动物营养学报    2022, Vol. 34 Issue (7): 4359-4368    PDF    
引用本文
秦昆鹏, 杨涛, 王永芳, 赵玉蓉. 饲粮添加乙酸钠对白羽肉鸡生长性能、屠宰性能、肉品质和血清生化指标的影响[J]. 动物营养学报, 2022, 34(7): 4359-4368.  
QIN Kunpeng, YANG Tao, WANG Yongfang, ZHAO Yurong. Effects of Dietary Sodium Acetate on Growth Performance, Slaughter Performance, Meat Quality and Serum Biochemical Indices of White-Feathered Broilers[J]. Chinese Journal of Animal Nutrition, 2022, 34(7): 4359-4368.  
饲粮添加乙酸钠对白羽肉鸡生长性能、屠宰性能、肉品质和血清生化指标的影响
秦昆鹏 , 杨涛 , 王永芳 , 赵玉蓉     
湖南农业大学动物科学技术学院, 长沙 410128
收稿日期: 2021-12-15
基金项目: 湖南省教育厅重点项目(18A087)
作者简介: 秦昆鹏(1996—)，男，湖南娄底人，硕士研究生，动物营养与饲料科学专业。E-mail: 1178843458@qq.com.
通信作者: 赵玉蓉，教授，博士生导师，E-mail: 1335434506@qq.com.
摘要: 本试验旨在探究饲粮中添加不同水平乙酸钠对白羽肉鸡生长性能、屠宰性能、肉品质和血清生化指标的影响。采用单因素完全随机设计, 选择288只7日龄健康、体重相近的罗斯308白羽肉鸡, 随机分为6个组, 每组6个重复, 每个重复8只鸡。各组分别饲喂基础饲粮(对照组)及在基础饲粮中添加不同水平(0.1%、0.2%、0.3%、0.4%和0.5%)乙酸钠的饲粮。试验期35 d。结果表明: 1)各组白羽肉鸡平均日增重、平均日采食量和料重比之间均无显著差异(P＞0.05)。2)各组白羽肉鸡屠宰率、半净膛率、全净膛率、胸肌率和腿肌率之间均无显著差异(P＞0.05)。3)各组白羽肉鸡胸肌亮度(L*)和黄度(b*)值、24和48 h滴水损失以及屠宰后24 h pH(pH24 h)之间均无显著差异(P＞0.05), 而0.2%、0.4%和0.5%乙酸钠添加组胸肌屠宰后45 min pH(pH45 min)显著低于对照组(P＜0.05), 0.1%和0.3%乙酸钠添加组胸肌pH45 min与对照组相比无显著差异(P＞0.05);0.1%、0.2%、0.3%和0.5%乙酸钠添加组胸肌红度(a*)值显著高于对照组(P＜0.05), 0.4%乙酸钠添加组胸肌a*值与对照组相比无显著差异(P＞0.05);0.3%、0.4%和0.5%乙酸钠添加组胸肌系水力显著高于对照组(P＜0.05), 0.1%和0.2%乙酸钠添加组胸肌系水力与对照组相比无显著差异(P＞0.05)。4)各组白羽肉鸡腿肌pH45 min、pH24 h、L*、a*和b*值以及24和48 h滴水损失之间均无显著差异(P＞0.05), 0.3%、0.4%和0.5%乙酸钠添加组腿肌系水力显著高于对照组(P＜0.05), 0.1%和0.2%乙酸钠添加组腿肌系水力与对照组相比无显著差异(P＞0.05)。5)各组白羽肉鸡血清葡萄糖(GLU)含量和谷草转氨酶(AST)活性之间无显著差异(P＞0.05)。0.4%和0.5%乙酸钠添加组血清甘油三酯(TG)含量显著高于对照组(P＜0.05), 0.1%、0.2%和0.3%乙酸钠添加组血清TG含量与对照组相比无显著差异(P＞0.05);0.1%、0.2%、0.4%和0.5%乙酸钠添加组血清总胆固醇(TC)含量显著高于对照组(P＜0.05), 0.3%乙酸钠添加组血清TC含量与对照组相比无显著差异(P＞0.05);0.1%、0.2%、0.3%、0.4%和0.5%乙酸钠添加组血清低密度脂蛋白胆固醇(LDL-C)含量均显著高于对照组(P＜0.05);0.2%、0.4%和0.5%乙酸钠添加组血清高密度脂蛋白胆固醇(HDL-C)含量显著高于对照组(P＜0.05), 0.1%和0.3%乙酸钠添加组血清HDL-C含量与对照组相比无显著差异(P＞0.05);0.4%和0.5%乙酸钠添加组血清谷丙转氨酶(ALT)活性显著高于对照组(P＜0.05), 0.1%、0.2%、0.3%乙酸钠添加组血清ALT活性与对照组相比无显著差异(P＞0.05)。综上所述, 饲粮添加乙酸钠对白羽肉鸡生长性能和屠宰性能无显著影响, 但对肉品质和血清生化指标有显著影响; 添加适宜水平的乙酸钠可以一定程度地改善肌肉a*值和系水力, 但过量添加会导致血脂上升、肝脏受损; 本试验条件下, 白羽肉鸡饲粮中乙酸钠适宜添加水平为0.3%。
关键词: 乙酸钠    白羽肉鸡    生长性能    屠宰性能    肉品质    血清生化指标    
Effects of Dietary Sodium Acetate on Growth Performance, Slaughter Performance, Meat Quality and Serum Biochemical Indices of White-Feathered Broilers
QIN Kunpeng , YANG Tao , WANG Yongfang , ZHAO Yurong     
College of Animal Science and Technology, Hunan Agricultural University, Changsha 410128, China
Corresponding author: ZHAO Yurong, professor, E-mail: 1335434506@qq.com.
Abstract: This experiment was conducted to investigate the effects of different dietary sodium acetate levels on growth performance, slaughter performance, meat quality and serum biochemical indices of white-feathered broilers. A total of 288 healthy Ross 308 white-feathered broilers of 7-day-old with similar body weight were randomly divided into 6 groups with 6 replicates per group and 8 broilers per replicate in a single-factor completely randomized design. Broilers in each group were fed a basal diet (control group) and the basal diet supplemented with different levels of sodium acetate (0.1%, 0.2%, 0.3%, 0.4% and 0.5%), respectively. The experiment lasted for 35 days. The results showed as follows: 1) there were no significant differences in average daily gain, average daily feed intake and feed to gain ratio of white-feathered broilers among all groups (P > 0.05). 2) There were no significant differences in dressed rate, half-eviscerated rate, all eviscerated rate, breast muscle rate and leg muscle rate of white-feathered broilers among all groups (P > 0.05). 