Ghrelin促生长机理的研究进展

垂体分泌的生长激素 (GH)是调节整个机体生长代谢的一种多功能激素。关于GH分泌调节的研究一直是营养学界研究的热点。最近在生长激素促释放素 (growthhormonesecretagogues,GHSs)对GH分泌调节的研究过程中发现的活性肽ghrelin对GH、胃酸的分泌 ,采食量的调节等方面起重要作用 ,本文将综述有关ghrelin的最新研究进展     

胃饥饿素分泌调控机制的研究进展

胃饥饿素(Ghrelin)是一种由28个氨基酸组成的多肽,具有促进生长激素释放、调控动物采食和能量代谢等作用.文章从Ghrelin的转录、修饰和体内循环过程出发,并对一些营养物质和激素对Ghrelin分泌的影响与调控机制进行综述,旨在为进一步研究调控Ghrelin分泌的机制提供理论参考,也为阐明动物的促生长机制提供理论...     

肝脏氧化调节因子及其对动物采食调节机制的研究进展

合理的采食量是优化奶牛等各种动物消化和吸收营养物质的前提,是提高动物生产性能和健康状况的关键因素。肝脏氧化是调节动物采食量的重要代谢途径,生能物质可通过提高动物肝脏细胞能量状态,进而降低肝细胞膜电位和细胞膜信号分子释放,最终抑制动物采食。而此代谢途径可被非营养性（2,5-脱水-1）-甘露醇,棕环氧酸甲酯等）和营养性物质（2-脱氧葡萄糖、丙酮酸盐等）调控,进而影响动物的采食量．,本文就非营养性和营养性物质对动物肝脏氧化代谢和采食量调节效果及机制进行综述。     

神经调节肽U的研究进展

神经调节肽U(neurom ed in U,NMU)是一种结构上高度保守的神经肽,广泛分布在下丘脑、垂体、胃肠道以及泌尿生殖系统,具有刺激平滑肌收缩、抑制摄食、调节能量平衡、抑制胃酸分泌、延缓胃排空和参与下丘脑-垂体-肾上腺轴的调节等多种功能,对肠道离子转运、局部血流和血压的调节甚至对疼痛和免疫调控等都有作用。作者就其主要功能和部分作用机制的研究进展作一综述。     

动物肠道葡萄糖吸收调节的分子机制研究进展

葡萄糖是动物机体必需的营养素之一，是体内重要的能量来源，在动物代谢过程中发挥着重要作用。迄今其吸收机制已经基本阐明并为大多数学者所接受，然而由于研究方法和条件的限制，其调节机制仍不完全清楚。作者主要综述了葡萄糖在动物肠道中的吸收机理以及日粮、发育、激素等活性因子对葡萄糖吸收调节的分子机制。     

禽类采食量生理调节因子的研究进展

采食量是影响禽类生长最重要的因素之一。认识采食量的调节规律和机制,旨在更有效地调节家禽的采食量,为生产实践提供重要指导。禽类采食量的生理调节机制十分复杂,涉及许多神经通路和体液因子的调节。本文将重点介绍采食量生理调节因子。     

家禽肌胃糜烂病的防治

1 肌胃糜烂的原因引起肌胃糜烂的原因很复杂.一般认为饲料的鱼粉中含有的肌胃糜烂素是导致本病发生的根本原因.所谓肌胃糜烂素是对鱼粉中导致肌胃糜烂、溃疡的成分的统称.鱼蛋白中含有的氨基酸,在细菌的作用下形成各种组织胺,这些组织胺通过H2受体作用于胃黏膜而使胃酸分泌亢进,从而造成肌胃的糜烂和溃疡;鱼粉加工过程中高温使其过量游离组氨酸与酪蛋白结合形成组氨酸的酪蛋白混合物,这种混合物可破坏肌胃黏膜表面的类角素保护层,使砂囊腺的分泌紊乱,从而导致肌胃糜烂和溃疡的发生.流出的血液在胃酸的作用下变成黑色,与胃内容物夹杂,使上行至嗉囊内容物和下行的腹泻物均呈现黑褐色.     

