Proteomic analysis of the temporal expression of bovine milk proteins during coliform mastitis and label-free relative quantification.

The discovery of biomarkers in milk indicative of local inflammation or disease in the bovine mammary gland has been hindered by the extreme biological complexity of milk, the dynamic range of proteins in the matrix that renders the identification of low-abundance proteins difficult, and the challenges associated with quantifying changes during disease in the abundance of proteins for which no antibody exists. The objectives of the current study were to characterize the temporal expression of milk proteins following Escherichia coli challenge and to evaluate change in relative abundance of identified proteins using a liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) label-free semiquantitative approach. Liquid chromatography-MS/MS conducted on whey from milk samples collected just before infusion with E. coli and at 12, 18, 24, 36, 48, and 60h following infection resulted in the identification of the high- to medium-abundance proteins alpha(S1)-, alpha(S2)- beta-, and kappa-caseins and the whey proteins serum albumin, beta-lactoglobulin, and alpha-lactalbumin. Additionally, a select number of lower abundance markers of inflammation were also identified, including lactoferrin, transferrin, apolipoprotein AI, fibrinogen, glycosylation-dependent cell adhesion molecule-1, peptidoglycan recognition receptor protein, and cyclic dodecapeptide-1. Normalized peptide counts for each protein identified were used to evaluate temporal changes in milk proteins following infection. For comparison with relative protein abundance determined using proteomic-based methods, changes in serum albumin, lactoferrin, and transferrin in milk during disease were also measured using ELISA. Label-free, proteomic-based quantification revealed relative changes in milk proteins that corresponded to expression profiles generated by ELISA. The results indicate that label-free LC-MS/MS methods are a viable means of tracking changes in relative protein abundance in milk during disease. Despite the identification of primarily abundant milk proteins, the results indicate that, with further refinement, LC-MS/MS could be used to evaluate temporal changes in proteins related to host response for which no antibody or ELISA currently exists.

Modeling nutrient fluxes and plasma ketone bodies in periparturient cows.

A mechanistic model was developed to study the interrelationship between glucose and lipid metabolism in periparturient cows. The driving variables were dry matter intake, feed composition, calf birth weight, milk production, and milk components. The response variables were body fat content and concentrations of plasma glucose, glycerol, nonesterified fatty acids (NEFA), and total ketone bodies (KB). Fetal growth and milk synthesis were assigned the highest priority for glucose demand in the model. The rate of fat mobilization was expressed as a function of glucose deficiency. The model assumed first-order kinetics for utilization of NEFA and KB. Model prediction errors were 19, 43, 48, and 36% of mean predictions for glucose, glycerol, NEFA, and KB, respectively. A linear bias was observed in KB and glycerol predictions. The model may be useful for understanding and explaining ketosis development.

Evaluation of a mechanistic model of glucose and lipid metabolism in periparturient cows.

A mechanistic model was previously developed to quantitatively describe glucose and lipid metabolism in periparturient cows. The objectives of the current study were to evaluate the accuracy and precision of the model by comparing predictions to data collected in an independent experiment; to identify the critical metabolic processes for ketosis development; and to use the model to evaluate the relative importance of dry matter intake, calf birth weight, milk yield, and body condition score on nutrition management. Residuals (observed - predicted) were regressed on model predictions using the independent data for the model inputs, and prediction error was calculated. Each model parameter (e.g., the rate of glucose consumption by peripheral tissues) was increased independently by 1 standard deviation to identify the critical metabolic processes for ketosis development. Critical control points to prevent ketosis were identified by increasing the driving variables of the model by 1 standard deviation to estimate the response in ketone body formation. The root mean square prediction error was 0.527 mM for ketone body predictions. The sensitivity analysis indicated that in the first few days of lactation, the rate of nonesterified fatty acid utilization had a greater effect on ketone body concentrations in periparturient cows than the other parameters tested in the model. The model was consistent with the knowledge that over-fattening during the prepartum period should be avoided to help prevent ketosis.

Effect of a transition diet on production performance and metabolism in periparturient dairy cows.

