Endocrine aspects in pathogenesis of mastitis in postpartum dairy cows

Chronic inflammation decreases arcuate kisspeptin expression in male sheep

Lipopolysaccharide (LPS) from Gram-negative bacteria induces an immune response and impairs reproduction through suppression of gonadotropin releasing hormone (GnRH), subsequently luteinizing hormone (LH) secretion. While there is evidence that acute inflammation inhibits kisspeptin, little is known about the impact of chronic inflammation on this key reproductive neuropeptide in livestock species. Thus, we sought to examine a central mechanism whereby LPS suppresses LH secretion in sheep. Twenty wethers were randomly assigned to one of five treatment groups: control (CON; n=4), single acute IV LPS dose (SAD; n=4), daily acute IV LPS dose (DAD; n=4), daily increasing IV LPS dose (DID; n=4), and chronic subcutaneous LPS dose (CSD; n=4). On Days 1 and 7, blood samples were collected every 12 minutes for 360 minutes using jugular venipuncture. Following blood collection on Day 7, all animals were euthanized, brain tissue was perfused with 4% paraformaldehyde, and hypothalamic blocks were removed and processed for immunohistochemistry. On Day 1, LH pulse frequency was significantly lower (p=0.02) in SAD (0.25 ± 0.1 pulses/hour), DAD (0.25 ± 0.1 pulses/hour), DID (0.35 ± 0.1 pulses/hour), and CSD (0.40 ± 0.1 pulses/hour) compared to CON (0.70 ±0.1 pulses/hour). On Day 7, only DID animals (0.35 ± 0.1 pulses/hour) had significantly lower (p=0.049) LH pulse frequency compared to controls (0.85 ± 0.1 pulse/hour). Furthermore, only DID animals (33.3 ± 10.9 cells/section/animal) had significantly fewer (p=0.001) kisspeptin-immunopositive cells compared to controls (82.6 ± 13.6 cells/section/animal). Taken together, we suggest that daily increasing doses of LPS is a powerful inhibitor of kisspeptin neurons in young male sheep and a physiologically relevant model to examine the impact of chronic inflammation on the reproductive axis in livestock.

A Study on Differential Biomarkers in the Milk of Holstein Cows with Different Somatic Cells Count Levels

Dairy cow mastitis is one of the common diseases of dairy cows, which will not only endanger the health of dairy cows but also affect the quality of milk. Dairy cow mastitis is an inflammatory reaction caused by pathogenic microorganisms and physical and chemical factors in dairy cow mammary glands. The number of SCC in the milk of dairy cows with different degrees of mastitis will increase in varying degrees. The rapid diagnosis of dairy cow mastitis is of great significance for dairy cow health and farm economy. Based on the results of many studies on the relationship between mastitis and somatic cell count in dairy cows, microflora, and metabolites in the milk of Holstein cows with low somatic cell level (SCC less than 200,000), medium somatic cell level (SCC up to 200,000 but less than 500,000) and high somatic cell level (SCC up to 5000,00) were analyzed by microbiome and metabolic group techniques. The results showed that there were significant differences in milk microbiota and metabolites among the three groups (p < 0.05), and there was a significant correlation between microbiota and metabolites. Meanwhile, in this experiment, 75 differential metabolites were identified in the H group and L group, 40 differential metabolites were identified in the M group and L group, and six differential microorganisms with LDA scores more than four were found in the H group and L group. These differential metabolites and differential microorganisms may become new biomarkers for the diagnosis, prevention, and treatment of cow mastitis in the future.

Effects of different nutrient supply on metabolism and mammary immune response to an LPS challenge in early lactation of dairy cows

