Effects of Rice Husk, Caproic Acid and Zinc Caproate on Fermentation Quality, Nutrients and Microbial Number of Rain-Exposed Oat Silage

FAN Wenke; CAO Yingbo; WANG Wenyan; LI Guangzhuan; CUI Yaoming; QIAO Hanzhen; LI Defeng; GUO Linna

doi:10.12418/CJAN2026.310

2026 , Vol. 38 >Issue 5: 3897 - 3907

DOI: https://doi.org/10.12418/CJAN2026.310

RESEARCH PAPER

Effects of Rice Husk, Caproic Acid and Zinc Caproate on Fermentation Quality, Nutrients and Microbial Number of Rain-Exposed Oat Silage

FAN Wenke ^,¹ ,
CAO Yingbo ¹ ,
WANG Wenyan ¹ ,
LI Guangzhuan ¹ ,
CUI Yaoming ¹ ,
QIAO Hanzhen ¹ ,
LI Defeng ² ,
GUO Linna ^,¹^,^*

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¹ College of Bioengineering, Henan University of Technology, Zhengzhou 450000, China
² College of Animal Science and Technology, Henan Agricultural University, Zhengzhou 450046, China

*lecturer, E-mail: linnam921@163.com

Received date: 2025-09-29

Online published: 2026-05-14

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Abstract

This experiment was conducted to investigate the effects of rice husk, caproic acid and zinc caproate on fermentation quality, nutrients and microbial number of rain-exposed oat silage. The experiment was set up a high moisture content group (original moisture content of harvested oats, 78.43%) and a low moisture content group (adjusted moisture content by adding 4% rice husk powder, 74.58%), three treatments were set up for each moisture content: control group (CK group, no additives), caproic acid group (CA group, added 0.5% caproic acid) and 0.5% zinc caproate group (ZnCA group, added 0.5% zinc caproate). After 80 and 210 days of silage and 6 days of aerobic exposure, the fermentation quality, nutrients and microbial number of oat silage were measured. The main effect analysis showed as follows: 1) after 80 days of silage, the ammonia nitrogen, lactic acid, acetic acid contents and lactic acid bacteria number of CA group and ZnCA group were significantly lower than those of CK group (P<0.05), and the propionic acid and water-soluble carbohydrate contents were significantly higher than those of CK group (P<0.05); the ammonia nitrogen, lactic acid, acetic acid, propionic acid, butyric acid and crude protein contents of high moisture content group were significantly higher than those of low moisture content group (P<0.05), and the dry matter and water-soluble carbohydrate contents were significantly lower than those of low moisture content group (P<0.05). 2) After 210 days of silage, the pH and ammonia nitrogen, acetic acid contents and lactic acid bacteria number of CA group and ZnCA group were significantly lower than those of CK group (P<0.05), and the propionic acid and water-soluble carbohydrate contents were significantly higher than those of CK group (P<0.05); the ammonia nitrogen, lactic acid, acetic acid and crude protein contents of high moisture content group were significantly higher than those of low moisture content group (P<0.05), and the dry matter and water-soluble carbohydrate contents were significantly lower than those of low moisture content group (P<0.05). 3) After 6 days of aerobic exposure, the pH and lactic acid bacteria number of CA group and ZnCA group were significantly lower than those of CK group (P<0.05), and the dry matter content was significantly higher than that of CK group (P<0.05); the pH of high moisture content group was significantly higher than that of low moisture content group (P<0.05), and the dry matter content and lactic acid bacteria number were significantly lower than those of low moisture content group (P<0.05). In conclusion, the rice husk, caproic acid and zinc caproate can effectively improve the fermentation quality and aerobic exposure stability of rain-exposed oat silage; among them, the adding rice husk and 0.5% zinc caproate group showed the best oat silage quality, which provides a method for the fermentation regulation of high-moisture oat silage.

