秸秆“破壁+菌酶”联合处理饲料化利用技术及其在反刍动物中的应用

doi:10.16431/j.cnki.1671-7236.2025.07.008

Abstract

Abstract: China has abundant crop straw resources,and if it can be converted into ruminant feed to make full use of it,not only reduce the problems of resource wastage and environmental pollution,but also effectively alleviate the predicament caused by the shortage of roughage resources in China,and decrease the cost of breeding.However,straw’s high cellulose content and complex structural characteristics have become barriers to its utilization in animal production.Currently,there are various treatment methods (including physical,chemical and biological) that can improve the feeding value of crop straw,but the actual feed utilization is still restricted by many factors.This review focuses on the national major agricultural leading technology—Feed utilization technology of straw with "wall breaking and bacteria-enzyme" synergism treatment.This technology combines wall-breaking technology with bacteria and enzyme co-fermentation technology,which opens up a new way for the efficient feed utilization of crop straw.This review describes the principle,process and characteristics of feed utilization technology of straw with "wall breaking and bacteria-enzyme" synergism treatment,and its application in ruminant production,and clarifies the challenges and future development direction of the efficient use of straw resources,aiming to provide technical guidance for the feed utilization of crop straw resources and promote the sustainable development of the animal husbandry industry.

Key words: expansion; bacteria-enzyme synergism; crop straw; feed utilization

CLC Number:

S816.5

LIANG Jianyong, LIU Yang, LI Jiuyue, GAO Yuan, ZHAO Xiaojuan, JIAO Linmiao, QI Ligeer, XUE Shuyuan. Feed Utilization Technology of Straw with "Wall Breaking and Bacteria-Enzyme" Synergism Treatment and Its Application in Ruminants[J]. China Animal Husbandry & Veterinary Medicine, 2025, 52(7): 3059-3069.