Energy and nutrient deficiency in dairy cows in early lactation is considered to contribute to their increased susceptibility to mastitis. We have tested the hypothesis that feeding diets with high contents of either nitrogenic, glucogenic, or lipogenic components in early lactation affects both the endocrine and metabolic status, as well as the mammary immune competence. After calving, cows were fed increasing amounts of concentrate up to 10 kg/d rich in crude protein (nitrogenic, n = 10), glucogenic precursors (glucogenic, n = 11), or lipids (lipogenic, n = 11). In wk 3, one udder quarter was challenged with lipopolysaccharide (LPS) from Escherichia coli. Blood and milk were sampled on the day before LPS challenge (d -1), and on d 0, 1, 2, 3, and 9 after LPS challenge. On the day of LPS challenge additional samples were taken hourly for quarter milk and every 3 h for blood. Urea concentrations were higher in plasma and milk of cows fed the nitrogenic diet. However, plasma concentrations of glucose, cholesterol, triglycerides, β-hydroxybutyrate, nonesterified fatty acids, as well as insulin, glucagon, and insulin-like growth factor-1 were not affected by the different diets. The mammary immune challenge induced a substantial increase of somatic cell count (SCC) in the treated quarter, and a transient decrease of total milk yield and white blood cells similar in all diet groups for one day. The absolute phagocytosis of blood leukocytes was decreased; however, the phagocytosis per cell was increased in glucogenic-fed cows at 6 h after LPS challenge. During mammary inflammation an insulin resistance, shown by increased plasma glucose, insulin, and glucagon, developed similarly in all diet groups. β-hydroxybutyrate and nonesterified fatty acids were decreased at 1 d after LPS challenge in glucogenic-fed cows only. Cholesterol did not change, and triglycerides only decreased significantly in lipogenic-fed cows 6 h after challenge. On d 9 after LPS challenge, SCC and milk yield and metabolic factors were recovered in all groups. In conclusion, the endocrine and metabolic situation, and the immune response to intramammary LPS of dairy cows during early lactation was not substantially influenced by the elevated supply of nitrogenic, glucogenic, or lipogenic components due to the provided feed in this study.

Mastitis: What It Is, Current Diagnostics, and the Potential of Metabolomics to Identify New Predictive Biomarkers

Periparturient diseases continue to be the greatest challenge to both farmers and dairy cows. They are associated with a decrease in productivity, lower profitability, and a negative impact on cows’ health as well as public health. This review article discusses the pathophysiology and diagnostic opportunities of mastitis, the most common disease of dairy cows. To better understand the disease, we dive deep into the causative agents, traditional paradigms, and the use of new technologies for diagnosis, treatment, and prevention of mastitis. This paper takes a systems biology approach by highlighting the relationship of mastitis with other diseases and introduces the use of omics sciences, specifically metabolomics and its analytical techniques. Concluding, this review is backed up by multiple studies that show how earlier identification of mastitis through predictive biomarkers can benefit the dairy industry and improve the overall animal health.

The Relation between Hair-Cortisol Concentration and Various Welfare Assessments of Dutch Dairy Farms

Many protocols have been developed to assess farm animal welfare. However, the validity of these protocols is still subject to debate. The present study aimed to compare nine welfare assessment protocols, namely: (1) Welfare Quality^© (WQ), (2) a modified version of Welfare Quality (WQ Mod), which has a better discriminative power, (3) WelzijnsWijzer (Welfare Indicator; WW), (4) a new Welfare Monitor (WM), (5) Continue Welzijns Monitor (Continuous Welfare Monitor; CWM), (6) KoeKompas (Cow Compass; KK), (7) Cow Comfort Scoring System (CCSS), (8) Stall Standing Index (SSI) and (9) a Welfare Index (WI Tuyttens). In addition, a simple welfare estimation by veterinarians (Estimate vets, EV) was added. Rank correlation coefficients were calculated between each of the welfare assessment protocol scores and mean hair cortisol concentrations from 10 cows at 58 dairy farms spread over the Netherlands. Because it has been suggested that the hair cortisol level is related to stress, experienced over a long period of time, we expected a negative correlation between cortisol and the result of the welfare protocol scores. Only the simple welfare estimation by veterinarians (EV) (ρ = -0.28) had a poor, but significant, negative correlation with hair cortisol. This correlations, however, failed to reach significance after correction of p-values for multiple correlations. Most of the results of the different welfare assessment protocols had a poor, fair or strong positive correlation with each other, supporting the notion that they measure something similar. Additional analyses revealed that the modified Welfare Quality protocol parameters housing (ρ = -0.30), the new Welfare Monitor (WM) parameter health (ρ = -0.33), and milk yield (ρ = -0.33) showed negative correlations with cortisol. We conclude that because only five out of all the parameter scores from the welfare assessment protocols showed a negative, albeit weak, correlation with cortisol, hair cortisol levels may not provide a long term indicator for stress in dairy cattle, or alternatively, that the protocols might not yield valid indices for cow welfare.

