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Insulin-like growth factors (IGF) are important mediators of growth, lactation, reproduction, and health. Considerable information on their role in ruminant animals has been learned in the past several years, but the precise mechanisms of their action are not known. The exact biological response of target cells is undoubtedly determined by the developmental state of the cell and synergism with other growth factors. Overall, somatomedins and their binding proteins seem to be major links between cellular developmental processes and nutrient supply. The mechanism by which nutrients control biological actions of somatomedins is not known but clearly involves the synthesis of IGF, as well as their binding proteins and receptors. In ruminants, severe feed restriction decreases circulating concentrations of IGF-I, whereas subtle alterations typical of those that occur in production systems have minimal effect. However, the responses of IGF to somatotropin are affected by modest alterations in nutritional status, including differences in nutritional status that are typically encountered in animal production systems. 相似文献
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Insulin has been shown to have an impact on both prenatal and postnatal growth. Specific mechanisms of insulin action on adipose cell function and lipid storage are well defined. Insulin probably acts in concert with other anabolic factors (i.e., growth hormone and somatomedins) to stimulate muscle protein anabolism and suppress protein catabolism (Figure 2). Insulin also plays a role in energy balance regulation by the hypothalamus, however exact mechanisms of effects on brain metabolism have not been clearly identified. 相似文献
4.
G.S.G. Spencer 《Livestock Production Science》1985,12(1):31-46
Growth is a complex, highly integrated process. It involves a host of interactions between nutrients, environment, genotype, many very different hormones and the receptors for these hormones in different tissues. The ultimate hormones for growth are the growth hormone-dependent somatomedins. These are purely anabolic agents that stimulate increases in both the number of cells (hyperplasia) and their size (hypertrophy). Although the growth hormone-somatomedins axis is the central route for growth control, many other hormones influence their effectiveness. Growth hormone — despite being essential for somatomedin production — is also lipolytic and diabetogenic. It thus has both anabolic and catabolic actions. Insulin has some direct effects on hypertrophy, but also controls the ability of growth hormone to stimulate somatomedin production by regulating the growth hormone receptors involved in stimulating production of somatomedins. Similarly, thyroid hormones regulate somatomedin receptors. Just as insulin has direct and indirect anabolic actions, so glucocorticoids have catabolic actions of both a direct and indirect nature. Oestrogens also have direct and indirect effects, but these are antagonistic; on the one hand directly stimulating cell growth by hypertrophy and on the other inhibiting somatomedins production.Clearly there has to be a controlling mechanism which allows a change in the hormonal balance towards anabolism for growth to be stimulated. Identifying and altering this factor(s) will be the key to increasing growth by physiological hormonal manipulation. A major candidate for this role of central growth controller is somatostatin, which inhibits the release of growth hormone, insulin and thyroid hormones, and also acts as a regulator connecting nutrient entry and metabolism. Recent experiments which show that immunization against somatostatin increases growth and food conversion efficiency support this hypothesis. 相似文献
5.
Antimicrobials given in subtherapeutic levels in feed are credited with having contributed to lower cost of meat, milk and eggs. The practice often is associated with the acquisition of resistant enteric flora by the involved animals, and this may in turn contribute to the human reservoir of antimicrobial resistant coliforms and salmonellae. Associated farm workers may transiently acquire resistant flora and on rare occasions develop salmonellosis. Although irrefutable evidence of growth promotant properties of antibiotics in animal feed was provided 30 to 40 years ago, additional studies on mechanisms of the effect are presently needed. It may be possible to identify factors effective in promoting growth without deleterious effects on flora. A national surveillance programme of antimicrobial utilisation (both subtherapeutic and therapeutic) among food producing animals should be established. Molecular epidemiologic research efforts will need to be undertaken to establish whether genetic information of animal origin importantly contributes to the human environmental pool of antimicrobial resistance. In the meantime, it does not appear that the use of drugs as feed additives, while allowing their unrestricted use for therapy in both animals and persons, would favorably influence the problems of antimicrobial resistance of salmonellosis in human populations. 相似文献
6.
