A simulation of strategies to lower bulk tank somatic cell count below 500,000 per milliliter

In the future, the Pasteurized Milk Ordinance may make milk quality standards more stringent by lowering the somatic cell count (SCC) limit on Grade A raw milk to 500,000/ml. Therefore, using a discrete event simulation model, we investigated the effects of the prevention of intramammary infection (as recommended by the National Mastitis Council), lactation therapy, and dry cow therapy (all seven possible combinations) on bulk tank SCC; milk, fat, and protein yields; prevalence of intramammary infection; and culling for mastitis. Untreated controls were also tested. Ten replicates of each intervention and each control were run for 2 simulated yr, including the daily sampling of 100 cows. The goal was to lower bulk tank SCC < 500,000/ml in the 2nd yr for herds that previously had stable bulk tank SCC between 500,000 and 750,000/ml. Although all strategies occasionally met this goal, on no occasion did all replicates perform without a violation in the 2nd yr of the study (median last month of violation ranged from mo 12 to 23). The combination of the prevention of intramammary infection, lactation therapy, and dry cow therapy resulted in the lowest bulk tank linear score, most replicated without a violation in the 2nd yr, fewest months with a bulk tank linear score > or = 5.3, and fewest mastitis culls. The combination of the prevention of intramammary infection and dry cow therapy also was favorably ranked (highest milk yield, fewest clinical intramammary infections during lactation, and highest percentage of uninfected cows).     

Association between milk somatic cell counts up to 400,000 cells/ml and clinical mastitis in French Holstein cows

The relationship between somatic cell counts (SCCs) up to 400,000 cells/ml in individual cows and clinical mastitis was studied by collecting monthly records for a year from 101 Holstein herds in the west of France. Monthly records obtained after any case of clinical mastitis occurring within the lactation were excluded. The resulting dataset consisted of 29,700 records from 4677 cows. The data were analysed by the logistic regression method. Herd, lactation number, calendar month, milk production, stage of lactation on the day of test, and SCC on previous test days were assumed to affect the likelihood of clinical mastitis. There was no significant relationship between SCC and the subsequent occurrence of clinical mastitis for an SCC up to 100,000 cells/ml, but the risk of clinical mastitis increased as the SCC increased up to 400,000 cells/ml. These results suggest that in individual cows, a low SCC recorded after five days in milk does not lead to an increased risk of clinical mastitis.     

Comparison of two regimens for the treatment of clinical bovine mastitis caused by bacteria sensitive to penicillin

The efficacies of two regimens for the treatment of acute clinical mastitis were compared in a randomised multi-centre field trial in Norway, using 657 cows. The purpose was to determine whether repeated intramuscular injections of penicillin G for three days were more effective than a single injection, when given in combination with intramammary treatment for five days. The results were evaluated on the basis of clinical and microbiological examinations and cell count determinations of quarter milk samples taken at the initial visit and four weeks later. There were no significant differences between the effects of the treatments, either for all the cows, or for subgroups of the cows based on age, stage of lactation, and systemic reaction, or the type of causal bacteria.     

Influence of parity and stage of lactation on the somatic cell count in bacteriologically negative dairy cows

This study examines the influence of parity, stage of lactation, and single isolations (i.e., the isolation of a microorganism that could not be reisolated in the same quarter in the next sampling) of staphylococci other than Staphylococcus aureus (coagulase-negative staphylococci), Corynebacterium bovis, or esculin-positive cocci other than Streptococcus uberis (referred to as esculin-positive cocci throughout) on the monthly log(e)-transformed somatic cell count (SCC) for 180 first, second, and third parity cows that were observed over a whole lactation. Repeated measures ANOVA was used to analyze the data. No significant effect was found for the infection variable. However, the results indicated that even single isolations of coagulase-negative staphylocci, C. bovis, or esculin-positive cocci resulted in a numerical or statistically significant increase in SCC. Least squares mean SCC (log(e)-transformed) for bacterio-logically negative cows and cows with single isolations of coagulase-negative staphylococci, C. bovis, or esculin-positive cocci were 3.90, 3.97, 4.08, and 4.17, respectively. Significant effects of parity, stage of lactation, and the interaction of parity and stage of lactation could not be found when only bacteriologically negative cows were considered. Least squares mean SCC for first, second, and third parity cows were 3.80, 3.93, and 3.97, respectively. However, the effects of parity, stage of lactation, and the interaction of parity and stage of lactation were significant when all 180 cows were included. Therefore, these effects must be due to factors that were present in the infected groups.     

