Effects of Lactic Acid Bacteria Preparation on Fermentation Quality, Nutritional Value and Nutrient in Vitro Degradation Rates of Mixed Silage of Corn Straw and Suaeda salsa with Different Ratios

ZHANG Xianglun; ZHAO Hongbo; GAO Shang; JI Kaixi; YANG Ming; SHENG Qingkai; LIU Xiaomu; WANG Lu

doi:10.12418/CJAN2025.453

2025 , Vol. 37 >Issue 8: 5584 - 5594

DOI: https://doi.org/10.12418/CJAN2025.453

RESEARCH PAPER

Effects of Lactic Acid Bacteria Preparation on Fermentation Quality, Nutritional Value and Nutrient in Vitro Degradation Rates of Mixed Silage of Corn Straw and Suaeda salsa with Different Ratios

ZHANG Xianglun ^,¹ ,
ZHAO Hongbo ¹ ,
GAO Shang ^,²^,^** ,
JI Kaixi ¹ ,
YANG Ming ¹^,³ ,
SHENG Qingkai ¹ ,
LIU Xiaomu ¹ ,
WANG Lu ²^,⁴

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¹ Shandong Province Key Laboratory of Animal Microecologics and Efficient Production of Livestock and Poultry, Key Laboratory of Livestock and Poultry Multi-Omics of Ministry of Agriculture and Rural Affairs, Institute of Animal Science and Veterinary Medicine, Shandong Academy of Agricultural Sciences, Ji’nan 250100, China
² Shandong Academy of Agricultural Sciences, Ji’nan 250100, China
³ College of Animal Science and Technology, Shandong Agricultural University, Tai’an 271018, China
⁴ National Center of Technology Innovation for Comprehensive Utilization of Saline-Alkali Land, Dongying 257347, China

^**professor, E-mail: gaoshangd@126.com

^*Contributed equally

Received date: 2025-01-03

Online published: 2025-08-14

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Abstract

This experiment was conducted to study the effects of lactic acid bacteria preparation on fermentation quality, nutritional value and nutrient in vitro degradation rates of mixed silage of corn straw and Suaeda salsa with different ratios. The fresh corn straw and Suaeda salsa were selected with 30 kg each, and mixed based on 5 mixing ratios (100% corn straw, 75% corn straw and 25% Suaeda salsa, 50% corn straw and 50% Suaeda salsa, 25% corn straw and 75% Suaeda salsa, 100% Suaeda salsa), named 100∶0, 75∶25, 50∶50, 25∶75 and 0∶100 groups, with 2 treatments in each ratio, included control (CON, sprayed sterile normal saline) and Lactobacillus plantarum group (LP, sprayed 1×10⁶ CFU/g Lactobacillus plantarum). Each treatment contained 4 replicates with 1 kg per replicate, and anaerobic fermentation for 60 days. The results showed as follows: 1) the yeast number of 25∶75 and 0∶100 groups was significantly lower than that of other groups (P<0.05), and the lactic acid bacteria number of 50∶50, 25∶75 and 0∶100 groups was significantly higher than that of other groups (P<0.05). The lactic acid bacteria preparation had no significant effects on yeast and lactic acid bacteria numbers (P>0.05). 2) The pH of 0∶100 group was significantly higher than that of other groups (P<0.05), the lactic acid content of 50∶50 and 25∶75 groups was significantly higher than that of other groups (P<0.05), and the acetic acid, propionic acid and butyric acid contents of 0∶100 group was significantly higher than that of other groups (P<0.05). The lactic acid bacteria preparation had no significant effects on pH and organic acid contents (P>0.05). 3) With the Suaeda salsa ratio increased, the organic matter, neutral detergent fiber and acid detergent fiber contents were significantly decreased (P<0.05), and the crude protein and ether extract contents were significantly increased (P<0.05). The ammonia nitrogen content of 0∶100 group was significantly higher than that of other groups (P<0.05), and the water-soluble carbohydrate content was significantly lower than that of other groups (P<0.05). The lactic acid bacteria preparation had no significant effects on nutrient components (P>0.05). 4) At 24, 48 and 72 hours after in vitro digestion, the in vitro degradation rate of crude protein of 50∶50 and 25∶75 groups was significantly higher than that of other groups (P<0.05), and the in vitro degradation rate of organic matter of 0∶100 group was significantly higher than that of other groups (P<0.05). The lactic acid bacteria had no significant effects on in vitro degradation rates of nutrients at each time point (P>0.05). In conclusion, comprehensive all indices, the recommended mixing ratios of mixed silage of corn straw and Suaeda salsa are 75∶25 and 50∶50.