The association between subclinical mastitis around calving and reproductive performance in grazing dairy cows

The objective of this study was to evaluate the effect of subclinical mastitis (SCM) on calving-to-first-service interval (CFS), calving-to-conception interval (CC), and on the number of services per conception (S/C) in grazing Holstein and Normande cows. Primiparous (n=43) and multiparous (n=165) cows were selected from five dairy herds. Two composite milk samples were aseptically collected from each cow at drying-off, and then every week during the first postpartum month. One sample was used for somatic cell count (SCC), and the other one for bacteriological analysis. Cows were followed up to 300 d after calving. Non-parametric and parametric survival models, and negative binomial regression were used to assess the association between SCM, evaluated by SCC and milk culture, and reproductive indices. Staphylococcus aureus, CNS, and Streptococcus uberis were the most frequent isolated pathogens. Subclinical mastitis in the first month of lactation was not associated with CFS; however, the CC interval was longer in cows with SCM compared to healthy cows, the former also had a higher number of S/C.

Lipopolysaccharides, cytokines, and nitric oxide affect secretion of prostaglandins and leukotrienes by bovine mammary gland during experimentally induced mastitis in vivo and in vitro

The aim of the study was to determine the effects of lipopolysaccharide (LPS), tumor necrosis factor alpha (TNF), interleukin-1-alpha (IL-1α), and nitric oxide donor (NONOate) on both in vivo and in vitro secretion of prostaglandin (PG)E2, PGF2α, leukotriene (LT)B4, and LTC4 by the bovine mammary gland. In the first experiment, tissues isolated from the teat cavity and lactiferous sinus were treated in vitro with LPS (10 ng/mL), TNF (10 ng/mL), IL-1α (10 ng/mL), NONOate (10(-4) M), and the combination of TNF + IL-1α + NONOate for 4 or 8 h. PGE2 or PGF2α secretion was stimulated by all treatments (P < 0.05) excepting NONOate alone, which did not stimulate PGF2α secretion. Moreover, all factors increased LTB4 and LTC4 secretion (P < 0.05). In the second experiment, mastitis was experimentally mimicked in vivo by repeated (12 h apart) intramammary infusions (5 mL) of (1) sterile saline; (2) 250-μg LPS; (3) 1-μg/mL TNF; (4) 1-μg/mL IL-1α; (5) 12.8-μg/mL NONOate; and (6) TNF + IL-1α + NONOate into 2 udder quarters. All infused factors changed PGE2, 13,14-dihydro,15-keto-PGF2α, and LT concentrations in blood plasma collected from the caudal vena cava, the caudal superficial epigastric (milk) vein, the jugular vein, and the abdominal aorta (P < 0.05). In summary, LPS and other inflammatory mastitis mediators modulate PG and LT secretion by bovine mammary gland in both in vivo and in vitro studies.

Relationship of concentrations of cortisol in hair with health, biomarkers in blood, and reproductive status in dairy cows

Hair cortisol has been used to measure chronic stress in dairy cows as it offers the advantage of being noninvasive, fast, and able to indicate levels of cortisol over long periods. The aim of this study was to determine the associations between hair cortisol with clinical disorders, reproductive status, and the development of subclinical endometritis in dairy cows. Furthermore, we aimed to determine the association between hair cortisol concentrations and blood markers associated with metabolic status and acute inflammation. In experiment 1, cows (n=64) were hair sampled every 3wk from the tail switch beginning at calving (d 0) until d 126 for cortisol analysis; blood samples were collected every 3wk from d 0 until 42 for β-hydroxybutyrate and glucose analysis. In experiment 2, cows (n=54) were chosen retrospectively by diagnosis of subclinical endometritis (END), subclinical endometritis and at least 1 clinical disease (END+CLIN), or as healthy (control) using a cytobrush and ultrasonography at 30±3d in milk. At the same time, animals were hair sampled for cortisol analysis and blood sampled for haptoglobin and ceruloplasmin analysis. Health records were recorded throughout both experimental periods. Animals with clinical disease presented higher cortisol concentrations than clinically healthy animals in experiment 1 [geometric mean (95% confidence interval); 8.8 (7.8, 9.9) vs. 10.7 (9.6, 12.0) pg/mg]; however, animals diagnosed with subclinical endometritis in experiment 2 did not differ in hair cortisol concentrations [11.7 (9.8, 14.0), 12.2 (9.3, 15.9), 10.5 (8.1, 13.6) pg/mg for control, END, and END+CLIN, respectively]. In experiment 1, an effect of sample day was noted, where d 21 had higher cortisol concentrations than d 42, 84, and 126, but not from d 0 for both parities. Within both experiments, a parity effect was present where multiparous animals consistently had higher cortisol concentrations than primiparous animals. Multiparous cows that became pregnant by 100d postpartum had lower concentrations of hair cortisol at d 42 and 84 in milk. Lastly, other biomarkers associated with metabolic status and acute inflammation, such as glucose, β-hydroxybutyrate, haptoglobin, and ceruloplasmin, were not strongly correlated with measurements of cortisol in hair. Overall, hair cortisol measurements appear to be associated with clinical disorders and have a direct association with pregnancy status; however, concentrations of hair cortisol may not be suited to differentiate situations of stress with lower magnitudes, such as the development of subclinical disease.

