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Browsing by Person "Claus, Rolf"

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Effects of immunological castration on the regulation of metabolism in boars
(2010) Bauer, Aneka; Claus, Rolf
Compared to surgical castrates, boars have a superior anabolic potential due to gonadal steroids, i.e. androgens and oestrogens. In consequence, they have an improved fattening performance and lean fat ratio in the carcass. However, most male piglets are surgically castrated without anaesthesia within the first week of life to avoid the unpleasant urine-like boar taint which is not acceptable to many consumers. Boar taint is mainly caused by androstenone which is synthesized in the testes together with the gonadal steroids. Skatole is another compound which contributes to the off odour. But this substance has a faecal smell and can be controlled by feeding strategies. Castration without anaesthesia is now regarded to cause acute pain and stress to the piglets, so that surgical castration is no longer tolerated due to animal welfare considerations. Different alternatives are discussed but it appears that active immunization against the gonadotropin releasing hormone (GnRH) is the most practicable alternative to surgical castration. It is based on application of a commercial antigen (Improvac®) two times at an interval of 4 weeks. The second vaccination then leads to a high antibody formation and to a blockade of GnRH and thus luteinizing hormone (LH). In turn, the testicular biosynthesis of anabolic hormones as well as androstenone is inhibited. Several studies found that immunized boars still had a better performance than surgical castrates. One explanation is that immunized boars maintain part of their anabolic potential before the second vaccination and thus the onset of antibody formation. Therefore, an exact time schedule for immunization is required to optimize the fattening period without risk of tainted carcasses at slaughter. Another explanation may be that high growth hormone (GH) concentrations are maintained in immunized boars at a boar specific level. In addition to low GH, barrows also have low concentrations of the anabolic insulin-like growth factor I (IGF-I). The present four studies were performed to investigate the hormonal and metabolic reactions before and after the second vaccination and to clarify why high GH concentrations are maintained. The cause for elevated GH levels in immunized boars could not be identified in the present studies. Nevertheless, results allow an exact timing of the vaccinations and thus an optimal use of the anabolic potential of immunized boars without the risk of tainted carcasses at slaughter. A further improvement of the fattening performance may be realized by feeding strategies and their influence on IGF-I.
Erhöhung der Butyratbildung durch Fütterung von Resistenter Stärke beim Schwein: Konsequenzen für die Mitose und Apoptoseregulation der Colonmucosa
(2004) Mentschel, Joachim; Claus, Rolf
Effects of nutrition on health status were examined in numerous studies for human as well as animal species. The interest is mainly focused on those components which are known to exert a beneficial effect on health. Specifically prae- and probiotic substances are discussed to decrease the use of antibiotics in animal nutrition. Moreover epidemiological studies suggest that a higher fiber content reduces the risk for carcinogenesis. The effects seem to be mediated by short chain fatty acids (SCFA). SCFA are major products of microbial fermentation of fiber in the hindgut and are essential for normal colonic function. Butyrate has been shown to have the most significant effects on colonic epithelium. For example colonic recovery after mucosal atrophy is improved due to butyrate supply. To examine the principles of the butyrate dependent effects, in numerous studies the effects of butyrate on mitosis, cell differentiation, and apoptosis of epithelial cells were determined. It has been shown that butyrate increases proliferation of normal cells both in vitro and in vivo, but decreases proliferation in neoplastic cells in vitro. In addition the incubation of adenoma and tumour cell lines with butyrate induced apoptosis whereas the absence of butyrate from the incubation medium triggered apoptosis in guinea pig colonic mucosa. This antiapoptotic function of butyrate has been confirmed in the bovine ruminal epithelium. The reasons for these contradicting results and the regulation of butyrate mediated apoptosis have not been examined so far. In the present study, therefore, the effects of butyrate on colonic epithelium were investigated by feeding resistant potato starch. Effects were verified by determining immunocytochemical parameters. The experiments were performed with 18 castrated male pigs (German Landrace x Pietrain). They were divided into the control group, the resistant starch group (RS), and the realimentation group (RE). At