肠道激素和食欲的关系

食欲的调控涉及到中枢和外周神经系统和内分泌系统。最近的研究结果显示一些消化道激素(ghre lin、神经肽YY、胰多肽、GLP-1和胃泌酸调节素)在有下丘脑调控的食欲过程中扮演一定的生理角色。这表明消化道激素食欲调控系统可能是研发抗肥胖病药物以及调节动物食欲的一个有潜力的对象。     

甜味剂在断奶仔猪肠道发育中的作用

肠道发育对于所有青年动物的健康和生产性能至关重要,对处于断奶时期的仔猪更是如此。在断奶后由于肠绒毛萎缩、营养吸收能力降低和可用能减少,仔猪采食量会出现降低。不幸的是,这种现象通常会出现在非常关键的生长时期,要知道断奶后体重与出栏体重高度相关。经由肠道吸收的主要营养素中,葡萄糖尤为重要,因为葡萄糖是机体生长的一个能量来源。例如,葡萄糖能够促进肠黏膜发育,从而提高营养吸收率,通过促进猪只的整体生长来回报养猪者。     

胃饥饿素对鱼类摄食调控的研究进展北大核心CSCD

胃饥饿素(Ghrelin)又称作生长激素释放肽,作为脑肠肽,其可促进鱼类摄食。有研究报道禁食或摄食前可提高鱼类Ghrelin表达水平,中枢或外周注射Ghrelin可增加鱼类的摄食量。本文根据Ghrelin在哺乳动物和鱼类上的研究进展,阐述了Ghrelin的结构、组织分布和对鱼类摄食的调控及相关机制,为今后鱼类摄食调控及生长的研究和生产实践提供理论依据。     

Oxyntomodulin reduces expression of glucagon‐like peptide 1 receptor in the brainstem of chickens

Oxyntomodulin (OXM) is a peptide released from the gut and attenuates food intake by acting on hypothalamus. However, its role at the molecular level is not well studied. In the first section of this study, we analysed the effect of OXM on food intake behaviour after injecting into the lateral ventricle of chickens. The outcome showed that food intake decreased significantly after administering 4 nmol of OXM. In the second part, the expression of glucagon‐like peptide 1 receptor (GLP‐1R) in the brainstem was analysed by real‐time RT‐PCR. The results showed that expression of GLP‐1R was reduced to 27% and 16% at 30 and 90 mins after injection of OXM respectively. In saline‐injected chickens, no reduction in GLP‐1R was seen. It can be concluded that OXM has a down regulatory effect on the responding receptor, GLP‐1R and OXM in chicks has the same reductive effect on food intake as in the mammals.     

不同葡萄糖水平对水貂日粮消化的影响

为了探讨水貂日粮中添加葡萄糖是否会增加可消化碳水化合物的摄入量以及消化情况,研究了不同葡萄糖水平对水貂生长期和冬毛期的采食量和各种营养物质消化率的影响。结果表明,随着葡萄糖水平的升高,水貂生长期和冬毛期对营养物质采食量逐渐下降(P<0.05),消化率逐渐升高(P<0.05),可消化营养物质的采食量下降,但差异不显著(P>0.05)。     

Protein intake but not feed intake affects dietary energy for finishing pigs

The effects of dietary protein and feeding levels on dietary metabolizable (ME) and net energy (NE) content were determined in 24 pigs, each offered two diets at 2.0 times the energetic maintenance requirement or for ad libitum intake between 55 and 95 kg body weight. Within feeding levels, pigs received, in random order, low‐protein (LP; 11.2% CP, 0.61% lysine) or high‐protein (HP; 20.2% CP, 0.61% lysine) diets of similar digestible energy content. Dietary NE was calculated from heat production based on 24‐h indirect calorimetry following a 7‐day N‐balance period. Feed intake was greater for LP than HP when fed for ad libitum intake (p = 0.001). Protein level did not affect daily gain (p > 0.1) but HP improved gain: feed (p = 0.003). Dietary ME and NE were not significantly affected by feeding level but were decreased by high protein intake (p < 0.07). Reducing dietary protein reduced urinary energy losses and increased energy retention but did not affect heat production. The effect of dietary protein restriction was already evident on the ME level and carried over to a similar degree to the NE level because the utilization of ME was not affected by protein level. Dietary ME and NE decreased by 0.012 MJ/kg (p = 0.014) and 0.018 MJ/kg (p = 0.062), respectively, for each gram per day N intake. The results suggest that although there was an effect of protein level on NE, the greatest effect occurred at the level of ME. However, the prediction of both ME and NE may be improved by adopting energy values for dietary protein that changes with dietary protein content.     

