不同饲料效率与绵羊瘤胃组织形态学关系

张德印，张小雪，李发弟,2，李冲,2，李国泽，张煜坤，李晓龙，宋其志，赵源，刘晓青，马亮强，王维民

不同饲料效率与绵羊瘤胃组织形态学关系

张德印1，张小雪1，李发弟1,2，李冲1,2，李国泽1，张煜坤1，李晓龙1，宋其志1，赵源1，刘晓青1，马亮强1，王维民1

（1甘肃农业大学动物科学技术学院，兰州 730030；2甘肃省肉羊繁育生物技术工程实验室，甘肃民勤 733300）

【】利用单栏系统测定个体的饲料效率相关性状与瘤胃组织形态学指标，探讨绵羊饲料效率与瘤胃组织形态的关系，为解析绵羊饲料效率性状的影响因素研究提供基础数据。随机选取出生日龄相近、系谱信息详细、健康状况良好的187湖羊公羔，56 d断奶后转入单栏饲养，过渡期14 d，预饲期10 d，正试期100 d。正试期内所有羊只仅饲喂颗粒饲料，自由采食及饮水，并在80 d和180 d晨饲前空腹测定其体重（body weight，BW）和80—180 d间的采食量（feed intake，FI），计算平均日增重（average daily gain，ADG）、中期代谢体重（metabolic body weight, MBW）、饲料转化率（feed conversion rate，FCR）和剩余采食量（residual feed intake，RFI）等饲料效率相关性状并对其进行描述性统计，于180 d饲养结束后屠宰采集瘤胃腹囊组织1 cm2保存于4%甲醛溶液中，用于制作组织切片并观测其瘤胃乳头长度、宽度和肌层厚度。最后将其与饲料效率相关性状进行相关分析和方差分析。饲料效率相关性状的变异系数均大于10%，且剩余采食量最大与最小的个体每天的剩余采食量之差达0.57 kg。饲料效率相关性状间的表型相关分析表明剩余采食量与饲料转化率（r= 0.68）和采食量（r= 0.48）呈极显著正相关（＜0.01），与初始体重（r=0）、末期体重（r= -0.01）和平均日增重（r= -0.02）无显著相关（＞0.05）。饲料效率相关性状与瘤胃组织形态相关性分析发现，瘤胃乳头长度与平均日增重、采食量、初始体重和末期体重呈显著或极显著正相关（＜0.05或＜0.01），肌层厚度与平均日增重、采食量和末期体重呈显著或极显著正相关（＜0.05或＜0.01），而剩余采食量和饲料转化率与瘤胃组织形态无显著相关。不同RFI组羔羊采食量、饲料转化率和瘤胃肌层厚度存在显著或极显著差异（0.05或＜0.01），瘤胃乳头长、宽无显著差异（＞0.05），其中High-RFI组羔羊采食量和饲料转化率极显著高于Low-RFI组（＜0.01），肌层厚度显著高于Medium-RFI组（＜0.05）；不同FCR组羔羊的剩余采食量、采食量、ADG、初始体重、末期体重和乳头长度存在显著或极显著差异（＜0.05或＜0.01），肌层厚度和乳头宽度差异不显著（＞0.05），其中High-FCR组羔羊剩余采食量、采食量、ADG、初始体重和末期体重均显著或极显著高于Low-FCR组（＜0.05或＜0.01），Medium-FCR组羔羊乳头长度显著长于Low-FCR组（＜0.05）；除瘤胃乳头宽度外，不同FI组羔羊的上述指标均存在显著或极显著差异（＜0.05或＜0.01），且High-FI组羔羊的剩余采食量、饲料转化率、ADG、初始体重、末期体重、肌层厚度和乳头长度均显著或极显著高于Low-FI组（＜0.05或＜0.01）；不同ADG组羔羊采食量、饲料转化率、初始体重、末期体重和肌层厚度均存在显著或极显著差异（＜0.05或＜0.01），乳头长度和乳头宽度无显著差异（＞0.05），其中High-ADG组羔羊采食量、剩余采食量、初始体重、末期体重和肌层厚度均显著或极显著高于Low-ADG组，饲料转化率则极显著低于Low-ADG组。剩余采食量与采食量和饲料转化率等饲料效率性状呈极显著正相关，表明其可作为衡量饲料效率的潜在指标。剩余采食量和饲料转化率与瘤胃组织形态学指标无显著相关，采食量和平均日增重与瘤胃乳头长度和肌层厚度呈显著正相关，表明羔羊瘤胃组织形态对采食量和增重有显著影响，但其进一步的作用机制有待深入研究。