the end of the feeding period the pigs were killed and tissue samples for immunocytochemical studies were obtained. The controls were fed during the whole treatment period (19d) with a ration containing pregelatinized starch with a high ileal digestibility (14,13 MJME and 173,5g XP / kg DM). The RS group received the same diet for 10 days. Thereafter a ration with a lower ileal digestibility containing raw potato starch (11,28 MJME and 138,5g XP/ kg DM) was fed for 5 days in the adaptation period and for 19 d in the treatment period. The pigs of the RE group were fed identically, however after the control diet a starvation period of 3 days was included. Due to the lower energy content of resistant starch compared to pregelatinized starch the average energy and protein content differed between the two rations. To ensure an equal energy and protein supply the RS and RE group received a higher amount of the resistant starch ration. For later analytical determination of pH and SCFA, representative amounts of fresh faeces were collected every morning. They were stored deep frozen (-20°C). At the end of the experimental period pigs were killed and colonic tissue samples were taken for histological and immunocytochemical analysis. Feeding of resistant starch led to a 2.2-fold increase of butyrate in faeces. The morphological results revealed a significant increase of crypt depth (20%) in the resistant starch groups. This difference, however, can not be explained by a different mitotic rate which was nearly identical in both groups. Thus the morphological difference has to be attributed to the differences in the apoptotic activity which was significantly lower (40%) in the groups fed with resistant starch. This decrease of apoptosis was paralleled by an increase of the mucus area of goblet cells which were shown to contain EGF (epidermal growth factor). The difference was about 50%. The results indicate a link between apoptosis and EGF in the colonic epithelium. A reduction of apoptosis by 40% and no change of mitotic rate should lead to higher differences in epithelial development. The low increase of crypt depth can be explained by the shift of apoptosis along the crypt axis. In the group with high butyrate levels 39% of the apoptotic cells were located in the basal compartment of the crypts, in the control-group, however, only 17%. This higher incidence of apoptosis in the stem-cell compartment led to an decrease of average lifespan of colonocytes and consequently to the relative low increase of epithelium. The compartmental distribution of apoptosis is regulated by pro- and antiapoptotic members of the bcl-2 family. Compared to the control group the higher apoptotic rate in the basal compartment of the butyrate group was paralleled by the higher expression (3,5- fold) of the proapoptotic protein Bak. In addition the expression of the antiapoptotic protein Bcl-2 was increased in the luminal compartment by 55%. The results of the RS and RE group did not differ significantly. Due to the treatment-period of 19 days and the high turnover-rate in the colon the effects of starvation seem to be compensated. In conclusion the results demonstrate that under in vivo conditions in the pig butyrate is an inhibitor of apoptosis, but additional mechanisms ensure that the resulting proliferation is limited.
Geschlechtsspezifische Unterschiede in der Fötalentwicklung beim Schwein
(2007) Häußler, Susanne; Claus, Rolf
Basic mechanisms of sexual differentiation in higher mammals are well established. The development of the testes is controlled by genetic mechanisms and initiated by the Y-chromosome. Further differentiation of the ?Anlagen? is performed by the presence of testicular androgens but requires no specific signal in females (basic femaleness). Speculation exists during the fetal development of pigs, because androgens are also measurable in female fetuses. In addition, the male gonad is able to synthesize remarkably high levels of estrogens. The aim of the present study was to follow up concentrations of steroids in peripheral plasma throughout fetal development, starting with week 6, and in particular to analyze changes in testicular cell populations (spermatogonia, Leydig cells) and to correlate them with testicular androgens, estrogens, 19-nortestosterone and cortisol. The expression of steroid converting enzymes such as 11beta-HSD 2 and aromatase as well as receptors were determined by immunocytochemistry and quantitative PCR. Altogether each of the stages of gestation (weeks 6, 10, 13, and 15 of pregnancy) was represented by 4 sows, so that a total of 158 fetuses were collected. Testicular steroid synthesis (testosterone, estradiol) could be demonstrated as early as week 6, but was independant of gonadotropine. 