Stimulation of swine growth by porcine growth hormone 总被引：7，自引：0，他引：7
Highly purified porcine growth hormone (pGH; USDA-B1) was administered by im injection (22 micrograms X kg body weight-1 X d-1) to rapidly growing Yorkshire barrows for 30 d. Growth hormone significantly increased growth rate (10%), feed efficiency (4%), cartilage growth and muscle mass. However, pGH did not affect carcass adipose tissue mass. Intramuscular lipid content of the longissimus was increased 50% by pGH administration. Plasma pGH concentration was elevated (7- to 11-fold) for 3 to 5 h post-injection. Chronic administration of pGH depressed pituitary GH content and concentration approximately 45%. No GH antibodies were detected in the plasma of GH-treated swine. Plasma somatomedin-C concentration was increased 55% by GH treatment 3 h post-injection. Plasma glucose and insulin concentrations were both significantly increased in GH-treated swine, suggesting that the animals had developed a state of insulin resistance. Plasma-free fatty acid concentration tended to be higher in GH-treated animals. Treatment of swine with pGH significantly decreased plasma blood urea nitrogen. Assessment of animal health during the trial and postmortem indicated that pGH administration did not have any adverse effects. In summary, treatment of young, rapidly growing swine with pGH stimulated growth performance without affecting animal health or inducing the production of GH antibodies. 相似文献
7.
John R. Walton 《Veterinary research communications》1983,7(1):1-7
The term growth promotion applies to the increase in performance or productivity achieved in food producing animals following the addition to their diet of feed antibiotics or growth promoters. Numerous methods are available for the different animal species. Steroidal substances are widely used in cattle whilst in pigs and poultry a wide range of substances are used to influence the gastro-intestinal microflora and thereby bring about a cost-effective improvement in productivity. Although certain antibiotics have been used for growth promotion for over three decades they are still highly effective and appear not to have reduced the value of other widely used antibiotics for the treatment of disease. The mechanisms by which growth promotion is produced are only poorly understood but it is now generally accepted that any improvement in performance is directly related to a variety of direct effects on the gut microbial flora and associated indirect effects on intestinal tissues. The direct effects include inhibition of bacterial growth, interference with bacterial cell wall development, induction of filament formation and interference with the metabolism of intestinal bacteria. The indirect effects include a reduction in the thickness of the intestinal mucosal layer and a decrease in the production of certain mucosal cell enzymes. Other effects seen in the gut of growth promoted animals and birds include a decrease in the prevalence of antibiotic resistance plasmids and a reduced frequency of plasmid transfer in enteric coliforms. It is clear from available data that conventional animals are depressed in performance and this depression can be alleviated by the administration of growth promoting agents in the diet of these animals. The lifting of this depression results in an improvement in performance especially daily live weight gain and feed conversion efficiency. 相似文献
8.
Summary Antimicrobials given in subtherapeutic levels in feed are credited with having contributed to lower cost of meat, milk and eggs. The practice often is associated with the acquisition of resistant enteric flora by the involved animals, and this may in turn contribute to the human reservoir of antimicrobial resistant coliforms and salmonellae. Associated farm workers may transiently acquire resistant flora and on rare occasions develop salmonellosis. Although irrefutable evidence of growth promotant properties of antibiotics in animal feed was provided 30 to 40 years ago, additional studies on mechanisms of the effect are presently needed. It may be possible to identify factors effective in promoting growth without deleterious effects on flora. A national surveillance programme of antimicrobial utilisation (both subtherapeutic and therapeutic) among food producing animals should be established. Molecular epidemiologic research efforts will need to be undertaken to establish whether genetic information of animal origin importantly contributes to the human environmental pool of antimicrobial resistance. In the meantime, it does not appear that the use of drugs as feed additives, while allowing their unrestricted use for therapy in both animals and persons, wouldfavorably influence the problems of antimicrobial resistance of salmonellosis in human populations. 相似文献
9.