References

[1] 刘俊杰,严晓斌,张美怡,等.中国农作物秸秆资源产量分布及利用分析[J].农业资源与环境学报,2024.Doi:10.13254/j.jare.2024.0184. LIU J J,YAN X B,ZHANG M Y,et al.Analysis of yield distribution and utilization of crop straw resources in China[J].Journal of Agricultural Resources and Environment,2024.Doi:10.13254/j.jare.2024.0184.(in Chinese)
[2] 曹国良,张小曳,王亚强,等.中国区域农田秸秆露天焚烧排放量的估算[J].科学通报,2007,52(15):104-109. CAO G L,ZHANG X Y,WANG Y Q,et al.Experimental investigation on emission factors of particulate matter and gaseous pollutants from crop residues burning[J].Chinese Science Bulletin,2007,52(15):104-109.(in Chinese)
[3] 曹国良,张小曳,王丹,等.秸秆露天焚烧排放的TSP等污染物清单[J].农业环境科学学报,2005,24(4):800-804. CAO G L,ZHANG X Y,WANG D,et al.Inventory of emissions of pollutants from open burning crop residue[J].Journal of Agricultural and Environmental Science,2005,24(4):800-804.(in Chinese)
[4] 中共中央国务院关于做好二○二三年全面推进乡村振兴重点工作的意见[N].人民日报,2023-02-14(1). Opinions of the Central Committee of the Communist Party of China and the State Council on doing a good job in the key work of comprehensively promoting rural revitalization in 2023[N].People’s Daily,2023-02-14(1).(in Chinese)
[5] 刘睿,万楚筠,黄茜,等.秸秆预处理技术存在的问题与发展前景[J].环境科学与技术,2009,32(5):88-91. LIU R，WAN C Y,HUANG Q,et al.Problem and prospect of pretreatment of straw[J].Environmental Science & Technology,2009,32(5):88-91.(in Chinese)
[6] 钟丽媛,孙会增,吴冠中,等.农作物秸秆饲料化利用的制约因素及其解决对策[J].中国畜牧杂志,2023,59(12):61-66. ZHONG L Y,SUN H Z,WU G Z,et al.Restrictive factors and countermeasures for use of cereal byproducts as feeds[J].Chinese Journal of Animal Science,2023,59(12):61-66.(in Chinese)
[7] CAO X H,ZUO S,LIN Y L,et al.Expansion improved the physical and chemical properties and in vitro rumen digestibility of buckwheat straw[J].Animals (Basel),2024,14(1)：29.
[8] DUQUE A,MANZANZARES P,BALLESTEROS M.Extrusion as a pretreatment for lignocellulosic biomass:Fundamentals and applications[J].Renewable Energy,2017,114:1427-1441.
[9] 王晓飞,高源,田丰,等.膨化秸秆微生物发酵饲料对杜寒杂交肉羊生长性能和胃肠道发育的影响[J].畜牧与饲料科学,2022,43(2):28-34. WANG X F，GAO Y，TIAN F,et al.Effects of microbial fermented expanded straw feed on growth performance and gastrointestinal tract development of Dorper and Thin-tailed Han crossbred sheep[J].Animal Husbandry and Feed Science,2022,43(2):28-34.(in Chinese)
[10] 陈洪章,陈继贞,刘健,等.麦草蒸汽爆碎处理的研究——Ⅰ.影响麦草蒸汽爆碎处理因素及其过程分析[J].纤维素科学与技术,1999,7(2):60-67. CHEN H Z,CHEN J Z,LIU J,et al.Study on steam explosion of wheat straw—Ⅰ.Effects of operating conditions for steam explosion of wheat straw and analysis of the process[J].Journal of Cellulose Science and Technology,1999,7(2):60-67.(in Chinese)
[11] 刘强林,赵永锋,孟庆翔.秸秆汽爆技术及其在反刍动物饲养中的应用[J].中国畜牧杂志,2015,51(S1):71-74. LIU Q L,ZHAO Y F,MENG Q X.Steam explosion of crop residues and their application in the feeding of ruminant animals[J].Chinese Journal of Animal Science,2015,51(S1):71-74.(in Chinese)
[12] 谭佳.不同氨基酸对“半胱氨酸-木糖”体系肉香气形成影响及机制研究[D].北京:北京工商大学,2021. TAN J.Influences of different amino acids on the formation of meat aroma in the "cysteine-xylose" reaction system and influencing mechanism[D].Beijing:Beijing Technology and Business University,2021.(in Chinese)
[13] 陈尚钘,勇强,徐勇,等.蒸汽爆破预处理对玉米秸秆化学组成及纤维结构特性的影响[J].林产化学与工业,2009,29(S1):33-38. CHEN S X,YONG Q,XU Y,et al.Effect of steam-explosion pretreatment on chemical components and cellulosic structure of corn stalk[J].Chemistry and Industry of Forest Products,2009,29(S1):33-38.(in Chinese)
[14] 韩浩然,常娟,尹清强,等.蒸汽爆破和化学处理对玉米秸秆化学成分的影响[J].江苏农业科学,2017,45(8):166-168. HAN H R,CHANG J,YIN Q Q,et al.Effect of steam explosion and chemical treatment on the chemical composition of corn stover[J]. Jiangsu Agricultural Sciences,2017,45(8):166-168.(in Chinese)