3) There were no significant differences in the brightness (L*) and yellowness (b*) values of breast muscle, drop loss at 24 and 48 h and pH at 24 h (pH24 h) after slaughter among all groups (P > 0.05). However, the pH of breast muscle at 45 min (pH45 min) after slaughter in 0.2%, 0.4% and 0.5% sodium acetate supplemental groups was significantly lower than that in the control group (P < 0.05), and the pH45 min in breast muscle in 0.1% and 0.3% sodium acetate supplemental groups had no significant difference compared with the control group (P > 0.05). The redness (a*) value of breast muscle in 0.1%, 0.2%, 0.3% and 0.5% sodium acetate supplemental groups was significantly higher than that in the control group (P < 0.05), while there was no significant difference in a* value of breast muscle in 0.4% sodium acetate supplemental group compared with the control group (P > 0.05). The water-holding capacity of breast muscle in 0.3%, 0.4% and 0.5% sodium acetate supplemental groups was significantly higher than that in the control group (P < 0.05), while there was no significant difference in the water-holding capacity of breast muscle in 0.1% and 0.2% sodium acetate supplemental groups compared with the control group (P > 0.05). 4) There were no significant differences in leg muscle pH45 min, pH24 h, values of L*, a* and b*, and drip loss at 24 and 48 h among all groups (P > 0.05). The water-holding capacity of leg muscle in 0.3%, 0.4% and 0.5% sodium acetate supplemental groups was significantly higher than that in the control group (P < 0.05), while there was no significant difference in leg muscle water-holding capacity in 0.1% and 0.2% sodium acetate supplemental groups compared with the control group (P > 0.05). 5) There were no significant differences in serum glucose (GLU) content and aspartate aminotransferase (AST) activity among all groups (P > 0.05). The serum triglyceride (TG) content in 0.4% and 0.5% sodium acetate supplemental groups was significantly higher than that in the control group (P < 0.05), while there was no significant difference in serum TG content in 0.1%, 0.2% and 0.3% sodium acetate supplemental groups compared with the control group (P > 0.05). The serum total cholesterol (TC) content in 0.1%, 0.2%, 0.4% and 0.5% sodium acetate supplemental groups was significantly higher than that in the control group (P < 0.05), while there was no significant difference in serum TC content in 0.3% sodium acetate supplemental group compared with the control group (P > 0.05). The serum low-density lipoprotein cholesterol (LDL-C) content in 0.1%, 0.2%, 0.3%, 0.4% and 0.5% sodium acetate supplemental groups was significantly higher than that in the control group (P < 0.05). The serum high-density lipoprotein cholesterol (HDL-C) content in 0.2%, 0.4% and 0.5% sodium acetate supplemental groups was significantly higher than that in the control group (P < 0.05), while the serum HDL-C content in 0.1% and 0.3% sodium acetate supplemental groups was not significantly different from that in the control group (P > 0.05). The serum alanine aminotransferase (ALT) activity in 0.4% and 0.5% sodium acetate supplemental groups was significantly higher than that in the control group (P < 0.05), while there was no significant difference in ALT activity in 0.1%, 0.2% and 0.3% sodium acetate supplemental groups compared with the control group (P > 0.05). In conclusion, dietary sodium acetate has no significant effects on growth performance and slaughter performance of white-feathered broilers, but has significant effects on meat quality and serum biochemical indices. The appropriate supplemental level of sodium acetate can improve muscle a* value and water-holding capacity to a certain extent, but excessive addition will lead to the rise of blood lipids and liver damage. Under the conditions of this experiment, the optimal dietary sodium acetate supplemental level for white-feathered broilers is 0.3%.
Key words: sodium acetate    white-feathered broilers    growth performance    slaughter performance    meat quality    serum biochemical indices    