Gareis M 《DTW. Deutsche tier?rztliche Wochenschrift》2002,109(8):345-348
By the term "meat" the consumer understands muscle meat, that is skeletal muscle. The german regulations, the "Leits?tze für Fleisch und Fleischerzeugnisse" as well as the Codex Alimentarius define meat in a much broader sense to include all edible parts of slaughtered or shot warm-blooded animals (skeletal muscles, fat, heart, gut, liver etc). Therefore, a differentiated procedure is required when the risk of BSE transmission by meat has to be estimated. This must be based on knowledge of occurrence, amount, and persistence of BSE agents in the organs of animals. The risk evaluation has to include further factors: differences between animal species, age of the animal at the time of slaughter, the possibility of contamination during the slaughtering and cutting process, and--as far as meat products are concerned--the processing technology. To date there are no indications for the existence of transmissible spongiform encephalopathy in pigs, poultry and fish, even though BSE has been transmitted to pigs experimentally by intracranial administration. Muscle meat of these species can be considered safe. Muscle meat of experimentally infected cattle in the preclinical stage and even of animals with clinically manifest BSE has not shown infectivity in homologous and autologous bioassays performed so far. This finding justifies the assumption that the risk of BSE exposure by the consumption of beef can be classified as extremely low. Nevertheless, the absence of a proof of infectivity can at present not be equated with absence of BSE agents. This is because of the limits of sensitivity of the bioassays and because muscle meat does contain non-muscle tissue such as connective tissue collagen, nerve and lymph tissue and blood vessels. 相似文献
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《The Professional Animal Scientist》2002,18(2):107-111
Meat tenderness is a major factor affecting the consumers’ assessment of meat quality. Collagen is an abundant connective tissue protein and is a contributing factor to variation in meat tenderness and texture. It is found in three specific regions in muscle and in various forms and types. Collagen molecules are bound together through intermolecular crosslinks that help provide structure and strength. These crosslinks are initially reducible, but over time are replaced by mature, thermally stable, and less soluble crosslinks. These mature crosslinks, rather than the total amount of collagen, are the key factors in collagen-related toughness. The proportion of mature to reducible crosslinks increases with age, resulting in older animals that often have less tender meat than younger animals. Collagen crosslinks are also affected by growth rate, nutrition, and genetics. Collagen plays major roles in cooked meat as well. As collagen fibrils are heated during cooking, they shrink, resulting in a fluid loss and less tender meat. They also act to hold muscle fibers together after shrinkage. Post-mortem degradation of collagen and the use of collagenases appear to play a role in providing the desired tenderness and texture by altering the connective tissue structure. Collagen is very important in maintaining acceptable texture; however, high amounts of crosslinks can greatly decrease tenderness and consumer acceptability. 相似文献
12.
Stem cell niche plays a critical role in regulating the behavior and function of adult stem cells that underlie tissue growth, maintenance, and regeneration. In the skeletal muscle, stem cells, called satellite cells, contribute to postnatal muscle growth and hypertrophy, and thus, meat production in agricultural animals. Satellite cells are located adjacent to mature muscle fibers underneath a sheath of basal lamina. Microenvironmental signals from extracellular matrix mediated by the basal lamina and from the host myofiber both impinge on satellite cells to regulate their activity. Furthermore, several types of muscle interstitial cells, including intramuscular preadipocytes and connective tissue fibroblasts, have recently been shown to interact with satellite cells and actively regulate the growth and regeneration of postnatal skeletal muscles. From this regard, interstitial adipogenic cells are not only important for marbling and meat quality, but also represent an additional cellular component of the satellite cell niche. At the molecular level, these interstitial cells may interact with satellite cells through cell surface ligands, such as delta-like 1 homolog (Dlk1) protein whose overexpression is thought to be responsible for muscle hypertrophy in callipyge sheep. In fact, extracellular Dlk1 protein has been shown to promote the myogenic differentiation of satellite cells. Understanding the cellular and molecular mechanisms within the stem cell niche that regulate satellite cell differentiation and maintain muscle homeostasis may lead to promising approaches to optimizing muscle growth and composition, thus improving meat production and quality. 相似文献
13.