Key words： oat; moisture content; silage; rice husk; caproic acid; zinc caproate

Cite this article

FAN Wenke , CAO Yingbo , WANG Wenyan , LI Guangzhuan , CUI Yaoming , QIAO Hanzhen , LI Defeng , GUO Linna . Effects of Rice Husk, Caproic Acid and Zinc Caproate on Fermentation Quality, Nutrients and Microbial Number of Rain-Exposed Oat Silage[J]. Chinese Journal of Animal Nutrition, 2026 , 38(5) : 3897 -3907 . DOI: 10.12418/CJAN2026.310

优质饲草是草食畜牧业健康、高质量发展的基础保障。其中,青贮饲料作为反刍动物的主要粗饲料来源,不仅能有效保存饲草养分,还可改善适口性,为动物提供全年稳定的营养供给,在现代畜牧业中占据重要地位^[1-2]。据《“十四五”全国饲草产业发展规划》显示,当前我国优质饲草缺口仍接近5 000万t。为缓解全株玉米收储压力,扩大优质饲草来源,近年来,“冬燕麦草+夏玉米”种植模式作为适宜黄淮海地区的饲草种植模式被广泛推行,可提高优质饲草产量^[3]。然而,全球气候变化导致我国黄淮海地区降雨量增加,燕麦收获期间其含水量会大幅升高。研究表明,高含水量燕麦中病原菌和植物酶的活性增强,青贮过程中会产生严重的丁酸发酵和营养损失,使得青贮发酵品质降低甚至发生霉变,威胁动物健康^[4-6]。因此,降低原料含水量、抑制不良微生物发酵对雨淋后高含水量燕麦青贮发酵品质的调控至关重要。

我国稻壳资源丰富,年产量巨大,但当前利用率较低^[7]。研究表明,在青贮饲料中添加一定比例稻壳可有效调节青贮含水量,提高青贮发酵品质^[8-9]。若将其应用于解决多雨季节燕麦收割后含水量过高的问题,不仅有助于提升燕麦青贮的发酵品质与稳定性,也对推动稻壳副产物的资源化利用具有重要意义。中链脂肪酸具有较强的抗菌和免疫调节功能,在饲料和食品行业应用广泛^[10]。其中,己酸(caproic acid,CA)成本低、来源广,用于青贮饲料添加剂可加速青贮发酵,有效抑制酵母菌和霉菌增殖,延缓pH上升和温度升高,提高青贮有氧稳定性^[11-12]。研究表明,相比己酸,作为己酸和氧化锌复合物的己酸锌(ZnCA)展现出更强的协同抑菌作用^[13]。然而,通过稻壳调节青贮含水量,并进一步添加己酸和己酸锌抑制雨淋燕麦青贮中不良微生物发酵的研究鲜有报道。

基于此,本研究以雨淋后燕麦为原料,通过添加稻壳降低燕麦含水量,使其达到适宜青贮的含水量,并进一步分析添加己酸和己酸锌对雨淋后燕麦青贮80、210 d和有氧暴露6 d后发酵品质、营养成分和微生物数量的影响,探究稻壳调节与添加己酸、己酸锌协同作用对青贮品质及有氧稳定性的影响,为青贮提供新的技术思路,从而推动畜牧业可持续发展。

1 材料与方法

1.1 试验材料

燕麦取自于河南农业大学新乡实验基地,品种为贝勒Ⅱ燕麦,收获前遇降雨,待地干后于2023年6月7日收获。稻壳来自2023年河南新乡收获的黄金晴粳稻,粉碎后使用。己酸购自上海某生化科技有限公司。己酸锌在河南工业大学生物工程学院实验室中合成^[14]。

1.2 试验设计

燕麦全株刈割后在当地进行青贮处理,用铡刀将其切割至2 cm左右。燕麦含水量为78.43%,通过添加稻壳(4%)降低燕麦含水量至74.58%。因此,将燕麦分为高含水量(78.43%)组和低含水量(74.58%)组。每种含水量燕麦添加剂处理为:1)对照组(CK组),无添加剂;2)己酸组(CA组),添加0.5%己酸;3)己酸锌组(ZnCA组),添加0.5%己酸锌。于青贮发酵80、210 d和有氧暴露6 d后测定发酵品质、营养成分及微生物数量。将添加剂喷洒到原料中并充分搅拌后装入青贮袋(22 cm×32 cm;中国东莞沧州华亮包装装饰有限公司),每袋装500 g,共54袋(3种添加剂处理×2种含水量×3个时间点×3个重复)。在充分混合后进行真空密封,并在室温(20~22 ℃)下保存。

