Associations between preweaning calf feeding behaviors with age at first calving and lactational performance using an automatic calf feeder.

The objective of this retrospective observational study was to determine whether preweaning calf behaviors and milk replacer (MR) intake from an automatic calf feeder were associated with age at first calving and first-lactation performance. Calves were housed in groups with access to an automatic calf feeder for 7 wk with a maximum milk allowance of 1,800 g/d of MR (12 L/d). Outcomes of interest included age at first calving (n = 137), first-lactation mature-equivalent 305-d (ME305) milk yield (n = 132), and first-lactation ME305 energy-corrected milk (ECM) yield (n = 132). Linear models included the fixed effects of the daily means of unrewarded visits, rewarded visits, drinking speed, and MR intake. Furthermore, breed, disease diagnosis, season of birth, and age of the calf when it was first introduced to the automatic calf feeder were included in all models. The genetic parameter for milk yield (predicted transmitting ability for milk) was included in models related to lactational performance. Feeding behaviors and milk replacer intake were not associated with age at first calving. Unrewarded visits to the automatic calf feeder were associated with ME305 milk and ECM yields. As mean daily unrewarded visits increased by 1, first-lactation ME305 milk yield and ME305 ECM yield increased by 319 kg and 224 kg, respectively. No other feeding behavior was significantly associated with first-lactation ME305 milk or ECM yields. In conclusion, unrewarded visits were positively associated with first-lactation performance, but external validation is still needed.

The effects of dexamethasone administration on physiological, behavioral, and production parameters in dairy cows after a difficult calving.

Dairy cows are predisposed to diseases during the postpartum period. Dystocia has been associated with increased risk for disease, which is likely the result of increased tissue trauma and stress during the prolonged parturition. To attenuate the inflammatory response seen in dystocic animals and improve well-being, we assessed the effects of a glucocorticoid, dexamethasone administered within 12 h after calving. Dystocia was defined as a difficult birth resulting in a prolonged calving (≥70 min after the amniotic sac appears) and was monitored through 3 video cameras in the close-up dry-cow pen. Cows meeting the dystocia definition were randomly assigned to receive a single intramuscular injection of either dexamethasone (DEX; 0.1 mg/kg of body weight; n = 43) or saline (CON, n = 44) within 12 h following a dystocic calving. Serum haptoglobin, blood ß-hydroxybutyrate (BHB) concentrations, body temperature, and several behaviors were measured for the first 7 d postpartum. Additionally, milk production and components for the first 120 d were recorded. Using a mixed model, the fixed effects of treatment, parity, calving assistance, and time, along with 2- and 3-way interactions, were analyzed with cow as a random effect. We observed that primiparous DEX cows had greater serum haptoglobin concentrations on d 3 and d 7 postpartum compared with primiparous CON cows. There was no difference between treatment groups for blood BHB concentrations and body temperature. Behavior was altered between treatments, with DEX cows having reduced activity for the first week postpartum, as well as less restlessness and increased lying times on some of the days following calving. Treatment interacted with time for milk yield, such that DEX cows produced 2.7 kg/d less milk than CON cows for the first month following calving. The administration of dexamethasone resulted in changes in behavioral measurements, which could suggest a reduction in discomfort; however, due to the reduction in milk yield for the first month following calving, DEX administration may not be applicable for typical farm use. Additional research is needed to investigate treatments for cows experiencing dystocia without detrimental effects on milk yield.

Practical challenges and potential approaches to predicting low-incidence diseases on farm using individual cow data: A clinical mastitis example.

