动物营养学报    2022, Vol. 34 Issue (1): 422-431    PDF    
哺乳期补饲开食料对牦牛犊牛生长性能、腹泻频率和发病频率的影响
郭文杰 , 刘书杰 , 冯宇哲 , 孙璐 , 崔占鸿     
青海大学畜牧兽医科学院, 青海省牦牛工程技术研究中心, 青海省高原放牧家畜动物营养与饲料科学重点实验室, 西宁 810016
摘要: 本试验旨在探究哺乳期补饲开食料对牦牛犊牛生长性能、腹泻频率和发病频率的影响。选取1月龄、体重相近的20头牦牛犊牛,随机分为试验组和对照组,每组10个重复,每个重复1头牛。在第1~100天,试验组补饲开食料,对照组不补饲开食料;在第101~150天,试验组和对照组饲喂相同的饲粮。测定牦牛犊牛的采食量、体重和体尺,并计算腹泻频率和发病频率。结果表明:1)在第1~50天和第51~100天,试验组牦牛的干物质采食量、粗蛋白质采食量和粗脂肪采食量显著高于对照组(P < 0.05),而中性洗涤纤维采食量和酸性洗涤纤维采食量显著低于对照组(P < 0.05);在第101~150天,2组采食量无显著差异(P>0.05)。2)在第50、100和150天,试验组牦牛的体重显著高于对照组(P < 0.05);在第1~50天,试验组牦牛平均日增重与对照组无显著差异(P>0.05);在第51~100天和第101~150天,试验组牦牛平均日增重显著高于对照组(P < 0.05);在第101~150天,试验组料重比显著低于对照组(P < 0.05)。3)在第50天,试验组牦牛的体高、胸围和管围显著高于对照组(P < 0.05);在第100天,试验组牦牛的胸围和管围显著高于对照组(P < 0.05);在第150天,试验组牦牛的体高和管围显著高于对照组(P < 0.05)。4)在第51~100天,试验组牦牛粪便评分显著低于对照组(P < 0.05);在第1~50天和第51~100天,试验组牦牛腹泻频率和发病频率显著低于对照组(P < 0.05);在第101~150天,试验组和对照组牦牛均无发病情况。综上所述,哺乳期补饲开食料可促进牦牛犊牛生长发育,降低腹泻频率,减少发病情况,并且有利于牦牛犊牛后期的生长发育。
关键词: 开食料    牦牛犊牛    生长性能    腹泻    
Effects of Starter Feed on Growth Performance, Diarrhea Frequency and Incidence Frequency of Yak Calves during Lactation
GUO Wenjie , LIU Shujie , FENG Yuzhe , SUN Lu , CUI Zhanhong     
Key Laboratory of Plateau Grazing Animal Nutrition and Feed Science of Qinghai Province, Yak Engineering Technology Research Center of Qinghai Province, Qinghai Academy of Animal Husbandry and Veterinary Sciences, Qinghai University, Xining 810016, China
Abstract: The study aimed to investigate the effects of starter feed on growth performance, diarrhea frequency and incidence frequency of yak calves during lactation. Twenty 1-month-old yak calves with similar body weight were evenly randomized divided into test group and control group. There were ten replicates in each group and one yak in each replicate. During days 1 to 100, test group was supplemented with starter feed, while control group was not supplemented with starter feed. Test group and control group were fed the same diet during days 101 to 150. The feed intake, body weight and body size of yak calves were measured, and the frequency of diarrhea and incidence were calculated. The results showed as follows: 1) the dry matter intake, crude protein intake and crude fat intake of yaks of test group during days 1 to 50 and days 51 to 100 were significantly higher than those of control group (P < 0.05), while the neutral detergent fiber intake and acid detergent fiber intake were significantly lower than those of control group (P < 0.05); there was no significant difference in feed intake between the two groups during days 101 to 150 (P>0.05). 2) On day 50, 100 and 150, the body weight of yaks of test group was significantly higher than that of control group (P < 0.05); there was no significant difference in the average daily gain between test group and control group during days 1 to 50 (P>0.05); but the average daily gain of test group was significantly higher than that of control group during days 51 to 100 and days 101 to 150 (P < 0.05); the ratio of feed to weight of test group was significantly lower than that of control group during days 101 to 150 (P < 0.05). 3) On day 50, body height, heart girth and cannon circumference of test group were significantly higher than those of control group (P < 0.05); on day 100, heart girth and cannon circumference of test group were significantly higher than those of control group (P < 0.05); on day 150, body height and cannon circumference of test group were significantly higher than those of control group (P < 0.05). 4) The yak feces score of test group was significantly lower than that of control group during days 51 to 100 (P < 0.05); the diarrhea frequency and incidence frequency of yaks of test group were significantly lower than those of control group during days 1 to 50 and days 51 to 100 (P < 0.05); there was no incidence of yak of test group and control group during days 101 to 150. In conclusion, starter feed can promote the growth and development of yak calves during lactation, reduce the frequency of diarrhea and the incidence of disease, and is conducive to the growth and development of yak calves in the later period.
Key words: starter feed    yak calves    growth performance    diarrhea    