1.3 测定指标及方法

1.3.1 发酵品质

发酵品质测定时,将燕麦青贮样品(20 g)与180 mL无菌蒸馏水混合后置于4 ℃培养箱中静置24 h。将浸提液过滤后离心取上清液,使用pH计(PHS-3C,上海仪电有限公司)测定pH,通过高效液相色谱(HPLC)法测定有机酸(乳酸、乙酸、丙酸和丁酸)含量,采用Broderick等^[15]的苯酚-次氯酸比色法测定氨态氮含量。

1.3.2 营养成分

取燕麦原料和燕麦青贮样品约200 g,在65 ℃烘箱中烘干48 h,参照GB/T 6435—2014的方法测定干物质含量。燕麦原料和燕麦青贮样品烘干后粉碎过1 mm筛,用于其他营养成分测定。采用凯氏定氮法^[16]测定粗蛋白质含量;采用Van Soest等^[17]的方法测定中性洗涤纤维和酸性洗涤纤维含量,半纤维素含量为中性洗涤纤维与酸性洗涤纤维之差;采用蒽酮比色法^[18]测定水溶性碳水化合物含量。

1.3.3 微生物数量

将燕麦青贮样品(20 g)与180 mL无菌蒸馏水混合,制备梯度稀释液(10^-1~10^-6)。取20 μL稀释样本涂布于选择性固体培养基,通过平板计数法进行微生物数量测定。乳酸菌用MRS琼脂培养基培养,30 ℃厌氧培养48 h;霉菌和酵母菌用孟加拉红培养基培养,28 ℃恒温培养箱培养48 h;大肠杆菌用伊红美蓝琼脂培养基培养,37 ℃恒温培养48 h。所有培养基均购自北京奥博星生物科技有限公司。微生物数量以每克鲜物质(FM)菌落形成单位取以10为底的对数[lg(CFU/g FM)]表示^[19]。

1.4 数据统计与分析

采用Excel 2021对数据进行初步整理,采用SPSS 27.0软件对燕麦青贮的发酵品质、营养成分和微生物数量进行双因素方差分析,利用Duncan氏多重比较法进行组间平均值的差异分析,P<0.05为差异显著。

2 结果

2.1 燕麦原料特性

如表1所示,燕麦初始pH为6.09,干物质含量为215.72 g/kg,粗蛋白质含量为94.07 g/kg DM,水溶性碳水化合物含量为83.56 g/kg DM,中性洗涤纤维、酸性洗涤纤维和半纤维素含量分别为618.13、421.72、196.41 g/kg DM。

表1 燕麦原料特性

Table 1 Oat raw material characteristics

项目 Items	含量 Content
pH	6.09±0.06
干物质 DM/(g/kg)	215.72±6.87
水溶性碳水化合物 WSC/(g/kg DM)	83.56±0.91
中性洗涤纤维 NDF/(g/kg DM)	618.13±5.19
酸性洗涤纤维 ADF/(g/kg DM)	421.72±6.07
半纤维素 HC/(g/kg DM)	196.41±1.09
粗蛋白质 CP/(g/kg DM)	94.07±0.03

2.2 添加剂和含水量对燕麦青贮80 d后发酵品质的影响

如表2所示,主效应分析表明,添加剂和含水量的交互效应显著影响pH及氨态氮、丙酸和丁酸含量(P<0.05);添加剂显著影响pH及氨态氮、乳酸、乙酸、丙酸和丁酸含量(P<0.05),CA组的pH和丁酸含量显著高于CK组(P<0.05),CA组和ZnCA组的氨态氮、乳酸、乙酸含量显著低于CK组(P<0.05),CA组和ZnCA组的丙酸含量显著高于CK组(P<0.05);含水量显著影响氨态氮、乳酸、乙酸、丙酸和丁酸含量(P<0.05),高含水量组的氨态氮、乳酸、乙酸、丙酸和丁酸含量显著高于低含水量组(P<0.05)。