The objectives of this study were to characterize the change in blood metabolites over time, and to evaluate the effect of dietary energy concentration on ketone body accumulation in periparturient cows. Twenty-eight multiparous Holstein cows were listed in order of their anticipated due dates and assigned randomly to 1 of 2 groups: with or without a transition diet. The control group received a nonlactating cow diet [1.54 Mcal/kg of net energy for lactation (NE(L)), 10.9% crude protein (CP), 53.1% neutral detergent fiber (NDF)] from 28 d before expected parturition, and a lactation diet (1.77 Mcal of NE(L)/kg, 16.8% CP, 29.9% NDF) after parturition. The treatment group received a transition diet (1.71 Mcal of NE(L)/kg, 16.8% CP, 35.2% NDF) from 17 d before parturition to 14 d after calving and was fed the same diets as cows in the control group during the third week of lactation. Blood from the coccygeal vein was sampled 3 times per week from 21 d before expected parturition to 21 d postpartum for analysis of glucose, nonesterified fatty acids (NEFA), beta-hydroxybutyrate, acetoacetate, acetone, and glycerol. There were no significant differences in dry matter intake, milk yield, milk components, body weight change, and body condition score change during the postcalving period. Plasma concentrations of different ketone bodies changed in parallel, stayed relatively constant precalving, peaked after parturition, and then decreased but remained high compared with concentrations late in gestation. Plasma concentrations of NEFA and glycerol changed in a pattern similar to those of the ketone bodies. Feeding a transition diet resulted in a greater area under the curve (AUC) for glucose in the last 17 d of gestation, but in no effect within the first 21 d in milk. Acetoacetate AUC was greater for treatment cows than for control cows across the first 21 d in milk. The AUC of NEFA and glycerol between d 15 and 21 postpartum were greater for treatment cows than for control cows. Feeding a transition diet both before and after parturition was associated with greater mobilization of adipose tissue and greater exposure to ketone bodies in early lactation compared with abruptly changing to a lactation diet after parturition.

Evaluation of antinociceptive activity of Casearia sylvestris and possible mechanism of action.

The antinociceptive properties of Casearia sylvestris Sw. (Flacourtiaceae) were investigated in various models of pain-related behavior in mice. The hydroalcoholic crude extract of the plant (30-300mg/kg, per os) clearly inhibited nocifensive responses induced by ovalbumin (hindpaw licking) or acetic acid (writhes) in graded fashion. At 300mg/kg, the extract reduced nocifensive behaviors (from 71.1+/-13.3 to 14.8+/-9.3s; from 31.3+/-4.5 to 3.3+/-1.2 writhes, respectively) to similar extents as indomethacin (5mg/kg; 5.7+/-1.1s and 3.3+/-1.2 writhes, respectively). Significant antinociceptive effects in the hot plate test were only detected following administration of the highest extract dose, but this analgesic action appeared to be specific as the extract failed to change motor and exploratory activities. The antinociceptive effect of Casearia sylvestris extract in the acetic acid test was prevented by prior treatment with the non-selective opioid receptor antagonist naloxone (1mg/kg; 5.8+/-4.2 and 31.5+/-3.1 writhes in vehicle-treated and naloxone-treated groups, respectively), indicating that the endogenous opioid system is involved in its analgesic mechanism of action. Thus, our investigation suggests a potential therapeutic benefit of Casearia sylvestris Sw. in treating conditions associated with inflammatory pain.

Evaluation of 1.6% phenol as a premilking and postmilking teat dip in preventing new bovine intramammary infections.