Clinical mastitis (CM) incidence is considerable in terms of cows affected per year, but cases are much less common in terms of detections per cow per milking. From a modeling perspective, where predictions are made every time any cow is milked, low CM incidence per cow day makes training, evaluating, and applying CM prediction models a challenge. The objective of this study was to build models for predicting CM incidence using time-series sensor data and choose models that maximize net return based on a cost matrix. Data collected from 2 university dairy farms, the University of Florida and Virginia Polytechnic Institute and State University, were used to gather representative data, including 110,156 milkings and 333 CM cases. Variables used in the models were milk yield, protein, lactose, fat, electrical conductivity, days in milk, lactation number, and activity as the number of steps, lying time, lying bouts, and lying bout duration. Models that predicted either likelihood of CM caused by gram-negative (GN) or gram-positive (GP) bacteria on each day were derived using extreme gradient boosting with weighting favoring true-positive cases, logistic responses, and log-loss errors. Model accuracies were determined using data randomly held out from the training set on each run. All variables considered were in terms of change (slope) over previous days, including the day CM was visually detected. The GN models had a median sensitivity (Se) of 52.6% and specificity (Sp) of 99.8%, whereas the GP models had a median Se of 37.5% and Sp of 99.9% when tested on the held-out data. In our models optimized to reduce cost from predictions, the Se was much less than Sp, suggesting that CM models might benefit from greater model weighting placed on Sp. Results also highlight the importance of positive predictive value (true positive cases per predicted positive case) along with Sp and Se, as models built on sparse data tend to predict too many false-positive cases. The calculated partial net return of our GN and GP models were -$0.15 and -$0.10 per cow per lactation, respectively, whereas International Organization for Standardization (ISO) standard models with Se of 80% and Sp of 99% would return -$1.32 per cow per lactation. Models chosen that minimized the cost to the farmer differed markedly from models that met ISO guidelines, showing asymmetry in targets between Sp and Se when the disease incidence rate is low. Because of the unique challenges that low-incidence diseases like CM present, we recommend that future CM predictive models consider the economic and practical implications in addition to the traditional model evaluation metrics.

Identifying gram-negative and gram-positive clinical mastitis using daily milk component and behavioral sensor data.

Opportunities exist for automated animal health monitoring and early detection of diseases such as mastitis with greater on-farm adoption of precision technologies. Our objective was to evaluate time series changes in individual milk component or behavioral variables for all clinical mastitis (CM) cases (ACM), for CM caused by gram-negative (GN) or gram-positive (GP) pathogens, or CM cases in which no pathogen was isolated (NPI). We developed algorithms using a combination of milk and activity parameters for predicting each of these infection types. Milk and activity data were collated for the 14 d preceding a CM event (n = 170) and for controls (n = 166) matched for breed, parity, and days in milk. Explanatory variables in the univariate and multiple regression models were the slope change in milk (milk yield, conductivity, somatic cell count, lactose percentage, protein percentage, and fat percentage) and activity parameters (steps, lying time, lying bout duration, and number of lying bouts) over 7 d. Slopes were estimated using linear regression between d -7 and -5, d -7 and -4, d -7 and -3, d -7 and -2, and d -7 and -1 relative to CM detection for all parameters. Univariate analyses determined significant slope ranges for explanatory variables against the 4 responses: ACM, GN, GP, and NPI. Next, all slope ranges were offered into the multivariate models for the same 4 responses using 3 baselines: d -10, -7, and -3 relative to CM detection. In the univariate analysis, no explanatory variables were significant indicators of ACM, whereas at least 1 parameter was significant for each of GN, GP, and NPI models. Superior sensitivity (Se) and specificity (Sp) estimates were observed for the best GP (Se = 82%, Sp = 87%) and NPI (Se = 80%, Sp = 94%) multiple regression models compared with the best ACM (Se = 73%, Sp = 75%) and GN (Se = 71%, Sp = 74%) models. Sensitivity for the GN model was greater at the baseline closest to the day of CM detection (d -3), whereas the opposite was observed for the GP and NPI model as Se was maximized at the d -10 baseline. Based on this screening of relationships, milk and activity sensor data could be used in CM detection systems.

The effect of J5 bacterins on clinical, behavioral, and antibody response following an Escherichia coli intramammary challenge in dairy cows at peak lactation.

Vaccination against coliform mastitis has become part of mastitis control programs in the past 3 decades, as a means of reducing the severity of clinical mastitis. Our study objective was to evaluate the effect of 2 commercially available vaccines on clinical, behavioral, and antibody response following Escherichia coli intramammary challenge in cows near peak lactation. Cows (n = 12 per group) were vaccinated with vaccine 1 (V1) or vaccine 2 (V2) at dry-off, 21 d pre-calving, and 14 d post-calving. Twelve cows served as unvaccinated controls (CTL). Cows were challenged with E. coli in a rear quarter at approximately 100 d in milk. Milk samples were collected pre- and post-challenge to enumerate E. coli and determine somatic cell count. Serum was collected before each vaccination and at d 0, 1, 2, 3, 6, 30, and 60 relative to challenge, to study antibody response. Milk IgA and tumor necrosis factor-α concentrations were determined in whey. Vaginal temperature, cow activity, and milk yield and components were monitored post-challenge. Bacterial count, somatic cell score, milk yield and component decline, vaginal temperature, activity measures, and antibody and cytokine response were analyzed for treatment differences. The effects of parity, breed, and a repeated measure of time were also tested. Seven cows had to be removed from the study post-challenge for antibiotic treatment (CTL and V1, n = 3 each; V2, n = 1), 2 of which were euthanized (both CTL). Vaccinated cows exhibited fever (vaginal temperature ≥39.4°C) 3 h earlier than CTL cows, but we found no differences between treatments for bacterial count, somatic cell score, or milk yield reduction. Vaccinated cows spent more time lying per rest bout 2 d post-challenge, but total daily lying time was not different from CTL cows during the 7 d post-challenge. The vaccines differed in antibody response: V1 cows had greater serum IgG1 and IgG2 post-challenge. A parity effect was also evident: primiparous cows had lower bacterial counts, somatic cell score and a smaller milk yield decline than multiparous cows, but also had lower antibody production. Immunization with either J5 bacterin did not reduce clinical signs of mastitis in cows challenged at 100 d in milk, demonstrating that the effects of J5 vaccination had diminished at peak lactation.