剩余采食量；饲料转化率；瘤胃；组织形态；湖羊

0 引言

【研究意义】在肉羊生产实践中，饲草料成本约占总成本的65%—70%，因此提高饲料效率对经济具有重要的意义。在畜禽生产中，饲料效率通常被定义为动物将饲料转化为产品的相对能力，目前饲料转化率（feed conversion rate，FCR）和剩余采食量（residual feed intake，RFI）作为衡量饲料效率最常用的指标[1-3]，但剩余采食量仍处于探讨与研究的阶段，因此需要更进一步地评价其作为衡量饲料效率指标的科学性。【前人研究进展】1963年，KOCH等[4]首次提出了剩余采食量（residual feed intake，RFI）作为估测畜禽饲料利用效率的指标，是指畜禽实际采食量与预期的根据生产性能（体增重、产奶量和产蛋数等）需要和维持体重需要的标准而计算得出的采食量之差。RFI反映的是畜禽本身由遗传背景决定的代谢差异而导致的饲料利用效率的差异[5]，其与畜禽的体型大小及生产性能，甚至是屠宰性能和肉品质等性状相互独立，计算过程中既考虑了畜禽的体增重，也校正了其代谢体重。在对RFI进行遗传改良的同时，不会对生长及生产性状造成不良影响或影响很小[6-7]。因此，RFI可作为评价饲料效率的潜在育种指标。目前有关RFI的研究主要集中在猪[8-9]、牛[10-11]和禽[12-13]上，有关绵羊RFI的研究较少。【本研究切入点】瘤胃是反刍动物特有的消化器官[14]，瘤胃乳头高和乳头宽等形态学结构，决定了瘤胃上皮对养分吸收和离子的转运能力[15]。而养分吸收和利用的效率决定动物饲料效率的高低。目前有关瘤胃形态学的研究主要集中在不同生长时期[16-18]、不同饲料类型和结构[19]、以及不同断奶时间[20]对瘤胃发育的影响，但不同饲料效率羔羊瘤胃组织形态与饲料效率的关系的研究报道较少。【拟解决的关键问题】本研究以湖羊公羔为研究对象，利用单栏系统测定个体的采食量、剩余采食量、饲料转化率、平均日增重（average daily gain，ADG）等饲料效率相关的性状，并观测瘤胃组织形态学指标，探讨绵羊饲料效率与瘤胃组织形态的关系，为解析绵羊饲料效率性状的影响因素研究提供基础数据。

1 材料与方法

1.1 试验群体与饲养管理

试验于2018年5—9月在甘肃民勤勤锋滩进行，所有试验羊只是从金昌中天羊业有限公司（甘肃，金昌）随机选取187只系谱信息详细、出生日期相近、身体健康、发育状态良好的湖羊公羔，56 d断奶后转于民勤县德福农业科技有限公司（甘肃，民勤）进行单栏饲养，每个栏位装有独立的水槽和料槽，在进行试验前按羊场常规程序对羊只进行免疫和驱虫，根据羊场饲喂方式，每天饲喂4次，试验羊只自由采食和饮水，并对羊舍每14 d进行一次消毒。试验期包括57—70 d的过渡期14 d，在过渡期间每天增加7.1%的全价颗粒饲料以代替羔羊料；71—80 d的预饲期，10 d；81—180 d的正试期，在正试期所有羊只均饲喂全价颗粒料。分别测定80—180 d期间的采食量、80 d和180 d体重，体重在晨饲前空腹测定。饲养试验结束后，立即屠宰采集瘤胃腹囊组织1 cm2保存于4%甲醛溶液中，用于后续制作组织切片。