近年来，有关短链脂肪酸在动物生产中的研究日渐增多。短链脂肪酸在机体内主要来源于结肠内的微生物发酵，研究发现其不仅能作为能量底物为机体供能，而且还对机体脂肪代谢、糖代谢、免疫等生理活动具有重要调节作用[1-4]。乙酸是动物机体内最主要的短链脂肪酸之一，占体循环内短链脂肪酸含量的60%，并且以游离酸(CH3COO-)的形式存在[5]。有研究报道，乙酸除了能作为能量底物和碳源参与机体内代谢活动外，还对机体食欲调节、脂肪代谢和胰岛素抵抗等具有重要影响[6-8]，并且乙酸及其盐类在含有相同CH3COO-含量时其生物学效价一致[9]。由过往研究推测，乙酸及其盐类对机体食欲调节和脂肪代谢的影响可能会对肉鸡生长代谢产生影响。因此，本试验旨在探究饲粮中添加不同水平乙酸钠对白羽肉鸡生长性能、屠宰性能、肉品质和血清生化指标的影响，以期获得饲粮中添加乙酸钠对白羽肉鸡的作用效果，同时也为乙酸及其盐类在肉鸡饲粮中的合理应用提供参考。

1 材料与方法 1.1 试验材料

食品级乙酸钠(99%)，由深圳某生物科技有限公司提供。罗斯308白羽肉鸡购自湖南某实业有限公司。

1.2 试验设计

采用单因素试验设计，选用1日龄罗斯308肉仔鸡，预饲7 d(饲喂基础饲粮)后选择体重相近和精神状态良好的肉鸡288只进行随机分组，根据饲粮不同分为6个组，分别饲喂乙酸钠添加水平为0(对照组，基础饲粮)、0.1%、0.2%、0.3%、0.4%和0.5%的饲粮，每组6个重复(笼)，每个重复8只鸡。试验期为35 d。根据《鸡饲养标准》(NY/T 33—2004)配制玉米-豆粕型基础饲粮，其组成及营养水平见表 1。

表 1 基础饲粮组成及营养水平(风干基础) Table 1 Composition and nutrient levels of basal diets (air-dry basis) 
1.3 饲养管理