表2 添加剂和含水量对燕麦青贮80 d后发酵品质的影响

Table 2 Effects of additives and moisture content on fermentation quality after 80 days of oat silage

项目 Items		pH	氨态氮 NH₃-N/ (g/kg TN)	乳酸 LA/ (g/kg DM)	乙酸 AA/ (g/kg DM)	丙酸 PA/ (g/kg DM)	丁酸 BA/ (g/kg DM)
含水量 Moisture content	添加剂 Additives
高 High	CK	3.98^b	128.21^a	114.65	32.50	7.42^d	24.11^a
	CA	3.99^b	53.99^d	70.43	6.39	13.72^b	ND
	ZnCA	4.01^a	72.97^c	94.56	8.01	17.22^a	ND
低 Low	CK	3.93^b	115.67^b	94.30	24.01	10.06^cd	ND
	CA	4.17^a	54.49^d	52.82	3.40	9.42^cd	26.56^a
	ZnCA	3.99^b	49.33^d	69.69	3.11	12.14^bc	ND
SEM		0.022	7.719	5.054	2.762	0.829	3.371
主效应 Main effects
含水量 Moisture content	高 High	4.00	85.06^a	93.21^a	15.63^a	12.79^a	28.70^a
	低 Low	4.03	73.16^b	72.27^b	10.17^b	10.54^b	8.85^b
添加剂 Additives	CK	3.96^b	121.94^a	104.48^a	28.25^a	8.74^c	12.06^b
	CA	4.08^a	54.24^b	61.62^c	4.90^b	11.57^b	28.89^a
	ZnCA	4.00^ab	61.15^b	82.13^b	5.56^b	14.68^a	15.38^b
P值 P-value
含水量 Moisture content		0.235	<0.001	<0.001	<0.001	0.008	<0.001
添加剂 Additives		0.012	<0.001	<0.001	<0.001	<0.001	<0.001
交互效应 Interaction effect		0.011	0.024	0.457	0.119	<0.001	<0.001

	TN:总氮;CK:无添加;CA:己酸;ZnCA:己酸锌;SEM:均值标准误。同列数据肩标不同小写字母表示差异显著(P<0.05),相同或无字母表示差异不显著(P>0.05)。下表同。
	TN: total nitrogen; CK: no addition; CA: caproic acid; ZnCA: zinc caproate; SEM: standard error of mean. In the same column, values with different small letter superscripts mean significant difference (P<0.05), while with the same or no letter superscripts mean no significant difference (P>0.05). The same as below.

2.3 添加剂和含水量对燕麦青贮80 d后营养成分及微生物数量的影响

如表3所示,主效应分析表明,添加剂和含水量的交互效应显著影响水溶性碳水化合物和粗蛋白质含量(P<0.05);添加剂显著影响干物质、水溶性碳水化合物和粗蛋白质含量以及乳酸菌数量(P<0.05),ZnCA组的干物质含量显著高于CK组(P<0.05),CA组和ZnCA组的水溶性碳水化合物含量显著高于CK组(P<0.05),CA组的粗蛋白质含量显著高于CK组(P<0.05),CA组和ZnCA组的乳酸菌数量显著低于CK组(P<0.05);含水量显著影响干物质、水溶性碳水化合物和粗蛋白质含量(P<0.05),高含水量组的粗蛋白质含量显著高于低含水量组(P<0.05),高含水量组的干物质和水溶性碳水化合物含量显著低于低含水量组(P<0.05)。此外,各组在各含水量下均未检出霉菌、酵母菌和大肠杆菌。

表3 添加剂和含水量对燕麦青贮80 d后营养成分及微生物数量的影响

Table 3 Effects of additives and moisture content on nutrients and microbial number after 80 days of oat silage

项目 Items		干物质 DM/ (g/kg)	水溶性碳水化合物 WSC/ (g/kg DM)	粗蛋白质 CP/ (g/kg DM)	中性洗涤纤维 NDF/ (g/kg DM)	酸性洗涤纤维 ADF/ (g/kg DM)	半纤维素 HC/ (g/kg DM)	乳酸菌 LAB/ [lg (CFU/ g FM)]	霉菌 Mould/ [lg (CFU/ g FM)]	酵母菌 Yeast/ [lg (CFU/ g FM)]	大肠杆菌 E.coli/ [lg (CFU/ g FM)]
含水量 Moisture content	添加剂 Additives
高 High	CK	191.73	12.49^c	91.87^b	644.91	444.94	199.98	7.37	ND	ND	ND
	CA	194.78	17.27^b	94.23^a	643.32	420.42	222.90	4.75	ND	ND	ND
	ZnCA	206.50	13.85^c	81.66^e	638.64	418.18	220.46	3.18	ND	ND	ND
低 Low	CK	214.03	8.38^c	79.00^f	648.42	445.01	203.41	7.26	ND	ND	ND
	CA	221.37	33.77^a	88.16^d	660.67	434.54	226.12	5.85	ND	ND	ND
	ZnCA	220.28	16.46^b	89.66^c	649.70	417.23	232.47	2.91	ND	ND	ND
SEM		2.931	1.961	1.320	5.099	4.715	6.247	0.545
主效应 Main effects
含水量 Moisture content	高 High	197.67^b	14.54^b	89.25^a	642.29	427.84	214.45	5.10
	低 Low	218.56^a	19.54^a	85.61^b	652.93	432.26	220.67	5.34
添加剂 Additives	CK	202.88^b	10.44^c	85.44^b	646.66	444.97	201.69	7.32^a
	CA	208.08^b	25.52^a	91.20^a	651.99	427.48	224.51	5.30^b
	ZnCA	213.39^a	15.16^b	85.66^b	644.17	417.70	226.46	3.05^b
P值 P-value
含水量 Moisture content		<0.001	<0.001	<0.001	0.372	0.626	0.646	0.766
添加剂 Additives		<0.001	<0.001	<0.001	0.853	0.074	0.273	<0.001
交互效应 Interaction effect		0.056	<0.001	<0.001	0.887	0.744	0.953	0.751

ND:未检出 not detected。下表同 the same as below。

2.4 添加剂和含水量对燕麦青贮210 d后发酵品质的影响

如表4所示,主效应分析表明,添加剂和含水量的交互效应显著影响pH及氨态氮、乳酸、乙酸和丁酸含量(P<0.05);添加剂显著影响pH及氨态氮、乳酸、乙酸、丙酸和丁酸含量(P<0.05),CA组和ZnCA组的pH及氨态氮和乙酸含量显著低于CK组(P<0.05),CA组和ZnCA组的丙酸含量显著高于CK组(P<0.05),ZnCA组的乳酸含量显著高于CK组(P<0.05);含水量显著影响氨态氮、乳酸和乙酸含量(P<0.05),高含水量组的氨态氮、乳酸和乙酸含量显著高于低含水量组(P<0.05)。此外,ZnCA组在各含水量下均未检出丁酸。

表4 添加剂和含水量对燕麦青贮210 d后发酵品质的影响

Table 4 Effects of additives and moisture content on fermentation quality after 210 days of oat silage

项目 Items		pH	氨态氮 NH₃-N/ (g/kg TN)	乳酸 LA/ (g/kg DM)	乙酸 AA/ (g/kg DM)	丙酸 PA/ (g/kg DM)	丁酸 BA/ (g/kg DM)
含水量 Moisture content	添加剂 Additives
高 High	CK	4.37^b	126.34^a	61.92^a	43.13^a	6.69	21.10^a
	CA	4.18^cd	54.37^c	51.28^ab	5.45^c	11.05	6.52^b
	ZnCA	4.19^cd	77.20^b	59.44^a	7.33^c	13.31	ND
低 Low	CK	4.45^a	114.08^a	27.64^c	28.17^b	7.33	ND
	CA	4.20^c	54.67^c	44.88^b	4.29^c	8.65	24.69^a
	ZnCA	4.14^d	49.09^c	58.67^ab	1.92^c	14.55	ND
SEM		0.028	7.538	3.224	3.781	0.810	2.560
主效应 Main effects
含水量 Moisture content	高 High	4.25	85.97^a	57.55^a	18.64^a	10.35	9.21
	低 Low	4.26	72.61^b	43.73^b	11.46^b	10.18	8.23
添加剂 Additives	CK	4.41^a	120.21^a	44.78^b	35.65^a	7.01^c	10.55^b
	CA	4.19^b	54.52^b	48.08^b	4.87^b	9.85^b	15.60^a
	ZnCA	4.17^b	63.15^b	59.05^a	4.63^b	13.93^a	ND^c
P值 P-value
含水量 Moisture content		0.317	0.003	0.002	0.002	0.856	0.444
添加剂 Additives		<0.001	<0.001	0.017	<0.001	<0.001	<0.001
交互效应 Interaction effect		0.007	0.022	0.005	0.024	0.265	<0.001

2.5 添加剂和含水量对燕麦青贮210 d后营养成分及微生物数量的影响

如表5所示,主效应分析表明,添加剂和含水量的交互效应显著影响干物质、水溶性碳水化合物和粗蛋白质含量(P<0.05);添加剂显著影响干物质、水溶性碳水化合物、粗蛋白质、酸性洗涤纤维含量以及乳酸菌数量(P<0.05),CA组和ZnCA组的水溶性碳水化合物含量显著高于CK组(P<0.05),CA组和ZnCA组的乳酸菌数量显著低于CK组(P<0.05);含水量显著影响干物质、水溶性碳水化合物和粗蛋白质含量(P<0.05),高含水量组的粗蛋白质含量显著高于低含水量组(P<0.05),高含水量组的干物质和水溶性碳水化合物含量显著低于低含水量组(P<0.05)。此外,各组在各含水量下均未检出霉菌、酵母菌和大肠杆菌。

表5 添加剂和含水量对燕麦青贮210 d后营养成分及微生物数量的影响

Table 5 Effects of additives and moisture content on nutrients and microbial number after 210 days of oat silage

项目 Items		干物质 DM/ (g/kg)	水溶性碳水化合物 WSC/ (g/kg DM)	粗蛋白质 CP/ (g/kg DM)	中性洗涤纤维 NDF/ (g/kg DM)	酸性洗涤纤维 ADF/ (g/kg DM)	半纤维素 HC/ (g/kg DM)	乳酸菌 LAB/ [lg (CFU/ g FM)]	霉菌 Mould/ [lg (CFU/ g FM)]	酵母菌 Yeast/ [lg (CFU/ g FM)]	大肠杆菌 E.coli/ [lg (CFU/ g FM)]
含水量 Moisture content	添加剂 Additives
高 High	CK	189.37^b	7.48^c	87.94^b	606.18	385.37	220.80	7.88	ND	ND	ND
	CA	191.99^b	23.59^b	93.89^a	645.31	437.25	208.06	5.99	ND	ND	ND
	ZnCA	218.39^a	18.10^b	78.94^d	648.36	423.67	224.69	6.46	ND	ND	ND
低 Low	CK	221.39^a	6.83^c	85.68^c	622.80	360.91	261.89	8.43	ND	ND	ND
	CA	229.18^a	47.86^a	84.42^c	693.33	489.79	203.54	5.74	ND	ND	ND
	ZnCA	225.64^a	21.96^b	88.38^b	605.39	416.97	188.42	4.07	ND	ND	ND
SEM		4.077	3.457	1.105	10.605	12.416	7.912	0.397
主效应 Main effects
含水量 Moisture content	高 High	199.91^b	16.39^b	86.92^a	633.28	415.43	217.85	6.78
	低 Low	225.40^a	25.55^a	86.16^b	640.51	422.56	217.95	6.08
添加剂 Additives	CK	205.38^b	7.16^c	86.81^b	614.49	373.14^b	241.35	8.15^a
	CA	210.58^b	35.73^a	89.15^a	669.32	463.52^a	205.80	5.87^b
	ZnCA	222.01^a	20.03^b	83.66^c	626.87	420.32^ab	206.55	5.27^b
P值 P-value
含水量 Moisture content		<0.001	<0.001	0.047	0.698	0.699	0.994	0.153
添加剂 Additives		<0.001	<0.001	<0.001	0.070	0.005	0.084	<0.001
交互效应 Interaction effect		0.005	<0.001	<0.001	0.159	0.229	0.099	0.056

