Mastitis and fertility in cattle - possible involvement of inflammation or immune activation in embryonic mortality.

Causes for pre-implantation embryo loss, which can be as high as 50% or more of fertilized embryos, are multifactorial and largely undescribed. Studies in cattle using mastitis as a model indicate that one cause of early embryonic loss is infectious disease or activation of immune responses at sites outside the reproductive tract. Infection of the mammary gland in dairy cattle is associated with a reduction in pregnancy rate (proportion of inseminated cows that become pregnant) and an increase in the number of inseminations required to establish pregnancy.

Actions of tumor necrosis factor-alpha on oocyte maturation and embryonic development in cattle.

Problem: Infertility can accompany mastitis in cattle. Involvement of tumor necrosis factor-alpha (TNF-alpha) in this phenomenon is suggested by observations that circulating concentrations of TNF-alpha are elevated after intramammary infection or infusion of endotoxin. It was hypothesized that (1) TNF-alpha acts on the oocyte during maturation to decrease the percent of oocytes that cleave and develop following fertilization; (2) exposure of embryos to TNF-alpha after fertilization reduces development to the blastocyst stage; and (3) TNF-alpha increases the proportion of blastomeres that undergo apoptosis in a stage-of-development dependent manner.

Identification of possible mediators of embryonic mortality caused by mastitis: actions of lipopolysaccharide, prostaglandin F2alpha, and the nitric oxide generator, sodium nitroprusside dihydrate, on oocyte maturation and embryonic development in cattle.

Problem: Mastitis and immunization against constituents of organisms causing mastitis can reduce fertility of cattle and sheep, respectively. For the current experiments, it was hypothesized that these effects are mediated via actions of lipopolysaccharide (LPS), prostaglandin F2alpha (PGF2), and nitric oxide on oocyte maturation and embryonic development.

Method Of Study: To evaluate effects on oocyte maturation, oocytes were matured with various concentrations of LPS, PGF2alpha, or the nitric oxide (NO) generator, sodium nitroprusside (SNP).

Interactions of heat stress and bovine somatotropin affecting physiology and immunology of lactating cows.

During summer, 34 cows received daily injections of placebo or 25 mg of bST and were placed in a thermoregulated or a heat stress environment. Heat stress increased rectal temperatures, respiration rates, and plasma cortisol concentrations and decreased milk yield. Four of 9 bST-treated cows and none of 8 control cows became atactic on the 1st d of heat stress.

Analysis of somatic cell count data by a peak evaluation algorithm to determine inflammation events.

Increases in SCC are an expression of inflammation events in the udder. Inflammation events are sporadic, of variable amplitude and duration, and can be analyzed by computer programs designed to evaluate pulses of hormone secretion. Baseline values for SCC, which take into account long-term trends, were calculated using the PULSAR peak evaluation algorithm.

Modulation of function of bovine polymorphonuclear leukocytes and lymphocytes by high temperature in vitro and in vivo.

Function of polymorphonuclear leukocytes (PMNL) and proliferation of lymphocytes after stimulation with mitogens were evaluated in vitro at incubation temperatures of 38.5 and 42 C, and after in vivo heat stress of lactating Holstein cows. Cytochrome-c reduction and random migration of PMNL were reduced when cells were preincubated or incubated at 42 C, but high incubation temperature had little or no effect on phagocytosis and killing of Escherichia coli.

Actions of bovine somatotropin on polymorphonuclear leukocytes and lymphocytes in cattle.

Objectives were to determine 1) in vitro effects of bST on function of polymorphonuclear leukocytes and lymphocytes and 2) in vivo effects of bST on leukocyte function of heifers fed to maintain medium or high growth rates. When administered in vitro, bST did not affect function of polymorphonuclear leukocytes. [Methyl-3H]thymidine incorporation by resting lymphocytes was stimulated by 1000 ng/ml bST.

Consequences of diagnostic errors in mastitis therapy trials.

The effect of errors that occur in the diagnosis of intramammary infectious mastitis on the precision of experiments measuring the efficacy of mastitis therapy has been investigated. Diagnostic errors within the range found by experienced workers can create large biases in the apparent cure rate of therapy particularly at cure rates of less than 0.5.

Effects of administration of bovine somatotropin on milk yield and composition.

Thirty-two Holstein cows were assigned to four treatment groups in a continuous lactation trial to evaluate effects of daily subcutaneous injections of 0 (A), 5.15 (B), 10.3 (C), and 20.

Characterization of clinical mastitis records from one herd in a subtropical environment.

Patterns of occurrence and reoccurrence of clinical mastitis, duration of episodes, and number of quarters treated in a large north Florida dairy over 6.5 yr are described. Monthly incidence of milk disposal due to clinical mastitis varied within and between years and ranged from 1.

Climatic effects on occurrence of clinical mastitis.