[15] GARCIA-APARICIO M P,BALLESTEROS I,GONZALEZ A,et al.Effect of inhibitors released during steam-explosion pretreatment of barley straw on enzymatic hydrolysis[J].Applied Biochemistry and Biotechnology,2006,22:278-288.
[16] 李国栋,赵圣国,张养东,等.秸秆饲料化预处理方式及其发酵抑制化合物的作用机理[J].动物营养学报,2016,28(10):3051-3058. LI G D,ZHAO S G,ZHANG Y D,et al.Straws as feed:Pretreatment methods and action mechanism of fermentation inhibitors[J].Chinese Journal of Animal Nutrition,2016,28(10):3051-3058.(in Chinese)
[17] CASTRO F B,HOTTEN P M,RSKOV E R,et al..Inhibition of rumen microbes by compounds formed in the steam treatment of wheat straw[J].Bioresource Technology,1994,50(1):25-30.
[18] VIOLA E,ZIMBARDI F,CARDINALE M,et al.Processing cereal straws by steam explosion in a pilot plant to enhance digestibility in ruminants[J].Bioresource Technology,2008,99(4):681-689.
[19] HENDRIKS A,ZEEMAN G.Pretreatments to enhance the digestibility of lignocellulosic biomass[J]. Bioresource Technology,2009,100(1):10-18.
[20] LIU J X,ORSKOV E R,CHEN X B.Optimization of steam treatment as a method for upgrading rice straw as feeds[J].Animal Feed Science & Technology,1999,76(3):345-357.
[21] KARUNANITHY C,MUTHUKUMARAPPAN K.Effect of extruder parameters and moisture content of switchgrass,prairie cord grass on sugar recovery from enzymatic hydrolysis[J].Applied Biochemistry and Biotechnology,2010,162(6):1785-1803.
[22] DUQUE A,MANZANARES P,BALLESTEROS M.Study of process configuration and catalyst concentration in integrated alkaline extrusion of barley straw for bioethanol production[J].Fuel,2014,134:448-454.
[23] 刘畅,孟倩楠,刘晓飞,等.挤压膨化技术及其应用研究进展[J].饲料研究,2021,44(4):137-140. LIU C,MENG Q N,LIU X F,et al.Advances in the application of extrusion technology in feed industry[J].Feed Research,2021,44(4):137-140.(in Chinese)
[24] 王宏立,杨天维,张祖立.秸秆挤压膨化技术[J].农产品加工,2003,6:27-34. WANG H L,YANG T W,ZHANG Z L.Straw extrusion technology[J].Farm Products Processing,2003,6:27-34.(in Chinese)
[25] 王鑫.挤压膨化对玉米秸秆特性及施用效果影响研究[D].长春:吉林农业大学,2019. WANG X.Study on effect of extrusion on characteristics and application effect of corn straw[D].Changchun:Jilin Agricultural University,2019.(in Chinese)
[26] 王玉婷,于维,祁宏伟.挤压膨化微贮玉米秸秆的瘤胃降解特性[J].中国畜牧杂志,2018,54(11):75-78. WANG Y T,YU W,QI H W.Ruminal degradation characteristics of extrusion and ensilage pretreated corn stover[J].Chinese Journal of Animal Science,2018,54(11):75-78.(in Chinese)
[27] 王宏立,张祖立.挤压膨化技术在秸秆饲料加工中的应用[J].农机化研究,2007,9:173-174. WANG H L,ZHANG Z L.Application of extrusion technology on straw and feed processing[J].Agricultural Mechanization Research,2007,9:173-174.(in Chinese)
[28] 严宇.面向畜牧养殖农作物秸秆双螺杆挤压膨化试验研究[D].扬州:扬州大学,2018. YAN Y.Research on experimental double-screw extruded expansion of crop residues for animal husbandry production[D].Yangzhou:Yangzhou University,2018.(in Chinese)
[29] 葛迅一.基于双螺杆挤压膨化技术的含秸秆浮性水产饲料制备研究[D].扬州:扬州大学,2019. GE X Y.Study on the preparation of floating aquafeed containing straw based on double-screw extrusion expansion technology[D].Yangzhou:Yangzhou University,2019.(in Chinese)
[30] 张静.秸秆饲料双螺杆挤压膨化技术研发现状及发展趋势[J].农业科技与装备,2020,4:49-50. ZHANG J.Research and development status and development trend of double screw extrusion technology for straw feed[J]. Agricultural Science & Technology and Equipment,2020,4:49-50.(in Chinese)
[31] KARUNANITHY C,MUTHUKUMARAPPAN K.Thermo-mechanical Pretreatment of Feedstocks[M].Dordrecht:Springer Netherlands.2013.