Levels of milk urea, plasma constituents and rumen liquid ammonia in relation to the feeding of dairy cows during early lactation

The study was undertaken to establish the relationships between milk and plasma urea levels and protein supply, using traditional and new measures of feed protein value. Samples of milk and plasma were taken before morning feeding twice weekly for the first 3 months post partum from 21 multiparous cows and 7 heifers. Samples of rumen fluid were collected every second week. The cows were distributed into 4 different feeding groups. Feeding regimens were factorial with respect to protein content of the concentrates (i.e. Low protein (Lp): 12.5% digestible crude protein (DCP) vs. High protein (Hp): 17.5% DCP) and concentrate allowances (i.e. Low energy (Le): substandard vs. High energy (He): standard). Silage was offered ad libitum. The within-animal coefficients of correlation between milk and plasma urea levels, and between milk urea levels and the levels of ammonia in the rumen fluid wer r = 0.88 (p less than 0.001) and r = 0.75 (p less than 0.001), respectively. Analysis of variance showed the following sources of urea variation to be significant: Protein balance in the rumen (PBV), intake of DCP, intake of amino acids absorbed in the intestine (AAT), intake of fattening feed units, and the individual animal factor. A similar tendency was found for the variation of ammonia in rumen fluid. The coefficients of determination (R2 model) were not increased by introducing protein balance (BADCP), the amount of PBV and AAT in the dry matter ingested, or the protein/energy ratio as alternative parameters of protein intake in the models. The levels of protein or energy intake did not significantly influence the levels of plasma albumin. The correlations between urea levels and other plasma indicators of metabolic status and liver function were generally low.     

Partitioning of nutrient and trace elements in feed between body retention,faeces and urine by growing dairy-breed steers

The partitioning of nutrients and trace elements from feeds, drinking water and mineral supplements on growth, faeces and urine of growing cattle was studied with eight steers in a balanced Latin square design with two replicates, each comprising four treatments (diet compositions), four periods and four animals. The treatments were four rations with a silage proportion of 15, 30, 60 and 100% of the dry matter. Records were taken of the individual intake of silage, concentrates, mineral supplements and water, and excretions by collecting all urine and faeces. All feeds, urine, faeces and water were analysed for their content of Al, Ca, Cd, Cl, Co, Cu, Fe, K, Mg, Mn, Mo, N, Na, Ni, P, S, Se, and Zn. Elements that were mainly excreted in faeces (Ca, Cd, Cu, Fe, P, and Zn) tended to have a constant uptake in amount. As there is a fairly good correlation between DM consumption and faeces production, it is possible to estimate the amount of these elements excreted at farm level by analysing a faeces sample. Elements that are excreted in significant amounts in both faeces and urine (Cl, K, Mg, Mo, N, Na, S, and Se) tended to have a constant uptake over treatments as a fraction of the feed content. It is more difficult to estimate the amounts of these elements at farm level because it is more difficult to predict urine production than faeces production.     

奶牛皱胃变位及其营养调控

奶牛皱胃变位是皱胃正常解剖学位置改变的一种疾病。该病的发生受多种因素的影响,营养方面有奶牛的采食量和产犊后日粮的转换以及产犊后的一些并发情况,如负能量平衡、低钙血症等都可能引发皱胃的变位。本文就皱胃变位的病因及其预防作一综述。     

Nutritional requirement of digestible tryptophan for white-egg layers of 60 to 76 weeks of age

The objective of this study was to determine the nutritional requirement of digestible Trp for white egg layers in the period from 60 to 76 wk of age. A total of 180 Dekalb White layers with an average weight of 1,345 kg were distributed in a completely randomized design with 5 increasing levels of digestible Trp (0.167, 0.175, 0.183, 0.191, and 0.199%), 6 replicates, and 6 birds per experimental unit. The diets of the treatments contained 0.759% of digestible Lys, which was obtained using the prediction equation of the Brazilian Tables for Poultry and Swine, and each treatment consisted of a digestible Trp-to-Lys ratio of 22, 23, 24, 25, or 26%. The digestible Trp levels in the diet had a quadratic effect on egg production, egg mass, and conversion per mass and per dozen eggs, and a linear effect on egg weight. In conclusion, a diet with 0.192% digestible Trp, in a 25.33% ratio with digestible Lys or 212 mg/bird per day, can be recommended for white egg layers of 60 to 76 wk of age.     