Association of abnormal uterine discharge with new intramammary infection in the early postpartum period in multiparous dairy cows

The association of abnormal uterine discharge with the development of intramammary infection (IMI) was studied in 62 multiparous Holstein cows during the nonlactating period and from lactation days 3 through 30. Duplicate milk samples were obtained from each mammary gland at approximately day 30 of the nonlactating period. Milk samples for bacteriologic culture also were obtained from each gland from all cows at the end of the previous lactation, at parturition, and on a minimum of 7 additional dates during the first 30 days of lactation. Beginning after parturition and continuing once weekly for 4 weeks, each cow was examined, using a vaginal speculum to visually estimate the quantity of abnormal uterine discharge in the vagina. Additionally, uterine swab specimens were obtained for aerobic bacteriologic culture. Cows were allotted to groups on the basis of the maximal amount of abnormal uterine discharge observed at any 1 of the 4 examinations. Cows in group 1 had normal discharge or < 30 ml of abnormal discharge; in group 2, > or = to 30 ml of abnormal discharge, observed only on examination by vaginal speculum; and in group 3, > or = to 30 ml of abnormal discharge visible externally. A difference was not detected in the development of new IMI in the nonlactating period between cows that subsequently developed uterine discharge and those that did not. Although significant differences were not found, a tendency for lactating cows with abnormal uterine discharge to be at increased risk for developing new IMI was observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bovine mastitis pathogens in New York and Pennsylvania: prevalence and effects on somatic cell count and milk production

Milk samples were collected from 108,312 dairy cows during 1601 farm visits made between January 1991 and June 1995. The herd visits were made by personnel from the Central Laboratory of the Quality Milk Promotion Services at Cornell University (Ithaca, NY) to farms located in central New York and northern Pennsylvania. Dairy Herd Improvement Association records were available for 32,978 cows in 327 herds. Intramammary infections, as defined by positive milk cultures, were present in 48.5% of all cows and in 36.3% of cows in herds enrolled in the Dairy Herd Improvement Association. Over 75% of the intramammary infections were caused by Streptococcus agalactiae, Streptococcus spp. other than Strep. agalactiae, Staphylococcus aureus, and coagulase-negative staphylococci. Mean days in milk at the time of diagnosis, linear score of the somatic cell count, cost of milk loss per lactation, and milk production effects were calculated for 24 etiologic agents of bovine mastitis.     

Management practices associated with low, medium, and high somatic cell counts in bulk milk

Management practices associated with bulk milk somatic cell counts (SCC) were studied for 201 dairy herds grouped into three categories according to bulk milk SCC. The cumulative production of fat-corrected milk over 305 d of lactation and category for bulk milk SCC were highly correlated; herds within the low category had the highest milk production. Differences in bulk milk SCC among the categories were well explained by the management practices studied. This correlation was not only true for the difference between the high (250,000 to 400,000) and low (< or = 150,000) categories for bulk milk SCC but also for the difference between the medium (150,000 to 250,000) and low categories and the high and medium categories. Management practices that are known to be important for herds in the high category for bulk milk SCC, such as dry cow treatment, milking technique, postmilking teat disinfection, and antibiotic treatment of clinical mastitis, were also found to be important in the explanation of the difference between herds in the medium and low categories for bulk milk SCC. More attention was paid to hygiene for herds in the low category than for herds in the medium or high category. Supplementation of the diet with minerals occurred more frequently for cows in the low category for bulk milk SCC than for cows in the medium and high categories.     

