Sixteen Holstein cows were used to test the effect of postmilking teat treatment on colonization and intramammary infection by Staphylococcus aureus on chapped teats. Treatments were (1) chapping the teat and using 1% I2/10% glycerin postdip solution, (2) 1% I2/10% glycerin postdip solution on nonchapped teats, (3) chapping the teat and using 10% glycerin postdip solution, (4) chapping the teat and not using a postdip solution. All mammary glands were free of S aureus teat skin colonization and intramammary infection at the start of the study. Teats selected for chapping were dipped in 1N NaOH prior to 3 applications of S aureus broth culture; cultures were applied at 12-hour intervals on all teats. Treatments were applied after each milking for 30 days and were initiated after the second broth dip. Teat skin swab specimens and milk samples were collected before treatment application. Teat skin condition was scored daily. Nonchapped teats (treatment 2) did not support skin or orifice colonization by S aureus. Treatment-1 teats healed most rapidly and supported less colonization in skin and orifice than did treatment-3 and -4 teats. Teat skin scores and skin colonization were lower for treatment-3 than treatment-4 teats. A correlation between teat skin colonization and teat skin conditions was found. Two intramammary infections were found in treatment-4 quarters and 1 in a treatment-3 quarter. On the basis of our findings, we concluded that poor teat skin condition will more readily support S aureus colonization, that a dip of 1% I2 with glycerin helped reduce S aureus colonization and was associated with faster healing, and that glycerin in teat dips may be of value in preventing colonization by S aureus and in promoting healing.

Twenty mature Holstein cows were randomized into 5 treatment groups. Cows of groups 2 to 5 were given 2 mg of elemental Pb/kg of body weight for 28 days. Clinical signs of plumbism were scored, and blood for Pb, progesterone, and hematologic analyses was collected weekly. Cows also were examined weekly for anomalous ovarian cycles. Starting on study day 28, cows in group 3 were treated once daily with 2 mg of thiamine HCl/kg (IM) for 13 days, cows in group 4 were treated twice daily with 62 mg of Na2,Ca-EDTA/kg (IV) for 4 days, and cows in group 5 were given thiamine (dosage regimen the same as for group 3) plus Na2,Ca-EDTA (dosage regimen the same as for group 4). On study days 96 through 139, cows were slaughtered in a commercial abattoir and samples of blood, skeletal muscles, bones, liver, and kidneys were collected and assayed for Pb concentration. Thiamine was not effective in reducing blood Pb concentration, and treatment with Na2,Ca-EDTA and thiamine plus Na2,Ca-EDTA was effective in reducing the concentration of Pb in blood. However, treatment with thiamine was more effective than treatment with Na2,Ca-EDTA or thiamine plus Na2,Ca-EDTA in inducing remission of clinical signs of plumbism. The concentration of Pb in blood was significantly (P < 0.05) correlated to the concentration of Pb in liver, kidneys, skeletal muscles, and bones. Significant (P < 0.05) relationship existed between number of days from Pb exposure to slaughter and concentration of Pb in blood, liver, and skeletal muscles. Exposure to Pb did not significantly alter CBC values. On the basis of progesterone analysis and ovarian examination, exposure to Pb and treatment for plumbism did not induce changes in the ovarian cycle.