Comparing dairy farm milk yield and components, somatic cell score, and reproductive performance among United States regions using summer to winter ratios.

Heat stress abatement is a challenge for dairy producers in the United States, especially in the southern states. Thus, managing heat stress is critical to maintain dairy cow performance in the summer. The ability to employ a metric to measure heat stress and evaluate abatement strategies may benefit dairy producers by providing meaningful feedback on the effectiveness of current and future management strategies with the goal of improving heat stress management. Therefore, this study aimed to explore the use of the summer to winter performance ratio metric to quantify and compare farm performance variables among regions of the United States. Monthly performance data recorded by the Dairy Herd Improvement Association from 2007 to 2016, for all US Dairy Herd Improvement Association herds processing records through Dairy Records Management Systems (Raleigh, NC), were obtained. Season dates were based on the astronomical definition of the Northern Hemisphere with summer as June 21 to September 21 and winter as December 21 to March 19. States were grouped into regions based on climate zone classification. Performance records included a total of 16,573 herds [Northeast (n = 7,955), Midwest (n = 6,555), Northern Plains (n = 305), Southeast (n = 1,370), and Southern Plains (n = 388) regions]. Herd test day performance variables energy-corrected milk, somatic cell score, milk fat and protein percentage, conception rate, heat detection rate, and pregnancy rate in summer and winter were used to calculate summer to winter ratios for each region. The MIXED procedure of SAS 9.4 (SAS Institute Inc., Cary, NC) was used to compare test day performance variables. The effects of year, mean days in milk, mean 150-d milk, mean herd size, and number of milkings per day were included as covariates in the models. Dairy cattle performance in all climate regions was negatively affected by summer heat stress, but some regions greater than others. A difference was also observed among regions when comparing summer to winter ratios for each performance parameter. This indicates that summer performance varies by climate region identified by the summer to winter ratio and demonstrates usefulness of the metric to monitor degree of heat stress based on performance.

Meloxicam administration either prior to or after parturition: Effects on behavior, health, and production in dairy cows.

Parturition is often a stressful period, when the incidence of disease is high after calving, which has been associated with an uncontrolled inflammatory response. Therefore, the objective of this study was to test the effect of the administration of a nonsteroidal anti-inflammatory drug (meloxicam) on the behavior, health, and production of peripartum cows. Meloxicam was dosed at 1 mg/kg of body weight, and an empty gel capsule served as a placebo. Both were administered orally with a balling gun. Dairy cows and heifers were randomly assigned to 1 of 3 treatment groups: (1) meloxicam administration before calving, with a placebo administered after calving (MEL-PRE, n = 60), (2) placebo administered before calving, and meloxicam administered after calving (MEL-POST, n = 69), and (3) a placebo administered before calving and after calving (CTL, n = 65). To identify imminent calving events, a vaginal thermometer was inserted approximately 2 wk before the expected calving date and a drop in temperature was used to identify cows close to calving. Calving events were monitored via video cameras, and the amount of time that elapsed between the appearance of the amniotic sac at the vulva until delivery of the calf was used to determine calving difficulty score. Eutocic calving events were defined as cows that calved in ≤70 min, and dystocia was defined as cows that took longer than 70 min to calve. Milk yield and components were measured for the first 15 wk of lactation and accelerometers were used to record activity and lying behaviors. The effects of treatment, breed, parity, calving difficulty, and, when applicable, a repeated measure, along with interaction terms, were analyzed in mixed models. Regardless of the time of administration, dystocic cattle that received meloxicam were less active than dystocic CTL. Dystocic animals displayed more lying bouts on the day of calving and then displayed fewer lying bouts and were less active during the days following calving. No effect of treatment was noted on any health outcomes. Eutocic MEL-PRE animals produced 6.8 kg/d more milk than eutocic CTL. Regardless of calving difficulty, MEL-PRE animals produced more milk fat, protein, and lactose (kg/d) than CTL. In conclusion, meloxicam administration before calving appears promising in increasing milk yield in eutocic cows.