M. Schwerin J. Voigt J. Wegner Ch. Kühn K. Ender H. Hagemeister 《Journal of animal physiology and animal nutrition》1999,81(3):113-123
Among other factors the nutrient utilization of a cow is influenced by its individual physiological and genetic predisposition. There are large differences within cows in the manner of partition of the nutrients that may affect the size and activity of the individual organs and the whole body composition. High genetic merit dairy cows have a higher potential rate of protein excretion than medium genetic merit dairy cows even when energy and protein intake are equal. Medium genetic merit dairy cows show higher potential rates of protein and fat deposition of the body. This phenomenon was partly explained by the regulatory functions of the hormone insulin (see Brockman and Laarveld 1986; Broucek et al. 1991; Wylie et al. 1998). Additionally, it is widely considered that the somatotropic axis [growth hormone, growth hormone releasing factor and insulin-like growth factor I (IGF-I)], could be involved, as one of the key control and balance mechanisms which regulate the partition of nutrients (Breier and Sauerwein 1995; Schams 1995; Knight 1997). Several studies have provided insights into the physiological action of these and further hormones, transport proteins and enzymes, e.g. the erythrocyte-type glucose transporter, the insulin-responsive glucose transporter or the glycerol-3-phosphate dehydrogenase, and indicate that these molecules may affect nutrient repartitioning and utilization as well as milk yield, growth and fat accumulation (Mathews et al. 1988; Bauman and Vernon 1993; Burton et al. 1994; Girard et al. 1994; Binelli et al. 1995; Zhao et al. 1996; Abe et al. 1997). However, the mechanisms of regulation of most of these processes are insufficiently known. This paper presents a comparison of mRNA patterns of tissues potentially associated with protein and energy turnover in lactating cows of different metabolic types. The technique of differential display of messenger RNA species originally described by Liang and Pardee (1992), has already been applied as a powerful tool for cloning genes that are differentially expressed in various tissues or under altered conditions in the same tissue (e.g. Liang et al. 1993; Aiello et al. 1994; Li et al. 1994; Nishio et al. 1994). This method was applied to characterize the expression patterns in 12 tissues of three cows with divergent metabolic types (milk type, meat/milk type, and meat type) by the display of differentially and identically expressed cDNA bands. The aims of this exploratory study were first to indicate which of the 12 tissues analysed are mainly involved in trait differentiation according to their differentially displayed mRNA patterns. Secondly, the results of this study represent the prerequisite for the identification of tissue-specific expressed sequence tags in general, and individual or type-dependent differentially expressed sequence tags in particular. 相似文献
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As it is for mammalian species, growth hormone (GH) is indispensable for normal growth and development of avian species. In contrast to mammals, exogenous GH administration has little, if any, potential for improving the growth rate and feed efficiency of rapidly growing broilers; it is more likely to do so in older birds. This is at least partly because of age-related changes in tissue GH-binding activity and GH-receptor mRNA expression. The effects of GH on lipid deposition depends on the age of the bird and pattern of GH administration. Pulsatile, but not continuous, GH administration to older broilers seems to reduce fat deposition. As in rats, the bioactivity of GH might also depend on the pulse-induced cyclicity in GH receptors and GH-binding proteins. In chickens, GH is also a very potent lipolytic hormone, but seems to have no diabetogenic effect, which is reported in mammalian species. Both insulin-like growth factors have apparently no growth-promoting effects in normal growing broilers, but seem to have opposite effects on fat deposition. In contrast to GH, both insulin-like growth factors have a marked hypoglycemic effect. Whether all these effects are direct effects, or are mediated by secondary mechanisms, awaits further investigations. 相似文献
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S R Gooneratne R K Chaplin A M Trent D A Christensen 《The British veterinary journal》1989,145(1):62-72
The copper (Cu), zinc (Zn), and iron (Fe) excreted daily in the bile of three sheep were estimated at 0.20, 0.10 and 0.36 mg respectively. Intravenous administration of tetrathiomolybdate (TM) increased bile Cu excretion and reduced liver Cu concentration. Tetrathiomolybdate had no significant effect on the excretion of Zn and Fe. These findings indicate that at least one of the mechanisms by which TM induces hypocuprosis is by increasing biliary Cu excretion. Hence it has a possible use in the treatment of Cu storage diseases in man and animals. 相似文献
16.
M. Sohaib F. M. Anjum M. Nasir F. Saeed M. S. Arshad S. Hussain 《Journal of animal physiology and animal nutrition》2018,102(1):33-40
Alpha‐lipoic acid (ALA) is a multifunction antioxidant that is produced in small amount by cells as well as its dietary provision facilitates fatty acid mobilization, energy expenditure as well as can scavenge free radicals in poultry birds. It exists in oxidized as well as reduced form, characterized by growth promoting, anti‐inflammatory, antioxidative, immunostimulatory, and hypocholesterolemic properties when fed as dietary supplement to farm animals particularly chicken birds. Recently, several studies reported that dietary supplementation of ALA can influence growth performance indicators, immunological, biochemical characteristics, lipid metabolism, and oxidative stress as well as increase antioxidant potential and storability of poultry meat and meat products. Accordingly, this paper adds the reviews and discusses the outcomes of studies documenting the effect of lipoic acid dietary fortification on growth performance, biochemical, and immunological characteristics as well as the effects on lipid peroxidation of fresh meat and meat‐based products. Furthermore, this paper also describes the possibilities of utilization of ALA as a feed additive in poultry nutrition to improve the growth performance of poultry as well as meat quality of resultant chicken birds. 相似文献
17.
