Effect of low-dose zearalenone exposure on luteal function, follicular activity and uterine oedema in cycling mares

The effect of 10-day zearalenone administration starting 10 days after ovulation was studied in 6 cycling trotter mares in the summer period. After an entire oestrous cycle (Cycle 1), mares were given 7 mg purified zearalenone per os daily (1 mg/ml in ethyl alcohol) beginning on Day 10 of Cycle 2. Toxin exposure was continued until the subsequent ovulation. Luteal function and follicular activity were monitored daily by rectal palpation, ultrasonography and blood sampling for progesterone. During toxin exposure, all animals were in good physical condition. The toxin had no effect on the length of the interovulatory intervals, luteal and follicular phases. It did not influence significantly the plasma progesterone profiles (logistic curve parameters A1 to A6), the follicular activity (growth rate, maximum size of the ovulatory follicles, maximum number and the time of first increase in the number of large follicles) and the uterine oedema. It is concluded that in cyclic mares the methods used in this study could not detect any adverse effect of zearalenone (administered at a low dose similar to natural exposure) on reproduction

Metabolic and endocrine profiles and reproductive parameters in dairy cows under grazing conditions: effect of polymorphisms in somatotropic axis genes

<p>Abstract</p> <p>Background</p> <p>The present study hypothesized that GH-AluI and IGF-I-SnabI polymorphisms do change the metabolic/endocrine profiles in Holstein cows during the transition period, which in turn are associated with productive and reproductive parameters.</p> <p>Methods</p> <p>Holstein cows (Farm 1, primiparous cows, n = 110, and Farm 2, multiparous cows, n = 76) under grazing conditions were selected and GH and IGF-I genotypes were determined. Blood samples for metabolic/endocrine determinations were taken during the transition period and early lactation in both farms. Data was analyzed by farm using a repeated measures analyses including GH and IGF-I genotypes, days and interactions as fixed effects, sire and cow as random effects and calving date as covariate.</p> <p>Results and Discussion</p> <p>Frequencies of GH and IGF-I alleles were L:0.84, V:0.16 and A:0.60, B:0.40, respectively. The GH genotype was not associated with productive or reproductive variables, but interaction with days affected FCM yield in multiparous (farm 2) cows (LL yielded more than LV cows) in early lactation. The GH genotype affected NEFA and IGF-I concentrations in farm 1 (LV had higher NEFA and lower IGF-I than LL cows) suggesting a better energy status of LL cows.</p> <p>There was no effect of IGF-I genotype on productive variables, but a trend was found for FCM in farm 2 (AB cows yielded more than AA cows). IGF-I genotype affected calving first service interval in farm 1, and the interaction with days tended to affect FCM yield (AB cows had a shorter interval and yielded more FCM than BB cows). IGF-I genotype affected BHB, NEFA, and insulin concentrations in farm 1: primiparous BB cows had lower NEFA and BHB and higher insulin concentrations. In farm 2, there was no effect of IGF-I genotype, but there was an interaction with days on IGF-I concentration, suggesting a greater uncoupling somatropic axis in AB and BB than AA cows, being in accordance with greater FCM yield in AB cows.</p> <p>Conclusion</p> <p>The GH and IGF-I genotypes had no substantial effect on productive parameters, although IGF-I genotype affected calving-first service interval in primiparous cows. Besides, these genotypes may modify the endocrine/metabolic profiles of the transition dairy cow under grazing conditions.</p