19-nortestosterone, which is formed during estrogen synthesis, was detected in amniotic fluid using a new established enzymeimmunoassay in this study. Aromatase activity clearly correlated with a wave-like pattern of cell development. Therefore the activity was elevated both during an alternating rise of Leydig cells or spermatogonia mitosis. During the rise of spermatogonia development Leydig cells remained quiescent and during the Leydig cell mitosis spermatogonia remained inactive. An increased aromatase activity was observed both during the rise of spermatogonia and Leydig cell mitosis, and in consequence an elevated concentration of estradiol was found. But during an increased Leydig cell formation aromatase expression and thus estradiol synthesis was taken over by spermatogonia. It is therefore reasonable to resume that estrogens are important mitogenic signals as it was also found earlier in mature boars. The expression of glucocorticoid receptors by spermatogonia could be demonstrated for the first time in fetal pig testes. As also shown for other tissues, its likely role in testes is the differentiation of new cells. This important role also explains the expression of the enzyme 11beta-HSD 2 both by Leydig cells and spermatogonia. This enzyme is a well known fine-tuning mechanism which indicates cortisol and thus the ligand for the glucocorticoid receptor. Its expression in parallel to the rise of estrogens suggests a dependancy on estrogens. Investigating this was, however, not the topic of the present study. The demonstration of androgens both in blood plasma and amniotic fluid in female fetuses seems to contradict the principle of basic femaleness. It was shown however, that concentrations of testosterone in males increase up to 2.01 ng/ml plasma during the main period of sexual differentiation whereas female levels remain at 0.2 ng/ml so that it is simply the concentration which decides where the male differentiation does occur. It can not be ruled out, however, that low concentrations in female fetuses may have an effect on follicular differentiation, as was also demonstrated in mature sows. At the same time androgens could have a mitotic effect caused by insulin-like growth factors (IGF I + II). Thus the present investigation was able to clarify of several new mechanisms and basic data of fetal pig development. Further confirmation of the mechanisms suspected in this study may be served by an aromatase inhibitor.
Der Glucocorticoidrezeptor des Schweins: Herstellung und Charakterisierung eines polyklonalen Antiserums, sowie Studien zur Verteilung des GCR im Intestinaltrakt von Ebern und Kastraten
(2002) Gutscher, Monika; Claus, Rolf
Glucocorticoids are well known to be essential for many physiological and developmental processes. Such functions include their effects on carbohydrate and protein metabolism and their regulatory influences on the immune system. In cell regulation they play a dose-dependent key role for differentiation and apoptosis. In rapidly renewing tissues the stringent control of these mechanisms is central to the maintenance of tissue homeostasis. ln the gastrointestinal tract both the adaption to changing nutrients and the presentation with a vast array of different types of antigens, including potential pathogens and harmless dietary antigens requires a granular regulation of cell proliferation, differentiation and cell death. In the pig, the differences in the turn-over rate for instance between skeletal muscle and the gut tissue could be attributed to different GCR concentrations respectively. This explains the tissue specific sensitivty on circulating corticoids. Thus studies on GCR distribution contributes to the clarification of the role of glucocorticoids in the regulation of these mechanisms in the intestinal tract. In the pig, so far receptor detection has been performed by radio ligand binding assays, which only measures steroid unoccupied non-activated receptors in the cytoplasm. Selective GCR antibodies react with both occupied and unoccupied GCR. In addition, antibodies enable celltype specific detection of the GCR in complex tissues by immunocytochemistry. The aim of this investigation was the production of porcine GCR-specific polyclonal antibodies by detailed analysis of the cDNA sequence of the GCR and the recombinant expression of a suitable antigen fragment. A fragment with 2.1 kb of the GCR cDNA (gcr2.1) was sequenced. Based on Blast sequence analysis a GCR antigen fragment for recombinant expression was selected from the modulatory region (GCRmr) and cloned in a T7-expression system as a His-tag fusion protein. After affinity chromatographic und preparative purification The anti-pGCR-antibodies bind the pGCRmr antigen with high affinity, as well as the denatured receptor in western blot analysis. In additon, immunoprecipitation assays demonstrated that cytosolic GCR is recognized regardless of whether it is unoccuppied or occuppied with dexamethasone. Thus, the antiserum is able to bind the native GCR both in its inactivated form as a multiprotein complex in association with HSP90 and in its activated form with shed HSP 90. Our investigations with immunoprecipitation assays support the applicability of the anti-pGCR antiserum in immunohistochemistry. The characterized antibodies were implemented in immunohistochemy for studies of distribution and localization of the GCR in the small bowl and colon of boars and barrows. The intracellular distribution of the GCR was examined by western blot assays. Immunohistochemical studies showed an increased number of immunostained GCR in the colon compared with the small intestine, as has been shown earlier with ligand-binding assays. 