We evaluated the effectiveness of a 1.6% phenol-based teat dip using both a teat skin assay and natural exposure field trial. A teat skin assay was conducted to ascertain the concentration of phenol + phenate to be used in the field study. One percent and 0.5% iodine, and 0.5, 1.1, and 1.6% phenol + phenate were compared using Escherichia coli and Staphylococcus aureus. Logarithmic reductions for S. aureus were 2.2 and 2.8 for 0.5 and 1% iodine, and 1.3, 2.1, and 2.8 for 0.5, 1.1, and 1.6% phenol + phenate, respectively. Logarithmic reductions for E. coli were 3.3 and 3.8 for 0.5 and 1% iodine, and 1.2, 1.9, and 2.6 for 0.5, 1.1, and 1.6% phenol + phenate, respectively. A concentration of 1.6% phenol + phenate was chosen as experimental teat dip, and 0.5% iodine served as control. The field study was conducted at Beltsville (n = 185) and Clarksville (n = 100) dairy herds using a split herd design. Teat dips were used premilking and postmilking for 12 mo. The number of new intramammary infections (IMI) for the Beltsville herd in iodine and phenol + phenate teat dipped cows were: 29 and 35 for major pathogens, and 81 and 72, for minor pathogens. For the Clarksville herd, number of new intramammary infections in iodine and phenol + phenate teat dipped cows was 9 and 10 for major pathogens, and 50 and 60 for minor pathogens. Rates of IMI per quarter day per lactation were not different for either herd or when herd data were combined. The number of clinical mastitis cases per 100 cows per month were similar in both treatments. The incidences of new IMI and clinical mastitis were similar using both dips.

Anti-inflammatory effects of the products from Wilbrandia ebracteata on carrageenan-induced pleurisy in mice.

Wilbrandia ebracteata Cogn. (Cucurbitaceae) is commonly known in Brazil as "Taiuia". The roots are employed in folk medicine for the treatment of several diseases, such as rheumatic disease. This study has evaluated the anti-inflammatory action of dicloromethane fraction (F-DCM), purified fraction (PFIII) and Cucurbitacin B extracted from crude extract of W. ebracteata in experimental models in vivo. The F-DCM (0.3 to 10 mg.kg(-1), i.p. or 3 to 30 mg.kg(-1) p.o.) produced significant but not dose-dependent inhibition of the carrageenan-induced cell influx and exsudate leakage in the pleural cavity of mice. The F-DCM 0.01 to 10 mg.kg(-1), i.p. or 0.1 to 10 mg.kg(-1) p.o.) decreased the levels of PGE2 in the exsudate leakage induced by carrageenan in the pleural cavity after 4 h with a calculated ID50 of 0.01 (0.002-0.09, i.p.) and 0.29 (0.05-1.45, p.o.) mg.kg(-1). The PFIII (3 mg.kg(-1), i.p.) inhibited 80% of cell migration (1.50 +/- 0.09 x 10(6) cells/cavity) and exsudate leakage by about 50% (3.09 +/- 0.71 microg/ml) in relation to the control group. Cucurbitacin B (0.1 mg.kg(-1), i.p.), the main compound of PFIII, reduced significantly the levels of PGE2 in the exsudate leakage by 40.7% (10.41 +/- 2.67 ng.ml(-1)). These data show that the active principle(s) present in the F-DCM of W. ebracteata elicited pronounced anti-inflammatory effects when assessed by i.p. or p.o. routes, as well as PFIII. The F-DCM was also able to prevent PGE2 formation in exsudate leakage induced by carrageenan, as well as Cucurbitacin B, its active principle. These results indicate that the anti-inflammatory activity of Wilbrandia ebracteata can be related with the inhibition of the production of PGE2.

Effects of a long daily photoperiod on milk yield and circulating concentrations of insulin-like growth factor-1.

Relative to a short daily (24-h) photoperiod, exposure to a long daily photoperiod increases the milk yield of dairy cows. However, the endocrine basis for this phenomenon is unknown. The present study was designed to test the hypothesis that a long daily photoperiod is associated with increased circulating insulin-like growth factor (IGF)-I, a hormone that is galactopoietic in ruminants. Forty lactating cows were exposed to either a natural photoperiod (< or = 13 h of light/d) or to a long daily photoperiod (18 h of light and 6 h of darkness) between January and April 1995. Cows were fed for ad libitum intake a total mixed diet formulated to meet the nutritional demands of lactation. Milk yield and dry matter intake were quantitated each day, and blood samples were collected by coccygeal venipuncture every 14 d. Plasma was harvested and assayed for IGF-I. The long photoperiod increased milk yield relative to the natural photoperiod (36.1 +/ 0.6 vs. 33.9 +/ 0.6 kg/d); the increase became significant after 28 d of treatment and was maintained for the duration of the study. In addition, cows exposed to a long photoperiod had greater circulating concentrations of IGF-I than did cows exposed to the ambient natural photoperiod (60.1 +/ 2.0 vs. 52.6 +/ 2.0 ng/ml). Concentrations of IGF binding protein -2 and -3 in plasma did not differ between treatments. These results support the hypothesis that a long daily photoperiod increases circulating concentrations of IGF-I in lactating cows and reveal a possible endocrine mechanism for the galactopoietic response to a long daily photoperiod.

