GABA緩解應激，提高采食

       采食是動物維持生存所必需的活動，充足的采食量更是發揮其生產潛力的必要保證。影響采食量的因素有很多，包括環境因素、動物因素、飼料因素等。在生產實踐中，飼養動物不可避免的會遭遇飼料更換、冷熱刺激、發情期狂躁好斗等因素影響，產生應激反應，從而降低采食影響生產效益。近年來對動物采食量調控的研究越來越受到重視，主要是添加外源添加劑通過神經調節、體液調節等方式來提高采食量。據報道稱，γ-氨基丁酸(γ-amino butyric acid，GABA) 具有促進動物采食量、抗應激、鎮靜等生理功能。

Foraging is a vital activity for animal survival and production. Adequate food intake is necessary to ensure the survival of animals and to better realize their productive potential. There are many factors affecting feed intake, including environmental factors, animal factors, feed factors and so on. In production practice, it is inevitable that feeding animals will suffer from feed change, cold and hot stimulation, manic and aggressive factors in heat, and produce stress response, so as to reduce the influence of food intake on production efficiency. In recent years, more and more attention has been paid to the research on the regulation of feed intake in animals. γ-amino butyric acid (GABA) has been reported to promote physiological functions such as food intake, anti-stress and sedation.

GABA是哺乳動物體內廣泛存在的一種抑制性神經遞質。近年，學界對飼用GABA在動物飼糧中添加用于對抗應激、提高采食做了大量的研究。

GABA is a widely available inhibitory neurotransmitter in mammals. In recent years, the academic community has done a lot of research on feeding GABA in animal diets to fight stress and improve food intake.

GABA簡介及其生理功能

Overview of GABA and its physiological functions

GABA又稱氨酪酸，是谷氨酸（Glu）在谷氨酸脫羧酶（GAD）作用下經α－脫羧反應獲得的產物。GABA是中樞神經系統中重要的抑制性氨基酸類神經遞質，在不同的部位其作用方式不同，在腦中GABA作用方式以突觸后抑制為主，而在髓中則以突觸前抑制為主。

GABA, also known as aminotyrosine, is the product of glutamic acid (Glu) under the action of glutamic acid decarboxylase (GAD) by the -decarboxylation reaction. GABA is an important inhibitory amino acid neurotransmitter in the central nervous system, and it has different modes of action in different parts. The mode of GABA action in the brain is dominated by post-synaptic inhibition, while that in the medulla is dominated by presynaptic inhibition.

GABA的生理功能主要體現在其對機體正常生理機能的調控上，主要有降血壓、鎮靜神經、延緩細胞衰老、抗應激等作用。此外，GABA對動物采食量也具有明顯的調控作用。

The physiological functions of GABA are mainly reflected in its regulation of normal physiological functions of the body, mainly including lowering blood pressure, calming nerves, delaying cell aging and anti-stress. In addition, GABA has an obvious regulatory effect on feed intake in animals.

提高采食的作用機制

Mechanism of improving food intake

目前，對GABA調控采食量的作用機制已有較多報道，下面僅就GABA 調控采食量的3 種最被認可的途徑作初步介紹。

The mechanism of GABA regulating feed intake has been widely reported. Now we choose the three most recognized approaches for your information.

1 抑制飽覺中樞

Inhibits satiety centers

飽覺中樞位于下丘腦腹內側核( VMH)，機體通過感應血液和下丘腦中葡萄糖濃度，將信息傳遞到VMH，再由飽覺神經調節采食。GABA 在VMH中是促進采食的信號分子。當葡萄糖缺乏時，會引起VMH中GABA 濃度升高，從而導致采食增加。

The satiety center is located in the ventromedial hypothalamus nucleus (VMH). The body sends the message to VMH by sensing glucose levels in the blood and hypothalamus, then the satiety nerve regulates feed intake. GABA is a signaling molecule in VMH that promotes feed intake. When glucose is deficient, the concentration of GABA in VMH increases. An increase in GABA concentration leads to an increase in feed intake.

2 通過味覺調控采食

Feed intake is regulated by acting on the taste response

味覺受體細胞（TRCs）有3種亞型，味覺反射是通過3種亞型的味覺細胞間信息傳遞而發揮功能的，TRCs直接受中樞神經系統支配。研究表明，動物的味蕾細胞內的GABA參與了味覺的調控，并且在動物延髓內側微注射GABA可使其采食量增加。

There are three subtypes of taste receptor cells (TRCs). The taste reflex functions through inter-cellular communication among the three subtypes of taste. TRCs are directly administered by the central nervous system. Studies have shown that GABA in the cells of animal taste buds is involved in taste regulation, and microinjection of GABA into the medial medulla oblongata of animals can increase feed intake.

