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.

The energy imbalance related predisposition to mastitis was studied in group-fed postpartum dairy cows (n = 333) kept in 4 large-scale units and producing milk of low somatic cell count (SCC). Blood samples were taken on Days 1-3 after calving for assaying some metabolites and hormones related to the negative energy balance (NEB). If mastitis was diagnosed later, aseptic milk samples were taken to identify the pathogens. Considering pathogen types [contagious pathogens: Staphylococcus (S.) aureus, Gram-positive (GP) environmental pathogens, and Gram-negative (GN) environmental pathogens + mastitis with no detectable pathogens (NDP)] separately, stepwise logistic regression was used to analyse the relation between the potential prognostic value of hormones and metabolites and mastitis outbreak. Only the elevated (≥ 1.00 mmol/l) serum β-hydroxybutyrate (BHB) levels predisposed the cows to mastitis in the subsequent 4 weeks. This prognostic value of BHB was significant only in GN + NDP mastitis and in cases caused by GP environmental pathogens, but not in S. aureus mastitis (odds ratio: 5.333, 3.600 and 1.333, respectively).

ContentsIn two field trials the interrelation of (Gram-negative) mastitis with postpartum blood levels of certain hormons (insulin, IGF-1, cortisol, thyroxin and triiodothyronine) and metabolites (glucose, acetoacetate, @OH-butyrate, non-esterified fatty acid and total cholesterol, TCh) were studied. On days 1-3 and 28-35 also the ACTH stimulated adreno-cortical cortisol response was determined. The resumption of cyclic ovarian function was investigated by progesterone profiles based on milk samples collected 3 times a week for about I 1-12 weeks after calving. The early puerperal cases of Gram-negative (GN) mastitis were followed by a temporary decrease in plasma insulin and IGF-1 levels and also the TCh concentrations were lower than in healthy cows, but did not postpone the first postpartum ovulation. The (GN) mastitis in late puerperal phase delayed both the first postpartum ovulation and visable estrus. In cyclic cows forced luteolysis (in luteal phase) and disturbances in ovulatory mechanism (in follicular phase) were the consequences of this disease, although no increase in occurrence of ovarian cysts were observed.

The postpartum changes in plasma leptin levels of dairy cows ovulated within 35 days after calving were compared to of those with delayed onset of cyclicity in two experiments. The cows were sampled for leptin, insulin, IGF-1, thyroid hormones (T4, T3, rT3), Cortisol and also for some metabolites (glucose, NEFA, BHB and TCH) on day 1-3 after calving and again four times 7 days apart (Exp. 1), or in weeks 1, 2, 3, 5 and 10 postpartum (Exp. 2). In Exp. 1 also the standard low dose ACTH-induced Cortisol response and TRH-stimulated T4/T3 responses were determined on days 1-3 and 28-35. In cows of Exp. 1 the leptin level varied within a wide range with a mean of about 4 ng/ml HE in the first samples. Up to week 5 it remained unchanged in cows ovulated within day 35 but reduced in those with delayed onset of cyclicity, resulting in significant difference between the two group means.In cows of Exp. 2 the week 1 leptin levels were lower and less variable than that of Exp. 1. In weeks 2 and 3 a slightly increasing tendency of leptin pattern was seen in cows resuming their ovarian cyclicity within 35 days whereas in those with delayed onset of cyclicity the leptin level remained unchanged. Up to week 5 this tendency resulted in exactly the same leptin values as seen in Exp. 1 with significant differences between the group means in both of the weeks 5 and 10. It was concluded that the plasma leptin concentration in postpartum dairy cows may interfere with resumption of cyclic ovarian function, but its influence may be only permissive (e.g. a minimal concentration above a supposed threshold seems to be the prerequisite of the onset of cyclicity)

The involvement of adrenocortical and thyroid hormones in the pathogenesis of ketosis as well as the ovarian consequences of this metabolic disorder were studied in ≥2 parity cows (n=199) in 3 large scale dairy herds. To compare the plasma / serum concentrations of certain hormones [Cortisol, thyroxin (T4), triiodo-thyronine (T3), insulin, isulin-like growth factor-1 (IGF-l)J and metabolites [glucose (G), acetoacetic acid (ACAC), βOH-butyrate (BHB), non-esterified fatty acid (NEFA), trigliceride (TG), total cholesterol (TCh)J, and the activity of aspartate aminotransferase (AST), blood samples were taken 1 to 3 days after calving and again at 7-day intervals on four other occasions. The ACTH-challenged Cortisol responsiveness and the TRH-induced T4/T3 increase were determined between days 1 to 3 and again between days 28 to 35. The resumption of ovarian cyclicity was followed up by individual progesterone (P4) profiles based on milk samples taken 3 times a week for about 80 to 85 days postpartum. A concentration of 1 mmol/l of BHB level was estimated as a border between hyper- (>1 mmol/l) and normal ketonaemic (<1 mmol/l) conditions. 5 different ketone patterns were distinguished: (1) non-ketotic (n=98; normal ketonaemia in all samples), (2) early type ketosis (n=45; hyperketonemia was detected only in the first week after calving), (3) late type (lacta-tional) ketosis (n=11; after a normal ketonaemic period increasing hyperketonaemia was detected in the 5th, or in the 4th and 5th weeks), (4) temporary ketosis (n=ll; hyperketonaemia was detected for 1-2 weeks in the 2nd and 3rd or in the 3rd and 4th weeks); (5) long-lasting ketosis (n=34; hyperketonaemia had been detected since calving for 4 to 5 weeks or until death or emergency slaughtering). Simultaneously with the hyperketonaemic stage increased NEFA, ACAC, depressed TCh, glucose and decreased insulin, IGF-1, T4 and T3 concentrations were detected in almost all the cases. Obvious metabolic and endocrine alterations were found, however, only in long-lasting ketosis. The TRH-stimulated T4 and T3 responses remained almost unaffected proving intact thyroid function in early and late type as well as in temporary ketosis. Depressed thyroid response and delayed onset of cyclic ovarian function were detected only in cases of long-lasting ketosis. The cows characterized by lower than normal (< mean-SD of non-ketotic cows) ACTH-stimulated cortisol response on days 1-3 after calving showed poorer chancefor spontaneous recovery. There was a significant negative correlation between the IGF-1 level in the 1st week after calving and the duration of the postpartum acyclic period. In late type (lactational) ketosis the cessation of ovarian cyclicity was the most characteristic genital malfunction.