Analysis of the role of nitric oxide in the relaxant effect of the crude extract and fractions from Eugenia uniflora in the rat thoracic aorta.

This study has evaluated the possible role played by the L-arginine-nitric oxide pathway in the vasorelaxant action of the hydroalcoholic extract from Eugenia uniflora, and fractions from the extract, in rings of rat thoracic aorta. The addition of an increasing cumulative concentration of hydroalcoholic extract from E. uniflora (1-300 micrograms mL-1) caused a concentration-dependent relaxation response in intact endothelium-thoracic aorta rings pre-contracted with noradrenaline (30-100 nM). The IC50 value, with its respective confidence limit, and the maximum relaxation (Rmax) were 7.02 (4.77-10.00) micrograms mL-1 and 83.94 +/- 3.04%, respectively. The removal of the endothelium completely abolished these responses. The nitric oxide synthase inhibitors N omega-nitro-L-arginine (L-NOARG, 30 microM) and N omega-nitro-L-arginine methyl ester (L-NAME, 30 microM), inhibited the relaxation (Rmax) to -10.43 +/- 7.81% and -3.69 +/- 2.62%, respectively. In addition, L-arginine (1 mM), but not D-arginine (1 mM), completely reversed inhibition by L-NOARG. Methylene blue (30 microM), a soluble guanylate cyclase inhibitor, reduced the relaxation induced by the extract to 14.60 +/- 7.40%. These data indicate that in the rat thoracic aorta the hydroalcoholic extract, and its fractions, from the leaves of E. uniflora have graded and endothelium-dependent vasorelaxant effects.

Anti-inflammatory and analgesic effects of cucurbitacins from Wilbrandia ebracteata.

The anti-inflammatory and antinociceptive actions of the CH2Cl2 extract and semipurified fraction (F-III) from roots of Wilbrandia ebracteata Cogn. have been investigated in rats and mice. The CH2Cl2 extract (1-10 mg/kg, i.p.; ID50 5 mg/kg) and (3-30 mg/kg, p.o.; ID50 15 mg/kg) inhibited, in a dose-related manner, carrageenan-induced paw edema in rats. The subfraction (F-III) from CH2Cl2 extract and compounds isolated as cucurbitacin B and E also inhibited carrageenan-induced edema. The CH2Cl2 extract and F-III also exhibited significant analgesic action in acetic acid-induced pain in mice. In the formalin test, the CH2Cl2 extract (0.3-10 mg/kg, i.p.) and (3-30 mg/kg, p.o.) caused inhibition of the neurogenic (first phase) and inflammatory phase (second phase) of formalin-induced pain. However, the CH2Cl2 extract was more effective in relation to the second phase than in inhibition of the formalin-induced edema. These findings suggest that CH2Cl2 extract has potent anti-inflammatory and analgesic action and that F-III and cucurbitacin B and E may account for these actions.

A demonstration project of interdisciplinary dairy herd extension advising funded by industry and users. 1. Implementation and evaluation.

An interdisciplinary team of extension workers conducted a 2-yr demonstration project using 30 herds with the objectives of increasing production efficiency and profitability and gaining experience in integrated problem solving. After 1 yr, 88% of the participants thought that the monthly fee paid to extension was a profitable investment. At the end of the project, 70% of the participants thought that increases in milk yield per cow were due to a combination of improvements in two to four management areas rather than to changes in any single management discipline. Additional labor was necessary to implement recommendations. Two issues were key in successfully convincing dairy operators and families to accept management recommendations: 1) a coordinated team effort aimed at integrated problem solving, followed by written recommendations and regular dialogue with the producer, and 2) possession of effective social decision-making skill by the participant family. Most farms in the project depended primarily on family labor and social decision making to implement management changes. Only those families that could jointly agree to implement a new management decision fully benefited from professional advice. A demonstration project of interdisciplinary dairy advising was an effective method to gain problem-solving expertise and to build credibility for extension services.