32,9 % and 14,5 % of the cells of the lamina propria were GCR immunoreactive in the small intestine of barrows and boars. In the colon 49,3 % and 43,3 % showed immunostaining. Epithelial cells showed a reversed pattern compared to the lamina propria in both groups. The number of GCR immunoreactive cells in barrows and boars decreased from 9,6 % and 9 % in the small intestine to 5,4 and 5,6 % in the colon, respectively. Comparison of both groups ? barrows and boars - revealed significant differences in the number of GCR immunoreactive cells in the lamina propria of the small bowl. Boars showed a decreased GCR expression of 10 % in the duodenum and 30 % in the jejunum. The number of GCR immuostained colonic cells amounts to 36,9 % in the colon ascendens and 49,2% in the colon descendens of boars and 47,5 % and 51 % in barrows. Studies of the subcellular localization by western blot analysis of cytosolplasmic and nuclear proteins demonstrated that in both groups in the ileum a higher amount of GCR was translocated into the nucleus. In the colon the number of cytoplasmic GCR was higher. The different subcellular GCR distribution in the two segments of the intestine can be explained by the increased expression of 11â-hydroxysteroid dehydrogenase 2 in the colon. 11â-HSD 2 inactivates cortisol and thus inhibits receptor activation and thereby translocation to the nucleus.
Die Regulation der Futteraufnahme beim Schwein - Untersuchung der Wirkungen eines Serotonin Noradrenalin Wiederaufnahmehemmers (Sibutramin) und eines MCH-R1 Antagonisten (Compound B4)
(2007) Sommer, Torsten; Claus, Rolf
The regulation of food- and feed intake is a highly topical investigative area in animal husbandry as well as in human medicine. Here the focus of medicine is primarily on the reduction of food intake and at the same time change of the metabolism to increased energy expenditure in order to counteract the rising number of adiposity and metabolic syndrome. Therefore, substances from pharmacological research are known which act in different nuclei of the hypothalamus and control food intake and energy expenditure. In the present study two of these new substances were examined with regards to their impact on pigs. The results lead to a more detailed understanding of the corresponding mechanisms in pigs, one of the most important animals used in agriculture. In addition, the pig is also a suitable model for human pharmacological research, as it equals the human physiological regulation more than the rat, which is the most common animal model. Study work flow: Two different regulative substances were examined, on the one hand a serotonin noradrenalin reuptake inhibitor (Sibutramine) and on the other hand, a melanin concentrating hormone receptor antagonist (MCH-R1 antagonist; Compound B4). For the evaluation of the effectiveness the following factors were measured; feed intake, water consumption, weight gain, feed conversion rate and the development of body fat content. The changes caused in the regulation of the metabolism were evaluated by anabolic (Growth hormone and IGF-I) and catabolic (cortisol and aldosterone) hormones. In addition, thyroid hormones and urea in the blood plasma were measured as a parameter of protein turnover. The study was divided in three trials, each of them taking six weeks. During the first trial sibutramine was given per os to three animals and three animals were kept as control. During the second trial sibutramine was given intravenously to two animals and two animals were kept as control. During the third trial the MCH-R1 antagonist, Compound B4, was given per os to six animals. The results are described in the following sections. Results of the sibutramine application: The pharmacological effectiveness of sibutramine is mainly explained through its metabolites (desmethyl sibutramine and didesmethyl sibutramine). It was found that for the per os intake of 20 mg/kg LW sibutramine, as well as sibutramine as the first metabolite desmethyl-sibutramine, a lower concentration in the blood plasma existed compared to the intravenous application. Whereas concentration of the second metabolite didesmethyl-sibutramine was higher for per os application than for intravenous application. Since the effectiveness of sibutramine is mainly based on its second metabolite didesmethyl-sibutramine, the way of application was crucial for its effectiveness. This means that the intravenous application was ineffective. After