牦牛是青藏高原上的特色反刍家畜之一,与当地经济、文化和生态环境等息息相关[1-3]。牦牛犊牛是牦牛产业持续高质量发展的基础。幼龄时期是生长发育的关键期,犊牛生长发育好坏对后期发育质量和生产性能水平具有重要影响[4]。牦牛产犊季节在每年的4~6月,高原上9月中下旬牧草开始迅速枯萎,质量明显降低[5],导致带犊母牦牛的泌乳量不能满足犊牛的生长需要[6-7]。营养缺乏不利于犊牛的生长发育,后期可能会形成僵牛,生长发育停滞[8],在冬春季节犊牛也会因营养缺乏、免疫力低下而体况衰竭造成死亡,产生重大经济损失[9-10]。加之牧民对散养犊牛的管理粗放及当地牦牛犊牛的培育技术未成系统,先进技术和管理方式的普及受到限制,会造成牦牛犊牛繁殖成活率低、犊牛生长发育不良、生长周期过长等[11-12]。这些问题一直制约着牦牛产业的发展。如果要实现突破,有必要对现有的技术体系及管理模式加以总结和改进。有研究者开展了牦牛犊牛人工代乳及补饲的初步研究[13-16],但对人工代乳时早期补饲开食料的营养调控研究的报道较少,早期适当补饲开食料可为牦牛犊牛提供充足的营养物质,减少断奶应激,是牦牛犊牛早期断母乳成功实施的关键因素之一,并可以刺激消化道的发育,有利于牦牛后期的生长发育。因此,本试验旨在探究在饲喂代乳粉和粗料的基础上补饲开食料此种培育方式对哺乳期牦牛犊牛生长性能的影响,以期为开食料在牦牛犊牛饲喂上的合理使用提供参考依据。

1 材料与方法 1.1 试验动物与分组

选取1月龄[(30±3) d]、体重相近、健康的20头牦牛犊牛作为试验动物,随机分为2组,试验组和对照组各10头牦牛。预试期30 d,正试期从2020年8月15日至2021年1月11日共计150 d。在青海省海北州海晏县高原现代生态畜牧业科技试验示范园进行饲养试验,该试验基地位于东经100°96′和北纬36°92′范围内,海拔为3 010 m,年平均温度为1.5 ℃。

1.2 试验饲粮

在第1~100天,对照组牦牛饲喂代乳粉和苜蓿干草,试验组牦牛饲喂代乳粉、苜蓿干草和开食料。2组每天代乳粉饲喂量相同,对照组饲喂的苜蓿干草和试验组饲喂的苜蓿干草+开食料的干物质相同。在第101~150天,试验组和对照组停止饲喂代乳粉,饲喂相同量的苜蓿干草+燕麦干(1 ∶ 1)和精料,干草和精料比为7 ∶ 3。代乳粉和开食料购自于北京精准动物营养研究中心,代乳粉主要由全脂奶粉、乳清粉、浓缩蛋白、生物素、烟酸、微量元素、赖氨酸、蛋氨酸、维生素A、维生素D、维生素E等组成,开食料主要由玉米、豆粕、膨化大豆、麸皮、乳清粉、细石粉、预混料、脂肪粉、磷酸氢钙、食盐等组成。精料购自于青海河湟青牧饲料科技开发有限公司,主要由玉米、麸皮、豆粕、钙、磷、氯化钠、微量元素铜、铁、锌、锰、硒、碘、钴等组成。原料营养成分见表 1

表 1 原料营养成分(干物质基础) Table 1 Nutrient components of raw materials (DM basis)  
1.3 饲养管理

代乳粉分早、中、晚3次饲喂。代乳粉和温水(煮沸冷却到42 ℃左右)按1 ∶ 5的质量比进行混合搅拌均匀,倒入奶瓶中,放置在奶瓶架上,犊牛主动进行吸吮。牦牛犊牛经过30 d的预饲逐渐适应代乳粉、苜蓿干草,试验组牦牛也适应了开食料。正式饲喂试验开始时代乳粉饲喂量为480 g/d,代乳粉每5 d增加12 g。对照组开始时苜蓿干草饲喂量为0.25 kg/d,每5 d增加57.5 g。饲粮组成及营养水平见表 2,在第1~50天,试验组苜蓿干草和开食料干物质按2 ∶ 1的比例进行饲喂;在第51~100天,根据实际情况,调整苜蓿干草和开食料干物质按1 ∶ 1的比例进行饲喂;在第101~150天,试验组和对照组饲喂相同量的苜蓿干草+燕麦干草(1 ∶ 1)和精料。试验牛实行单栏饲养,可在室内牛圈和室外牛圈进行活动,有足够的空间和阳光照射,自由饮水。每周对牛圈进行打扫及消毒。

表 2 饲粮组成及营养水平(干物质基础) Table 2 Composition and nutrient levels of diets (DM basis)  
1.4 指标测定 1.4.1 采食量和体重

在饲养试验过程中,每天记录每头试验牦牛的代乳粉饲喂量及固体饲粮的给料量和剩料量,计算干物质采食量(DMI)和粗蛋白质采食量(CPI)、粗脂肪采食量(EEI)、中性洗涤纤维采食量(NDFI)和酸性洗涤纤维采食量(ADFI)。在正式饲养试验开始前、第50天、第100天和结束时对每头牦牛犊牛进行体重测定。在早晨饲喂前进行称重,记录体重数据,分别计算各阶段试验组和对照组牦牛犊牛平均日增重(ADG)和料重比(F/G)。

1.4.2 体尺

在饲养试验的第50天、第100天和结束时对牦牛犊牛进行体尺测量。用卷尺和测仗测定牦牛犊牛的体高、体斜长、胸围和管围。体高是由耆甲最高点至地面的垂直距离。体斜长是由肩端至坐骨端的距离。胸围是由肩胛骨后角垂直体轴绕胸一周的周长。管围是管骨最细处的周长,在左前腿胫骨由下向上1/3处。

1.4.3 腹泻频率

试验开始后每天观察犊牛的排粪情况,参照Lee等[9]的方法对粪便进行评分,评分标准为:形态正常,外观较硬,评分1分;形态成型,外观较软,评分2分;形态不成型,外观呈水样,评分3分;形态不成型,外观呈水样、黏液附着少量血丝,评分4分;形态不成型,外观呈水样、黏液附着大量血丝,评分5分。每天记录每头牛的评分。当粪便被评为3分及以上时则判定为腹泻。腹泻发生时遵循兽医给出的治疗方法进行治疗。腹泻频率计算公式如下:

1.4.4 发病频率

在饲养试验期间,每天观察犊牛的健康情况,若有流鼻涕、咳喘、发烧和腹泻等状况,则记为发病。发病时遵循兽医给出的治疗方法进行治疗。发病频率计算公式如下:

1.5 数据处理

试验数据使用Excel 2019进行初步整理分析,使用SPSS 20.0软件进行t检验分析,判断标准是以P < 0.05为差异显著。数据结果用“平均值±标准差”表示。

2 结果 2.1 哺乳期补饲开食料对牦牛犊牛生长性能的影响 2.1.1 哺乳期补饲开食料对牦牛犊牛采食量的影响

表 3可知,在第1~50天和第51~100天,试验组牦牛的干物质采食量、粗蛋白质采食量和粗脂肪采食量显著高于对照组(P < 0.05),而中性洗涤纤维采食量和酸性洗涤纤维采食量显著低于对照组(P < 0.05);在第101~150天,2组牦牛采食量无显著差异(P>0.05)。

表 3 哺乳期补饲开食料对牦牛犊牛干物质采食量和营养物质采食量的影响 Table 3 Effects of starter feed on dry matter intake and nutrient intake of yak calves during lactation  
2.1.2 哺乳期补饲开食料对牦牛犊牛体重和平均日增重的影响

表 4可知,试验组和对照组牦牛初始体重无显著差异(P>0.05)。在饲养到第50、100和150天时,试验组牦牛体重均显著高于对照组(P < 0.05)。在第1~50天,牦牛平均日增重试验组和对照组间差异不显著(P>0.05);在第51~100天和第101~150天,试验组牦牛平均日增重显著高于对照组(P < 0.05);在第1~50天,试验组和对照组的平均日增重最高,在第101~150天,平均日增重最低;在第101~150天,试验组料重比显著低于对照组(P < 0.05),且在此阶段2组的料重比显著增加(P < 0.05)。

表 4 哺乳期补饲开食料对牦牛犊牛体重和平均日增重的影响 Table 4 Effects of starter feed on body weight and average daily gain of yak calves during lactation
2.1.3 哺乳期补饲开食料对牦牛犊牛体尺的影响

表 5可知,在第50天,试验组牦牛的体高、胸围和管围显著高于对照组(P < 0.05);在第100天,试验组牦牛的胸围和管围显著高于对照组(P < 0.05);在第150天,试验组牦牛的体高和管围显著高于对照组(P < 0.05)。

表 5 哺乳期补饲开食料对牦牛犊牛体尺的影响 Table 5 Effects of starter feed on body size of yak calves during lactation  
2.2 哺乳期补饲开食料对牦牛犊牛腹泻的影响

表 6可知,在第51~100天,试验组牦牛粪便评分显著低于对照组(P < 0.05);在第1~50天和第51~100天,试验组牦牛腹泻频率显著低于对照组(P < 0.05);在第101~150天,试验组和对照组牦牛均无腹泻的发生。

表 6 哺乳期补饲开食料对牦牛犊牛腹泻的影响 Table 6 Effects of starter feed on diarrhea of yak calves during lactation
2.3 哺乳期补饲开食料对牦牛犊牛发病频率的影响

表 7可知,在第1~50天和第51~100天,试验组牦牛的发病频率显著低于对照组(P < 0.05);在第101~150天,试验组和对照组牦牛均未发病。

表 7 哺乳期补饲开食料对牦牛犊牛发病频率的影响 Table 7 Effects of starter feed on incidence frequency of yak calves during lactation  
3 讨论 3.1 哺乳期补饲开食料对牦牛犊牛生长性能的影响

对于传统放牧的牦牛,犊牛跟随母牦牛进行哺乳,在冷季牧草枯萎,母牦牛产奶量少,不能满足犊牛的生长发育。代乳粉营养成分中含有蛋白质、脂肪和矿物元素可以促进牦牛犊牛的生长发育,提高犊牛平均日增重,缩短母牦牛繁殖周期[17-19]。在早期给牦牛犊牛饲喂苜蓿干草,苜蓿干草的纤维含量高,被动物食入瘤胃后,在瘤胃的蠕动下对瘤胃壁的物理摩擦作用更强,而这种摩擦作用可以促进死亡的上皮细胞从瘤胃壁脱落,降低上皮角质蛋白沉积,使瘤胃上皮变薄,更有利于瘤胃健康[20],并且瘤胃壁因受物理刺激,增强了瘤胃肌化,促进瘤胃蠕动,使瘤胃容积增大,从而促进瘤胃发育[21-22]。开食料是一种营养丰富、易消化吸收的高质量精料,可加快犊牛适应植物饲料,饲喂适口性好的开食料能提高犊牛采食量从而促进其生长发育。Bhatti等[23]研究表明,饲粮由全乳、干草和开食料组合搭配后饲喂犊牛能获得更高的生长速率,本试验在饲喂代乳粉和苜蓿干草的基础上补饲开食料,结果发现,在第1~50天和第51~100天,试验组牦牛犊牛的干物质采食量显著高于对照组,分析原因可能是开食料相比粗料发酵速度快、瘤胃排空率快,因此试验组干物质采食量较高[24]。试验组牦牛犊牛在3个饲养阶段的体重均显著高于对照组,平均日增重在第51~100天和第101~150天这2个阶段试验组显著高于对照组,试验组粗蛋白质和粗脂肪采食量显著高于对照组,而中性洗涤纤维和酸性洗涤纤维采食量显著低于对照组。Biome等[25]发现犊牛平均日增重随着饲粮蛋白质水平的增加而升高,较高的蛋白质水平会提高机体对蛋白质和能量的利用效率。脂肪主要用来提供能量,也能通过调控脂肪酸的生成影响瘤胃微生物区系,进而影响动物的生长发育[26],但两者的互作机制并不明确,需要进一步探索。蛋白质和脂肪采食量较高可能是影响体重的主要原因。结果中发现,在第1~50天,2组平均日增重无显著差异,可能是因为在第1~50天对照组中性洗涤纤维采食量和酸性洗涤纤维采食量较高,纤维属于结构性碳水化合物,可以刺激瘤胃发育,提高营养物质消化吸收从而促进生长发育[27]