动物试验在湖南农业大学耘园基地进行。采用3层笼养方式饲养，在饲养试验前对鸡舍和笼具进行清洗消毒，然后用福尔马林和高锰酸钾进行熏蒸、通风。入雏前将圈舍升温至32~35 ℃，此后温度每周降低2~3 ℃，直至保持在20~22 ℃；鸡舍相对湿度保持在50%~60%(预饲前3 d在65%以上)。日常管理参照《商品肉鸡生产技术规程》(GB/T 19664—2005)，先饮水后开食，自由采食和饮水。饲养过程中，注意监测环境空气质量，注意通风换气，保持良好的鸡舍环境；每天打扫鸡舍清洁卫生，并定期用专用消毒剂对鸡舍进行喷雾消毒。

1.4 测定指标及方法 1.4.1 生长性能

试验期间观察试验鸡健康情况，并记录死淘率，分别在肉鸡7和42日龄空腹称重，并准确计量试验阶段采食量，计量试验期肉鸡平均日增重(ADG)、平均日采食量(ADFI)和料重比(F/G)。

1.4.2 屠宰性能及肉品质

于42日龄，从每个重复中随机挑选1羽白羽肉鸡，屠宰后进行屠宰性能测定，测定方法参照NY/T 823—2004。分别取左右两侧胸肌和腿肌用于测定pH、肉色、滴水损失和系水力。pH采用MC Testo 205 pH测定仪测定，分别取屠宰后45 min和24 h的胸肌、腿肌3个点进行测定，取平均值为屠宰45 min后pH(pH45 min)和屠宰24 h后pH(pH24 h)；肉色用NR20XE肉色仪进行测定；取5 g左右肌肉置于滴水损失测定管中，于4 ℃保存，分别于24和48 h称重，计算24和48 h肌肉滴水损失；肌肉系水力则用肉品系水力测定仪MJ-1000进行测定。

1.4.3 血清生化指标

于42日龄，从每个重复中随机挑选1羽白羽肉鸡，颈静脉采血，4 000 r/min离心分离血清，-20 ℃保存待测。采用酶标仪测定血清中甘油三酯(TG)(单试剂GPO-PAP法)、总胆固醇(TC)(单试剂GPO-PAP法)、低密度脂蛋白胆固醇(LDL-C)(双试剂直接法)、高密度脂蛋白胆固醇(HDL-C)(双试剂直接法)和葡萄糖(GLU)(己糖激酶法)含量以及谷丙转氨酶(ALT)(赖氏法)、谷草转氨酶(AST)(赖氏法)活性。试剂盒均购自南京建成生物工程研究所。

1.5 数据统计分析

试验数据采用SPSS 20.0软件进行单因素方差分析(one-way ANOVA)，采用LSD法进行多重比较，P＜0.05为差异显著，P＞0.05为差异不显著。

2 结果与分析 2.1 饲粮添加乙酸钠对白羽肉鸡生长性能的影响

由表 2可知，与对照组相比，饲粮添加不同水平乙酸钠对白羽肉鸡ADG、ADFI和F/G均无显著影响(P＞0.05)，各乙酸钠添加组白羽肉鸡生长性能之间也均无显著差异(P＞0.05)。

表 2 饲粮添加乙酸钠对白羽肉鸡生长性能的影响 Table 2 Effects of dietary sodium acetate on growth performance of white-feathered broilers
2.2 饲粮添加乙酸钠对白羽肉鸡屠宰性能和肉品质的影响 2.2.1 饲粮添加乙酸钠对白羽肉鸡屠宰性能的影响

由表 3可知，与对照组相比，饲粮添加不同水平乙酸钠对白羽肉鸡屠宰率、半净膛率、全净膛率、胸肌率和腿肌率均无显著影响(P＞0.05)，各乙酸钠添加组白羽肉鸡屠宰性能之间也均无显著差异(P＞0.05)。

表 3 饲粮添加乙酸钠对白羽肉鸡屠宰性能的影响 Table 3 Effects of dietary sodium acetate on slaughter performance of white-feathered broilers 
2.2.2 饲粮添加乙酸钠对白羽肉鸡肉品质的影响

由表 4可知，与对照组相比，饲粮添加不同水平乙酸钠对白羽肉鸡胸肌亮度(L*)和黄度(b*)值、pH24 h以及24和48 h滴水损失均无显著影响(P＞0.05)，但饲粮添加0.2%、0.4%和0.5%乙酸钠可以显著降低胸肌pH45 min(P＜0.05)，0.1%和0.3%乙酸钠添加组胸肌pH45 min与对照组相比无显著差异(P＞0.05)；与对照组相比，饲粮添加0.1%、0.2%、0.3%和0.5%乙酸钠显著提高胸肌红度(a*)值(P＜0.05)，饲粮添加0.3%、0.4%和0.5%乙酸钠显著提高胸肌系水力(P＞0.05)，而饲粮添加0.1%和0.2%乙酸钠对胸肌系水力无显著影响(P＞0.05)。