Four consecutive 6-hour urine sample collections were performed on 7 healthy adult Holstein cows fed a diet of coastal Bermuda hay with ad libitum water consumption. Urine (via indwelling urinary catheter) and venous blood samples were collected at 6, 12, 18, and 24 hours. Total 24-hour urine production for the 7 cows ranged from 4,515 to 7,130 ml/d (mean +/- SD, 5,633 +/- 946 ml/d) or 0.02 to 0.04 ml/kg of body weight/d (mean +/- SD, 0.03 +/- 0.007 ml/kg/d). Renal clearance (C) of creatinine (Cr), sodium (Na), calcium (Ca), and magnesium (Mg) varied significantly (P less than 0.05) among individuals, but did not vary significantly among the four 6-hour collection periods. Clearance of chloride (Cl) and phosphorous (P) did not vary significantly either among individuals or among the four 6-hour periods. Clearance of potassium (K) varied significantly (P less than 0.05) among individuals and among the four 6-hour periods. Creatinine clearance was significantly (P less than 0.01) correlated with CCl, CCa, CP, and CMg when all data were considered. Significant (P less than 0.05) correlations were also found between CCl, and CK, CCa, CP, and CMg; between CCa and CP and CMg; and between CP and CMg. Fractional excretion (FE) of Na, K, Cl, Ca, P, and Mg did not vary significantly among the four 6-hour periods. Fractional excretion of Na, Ca, and Mg (P less than 0.01) and K and P (P less than 0.05) varied significantly within individuals among the 6-hour periods. Mean FE values, calculated by averaging values for each of the 4 collection periods for all 7 cows, ranged from 0.05 to 0.78% for FENa; 129.33 to 670.40% for FEK; 1.23 to 6.23% for FECl; 0.17 to 4.44% for FECa; 0.36 to 1.14 for FEP; and 4.96 to 11.73% for FEMg. Linear relationships between the clearance and fractional excretion of electrolytes were observed on base-10 logarithmically transformed data for Na, Ca, P, and Mg. Linear relationship was not found between CK and FEK or between CCl and FECl.

The relative sensitivity of bovine blood monocytes and macrophages isolated from milk to lipopolysaccharide, with respect to interleukin 1 (IL-1) production, was evaluated. Addition of lipopolysaccharide (0 to 30 microgram/ml) to theculture medium resulted in increases in secreted and intra-cellular IL-1 activity for monocytes and milk macrophages, with maximal stimulation achieved at 30 microgram oflipopolysaccharide/ml of medium. At this concentration of lipopolysaccharide, monocytes released 76% of the total IL-1, whereas milk macrophages released only 26% of the total IL-1 produced within the cell. Secretion of a small quantity of IL-1 was a common property of macrophages isolated from healthy and mastitic quarters. We concluded that limited secretion of IL-1 may render the milk macrophages less efficient in promoting lymphocyte activation.

Phagocytic and nitroblue tetrazolium (NBT) reductive activities of blood neutrophils from 19 Holstein heifers were measured by light microscopic and spectrophotometric methods, respectively. These functional properties of neutrophils correlated well (r = 0.64) and varied significantly (P < 0.05) among animals studied. Variations in phagocytosis and NBT reductive activities attributable to the source of sera were determined in experiments in which cells from the same cows and zymogen particles opsonized with heat-inactivated autologous or homologous sera were used. Variations attributable to the source of cells were determined in experiments in which cells from different cows and particles opsonized with pooled sera from all the cows were used. Most of the variation in phagocytic properties and NBT reductive activities was attributable to the source of cells (ie, each cow). The source of sera contributed slightly to the variation in NBT reductive activities, but not to the phagocytic properties. These results support the concept of functional heterogeneity of neutrophils among cows.

Hydrated sodium calcium aluminosilicate (HSCAS), an anticaking agent for agricultural feeds, was added to aflatoxin (AF)-contaminated diets of 3 lactating dairy cows and evaluated for its potential to reduce aflatoxin M1 (AFM1) residues in milk. During phase I, cows were fed alternating diets that consisted of 200 microgram of AF/kg of feed for 7 days, 0.5% HSCAS plus 200 microgram of AF/kg of feed for 7 days, and feed with the HSCAS removed for a final 7 days. The AFM1 milk concentrations from the intervals with HSCAS added to diets were compared with those times when HSCAS was absent. The presence of 0.5% HSCAS in feed containing 200 microgram of AF/kg reduced AFM1 secretion into the milk by an average of 0.44 microgram/L (from pretreatment of 1.85 microgram/L to 1.41 microgram/L with HSCAS, a 24% reduction). Following a 10-day period of noncontaminated feed consumption and no AFM1 residues in the milk, phase II of the study was begun. The same experimental design as phase I was used, but the dosages of HSCAS and AF were changed to 1.0% and 100 microgram/kg of feed, respectively. The addition of 1.0% HSCAS in feed containing 100 microgram of AF/kg decreased AFM1 content in the milk by an average of 0.40 microgram/L (from a pretreatment of 0.91 microgram/L to 0.51 microgram/L when HSCAS was present, a 44% reduction). These findings suggest that HSCAS, a high-affinity sorbent compound for AF in vitro, is capable of reducing the secretion of AFM1 into milk.