3 協同NPY促進采食

Synergies with NPY to promote feed intake

NPY稱為神經肽酪氨酸，在中樞神經系統中，NPY具有促進動物采食，影響激素分泌、性行為，體溫調節等各種生物功能。促攝食的NPY神經元經過一些列的信號傳導，最終抑制交感神經和興奮副交感神經，引發強列的攝食反應。GABA是NPY增食效應的促進劑，GABA促進NPY的分泌，提高血液中NPY的濃度，進而提高動物采食。

NPY is called neuropeptide tyrosine. In the central nervous system, NPY has various biological functions such as promoting animal feed intake, affecting hormone secretion, sexual behavior, and temperature regulation. NPY neurons go through a series of signal transductions, which eventually inhibit the sympathetic and excitatory parasympathetic nerves, trigger a strong series of ingestion responses. GABA is a promoter of the dietary effect of NPY. GABA promotes the secretion of NPY and increases the concentration of NPY in the blood, which in turn increases the feed intake.

GABA緩解熱應激的作用機制

The mechanism of  GABA to alleviate heat stress

熱應激是指機體應對環境高溫所產生的非特異性應答反應。由于全球變暖，熱應激漸成為危害畜牧生產的最重要因素之一。熱應激會加速體內脂肪、糖原及蛋白質的分解代謝，以致畜禽采食量下降、生長受阻、飼料報酬下降、體重降低。

Heat stress refers to the non-specific response of the body to high temperature. Due to global warming, heat stress is becoming one of the most important factors to harm livestock production. Heat stress will accelerate the catabolism of fat, glycogen and protein in the body, resulting in the decrease of feed intake and feed remuneration.

熱應激主要通過2種方式影響畜禽生產性能，一種是激活HPA軸和抑制性神經系統；另一種是降低血漿中2種甲狀腺素［三碘甲腺原氨酸(T3)、四碘甲腺原氨酸(T4)］、胰島素的濃度以及提高皮質酮（CS）濃度來影響營養物質合成代謝過程。

Heat stress mainly affects the performance of livestock and poultry production in two ways. One is to activate the HPA axis and the inhibitory nervous system. The other is to reduce the plasma concentration of two thyroxine [triiodothylamine (T3), tetraiothylamine (T4)]and insulin,but increase the concentration of corticosterone (CS) to affect the process of nutrient anabolism.

GABA是神經系統中主要的神經拮抗劑，具有抗熱應激與鎮靜等作用。GABA介導大部分中樞神經及外周神經的消極動作。在熱應激情況下，飼糧中添加GABA可以顯著提高飼養動物的體重、采食量、日增重、胴體重以及血液中T3、胰島素的濃度，而且可以顯著降低血液中CS的濃度，緩解熱應激效應。另外，日糧中添加GABA可以提高血清抗氧化指標SOD、GSH-PX的活性，降低反應細胞膜傷害程度的指標MDA的活性，顯著降低血清COＲ、COＲT及ACTH三種激素濃度，明顯減少機體的熱應激反應。

GABA is the main nerve antagonist in the nervous system, which has the effects of heat stress and sedation. GABA mediates the passive action of most central and peripheral nerves. In the case of heat stress, dietary GABA can significantly improve the body weight, feed intake, daily weight gain, carcass weight, and blood T3 and insulin concentration of feed animals, as well as significantly reduce the concentration of CS in the animal blood to alleviate the effect of heat stress. In addition, dietary addition of GABA can improve the activity of serum antioxidant indexes SOD and GSH-PX, reduce the activity of MDA which reflects the damage degree of cell membrane, significantly reduce the concentration of three hormones-COR, CORT and ACTH, and obviously reduce the body's heat stress response.小結  Summary

GABA可以通過抑制飽感神經興奮、調控味覺反應、促進NPY（增食效應的促進劑）的分泌等方式，提高動物采食量；另外，GABA還能通過抑制中樞神經反應、抑制激素分泌等方式，減少應激反應。因此，在實踐生產中，GABA一方面可抑制應激反應、另一方面又能促進采食，從兩個維度上完美的解決了生產實踐中應激反應對動物采食量的影響，提高生產效益。

GABA can increase feed intake in animals by inhibiting the stimulation of satiety nerve, regulating the taste response, and promoting the secretion of NPY (an accelerant of feeding effect). In addition, GABA can also reduce stress response by inhibiting central nervous system response and hormone secretion. Therefore, in practical production, GABA can not only inhibit the stress response, but also promote feed intake. So that perfectly solved the effect of stress response and improved the production efficiency.

隨著夏季和禁止飼添抗生素的日期越來越近，飼養動物必定會面臨諸如高濕高熱、飼料中無抗生素、環境微生物增多等多種應激，喜食寧（GABA）必將是助您提高生產成績的較好選擇。

With the approaching of the summer and the prohibition of feeding antibiotics, feeding animals are bound to face a variety of stress, such as high humidity and high heat, no antibiotics in the feed, the increase of environmental microorganisms, and so on. GABA will be the best choice for you to improve the production efficiency.

應用方案

Application solutions

參考文獻：

3.施忠秋, 齊智利.γ-氨基丁酸調控采食量和緩解熱應激的機制.動物營養學報, 2014(1):49-53.

4.Y. Cao, F.-l. Zhao, T. Kolli, etc. GABA expression in the mammalian taste bud functions as a route of inhibitory cell-to-cell communication.The Physiological Society.2004:4006-4011.