A demonstration project of interdisciplinary dairy herd extension advising funded by industry and users. 2. Impact on herd performance.

The objectives of this 24-herd, demonstration project of extension advising were to measure the impact of integrated problem solving on measures of DHI performance for 2 yr during and 2 yr after the project. During project advising, increases in rolling herd average milk and fat yields and 3.5% FCM were similar for project and state herds. When rolling herd average for milk yield for state herds was adjusted for two USDA milk reduction programs, milk yield of project herds was estimated to have increased 434 lb more per cow than that of DHI state herds. Compared with state DHI trends, project producers significantly improved in percentage of low SCC, days open, and age at first calving. Two years postproject, DHI milk yield declined for project and state herds, probably because of drought. Demonstration herds did not outperform state DHI herd average in milk yield or in other efficiency parameters during the 2-yr postproject. The extension advising in the demonstration project had the most positive impact on management of low ranking herds. Only low ranking herds had an advantage in rate of improvement, compared with high ranking herds, in rolling herd average for milk yield during and after the project and in SCC and days open during the project. Gains by managers of herds ranking low and in the middle in DHI parameters were generally lost or declining postproject.

A demonstration project of interdisciplinary dairy herd extension advising funded by industry and users. 3. Impact on management practices.

The objectives of this 24-herd, demonstration project of integrated problem solving and extension advising were 1) to evaluate dairy production management practices, 2) to formulate recommendations for guiding producers to correct management deficiencies, and 3) to measure the rate of practice adoption. Management evaluations focused on herd nutrition and forage crops, mastitis control and milking equipment, reproduction, and herd health. Sixty-eight management practices or milking equipment components were evaluated on each farm. A total of 216 recommendations were made in nutrition and forage crops as follows: calf and heifer management, 89; forage crops, 73; dry cows, 26; lactating cows, 19; and general, 9. The least adopted suggestions for nutrition and crops were for forage crop management. A total of 283 recommendations were made in mastitis management or milking equipment as follows: milking practices, 90; milking equipment, 90; general mastitis control, 61; environment, 32; calf management, 9; and stray voltage, 1. Producers most resisted updating and maintaining milking equipment within the milking management area. Detection of estrus was the focus of reproductive management advising. A total of 80 practices were recommended as follows: one person responsible, 24; specific location, 24; specific time, 24; and regular veterinary visits, 10. Designation of a specific site was the least adopted of these recommendations. Overall, 419 of 581, or 72%, of all recommendations were adopted.

Modulation of bovine neutrophil functions by monoclonal antibodies.

The main objective of the study reported here was to generate a panel of monoclonal antibodies (MAB) to bovine neutrophil surface antigens, and to identify MAB that modulate neutrophil chemotaxis, respiratory burst, and phagocytosis. A further objective was to study MAB reactivity with resting and activated neutrophils, to identify activation antigens and adhesion molecules. A panel of 14 MAB was generated by producing murine hybridomas. Neutrophils incubated with MAB at 4 C for 2 hours were used in chemotaxis, respiratory burst, and phagocytosis assays. Chemotaxis was evaluated in Boyden chambers, using Escherichia coli endotoxin-activated fetal bovine serum as the chemoattractant. Respiratory burst was determined by measuring chemoluminescence of neutrophils incubated with 5-amino-2,3-dihydro-1,4-phthalazinedione, and serum opsonized zymosan. Phagocytosis was determined by flow cytometry, using fluorescein-labeled Staphylococcus aureus. The MAB S7G8, S5F8G10, S7E10, and S5F8B8 enhanced chemotaxis (to > 125% of control). The MAB S7E10 and S8D9 enhanced respiratory burst activity (to > 125% of control), whereas MAB S2G8, S4G10, S8G10, and S5F8B8 caused inhibition (to < 75% of control). The MAB S2G8, S4G10, S8G10, and S5F8G10 enhanced phagocytosis (to > 125% of control). Chemotaxis, respiratory burst, and phagocytosis values of neutrophils not bound with MAB served as controls for comparison. The MAB binding for nonactivated neutrophils (at 4 C) ranged from 9 to 100%, and for activated neutrophils (at 37 C; at 37 C with phorbol myristate acetate) from 90 to 100%. Binding of MAB S4F5, S5F8B8, S6C6, S7E10, S8D9, and S5F8G10 increased when neutrophils had been incubated at 37 C.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional variation in endogenous and exogenous immunoglobulin binding to bovine neutrophils relative to parturition.