1.2 试验方法

1.2.1 剩余采食量（residual feed intake，RFI）的计算 本试验的预测采食量是通过试验羊只的实际日采食量（AFI）与平均日增重（ADG）和平均中期代谢体重（MBW）多元回归模型来计算，其中ADG和MBW被作为固定效应，所用计算方法参照莫负涛[21]构建的回归模型：

ADG=(BW180-BW80)/N，MBW=[1/2×(BW180+ BW80)]0.75，Yi=β0+β1(ADGi)+β2(MBWi)+ei，FCR=FI/（BW180-BW80），其中，ADG为平均日增重，MBW为平均中期代谢体重（W0.75），BW80为试验初始体重，BW180为试验末期体重，FI为采食量，N为饲养天数，Yi表示动物i的实际干物质采食量，β0表示回归截距，β1为固定值，表示ADG对采食量的影响程度，β2表示MBW对采食量的影响程度，为定值。ei表示第i只动物的随机误差，即RFI=实际采食量-预测采食量。

1.2.2 试验分组与统计分析 根据个体RFI对试验群体进行排序，将试验群体按平均值和标准差分为High-RFI组（High＞0.05）、Medium-RFI组（-0.05≤Medium≤0.05）和Low-RFI组（Low＜-0.05）3组。

根据个体ADG对试验群体进行排序，将试验群体按平均值和标准差分为High-ADG组（High＞0.29）、Medium-ADG组（0.26≤Medium≤0.29）和Low-ADG组（Low＜0.26）3组。

根据个体FI对试验群体进行排序，将试验群体按平均值和标准差分为High-FI组（High＞165.82）、Medium-FI组（144.98≤Medium≤165.82）和Low-FI组（Low＜144.98）3组。

根据个体FCR对试验群体进行排序，将试验群体按平均值和标准差分为High-FCR组（High＞6.06）、Medium-FCR组（5.48≤Medium≤6.06）和Low-FCR组（Low＜5.48）3组。

1.2.3 切片制作与数据测定 参考温蕾等[22]的石蜡切片制作过程制作瘤胃组织切片。在进行石蜡包埋、切片、苏木精-伊红染色后，选择3—5张切片，每张选5个典型视野（组织完整），采用Image-Pro Express 6.0图像分析系统软件分别测量瘤胃腹囊乳头长度和宽度以及瘤胃肌层的厚度。

1.3 数据处理

利用SPSS 16.0软件和R语言（版本3.6.1）对测得的数据进行分析，结果用平均值±标准差表示，采用Tukey法进行多重比较，统计结果以＜0.05为差异显著，＜0.01为差异极显著；对饲料效率相关性状及其与瘤胃组织形态进行皮尔逊相关性分析，并使用corrplot和pheatmap包作图。

2 结果

2.1 饲料效率相关性状描述性统计量

试验测定了试验羊只80—180 d期间的采食量和80 d体重和180 d体重，分别计算剩余采食量、饲料转化率、平均日增重等相关性状结果如表1所示。发现剩余采食量最高和最低个体每天的剩余采食量之差达0.57 kg，其次各性状的变异系数均大于10%，且初始体重的变异系数最大。

2.2 饲料效率相关性状的相关性分析

相关性分析结果表明剩余采食量与平均日增重、初始体重和末始体重无显著相关，但与采食量（r=0.48）和饲料转化率（r=0.68）呈极显著正相关（＜0.01），而且采食量与平均日增重（r = 0.73）、初始体重（r = 0.87）和末期体重（r = 0.73）高度相关，与饲料转化率（r = 0.45）呈中等相关（＜0.01）。饲料转化率与平均日增重呈极显著负相关（r=-0.28，＜0.01，图1）。

2.3 羔羊瘤胃组织形态及其与饲料效率相关性状的相关性分析

由图2可知，不同饲料效率羔羊瘤胃的肌层厚度和乳头长度存在一定差异，并与饲料效率性状关联分析发现剩余采食量和饲料转化率与瘤胃乳头宽度、长度以及肌层厚度的相关程度不高，但平均日增重、采食量和末期体重与瘤胃乳头长度和肌层厚度呈显著正相关，而初始体重仅与乳头长度呈显著正相关（图3）。