表 4 饲粮添加乙酸钠对白羽肉鸡胸肌肉品质的影响 Table 4 Effects of dietary sodium acetate on breast muscle quality of white-feathered broilers

由表 5可知，与对照组相比，饲粮添加不同水平乙酸钠对白羽肉鸡腿肌pH45 min、pH24 h、亮度、红度和黄度值以及24和48 h滴水损失均无显著影响(P＞0.05)；饲粮添加0.3%、0.4%和0.5%乙酸钠显著提高腿肌系水力(P＜0.05)，饲粮添加0.1%和0.2%乙酸钠对腿肌系水力无显著影响(P＜0.05)。

表 5 饲粮添加乙酸钠对白羽肉鸡腿肌肉品质的影响 Table 5 Effects of dietary sodium acetate on leg muscle quality of white-feathered broilers
2.3 饲粮添加乙酸钠对白羽肉鸡血清生化指标的影响

由表 6可知，饲粮添加乙酸钠对白羽肉鸡血清TG、TC、LDL-C、HDL-C含量以及ALT活性存在显著影响(P＜0.05)。与对照组相比，0.4%和0.5%乙酸钠添加组血清TG含量显著提高(P＜0.05)，其中0.4%乙酸钠添加组血清TG含量最高，且显著高于0.1%、0.2%和0.3%乙酸钠添加组(P＜0.05)，0.5%乙酸钠添加组血清TG含量显著高于0.1%乙酸钠添加组(P＜0.05)。与对照组相比，0.1%、0.2%、0.4%和0.5%乙酸钠添加组血清TC含量显著提高(P＜0.05)，0.2%和0.5%乙酸钠添加组血清TC含量显著高于其他组。与对照组相比，各乙酸钠添加组血清LDL-C含量显著提高(P＜0.05)，其中0.2%和0.5%乙酸钠添加组血清LDL-C含量显著高于其他各组(P＜0.05)，0.4%乙酸钠添加组血清LDL-C含量显著高于0.1%乙酸钠添加组(P＜0.05)。0.2%、0.4%和0.5%乙酸钠添加组血清HDL-C含量显著高于对照组、0.1%和0.3%乙酸钠添加组(P＜0.05)，而0.1%和0.3%乙酸钠添加组血清HDL-C含量与对照组相比差异不显著(P＞0.05)，0.3%乙酸钠添加组血清HDL-C含量显著高于0.1%乙酸钠添加组(P＜0.05)。与对照组相比，0.4%和0.5%乙酸钠添加组血清ALT活性显著提高(P＜0.05)，0.1%、0.2%和0.3%乙酸钠添加组血清ALT活性无显著差异(P＞0.05)。与对照组相比，饲粮添加不同水平乙酸钠对白羽肉鸡血清GLU含量和AST活性无显著影响(P＞0.05)。

表 6 饲粮添加乙酸钠对白羽肉鸡血清生化指标的影响 Table 6 Effects of dietary sodium acetate on serum biochemical indices of white-feathered broilers
3 讨论 3.1 饲粮添加乙酸钠对白羽肉鸡生长性能的影响