Key words： corn straw; Suaeda salsa; mixing ratio; lactic acid bacteria; silage

Cite this article

ZHANG Xianglun , ZHAO Hongbo , GAO Shang , JI Kaixi , YANG Ming , SHENG Qingkai , LIU Xiaomu , WANG Lu . Effects of Lactic Acid Bacteria Preparation on Fermentation Quality, Nutritional Value and Nutrient in Vitro Degradation Rates of Mixed Silage of Corn Straw and Suaeda salsa with Different Ratios[J]. Chinese Journal of Animal Nutrition, 2025 , 37(8) : 5584 -5594 . DOI: 10.12418/CJAN2025.453

我国是盐碱地大国,可利用的各类盐碱地资源规模约为5亿亩(1亩≈667 m²),盐碱地作为重要的后备耕地资源,提高盐碱地综合利用对于保障国家粮食安全、端牢中国饭碗具有重要战略意义^[1]。我国饲草资源紧张、缺口大,每年需要大量依赖进口满足畜牧业养殖需求。我国沿海地区分布着大面积的盐碱地,包括沿海滩涂(约2万km²)、沿海地区和海岛海岸(约1.8万km²)^[2]。在盐碱地种植耐盐碱牧草,对于饲草供给和盐碱地改造提升具有重要作用。盐地碱蓬(Suaeda salsa)是一种藜科耐盐碱植物,生长于海滨、荒漠等地,耐盐性较强、可降低土壤盐分及改良土壤^[3]。课题组前期已证实盐地碱蓬具有独特的耐盐机制^[4],对于其饲用价值尚未开展系统研究。有研究报道,盐地碱蓬粗蛋白质和盐分含量较高,但水溶性碳水化合物含量较低^[5],不适宜单独青贮。玉米秸秆是常用的饲料原料,水溶性碳水化合物含量较高,但粗蛋白质含量偏低^[6]。如果将玉米秸秆和盐地碱蓬混贮,可以充分发挥二者营养优势,补足营养短板,提高青贮品质。

关于盐地碱蓬的研究多集中于其耐盐机制分析^[7-8]及对盐碱地土壤的改良^[9-10]等方面,在饲料化加工及利用方面的报道还较少。Wang等^[11]分析了不同盐度灌溉条件下盐地碱蓬营养成分变化,发现其自身盐分含量较稳定,粗蛋白质、中性洗涤纤维、酸性洗涤纤维和微量元素含量适宜,营养价值较高。徐晶等^[12-13]先后研究了盐地碱蓬发酵前后营养成分变化及不同发酵时间对盐地碱蓬发酵品质的影响,发现其具有较高的饲用价值,具有制作优质青贮饲料的潜力。位孟聪^[14]和张福海等^[15]在生猪和阿勒泰羊上饲喂风干盐地碱蓬粉,发现其在改善动物生长性能和屠宰性能、提高经济效益方面具有显著效果。已有研究主要围绕盐地碱蓬营养成分、发酵参数及风干形式的盐地碱蓬饲喂进行了初步探讨,关于盐地碱蓬饲用价值及与玉米秸秆混贮方面的研究仍需深入开展,以促进盐碱地饲草资源的开发与利用。基于此,本研究以新鲜玉米秸秆和盐地碱蓬为研究对象,通过研究混合比例和乳酸菌制剂对二者混贮发酵品质、营养价值及营养物质体外降解率的影响,明确发酵关键技术参数,以期为我国盐碱地饲草资源开发及高效利用提供数据支撑,助力盐碱地改造提升。

1 材料与方法

1.1 试验设计

试验于2024年10—12月开展,选用新鲜玉米秸秆、盐地碱蓬各20 kg,分别切短粉碎至1~2 cm,按不同混合比例(100%玉米秸秆、75%玉米秸秆和25%盐地碱蓬、50%玉米秸秆和50%盐地碱蓬、25%玉米秸秆和75%盐地碱蓬、100%盐地碱蓬)将二者混合,分别记为100∶0、75∶25、50∶50、25∶75、0∶100组,每个比例组下设2个处理,分别为对照(CON,喷洒无菌生理盐水)和植物乳杆菌(LP,喷洒1×10⁶ CFU/g)。植物乳杆菌活菌数为1×10¹⁰ CFU/g。选用的青贮发酵袋规格为23 cm×40 cm,聚乙烯材料,装有单向排气阀。每个处理下设4个重复,每个重复装1 kg,封口后用真空泵将袋内空气排出,于室温下避光厌氧发酵60 d,之后开袋取样,测定相关指标。玉米秸秆和盐地碱蓬营养水平见表1。

表1 玉米秸秆和盐地碱蓬营养水平(干物质基础)

Table 1 Nutrient levels of corn straw and Suaeda salsa (DM basis) %

项目 Items	干物质(鲜样基础) DM (fresh sample basis)	有机物 OM	粗蛋白质 CP	粗脂肪 EE	中性洗涤纤维 NDF	酸性洗涤纤维 ADF
玉米秸秆Corn straw	27.86	92.91	5.91	1.71	61.86	31.45
盐地碱蓬Suaeda salsa	17.16	77.81	19.89	6.67	35.04	18.75

1.2 样本采集及测定指标

1.2.1 微生物数量

每重复准确称取玉米秸秆和盐地碱蓬混贮样本20 g,加入180 mL无菌生理盐水,充分搅拌后匀浆,然后按10~10⁷倍数稀释。采用平板计数法测定微生物数量,霉菌和酵母菌采用马铃薯葡萄糖琼脂培养基进行计数,乳酸菌用MRS琼脂培养基进行计数。