2.6 添加剂和含水量对燕麦青贮有氧暴露6 d后pH、干物质含量和微生物数量的影响

如表6所示,主效应分析表明,添加剂、含水量及二者交互效应显著影响pH、干物质含量和乳酸菌数量(P<0.05);CA组和ZnCA组的pH和乳酸菌数量显著低于CK组(P<0.05),CA组和ZnCA组的干物质含量显著高于CK组(P<0.05);高含水量组的pH显著高于低含水量组(P<0.05),高含水量组的干物质含量和乳酸菌数量显著低于低含水量组(P<0.05)。此外,CA组和ZnCA组在各含水量下均未检出霉菌和酵母菌;ZnCA组在各含水量下均未检出大肠杆菌,CA组仅在高含水量下未检出大肠杆菌。

表6 添加剂和含水量对燕麦青贮有氧暴露6 d后pH、干物质含量和微生物数量的影响

Table 6 Effects of additives and moisture content on pH, dry matter content and microbial number after aerobic exposure 6 days of oat silage

项目 Items		pH	干物质 DM/ (g/kg)	乳酸菌 LAB/ [lg(CFU/ g FM)]	霉菌 Mould/ [lg(CFU/ g FM)]	酵母菌 Yeast/ [lg(CFU/ g FM)]	大肠杆菌 E.coli/ [lg(CFU/ g FM)]
含水量 Moisture content	添加剂 Additives
高 High	CK	4.69^a	188.17^c	8.26^a	3.83	6.29	7.34
	CA	4.23^c	194.03^c	4.82^bc	ND	ND	ND
	ZnCA	4.26^c	217.05^b	3.81^c	ND	ND	ND
低 Low	CK	4.45^b	216.24^b	8.00^a	ND	6.27	ND
	CA	4.28^c	235.75^a	5.70^b	ND	ND	3.32
	ZnCA	4.25^c	224.94^b	7.79^a	ND	ND	ND
SEM		0.041	4.167	0.438	0.379	0.920	0.202
主效应 Main effects
含水量 Moisture content	高 High	4.39^a	199.75^b	5.63^b	1.28	2.10	2.45
	低 Low	4.33^b	225.64^a	7.17^a	ND	2.10	1.10
添加剂 Additives	CK	4.57^a	202.21^c	8.13^a	1.92	6.28	3.67
	CA	4.25^b	214.89^b	5.26^b	ND	ND	1.66
	ZnCA	4.25^b	221.00^a	5.80^b	ND	ND	ND
P值 P-value
含水量 Moisture content	<0.001	<0.001	<0.001
添加剂 Additives	<0.001	<0.001	<0.001
交互效应 Interaction effect	<0.001	<0.001	<0.001

3 讨论

3.1 雨淋后燕麦原料特性

雨淋后燕麦原料干物质含量为215.72 g/kg,含水量为78.43%。这一含水量高于理想青贮含水量范围,过高的含水量易导致青贮过程中腐败菌滋生,增加养分流失。青贮原料水溶性碳水化合物含量是预测青贮难易的重要因素^[20]。本研究中,雨淋后燕麦水溶性碳水化合物含量为83.56 g/kg DM,适宜乳酸菌发酵;此外,雨淋后燕麦中性洗涤纤维含量为618.13 g/kg DM,酸性洗涤纤维含量为421.72 g/kg DM,半纤维素含量为196.41 g/kg DM,与赵桂琴等^[21]研究结果一致,表明雨淋对燕麦纤维组分影响较小。