Lipopolysaccharides, cytokines, and nitric oxide affect secretion of prostaglandins and leukotrienes by bovine mammary gland epithelial cells

The aims of this study were to determine the effects of lipopolysaccharides (LPS), tumor necrosis factor (TNF), interleukin 1 alpha (IL-1α), nitric oxide donor (NONOate), or the combination of TNF + IL-1α + NONOate on the following: (i) secretion of prostaglandin (PG)-F(2α), PGE(2), leukotriene (LT)-B(4), and LTC(4) by epithelial cells of the teat cavity and lactiferous sinus of bovine mammary gland; (ii) messenger RNA (mRNA) transcription of enzymes responsible for arachidonic acid (AA) metabolism (prostaglandin-endoperoxide synthase 2 [PTGS2], prostaglandin E synthase [PTGES], prostaglandin F synthase [PGFS], and arachidonate 5-lipooxygenase [ALOX5]); and (iii) proliferation of the cells. The cells were stimulated for 24 h. Prostaglandins and LT were measured by enzyme immunoassay, mRNA transcription of enzymes was determined by real-time reverse transcription polymerase chain reaction, and the cell viability was measured by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide. All factors increased PG secretion, but the highest stimulation was observed after TNF and IL-1α (P < 0.001). Tumor necrosis factor, NONOate, and TNF + IL-1α + NONOate increased LTB(4) production (P < 0.01), whereas LTC(4) was increased by LPS, TNF, and IL-1α (P < 0.01). Lipopolysaccharides, TNF, IL-1α, and the reagents combination increased PTGS2, PTGES, and PGFS mRNA transcription (P < 0.01), whereas ALOX5 mRNA transcription was increased only by TNF (P < 0.001). Lipopolysaccharides, TNF, IL-1α, NONOate, and the combination of reagents increased the cell number (P < 0.001). Mediators of acute-clinical Escherichia coli mastitis locally modulate PG and LT secretion by the epithelial cells of the teat cavity and lactiferous sinus, which might be a useful first line of defense for the bovine mammary gland. Moreover, the modulation of PG and LT secretion and the changing ratio of luteotropic (PGE(2), LTB(4)) to luteolytic (PGF(2α), LTC(4)) metabolites may contribute to disorders in reproductive functions.

Low cortisol levels in blood from dairy cows with ketosis: a field study

BACKGROUND

An elevated plasma glucose concentration has been considered to be a potential risk factor in the pathogenesis of left-displaced abomasums (DA). Therefore the present study was performed to investigate if spontaneous disease (parturient paresis, metritis, ketosis etc) in dairy cows results in elevated concentrations of glucose and cortisol in blood as cortisol is the major regulator of glucose in ruminants.

METHODS

Cortisol, insulin, beta-hydroxybutyric acid (BHBA), non esterified fatty acids (NEFA), and serum calcium were analyzed in blood serum and glucose, in whole blood, from 57 spontaneously diseased cows collected at different farms. The cows were grouped according to the disease; parturient paresis, recumbent for other reasons, mastitis, metritis, ketosis, inappetance and others.

RESULTS

No elevated concentrations of cortisol or glucose were found in cows with metritis and mastitis but both cortisol and glucose were elevated in cows stressed by recumbency. Cows with ketonemia (BHBA > 1.5 mmol/l) did not have low concentration of glucose in blood but significantly low levels of cortisol. Some of these cows even had cortisol concentrations below the detection limit of the analysing method (< 14 nmol/l).

CONCLUSIONS

The study gives patho-physiological support to the treatment strategies of ketosis, recommending glucocorticoids, insulin etc. However further studies of this problem are needed to understand why cows with ketosis have low levels of cortisol and normal levels of glucose. To what extent elevated cortisol and glucose levels in hypocalcemic and recumbent cows are involved in the ethiology and /or the pathogenesis of DA also will need further research.