动物的生长性能和采食量紧密相关，采食量的多少直接决定了养分摄入量，进而影响动物生长性能。目前有不少关于乙酸对动物生长性能和摄食影响的报道。Canibe等[10]报道，饲喂含不同乙酸含量的液体发酵饲料对仔猪的生长性能并无显著影响；张治国[11]报道，饲粮添加0.1%~0.4%乙酸对小鼠和大鼠的ADFI无显著差异；杨春雷等[12]报道，用醋酸酸化饲粮分别至pH为3.0、4.0和5.0后饲喂断奶仔猪，可以显著提高仔猪ADG和健康状况。但也有报道乙酸盐对试验动物采食量及ADG具有负面影响。武枫林等[13]报道，水牛正常条件下饲喂24 h后颈静脉分别灌注500 mL的1和2 mol/L乙酸钠，发现低水平乙酸钠在0~3 h和12~24 h阶段对水牛采食量有显著抑制作用，高水平乙酸钠则全天对水牛采食量有显著抑制作用。王云云等[14]报道，分别给昆明小鼠每天腹腔注射0.3和0.5 kg/L的乙酸钠，在4周内，小鼠的采食量、饲料转化率、增重率和绒毛发育程度被显著抑制，并且上调了厌食激素[胆囊收缩素(CCK)、瘦素(LEP)和酪酪肽(PYY)]和摄食调控因子[Janus激酶2/信号转导及转录激活蛋白3(JAK2/STAT3)] mRNA的表达。Frost等[15]报道，静脉和回肠输注醋酸盐(500 mg/kg BW)都可以抑制C57BL/6小鼠的食欲，降低小鼠采食量。Cuche等[16]给雌性大白猪回肠持续输注1 h(2.4 mL/min)含60%乙酸的复合短链脂肪酸(pH 6.8, 0.5 mmol/L)可以显著提高血浆中厌食激素PYY的含量，并且抑制胃排空，在输注完成后的15 min后血浆中PYY含量回归基础水平。本试验的结果与Canibe等[10]和张治国[11]的报道一致，饲粮添加0.1%~0.5%乙酸钠对白羽肉鸡生长性能无显著影响。关于乙酸钠对于试验动物采食量和ADG影响的研究结果存在差异，但也可以发现规律，在饲粮中添加适量的乙酸钠对试验动物生长性能无显著影响或促进，而对试验动物静脉输注或回肠输注乙酸钠则可以显著降低采食量及ADG。这可能与乙酸钠半衰期较短以及通过摄食摄入的乙酸可以被小肠上皮细胞迅速吸收代谢或经门静脉进入肝脏内代谢，最后才进入血液，血液中的乙酸含量不足以对动物采食造成影响有关。对试验动物直接静脉或回肠输注乙酸钠可以短时间内使动物血浆内乙酸含量升高，乙酸可以通过血脑屏障，在下丘脑神经元内转化为乙酰辅酶A。该过程会释放大量一磷酸腺苷(AMP)进而使腺苷酸活化蛋白激酶(AMPK)磷酸化，AMPK磷酸化进而磷酸化乙酰辅酶A羧化酶(ACC)，导致丙二酰辅酶A水平降低，下丘脑丙二酰辅酶A水平的降低与抑食因子POMC19表达的提高以及促食神经肽Y(NPY)和刺豚鼠相关蛋白(AgRP)表达抑制有关[15]。

3.2 饲粮添加乙酸钠对白羽肉鸡屠宰性能和肉品质的影响

肉鸡养殖的生产效益与肉鸡的屠宰性能和肉品质有直接关系，如何改善肉鸡的屠宰性能和肉品质日益受到关注。通过在饲粮中添加功能活性成分或新型饲料原料等营养调控手段来提高肉鸡胴体品质是常见的措施。本试验在了解了乙酸生物学功能之后，推测乙酸可能对肉鸡脂肪代谢产生影响，进而对肉鸡屠宰性能和肉品质产生影响。本试验结果发现，饲粮添加乙酸钠对白羽肉鸡屠宰性能并无显著影响，但对白羽肉鸡的肉品质有显著影响。即饲粮添加0.2%、0.4%和0.5%乙酸钠显著降低胸肌pH45 min；饲粮添加0.3%、0.4%和0.5%乙酸钠显著提高胸肌和腿肌系水力；饲粮添加0.1%、0.2%、0.3%和0.5%乙酸钠显著提升胸肌红度值。活体禽肉一般为中性偏碱的状态，屠宰后由于肌肉中肌糖原的无氧酵解生成乳酸，使pH迅速降低[17]。饲粮添加乙酸钠使白羽肉鸡肌肉pH下降的可能原因是乙酸进入体内会转化为乙酰辅酶A，乙酰辅酶A既可以作为底物直接参与三羧酸循环供能，减少肌糖原的消耗，也可以作为糖异生的底物生成GLU，使肌糖原增加。还有研究指出，营养干预会影响肌肉肌纤维的组成，肌肉肉品质和肌纤维的组成密切相关。Lebedová等[18]报道，限饲显著提高育肥猪肌肉ⅡB型肌纤维比例，显著降低Ⅰ型肌纤维比例。ⅡB型肌纤维直径大，占比越高肌纤维横截面积越大，系水力越低，肉质越差，而Ⅰ型肌纤维占比越高则红度越好，系水力越高[19]。也有报道指出，肌肉横截面积变大和肌糖原的减少相关[20]，故饲粮添加乙酸使白羽肉鸡肌肉红度质提高、系水力增强的一个可能原因是充足的营养供给对肉鸡肌肉的肌纤维组成产生了积极影响，提高了Ⅰ型肌纤维比例，降低了ⅡB型肌纤维比例，肌纤维横截面积变小，从而使肌肉红度值变高，系水力变强。