1.2.2 发酵指标测定

每重复准确称取玉米秸秆和盐地碱蓬混贮样本20 g,加入180 mL蒸馏水,匀浆60 s后用4层纱布过滤,使用pH计(HI9025,意大利Hanna Instruments公司)测定pH。另取样本20 g,加入180 mL去离子水,匀浆后通过4层纱布和滤纸过滤,所得的液体分装后保存待测。乳酸含量采用对羟基联苯法^[16]测定;挥发性脂肪酸(VFA)含量采用高效气相色谱仪(GC-2010,日本岛津公司)测定,包括乙酸、丙酸和丁酸。

1.2.3 营养成分测定

分别取各重复玉米秸秆和盐地碱蓬混贮样品制备风干样本,干物质、有机物、粗蛋白质和粗脂肪含量采用AOAC(2015)^[17]方法测定,酸性洗涤纤维和中性洗涤纤维含量采用Van Soest等^[18]的方法测定。氨态氮(NH₃-N)含量采用苯酚-次氯酸钠比色法^[19]测定。水溶性碳水化合物含量采用蒽酮硫酸比色法^[20]测定。

1.2.4 营养物质体外降解率测定

选用3头体况良好、装有永久性瘤胃瘘管的西门塔尔杂交牛[体重(516±15) kg]采集瘤胃液,试验饲粮(干物质基础)为:全株玉米青贮45.0%,羊草15.0%,玉米27.0%,豆粕7.4%,干酒糟及其可溶物4.0%,氯化钠0.4%,小苏打0.4%,石粉0.4%,预混料0.4%。于晨饲1 h前采集瘤胃液,4层纱布过滤后置于预热的无氧保温瓶中保存,立即带回实验室,参考Menke等^[21]的方法配制体外消化液。准确称取0.5 g玉米秸秆和盐地碱蓬混贮样品于聚酯纤维袋中(规格为5 cm×5 cm,20 μm孔径),密封后放于100 mL发酵瓶中,加入60 mL体外消化液,充入二氧化碳后密封。将发酵瓶置于摇床中,于39 ℃、125 r/min条件下消化24、48和72 h后取样测定营养物质体外降解率,每个时间点3个重复,试验重复2次。计算公式如下:

营养物质体外降解率(%)=[(降解前样品营养物质含量-降解后样品营养物质含量)/降解前样品营养物质含量]×100。

1.3 数据统计

数据经Excel 2021整理后,采用SPSS 21.0软件中的单因素方差分析(one-way ANOVA)过程对各组数据进行统计分析,采用一般线性模型(general linear model,GLM)过程对主效应作用及主效应间的交互作用进行统计分析。3组以上数据多重比较采用Tukey法进行,2组数据比较采用独立样本t检验法进行,结果以平均值和均值标准误(SEM)表示,P<0.05为差异显著。

2 结果

2.1 乳酸菌制剂对不同比例玉米秸秆和盐地碱蓬混贮微生物数量的影响

各组青贮中均未出现霉菌。由表2可见,混合比例对混贮微生物数量有显著影响(P<0.05)。25∶75组和0∶100组酵母菌数量显著低于100∶0组、75∶25组和50∶50组(P<0.05),50∶50组、25∶75组和0∶100组乳酸菌数量显著高于100∶0组和75∶25组(P<0.05)。乳酸菌制剂对混贮微生物数量无显著影响(P>0.05)。混合比例和乳酸菌制剂的交互作用对混贮微生物数量无显著影响(P>0.05)。

表2 乳酸菌制剂对不同比例玉米秸秆和盐地碱蓬混贮微生物数量的影响

Table 2 Effects of lactic acid bacteria preparation on bacteria number of mixed silage of corn straw and Suaeda salsa with different ratios log₁₀(CFU/mL)

项目 Items	玉米秸秆∶盐地碱蓬Corn straw∶Suaeda salsa										SEM	混合比例 Mixing ratio					SEM	乳酸菌制剂 Lactic acid bacteria preparation		SEM	P值P-value
	100∶0		75∶25		50∶50		25∶75		0∶100			混合比例 Mixing ratio						乳酸菌制剂 Lactic acid bacteria preparation			混合比例 Mixing ratio	乳酸菌制剂 Lactic acid bacteria preparation	混合比例× 乳酸菌制剂 Mixing ratio× Lactic acid bacteria preparation
	100∶0		75∶25		50∶50		25∶75		0∶100			100∶0	75∶25	50∶50	25∶75	0∶100		CON	LP
	CON	LP	CON	LP	CON	LP	CON	LP	CON	LP		100∶0	75∶25	50∶50	25∶75	0∶100		CON	LP
酵母菌 Yeast	5.28^a	5.16^a	5.60^a	5.62^a	4.53^abc	4.99^ab	1.72^d	3.30^bcd	2.17^d	3.08^cd	0.242	5.22^a	5.61^a	4.76^a	2.51^b	2.63^b	0.248	3.86	4.43	0.157	<0.001	0.248	0.124
乳酸菌 Lactic acid bacteria	5.25^c	5.38^c	5.75^c	5.59^c	6.98^b	6.96^b	7.33^ab	7.13^b	8.05^a	8.08^a	0.170	5.32^c	5.67^c	6.97^b	7.23^b	8.06^a	0.120	6.67	6.63	0.076	<0.001	0.896	0.869

	CON:对照;LP:植物乳杆菌。同行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。
	CON: control: LP: Lactobacillus plantarum. In the same row, 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.