Short communication: Automated detection of behavioral changes from respiratory disease in pre-weaned calves.

Group housing of calves can pose a challenge in identifying respiratory disease; therefore, it is necessary to develop tools that can identify these disease events. In this experiment, pre-weaned calves (n = 30) were housed in groups with an automatic calf feeder and were fitted with an accelerometer. Step activity, lying behaviors, and feeding behaviors were recorded to determine the effect of respiratory disease. All calves were health scored twice daily, and calves with respiratory scores ≥5 were diagnosed with respiratory disease (n = 10). Each diseased calf was match paired with a healthy control based on the date of disease diagnosis, breed, and age. Control calves were determined to be healthy if they had respiratory scores ≤4, as well as fecal, navel, and joint scores of 0 or 1. Diseased calves were less active before, on the day of, and after respiratory disease diagnosis. Furthermore, diseased calves had reduced lying frequencies starting 2 d before diagnosis, as well as after diagnosis. Last, diseased calves consumed less milk on the day of diagnosis when compared with healthy controls. Step activity, lying bouts, and milk intake may prove to be a useful tool in identifying respiratory disease under practical farming, but this requires further research.

Technical note: The use of an accelerometer for measuring step activity and lying behaviors in dairy calves.

Calf behaviors such as step activity, lying bouts, and lying time may be an indicator of calf health and welfare. To reduce time-consuming visual observations, the use of behavioral monitoring systems have been developed to capture these data. Previous studies have validated lying behaviors using an accelerometer (HPG; HOBO Pendant G data logger, Onset Computer Corp., Bourne, MA) in calves. However, the HPG does not measure step activity. The objectives of this study were to (1) validate step activity, lying bouts, and lying time of AfiTag II (AT2; AfiTag II, Afimilk Ltd., Kibbutz Afikim, Israel) to observations from video, and (2) to compare the behavioral data from AT2 to the HPG. Calves (n=5) were group housed with an automatic calf feeder. Video cameras were installed at both sides of the pen, and observations were analyzed for 7h/calf. The AT2 and the HPG were both attached to the lateral side of the right rear leg of 5 calves, and data were recorded for 10 d. The full 10-d data set was used to examine correlations for lying bouts and lying time between AT2 and the HPG. The HPG was set at a 60-s sampling interval and the output was analyzed both unfiltered as well as utilizing a 1-min event filter to remove potentially erroneous readings. The AT2 recorded step activity, lying bouts, and lying time, and summarized these behaviors in 15-min periods. The AT2 recorded lying time in 3-min intervals, which were then automatically summarized in 15-min periods. The correlations of step activity, lying bouts, and lying time between video recordings and AT2 were 0.99. For the second objective, correlations between AT2 and the HPG were 0.99 for lying time and 0.93 for lying bouts. The 1-min event filter resulted in a 0.03 improvement in correlations for lying bouts between the HPG and AT2. The high correlation between video recordings and AT2 suggest that this device can be used to measure step activity, lying time, and lying bouts in unweaned dairy calves housed in groups.

Effect of feeding whole compared with cell-free colostrum on calf immune status: Vaccination response.

Vaccination contributes to improved herd health and production. Boosting immune development at a young age may have long-term effects by enhancing vaccine immune response and efficacy. In the bovine, colostrum is the sole source of maternal immunity, having a substantial effect on health status in the neonate. To date, colostral antibody concentration is used to evaluate colostrum quality. However, colostrum also contains proteins and cells, which may affect immune development and future responses to vaccines. To determine the effect of maternal colostral cells on immune development, 37 female Holstein and Jersey dairy calves were bottle-fed 4 quarts total of whole colostrum (WC) or cell-free colostrum (CFC) at birth. Calves were vaccinated with 2 series of multivalent vaccines. Series A consisted of vaccines given between 1 and 4mo of life. Series B consisted of vaccines given between 5 and 10mo of life. Calf peripheral blood samples were obtained before each vaccination series and monthly for 3mo after each vaccination series. Cellular blood parameters were determined by flow cytometry. Quantitative real-time PCR was used to determine cytokine gene expression in peripheral blood mononuclear cells before vaccination series B and once a month for 2mo after vaccination series B. Calves fed CFC had fewer numbers of B cells in mo 2 after vaccination series A when compared with WC-fed calves. Calves fed CFC had decreased gene expression levels of IL-2 in mo 1 and numbers of CD4(+)CD62L(+)CD45RO(-) and CD4(+)CD62L(+)CD45RO(+) T cells in mo 0 and 1 after vaccination series B as compared with WC-fed calves. Our findings indicate a greater response to vaccines up to 6 to 10mo post-WC feeding when compared with CFC. These data suggest that adoptive transfer of maternal colostral cells at birth has a long-term effect on development of the neonatal immune system.