Role of adrenocortical system in occurrence of ketosis in high-yield dairy cows

From the very onset of lactation, the requirements of the mammary gland have an advantage over the requirements of other organic systems, even in the case of clinically exhibited ketosis. In hypoglycemic, ketotic cows, the mammary gland utilizes glucosis approximately in the same degree as the mammary gland of cows with normal glycemia. This indicates that the regulatory role of hormones can have primary importance in the earliest phase of lactation, when metabolic processes are on the very brink of a ketotic state. That is why it is believed that, in conditions of a great burdening of the metabolism, inadequate activity by the adrenocortical system presents one of the primary factors in the etiopathogenesis of ketosis in dairy cows. It is still an open issue whether hypof unction of the adrenal cortex is a direct cause of this disorder, or whether its activity is a consequence of insufficient stimulation by ACTH. In ketotic cows, average concentrations of cortisol have been established in ketotic cows, from 23.98 nmol/l in blood serum, and it is approximately the same as in healthy cows in the corresponding phase of lactation. However, the vast range of individual values largely makes it difficult to make a correct evaluation of the functional state of the adrenal cortex of ketotic cows. On the grounds of individual figures, in 26% diseased cows cortisol concentration in blood serum is from 1.38 to 16.55 nmol/l, in 37% it is from 16.55 to 27.59 nmol/l, and in 37 percent it is over 27.59 nmol/l. This indicates that cows with clinical symptoms of ketosis can be divided into those with low, medium, or high values of cortisol concentration in blood serum. Following the stimulation of the adrenal cortex with ACTH, the individual differences in serum cortisol concentration are considerably decreased. The ratio between the lowest and the highest values of cortisol concentration before the application of ACTH is 1:6, while it is only 1:1.5 four hours following application. After that, the values again take on the starting characteristics, and 24 hours after the application of ACTH they return to the starting values, and the ratio between the individual values is 1:8. It seems that the function of the adrenal cortex has been preserved in cows with clinical symptoms of ketosis and it is capable of reacting fully to stimulation with corticotropin. The cortisolemia values indicate, primarily, that there are big individual differences regarding the regulation of the degree of activity of the adrenal cortex, so that it is possible that, in the ketotic state, it is rather a case of uncoordinated activities of the adrenal cortex with the organism requirements imposed by the mammary gland, than that it is a matter of its hypofunction.

Development and validation of a radioimmunoassay for thyrotropin in cattle

In mammals, thyrotropin, or thyroid-stimulating hormone (TSH), assay is used for the diagnosis of primary hypothyroidism. Hypothyroidism is the most common type of thyroid disorder in cattle. The aim of this study was to develop and validate, under physiologic and pathologic conditions, a radioimmunoassay (RIA) for bovine TSH (bTSH). Double RIA was performed with purified bTSH and specific bovine antiserum. Laboratory validation included research of minimal detection limit, accuracy, and reproducibility. The physiologic validation included a thyrotropin-releasing hormone (TRH) challenge performed on euthyroid cows and a follow-up of bTSH concentration over a 24-hour period. Furthermore, bTSH concentration was assayed in a large population of healthy dairy and beef cows to define reference interval. The pathologic validation was made by assaying bTSH and thyroid hormones on healthy and goitrous newborn calves. The minimum detection limit (MDL) for bTSH assay was 1.3 microU/ml. The recovery was 101% to 106%. The intra- and interassay coefficients of variation (CVs) ranged from 5% to 11% and 11% to 15%, respectively. The RIA covered the whole range of physiologic bTSH values, as shown by bTSH values induced by TRH-challenge. A pulsatile secretion of bTSH was observed, accompanied by a diurnal variation with lower night values than day values. Reference intervals of bTSH ranged from 1.3 to 13.0 microU/ml for beef and dairy breeds. Finally, bTSH easily discriminated goitrous newborn calves from healthy ones, leading to the definition of a cutoff value of 35 microU/ml. The bTSH assay positively reacted to physiologic and pathologic conditions. The accuracy and precision of the RIA were satisfying

Effect of glucocorticoid treatment on fresh and deep frozen semen and on endocrine parameters in the stallion

International audienc

Effects of environmental temperature on thyroid hormones in the barn owl (Tyto alba)

The basic patterns of thyroid hormones [thyroxine (T4) and 3,3',5-triiodothyronine (T3)] and the T4 and T3 responses induced by thyrotropin releasing hormone (TRH) are reported in captive female barn owls (Tyto alba) during the non-breeding period. The main findings of the study, conducted on a total of 10 owls, are as follow: (1) The thyroid gland of barn owl can be stimulated by the classical TRH stimulation test. (2) T3 response was much more pronounced both under cold (around 10°C) and warm (around 20°C) conditions, whereas T4 response ranged so widely that we could not point out any significant change in it. (3) Basal T3 plasma level was significantly (p = 0.036) higher in birds exposed to cold temperature, and they responded to TRH treatment with a lower plasma T3 elevation than the birds kept in a warm chamber. This pattern, however, cannot be explained by increased food intake, but is in agreement with the fact that enhanced T3 level may account for higher avUCP mRNA expression, which results in higher heat production on the cell level. From the results it is concluded that altering T3 plasma level plays a significant role in cold-induced thermoregulation