2.4 不同剩余采食量羔羊瘤胃组织形态学

由表2可知，不同RFI组羔羊的平均日增重、初始体重、末期体重、乳头长度和乳头宽度均无显著差异（＞0.05），但采食量、饲料转化率和瘤胃肌层厚度存在显著或极显著差异（＜0.05或＜0.01），其中High-RFI组羔羊的采食量、饲料转化率极显著高Medium-RFI和Low-RFI组（＜0.01），并且High-RFI组羔羊瘤胃腹囊组织肌层厚度显著高于Medium-RFI组羔羊（＜0.05），但与Low-RFI组羔羊无显著差异（＞0.05）。

表1 饲料效率相关性状的描述性统计

每个圆的大小表示相关系数的绝对值。蓝色和红色梯度分别表示正相关或负相关。**表示差异极显著（P＜0.01），*表示差异显著（P＜0.05）

a：低饲料效率组；b：中饲料效率组；c：高饲料效率组 a: Low feed efficiency group; b: Medium feed efficiency group; c: High feed efficiency group

2.5 不同日增重羔羊瘤胃组织形态学

由表3可知，在不同日增重组羔羊中，采食量、饲料转化率、初始体重、末期体重和肌层厚度存在显著差异（＜0.05），其他指标在3组间均无显著差异（＞0.05），High-ADG组羔羊的采食量和末期体重极显著高于Medium-ADG和Low-ADG组（＜0.01）；High-ADG组羔羊的饲料转化率极显著低于Medium- ADG和Low-ADG组（＜0.01）；但High-ADG组羔羊瘤胃腹囊组织肌层厚度显著高于Low-ADG组羔羊（＜0.05）。

蓝色和红色梯度分别表示正相关或负相关。**表示差异极显著（P＜0.01），*表示差异显著（P＜0.05）

表2 不同剩余采食量羔羊瘤胃组织形态

同列中数值标注不同小写字母表示差异显著（＜0.01）；不同大写字母表示差异极显著（＜0.05）。下同

In the same column, different lowercase letters represent significant differences (＜0.05), different capital letters represent extremely significant differences (＜0.01). The same as below

表3 不同日增重羔羊瘤胃组织形态

2.6 不同采食量羔羊瘤胃组织形态学

由表4可知，与饲料效率相关的剩余采食量、饲料转化率、平均日增重、初始体重和末期体重在不同采食量组中均存在极显著差异（＜0.01），且High-FI组极显著高于Medium-FI和Low-FI组。在不同采食量羔羊瘤胃组织形态学中，High-FI组羔羊瘤胃腹囊组织肌层厚度显著高于Low-FI组羔羊（＜0.05），High-FI和Medium-FI组羔羊瘤胃腹囊组织乳头长度极显著高于Low-FI组羔羊（＜0.01），但乳头宽度无显著差异（＞0.05）。

表4 不同采食量羔羊瘤胃组织形态

2.7 不同饲料转化率羔羊瘤胃组织形态学

由表5可知，不同饲料转化率组羔羊的剩余采食量、采食量、平均日增重、初始体重、末期体重以及瘤胃腹囊组织乳头长度存在显著差异（＜0.05），肌层厚度和乳头宽度无显著差异（＞0.05）。其中，High- FCR组羔羊的RFI、FI、Initial BW极显著高于Medium-和Low-FCR组羔羊（＜0.01）；Medium-和Low-FCR组羔羊的平均日增重极显著高于High-FCR组（＜0.01）；并且Medium-FCR组羔羊的末期体重和瘤胃腹囊组织乳头长度显著长于Low-FCR组羔羊（＜0.05）。