Clinical mastitis records for 6.5 yr from a large north Florida dairy and corresponding daily weather data were analyzed. Monthly incidence of clinical mastitis was expressed as percent of cow-days in milk and graphed against monthly average daily maximum temperature humidity index values and monthly total rainfall.

Factors affecting days of discarded milk due to clinical mastitis and subsequent cost of discarded milk.

Records of clinical mastitis for 6.5 yr from one Florida dairy with 1050 to 1350 cows milking per month were used to predict duration of occurrence of clinical mastitis and to estimate dollar value of discarded milk per lactation with occurrences of clinical mastitis. Only 6.

Occurrence and reoccurrence of clinical mastitis.

Clinical mastitis records for 6.5 yr (July 1977 through November 1983) from a large north Florida dairy were analyzed. Observed frequencies of clinical mastitis were calculated in 7240 Holstein and Jersey lactations.

Comparison of teat dips with differing iodine concentrations in prevention of mastitis infection.

Six commercial dairy herds were used to test the relative efficacy of three concentrations of iodine as a teat dip over 12 mo. Concentrations were .1, .

Cost benefit analysis of lactation therapy with somatic cell counts as indications for treatment.

Lactating dairy cows (487) from five commercial herds were in a study of benefits from lactation therapy of sub-clinical mastitis. Bacterial isolations and composite milk samples for somatic cell counts were taken from each cow each month for 15 mo. Cows (254) in the experimental group were infused with cephapirin in all quarters for two consecutive milkings if somatic cell counts rose above 400,000 cells/ml; 103 cows were so treated.

Predictability by somatic cell counts related to prevalence of intrammary infection within herds.

Somatic cells were counted and bacteria identified for milk samples from 719 lactating dairy cows in 12 commercial herds. These pooled data were used to look at the accuracy of alternative thresholds of somatic cell counts as indicators of intramammary infection. Sensitivity, specificity, and predictability positive and negative at alternative cell count thresholds were calculated.

Effect of overmilking on udder health.

This study evaluated the effect on udder health of extending the milking period with or without vacuum fluctuation. Eighty cows were allotted into treatment groups consisting of 1) Control milked with normal milking equipment and the milker removed as soon as milk flow ceases; 2) milked for 12 min with normal equipment; 3) milked 12 min with induced vacuum fluctuations; and 4) normal milking time with induced fluctuations. Groups 2 and 3 had more newly infected quarters than groups 1 and 4.

Rapidity of cortisol transfer between blood and milk following adrenocorticotropin injection.

Cortisol concentrations in milk and blood plasma were measured in 12 lactating Holstein cows following administration of 40 IU adrenocorticotropin intravenously (groups 1 and 2) or 4 ml saline (control). Blood and milk samples were collected at 15 or 30-min intervals for 4 h from control and group 1 cows and at hourly intervals for 4 h from group 2. Cortisol concentrations in plasma and milk were increased 15 min after treatment and peaked by 1 h in group 1 but remained unchanged in controls.

Effect of adrenocorticotropin on milk and plasma cortisol and prolactin concentrations.

Milk cortisol and prolactin concentrations were measured in 12 lactating Holstein cows for 3 days (Experiment 1). On day 3, cows were divided randomly into groups: IV1, IV4, IM, and control. Group IV1 received one intravenous injection of 49 IU adrenocorticotropin, group IV4 the same dosage four times at 2-h intervals, group IM 240 IU adrenocorticotropin intramuscularly, and control cows were injected with saline.

Change in udder health and overmilking.

Removing milker units as soon as milk flow stopped was compared to milking for a fixed time of 12 min in an 8-wk trial with 60 cows. Teats were dipped in broth culture of approximately 10(9) colony forming units per ml of Staphylococcus aureus, Streptococcus agalactiae, and Streptococcus uberis for 4 wk. More new infections of quarters occurred in the 12-min group.

Role of teat dips and hygiene in mastitis control.

The primary sources of mastitis pathogens are infected quarters, chapped, sore, or eroded teat ends, and the environment. The major means of transfer of the most predominant mastitis pathogens is the milking routine. Methods are available to reduce the number of organisms normally transferred during each of the procedures.

Coliform contaminated bedding and new infections.

Ten Holstein cows were bedded on fresh, uncured sawdust seeded with coliform broth culture. Escherichia coli concentrations were maintained at 10(6) colony-forming units/g for the 4-wk experimental period. Ten control cows were bedded with dry shavings.

Effect of coliform challenge at milking time on new udder infections.

This project was designed to study rates of infection in udders of cows exposed to an Escherichia coli broth culture at milking time. Forty Holstein cows of varied stages of lactation were divided randomly into three treatment and one control group of ten cows each. The treatment groups were exposed for 3 wk to an Escherichia coli broth of 10(9) colony forming units per ml at milking time by either 1) dipping teat ends in broth before milking, 2) spraying the udder and leaving it dripping wet during milking, or 3) dipping teat ends in broth after milking.