per os application feed intake was significantly reduced, also dependent on the dose applied, but did not lead to a reduced weight gain of the animals. Further, no impact was found on the feed conversion ratio. In contrast, the treatment with sibutramine per os led to significantly increased water consumption. The application of sibutramine had no impact on the growth hormone secretion. However, IGF-1 concentration was increased while feed intake was decreased. The cortisol concentration in blood plasma was not impacted by any treatment. Results of the application of the MCH-R1 antagonist (Compound B4): The application of the antagonist led to a significant reduction of feed intake, dependent on the dose applied. The means derived for daily weight gain show considerable individual differences per animal, hence the reduction of daily weight gain overall was not significant. Further, changes in water consumption were also detected in this trial. However, it could not be clarified if this was caused by the application of the antagonist or the reduced feed intake. Generally, the application of Compound B4 tends to result in energy saving mechanisms, which have an impact on metabolic active hormones. IGF-1 for example, was slightly lower in the control phase. Neither sibutramine nor the MCH-R1 antagonist Compound B4 had any impact on the concentration of thyroid hormones or cortisol. Conclusions: The studies have shown that the MCH-R1 antagonist leads to a significant reduction of feed intake in pigs, whereas the metabolic active hormones, and therefore the energy expenditure, do not seem to be impacted at all. In addition, it was proven that the pig is a useful animal model for such human pharmacological investigations. However, the large amount of substances required can be seen as disadvantageous and as a limiting factor in the investigation of new agents with an initially small amount of substance synthesis.
Steuerungsmechanismen der Spermatogenese beim Eber: Auswirkungen einer GnRH-Immunisierung und anschließender Estradiolinfusion
(2005) Wagner, Anna; Claus, Rolf
Whereas the regulation of spermatogenesis is well known in various species, specific differences, however, exist for the boar, which require species-specific investigation. High concentrations of estrogens are synthesized in the boar testis. It is known, that they play a synergistic role for male behaviour and function of accessory sex glands. Additionally, estrogens in the ejaculate reach the female genital tract and contribute to sperm transport and ovulation in the sow. A possible involvement of estrogens in spermatogenesis, however, was not investigated so far. Similarly, high concentrations of glucocorticoids occur in the tubuli of mature boars. Their regulatory function in spermatogenesis so far is unknown. For clarification, boars were actively immunized against GnRH. GnRH stimulates gonadotropin-release from the pituitary. The evaluation of hormone concentrations in blood plasma after GnRH immunization showed unexpectedly, that the gonadotropin FSH is not influenced, whereas LH- and in consequence steroid- (androgen and estrogen) concentrations were abolished. This offers the possiblity to characterize the selecitve function of estrogens in the presence of FSH. Three groups were evaluated: intact boars (n=5), immunized boars (n=5), 17ß-estradiol infused, immunized boars (n=6). All animals were fitted with indwelling cephalic vein catheters on both sides. One of them was reserved for infusion, the other one for uncontaminated blood sampling. All animals were infused with physiological saline over 7 weeks. For the 17ßEstradiol infused, immunized boars, a defined concentration of estradiol was added to the solution. Blood samples were collected over the whole 7-week period for LH, FSH, testosterone and estradiol. Blood samples were later analysed by established radioimmunological procedures. At the end of the 7-week period, all animals were killed. Tissue samples were fixed for histological examination. Morphological criteria included e.g. tubular diameter, seminiferous epithelial height and number of Leydig cells. Imunocytochemical evaluation was performed for mitosis (Ki-67), apoptosis (TUNEL) and the glucocorticoid receptor. The number of germ cell in the tubuli was reduced by 60% in immunized boars compared to the intact controls. These changes were explained by a more pronounced expression of the glucocorticoid receptor in spermatogonia, followed by the appearance of apoptosis in spermatogonia and primary spermatocytes. In consequence these findings demonstrate for the first time an involvment of glucocorticoids in the quantitative regulation of spermatogenesis. They counteract tubular mitosis by reducing the number of germ cells by apoptosis. In the 17ßestradiol infused group of immunized boars, the infusion led to the restoration of physiological estradiol concentrations (230 pg/ml) in peripheral blood plasma. As expected, androgen concentrations