2.2 乳酸菌制剂对不同比例玉米秸秆和盐地碱蓬混贮pH及有机酸含量的影响

由表3可见,混合比例对混贮pH及有机酸含量有显著影响(P<0.05)。随盐地碱蓬比例的升高,混贮pH升高,0∶100组混贮pH显著高于其他各组(P<0.05);混贮中乳酸含量呈先升高后降低的变化趋势,50∶50组和25∶75组混贮中乳酸含量显著高于其他各组(P<0.05)。挥发性脂肪酸方面,0∶100组混贮中乙酸、丙酸和丁酸含量显著高于其他各组(P<0.05),其他各组之间差异不显著(P>0.05)。乳酸菌制剂对混贮pH及有机酸含量均无显著影响(P>0.05)。混合比例和乳酸菌制剂的交互作用对混贮pH及丁酸含量有显著影响(P<0.05)。

表3 乳酸菌制剂对不同比例玉米秸秆和盐地碱蓬混贮pH及有机酸含量的影响

Table 3 Effects of lactic acid bacteria preparation on pH and organic acid contents of mixed silage of corn straw and Suaeda salsa with different ratios

项目 Items	玉米秸秆∶盐地碱蓬Corn straw∶Suaeda salsa										SEM	混合比例 Mixing ratio					SEM	乳酸菌制剂 Lactic acid bacteria preparation		SEM	P值P-value
	100∶0		75∶25		50∶50		25∶75		0∶100			混合比例 Mixing ratio						乳酸菌制剂 Lactic acid bacteria preparation			混合比例 Mixing ratio	乳酸菌制剂 Lactic acid bacteria preparation	混合比例× 乳酸菌制剂 Mixing ratio× lactic acid bacteria preparation
	100∶0		75∶25		50∶50		25∶75		0∶100			100∶0	75∶25	50∶50	25∶75	0∶100		CON	LP
	CON	LP	CON	LP	CON	LP	CON	LP	CON	LP		100∶0	75∶25	50∶50	25∶75	0∶100		CON	LP
pH	3.48^e	3.51^e	3.57^e	3.54^e	3.71^de	3.67^de	3.97^c	3.90^cd	5.53^a	5.23^b	0.114	3.49^d	3.56^cd	3.69^c	3.93^b	5.38^a	0.037	4.05	3.97	0.023	<0.001	0.721	0.035
乳酸 Lactic acid/ (g/kg DM)	44.04^c	41.94^c	48.48^bc	47.86^bc	56.61^a	56.58^a	55.06^ab	57.76^a	4.74^e	7.80^d	3.018	42.99^c	48.17^b	56.60^a	56.41^a	6.27^d	1.071	41.79	42.39	0.678	<0.001	0.567	0.338
乙酸 Acetic acid/ (g/kg DM)	13.20^b	11.96^b	13.40^b	12.02^b	10.71^b	10.31^b	12.77^b	10.13^b	42.69^a	34.64^a	1.874	12.58^b	12.71^b	10.51^b	11.45^b	38.66^a	1.364	18.55	15.81	0.891	<0.001	0.424	0.304
丙酸 Propionic acid/ (g/kg DM)	0.03^b	0.04^b	0.03^b	0.03^b	0.02^b	0.05^b	0.04^b	0.03^b	0.31^a	0.27^a	0.019	0.03^b	0.03^b	0.03^b	0.04^b	0.29^a	0.025	0.09	0.08	0.016	<0.001	0.938	0.896
丁酸 Butyric acid/ (g/kg DM)	0.01^c	0.03^bc	0.02^bc	0.02^bc	0.02^bc	0.02^bc	0.01^c	0.02^bc	0.11^a	0.06^b	0.005	0.02^b	0.02^b	0.02^b	0.02^b	0.08^a	0.006	0.03	0.03	0.004	<0.001	0.519	0.002

2.3 乳酸菌制剂对不同比例玉米秸秆和盐地碱蓬混贮营养成分的影响

由表4可见,混合比例对混贮营养成分有显著影响(P<0.05)。随盐地碱蓬比例的升高,混贮中有机物、中性洗涤纤维及酸性洗涤纤维含量显著降低(P<0.05),粗蛋白质和粗脂肪含量显著升高(P<0.05)。0∶100组混贮中氨态氮含量显著高于其他各组(P<0.05),水溶性碳水化合物含量显著低于其他各组(P<0.05)。乳酸菌制剂对混贮营养成分均无显著影响(P>0.05)。混合比例和乳酸菌制剂的交互作用对混贮水溶性碳水化合物含量有显著影响(P<0.05)。