Effect of feeding whole compared with cell-free colostrum on calf immune status: The neonatal period.

Mortality and decreased weight gain resulting from infection and disease in dairy calves are problems within the dairy industry. The bovine neonate relies solely on colostrum to acquire antibodies through passive transfer. To date, colostrum quality is determined by the concentration of antibodies. However, proteins and cells in the colostrum might also enhance immune development in the neonate. To determine the effect of maternal colostral immune cells on calf health and immune status, maternal colostrum was fed either fresh or after lysis of cells by flash-freezing in liquid nitrogen. Thirty-seven female Holstein and Jersey dairy calves were fed 4 quarts total of whole colostrum (WC) or cell-free colostrum (CFC) at birth. Respiratory and fecal scores were measured from birth to d 45 of life. Calf peripheral blood samples were obtained before and after feeding colostrum as well as on d 1, 3, 7, 14, 21, and 28 of life. Peripheral blood mononuclear cells were collected and analyzed for cellular parameters by flow cytometry. Total respiratory scores were greater in CFC-fed calves compared with WC-fed calves on d 38 of life. There were fewer CD4+ T cells and CD4+CD62L+CD45RO- T cells on d 1 and fewer CD4+CD62L+CD45RO+ T cells on d 1 and 3 in CFC-fed calves compared with WC-fed calves. Compared with WC-fed calves, CFC-fed calves had a greater percentage of CD4+CD62L-CD45RO+ T cells on d 0.25, 1, 3, and 7, and a greater percentage of monocytes on d 7. Our data suggest that colostral cells adoptively transfer and enhance neonatal immunity during the first month of life.

Short communication: comparison of virulence factors in Klebsiella pneumoniae strains associated with multiple or single cases of mastitis.

Klebsiella pneumoniae mastitis in dairy cattle is generally due to an opportunistic infection from the environment, resulting in large heterogeneity among mastitis-causing strains within a herd. However, in mastitis outbreaks in 4 herds, several strains of K. pneumoniae were identified as the cause of infection in multiple cows, suggesting increased ability to either cause disease or evade host defenses. In this study, differences in capsule formation and immune evasion were compared in 5 pairs of K. pneumoniae strains, where one strain in each pair was associated with multiple cases of mastitis and the other with a single case of mastitis. Production of capsular polysaccharide, ability to evade killing by polymorphonuclear neutrophilic leukocytes (PMNL), and the relationship between the 2 were evaluated for each strain grown in broth or milk. Growth of isolates in skim milk increased capsule size and ability to evade killing by PMNL, depending on strain type. Specifically, strains associated with multiple cases of mastitis had increased capsule size in skim milk. Strains associated with single cases of mastitis were better able to evade killing by PMNL when grown in skim milk. Our results, although preliminary, suggest that the 2 groups of strains may constitute different subpopulations of K. pneumoniae. However, our findings do not indicate that capsule or evasions of killing by PMNL explain increased mastitis outbreaks with Klebsiella. Further work will explain the enhanced ability of some strains to cause mastitis in dairy cows.

The effect of meloxicam on pain sensitivity, rumination time, and clinical signs in dairy cows with endotoxin-induced clinical mastitis.

