or low IgM. For volume category, we arbitrarily defined 6 L of colostrum (4 L for first and 2 L for second feeding of calves) as the cutoff point, whereas for IgG we used the industry standard of ≥50 g/L. To create groups of low and high IgM or IgA, we used the median of these immunoglobulin as the cutoff point. Colostrum volume was lowest in winter, but no differences were observed among parity groups. Conversely, colostrum IgG concentration was highest in fall and winter, but colostrum IgM was lowest at these seasons. However, colostrum immunoglobulin content only showed a negative weak correlation with volume (Spearman's correlation coefficient < -0.28). Compared with low colostrum producer, high colostrum producer cows had higher concentrations of antioxidant potential and ß-hydroxybutyrate, and lower cholesterol and oxidant status index. Cows with high IgG showed higher concentrations of glucose compared with low IgG. Cows with high IgA had higher concentrations of cholesterol, reactive oxygen and nitrogen species, oxidant status index, and total protein, whereas ß-hydroxybutyrate and glucose were lower compared with low IgA. Biomarkers of metabolic stress were not significantly different between high IgM and low IgM. Nevertheless, the differences observed did not result in differences in inflammatory status between animals in any of the colostrum variable categories analyzed, suggesting that physiological homeostasis was not disrupted during late gestation in association with the colostrum variables studied. Overall, the great variability observed in colostrum variables suggests that colostrogenesis is a complex and multifactorial process. However, our results suggest that greater availability of antioxidants during late gestation could support the production of higher volumes of colostrum, which needs to be explored in future trials.

Review: Salmonella Dublin in dairy cattle.

Salmonella enterica serovar Dublin (S. Dublin) is a bacterium host-adapted to cattle with increasing prevalence in dairy facilities. It can severely affect cattle health, producing high morbidity and mortality in young calves and reducing the performance of mature animals. Salmonella Dublin is difficult to control and eradicate from herds, as it can be shed from clinically normal animals. In addition, S. Dublin is a zoonotic bacterium that can be lethal for humans and pose a risk for human and animal health due to its multi-drug resistant characteristics. This review provides an overview of S. Dublin as a pathogen in dairy facilities, the risk factors associated with infection, and current strategies for preventing and controlling this disease. Furthermore, current gaps in knowledge are also discussed.

Peripheral biomarkers of oxidative stress in dogs with acute pancreatitis.

BACKGROUND: Oxidative stress is considered a pathomechanism of acute pancreatitis (AP), but no studies have extensively characterized oxidant status in dogs with naturally-occurring AP. HYPOTHESIS OR OBJECTIVES: Evaluate measures of oxidant status in dogs with AP and explore whether these measures correlate with AP severity. ANIMALS: Fifteen dogs with AP and 9 control dogs. METHODS: Prospective, controlled observational study. Plasma reactive metabolite (RM) concentrations, antioxidant potential (AOP), and urinary F2 isoprostane concentrations were measured in AP dogs and healthy controls. Severity of AP was assessed by length of hospitalization and 3 disease severity indices: canine acute pancreatitis severity (CAPS), modified canine activity index (M-CAI), and the acute patient physiologic and laboratory evaluation score (APPLEfull ). RESULTS: Reactive metabolite (RM) concentrations (median, 65 relative fluorescent units [RFU]/µL; range, 20-331 RFU/µL) and RM:AOP (median, 7; range, 4-109) were higher in AP dogs than healthy controls (median RM, 25 RFU/µL; range, 16-41 RFU/µL; median RM:AOP, 4; range, 2-7; P < .001 for both comparisons). Reactive metabolite (rS  = 0.603, P = .08) and RM:AOP (rS  = 0.491, P = .06) were not correlated with the duration of hospitalization or disease severity indices evaluated. However, disease severity indices did not predict mortality in our study. Normalized urine 2,3-dinor-8-iso-prostaglandin F2α concentrations were correlated with C-reactive protein (CRP; rS  = 0.491, P = .03), canine specific pancreatic lipase (Spec cPL; rS  = 0.746, P = .002), and CAPS (rS  = 0.603, P = .02). CONCLUSIONS AND CLINICAL IMPORTANCE: Oxidant status is altered in dogs with naturally occurring AP, but the clinical relevance of this finding is unknown.

Parenteral Antioxidant Supplementation at Birth Improves the Response to Intranasal Vaccination in Newborn Dairy Calves.