[32] 赵凤芹,申德超.挤压膨化参数对玉米秸秆纤维成分含量的影响[J].农业机械学报,2010,41(10):112-116. ZHAO F Q,SHEN D C.Influence of extrusion system parameters on fiber content of maize straw[J].Transactions of the Chinese Society for Agricultural Machinery,2010,41(10):112-116.(in Chinese)
[33] 赵凤芹,申德超,刘远洋,等.挤压膨化对玉米秸秆中粗纤维含量的影响[J].东北农业大学学报,2008,39(3):105-109. ZHAO F Q,SHEN D C,LIU Y Y,et al.The experimental study on the influence regularity of extruding-expanding on crude fibre content of corn straw[J].Journal of Northeast Agricultural University,2008,39(3):105-109.(in Chinese)
[34] 张祖立,刘晓峰,李永强,等.农作物秸秆膨化技术及膨化机理分析[J].沈阳农业大学学报,2001,32(2):128-130. ZHANG Z L,LIU X F,LI Y Q,et al.Techniques and mechanisms of extruding process of crop straw[J].Journal of Shenyang Agricultural University,2001,32(2):128-130.(in Chinese)
[35] 丁健,武忠,武小平,等.不同处理方式对玉米秸秆营养价值的影响研究[J].中国饲料,2018,6:21-25. DING J,WU Z,WU X P,et al.Study on the effect of different treatments on nutritive value of corn stalk[J].China Feed,2018,6:21-25.(in Chinese)
[36] 张祖立,朱永文,刘晓峰,等.螺杆挤压膨化机加工农作物秸杆的试验研究[J].农业工程学报,2001,17(6):97-101. ZHANG Z L,ZHU Y W,LIU X F,et al.Experimental study on extruding crop straw by screw extruder[J].Transactions of the Chinese Society of Agricultural Engineering,2001,17(6):97-101.(in Chinese)
[37] LIU C,VANDERHEIDE E,WANG H,et al.Alkaline twin-screw extrusion pretreatment for fermentable sugar production[J].Biotechnology for Biofuels,2013,6(1):97.
[38] 萨如拉,徐均钊,包呼格吉乐图,等.菌酶协同对肉牛膨化玉米秸秆型发酵全混合日粮品质的影响[J].吉林农业大学学报,2023,45(4):461-466. SA R L,XU J Z,BAO H G J L T,et al.Effect of bacteria-enzyme synergism on quality of beef cattle puffed corn stalk fermented total mixed ration[J].Journal of Jilin Agricultural University,2023,45(4):461-466.(in Chinese)
[39] CHANG J,CHENG W,YIN Q,et al.Effect of steam explosion and microbial fermentation on cellulose and lignin degradation of corn stover[J].Bioresource Technology,2012,104:587-592.
[40] 王玉婷.膨化微贮玉米秸秆营养价值的评定及其对肉牛生产性能的影响[D].长春:吉林农业大学,2019. WANG Y T.Evaluation the nutritional value of expanded microbial corn stover silage and its effect on beef cattle performance[D].Changchun:Jilin Agricultural University,2019.(in Chinese)
[41] 黄开明,赵立欣,冯晶,等.复合微生物预处理玉米秸秆提高其厌氧消化产甲烷性能[J].农业工程学报,2018,34(16):184-189. HUANG K M,ZHAO L X,FENG J,et al.Pretreatment of corn stalk by composite microbial strain improving its methane production performance by anaerobic digestion[J].Transactions of the Chinese Society of Agricultural Engineering,2018,34(16):184-189.(in Chinese)
[42] 王红梅.复合酶处理玉米秸秆对肉羊生产性能及破解纤维结构机制的研究[D].北京：中国农业科学院,2017. WANG H M.Effect of enzyme preparation in corn straw-based diet on growth performance of lambs and mechanism of its action on degradation of fiber structure[D].Beijing:Chinese Academy of Agricultural Sciences,2017.(in Chinese)
[43] 韩浩然.玉米秸秆的理化处理及其在湖羊生产中的应用[D].郑州:河南农业大学,2017. HAN H R.The physichemical treatment of corn straw and its application in Hu sheep production[D].Zhengzhou:Henan Agricultural University,2017.(in Chinese)
[44] 冉福,焦婷,雷赵民,等.不同汽爆处理下玉米秸秆品质综合评价[J].草地学报,2020,28(3):835-843. RAN F,JIAO T,LEI Z M,et al.Comprehensive evaluation on corn stalk nutrient quality under different steam explosion treatments[J].Journal of Grassland Science,2020,28(3):835-843.(in Chinese)
[45] NIE D C,YAO L Y,XU X K,et al.Promoting corn stover degradation via sequential processing of steam explosion and cellulase/lactic acid bacteria-assisted ensilage[J].Bioresource Technology,2021,337:125392.
[46] 高雪梅,焦婷,雷赵民,等.不同添加剂发酵处理对汽爆玉米秸秆发酵品质及微生物数量的影响[J].草业科学,2021,38(1):192-201. GAO X M,JIAO T,LEI Z M,et al.Effects of different additives on fermentation quality and microbial population of steam-exploded corn straw[J].Pratacultural Science,2021,38(1):192-201.(in Chinese)
