ISSN:0003-942X    

DOI:10.1080/17450399809381910

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The Rostock research in animal nutrition has underlain in continuation and progressive development of Kellner's starch value system, net energy fat as measuring unit for energetic feed evaluation. Net energy‐fat was used as an uniform unit of measure for all farm animals with different performances. The scientific basis for the net energy‐fat system was created by numerous studies on energy retention and utilisation efficiency of pure nutrients and nutrients of feedstuffs and rations. For the estimation the energy content of feedstuffs and rations, multiple regression equations were derived on the basis of experimental results of the energy research group. The regressions for the estimation of energy values are used directly and modified in feed evaluation systems for practical use. The Rostock research group in energy metabolism created also essential contributions to factorial derivations of energy requirement of farm animals. In the presented paper selected results on maintenance energy requirement in relation to partial energy requirement values and utilisation efficiencies in growing, pregnant and lactating animals, especially cattle and pigs, are comprised. The Rostock results are compared to those from literature.

ISSN:0003-942X    

DOI:10.1080/17450399809381911

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The paper describes the energetic feed evaluation systems for ruminants, pigs, poultry and horses presently used in Germany. During the last ten years the “Ausschuß für Bedarfsnormen”; (AfB; Committee of Nutrient Requirements) of the “Gesellschaft für Ernährungsphysiologie”; (GfE, Society of Nutritional Physiology) introduced new recommendations for energy requirements of domestic animals including national and international references.

ISSN:0003-942X    

DOI:10.1080/17450399809381912

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The advantages and disadvantages of metabolisable and net energy as parameters of energetic feed evaluation are discussed. For a global comprehensive standardisation of the energetic feed evaluation, the metabolisable energy (ME) will have a preference. The principles of an energetic feed evaluation system with ME as parameter are explained according to which the subsystems for all species of animals should be worked out uniformly. The subsystems for the most important farm animals integrate themselves in addition to ME for predicting the energy and food needs of the animal also the net energy (NE) by taking a standard feedstuff to characterise the relative energetic feed value of the feedstuffs for one or more partial performances of the animal species concerned.

ISSN:0003-942X    

DOI:10.1080/17450399809381913

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The need for improvement of feed information in future is discussed from the perspective for implementation in practice. Weaknesses of the current feed evaluation systems, energy systems in particular, are described: prediction of voluntary feed intake, additivity of digestibilities of individual feedstuffs and dynamics of digestion, efficiency of utilization of energy and variation in maintenance requirements. A brief inventory of models to quantify energy and nutrient metabolism by farm animals is followed by an overview of aspects required to fulfill the demands for a nutrient‐oriented feed evaluation. These include feed characteristics to determine and animal aspects, as well as involvement of environmental and management factors. The need for better harmonization of methods and quality of feed information and for international coordination in this matter is underlined.

ISSN:0003-942X    

DOI:10.1080/17450399809381914

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Energy content of feedstuffs has to be determined by animal experiments. For practical purposes energy content of feeds was predicted by data onin vivodigestibility of nutrients,in vitrodigestibility and different chemical parameters. Especially chemical andin vitroparameters were used in different combinations as predictors. The accuracy of such equations has to be discussed as well as cost and feasibility.

ISSN:0003-942X    

DOI:10.1080/17450399809381915

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Short‐chain fatty acids (SCFA),viz.acetate, propionate and butyrate are quantitatively important substrates in ruminant energy metabolism. In the reviewed literature, 16–44% of ME intake was recovered as portal appearance of SCFA. This is considerably lower than expected when related to the estimated intra‐gastric flux of SCFA. The discrepancy is caused by portal drained viscera metabolism of arterially abundant metabolites e.g., acetate and the metabolism of acetate and butyrate to acetoacetate and D‐3‐hydroxybu‐tyrate in the absorptive epithelia. Even though considerable variations between experiments on acetate and propionate appearance are found, there seems to be a great deal of evidence that the proportion of gastroin‐testinally produced acetate and propionate absorbed to the portal blood is 50–75%. The portal recovery of butyrate has been found to be between 10 and 36% dependent on intraruminal infusion rate.

ISSN:0003-942X    

DOI:10.1080/17450399809381916

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A new dimension to the regulation of energy balance has come from the identification of theob(obese) gene and its protein product, leptin. Leptin is produced primarily in white adipose tissue, but synthesis also occurs in brown fat and the placenta. Several physiological functions have been described for leptin‐the inhibition of food intake, the stimulation/maintenance of energy expenditure, as a signal of energy reserves to the reproductive system, and as a factor in haematopoiesis. The production of leptin by white fat is influenced by a number of factors, including insulin and glucocorticoids (which are stimulatory), and fasting, cold exposure and ß‐adrenoceptor agonists (which are inhibitory). A key role in the regulation of leptin production is envisaged for the sympathetic nervous system, operating through ß3‐adreno‐ceptors. The leptin receptor gene is expressed in a wide range of tissues, and several splice variants are evident. A long form variant (Ob‐Rb) with an intracellular signalling domain is found particularly in the hypothalamus. Leptin exerts its central effects through neuropeptide Y, and through the glucagon‐like peptide‐1 and melanocortin systems, but it may also interact with other neuroendocrine pathways. The role and function of the leptin system in agricultural animals has not been established, but it offers a potential new target for the manipulation of body fat.

ISSN:0003-942X    

DOI:10.1080/17450399809381917

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The nonessential amino acids are involved in a large number of functions that are not directly associated with protein synthesis. Recent studies using a combination of transorgan balance and stable isotopic tracers have demonstrated that a substantial portion of the extra‐splanchnic flux of glutamate, glutamine, glycine and cysteine derives from tissue synthesis. A key amino acid in this respect is glutamic acid. Little glutamic acid of dietary origin escapes metabolism in the small intestinal mucosa. Furthermore, because glutamic acid is the only amino acid that can be synthesized by mammals by reductive amination of a ketoacid, it is the ultimate nitrogen donor for the synthesis of other nonessential amino acids. Because the synthesis of glutamic acid and its product glutamine involve the expenditure of adenosine triphosphate (ATP), it seems possible that nonessential amino acid synthesis might have a significant bearing on the energetics of protein synthesis and, hence, of protein deposition. This paper discusses the topic of the energy cost of protein deposition, considers the metabolic physiology of amino acid oxidation and nonessential amino acid synthesis, and attempts to combine the information to speculate on the overall impact of amino acid metabolism on the energy exchanges of animals.

ISSN:0003-942X    

DOI:10.1080/17450399809381918

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Beyond the energy requirement of maintenance, the assimilated energy, occurring in bioproducts, is linearly proportional to the intake of metabolizable energy in non‐underfed conditions. In contrast, resting metabolic rate is differing between individuals within a population of an animal species. As adaptability to changed environmental conditions may play a role, young bulls were exposed to thermoneutral (18°C) and low (4°C) ambient temperatures and were fed at two feeding levels (1.0 and 1.6 times energy requirement in maintenance) to produce metabolic rate differences, using the same animals, metabolic rate was altered by reducing the sympathetic outflow in each case. Expression of sulfonylurea receptors in circulating mononuclear leukocytes and cells from skeletal muscle (m. semitendinosus)was studied by flow cytom‐etry. Changes of metabolic rate at rest corresponded to the portion of cells with sulfonylurea receptors expression. The data from reducing the sympathetic outflow and those from sulfonylurea receptors expression are useful to explain metabolic rate differences among individuals of an animal population.

ISSN:0003-942X    

DOI:10.1080/17450399809381919

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor