RESEARCH PAPER

To Evaluate Feeding Value of a Mixed Silage of Reed Straw and Defective Pear Silage Replacing Whole Corn Silage by in Vitro Method

  • YU Wanrui , 1 ,
  • TANG Limin 1 ,
  • LIU Haonan 1 ,
  • GAO Qifeng 1 ,
  • SUN Yuliang 1 ,
  • TAO Dayong 1, 2, 3 ,
  • JIANG Hui 1, 2, 3 ,
  • JIANG Tao , 1, 2, 3, *
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  • 1 College of Animal Science, Tarim University, Alar 843300, China
  • 2 Key Laboratory of Animal and Grass Resources Utilization in the Tarim Basin, Ministry of Agriculture and Rural Affairs, Alar 843300, China
  • 3 Key Laboratory of Tarim Animal Husbandry Science and Technology, Alar 843300, China
* professor, E-mail:

Received date: 2024-04-09

  Online published: 2024-11-09

Abstract

The aim of this experiment was to investigate the effects of replacing whole corn silage with a mixture of reed straw and defective pear silage on the dynamics of in vitro rumen fermentation parameters, nutrient degradation rates and microbial composition. In vitro fermentation was carried out by replacing 0 (T0 group, control group), 10% (T1 group), 30% (T3 group) and 50% (T5 group) of whole corn silage for 72 h. The cumulative gas production, fermentation parameters, microbial composition and nutrient degradation rate after fermentation were measured at different time points, and evaluated by multi-indicator composite index (MFAEI). The results showed as follows: with the extension of fermentation time, the gas production and contents of ammonia nitrogen (NH3-N), total volatile fatty acids, acetic acid, propionic acid and butyric acid were significantly increased (P<0.05). At 48 and 72 h, gas production in control group was significantly higher than that in T3 and T5 groups (P<0.05). There were no significant differences in pH and NH3-N content among all groups (P>0.05). There was no significant difference in total volatile fatty acid content among different groups at different time points (P>0.05). at 12 and 24 h, the acetic acid content in T5 group was significantly higher than that in T1 group (P<0.05); at 3 and 48 h, the propionic acid content in T1 group was significantly higher than that in T5 group (P<0.05); at 24 h, butyric acid content in control group was significantly higher than that in T5 group (P<0.05); the dry matter degradation rate, neutral detergent fiber degradation rate and acid detergent fiber degradation rate in control group were significantly higher than those in T5 group (P<0.05). MFAEI in T1 group was significantly higher than that in T3 group and T5 group (P<0.05). According to the experimental results, it is recommended to use mixed silage of reed straw and defective pear silage to replace 10% whole corn silage in sheep diet under this experimental condition.

Cite this article

YU Wanrui , TANG Limin , LIU Haonan , GAO Qifeng , SUN Yuliang , TAO Dayong , JIANG Hui , JIANG Tao . To Evaluate Feeding Value of a Mixed Silage of Reed Straw and Defective Pear Silage Replacing Whole Corn Silage by in Vitro Method[J]. Chinese Journal of Animal Nutrition, 2024 , 36(11) : 7394 -7408 . DOI: 10.12418/CJAN2024.629

新疆是畜牧业大省,主要以牛、羊等草食家畜养殖为主[1]。由于近几十年来,牛、羊等草食家畜数量不断增加,气候的改变以及人们的生产生活活动等因素,使得草地退化严重,可利用草地逐渐减少,提供给牛、羊的饲草料严重不足[2]。饲草料短缺一直是制约新疆畜牧业现代化、规模化发展的重要因素[3]。新疆芦苇秸秆资源丰富,但除少部分资源被利用之外,大多数都处于自生自灭的状态,利用率极低;新疆也是我国产梨大省,但每年因各种原因使香梨的浪费达38%以上,残次香梨中含有丰富的可溶性碳水化合物,能够为微生物发酵提供充足的底物,但香梨的含水量较高,易发生腐败[4-7]。青贮玉米被广泛应用于畜牧生产,具有成本低、产量高、营养丰富、适口性好等特点,但玉米生长对氮的需求量较高,加上我国北方地区短生长季的限制,青贮玉米较高的种植成本使其在反刍动物的生产应用上仍然有一定的局限性[8]。因此,本试验用芦苇秸秆与残次香梨混合青贮替代全株玉米青贮,评定其对瘤胃体外发酵参数、营养物质降解率与微生物组成的影响,探讨适宜替代比例,为缓解本地区粗饲料短缺问题提供有价值的参考数据。

1 材料与方法

1.1 试验材料

芦苇秸秆与残次香梨混合青贮已在前期试验中制作完成,并评定出二者质量比为6∶4时品质最优[9];全株玉米青贮由新疆天润牧业提供。试验前将2种样品放入65 ℃烘箱内烘至恒重,粉碎,过40目筛,置于干燥密封环境保存。2种样品的干物质(DM)含量采用GB/T 6435—2014[10]的方法测定;粗蛋白质(CP)含量采用GB/T 6432—2018[11]凯氏定氮法测定;中性洗涤纤维(NDF)含量采用GB/T 20806—2022[12]的方法测定;酸性洗涤纤维(ADF)含量采用NY/T 1459—2022[13]的方法测定;钙含量采用GB/T 6436—2018[14]的方法测定;总磷含量采用GB/T 6437—2018[15]的方法测定。表1为混合青贮与全株玉米青贮的营养水平。
表1 混合青贮与全株玉米青贮的营养水平

Table 1 Nutrient levels of mixed silage and whole corn silage

项目
Items
干物质
DM
粗蛋白质
CP/% DM
中性洗涤纤维
NDF/% DM
酸性洗涤纤维
ADF/% DM

Ca/% DM
总磷
TP/% DM
混合青贮Mixed silage 29.41 4.84 58.51 38.41 0.28 0.96
全株玉米青贮Whole corn silage 32.08 8.07 59.42 43.84 0.45 0.23
本试验经塔里木大学科技伦理委员会批准(批准编号:2024048),选取5只体重[(35.0±2.5) kg]相近、装有永久瘤胃瘘管的成年健康多浪羊,试验羊单圈饲养,每日06:00和18:00各饲喂1次,自由饮水。晨饲前采集瘤胃液,并用4层灭菌纱布过滤至充满CO2的暖壶中,带回实验室备用。

1.2 试验设计

采用单因素试验设计,共分为4组,分别为对照组(基础饲粮,T0组)、替代10%全株玉米青贮组(T1组)、替代30%全株玉米青贮组(T3组)和替代50%全株玉米青贮组(T5组)。本试验参照《肉羊饲养标准》(NY/T 816—2004),日增重100 g/d配制饲粮,精粗比为4∶6。饲粮组成及营养水平见表2
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) %

项目
Items
组别Groups
T0 T1 T3 T5
原料Ingredients
全株玉米青贮Whole corn silage 21.00 18.90 14.70 10.50
混合青贮Mixed silage 2.10 6.30 10.50
苜蓿草粉Alfalfa meal 24.16 24.16 24.16 24.16
稻草Straw 13.65 13.65 13.65 13.65
玉米Corn 22.76 22.60 22.30 22.00
麸皮Bran 10.60 10.60 10.60 10.60
棉籽粕Cottonseed meal 5.82 5.98 6.28 6.58
食盐NaCl 0.66 0.66 0.66 0.66
预混料Premix1) 1.35 1.35 1.35 1.35
合计Total 100.00 100.00 100.00 100.00
营养水平Nutrient levels2)
消化能DE/(MJ/kg) 11.09 11.08 11.07 11.05
粗蛋白质CP 12.01 12.00 11.98 11.96
中性洗涤纤维NDF 43.27 43.28 43.30 43.33
酸性洗涤纤维ADF 27.36 27.27 27.09 26.90
钙Ca 0.48 0.48 0.47 0.47
总磷TP 0.33 0.34 0.37 0.41

1)每千克预混料含有 One kg of premix contained the following:Cu 250 mg, Fe 1 400 mg, Mn 900 mg, Zn 1 200 mg, VA 100 000 IU, VD 327 000 IU, VE 800 IU。

2) 消化能按照公式DE(MJ/kg DM)=17.211-0.135×NDF(%DM)计算,其余营养水平均为实测值。DE was calculated according to the formula DE (MJ/kg DM)=17.211-0.135×NDF (%DM), while the other nutrient levels were measured values.

1.3 体外发酵试验

准确称取200 mg待测饲粮样本,装入100 mL带刻度的注射器中,在注射器内塞上均匀涂抹适量凡士林以保证气密性防止漏气。采用Menke等[16]方法配制人工瘤胃液,将瘤胃液与人工瘤胃液以1∶2的体积比混合,具体操作参考本课题组已发表文章[17]。分别在0、3、6、9、12、24、36、48和72 h记录各注射器的产气量,并在0、3、12、24和48 h时取样。

1.4 测定指标及方法

1.4.1 产气量及产气参测定

分别记录0、3、6、9、12、24、36、48和72 h各注射器的产气量并用空白进行校正。产气量和产气参数按如下公式计算:
GP= 200 W×(Vt-V0)×30/V0
式中:GP为t时刻的产气量(mL);Vtt时刻注射器的产气量读数(mL);V0t时刻空白注射器的产气量刻度读数(mL);W为样品干物质重量(mg)。
GP=a+b(1-e-ct)。
式中:t为发酵时间(h);GP为t时刻的产气量(mL);a为快速降解部分产气量(mL);b为慢速降解部分产气量(mL);c为产气速率常数(%/h);a+b为潜在产气量(mL)[18]

1.4.2 发酵参数测定

在到达各发酵时间时将样品立即放入冰水中停止发酵,用pH计测定pH,并将一部分样品冻存于-20 ℃冰箱中,用于测定氨态氮(NH3-N)和挥发性脂肪酸(VFA)的含量;另一部分样品放入-80 ℃冰箱中,用于瘤胃细菌多样性分析。发酵液中NH3-N含量采用Searle[19]的方法进行测定;乙酸、丙酸和丁酸含量采用Thermo Scientific TRACE 1310型气相色谱仪测定。

1.4.3 营养物质降解率测定

准确称取5 g (精确至0.000 1)饲粮装入孔径为35 μm的尼龙袋中,具体操作参考本课题组已发表文章[17]。饲粮和残渣中的DM含量采用GB/T 6435—2014[10]的方法测定;NDF含量采用GB/T 20806—2022[12]的方法测定;ADF含量采用NY/T 1459—2022[13]的方法测定,并按如下公式计算营养物质降解率:
营养物质降解率(%)=100×(a-b)/a
式中:a为营养物质含量(g);b为发酵72 h后残渣营养物质含量(g)。

1.4.4 瘤胃微生物组成

先用E.Z.N.A.®Water DNA Kit试剂盒(Omega Bio-Tek,美国)提取总DNA。使用引物(338F:5'-ACTCCTACGGGAGGCAGCA-3';806R:5'-GGACTACHVGGGTWTCTAAT-3')对16S rDNA基因V3~V4可变区进行PCR扩增,并对其产物进行纯化、定量。使用Illumina NovaSeq 6000平台进行测序(北京擎科生物科技有限公司)。

1.5 数据处理与统计分析

单项组合效应指数(SFAEI)与多项指标综合指数(MFAEI)的计算参考卢德勋[20]的计算方法。MFAEI为各单项组合效应值之和。微生物测序原始数据参考本课题组已发表文章[17]进行处理。试验数据采用SPSS 24.0软件进行单因素方差分析,采用Duncan氏法进行多重比较,结果用平均值和均值标准误(SEM)表示,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 混合青贮替代全株玉米青贮对体外发酵产气量与产气参数的影响

表3可知,随着发酵时间的延长,各组产气量显著增加(P<0.05)。在3~12 h产气速度较快,随后速度逐渐减慢。在48和72 h时,对照组产气量显著高于T3组和T5组(P<0.05)。各组快速产气部分、慢速产气部分和产气速率常数差异不显著(P>0.05),对照组的潜在产气量显著高于T3组和T5组(P<0.05)。
表3 混合青贮替代全株玉米青贮对体外发酵产气量与产气参数的影响

Table 3 Effects of mixed silage replacing whole corn silage on gas production and gas production parameters during in vitro fermentation

项目
Items
组别Groups SEM PP-value
T0(对照
Control)
T1 T3 T5 处理
Treatment
时间
Time
处理×时间
Treatment×
time
产气量Gas production/mL
3 h 11.00H 10.67H 10.67H 10.33H 0.19 0.728 <0.001 0.372
6 h 20.00G 20.33G 20.00G 20.00G 0.15 0.859
9 h 29.33F 29.00F 28.67F 28.33F 0.24 0.557
12 h 35.67E 35.00E 34.33E 34.33E 0.24 0.139
24 h 51.00D 50.67D 49.67D 49.00D 0.36 0.170
36 h 59.00C 58.67C 57.00C 56.67C 0.46 0.173
48 h 63.00Ba 62.33Bab 60.33Bb 60.33Bb 0.45 0.039
72 h 66.67Aa 66.00Aab 64.00Ab 64.00Ab 0.46 0.045
产气参数Gas production parameters
快速产气部分a/mL -0.057 -0.147 -0.084 -0.003 0.272 0.999
慢速产气部分b/mL 66.83 66.26 63.96 63.89 0.61 0.194
潜在产气量a+b/mL 66.77a 66.10ab 63.88b 63.89b 0.49 0.031
产气速率常数c/(%/h) 0.062 0.062 0.064 0.063 0.001 0.755

同列数据肩标不同大写字母表示不同时间之间差异显著(P<0.05),同行数据肩标不同小写字母表示不同组之间差异显著(P<0.05)。下表同。

In the same column, values with different capital letter superscripts mean significant difference among different time (P<0.05); in the same row, values with different small letter superscripts mean significant difference among groups (P<0.05). The same as below.

2.2 混合青贮替代全株玉米青贮对体外发酵参数的影响

表4可知,随着发酵时间的延长,pH显著降低(P<0.05),NH3-N含量显著升高(P<0.05),各组pH和NH3-N含量差异不显著(P>0.05)。
表4 混合青贮替代全株玉米青贮对体外发酵pH和氨态氮含量的影响

Table 4 Effects of mixed silage replacing whole corn silage on pH and ammonia nitrogen content during in vitro fermentation

项目
Items
组别Groups SEM PP-value
T0(对照
Control)
T1 T3 T5 处理
Treatment
时间
Time
处理×时间
Treatment×
time
pH
0 h 6.60A 6.61A 6.62A 6.60A 0.02 0.994
<0.001

1.000
3 h 6.44B 6.45B 6.46B 6.48B 0.01 0.148
12 h 6.34C 6.35C 6.37C 6.37C 0.01 0.661
24 h 6.20D 6.21D 6.21D 6.22D 0.01 0.898
48 h 6.18D 6.18D 6.19D 6.20D 0.01 0.896
氨态氮NH3-N/(mg/dL)
0 h 9.61E 9.59E 9.62E 9.61E 0.04 0.995 <0.001 1.000
3 h 10.30D 10.24D 10.19D 10.14D 0.04 0.663
12 h 13.48C 13.46C 13.40C 13.33C 0.08 0.925
24 h 15.85B 15.81B 15.73B 15.70B 0.07 0.924
48 h 18.41A 18.33A 18.17A 18.15A 0.08 0.642
表5可知,随着发酵时间的延长,总挥发性脂肪酸、乙酸、丙酸和丁酸的含量显著升高(P<0.05),乙酸/丙酸显著降低(P<0.05)。总挥发性脂肪酸含量在各时间点不同组之间差异不显著(P>0.05);在12和24 h时,T5组乙酸含量显著高于对照组(P<0.05);除0和24 h时,其余各时间点对照组丙酸含量均显著高于T5组(P<0.05);在24 h时,对照组丁酸含量显著高于T5组(P<0.05)。
表5 混合青贮替代全株玉米青贮对体外发酵VFA含量的影响

Table 5 Effects of mixed silage replacing whole corn silage on VFA content during in vitro fermentation

项目
Items
组别Groups SEM PP-value
T0(对照
Control)
T1 T3 T5 处理
Treatment
时间
Time
处理×时间
Treatment×
time
总挥发性脂肪酸TVFA/(mmol/L)
0 h 19.30E 19.32E 19.35E 19.37E 0.03 0.833 <0.001 0.998
3 h 22.02D 21.94D 21.97D 21.95D 0.03 0.901
12 h 29.34C 29.30C 29.24C 29.25C 0.03 0.742
24 h 33.20B 33.21B 33.22B 33.26B 0.04 0.968
48 h 38.43A 38.36A 38.39A 38.37A 0.05 0.952
乙酸AA/(mmol/L)
0 h 14.79E 14.76E 14.82E 14.83E 0.02 0.792 <0.001 0.708
3 h 15.41D 15.43D 15.46D 15.51D 0.02 0.440
12 h 16.40Cb 16.49Cab 16.52Cab 16.63Ca 0.03 0.037
24 h 18.35Bb 18.47Bb 18.54Bab 18.67Ba 0.04 0.025
48 h 21.09A 21.13A 21.19A 21.28A 0.03 0.161
丙酸PA/(mmol/L)
0 h 2.78E 2.81E 2.79E 2.83E 0.02 0.768 <0.001 0.326
3 h 3.91Da 3.88Da 3.84Dab 3.78Db 0.02 0.037
12 h 7.21Ca 7.14Cab 7.12Cab 7.06Cb 0.02 0.025
24 h 8.70B 8.66B 8.61B 8.55B 0.02 0.076
48 h 10.47Aa 10.41Aab 10.39Abc 10.33Ac 0.02 0.016
丁酸BA/(mmol/L)
0 h 1.73E 1.75E 1.74E 1.71E 0.01 0.582 0.012 0.805
3 h 2.69D 2.63D 2.67D 2.66D 0.02 0.872
12 h 5.73C 5.66C 5.60C 5.56C 0.03 0.169
24 h 6.15Ba 6.08Bab 6.07Bab 6.05Bb 0.02 0.027
48 h 6.87A 6.82A 6.80A 6.76A 0.02 0.384
乙酸/丙酸AA/PA
0 h 5.32A 5.26A 5.31A 5.24A 0.03 0.801 <0.001 0.288
3 h 3.94Bb 3.98Bb 4.03Bab 4.11Ba 0.02 0.012
12 h 2.27Cb 2.31Cab 2.32Cab 2.36Ca 0.01 0.043
24 h 2.11Dc 2.13Dbc 2.16Dab 2.18Da 0.01 0.005
48 h 2.02Dc 2.03Ebc 2.04Eb 2.06Ea 0.01 0.006

2.3 混合青贮替代全株玉米青贮体外发酵对营养物质降解率的影响

表6可知,对照组的干物质降解率和酸性洗涤纤维降解率均显著高于T5组(P<0.05),但与T1组和T3组不显著(P>0.05)。
表6 混合青贮替代全株玉米青贮体外发酵对营养物质降解率的影响

Table 6 Effects of mixed silage replacing whole corn silage on nutrient degradation rate during in vitro fermentation %

项目
Items
组别Groups SEM P
P-value
T0(对照Control) T1 T3 T5
干物质降解率DMD 56.24a 55.27a 53.21ab 50.36b 0.84 0.031
中性洗涤纤维降解率NDFA 60.10 58.29 57.70 56.66 0.53 0.112
酸性洗涤纤维降解率ADFD 48.42a 47.92a 46.53a 43.24b 0.72 0.015

2.4 混合青贮替代全株玉米青贮体外发酵对多项组合效应值的影响

表7可知,T1组MFAEI显著高于T3组和T5组(P<0.05),T3组和T5组之间差异不显著(P>0.05)。
表7 混合青贮替代全株玉米青贮体外发酵对多项组合效应值的影响

Table 7 Effects of mixed silage replacing whole corn silage on multiple combination effect values during in vitro fermentation

项目
Items
组别Groups SEM P
P-value
T1 T3 T5
单项指标综合指数SFAEI
pH 0.13b 0.28a 0.30a 0.08 0.013
氨态氮NH3-N -0.33a -1.07b -1.08b 0.11 0.005
总挥发性脂肪酸TVFA -0.11 -0.08 -0.06 0.02 0.174
产气量GP -1.02a -4.17b -4.17b 0.49 0.002
多项指标综合指数MFAEI -1.33a -5.04b -5.01b 0.55 0.001

2.5 混合青贮替代全株玉米青贮体外发酵瘤胃微生物多样性分析

2.5.1 混合青贮替代全株玉米青贮体外发酵瘤胃微生物α多样性分析

表8可知,在24 h时,对照组和T1组的Chao1指数显著高于T3组和T5组(P<0.05),其余各时间点差异不显著(P≥0.05);各组3 h的Chao1指数显著高于其他时间点(P<0.05)。在3 h时,T5组的Simpson指数显著低于其他3组(P<0.05);12 h时T1组的Simpson指数显著高于其他3组(P<0.05)。在24 h时,对照组的Shannon指数显著高于T3组和T5组(P<0.05);各组3 h的Shannon指数显著高于其他时间点(P<0.05)。
表8 混合青贮替代全株玉米青贮体外发酵瘤胃微生物α多样性分析 Table 8 α diversity analysis of rumen microorganisms of mixed silage replacing whole corn silage during in vitro fermentation
项目
Items
组别Groups SEM PP-value
T0(对照
Control)
T1 T3 T5 处理
Treatment
时间
Time
处理×时间
Treatment×
time
Chao1指数Chao1 index
0 h 1 123.28C 1 008.20C 1 100.12C 1 033.78CD 27.04 0.438 <0.001 <0.001
3 h 2 085.51A 2 176.46A 2 267.05A 2 139.96A 34.96 0.344
12 h 1 442.33B 1 388.39B 1 318.18B 1 239.09B 35.26 0.196
24 h 1 435.67Ba 1 291.76Ba 927.89Db 1 063.79Cb 63.27 <0.001
48 h 971.33C 938.65C 846.90D 999.72D 26.64 0.175
ACE指数ACE index
0 h 1 125.21C 1 010.49C 1 104.14C 1 037.24C 28.51 0.511 <0.001 0.001
3 h 2 090.74A 2 183.02A 2 272.87A 2 147.96A 43.05 0.217
12 h 1 446.83B 1 389.59B 1 323.27B 1 242.01B 35.23 0.120
24 h 1 437.41Ba 1 294.64Ba 930.54CDb 1 064.75Cb 62.81 <0.001
48 h 974.54C 941.44C 851.87D 1 002.74C 22.54 0.065
Simpson指数Simpson index
0 h 0.994 1B 0.993 5B 0.993 6B 0.993 7 0.000 2 0.957 <0.001 0.137
3 h 0.996 5Aa 0.997 1Aa 0.997 0Aa 0.993 3b 0.000 5 0.006
12 h 0.993 5Bb 0.996 1Aa 0.992 9Bb 0.992 0b 0.000 7 0.007
24 h 0.993 9B 0.993 3B 0.993 3B 0.992 8 0.000 3 0.822
48 h 0.992 1B 0.993 2B 0.993 2B 0.992 6 0.000 5 0.727
Shannon指数Shannon index
0 h 8.79BC 8.64BC 8.73B 8.58B 0.12 0.661 <0.001 0.254
3 h 9.56A 9.70A 9.79A 9.52A 0.04 0.406
12 h 8.93BC 8.91B 8.70B 8.82B 0.03 0.553
24 h 9.01Ba 8.88Bab 8.41Bb 8.61Bb 0.07 0.007
48 h 8.51C 8.52C 8.51B 8.53B 0.02 0.999

2.5.2 混合青贮替代全株玉米青贮体外发酵瘤胃微生物门水平分布

表9可知,在各组瘤胃发酵液中,厚壁菌门(Firmicutes)、拟杆菌门(Bacteroidota)与变形菌门(Proteobacteria)相对丰度之和均达到90%以上,因此,厚壁菌门、拟杆菌门与变形菌门为优势菌门。随着发酵时间的变化,厚壁菌门相对丰度先降低后升高,变形菌门相对丰度先升高后降低,拟杆菌门相对丰度无明显变化趋势。
表9 混合青贮替代全株玉米青贮体外发酵瘤胃微生物门水平分布

Table 9 Distribution of rumen microbiota at phylum level of mixed silage replacing whole corn silage during in vitro fermentation

项目
Items
组别Groups SEM PP-value
T0(对照
Control)
T1 T3 T5 处理
Treatment
时间
Time
处理×时间
Treatment×
time
厚壁菌门Firmicutes
0 h 45.64Cd 51.22Ba 46.87Bc 47.80Cb 0.64 <0.001 <0.001 <0.001
3 h 34.52Dd 36.59Ec 38.01Db 44.93Da 1.19 <0.001
12 h 45.47Cb 39.11Dd 42.39Cc 51.53Ba 1.38 <0.001
24 h 52.32Aa 44.19Cc 47.01Bb 47.37Cb 0.89 <0.001
48 h 50.06Bc 54.96Aa 54.18Aab 53.80Ab 0.58 <0.001
拟杆菌门Bacteroidota
0 h 38.11Aa 29.63Dc 33.46Bb 34.03Bb 0.91 <0.001 <0.001 <0.001
3 h 30.50Cc 33.15Bb 28.50Dd 35.08Aa 0.77 <0.001
12 h 35.53Bb 26.88Ec 36.97Aa 25.79Dd 1.51 <0.001
24 h 27.23Dd 35.41Ab 37.49Aa 30.71Cc 1.22 <0.001
48 h 35.83Ba 32.00Cc 32.42Cc 33.76Bb 0.47 <0.001
变形菌门Proteobacteria
0 h 10.66Bb 11.55Ca 11.87Ba 11.06Ab 0.15 0.002 <0.001 <0.001
3 h 19.16Aa 14.66Bc 15.66Ab 11.43Ad 0.83 <0.001
12 h 10.44Bb 18.72Aa 11.26Cb 10.91Ab 1.04 <0.001
24 h 8.87Cc 10.61Da 6.76Dd 9.95Bb 0.45 <0.001
48 h 5.19Db 4.77Eb 5.70Ea 4.21Cc 0.18 0.001
髌骨菌门Patescibacteria
0 h 2.59C 3.80A 3.99AB 3.99C 0.23 0.058 <0.001 <0.001
3 h 1.89Cc 2.29Bbc 2.91Cb 4.71BCa 0.34 <0.001
12 h 4.50Ba 2.26Bb 4.68Aa 7.62Aa 0.58 <0.001
24 h 5.74Aa 3.94Ac 3.71Bc 4.89Bb 0.26 0.001
48 h 3.86B 4.13A 3.33BC 3.82C 0.13 0.211
疣微菌门Verrucomicrobiota
0 h 1.67D 2.03C 2.14C 2.29C 0.09 0.071 <0.001 <0.001
3 h 2.03CD 2.27C 1.98C 1.94C 0.08 0.496
12 h 2.15Cbc 2.47Bab 2.86Ba 1.96Cc 0.12 0.006
24 h 2.69Bc 3.18Abc 3.60Aab 3.89Aa 0.16 0.011
48 h 3.73Aa 2.99Abc 2.51BCc 3.28Bab 0.15 0.007
在3和12 h时,T5组的厚壁菌门相对丰度显著高于其他3组(P<0.05);在24 h时,对照组的厚壁菌门相对丰度显著高于其他3组(P<0.05);在48 h时,对照组厚壁菌门相对丰度显著低于其他3组(P<0.05)。
在3 h时,T5组的拟杆菌门的相对丰度显著高于其他3组(P<0.05);在12和24 h时,T3组的拟杆菌门的相对丰度显著高于其他3组(P<0.05);在48 h时,对照组的拟杆菌门的相对丰度显著高于其他3组(P<0.05)。

2.5.3 混合青贮替代全株玉米青贮体外发酵瘤胃微生物属水平分布

表10可知,混合青贮替代全株玉米青贮体外发酵瘤胃微生物属水平的排名前10的物种分别为普雷沃氏菌属(Prevotella)、理研菌科RC9肠道群(Rikenellaceae_RC9_gut_group)、未培养的瘤胃细菌(uncultured_rumen_bacterium)、瘤胃球菌属(Ruminococcus)、短波单胞菌属(Brevundimonas)、未分类的产粪甾醇真细菌群(unclassified_[Eubacterium]_coprostanoligenes_group)、候选单胞生糖菌属(Candidatus_Saccharimonas)、未分类梭菌纲UCG-014(unclassified_Clostridia_UCG_014)、UCG_002和CAG_352。在3 h时,T5组的普雷沃氏菌属相对丰度显著高于其他3组(P<0.05);在12和24 h时,T3组的普雷沃氏菌属相对丰度显著高于其他3组(P<0.05);在48 h时,T1组的普雷沃氏菌属相对丰度显著高于其他3组(P<0.05)。
表10 混合青贮替代全株玉米青贮体外发酵瘤胃微生物属水平分布

Table 10 Distribution of rumen microbiota at genus level of mixed silage replacing whole corn silage during in vitro fermentation

项目
Items
组别Groups SEM PP-value
T0(对照
Control)
T1 T3 T5 处理
Treatment
时间
Time
处理×时间
Treatment×
time
普雷沃氏菌属Prevotella
0 h 15.76Aa 13.96Ab 14.45Ab 15.37Aa 0.24 0.005 <0.001 <0.001
3 h 11.81Cb 12.24Bb 8.11Cc 14.62Ba 0.71 <0.001
12 h 14.12Bb 6.81Dd 14.97Aa 8.46Dc 1.06 <0.001
24 h 7.68Dc 11.66Cb 13.57Ba 11.57Cb 0.65 <0.001
48 h 6.15Eb 6.91Da 6.11Db 6.30Eb 0.10 0.011
理研菌科RC9肠道群Rikenellaceae_RC9_gut_group
0 h 9.43Ba 6.73Cc 8.12Cb 8.44Bb 0.30 <0.001 <0.001 <0.001
3 h 3.00Ec 6.44Cb 3.57Ec 8.50Ba 0.68 <0.001
12 h 8.59Ca 4.76Dc 9.06Ba 6.90Cb 0.52 <0.001
24 h 7.10Dc 9.52Ba 7.23Dc 7.95Bb 0.29 <0.001
48 h 15.57Aa 13.47Ac 13.79Ac 14.48Ab 0.26 <0.001
未培养的瘤胃细菌Uncultured_rumen_bacterium
0 h 6.43C 7.13A 6.88A 6.82B 0.10 0.078 <0.001 <0.001
3 h 2.96Dc 3.93Cb 3.32Cc 6.99Ba 0.49 <0.001
12 h 7.37Bb 3.89Cd 6.80Ac 7.97Aa 0.48 <0.001
24 h 7.99Aa 7.19Aa 5.92Bb 7.66Aa 0.26 0.002
48 h 7.33Ba 6.37Bb 6.81Aab 7.03Ba 0.13 0.021
瘤胃球菌属Ruminococcus
0 h 4.31Cc 5.90Aa 4.84Bb 4.46Dc 0.19 <0.001 <0.001 <0.001
3 h 2.67Db 3.10Cb 2.88Db 5.61Ba 0.36 <0.001
12 h 5.15Bb 3.15Cc 5.46Ab 6.84Aa 0.40 <0.001
24 h 6.32Aa 5.78Ab 5.29Ac 6.54Aa 0.16 <0.001
48 h 4.49Cbc 4.76Bab 4.20Cc 5.06Ca 0.11 0.017
短波单胞菌属Brevundimonas
0 h 4.35Bb 5.02Ba 5.17Aa 3.67Dc 0.19 <0.001 <0.001 <0.001
3 h 2.39Dc 1.70Dd 3.19Bb 5.76Ba 0.47 <0.001
12 h 4.81Ab 2.86Cc 4.79Ab 7.05Aa 0.45 <0.001
24 h 4.56ABb 5.49Aa 3.45Bc 4.82Cb 0.23 <0.001
48 h 2.99Ca 2.50Cb 2.43Cb 2.34Eb 0.09 0.011
未分类的产粪甾醇真细菌群Unclassified_[Eubacterium]_coprostanoligenes_group
0 h 3.75Bb 4.41Ba 4.23Ba 4.56Aa 0.11 0.014 <0.001 <0.001
3 h 1.78Dc 2.25Db 1.88Ec 3.25Ca 0.18 <0.001
12 h 2.85Cb 1.96Dc 2.73Db 3.57Ba 0.18 <0.001
24 h 4.09Aa 3.22Cc 3.66Cb 3.25Cc 0.11 <0.001
48 h 3.71Bc 4.88Aa 4.94Aa 4.27Ab 0.16 <0.001
候选单胞生糖菌属Candidatus_Saccharimonas
0 h 2.07Cc 3.29Ba 3.46Ba 2.87Eb 0.17 <0.001 <0.001 <0.001
3 h 1.50Dc 1.69Cc 2.44Db 4.02Ca 0.30 <0.001
12 h 3.58Bc 1.83Cd 3.94Ab 6.76Aa 0.54 <0.001
24 h 5.23Aa 3.52Ac 3.28Bc 4.53Bb 0.24 <0.001
48 h 3.41Bb 3.68Aa 2.91Cc 3.35Db 0.09 <0.001
未分类梭菌纲UCG-014 Unclassified_Clostridia_UCG_014
0 h 3.48Bc 4.05Aa 3.77Ab 3.67Bbc 0.07 0.001 <0.001 <0.001
3 h 1.71Dc 2.46Db 1.89Dc 4.01Aa 0.28 <0.001
12 h 4.08Aa 2.15Ec 3.78Ab 3.95Aab 0.13 <0.001
24 h 2.99C 3.02B 2.93B 2.98C 0.05 0.867
48 h 2.82Ca 2.71Ca 2.23Cb 2.73Da 0.07 <0.001
UCG_002
0 h 0.86Db 1.13Ca 0.76Db 0.81Db 0.05 0.003 <0.001 <0.001
3 h 0.80Dbc 0.92Db 0.63Dc 1.29Ca 0.08 0.001
12 h 1.64Bb 0.71Ec 2.76Ca 0.87Dc 0.25 <0.001
24 h 1.34Cd 2.14Bc 3.15Ba 3.18Ba 0.23 <0.001
48 h 4.70Ac 6.69Aa 6.22Ab 6.24Ab 0.23 <0.001
CAG_352
0 h 1.05Cc 2.32Ca 1.81Bb 1.18Dc 0.16 <0.001 <0.001 <0.001
3 h 1.02Cc 1.00Dc 1.39Cb 2.33Ca 0.17 <0.001
12 h 4.32Bb 2.84Bc 2.40Ad 5.10Aa 0.33 <0.001
24 h 5.79Aa 3.20Ac 2.21Ad 4.63Bb 0.41 <0.001
48 h 0.55D 0.82D 0.61D 0.67E 0.03 0.099

3 讨论

3.1 混合青贮替代全株玉米青贮对体外发酵产气量与产气参数的影响

体外发酵产生的气体主要是由饲粮中的碳水化合物和粗蛋白质产生的二氧化碳和甲烷,其产气量主要受可发酵有机物含量和瘤胃微生物活性的影响,能够反映饲料的可发酵程度[21]。本试验中,在体外发酵3、6、9、12、24和36 h时,各组产气量差异不显著,而在体外发酵48和72 h时,对照组的产气量显著高于T3组和T5组。这表明各组饲粮中的易发酵的营养物质含量相似,而混合青贮中的不易发酵的结构性碳水化合物的含量高于全株玉米青贮[22]。这与各组饲粮的快速产气部分差异不显著,而对照组的潜在产气量显著高于T3组和T5组的结果相对应。各组饲粮体外发酵产气速率差异不显著,这表明瘤胃微生物活性差异性不大,饲粮中的能氮平衡也没有差异[23]

3.2 混合青贮替代全株玉米青贮对体外发酵参数的影响

瘤胃液pH是反映瘤胃环境稳态情况和发酵特征的重要指标,是瘤胃微生物正常生存和发挥正常功能的必要条件[24]。有研究表明,瘤胃液的pH范围在6.0~6.8,有利于维持瘤胃内环境的稳定[25]。本试验中,各组发酵液的pH均在正常范围内,且各组之间差异不显著,这表明当混合青贮替代不同比例的全株玉米青贮后,对瘤胃内环境无不良影响。
NH3-N含量是评价瘤胃发酵状况的主要指标之一,可反映微生物对饲粮中蛋白质的分解能力以及吸收速率的平衡状态[26]。研究认为,瘤胃内适宜的NH3-N含量一般为6.30~27.50 mg/dL[27]。本试验各组NH3-N含量均处于正常范围之内,且各组NH3-N含量无显著差异,表明微生物对饲粮中蛋白质的分解能力以及吸收速率的平衡状态无不良影响。
挥发性脂肪酸主要包括乙酸、丙酸、丁酸,是饲粮被瘤胃微生物降解的主要终产物,它们被瘤胃上皮吸收并为反刍动物提供70%~80%的能量[28]。本试验中,发酵48 h后,各组饲粮的总挥发性脂肪酸、乙酸和丁酸含量差异不显著,对照组丙酸含量显著高于T3组和T5组。这可能是由于T3组和T5组的中性洗涤纤维含量相对较高,使丙酸含量降低,同时也使乙酸/丙酸升高[29]

3.3 混合青贮替代全株玉米青贮体外发酵对营养物质降解率的影响

饲粮营养物质的瘤胃降解率可反映饲粮营养物质在瘤胃中被微生物转化和利用的情况,在一定范围内降解率越高,表明该营养物质越容易被反刍动物消化利用[30]。本试验中,对照组的干物质降解率显著高于T5组。这可能与对照组的中性洗涤纤维含量相对较低有关[31]。中性洗涤纤维主要是由纤维素、半纤维素和木质素等组成,其中半纤维素部分是主要可发酵的成分,而木质素部分结构独特,几乎不会被瘤胃微生物所利用,因此,影响中性洗涤纤维降解率主要因素是木质素在中性洗涤纤维中的比例[32]。本试验中,对照组的中性洗涤纤维降解率显著高于T5组。这可能与对照组中的木质素含量相对较低,可发酵的半纤维素含量较高有关。

3.4 混合青贮替代全株玉米青贮体外发酵瘤胃微生物多样性分析

在本试验中,体外发酵48 h后,各组饲粮的瘤胃微生物α多样性无显著差异,这表明混合青贮替代不同比例的全株玉米青贮对瘤胃微生物多样性无显著影响,瘤胃微生物相对稳定[33]。这可能与本试验中4个组的粗饲料比例相同,并且蛋白质和能量水平相同有关[34]
本试验中,各组门水平优势菌群均为厚壁菌门、拟杆菌门和变形菌门,这与许多研究结果[35-37]一致。厚壁菌门主要分解纤维类物质,而拟杆菌门在非纤维类物质中发挥重要作用[38-39]。本试验中,发酵48 h后,对照组厚壁菌门相对丰度显著低于其他3组,而拟杆菌门相对丰度显著高于其他3组。这可能与各组饲粮的营养物质组成相关。
本试验中,各组属水平优势菌群均为普雷沃氏菌属,这与许多研究结果[40-42]相一致。普雷沃氏菌属为革兰氏阴性菌,它不仅参与纤维的降解,还能够促进多糖的降解,并且参与半纤维素、果胶和蛋白质的利用过程[43]。本试验中,T1组饲粮的普雷沃氏菌属的相对丰度显著高于其他3组,这表明混合青贮替代10%的全株玉米青贮影响了普雷沃氏菌属的组成和相对丰度,提高了非纤维多糖、蛋白质等营养物质的分解效率。

4 结论

本试验条件下,芦苇秸秆与残次香梨混合青贮替代不同比例全株玉米青贮对体外发酵pH、NH3-N含量、总挥发性脂肪酸含量和α多样性无显著影响。本试验条件下,推荐使用芦苇秸秆与残次香梨混合青贮替代绵羊饲粮中10%的全株玉米青贮。本次试验仅为体外试验,仍需开展动物体内试验进一步验证本结论。
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