[47] WANG K,NAN X,TONG J,et al.Steam explosion pretreatment changes ruminal fermentation in vitro of corn stover by shifting archaeal and bacterial community structure[J].Frontiers in Microbiology,2020,11:2027.
[48] 李德勇,和立文,张民哲,等.体外产气法评价汽爆处理对秸秆营养价值的影响[J].中国畜牧杂志,2015,51(S1):62-65. LI D Y,HE L W,ZHANG M Z,et al.Effect of steam explosion treatment on the nutritional value of straw evaluated through gas production methods in vitro[J].Chinese Journal of Animal Science,2015,51(S1):62-65.(in Chinese)
[49] 孙美杰,徐诣轩,曹玉荣,等.不同尿素添加剂量对蒸汽爆破玉米秸秆体外瘤胃发酵和功能微生物数量的影响[J].动物营养学报,2021,33(7):3959-3969. SUN M J,XU Y X,CAO Y R,et al.Effects of different urea addition levels on in vitro rumen fermentation and functional microbial populations of steam-exploded corn stover[J].Chinese Journal of Animal Nutrition,2021,33(7):3959-3969.(in Chinese)
[50] NAEEM M.蒸汽处理稻草体外消化率的评定及其对山羊的消化能力、生长性能和肉品质的影响[D].南京:南京农业大学,2014. NAEEM M.Evaluation of degradability of the steam treated rice straw in vitro and its effects on digestibility,growth and meat quality of goats[D].Nanjing:Nanjing Agricultural University,2014.(in Chinese)
[51] GAMBACORTA E,ZIMBARDI F,PALAZZO M,et al.'Steam explosion’ treated straw in mixed feeds for ewes:Effect on milk production[J].Italian Journal of Animal Science,2011,2(S1):566-568.
[52] ZHAO S,LI G,ZHENG N,et al.Steam explosion enhances digestibility and fermentation of corn stover by facilitating ruminal microbial colonization[J].Bioresource Technology,2018,253:244-251.
[53] 郭同军,张志军,赵洁,等.蒸汽爆破发酵棉秆饲喂绵羊效果分析[J].农业工程学报,2018,34(7):288-293. GUO T J,ZHANG Z J,ZHAO J,et al.Analysis on feeding effects of steam explosion and fermentation cotton stalk in sheep[J].Transactions of the Chinese Society of Agricultural Engineering,2018,34(7)288-293.(in Chinese)
[54] 崔树和.膨化玉米秸秆发酵饲料对延边黄牛生产性能的影响研究[D].吉林:延边大学,2016. CUI S H.Effects of puffed corn straw fermentation feed on the production performance of Yanbian Yellow cattle[D].Jilin:Yanbian University,2016.(in Chinese)
[55] 王琦.不同高值化玉米秸秆类型TMR对肉牛瘤胃发酵、菌群和生产性能的影响[D].通辽:内蒙古民族大学，2022. WANG Q.Effects of different high-value corn stover types TMR on rumen fermentation,microbiota and production performance of beef cattle[D].Tongliao:Inner Mongolia Minzu University,2022.(in Chinese)
[56] 侯沛君.膨化艾草秸秆对湖羊生长性能、消化代谢及瘤胃微生物区系的影响[D].郑州:河南农业大学,2021. HOU P J.Effects of extruded Artemisia argyi straw on growth performance,digestion and rumen microflora of Hu sheep[D].Zhengzhou:Henan Agricultural University,2021.(in Chinese)
[57] 王廷艳,白国明,侯留飞,等.菌酶协同发酵对青稞秸秆营养品质的影响[J].饲料研究,2024,47(19):117-123. WANG T Y,BAI G M,HOU L F,et al.Effect of bacterial enzyme co-fermentation on nutritional quality of highland barley straw[J].Feed Research,2024,47(19):117-123.(in Chinese)
[58] 张彩霞,付文华,李俊良,等.菌酶协同秸秆生物发酵饲料营养价值及瘤胃降解率研究[J].动物营养学报,2024,36(9):6038-6048. ZHANG C X,FU W H,LI J L,et al.A study of nutritional value and rumen degradation rate of fermented stover feed by fungus and enzyme[J].Chinese Journal of Animal Nutrition,2024,36(9):6038-6048.(in Chinese)
[59] 薛树媛,李九月,田丰,等.膨化秸秆微生物发酵饲料对杜寒杂交肉羊瘤胃微生物区系的影响[J].中国饲料,2021,19:115-123. XUE S Y,LI J Y,TIAN F,et al.Effects of extruded straw microbial fermented feed on rumen microflora of Dorper-Han crossbred sheep[J]. China Feed,2021,19:115-123.(in Chinese)
[60] 王晓飞,乌日勒格,田丰,等.膨化秸秆微生物发酵饲料对杜寒杂交肉羊瘤胃发酵的影响[J].畜牧与饲料科学,2021,42(2):32-36. WANG X F,WU R L G,TIAN F,et al.Effect of extruded straw microbial fermented feed on ruminal fermentation of Dorper×Thin-tailed Han crossbred sheep[J].Animal Husbandry and Feed Science,2021,42(2):32-36.(in Chinese)