3.2 添加剂和含水量对燕麦青贮发酵品质的影响

青贮饲料的pH和有机酸含量是评价青贮品质的关键性指标,一般认为饲草青贮饲料的pH小于4.2时可以取得较好的发酵品质^[22-25]。在本研究中,青贮80 d后所有组的pH均降低至4.2以下(3.93~4.17)。然而,随着青贮时间延长,pH缓慢上升,青贮210 d后,无论高含水量还是低含水量的CK组pH均超过4.2(4.37和4.45),而CA组和ZnCA组的pH仍维持在4.2以下,且有氧暴露6 d后,所有组的pH均低于CK组,表明添加己酸和己酸锌能保证燕麦长时间青贮及有氧暴露后的良好发酵品质。本研究中,青贮80 d后,与CK组相比,CA组和ZnCA组的乳酸含量降低;且相较于高含水量组,低含水量组的乳酸含量较低,这可能是由于含水量降低抑制了微生物活性,乳酸菌代谢减缓,从而导致乳酸含量降低^[4,26]。此外,己酸和己酸锌也抑制了部分乳酸菌生长,减少了乳酸生成^[27]。青贮饲料中氨态氮含量可表示青贮蛋白质的降解程度,其产生受植物蛋白酶、微生物活动等多因素影响^[28]。较高的含水量容易造成青贮饲料中不良微生物如梭状芽孢杆菌、肠杆菌和芽孢杆菌的活性增强,发生脱氨作用和蛋白质水解,从而发生腐败^[29-30]。此外,青贮饲料中丁酸由梭状芽孢杆菌等不良微生物代谢产生,这类微生物会分解氨基酸,导致蛋白质损失^[31-32]。在本研究中,青贮80和210 d后,与CK组相比,CA组和ZnCA组的氨态氮含量降低,表明添加稻壳、己酸和己酸锌均能有效降低燕麦青贮的蛋白质降解。

3.3 添加剂和含水量对燕麦青贮营养成分的影响

干物质、水溶性碳水化合物和粗蛋白质含量是评价青贮饲料营养品质的主要营养指标。水溶性碳水化合物作为微生物发酵的底物,其含量变化反映青贮营养消耗程度^[26]。本研究中,青贮80和210 d后,与CK组相比,CA组和ZnCA组的水溶性碳水化合物含量升高,这可能是因为己酸和己酸锌抑制了微生物代谢,减少了对碳水化合物的消耗,从而保留更多营养成分。低含水量组燕麦青贮发酵80和210 d后,干物质含量高于高含水量组,表明添加稻壳、己酸和己酸锌对雨淋后燕麦青贮的营养成分保留较好。

3.4 添加剂和含水量对燕麦青贮微生物的影响

青贮过程中的微生物群落对调控青贮发酵起关键作用。一般良好的青贮饲料中乳酸菌占主导地位^[33-34]。然而Li等^[35]研究发现,青贮饲料中添加丁香显著抑制了乳酸菌的生长,但丁香通过降低氨态氮和非蛋白氮含量来降低青贮的蛋白质损失,提高了青贮品质。此外,Wang等^[27]向全株玉米青贮中添加己酸发现,青贮45 d过程中己酸组乳酸菌数量和氨态氮含量均低于对照组,表明青贮前期添加己酸加速了pH的下降,有效抑制了霉菌和酵母菌的生长,提高了青贮品质。这与本研究结果类似,青贮发酵和有氧暴露后氨态氮含量较低的CA组和ZnCA组的乳酸菌数量降低。可能原因是添加剂对微生物的生长产生了一定的抑制作用,使得部分不耐受的乳酸菌数量降低,但具有较强生长能力和产酸能力的乳酸菌依旧存活,同时添加剂也有效抑制了大肠杆菌等产氨细菌的繁殖,减少了蛋白质降解,提高了青贮饲料的发酵品质和有氧稳定性^[35]。

4 结论

己酸和己酸锌都能通过降低氨态氮含量来提高雨淋后燕麦青贮的发酵品质,通过抑制大肠杆菌、酵母菌和霉菌的生长提高有氧稳定性。其中,通过添加稻壳降低雨淋后燕麦含水量,并进一步添加己酸锌,有效抑制了青贮过程中的丁酸发酵,发酵品质最佳。

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