The effect of Escherichia coli lipopolysaccharide and tumour necrosis factor alpha on ovarian function

PROBLEM

Pelvic inflammatory disease and metritis are important causes of infertility in humans and domestic animals. Uterine infection with Escherichia coli in cattle is associated with reduced ovarian follicle growth and decreased estradiol secretion. We hypothesized that this effect could be mediated by the bacterial lipopolysaccharide (LPS) or cytokines such as tumour necrosis factor alpha (TNFalpha).

METHOD OF STUDY

In vitro, bovine ovarian theca and granulosa cells were treated with LPS or TNFalpha and steroid secretion measured. In vivo, the effect of LPS or TNFalpha intrauterine infusion was determined by ovarian ultrasonography and measurement of hormones in cattle.

RESULTS

Lipopolysaccharide reduced granulosa cell estradiol secretion, whilst TNFalpha decreased theca and granulosa cell androstenedione and estradiol production, respectively. In vivo, fewer animals ovulated following intrauterine infusion with LPS or TNFalpha.

CONCLUSION

Lipopolysaccharide and TNFalpha suppress ovarian cell function, supporting the concept that pelvic inflammatory disease and metritis are detrimental for bovine ovarian health.

Effects of exogenous tumour necrosis factor-alpha on the secretory function of the bovine reproductive tract depend on tumour necrosis factor-alpha concentrations

The aim of study was to correlate tumour necrosis factor-alpha (TNF) infused doses used with the TNF concentrations achieved and with the secretory function of both the ovary and the uterus in cows. We evaluated the concentrations of progesterone (P4), prostaglandin (PG)F(2alpha), PGE(2) nitric oxide (NO) and TNF in the jugular vein and vena cava caudalis as parameters of exogenous TNF action on the female reproductive tract. Aortae abdominalis of cows (n = 18) were infused with saline or two doses of TNF (luteolytic--1 microg or luteotrophic--10 microg). In the peripheral blood, 1 microg TNF concentrations achieved within the range of 30-45 pg/ml, and 10 microg TNF provoked a sharp increase in achieved concentrations at a range of 250-450 pg/mL). The TNF concentrations achieved in vena cava caudalis were five to six times higher than that in peripheral blood (p < 0.001). One microgram TNF increased PGF(2alpha) and NO (p < 0.001) and decreased P4 (p < 0.05). The higher TNF dose stimulated P4 and PGE(2) (p < 0.01). TNF infusion at luteolytic dose achieved its concentrations at the physiological range previously observed in cows. Luteotrophic TNF dose achieved the concentrations in vena cava caudalis that are much higher than physiological level and were previously noted in pathological circumstances (i.e. mastitis, metritis).

Bacterial complications of postpartum uterine involution in cattle

The bacterial contamination of the postpartum uterus is a frequent finding which by itself does not disturb the anatomical and histological restoration of tubular genital tract. The improper balance between uterine infection and the intrauterine antimicrobial self-defence mechanisms, however, often results in complications, such as puerperal metritis, clinical endometritis, pyometra and subclinical endometritis. After reviewing the bacteriology of uterine involution, and the predisposing factors for its bacterial complications, this paper defines the different clinical forms, and summarizes their pathology, furthermore, the recent progress in diagnostic considerations and principles of current treatments for these diseases of bovine genitals.

Exogenous glucagon effects on health and reproductive performance of lactating dairy cows with mild fatty liver

Severe fatty liver, a metabolic disease of dairy cows in early lactation, results in decreased health and reproductive performance, but can be alleviated by treatment with i.v. injections of glucagon. Mild fatty liver in cows effects on health and reproductive performance were determined by treatment with 14-day s.c. injections of glucagon at 7.5 or 15 mg/day. Multiparous Holstein cows (n=32) were grouped into Normal and Susceptible based on liver triacylglycerol concentrations (>1% liver tissue biopsy wet weight) at day 8 postpartum (day 0=day of parturition). Susceptible cows (n=24) were assigned randomly to three groups and s.c. injected with 0mg glucagon [60 ml 0.15M NaCl] [n=8] (same for Normal cows), 2.5 mg glucagon, or 5 mg glucagon every 8 h for 14 days, beginning day 8 postpartum. Mild fatty liver resulted in an increased number of days with elevated body temperature during the injection period, an increased incidence of mastitis after glucagon treatment, increased days to first estrus and insemination, increased days before conception occurred, and decreased conception rate. In cows with mild fatty liver, glucagon (15 mg/day) decreased the number of days with elevated body temperature and the incidence of mastitis after hormone treatment. From these results, we suggest that mild fatty liver is detrimental to health and reproduction of dairy cows and, furthermore, that exogenous glucagon decreases some of these detrimental effects.