表5 不同饲料转化率羔羊瘤胃组织形态

3 讨论

饲料效率是衡量饲料利用率的主要指标，当饲料效率较低时，会使饲养成本增加，因此提高饲料效率显得尤为重要。并且瘤胃是反刍动物特有的消化器官[23-24]，在动物机体的消化代谢过程中具有极其重要的作用，是反刍动物健康生长的基础。在瘤胃形态学研究中，瘤胃乳头长度是最重要的指标，其次是瘤胃乳头宽度和肌层厚度[25]。剩余采食量是一个具有中等遗传力的负向选择性状，遗传力为0.18—0.43[26-27]，是衡量饲料利用效率的一个重要指标。有学者对畜禽剩余采食量的研究中，发现剩余采食量与采食量、消化率、体组织代谢、活动量、体温调节等生理因素有密切关系[28-29]。本研究对不同饲料效率羔羊瘤胃组织形态的研究结果显示，按RFI值分组后，发现在同样的饲喂条件下Low-RFI组羔羊的FI和FCR极显著低于Medium-RFI和High-RFI组，且不同组间的生长性能如ADG、初始体重、末期体重均无显著差异，这与莫负涛[21]和MCGEE等[30]的研究结果相一致。其次发现High-RFI组羔羊瘤胃腹囊组织肌层厚度显著高于Medium-RFI组羔羊，但瘤胃乳头长度和宽度在不同组间也无显著差异这与梁玉生[31]的研究结果相一致。表明对RFI的选择不会影响瘤胃乳头的发育，进而不会影响个体的生长性能。此外，本研究按平均日增重(ADG)、采食量（FI）、饲料转化率(FCR)等影响饲料效率的重要性状对试验群体进行分组，结果表明不同ADG羔羊的采食量、饲料转化率、初始体重、末期体重、瘤胃肌层厚度存在显著差异，其中High-ADG组羔羊的饲料转化率极显著低于Medium-ADG和Low-ADG组，但High-ADG组羔羊瘤胃肌层厚度显著高于Low-ADG组羔羊，表明瘤胃肌层厚度可能会影响饲料效率。饲料相关性状在不同FI组均存在极显著差异，并且High-FI羔羊瘤胃肌层厚度和乳头长度均显著高于Low-FI羔羊，可能与采食量的增多可提高瘤胃的运动水平，从而促进瘤胃肌层厚度的发育有关，这与朱文涛等[32]等的研究表明饲料的物理刺激是影响瘤胃肌层发育的主要因素相符；不同FCR组羔羊瘤胃乳头长度以及饲料效率相关的性状均存在显著差异，其中Medium-FCR组羔羊瘤胃乳头长度显著高于Low-FCR组羔羊，与High-FCR组无显著差异，但Medium-和Low-FCR组羔羊的平均日增重极显著高于High-FCR组；表明羔羊瘤胃组织形态的发育有利于提高饲料效率，特别是瘤胃乳头长度和肌层厚度，但其进一步作用机理还有待深入研究。

4 结论

本研究结果表明剩余采食量与生长性状无显著相关，与采食量和饲料转化率呈显著正相关，且Low-RFI组羔羊饲料转化率极显著低于High-RFI组，表明RFI可作为评价饲料效率的潜在指标；剩余采食量和饲料转化率与瘤胃组织形态学指标无显著相关，采食量和平均日增重与瘤胃乳头长度和肌层厚度呈显著正相关，表明羔羊瘤胃组织形态对采食量和增重有显著影响，但其进一步的作用机制有待深入研究。

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Association of Rumen Histomorphology of Sheep with Different Feed Efficiencies

ZHANG DeYin1, ZHANG XiaoXue1, LI FaDi1,2, LI Chong1,2, LI GuoZe1, ZHANG YuKun1, LI XiaoLong1, SONG QiZhi1, ZHAO Yuan1, LIU XiaoQing1, MA LiangQiang1, WANG WeiMin

(1College of Animal Science and Technology, Gansu Agricultural University, Lanzhou 730070;2Engineering Laboratory of Sheep Breeding and Reproduction Biotechnology in Gansu Province, Minqin 733300)