were minimal, so that the specific role of estrogens for spermatogenesis could be clarified. Data from the histological evaluation showed, that the expression of the estrogen receptor alpha occured in spermatogonia, selectively in the mitotic active stage of the seminiferous epithelial cycle leading to a 41-50% rise of germ cell numbers compared to immunized boars. The apoptotic rate in the tubuli of the estradiol infused boars however was not changed compared to immunized boars, so that physiological sperm numbers as they are characteristic for intact boars, were not reached. This study shows for the first time that both glucocorticoids and estrogens play an essential role for spermatogenesis in the boar. They are involved in the regulation of sperm yield by influencing the mitosis-apoptosis equilibrium in the tubuli of boars.
Versuche zur Verbesserung der sensorischen Fleischqualität beim Schwein durch nutritive Hemmung der Skatolbildung
(2006) Lösel, Dorothea; Claus, Rolf
Skatole is known to occur in pork carcasses. Due to its pronounced faecal odour, it may have an adverse effect on sensorial quality of pork. Skatole has been associated with boar taint, but is also formed in the large intestine of barrows and gilts by bacterial degradation of tryptophan. As apoptotic cells from the gut mucosa are the main source of tryptophan, skatole formation is partly linked to the degree of cell renewal in the gut. A part of microbially formed skatole is absorbed and stored in adipose tissue due to its lipophilic properties. In earlier studies it has been shown that intestinal butyrate formation increased by feeding resistant potato starch. This short-chain fatty acid reduced the apoptotic activity in the gut mucosa and thus decreased skatole formation and tissue accumulation. Therefore, it was the aim of the present study to investigate whether this method is applicable to improve sensorial quality of pork under routine fattening conditions. In the first experiment the amount of potato starch required for sufficient reduction of skatole was determined. Four groups of pigs received diets containing different amounts of potato starch (0 % as a control, 20 %, 30 %, 40 %) for 2-3 weeks prior to slaughter. Skatole concentrations in gut content (proximal and distal colon, rectum) and adipose tissue (flare fat and ventral fat) were determined by High Performace Liquid Chromatography. An amount of 30 % in the diet reduced skatole concentrations in gut content and adipose tissue compared to the control. The reduction was 98 % in the proximal colon, 93 % in the distal colon and 89 % in the rectum. Skatole concentrations in flare fat decreased by 84 %. Feeding a higher amount of potato starch (40 %) did not result in a significant further reduction. Therefore, in the following experiment (consisting of two replicates) diets of treatment groups contained 30 % of potato starch. In each replicate, 80 Baden-Württemberg Hybrids (barrows and gilts) were fed the diets during the whole fattening period. The control groups received a conventional diet based on grain and soya and a diet with a proportion of 30 % gelatinized starch in replicate 1 and 2, respectively. Skatole concentrations were determined in gut content (proximal and distal colon, rectum), blood plasma and adipose tissue (flare fat, ventral fat and back fat). Apoptosis in the colonic mucosa was determined cytochemically. From each replicate cutlets from 12 control pigs and 12 potato starch pigs were used for sensorial evaluation. The panellists evaluated samples for aroma of meat juice, and aroma and taste of meat according to a 5-point scale. The attributes were from 1 (very unpleasant) to 5 (very pleasant). A trend towards reduced apoptosis was demonstrated in the upper crypt compartment in the proximal colon. Intestinal skatole formation decreased from 50-60 µg/g dry matter to values around the lower limit of detection (0.4 µg/g). Thus, less skatole was absorbed and the mean concentrations in blood plasma were reduced by 45-65 %. In adipose tissue, concentrations in the potato starch group decreased by 57-90 % compared to the controls. Therefore, the variation of concentrations was reduced, so that 90 % of the potato starch pigs had values below 20 ng/g. Concentrations in gut content, blood plasma and adipose tissue were significantly correlated. In replicate 1, sensorial evaluation showed that cutlets containing between 0 and 2.78 ng/g skatole in fat had better ratings for aroma of meat juice and meat than samples with mean (up to 28 ng/g) or high (up to 78 ng/g) skatole concentrations. Also, the overall impression was significantly improved. In replicate 2, there was still a tendency to these differences. In conclusion, this study shows that the reduction of intestinal skatole formation by feeding resistant starch can improve the aroma of pork. For routine application, it would be sufficient to feed the potato starch diet for only a few days prior to slaughter.