Newborn calves experience oxidative stress throughout the first month of their life, which is known to decrease lymphocyte functions relevant to vaccine responsiveness. Thus, this study aimed to determine the extent to which parenteral antioxidant supplementation given at birth improves the response to an intranasal viral vaccine in the first month of life of newborn dairy calves. For this, 21 calves were randomly assigned at birth to one of two commercially available antioxidant micronutrient supplements or a placebo group receiving 0.9% sterile saline (n = 7/group). Serum and nasal secretion samples were collected before administration of treatments and an intranasal vaccine against respiratory viruses (bovine herpesvirus type 1, bovine syncytial respiratory virus, and parainfluenza 3), and once weekly for the first four weeks of age. Systemic redox balance was determined in serum. Immunoglobulin A specific for bovine herpesvirus 1 and bovine syncytial respiratory virus was quantified in nasal secretions as a proxy to intranasal vaccine responsiveness. Our results showed that parenteral administration of antioxidants at birth improved calves' redox balance. Additionally, calves receiving antioxidant supplementation had higher concentrations of immunoglobulin A in their nasal secretions than calves in the control group. Thus, we conclude that supplementation of calves with antioxidants at birth could be a practical strategy to improve intranasal vaccine response. Future larger studies should evaluate the extent to which this increased mucosal response to intranasal vaccination could result in decreased calf morbidity and mortality.

Activity of sEH and Oxidant Status during Systemic Bovine Coliform Mastitis.

Bovine coliform mastitis presents treatment challenges because of systemic inflammation and oxidative stress. Soluble epoxide hydrolase (sEH) is a promising therapeutic target in conditions characterized by inflammation and oxidative stress but has not been evaluated in cattle. We compared sEH activity and oxidant status in healthy Holstein dairy cows to those with systemic coliform mastitis (n = 5/group) using complementary approaches. First, the activity of sEH on [3H]-trans-diphenyl-propene oxide (tDPPO) was assessed ex vivo using tissue homogenates (mammary, liver, and kidney). Second, the concentrations of sEH substrates and metabolites in plasma, milk, and urine were determined as an index of in vivo sEH activity. Oxidant status was assessed in serum and milk. Data were analyzed by non-parametric methods. Metabolism of tDPPO was greater in mammary tissues from cows with coliform mastitis compared to controls. In contrast, ratios of sEH substrates and metabolites predicted lower sEH activity in cows with coliform mastitis than controls. Milk oxidant status showed greater prooxidant levels in coliform mastitis cows. Cows with coliform mastitis exhibit increased sEH activity in mammary tissue; at the same time, milk oxidant status is increased. Future studies should characterize sEH activity and oxidant status patterns and explore therapies targeting sEH during coliform mastitis.

Impact of 2 Versus 1 Colostrum Meals on Failure of Transfer of Passive Immunity, Pre-Weaning Morbidity and Mortality, and Performance of Dairy Calves in a Large Dairy Herd.

Failure of transfer of passive immunity (FTPI) due to inadequate ingestion of colostral immunoglobulins by calves is associated with increased mortality and morbidity risks. Feeding calves a sufficient amount of quality-tested colostrum within the first hours of life is essential for successfully transferring passive immunity. Many farms have implemented a second meal of colostrum to maximize the opportunities for passive immunity transfer. However, excellent passive immunity can be achieved with a single feeding of sufficient quality-tested colostrum. Moreover, there is currently no evidence demonstrating the impact of a second colostrum feeding within 24 h of life in calves receiving adequate volumes of quality-tested colostrum in an initial feeding. Hence, the objective of this retrospective cohort study was to compare the risks of FPTI, pre-weaning morbidity and mortality, and growth and performance between dairy calves that received one or two feedings of colostrum. For this, the health and production records of a large dairy herd were analyzed. At this farm, newborn calves receive 3 L of quality-tested colostrum soon after birth, followed by another 2 L 5-6 h later. However, at times of shortages of colostrum, calves only receive the initial 3 L meal. The records of 2064 male and 2272 female calves were analyzed, where 4156 and 180 calves received 2 and 1 colostrum meals, respectively. Data from both sexes were included in the analysis of the risks of FTPI, morbidity, and mortality; however, only data from heifer calves were utilized for growth and performance analysis. Survival analysis, and logistic and linear regression models were used to investigate the impact of receiving two feedings of colostrum on calf FTPI status, morbidity, mortality, reproductive indices, pre-weaning average daily gain (ADG), and first lactation 305-d Mature Equivalent milk production (305ME). Calves that received two feedings of colostrum had lower odds of FTPI, a lower probability of being treated for respiratory disease, diarrhea, or any disease, and a greater pre-weaning ADG. However, there was no association between the number of colostrum feedings and pre-weaning mortality, and the probabilities of first insemination and first calving, although heifers receiving two colostrum feedings tended to receive fewer inseminations and to have a greater first lactation 305ME. Collectively, our results suggest that feeding calves a second feeding of colostrum 5-6 h after the initial feeding soon after birth could be an effective strategy to decrease FTPI and morbidity and optimize ADG in dairy calves pre-weaning.

Effect of preweaning disease on the reproductive performance and first-lactation milk production of heifers in a large dairy herd.