The objectives of this study were to (1) evaluate the use of a pressure algometer and an automated rumination monitoring system to assess changes in pain sensitivity and rumination time in response to endotoxin-induced clinical mastitis and (2) evaluate the effect of the nonsteroidal antiinflammatory drug meloxicam on pain sensitivity and rumination time, as well as other clinical signs, in dairy cattle with endotoxin-induced clinical mastitis. Clinical mastitis was induced in 12 primiparous and 12 multiparous lactating dairy cows by intramammary infusion of 25 µg of Escherichia coli lipopolysaccharide (LPS) into 1 uninfected quarter. Immediately after, half the cows were injected subcutaneously with meloxicam (treated group) and half with the same volume of a placebo solution (control group). Pain sensitivity was assessed by measuring the difference in pressure required to elicit a response on the control and challenged quarter using an algometer 3 d before, immediately before, and at 3, 6, 12, and 24h after LPS infusion and either meloxicam or placebo injection. Rumination was continuously monitored from 2 d before to 3 d after LPS infusion using rumination loggers. Udder edema, body temperature, somatic cell score, and dry matter intake were also monitored to evaluate the occurrence and the duration of the inflammation after LPS infusion. In control animals, the difference in the pressure applied to the control and challenged quarters (control - challenged quarter) increased by 1.1 ± 0.4 kg of force 6h after LPS infusion compared with the baseline, suggesting an increase in pain sensitivity in the challenged quarter. Neither the LPS infusion nor the meloxicam treatment had an effect on daily rumination time. However, the rumination diurnal pattern on the day of LPS infusion showed an overall deviation from the baseline pattern. Cows spent less time ruminating in the hours following LPS infusion and more time ruminating later in the day. Meloxicam did not alter somatic cell score or dry matter intake. However, meloxicam-treated animals had less udder edema and a lower body temperature in the hours following LPS infusion compared with control animals. In conclusion, pressure algometers and rumination loggers show promise as tools to detect mastitis and monitor recovery on farm. Further, meloxicam has a beneficial effect in relieving pain and decreasing udder edema and body temperature in LPS-induced clinical mastitis.

The effects of experimentally induced Escherichia coli mastitis and flunixin meglumine administration on activity measures, feed intake, and milk parameters.

The use of flunixin meglumine (FM), a nonsteroidal antiinflammatory drug, during experimentally induced Escherichia coli mastitis was evaluated. Twenty-four primiparous and multiparous lactating dairy cows were challenged with 1×10(2) cfu of E. coli 727 in 1 uninfected quarter. Of the 24 E. coli-challenged animals, 12 were administered FM [ECF; 100mg (2 cc)/45.5 kg of body weight) at the onset of clinical mastitis signs. The remaining 12 challenged cows were untreated (EC). An additional 11 cows were infused with 1 mL of sterile phosphate-buffered saline and served as the nonchallenged control (CTL) group. Activity measures, dry matter intake (DMI), milk production, milk bacterial counts from challenged mammary glands, and somatic cell score (SCS) were collected on all animals. Activity measurements were collected using both a behavior-monitoring system and data loggers. Activity was summarized by day (behavior-monitoring system) and in 3-h time periods (data loggers). An examination of animal activity indicated that EC and ECF cows stood more and lay less as compared with the CTL animals in the first 6h after FM administration. When DMI was analyzed, CTL and ECF animals had greater DMI than the EC animals on d 1 postchallenge. However, by d 2 postchallenge, DMI for ECF and EC cows was significantly less than for the CTL cows. The ECF cows had greater milk yield than did EC animals by d 3 and 4 postchallenge, and no significant difference in yield was observed between the ECF and CTL animals. No differences in SCS were observed between the parity groups. Yet, bacterial counts in milk were greater in multiparous animals compared with the primiparous cows. Therefore, it can be concluded that E. coli mastitis does alter animal activity and may have a negative effect on animal well-being. However, the improvement in DMI and milk production for ECF animals provides evidence for using a nonsteroidal antiinflammatory drug as supportive therapy in alleviating the adverse effects associated with E. coli mastitis.

The ability of common mastitis-causing pathogens to survive an ensiling period.