Wachstum und Wachstumsregulation beim Schwein
(1995) Weiler, Ulrike; Claus, Rolf
The endocrine regulation of growth was studied in wild and domestic pigs by systematic measurements of growth hormone (GH), IGF-I (Insulin-like growth factor-I), insulin and steroid hormones. In some of the studies measurements of osteocalcin were included to monitor the anabolic activity of osteoblasts under different physiological situations. The following results were obtained. Age dependent changes in the secretion of GH- und IGF-I were studied in growing boars, barrows and gilts and compared to growth parameters. IGF-I reflected age dependent changes in the growth potential and were closely correlated with daily gain and protein accretion. Osteocalcin concentrations were always correlated to IGF-I, the age dependent decrease, however, was more pronounced for osteocalcin than for IGF-I, reflecting the allometric predominance of skeletal growth in very young pigs. Osteocalcin concentrations were always correlated to IGF-I, the age dependent decrease was more pronounced for osteocalcin than for IGF-I, reflecting the allometric predominance of bone growth in very young pigs. Additionally a clear rhythm of IGF-I secretion was obvious with a period length of two to three weeks. This rhythm was similarly found for cortisol secretion and peripheral osteocalcin and might be related to allometric growth phenomena, as described for skeletal growth in other species. Regulation of GH-secretion includes interactions with hormones involved in the regulation of reproduction. At the pituitary level such interactions were demonstrated for Gn-RH and GH-RH. Gonadal steroids directly influence the release of GH and IGF-I secretion. The analysis of physiological situations as well as application studies revealed that testosterone had only a minor effect on both hormones. In contrast, low concentrations of estradiol clearly stimulated GH- and IGF-I secretion as well. Further increasing estradiol concentrations were still stimulatory for IGF-I but inhibited GH-secretion. Progesterone tended to lower both, GH and IGF-I secretion. Additionally Large White, Meishan and European wild boar were studied for differences in growth performance and the endocrine regulation during the first year of life. The studies revealed, that the high growth potential of LW is related both, to high levels of anabolic IGF-I and concomitantly low levels of catabolic cortisol. In Meishan and wild boars cortisol levels were high, but in Meishan boars additionally high concentrations of gonadal steroids were measured, which may explain the higher growth rate in MS when compared to wild boars. IGF-I concentrations were even higher in wild boars than in LW. Thus it is assumed that selection for growth potential led to a concomitant change in the level of catabolic glucocorticoids. The influence of the season and photoperiod on endocrine parameter, food intake and growth was investigated in wild and domestic boars. A seasonal influence on IFG-I secretion was obvious in wild and LW boars, but not in Meishan boars. It was further proven by the application of a reverse light programme that the pattern is mainly due to the influence of the photoperiod. In the wild boar three distinct metabolic periods were obvious, which were also found in domestic pigs, but less pronounced. In addition to the photoperiod food intake and food composition modulate GH and IGF-I secretion in the pig. Several experiments revealed, that IGF-I secretion is predominantly influenced by the energy supply and only to a lower extend by protein and tryptophane content of the ration.

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