表4 乳酸菌制剂对不同比例玉米秸秆和盐地碱蓬混贮营养成分的影响

Table 4 Effects of lactic acid bacteria preparation on nutrient components of mixed silage of corn straw and Suaeda salsa with different ratios (DM basis)

项目 Items	玉米秸秆∶盐地碱蓬Corn straw∶Suaeda salsa										SEM	混合比例 Mixing ratio					SEM	乳酸菌制剂 Lactic acid bacteria preparation		SEM	P值P-value
	100∶0		75∶25		50∶50		25∶75		0∶100			混合比例 Mixing ratio						乳酸菌制剂 Lactic acid bacteria preparation			混合比例 Mixing ratio	乳酸菌制剂 Lactic acid bacteria preparation	混合比例× 乳酸菌制剂 Mixing ratio× lactic acid bacteria preparation
	100∶0		75∶25		50∶50		25∶75		0∶100			100∶0	75∶25	50∶50	25∶75	0∶100		CON	LP
	CON	LP	CON	LP	CON	LP	CON	LP	CON	LP		100∶0	75∶25	50∶50	25∶75	0∶100		CON	LP
有机物 OM/%	92.31^a	92.05^a	90.04^b	90.36^b	87.01^c	87.14^c	83.28^d	83.65^d	75.71^e	76.05^e	0.923	92.18^a	90.20^b	87.07^c	83.47^d	75.88^e	0.138	85.67	85.85	0.087	<0.001	0.924	0.477
粗蛋白质 CP/%	7.03^e	7.29^e	9.09^d	8.90^d	12.20^c	11.98^c	15.14^b	14.83^b	20.08^a	20.19^a	0.739	7.16^e	8.99^d	12.09^c	14.98^b	20.13^a	0.194	12.71	12.64	0.123	<0.001	0.962	0.807
粗脂肪 EE/%	2.93^f	2.94^f	4.12^e	4.27^e	5.04^de	5.49^cd	6.61^ab	6.18^bc	6.97^ab	7.36^a	0.250	2.94^e	4.19^d	5.26^c	6.40^b	7.16^a	0.138	5.13	5.25	0.087	<0.001	0.822	0.196
中性洗涤纤维 NDF/%	64.31^a	63.12^a	57.57^b	57.32^b	46.77^c	46.36^c	38.73^d	39.91^d	32.49^e	32.29^e	1.851	63.71^a	57.44^b	46.57^c	39.32^d	32.39^e	0.580	47.97	47.80	0.367	<0.001	0.963	0.705
酸性洗涤纤维 ADF/%	33.84^a	33.55^a	29.76^b	30.19^b	25.41^c	25.69^c	21.61^d	22.37^d	18.55^e	18.77^e	0.872	33.69^a	29.97^b	25.55^c	21.99^d	18.66^e	0.304	25.83	26.12	0.192	<0.001	0.873	0.812
氨态氮 NH₃-N/(g/kg)	62.16^b	59.18^b	67.15^b	55.05^b	60.56^b	62.31^b	78.60^b	59.41^b	182.05^a	167.85^a	7.495	64.66^b	61.10^b	61.44^b	69.01^b	174.95^a	5.246	91.70	80.76	3.321	<0.001	0.472	0.703
水溶性碳水化合物 WSC/(g/kg)	22.38^ab	18.16^b	19.02^ab	18.38^b	21.31^ab	20.62^ab	19.91^ab	24.21^a	10.18^c	12.63^c	0.724	20.27^ab	18.70^b	20.97^ab	22.06^a	11.40^c	0.802	18.56	18.80	0.507	<0.001	0.872	0.008

2.4 乳酸菌制剂对不同比例玉米秸秆和盐地碱蓬混贮营养物质体外降解率的影响

由表5可见,混合比例对混贮营养物质体外降解率有显著影响(P<0.05)。体外消化24 h时,随盐地碱蓬比例的升高,干物质和粗蛋白质体外降解率呈先升高后降低的变化趋势,其中25∶75组干物质体外降解率显著高于其他各组(P<0.05),50∶50组和25∶75组粗蛋白质体外降解率显著高于其他各组(P<0.05);有机物体外降解率逐渐升高,0∶100组有机物体外降解率显著高于其他各组(P<0.05);中性洗涤纤维和酸性洗涤纤维体外降解率呈先升高后降低的变化趋势,其中75∶25组中性洗涤纤维体外降解率显著高于其他各组(P<0.05),75∶25组和50∶50组酸性洗涤纤维体外降解率显著高于其他各组(P<0.05)。乳酸菌制剂对各营养物质体外降解率均无显著影响(P>0.05)。混合比例和乳酸菌制剂的交互作用对干物质、有机物、粗蛋白质和中性洗涤纤维体外降解率有显著影响(P<0.05)。