【】The individual pens was used to determine individual feed efficiency-related traits and rumen morphology indexes, and the association of feed efficiency of sheep and rumen histomorphology was discussed, so as to provide fundamental data for analyzing the influencing factors of sheep feed efficiency traits. 【】One hundred and eighty-seven Hu lambs with the similar birthday age, good growth and available pedigrees were selected randomly, and all lambs were transferred to the housed indoors in individual pens after weaning at 56 days, the lambs were subjected to a 14 days adaptation period. The pre-test period was 10 days and the experimental period was 100 days, during which all lambs were fed pellet feed and had free access to food and fresh drinking water. Lambs were weighed before feeding in the morning at 80 and 100 days, and feed intake (FI) were measured during 80-180 days. Average daily gain (ADG), metabolic body weight (MBW), feed conversion rate (FCR) and residual feed intake (RFI) were calculated and the descriptive statistics were carried out. The lambs were slaughtered at 180 days, and rumen abdominal sac tissue was collected, and stored in 4% formaldehyde solution for making tissue sections. The length, width and muscle thickness of the rumen papilla were observed. Finally, correlation analysis and variance analysis were carried out for the traits related to feed efficiency.【】The variation coefficients of feed efficiency-related traits were all greater than 10%, and the difference of the individuals with the largest and smallest residual feed intake was 0.57 kg per day. Phenotypic correlation analysis of feed efficiency-related traits showed that RFI was very significantly positively correlated with FCR (r= 0.68) and FI (r= 0.48) (＜0.01), there was no significant correlation with initial body weight (r=0) final body weight (r= -0.01) and average daily gain (r= -0.02) (＞0.05). The correlation analysis between feed efficiency and rumen histomorphology was found that the length of the rumen papilla was significantly or very significantly positively correlated with average daily gain, feed intake, initial body weight and final body weight (＜0.05 or＜0.01), while there were no significant differences in length and width of rumen papilla (＞0.05). The feed intake and feed conversion rate of lambs in the High-RFI group were significantly higher than those in the Low-RFI group (＜0.01), and the muscle thickness was significantly higher than that of the Medium-RFI group (＜0.05). There were significantly or extremely significantly differences in residual feed intake, feed intake, ADG, initial body weight, final body weight and the length of rumen in different FCR groups (＜0.05 or＜0.01), there was no significant difference between the rumen muscular thickness and the width of rumen papilla (＞0.05). Among them, the residual feed intake, feed intake, ADG, initial body weight and final body weight of the lambs in the High-FCR group were significantly or extremely significantly higher than those in the Low-FCR group (＜0.05 or＜0.01), The length of the rumen papilla in the medium-FCR group was significantly longer than that in the Low-FCR group (＜0.05). There were significant or extremely significant differences in the above indexes of the lambs in different FI groups (＜0.05 or＜0.01), and the residual feed intake, feed conversion rate, ADG, initial body weight, final body weight, muscle thickness and the length of the rumen papilla in the High-FI group were significantly or extremely significantly higher than those in the Low-FI group (＜0.05 or＜0.01). There were significant or extremely significant differences in feed intake, feed conversion rate, initial body weight, final body weight and muscle thickness in different ADG groups (＜0.05 or＜0.01), there was no significant difference between the length and the width of the rumen papilla (＞0.05), the feed intake, residual feed intake, initial body weight, final body weight and muscle thickness of the High-ADG group were significantly or extremely significantly higher than those of the Low-ADG group, and the feed conversion rate was significantly lower than that of the Low-ADG group.【】There was a significant positive correlation between residual feed intake and the traits related to feed efficiency such as feed intake and feed conversion rate, indicating that it could be used as a potential index to measure feed efficiency. There was no significant correlation between the residual feed intake and feed conversion rate and the rumen histopathology. Feed intake and average daily gain were significantly positively correlated with the length of the rumen papilla and the muscular thickness, indicating that the morphology of the rumen tissue had significant effects on feed intake and body weight gain. However, the mechanism of action remains to be further studied.

residual feed intake; feed conversion rate；rumen; histomorphology; Hu sheep

10.3864/j.issn.0578-1752.2020.24.014

2020-01-02；

2020-09-05

国家自然科学基金（31560625）、国家自然科学基金（31760651）、国家畜禽良种联合攻关计划（125D0101）、国家肉羊产业技术体系（CARS-38）

张德印，E-mail：1547767138@qq.com。通信作者王维民，E-mail：wangwm@gsau.edu.cn

（责任编辑 林鉴非）