在第101~150天,给试验组和对照组牦牛犊牛饲喂相同的饲粮,2组牦牛犊牛干物质采食量无显著差异,试验组牦牛犊牛平均日增重显著高于对照组,料重比显著低于对照组,说明前期饲喂开食料也有利于后期牦牛生长。在结果中发现,试验组和对照组牦牛平均日增重和料重比在第1~50天、第51~100天和第101~150天这3个阶段逐渐降低,可能是更换饲粮比例及更换饲粮种类引起的。以体重、体尺作为犊牛培育的重要指标,可准确地反映犊牛的生长发育情况[28]。第50、100和150天对牦牛体尺进行测量,试验组牦牛的体尺指标有些与对照组无显著差异,但每个阶段中均有体尺指标显著高于对照组。在崔占鸿[29]研究中,补饲开食料和苜蓿干草组牦牛犊牛体高、体斜长和胸围均显著高于自由放牧组牦牛,而与补饲苜蓿干草组牦牛体尺指标差异均不显著。在鲍宇红等[30]补饲半舍饲牦牛研究中发现各组体尺指标无显著差异,但补饲后牦牛的体高、体斜长和胸围有增加的趋势,说明合理的补饲是有必要的。

3.2 哺乳期补饲开食料对牦牛犊牛腹泻频率和发病频率的影响

本试验牦牛在第1~50天腹泻频率和发病频率较高,分析原因可能是牦牛犊牛由跟随母牦牛自然放牧转变为单栏饲养,并且天气较热,发生应激反应。对牦牛犊牛管理不当,众多应激因素会导致犊牛腹泻[31-32]。但试验组的腹泻频率和发病频率均显著低于对照组。初生牦牛犊牛胃肠道消化功能不完善,如果犊牛吃奶过急,会有少量的乳汁进入瘤胃和网胃,而瘤胃和网胃还不能正常消化各种内容物,会异常发酵,最终引起消化不良。并且犊牛免疫系统和神经系统还没有发育完善。这些独特生理特点易造成牦牛犊牛出现消化不良,身体抵抗能力下降,对外界适应能力较差,极易受到各种病原微生物的侵染而引发腹泻。给试验组牦牛在饲喂苜蓿干草基础上补饲开食料,可以促进消化器官的发育,促进肠道对营养物质的吸收,在肠道内厌氧细菌对碳水化合物进行无氧酵解,产生短链脂肪酸,对肠黏膜形态和功能具有保护作用,改善肠道黏膜免疫能力[33-35],并且补饲开食料会改变肠道菌群,肠道菌群对肠道黏膜免疫具有调控作用[36-38],从而降低腹泻的发生。在第51~100天可以看出试验组和对照组牦牛犊牛腹泻频率和发病频率相比第1~50天均有所下降,说明随着牦牛不断适应,应激反应减少,消化道及免疫功能逐渐完善。并且试验组在整个饲养阶段腹泻频率和发病频率均显著低于对照组,说明补饲开食料在整个试验期都发挥了积极的作用。试验还发现在第1~50天虽然腹泻频率和发病频率较高,但平均日增重却比较高,而传统放牧的牦牛犊牛平均日增重较低[29]且发病频率较高[39],说明补饲开食料可促进牦牛犊牛生长发育,增强免疫功能。

4 结论

哺乳期补饲开食料可促进牦牛犊牛生长发育,降低腹泻频率,减少发病情况,并且有利于牦牛犊牛后期的生长发育。

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