表5 乳酸菌制剂对不同比例玉米秸秆和盐地碱蓬混贮体外降解率的影响

Table 5 Effects of lactic acid bacteria preparation on in vitro degradation rates of mixed silage of corn straw and Suaeda salsa with different ratios %

项目 Items			玉米秸秆∶盐地碱蓬Corn straw:Suaeda salsa																				SEM		混合比例 Mixing ratio										SEM		乳酸菌制剂 Lactic acid bacteria preparation				SEM		P值P-value
			100∶0				75∶25				50∶50				25∶75				0∶100						混合比例 Mixing ratio												乳酸菌制剂 Lactic acid bacteria preparation						混合比例 Mixing ratio		乳酸菌制剂 Lactic acid bacteria preparation		混合比例× 乳酸菌制剂 Mixing ratio× lactic acid bacteria preparation
			100∶0				75∶25				50∶50				25∶75				0∶100						100∶0		75∶25		50∶50		25∶75		0∶100				CON		LP
			CON		LP		CON		LP		CON		LP		CON		LP		CON		LP				100∶0		75∶25		50∶50		25∶75		0∶100				CON		LP
干物质 DM	24 h		35.96^f		36.32^f		40.65^e		43.80^d		44.56^d		49.11^a		48.66^ab		49.69^a		46.25^c		47.13^bc		0.894		36.14^d		42.23^c		46.83^b		49.17^a		46.69^b		0.231		43.22		45.21		0.146		<0.001		0.272		<0.001
	48 h		45.42^c		45.27^c		46.61^bc		46.70^bc		46.25^c		49.76^a		49.71^a		49.56^a		49.31^ab		50.30^a		0.383		45.35^d		46.66^cd		48.00^bc		49.63^ab		49.81^a		0.403		47.46		48.32		0.255		<0.001		0.270		0.020
	72 h		55.22^b		59.19^a		51.49^bc		50.43^c		49.14^c		50.55^c		50.41^c		50.60^c		51.58^bc		52.36^bc		0.564		57.21^a		50.96^b		49.85^b		50.51^b		51.97^b		0.556		51.57		52.63		0.352		<0.001		0.356		0.052
有机物 OM		24 h		20.65^g		21.11^g		39.10^f		41.81^de		40.96^e		44.90^bc		41.85^de		43.39^cd		46.61^ab		47.49^a		1.725		20.88^d		40.45^c		42.93^b		42.62^b		47.05^a		0.251		37.84		39.74		0.159		<0.001		0.590		0.001
		48 h		32.45^c		32.28^c		45.19^b		44.70^b		42.70^b		45.65^b		42.86^b		43.24^b		49.79^a		50.77^a		1.107		32.37^d		44.94^b		44.18^bc		43.05^c		50.28^a		0.439		42.60		43.33		0.278		<0.001		0.748		0.083
		72 h		44.57^ef		49.50^abcd		50.13^abc		48.36^bcde		45.34^def		46.35^cdef		43.72^f		44.08^ef		52.22^ab		52.99^a		0.643		47.04^bc		49.25^b		45.84^cd		43.90^d		52.61^a		0.627		47.20		48.26		0.396		<0.001		0.421		0.020
粗蛋白质 CP		24 h		30.92^f		31.31^f		59.23^d		62.88^c		70.69^b		73.96^a		71.24^b		73.63^a		46.18^e		47.07^e		2.966		31.12^d		61.06^b		72.33^a		72.43^a		46.63^c		0.213		55.65		57.77		0.135		<0.001		0.723		<0.001
		48 h		37.65^f		37.49^f		63.57^d		66.34^c		71.32^b		74.04^a		71.42^b		73.74^a		49.11^e		50.11^e		2.574		37.57^d		64.95^b		72.68^a		72.58^a		49.61^c		0.318		58.61		60.34		0.201		<0.001		0.743		0.015
		72 h		53.09^e		57.25^d		68.74^c		71.27^bc		73.65^ab		75.19^a		72.29^ab		74.88^a		57.14^d		57.83^d		1.546		55.17^d		70.00^b		74.42^a		73.59^a		57.49^c		0.469		64.98		67.29		0.297		<0.001		0.466		0.144
中性洗涤纤维 NDF		24 h		25.12^b		25.55^b		30.48^a		32.24^a		24.58^b		24.94^b		24.96^b		23.87^bc		22.43^c		23.71^bc		0.556		25.33^b		31.36^a		24.76^b		24.42^b		23.07^c		0.298		25.51		26.06		0.188		<0.001		0.631		0.030
		48 h		35.59^a		35.42^a		34.53^a		34.03^a		25.81^bc		24.73^c		25.46^bc		23.67^c		27.23^bc		28.65^b		0.874		35.51^a		34.28^a		25.27^c		24.57^c		27.94^b		0.527		29.72		29.30		0.333		<0.001		0.815		0.306
		72 h		45.70^ab		50.52^a		41.37^bc		38.58^c		28.52^d		27.88^d		26.00^d		25.27^d		26.75^d		27.92^d		1.662		48.11^a		39.98^b		28.20^c		25.63^c		27.34^c		0.682		33.67		34.04		0.431		<0.001		0.914		0.010
酸性洗涤纤维 ADF		24 h		24.14^bc		24.57^ab		26.76^a		26.23^ab		25.93^ab		26.28^ab		21.14^d		22.06^cd		12.27^e		13.72^e		0.934		24.35^b		26.50^a		26.11^a		21.60^c		13.00^d		0.340		22.05		22.57		0.215		<0.001		0.786		0.356
		48 h		31.83^a		31.66^a		31.28^ab		27.68^bc		26.30^cd		26.44^c		22.41^de		22.00^e		13.63^f		13.87^f		1.206		31.75^a		29.48^a		26.37^b		22.20^c		13.75^d		0.551		25.09		24.33		0.348		<0.001		0.758		0.114
		72 h		41.22^ab		46.43^a		36.98^bc		32.04^cd		29.59^d		29.90^d		23.09^e		22.77^e		15.59^f		15.56^f		1.840		43.83^a		34.51^b		29.75^c		22.93^d		15.58^e		0.741		29.29		29.34		0.468		<0.001		0.990		0.003