3.3 饲粮添加乙酸钠对白羽肉鸡血清生化指标的影响

短链脂肪酸对动物的生理活动具有重要影响，在维持机体能量平衡及代谢稳态、机体免疫调节以及脂肪代谢等方面具有重要作用。有研究指出，乙酸对动物脂肪代谢具有重要调控作用[21]。Jocken等[22]报道，1 μmol/L乙酸盐处理人多能脂肪源干细胞(hMADS)导致丝氨酸650位点磷酸化的激素敏感性脂肪酶(HSL)相对量减少，从而抑制了细胞脂解作用。Hong等[23]报道，乙酸盐处理小鼠前脂肪细胞系(3T3-L1)可以激活G蛋白偶联受体43(GPR43)，使氧化物酶体增殖物激活受体γ(PPARγ)的表达量提高，从而促进脂肪细胞的分化，同时还抑制异丙肾上腺素诱导的脂解作用。本试验探究了饲粮添加乙酸钠对白羽肉鸡血清中脂肪代谢相关生化指标的影响，结果表明乙酸钠的添加使白羽肉鸡血清中TG、TC、LDL-C和HDL-C的含量上升。血清中TG、TC、LDL-C和HDL-C的含量与机体脂肪代谢密切相关，脂肪摄入过高和机体脂肪沉积过多都有可能导致其含量升高[24]。乙酸钠的添加可能抑制了白羽肉鸡体内HSL诱导的或异丙肾上腺素诱导的脂解作用，并促进了脂肪细胞的分化，从而使肉鸡肝脏和机体脂肪沉积增加，进而影响了血清生化指标。另外，乙酸进入体内可以转化为乙酰辅酶A，可以作为脂肪合成的原料[25]，在肉鸡肝脏内可以直接参与脂肪的从头合成及胆固醇的从头合成，从而促进体脂沉积。乙酸还可以抑制肝X受体(LXR)的表达[21]，而LXR可以促进肝脏对HDL-C的吸收[26]，即饲粮添加适宜水平的乙酸钠可能通过抑制LXR表达，导致肝脏对HDL-C的吸收减少，从而使血清中HDL-C含量升高[26]。

在乙酸与胰岛素抵抗的研究上表明，乙酸可以缓解胰岛素抵抗。Kimura等[27]报道，乙酸可以改善小鼠肌肉及肝脏组织胰岛素敏感性，促进小鼠糖酵解及能量消耗相关基因的表达，增强小鼠对GLU的吸收利用。Mitrou等[28]报道，摄入乙酸可以改善GLU耐受量，降低患者骨骼肌胰岛素敏感性，增强骨骼肌对GLU的吸收和利用，降低血液中胰岛素含量。本研究中，饲粮添加乙酸钠并未显著影响白羽肉鸡血清GLU含量，即乙酸钠对正常白羽肉鸡血糖调节能力无显著影响。

ALT和AST是肝功能检测最常见的指标。ALT主要分布在肝细胞内，AST在肝细胞、心脏细胞和骨骼肌细胞均有分布，如果肝脏受损或损坏，肝细胞中的转氨酶便进入血液，血液中ALT和AST活性升高，提示肝脏疾病信号[29]。本试验中，饲粮添加0.4%和0.5%乙酸钠使白羽肉鸡血清中ALT活性显著上升，这说明饲粮添加0.4%和0.5%乙酸钠使肝脏受到了一定程度的损伤。

4 结论

综上所述，饲粮添加乙酸钠对白羽肉鸡生长性能和屠宰性能无显著影响，添加适宜水平的乙酸钠可以一定程度改善肉质，但过量添加可能会使血脂升高、肝脏受损。其中，饲粮添加0.3%乙酸钠改善了白羽肉鸡肌肉红度值和系水力，但对血清TG、TC和HDL-C含量无显著影响，并且未导致肝损伤，是较为适宜的添加水平。

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