A forage-based study was conducted to examine the ability of enterococci, streptococci, and gram-negative bacteria to survive a 3-wk ensiling process. Harvested grass and corn forages were each divided into 3 treatment groups consisting of 2 commercially available silage inoculants and 1 negative control group. Within 24h of harvest, a uniform amount of forage was added to each of 18 vacuum-sealable freezer bags. Inoculants 1 and 2 were applied to each of 6 bags and the remaining 6 bags were not inoculated (negative control). All bags were sealed using an industry-grade vacuum sealer to create a pillow pack. At wk 1, 2, and 3 of the ensiling process, 6 bags were opened, 2 from each of the 3 groups. Dry matter (DM), pH, and bacterial enumeration were determined on the forage before ensiling, as well as at wk 1, 2, and 3 of ensiling. The pH of grass and corn samples decreased to 5.2 and 4.1, respectively, by the end of the ensiling period. Inoculant 2 (7.3 log(10) cfu/g of DM) resulted in a greater enterococcal count in grass samples than did inoculant 1 (4.2 log(10) cfu/g of DM) at 3 wk of ensiling and both were greater than the negative control (1.2 log(10) cfu/g of DM). Counts of streptococci in grass samples at wk 3 were greater in inoculated samples (inoculant 1, 7.6 log(10) cfu/g of DM; inoculant 2, 7.0 log(10) cfu/g of DM) compared with the negative control (4.3 log(10) cfu/g of DM). Treatment differences were observed following 1 wk of ensiling in corn samples. Enterococcal counts on corn samples following the 3-wk ensiling were not significantly different between inoculant 1 (4.3 log(10) cfu/g of DM) and inoculant 2 (4.4 log(10) cfu/g of DM). However, counts in both inoculated groups were greater than in the negative control group (4.0 log(10) cfu/g of DM). No significant treatment differences were observed for streptococci counts at wk 3. Counts for gram-negative bacteria were not detectable by wk 3 of ensiling in either grass or corn samples. The addition of a silage inoculant led to greater counts of enterococci and streptococci in grass silage compared with the negative control at the end of a 3-wk ensiling period. The application of a silage inoculant led to increased enterococci counts, but not streptococci counts, in corn samples following the ensiling period. These data indicate that enterococci and streptococci are able to survive the pH decrease observed during ensiling.

Evaluation of confirmatory stains used for direct microscopic somatic cell counting of sheep milk.

Current FDA regulatory screening and confirmatory methods, electronic cell counting and the direct microscopic somatic cell count (DMSCC), differ for the detection of abnormal milk in sheep and goats. The DNA-specific electronic SCC screening methods such as Fossomatic (Foss, Hillerød, Denmark) can be used for both sheep and goat milk; however, the nonspecific methylene blue-based stains used for DMSCC in sheep cannot be used for goats as they nonspecifically stain cytoplasmic particles naturally present in goat milk. The DNA-specific stain pyronin Y-methyl green (PMG) is currently used for DMSCC in goats. Sheep also shed cytoplasmic particles during the milk secretory process, but in fewer numbers than goats. The objective of this study was to determine whether the nonspecific, methylene blue-based Levowitz-Weber (L-W) stain is the appropriate regulatory stain to use for DMSCC in sheep milk. Composite milk samples from 42 commercial dairy ewes were collected every 4 wk for the duration of each ewe's lactation for a total of 10 sample days. Milk samples were subjected to 3 methods of SCC determination: automated Fossomatic counting, DMSCC with L-W stain, and DMSCC with PMG stain conducted according to FDA regulatory procedures (2400 series forms). The DMSCC from milk smears stained with L-W were greater than those from smears stained with PMG and those from the Fossomatic analysis on 6 of the 10 sampling days. Milk smears stained with PMG did not differ from Fossomatic analysis at any sampling. The average milk SCC for L-W, PMG, and Fossomatic were (mean±SE) 275±36×10(3), 174±24×10(3), and 164±24×10(3) cells/mL, respectively. The DMSCC for milk stained with L-W was 58% greater than that with PMG and 68% greater than that obtained with the Fossomatic analysis. In conclusion, DMSCC of sheep milk stained with the nonspecific, methylene blue L-W stain resulted in a marked increase in SCC over that of the DNA-specific stain PMG and Fossomatic SCC analysis. The findings of this study support the continued use of Fossomatic SCC but recommend the replacement of the methylene blue-based stains with DNA-specific PMG for determination of DMSCC in sheep milk.

The influence of vitamin E on immune function and response to vaccination in older horses.

Horses have an increased susceptibility to infection because of a decline in immune function with advancing age. Vitamin E has been found to play a key role in normal immune system function. The purpose of the study was to examine the effect of vitamin E supplementation on immune function and response to vaccination in older horses. Predominantly older horses (18.9 +/- 1.3 yr, range 7 to 26 yr; 523 +/- 38 kg of BW) were supplemented orally once daily for 16 wk with either all-rac-alpha-tocopheryl acetate (15 IU/kg of BW; n = 8) or a placebo (n = 8). One horse from each group was removed from the study for reasons not related to the study. Serum alpha-tocopherol concentration, neutrophil and monocyte bacterial killing ability, lysozyme activity, immunoglobulin concentration (IgG(a), IgG(b), IgG(T), and IgM), and neutralizing antibody production to West Nile virus vaccination were determined. The overall serum alpha-tocopherol concentration of the vitamin E-supplemented horses was greater than that of placebo-supplemented horses (P < 0.001). Bacterial killing capacity of monocytes and neutrophils increased in the vitamin E-supplemented horses (P < 0.05). Vitamin E-supplemented horses had greater serum IgG(a) (P < 0.001) and IgG(T) (P = 0.003) concentrations but produced less serum IgG(b) (P = 0.023) than placebo-supplemented horses. There was no effect of vitamin E supplementation on IgM production. The neutralizing antibody response to vaccination against West Nile virus was unaffected by vitamin E supplementation. There was a continuous increase in serum lysozyme concentration in placebo-supplemented horses, whereas serum lysozyme concentration did not increase until wk 12 in vitamin E-supplemented horses. In conclusion, vitamin E supplementation of predominantly older horses differentially modulated general cell-mediated and humoral immune function. Further research is needed to fully understand the effect of vitamin E on the immune function of horses.