体外消化48 h时,随盐地碱蓬比例的升高,干物质和有机物体外降解率逐渐升高,其中0∶100组干物质体外降解率显著高于100∶0组、75∶25组和50∶50组(P<0.05),0∶100组有机物体外降解率显著高于其他各组(P<0.05);粗蛋白质体外降解率呈先升高后降低的变化趋势,50∶50组和25∶75组粗蛋白质体外降解率显著高于其他各组(P<0.05);中性洗涤纤维体外降解率呈先降低后升高的变化趋势,酸性洗涤纤维体外降解率逐渐降低,其中50∶50组和25∶75组中性洗涤纤维体外降解率显著低于其他各组(P<0.05),0:100组酸性洗涤纤维体外降解率显著低于其他各组(P<0.05)。乳酸菌制剂对各营养物质体外降解率均无显著影响(P>0.05)。混合比例和乳酸菌制剂的交互作用对干物质和粗蛋白质体外降解率有显著影响(P<0.05)。

体外消化72 h时,100∶0组干物质体外降解率显著高于其他各组(P<0.05),0∶100组有机物体外降解率显著高于其他各组(P<0.05);粗蛋白质体外降解率呈先升高后降低的变化趋势,50∶50组和25∶75组粗蛋白质体外降解率显著高于其他各组(P<0.05);50∶50组、25∶75组和0∶100组中性洗涤纤维和酸性洗涤纤维体外降解率显著低于其他各组(P<0.05)。乳酸菌制剂对各营养物质体外降解率均无显著影响(P>0.05)。混合比例和乳酸菌制剂的交互作用对有机物、中性洗涤纤维和酸性洗涤纤维体外降解率有显著影响(P<0.05)。

3 讨论

3.1 乳酸菌制剂对不同比例玉米秸秆和盐地碱蓬混贮微生物含量的影响

本研究中各组均未出现霉菌,说明发酵过程控制良好,有效抑制了霉菌的生长。随盐地碱蓬比例的升高,混贮中酵母菌数量有所降低。研究表明,玉米秸秆上附着的酵母菌数量较多^[22],而盐地碱蓬上附着的酵母菌数量较少^[13],因此导致酵母菌数量减少的原因主要与玉米秸秆比例减少、盐地碱蓬比例增多有关。本研究还发现,混贮中乳酸菌数量随盐地碱蓬比例升高逐渐升高,以盐地碱蓬单一青贮组最高,但乳酸含量却呈先升高后降低的趋势,以盐地碱蓬单一青贮组最低。青贮是在密闭厌氧条件下,利用乳酸菌活动产生乳酸,抑制其他腐败微生物活动,达到饲料长期保存的目的^[23]。在短暂的好气性细菌活动阶段结束后,乳酸菌在厌氧条件下大量增殖,将原料自身的水溶性碳水化合物发酵生成乳酸,而盐地碱蓬能够提供较多的氮源,可能促进了乳酸菌的增殖和乳酸的生成^[24];而盐地碱蓬单一青贮组因缺乏水溶性碳水化合物,乳酸菌增殖后难以发酵产生乳酸,因此导致盐地碱蓬单一青贮组的乳酸菌数量与乳酸含量呈负相关。