Ten healthy first- and second-lactation Holstein cows were observed from 1 week before to 1 week after calving and at postpartum day 30 to determine polymorphonuclear neutrophil (PMN) functional variation and immunoglobulin binding profiles. Blood and mammary PMN were obtained 3 times weekly and within 24 hours of calving. Functional traits measured included phagocytosis of Staphylococcus aureus and in vitro chemotaxis through micropore filters in a Boyden chamber. Additionally, PMN were evaluated for endogenous binding of IgG1, IgG2, IgA, and IgM before and after in vitro chemotaxis. Exogenous binding of the same isotypes was determined after incubation in pooled colostrum, purified immunoglobulin, and pooled sera. Phagocytosis results indicated a significant and transient increase in percentage of milk PMN with associated, rather than phagocytosed, bacteria for 1 week after calving. Blood PMN phagocytosis was not significantly different during this period. Though total chemotaxis was essentially unchanged, the percentage of PMN that were unable to complete migration increased substantially on the day of calving, an effect that disappeared by postpartum day 4. A significant (P < 0.01) positive correlation (r = 0.29) between percentage of PMN migrating completely through the micropore filter and percentage of blood PMN with associated bacteria was observed. Changes were not observed in endogenous immunoglobulin binding, with the exception of a peak in relative fluorescence intensity for IgG1 on the day of calving; this disappeared within 2 days after calving. Correlations between relative intensities of IgG2 and IgM, and percentage of mammary neutrophils phagocytosing were 0.37 and 0.70.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of involution on intramammary phagocytic defense mechanisms.

Mammary secretions (n = 34 cows) and mammary phagocytes (n = 18 cows) were collected throughout the nonlactating (dry) period to determine changes in intramammary phagocytic defense mechanisms. Mammary secretions were evaluated for their ability to support phagocytosis of Staphylococcus aureus by neutrophils from donor cows and mammary phagocytes for phagocytic and chemiluminescence activity. Ability of secretions to support phagocytosis decreased with advancing length of the dry period. This effect was more pronounced when dry cow secretions constituted 50% of the phagocytic mixture. Phagocytic activity of mammary phagocytes decreased with advancing dry period when autologous secretion was used in the incubation mixture. With homologous secretion, the percentage of phagocytosis increased 5 to 6 d after drying off compared with before drying off and then gradually decreased throughout the remainder of the dry period. Chemiluminescence activity (log10 counts per minute) of mammary phagocytes was lower during the dry period and decreased with advancing dry period. Results indicated diminishing ability of secretions to support phagocytosis and diminished phagocytic and bactericidal mechanisms during the dry period.

Intramammary response to modified intramammary devices.

Twenty-five cows in three experiments were used to evaluate the following intramammary devices: abraded surfaces; abraded and sulfur hexafluoride-coated; abraded, sulfur hexafluoride-coated, and weighted; and smooth surfaces and weighted. The objectives of the experiments were 1) to determine whether coating the abraded intramammary devices prevented amorphous deposits and bacterial adherence on the devices, 2) to determine whether addition of weight to devices increased the concentration of somatic cells in milk, and 3) to evaluate milk production and response of mammary epithelial cells to the devices. Milk SCC and NAGase (EC 3.2.1.30) from quarters fitted with devices were increased in quarter bucket and stripping milk, but increases were similar among all devices. Macrophages were the predominate cell type in quarter milk before insertion and neutrophils after insertion. Moderate to heavy deposits of amorphous material were observed on all devices, regardless of time residing in the gland. Approximately 50% of the devices were colonized after intramammary inoculation with Corynebacterium bovis. Milk production in control quarters and in quarters with devices were similar. Neither coating with sulfur hexafluoride nor addition of weight to devices reduced amorphous deposits or bacterial adherence or enhanced milk somatic cell response.