Raising replacement heifers represents a substantial cost in dairy farms, with reproductive efficiency being one of the main factors driving the total rearing cost. Diseases during the preweaning period, such as diarrhea or bovine respiratory disease (BRD), are reported at high incidence risks worldwide. However, the long-term effects of disease before weaning on productive and reproductive performance remain controversial. This retrospective cohort study explored the extent to which diseases such as diarrhea or BRD during the preweaning period affected average daily gain (ADG), herd removal, reproductive indices, and 305-d mature equivalent milk production (305ME) of replacement heifers. The health, growth, and production records of 2,272 female calves from a large dairy herd were used; 487 and 926 of the calves had BRD and diarrhea, respectively, before weaning. The reproductive variables age at first service, age at successful service, age at calving, and pregnancies per artificial insemination were calculated. Associations of disease status with reproduction indices, removal from herd, ADG, and 305ME were evaluated by survival analysis and mixed models. Heifers with a history of BRD before weaning were less likely to be inseminated or achieve first calving than heifers without BRD. However, BRD status did not change the age at first insemination of calving among those being inseminated or reaching first calving, respectively. There were also no differences in ADG, 305ME, and pregnancies per artificial insemination between heifers with and without a history of BRD. A history of diarrhea preweaning was not associated with changes in the probability of being inseminated, having a confirmed pregnancy, or reaching first calving. However, heifers affected by diarrhea required more inseminations to become pregnant. Diarrhea status was also associated with a 325-kg reduction in 305ME in the first lactation and a 50 g/d reduction in ADG. Collectively, our results demonstrate some long-term effects of diseases before weaning on the reproductive efficiency of heifers and first-lactation 305ME production, but with limited effect on the time to achieve critical reproductive performance indicators.

Rumination time around dry-off relative to the development of diseases in early-lactation cows.

Monitoring rumination time (RT) around the time of calving is an effective way of identifying cows at risk of disease in early lactation. However, this only allows for the identification of cows a few days before the onset of clinical signs; thus, effective preventive measures cannot be implemented. Recent research has suggested that biomarkers of immune and metabolic function measured at dry-off (DO) can predict higher disease risk in early lactation. Nevertheless, the extent to which RT around DO is associated with early-lactation disease risk remains unexplored. Thus, the objective of this study was to compare RT in the weeks before and after DO between cows that did and did not experience health disorders in early lactation. For this, we conducted an observational retrospective cohort study utilizing the records available from a large commercial dairy herd in which RT is recorded daily using an automated system. Daily RT from -7 to +14 d relative to DO from 2,258 DO cycles and their respective health records in the first 60 d in milk were used. Differences in RT between animals with and without a disease history were tested with the Student t-test with Bonferroni adjustment. Mixed linear regression analyses were performed to assess differences in RT around DO and the association of RT with the occurrence of mastitis, metritis, retained placenta, hyperketonemia, lameness, hypocalcemia, pneumonia, and displaced abomasum. Rumination time decreased abruptly at DO and remained lower for 3 to 4 d compared with the days before DO. On average, cows affected by hyperketonemia and lameness ruminated 9.83 ± 6.40 and 15.00 ± 6.08 min/d less than unaffected cows, respectively. Cows that developed lameness in the first 60 d in milk showed reduced RT from 1 to 3 d following DO compared with cows that were not diagnosed with lameness in early lactation. However, RT around DO was not associated with the occurrence of the other health disorders studied here. Our results demonstrate that DO is a stressful event for dairy cows resulting in decreased RT for several days. Furthermore, the association between RT around DO and some early-lactation diseases suggests that RT could be a useful tool to identify at-risk cows early enough to allow for preventive interventions. Further studies should investigate the diagnostic utility of incorporating RT data early in the dry period in the disease prediction algorithms of rumination sensors.

Oxidative Stress Compromises Lymphocyte Function in Neonatal Dairy Calves.

Dairy calves are unable to mount an effective immune response during their first weeks of life, which contributes to increased disease susceptibility during this period. Oxidative stress (OS) diminishes the immune cell capabilities of humans and adult cows, and dairy calves also experience OS during their first month of life. However, the impact that OS may have on neonatal calf immunity remains unexplored. Thus, we aimed to evaluate the impact of OS on newborn calf lymphocyte functions. For this, we conducted two experiments. First, we assessed the association of OS status throughout the first month of age and the circulating concentrations of the cytokines interferon-gamma (IFN-γ) and interleukin (IL) 4, as well as the expression of cytokine-encoding genes IFNG, IL2, IL4, and IL10 in peripheral mononuclear blood cells (PBMCs) of 12 calves. Subsequently, we isolated PBMCs from another 6 neonatal calves to investigate in vitro the effect of OS on immune responses in terms of activation of lymphocytes, cytokine expression, and antibody production following stimulation with phorbol 12-myristate 13-acetate or bovine herpesvirus-1. The results were compared statistically through mixed models. Calves exposed to high OS status in their first month of age showed higher concentrations of IL-4 and expression of IL4 and IL10 and lower concentrations of IFN-γ and expression of IFNG and IL2 than calves exposed to lower OS. In vitro, OS reduced lymphocyte activation, production of antibodies, and protein and gene expression of key cytokines. Collectively, our results demonstrate that OS can compromise some immune responses of newborn calves. Hence, further studies are needed to explore the mechanisms of how OS affects the different lymphocyte subsets and the potential of ameliorating OS in newborn calves as a strategy to augment the functional capacity of calf immune cells, as well as enhance calves' resistance to infections.