Feed Utilization Technology of Straw with "Wall Breaking and Bacteria-Enzyme" Synergism Treatment and Its Application in Ruminants

PDF (PC)

Knowledge

Abstract

Cite this article

share this article

References

Related Articles 8

Recommended Articles

Metrics

Comments

[1]	LI Zhongbo, CHENG Tianyin. Haplotype Diversity,Genetic Differentiation and Population Expansion of Haemaphysalis longicornis Isolated from Different Districts [J]. China Animal Husbandry & Veterinary Medicine, 2024, 51(12): 5405-5415.
[2]	TIAN Yangqing, WANG Yayuan, ANG Yanfen, YAN Han, LIU Xin, YAN Yulin. Research Progress on Therapeutic Mechanism and Application of Canine Hematopoietic Stem Cell Transplantation [J]. China Animal Husbandry & Veterinary Medicine, 2022, 49(2): 791-799.
[3]	PU Lei, LIU Xin, YUE Jing-wei, ZHANG Jin-shan, WANG Li-gang, YAN Hua, HOU Xin-hua, GAO Hong-mei, ZHANG Tian, ZHANG Yue-bo, WU Qun-qing, ZHANG Long-chao, WANG Li-xian. Study on HMGA1 Gene Polymorphism Site and Its Association with Feed Efficiency Related Traits in Duroc Pigs [J]. China Animal Husbandry & Veterinary Medicine, 2016, 43(12): 3268-3274.
[4]	PU Lei, YUE Jing-wei, ZHANG Jin-shan, LIU Xin, WANG Li-gang, YAN Hua, HOU Xin-hua, GAO Hong-mei, ZHANG Tian, ZHANG Yue-bo, WU Qun-qing, ZHANG Long-chao, WANG Li-xian. Association Analysis on MAP3K5 Gene Polymorphism Site with Growth and Feed Efficiency Related Traits in Duroc Pigs [J]. China Animal Husbandry & Veterinary Medicine, 2016, 43(11): 2982-2988.
[5]	LI Rui-lan, OUYANG Xiao-qing, ZHANG Chun-qiang, ZHANG Tong, FAN Xiao-mei, ZHANG Jia-xin. Construction of Eukaryotic Expression Vector of GDF-9 Gene and its Effect on the Expression of Expansion-related Genes in Bovine Cumulus Cells [J]. China Animal Husbandry & Veterinary Medicine, 2015, 42(6): 1325-1332.
[6]	JIAO Ming-xia, LIU Zhong-feng, WANG Feng, LIU Shi-chao, Gerelchimeg, ZHOU Yang, KONG Qing-ran, YIN Zhi, GUO Shi-meng, LIU Zhong-hua. Preliminary Study on the Mechnism Account for the Difference of Cytoplasmic Maturation and in vitro Developmental Potential of Porcine Oocytes from Different Diameter Follicles [J]. China Animal Husbandry & Veterinary Medicine, 2014, 41(10): 165-171.
[7]	CHEN Lin;ZHANG Jun-feng;LIU Jian-hua;CHEN Zhang-liu;ZENG Zhen-ling. Transfer Mode of 16S rRNA Methylase rmtB in EnterobacteriaIsolates from Pig Farms [J]. China Animal Husbandry & Veterinary Medicine, 2010, 37(3): 55-59.
[8]	KUANG Shengyao;TANG Ling;ZHANG Chun;ZENG Lihua. Research and Application of Compound Enzymes in Swine and Poultry Breeding [J]. China Animal Husbandry & Veterinary Medicine, 2007, 34(9): 21-23.