3.2 乳酸菌制剂对不同比例玉米秸秆和盐地碱蓬混贮pH及有机酸含量的影响

青贮pH和有机酸含量是反映青贮品质的重要指标,通常优质的青贮pH应在4.4以下^[25]。本研究发现,除盐地碱蓬单独青贮组外,其他各组的混贮pH均在4.4以下,且随盐地碱蓬比例的提高,混贮pH逐渐升高。本研究证实,玉米秸秆的水溶性碳水化合物含量较高,而盐地碱蓬的水溶性碳水化合物含量较低,水溶性碳水化合物是乳酸菌发酵的重要底物^[26],因此,随着盐地碱蓬比例的升高,乳酸菌可用的发酵底物逐渐减少,造成pH逐渐升高。乳酸是由乳酸菌发酵产生,其含量通常与青贮品质呈正相关。本研究发现,盐地碱蓬比例由0升至75%时,混贮中乳酸含量升高。盐地碱蓬含有较高的粗蛋白质含量,适宜提高盐地碱蓬比例可能为乳酸菌提供了丰富的氮源,促进了乳酸的产生,而盐地碱蓬单独青贮组因缺乏水溶性碳水化合物导致乳酸含量降低。

挥发性脂肪酸方面,本研究发现,盐地碱蓬单独青贮组乙酸、丙酸和丁酸含量显著高于其他各组,其余组各之间无显著差异。乙酸通常由异型发酵乳酸菌产生,异型发酵速度慢、易造成养分损失;丙酸主要由丙酸菌产生,青贮pH较高时微生物菌群不稳定,易产生丙酸;丁酸主要由腐败菌和酪酸菌等产生,其含量与青贮品质呈负相关^[27-28]。因此,盐地碱蓬因缺乏发酵底物,导致单一青贮无法达到较高的青贮品质。本研究还发现,植物乳杆菌对青贮pH及有机酸含量均无显著影响,说明乳酸菌制剂可能对各组青贮发酵过程影响较小。

3.3 乳酸菌制剂对不同比例玉米秸秆和盐地碱蓬混贮营养成分的影响

青贮营养成分是影响青贮饲用品质的重要指标,随盐地碱蓬比例的升高,混贮的有机物、中性洗涤纤维和酸性洗涤纤维含量显著降低,而粗蛋白质和粗脂肪含量显著升高。营养成分分析表明,盐地碱蓬作为耐盐碱作物,盐分及粗灰分含量较高,粗纤维含量较低,粗蛋白质和粗脂肪含量较高^[11,28];而玉米秸秆的有机物、中性洗涤纤维和酸性洗涤纤维含量较高,粗蛋白质和粗脂肪含量较低;因此导致玉米秸秆和盐地碱蓬混贮营养成分变化的原因主要与二者营养成分差异有关。氨态氮是反映青贮中蛋白质降解程度的重要指标,主要由微生物分解利用蛋白质或氨基酸产生^[29]。本研究发现,盐地碱蓬单独青贮组氨态氮含量显著提高,比其余各组提高近3倍,说明盐地碱蓬单独青贮导致蛋白质降解,饲用品质下降。水溶性碳水化合物是乳酸菌发酵的重要底物^[26]。本研究发现,盐地碱蓬单独青贮组水溶性碳水化合物含量最低,这与其自身水溶性碳水化合物含量低有关,进一步说明盐地碱蓬不适于单独青贮发酵。研究还表明,植物乳杆菌对各组青贮营养成分未产生显著影响,说明植物乳杆菌不影响混贮过程中养分变化。

3.4 乳酸菌制剂对不同比例玉米秸秆和盐地碱蓬混贮营养物质体外降解率的影响

为进一步探讨玉米秸秆和盐地碱蓬混贮的饲用价值,进一步开展了青贮体外降解特性研究。结果表明,在体外消化24和48 h时,提高盐地碱蓬比例有利于提高混贮的干物质、有机物、粗蛋白质、中性洗涤纤维和酸性洗涤纤维体外降解率;但在体外消化72 h时,各组干物质和有机物体外降解率差异不大,粗蛋白质体外降解率随盐地碱蓬比例升高呈先升高后降低趋势,但中性洗涤纤维和酸性洗涤纤维降解率呈逐渐下降趋势。推测提高盐地碱蓬比例一定程度上改善了混贮的饲用品质,提高了消化特性,且盐地碱蓬的蛋白质具有较高的可消化性;但盐地碱蓬自身纤维可能较难消化,造成中性洗涤纤维和酸性洗涤纤维体外降解率降低。目前,关于盐地碱蓬可消化特性的研究还较少,需进一步开展系统研究以促进盐地碱蓬在畜禽生产中的应用。本研究还表明,乳酸菌制剂对各组混贮的营养物质体外降解率无显著影响,但数值上以植物乳杆菌组总体偏高,这可能与乳酸菌不能有效地利用青贮中的木质素、纤维素和半纤维素,在改善青贮消化特性方面的作用有限有关^[30]。但混合比例和乳酸菌制剂的交互作用对各组多个时间点的营养物质体外降解率有显著影响,提示植物乳杆菌在一定程度上可能改善青贮的可消化性。

4 结论

① 将玉米秸秆和盐地碱蓬混贮可以改善青贮品质,提高可消化特性及饲用价值。

② 乳酸菌制剂对玉米秸秆和盐地碱蓬混贮发酵品质及各项指标的影响较小。

③ 综合各项指标,推荐玉米秸秆和盐地碱蓬混贮的混合比例为75∶25和50∶50。

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DOI

TAO

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