An animal's response to a stressor is to increase metabolic rate, and thus energy consumption through the activation of the hypothalamic-pituitary-adrenal axis. Changes to energy use by an animal are likely to influence the efficiency with which it is utilised. In this study, we tested the hypothesis that less efficient sheep are more responsive to exogenous administration of adrenocorticotropin hormone. This was done by firstly determining the appropriate dose (0.4, 1.6 or 6.4microg/kg LW) and peak serum cortisol response time (45min) to exogenous administration of adrenocorticotropin hormone in a pilot study (n=3 sheep). Following this, adrenocorticotropin hormone (2.0microg/kg LW) stimulated cortisol levels were measured in a larger group of sheep (n=50) of known feed efficiency (feed conversion ratio and residual feed intake values). Less efficient sheep (more positive residual feed intake values) were found to have a greater (P<0.001) increase in cortisol concentration in comparison to more efficient animals. Those sheep which had higher levels of cortisol also had a greater proportion (P<0.001) of fat tissue. These data clearly demonstrated that efficiency of energy use, when measured as residual feed intake, is significantly related to an animal's stress response. These findings have important implications for understanding the physiological mechanisms underpinning efficiency of energy use, and may be useful in successfully identifying animals which are superior in terms of feed efficiency. 相似文献
18.
《Domestic animal endocrinology》1996,13(2):107-126
Satellite cells are the postnatal myogenic cells, as they provide myonuclei to support skeletal muscle hypertrophy and are principal cells responsible for myofiber repair and regeneration. Even though research with satellite cells from meat animals is new, considerable data exist to suggest that these cells are regulated through both intrinsic and extrinsic mechanisms. This review covers the present status of the extrinsic factors known or postulated to modulate meat animal satellite cell growth and development. 相似文献
19.
生长激素受体基因表达的研究进展 总被引：4，自引：1，他引：3
生长激素(growth hormone,GH)在促进动物生长、发育等代谢过程中起着重要作用。长期以来人们在研究动物生长发育机制及其调控时,主要着眼于提高生长激素水平。然而GH必须与靶器官上生长激素受体(growth hormone receptor,GHR)结合,由GHR介导将信号传入细胞内才能发挥作用。大量研究结果显示,动物生长速度与GH水平并不完全平行,但与肝脏GHR呈明显正相关。生长快的肉鸡血液中GH和垂体GH mRNA水平比生长慢的蛋鸡低,而肝脏GHR水平比蛋鸡高;患侏儒症动物血液中GH浓度却比正常动物高,而GHR胞外部分缺失或功能不全。可见GHR基因表达对动物生长发育调控起着至关重要的作用。 相似文献
20.
Quantitative morphological methods were used to analyse the histomorphometric changes and variations in the number and size of cells from diverse cellular populations in testes of newly hatched chicks treated with follicle stimulating hormone (FSH) during embryonic development. The tissue was fixed and embedded in Epon and sections were morphometrically measured under light microscopy, using point counting for volume densities and the Floderus equation to determine numerical density. The average volume of the individual cell was determined by dividing the volume density by the numerical density. Results indicate that FSH administration causes an increase in the number of Sertoli cells and spermatogonia, as well as enlargement of the individual Sertoli cells leading consequently to an increase in the diameter and volume density of the testicular seminiferous tubules. Results also reveal an increase in the volume density of the interstitial cords of the Leydig cells, this expansion is due to the enlargement of the individual Leydig cells and not to an increase in their number, which remains constant. We conclude that testes of chick embryos are able to respond to FSH treatment, as revealed by the changes in the number and size of the cells conforming the diverse cellular populations of the testis. FSH treatment during embryonic development induces histomorphometric changes in both the interstitial tissue and seminiferous tubules, accelerating their growth and differentiation. 相似文献