Milk samples were collected at onset of 508 episodes of clinical mastitis on a 1,700-cow dairy farm in Michigan. Daily milk production and disease events were recorded for all cows in the herd. Despite statistical association with severity of mastitis, this association was too weak for N-acetyl-beta-D-glucosaminidase (NAGase) activity to be of great value as a prognostic test for clinical mastitis. High milk NAGase activity was significantly (P < 0.0001) associated with: increased duration of treatment; increased duration of clinical signs of mastitis; decreased daily milk production; and increased risk of the cow being culled because of mastitis. The NAGase value was combined with days in milk production, baseline milk production before mastitis onset, parity, and season of onset to predict the outcome of clinical cases as measured by the first 3 aforementioned variables. Statistical models explained little of the variability among cows in duration of treatment (R2 = 0.11), duration of clinical signs of infection (R2 = 0.11), and milk production change (R2 = 0.09).

Polymorphonuclear cells have a critical role in the pathogenesis of bovine mastitis. We have documented that experimentally induced Staphylococcus aureus mastitis is associated with cyclic increase and decrease in the quantity of viable bacteria shed in the milk. Concomitant with this cycling of bacteria is an inverse cycling of the hosts cells within the milk. Such somatic cells were determined to be greater than or equal to 95% polymorphonuclear cells. The quality of these cells was evaluated by measuring their relative efficiency of bacterial killing and phagocytosis at various times during an infection. Host polymorphonuclear cells had as much as 10,000-fold variation in the bactericidal failure rate for staphylococci during cell cycling. The most efficient bactericidal effect was observed at or near the peak of the somatic cell count (SCC). The ability of these cycling cells to ingest fluorescent beads was also quantitated by use of flow cytometry. The percentage of phagocytic polymorphonuclear cells that ingested fluorescent latex beads ranged from 15 to 80% of the total cell population during cell cycling, and tended to be optimal at or near peak SCC. In addition, the average number of beads ingested varied between 1 and 2 particles/polymorphonuclear cell, with as many as 17% of the phagocytic cells ingesting 4 or more beads at maximal efficiency. Polymorphonuclear cells from quarters infected with S aureus varied quantitatively (total SCC) and qualitatively (bactericidal activity and phagocytic ability) during the course of an infection. Not only is the quantity of host's phagocytic cells in the mammary gland central to the defense mechanism against infection, but the biological activation state appears to be equally important. The role of these cells in the pathogenesis of a cycling infection is presented in a model to explain the cyclic nature of mastitis.

One hundred and fifty lactating Holstein cows from 2 genetic lines selected for high and average milk production were used in the study. Sera from 6 annual herd tests were analyzed by agar-gel immunodiffusion test for antibodies to bovine leukemia virus. Odds of being seropositive were analyzed by use of stepwise and backward logistic regression procedures. Analysis within birth year revealed that estimated ln odds increased by 0.19/year of age among cows of the high genetic line and by 0.43 among cows of the average genetic line. This was accompanied by a more important cohort effect among high producers than among average producers.

Pulmonary function tests were performed on seven adult dairy cows with an expanded tung field (ExLF) and the results were compared to the values from seven cows with normal lung fields. The cows with ExLF had an increased functional residual capacity (FRC) and end-tidal N2 concentration of the final breath of the multiple-breath N2 washout (FET(N2),fb), and an abnormal distribution of ventilation. The measurements of ventilation and gas exchange and pulmonary mechanics did not differ between the two groups. Postmortem examination of the lungs of five of the cows in each group indicated the cows with ExLF had a bronchiolitis with varying degrees of goblet cell hyperplasia, epithelial cell hyperplasia and metaplasia, smooth muscle hypertrophy, inflammatory cell infiltrate, vascular thickening, peribronchiolar fibrosis, and a mild overinflation of the lung. A histopathological score, based on the preceding indices and bronchus-associated lymphoid tissue, was correlated with FRC, FET(N2),fb, the lung clearance index and pulmonary resistance. There were no correlations between the histopathological score and any of the measures of ventilation and gas exchange.