Total and differential somatic cell counts and N-acetyl-beta-D-glucosaminidase activity in mammary secretions during dry period.

Eighteen Holstein cows free of intramammary infection were sampled during dry period to measure changes in total SCC, differential cell counts, and N-acetyl-beta-D-glucosaminidase activity of milk or dry secretion. The design was to sample prior to and at drying off, two or more times during wk 1 of dry period, at 14 and 21 d of dry period, and after calving; 7 cows were sampled rotationally by quarters at 7, 14, and 21 d to avoid altering normal processes by repeated sampling. Total SCC of secretions declined just after drying off, increased to a peak of 6.593 (log10 scale) at 2 wk, and then declined slightly at 3 wk. Percentage of neutrophils rose from 33.3 at drying off to 83.8 at 1 wk and declined to 59.2 at 3 wk. Lymphocyte percentage declined in wk 1 of dry period but increased during wk 2 and 3. Activity of N-acetyl-beta-D-glucosaminidase in secretion rose throughout the first 3 wk of dry period.

Teat stimulation-induced release of prolactin and basal concentrations of prolactin and growth hormone in pregnant dairy and beef heifers.

The physiological bases for differences in milk production between breeds of cattle selected for beef or milk production are largely unknown. This study was conducted to determine concentrations of prolactin (PRL) and growth hormone (GH) in serum before and after teat stimulation in primiparous Hereford and Holstein heifers. Blood was collected from 6 beef and 9 dairy heifers at 115, 175, 230 and 250 d of gestation. Sampling times were -15, -10, -5, 0, 2, 4, 6, 8, 10, 12, 15, 20, 25 and 30 min relative to test stimulation. Mean areas under PRL response curves for beef and dairy heifers at 115, 175, 230 and 250 d of gestation were 427, 447, 556, 273 and 243, 189, 167, 343 ng/ml/30 min, respectively. Calculations of area (but not basal levels) excluded instances when no PRL response to test stimulation was obtained (22%). Neither stage of gestation nor breed affected PRL response. Basal PRL did not differ between breeds and was 1.8, 2.6, 2.4 and 9.2 ng/ml at 115, 175, 230 and 250 d of gestation. GH did not differ between breeds and was 6.6, 6.2, 5.5 and 7.4 ng/ml at 115, 175, 230 and 250 d. No difference between breeds was apparent with regard to PRL or GH secretion during first gestation.

Effect of intramammary devices on the outcome of induced Escherichia coli infection of bovine mammary quarters.

Eighteen Holstein cows, free of intramammary infection, were fitted with smooth (n = 9) or abraded (n = 9) intramammary devices (IMD) in 2 diagonally opposed quarters within 4 weeks after calving. The 2 other quarters of each cow were used as controls. Three to 6 weeks after IMD insertion, depending on when milk somatic cell counts returned to a base-line value of less than 4 X 10(5)/ml, all cows were subjected to bacterial challenge exposure in the front or rear quarters by intracisternal injection of about 30 colony-forming units of Escherichia coli/quarter. Challenge exposure was done immediately after milking. Three weeks after the initial bacterial exposure, the other quarter pairs were similarly challenge exposed. Quarter bacteriologic status, concentration of milk somatic cells, and clinical observations (rectal temperature, milk appearance, udder palpation, and general condition of the cow) were monitored. Infection developed in 14 of 16 (88%) quarters with smooth IMD vs 16 of 16 (100%) control quarters and in 7 of 17 (41%) quarters with abraded IMD vs 17 of 17 (100%) control quarters. The difference in infection frequency between quarters with smooth IMD and quarters with abraded IMD was significant (P less than 0.05). Protection against establishment of infection was associated with somatic cell counts greater than 8.0 X 10(5)/ml in milk collected immediately after milking (7 of 12 quarters) or 4 hours later (11 of 12 quarters). In 10 quarters (59%) of cows fitted with abraded IMD, secretory abnormalities appeared before bacterial challenge inoculation. Abnormal milk or visible blood was observed over periods varying from 2 weeks after insertion through the entire lactation.