Coping with intractable symptoms in collagen diseases--Behcet''s disease

OBJECTIVE: To determine associations between subclinical Mycobacterium paratuberculosis infection and milk production, milk components, and somatic cell counts of dairy cattle. DESIGN: Cross-sectional epidemiologic survey. ANIMALS: 23 dairy herds in Wisconsin containing 1,653 adult cows were studied. The herds had above average milk production and a history of bovine paratuberculosis in the herd within the previous 12 months. PROCEDURE: All adult cows in the herds were tested for paratuberculosis by use of an absorbed ELISA. Milk yield, fat, protein, and somatic cell count data were retrieved electronically from Dairy Herd Improvement Association records. RESULTS: 147 ELISA-positive and 1,506 ELISA-negative cows were identified. ELISA-positive cows had a mature-equivalent milk production of 376 kg (829 lb)/lactation less than that for ELISA-negative herdmates. Significant difference was not found in lactation average percent-ages of fat and protein, or somatic cell count linear score. When comparing ELISA-positive and -negative cow's current mature equivalent milk with all previous lactations, significant difference was found only from the immediate-preceding lactation. When this difference was examined by parity group, significant difference was confined to cows in the second lactation. CLINICAL IMPLICATIONS: Subclinical paratuberculosis infections, as determined by ELISA, are associated with a 4% reduction in milk yield and add to the already substantial costs of clinical M paratuberculosis infection in the dairy industry.     

Diagnosis of paratuberculosis in dairy cattle, using enzyme-linked immunosorbent assay for detection of antibodies against Mycobacterium paratuberculosis in milk

An ELISA containing lipoarabinomannan (LAM) antigen was used to detect antibodies in milk and serum for diagnosis of Mycobacterium paratuberculosis infection in dairy cattle. In experiment 1, milk and serum samples were obtained from 25 cows, and subjected to LAM ELISA testing immediately, and after 1 year of storage at -70 C. Milk samples, with and without a commonly used chemical preservative, were tested. There was no significant difference in LAM ELISA results between fresh and frozen samples or between preserved and unpreserved milk samples. In experiment 2, milk samples were collected daily from 30 cows over a 14-day period. The day-to-day coefficient of variation was 0.19 for milk LAM ELISA and was 0.15 for serum LAM ELISA, with no statistically significant time effect detected. In experiment 3, single milk, serum, and fecal samples were obtained from 764 cows. The fecal samples were cultured for M paratuberculosis to identify infected cows, and the serum and milk samples were subjected to LAM ELISA testing. Results were compared, using the area under the receiver operating characteristic curves. The milk LAM ELISA had specificity (+/- 95% confidence limits) of 87 +/- 8.1% when the cutoff was set at 50% sensitivity, and specificity of 83 +/- 9.1% when sensitivity was set at 60%. The area under the receiver operating characteristic curve was 0.85 +/- 0.03 for the milk ELISA and 0.75 +/- 0.02 for the serum ELISA. In this population of cattle, the milk LAM ELISA had comparable accuracy to serum LAM ELISA, although the milk LAM ELISA was slightly less reproducible (higher coefficient of variation).     

Neuropeptide Y2 receptors on nerve endings from the rat neurohypophysis regulate vasopressin and oxytocin release

Cows from eight commercial dairies were randomly assigned to intrammamary infusions of cephapirin or cephapirin plus interleukin-2 at the end of lactation. During the first phase of the trial, interleukin-2 was administered to 159 cows at a dose of 1 mg per gland by intracisternal infusion immediately after 300 mg of cephapirin were administered. One hundred sixty-one cows received infusions of a placebo (phosphate-buffered saline; PBS) immediately after cephapirin. In the second phase of the trial, 70 cows received 2 mg of interleukin-2 per gland, and 78 cows received the placebo. Cows were observed daily by the participating farmer for 72 h after infusion and also during routine feeding and care during the dry period and at calving. Potential side effects from udder infusions, particularly gross abnormalities of the udder and signs of systemic side effects were monitored. During the first phase, cure rates for intramammary infections caused by Staphylococcus aureus that were present at the end of lactation were 33.3% for quarters treated with cephapirin and 53.6% for quarters treated with cephapirin and interleukin-2. Cure rates did not differ between treatment groups for all other pathogens or during the second phase of the trial. The incidence of new intramammary infections during the dry period was not affected by intramammary infusion of interleukin-2. Eighteen of 229 (7.9%) cows treated with interleukin-2 aborted within 49 d of treatment compared with 4 of 239 (1.7%) cows treated with PBS. Eleven of the 18 (61.1%) abortions by cows treated with interleukin-2 occurred 3 to 7 d after infusion; none of the abortions by cows treated with PBS occurred until wk 7 after infusion.     