Influence of Dietary Energy and Antibiotic on Performance,Egg Solids,and Egg Quality in Bovans White and Dekalb White Hens

A 4 × 2 × 2 factorial experiment with 4 dietary energy levels (2,776, 2,820, 2,864, and 2,908 kcal/kg) and 2 strains (Bovans White and Dekalb White) with and without Tylosin was conducted to determine the influence of dietary energy and antibiotic on performance, egg solids, and egg quality. The experiment lasted 10 wk. Bovans White hens (n = 768) and Dekalb White hens (n = 768) at 55 wk of age were randomly divided into 16 treatments (8 replicates of 12 birds per treatment). Bovans hens had significantly greater egg production and significantly lower egg weight, egg-specific gravity, and shell weight than Dekalb hens. Increasing dietary energy by the addition of poultry oil had no significant effect on performance, egg solids, or eggshell quality. An ideal dietary energy level for optimal performance could not be determined. There can be no fixed ideal dietary energy level for optimal profits, due to varying feed ingredient and egg price. Although Tylosin supplementation had no effect on performance or egg solids, Tylosin significantly reduced dirty eggs, resulting in a positive effect on egg quality.     

干奶期不同能量摄入对围产期乳牛血液葡萄糖胰高血糖素和胰岛素浓度的影响

将围产期健康乳牛30头随机分为3组，分别于产前第28d开始饲喂标准日粮（能量摄入i00％组）、标准日粮增加20％的日粮（能量摄入120％组）和标准日粮减少20％的日粮（能量摄入80％组），产后备组乳牛均饲喂标准泌乳日粮，至产后第56d结束，观察干奶期不同能量摄入水平对围产期健康乳牛血液葡萄糖、胰高血糖素和胰岛素浓度的影响。结果表明，产前低能饲喂可以增加围产期乳牛血浆葡萄糖浓度，干奶期不同能量摄入水平对围产期健康乳牛血液葡萄糖、胰高血糖素和胰岛素浓度起重要调节作用。     

Simultaneous Bayesian estimation of genetic parameters for curves of weight,feed intake,and residual feed intake in beef cattle

Rates of gain and feed efficiency are important traits in most breeding programs for growing farm animals. The rate of gain (GAIN) is usually expressed over a certain age period and feed efficiency is often expressed as residual feed intake (RFI), defined as observed feed intake (FI) minus expected feed intake based on live weight (WGT) and GAIN. However, the basic traits recorded are always WGT and FI and other traits are derived from these basic records. The aim of this study was to develop a procedure for simultaneous analysis of the basic records and then derive linear traits related to feed efficiency without retorting to any approximation. A bivariate longitudinal random regression model was employed on 13,791 individual longitudinal records of WGT and FI from 2,827 bulls of six different beef breeds tested for their own performance in the period from 7 to 13 mo of age. Genetic and permanent environmental covariance functions for curves of WGT and FI were estimated using Gibbs sampling. Genetic and permanent covariance functions for curves of GAIN were estimated from the first derivative of the function for WGT and finally the covariance functions were extended to curves for RFI, based on the conditional distribution of FI given WGT and GAIN. Furthermore, the covariance functions were extended to include GAIN and RFI defined over different periods of the performance test. These periods included the whole test period as normally used when predicting breeding values for GAIN and RFI for beef bulls. Based on the presented method, breeding values and genetic parameters for derived traits such as GAIN and RFI defined longitudinally or integrated over (parts of) of the test period can be obtained from a joint analysis of the basic records. The resulting covariance functions for WGT, FI, GAIN, and RFI are usually singular but the method presented here does not suffer from the estimation problems associated with defining these traits individually before the genetic analysis. All the results are thus estimated simultaneously, and the set of parameters is consistent.