Experimental challenge of bovine mammary glands with Enterococcus faecium during early and late lactation.

Mammary glands of early and late lactation cows were challenged with Enterococcus faecium of bovine origin to determine in vivo pathogenicity and milk somatic cell count (SCC) responses. A total of 20 early lactation and 18 late lactation mammary glands were challenged. Two isolates highly adaptive and 2 isolates poorly adaptive for in vitro growth in mammary secretion were used as challenge strains of bacteria. Challenged quarters of early lactation cows were more susceptible to intramammary infection caused by E. faecium than those of late lactation cows. Intramammary challenge with isolates poorly adaptive for in vitro growth in mammary secretions resulted in 94.7% of quarters infected compared with 36.8% of the quarters infused with the isolates highly adaptive for in vitro growth in mammary secretions. Milk from quarters infused with the isolates poorly adaptive for in vitro growth had higher SCC and bacterial counts compared with quarters challenged with the isolates highly adaptive for in vitro growth. A stage of lactation effect within treatment groups was measured when milk SCC were compared between early and late lactation cows. Milk SCC in uninfused (negative control) quarters were lower in early lactation cows compared with late lactation cows. Conversely, in quarters infused with isolates poorly adaptive for in vitro growth, SCC were higher in early lactation cows compared with late lactation cows on d 2, 3, 4, 15, 16, and 17 postchallenge. In quarters infused with isolates highly adaptive for in vitro growth, SCC response did not differ between early and late lactation cows. In vitro growth of E. faecium in mammary secretion was inversely related to in vivo pathogenicity in the mammary glands of early and late lactation cows.

Short communication: analysis of immune function in lactating dairy cows fed diets varying in phosphorus content.

The aim of this study was to evaluate the effect of varying dietary P on bovine immune function. Nine first- or second-lactation Holstein cows were fed diets varying in P in a 3 x 3 Latin square design. Diets were formulated to contain either low (0.34%, no supplementary P), medium (0.43%), or high (0.52%) P. All 3 diets were formulated to meet or exceed current NRC requirements for P content. Between d 21 and 26 of each period, blood samples were collected and serum inorganic P concentration, lymphocyte proliferation, and neutrophil bactericidal activity were measured. Serum P increased with increasing dietary P intake and was greatest in the first lactation compared with subsequent lactations. There was a stage of lactation-dependent increase in lymphocyte proliferation after stimulation with concanavalin A, phytohemagglutinin, or pokeweed mitogen. However, dietary P did not alter lymphocyte proliferation or neutrophil bactericidal activity in vitro. In conclusion, decreasing dietary P to reduce manure P content and the risk of P losses from farms to surface water does not have an adverse effect on the innate or cell-mediated immune responses of lactating dairy cattle.

Genomic typing of enterococci isolated from bovine mammary glands and environmental sources.

Enterococcal isolates (n = 102) from various sources of bovine origin on 1 farm were characterized using pulsed field gel electrophoresis analysis of SmaI restriction patterns. Isolates originated from feed samples (n = 6), bedding samples (n = 15), and bovine quarter-milk samples (n = 81). Isolates collected from milk samples included those from high-somatic cell count cows (n = 42), postpartum milk samples (n = 16), and clinical mastitis samples (n = 23). Species evaluated included Enterococcus faecium (n = 68), Enterococcus casseliflavus (n = 29), and Enterococcus faecalis (n = 5). A total of 20 clusters representing 44 isolates were detected when a similarity cut-off level of 75% was applied to interpret the pulsed field gel electrophoresis results. Fifteen of the clusters contained only isolates from milk samples. Four clusters contained isolates from bedding and milk samples. One cluster contained only isolates from feed samples. Clusters comprised of a single species represented 17 of the 20 total clusters. These results suggest enterococci from bovine origin were genetically diverse, whereas a limited number of isolates from various sources appeared to cluster together.