Effect of diseases on the culling of Holstein dairy cows in New York State

The effect of seven diseases on culling was measured in 7523 Holstein cows in New York State. The cows were from 14 herds and had calved between January 1, 1994 and December 31, 1994; all cows were followed until September 30, 1995. Survival analysis was performed using the Cox proportional hazards model to incorporate time-dependent covariates for diseases. Different intervals representing stages of lactation were considered for effects of the diseases. Five models were fitted to test how milk yield and conception status modified the effect of diseases on culling. Covariates in the models included parity, calving season, and time-dependent covariates measuring diseases, milk yield of the current lactation, and conception status. Data were stratified by herd. The seven diseases and lactational risks under consideration were milk fever (0.9%), retained placenta (9.5%), displaced abomasum (5.3%), ketosis (5.0%), metritis (4.2%), ovarian cysts (10.6%), and mastitis (14.5%). Older cows were at a much higher risk of being culled. Calving season had no effect on culling. Higher milk yield was protective against culling. Once a cow had conceived again, her risk of culling dropped sharply. In all models, mastitis was an important risk factor throughout lactation. Milk fever, retained placenta, displaced abomasum, ketosis, and ovarian cysts also significantly affected culling at different stages of lactation. Metritis had no effect on culling. The magnitude of the effects of the diseases decreased, but remained important, when milk yield and conception status were included as covariates. These results indicated that diseases have an important impact on the actual decision to cull and the timing of culling. Parity, milk yield, and conception status are also important factors in culling decisions.     

Dietary vitamin E and selenium affect mastitis and milk quality

Vitamin E and selenium (SE) are essential nutrients that are integral components of the antioxidant defense of tissues and cells. Soils in many of the important dairy regions of the world are Se-deficient, and feedstuffs grown on these soils will not provide adequate dietary Se. Cattle consuming stored forages are likely to be low in vitamin E unless supplemented, and vitamin E deficiencies are frequently observed in peripartum dairy cows. Many new intramammary infections (IMI) occur in the 2 wk before and after calving. Deficiencies of either vitamin E or Se have been associated with increased incidence and severity of IMI, increased clinical mastitis cases, and higher somatic cell counts (SCC) in individual cows and bulk tank milk. Somatic cell counts are a primary indicator of mastitis and milk quality in dairy herds. The polymorphonuclear neutrophil (PMN) is a major defensive mechanism against infection in the bovine mammary gland. A know consequence of vitamin E and Se deficiency is impaired PMN activity and postpartum vitamin E deficiencies are frequently observed in dairy cows. Dietary supplementation of cows with Se and vitamin E results in a more rapid PMN influx into milk following intramammary bacterial challenge and increased intracellular kill of ingested bacteria by PMN. Subcutaneous injections of vitamin E approximately 10 and 5 d before calving successfully elevated PMN alpha-tocopherol concentrations during the periparturient period and negated the suppressed intracellular kill of bacteria by PMN that commonly is observed around calving.     

Effect of Neospora caninum infection on milk production in first-lactation dairy cows

OBJECTIVE: To determine whether cows seropositive to Neospora caninum produced less milk during their first lactation than seronegative cows. DESIGN: Repeated-measures, prospective study. ANIMALS: 372 Holstein cows in their first lactation. PROCEDURE: Cows were tested repeatedly before and during their first lactation for antibodies to N caninum. One-way and repeated-measures ANOVA were used to determine whether mean daily milk weights and milk weights from Dairy Herd Improvement Association testing were less for seropositive cows than for seronegative cows. RESULTS: Weekly mean daily milk weights for the 118 seropositive cows were significantly less than those for the 254 seronegative cows, and milk production for seropositive cows (mean, 55.2 lb/cow/d) was 2.5 lb/cow/d less than that for seronegative cows (mean, 57.7 lb/cow/d). Analysis of results from Dairy Herd Improvement Association testing revealed that production of seropositive cows was less for milk (3.1 lb/cow/d), fat-corrected milk (3.6 lb/cow/d), and fat (0.14 lb/cow/d) than production of seronegative cows. CLINICAL IMPLICATIONS: The economic impact of N caninum infection in dairy cows can include reduced revenues from decreased milk production, which may warrant culling of young, seropositive replacement stock.     