Effects of clinical mastitis on ovarian function in post-partum dairy cows

Mastitis-induced ovarian abnormalities were studied in a field trial. At 1-3 day after calving, > or = 2 parity cows not affected with chronic recurrent mastitis and yielding < 400,000/ml somatic cell count (SCC) individual milk in the previous lactation, were enrolled in the study. Thereafter milk samples were collected three times weekly for 95-100 day for progesterone (P4) assay. Individual P4 profiles were used to monitor ovarian cyclicity. When mastitis was diagnosed in the first 80 day post-partum (pp), clinical signs were recorded and scored, and aseptic milk samples were taken to identify the mastitis pathogens. Depending on the isolated pathogens the cows were blocked into one of the three sub-groups affected by either Gram-positive (GP), or Gram-negative (GN) bacteria, or of those with no detected pathogens (NDP). Cows suffering from any type of mastitis between days 15 and 28 (n = 27) showed a delay in the onset of ovarian cyclicity, and estrus was postponed compared to cows affected during the first 14 day pp (n = 59) and controls (n = 175) (38.6 +/- 2.3 vs 33.4 +/- 2.1 and 32.0 +/- 1.0 day, respectively, for onset of ovarian cyclicity and 90.7 +/- 2.5 vs 80.2 +/- 2.8 and 83.9 +/- 2.1 day, respectively, for estrus; both p < 0.05). The percentage of cows ovulating by day 28 was lower in those affected by mastitis between days 14 and 28 compared to cows between days 1 and 14 and controls (22.2% vs 47.5 and 50.3%, respectively; p < 0.05). A significantly higher rate of premature luteolysis was observed in GN + NDP compared to GP mastitis and healthy cows (46.7% vs 8.3 and 2.0%, respectively; p < 0.001). If the mastitis outbreak occurred during the follicular phase, the duration of this cycle segment was lengthened in GN + NDP mastitis compared to GP mastitis and healthy cows (10.8 +/- 0.9 vs 7.9 +/- 0.1 and 7.2 +/- 0.1, respectively; p < 0.001). The results indicate that mastitis can affect the resumption of ovarian activity in pp dairy cows. Mastitis may also impair reproduction also in cyclic cows: this effect can be the consequence of premature luteolysis or a prolonged follicular phase.

Feeding-unrelated factors influencing the plasma leptin level in ruminants

The triglyceride content of lipid depots associated with the current feeding level is the primary determinant of leptin gene expression and the circulating leptin level. In laboratory rodents and primates the plasma leptin is influenced also by the age, gender and physiological status (puberty, pregnancy, lactation, postpartum period), and by the health condition such as sepsis due to Gram-negative (GN) bacteria. Some pathologic conditions with intensive cytokine release evoke an increase in plasma leptin, which is thought to depress the subsequent feed intake. However, the effect of these secondary factors may be species-dependent, with still unknown clinical relevance in ruminants. In our ovine and bovine models plasma leptin increased after castration and dexamethasone treatment, decreased after experimental administration of synthetic androgens in castrated rams, but remained unchanged throughout the ovarian cycle and after ovariectomy. The circulating leptin level increased temporarily during synthetic progestin (fluorogestone) treatment in ewes, but similar changes were not seen in progesterone-supplemented ewes and norgestomet-treated cows. In a second trial on dairy cows we wanted to study whether elevated plasma leptin levels are induced by experimental endotoxin mastitis, or by natural outbreak of GN mastitis and puerperal metritis. Experimental endotoxin mastitis resulted in some-hour elevation in cortisol and insulin, with a simultaneous decrease in IGF-I and thyroid hormones. In the first 14 days of lactation GN mastitis induced the same endocrine alterations as the experimental endotoxin challenge, but in natural cases these changes varied within a wider range, and were more protracted and robust. Cows with puerperal metritis had more obvious catabolic changes in the early weeks of lactation, than their healthy counterparts. However, both mastitis and puerperal metritis failed to increase the circulating leptin level, showing that in cows the plasma leptin is not responsible for the anorexia associated with these inflammatory diseases.