Parameters of test day milk yield and milk components for dairy ewes

A total of 3119 test day records for milk yield, somatic cell count (SCC), and contents of fat, protein, casein, serum protein, lactose, and total solids were obtained weekly from 155 lactations of Churra ewes during both the suckling and milking periods. All of the variables were significantly affected by stage of lactation, number of live lambs weaned, age at parity, and parity number within age. The lactation curves for SCC and for percentages of protein, casein, fat, and total solids were related inversely to the lactation curves for milk yield and lactose percentage. The SCC curve reached its lowest point at wk 5, which coincided with the maximum milk yield. At wk 3, lactose content reached its peak, and contents of fat, protein, casein, and total solids reached their lowest points. After weaning, monthly within-lactation correlations of the variables were simulated; values were 0.584 for yield, 0.468 for SCC, 0.371 for casein percentage, 0.360 for total solids percentage, 0.350 for protein percentage, 0.342 for fat percentage, 0.270 for lactose percentage, and 0.030 for serum protein percentage. Simplified procedures based on only one milking (a.m. or p.m.) could be effective in the testing programs for milk yield and SCC, thus, reducing the economic costs of milk recordings in mammary health and breeding programs.     

Environmental reservoirs for Serratia marcescens intramammary infections in dairy cows

Via special media, Serratia marcescens isolates were found in 3 bedding pack samples and in 2 milking parlor floor samples, and in milk samples from 19 cows during an episode of mastitis in a dairy cow herd. Chromosomal digest patterns of isolated S marcescens were indistinguishable for 18 of the milk samples and all bedding pack samples. Our findings provide strong evidence that the bedding pack was the reservoir of S marcescens associated with the outbreak of intramammary infections. Additionally, our ability to match digest patterns of isolates in the bedding pack and milk confirms the theory that S marcescens is an environmental pathogen capable of causing mastitis.     

Modeling the impact of mastitis on milk production by dairy cows

Individual milk production curves of 542 cows with 722 cases of mastitis were compared with control curves drawn from healthy lactating cows. First, differences were classified into patterns of milk loss, and their distribution was analyzed among the patterns with regard to breed, season, lactation number, stage of lactation, and milk production. Then, individual milk losses were estimated and analyzed according to the same factors. In early lactation, almost 7% of mastitis cases necessitated culling or drying off. For 36% of the cases of mastitis occurring in early lactation, milk production was affected for an extended period, and the milk loss induced was 911 kg on average over the entire lactation. Fifty-two percent of the mastitis cases occurring after lactation peak was not accompanied by marked modifications of the lactation curves. For 38% of cases of mastitis occurring from mid to late lactation, milk production was affected for an extended period. When milk production was the most affected (26% of total cases), the average loss was 850 kg over the entire lactation. For cases in early or mid to late lactation, the production at mastitis onset was a determining factor of the amount and pattern of milk production loss induced. Results were applied in a simulation over two simulated groups of cows.     

Recovery of Staphylococcus aureus from centrifuged quarter milk samples

The identification of cows that are positive for mastitis caused by Staphylococcus aureus is difficult under field conditions. The frequency of isolation of S. aureus from quarter milk samples was compared with the frequency of recovery of S. aureus from sediment after centrifugation of those same samples. Overall, 776 quarter milk samples from 194 cows were studied. Cultures that were positive for S. aureus were obtained from 82 samples; 153 sediments from quarter milk samples were also positive for S. aureus. The results of this investigation showed that cultures of the sediment of quarter milk samples increased the number of positive outcomes up to 145.5%, depending on the herd. Using a different group of samples, including samples taken 1 to 5 d or 7 to 10 d after calving and samples taken after intramammary therapy, a 94% increase in cultures that were positive for S. aureus after centrifugation was found compared with cultures of the same quarter milk samples that were not centrifuged. Sedimented cultures may be useful in S. aureus control programs that require the segregation, selective treatment, or culling of cows that are positive for S. aureus.     

Variations with breed, age, season, yield, stage of lactation and herd in the concentration of urea in bulk milk and individual cow's milk

The concentration of urea in the milk of 510 dairy cows in 10 herds was determined at regular intervals for a year. The herds contained approximately equal numbers of Swedish Red and White, and Swedish Holstein cows. The mean +/- sd concentration in the samples from individual cows was 5.32 +/- 1.13 mmol/l, and the mean concentration in bulk milk was 5.39 +/- 0.96 mmol/l. These values indicated that on average the herds were fed too much protein relative to their intake of energy throughout the year. Herd factors had a strong influence on the milk urea concentration. The concentration was lower during the first month of lactation than later in the lactation, and lower when the cows were housed during the winter than when they were grazing. There was a weak positive relationship between the daily milk yield and urea concentration, particularly during late lactation, but there was no relationship with either breed or age. Bulk milk urea was a reliable guide to the average urea concentration of a herd.     

Use of physiologic variables to predict milk yield after clinical mastitis in dairy cattle

OBJECTIVE: To determine the association between intramammary infections caused by various bacteria and hepatic damage, as measured by serum sorbitol dehydrogenase (SDH) activity, WBC counts, and PCV and the association of clinical variables with milk production after a case of clinical mastitis. DESIGN: Prospective, cohort study. ANIMALS: 82 cows with clinical mastitis. PROCEDURE: Information on milk production, mastitis status, and selected physiologic variables was collected during a 1-year period. Milk samples for bacteriologic evaluation were collected on day 1 of an episode of clinical mastitis. Physical examination was performed and blood samples for laboratory evaluation were collected on days 1, 5, and 9. Primary outcome was mature equivalent 305-day (ME305) milk production. Correlations were assessed using a multiple regression model. RESULTS: Higher WBC counts were associated with higher ME305 values. For cows with coliform mastitis, increases in SDH values were associated with higher ME305 values. For cows with coliform and streptococci/staphylococci mastitis, PCV was associated with ME305 values. Higher PCV values were associated with lower ME305 values for streptococci/ staphylococci and coliform infections. CLINICAL IMPLICATIONS: The association between milk production and WBC count indicated that cows mobilizing WBC were better able to neutralize mammary gland infections, which may result in better milk production. The association between milk production and PCV suggested that maintaining hydration in cows with clinical mastitis may be a critical aspect of treating all cows with mastitis.     

Feed intake relative to stage of lactation for dairy cows consuming total mixed diets with a high or low ratio of concentrate to forage

This experiment examined the effect of feed quality on the relationship between intake and stage of lactation in dairy cows. Two total mixed diets composed of grass silage and concentrate were formulated. The high concentrate total mixed diet was designed to meet energy requirements, and the low concentrate total mixed diet was designed to limit intake. Twenty-four Holstein-Friesian cows were offered the total mixed diets in a full 2 x 2 change-over design with control treatments. The changeover was at 153 d in milk (DIM). For the statistical analyses, two periods of 13 wk, one period before and one period after the changeover, were used. Dry matter intake (DMI), milk yield, body weight, and body condition score were significantly greater for cows fed the high concentrate total mixed diet than for cows fed the low concentrate total mixed diet. Significant interactions between total mixed diet and period were observed for DMI and milk yield. However, no significant residual effects of changing from one total mixed diet to the other were observed. The interactions were due to substantially different slopes of DMI and milk yield relative to DIM for cows fed the two different total mixed diets. For cows fed the low concentrate total mixed diet, there was no effect of stage of lactation on DMI; the slope was 0. For cows fed the high concentrate total mixed diet, there was a significant decline in DMI as lactation progressed.