含無患子皂甙的精料對(duì)后備牛生產(chǎn)性能和瘤胃發(fā)酵的影響

含無患子皂甙的精料對(duì)后備牛生產(chǎn)性能和瘤胃發(fā)酵的影響

焦陽, 黃文明, 郭海明, 葉均安*

(浙江大學(xué)動(dòng)物科學(xué)學(xué)院奶業(yè)科學(xué)研究所,杭州310058)

摘要為探討無患子皂甙對(duì)25～28月齡中國(guó)荷斯坦后備奶牛生產(chǎn)性能、營(yíng)養(yǎng)物質(zhì)消化率、瘤胃發(fā)酵和血液生化指標(biāo)的影響,試驗(yàn)選用16頭平均月齡為(25.75±0.94)、產(chǎn)前為(144.94±22.98) d的健康中國(guó)荷斯坦后備奶牛,采用配對(duì)設(shè)計(jì)分為2組,每組8頭。對(duì)照組和試驗(yàn)組分別飼喂質(zhì)量分?jǐn)?shù)為0和0.15%無患子皂甙的精料。試驗(yàn)期95 d,其中預(yù)飼期7 d,正式期88 d,試驗(yàn)?zāi)┢诓杉S樣、血樣和瘤胃液樣品。結(jié)果表明：與對(duì)照組相比,試驗(yàn)組后備牛的體高、體斜長(zhǎng)、胸圍和估測(cè)體質(zhì)量有一定提高(P>0.05),平均日增質(zhì)量提高了31%(P=0.05),飼料質(zhì)量比顯著下降(P<0.05);干物質(zhì)(P<0.01)、有機(jī)物(P<0.01)、粗蛋白(P<0.01)、中性洗滌纖維(P<0.05)、酸性洗滌纖維(P<0.01)和粗灰分(P<0.01)消化率均升高;原蟲密度、氨態(tài)氮質(zhì)量濃度、總揮發(fā)性脂肪酸及乙酸和丙酸都沒有發(fā)生顯著變化(P>0.05),乙酸丙酸濃度之比和估測(cè)甲烷產(chǎn)量降低(P<0.05);各個(gè)血液生化指標(biāo)也沒有顯著變化。表明飼喂含無患子皂甙的精料對(duì)25～28月齡后備牛生產(chǎn)性能有提高的趨勢(shì),并在一定程度上改善了瘤胃發(fā)酵模式。

關(guān)鍵詞無患子皂甙; 后備牛; 瘤胃調(diào)控; 生產(chǎn)性能

中圖分類號(hào)S 816.79文獻(xiàn)標(biāo)志碼A

基金項(xiàng)目:浙江省農(nóng)業(yè)(畜禽)新品種選育重大科技專項(xiàng)項(xiàng)目(2012C12906-14)。

收稿日期(Received):2014-06-30;接受日期(Accepted):2014-10-28;網(wǎng)絡(luò)出版日期(Published online):2015-05-19

Effects of Sapindoside-containing concentrate on productive performance and rumen fermentation in heifers. Journal of ZhejiangUniversity(Agric. & LifeSci.), 2015,41(3)：358-364

Jiao Yang, Huang Wenming, Guo Haiming, Ye Jun’an*(InstituteofDairyScience,CollegeofAnimalSciences,ZhejiangUniversity,Hangzhou310058,China)

SummarySapindoside is a type of triterpenoid saponins and is extracted fromSapindusmukorossipericarp by anhydrous ethanol. Previous studies reported that Sapindoside can regulate rumen fermentationinvitro, but whether it is effectiveinvivois still unknown. Thus, the objective of the study is to investigate the effects of Sapindoside-containing concentrate on productive performance, nutrient digestion, rumen fermentation and plasma biochemical indexes in 25-28 month-old heifers.

Sixteen Chinese Holstein heifers, 144 days left to give birth, were used in a 95 d trial (7 d for adaptation). The animals were assigned to two treatments: basal diet with or without 0.15% Sapindoside (powder of 80% triterpenoid saponins) in concentrate. The adding level was based on our previous experimentinvitro. At the last week of the trial, a total of 12 heifers, six from each treatment, were randomly selected, and subjected to a digestion trial by index method with acid insoluble ash as index. The samples of blood and rumen fluids were collected on the day before the last day of the trial. Body size indexes were measured every month and body mass was calculated by formula.

Results showed that body height, body length, heart girth and estimated body mass had an increase trend (P>0.05) in Sapindoside-containing group, and the estimated average daily gain of the whole period was increased by 31% compared with the control (P=0.05). Apparent total tract digestibility of dry matter (DM,P<0.01), organic matter (OM,P<0.01), crude protein (CP,P<0.01), ether extract (EE,P>0.05), neutral detergent fiber (NDF,P<0.05), acid detergent fiber (ADF,P<0.01) and crude ash (P<0.01)were greater in Sapindoside-containing group compared with the control. Protozoa counts, concentration of ammonia-nitrogen, total volatile fatty acids as well as acetate and propionate were not affected by Sapindoside-containing concentrate (P>0.05). However, butyrate concentration, acetate to propionate ratio and estimated methane production decreased in Sapindoside-containing group (P<0.05). Moreover, no difference was found in blood biochemical indexes, including total protein, albumin, globulin, urea nitrogen, glucose, total cholesterol, triglyceride, non-esterified fatty acid,β-hydroxybutyrate, total bilirubin, creatinine, glutamic-pyruvic transaminase, glutamic-oxalacetic transaminase, alkaline phosphatase and superoxide dismutase between two groups (P>0.05).

In summary, feeding Sapindoside-containing concentrate presents a trend to improve the productive performance of 25-28 month-old heifers. Meanwhile, further studies are required to explore the Sapindoside’s adding level and the long-term effects of Sapindoside on heifers.

Key wordsSapindoside; heifer; rumen regulation; productive performance

隨著動(dòng)物生產(chǎn)的集約化程度越來越高,很多養(yǎng)殖企業(yè)都使用抗生素來提高動(dòng)物的抗病性和生產(chǎn)性能,但使用抗生素造成的殘留和動(dòng)物的耐藥性問題一直沒有辦法解決,所以很多發(fā)達(dá)國(guó)家已經(jīng)禁止使用抗生素。未來,中國(guó)禁止使用抗生素也是一種必然的趨勢(shì)。因此,尋找新的添加劑來替代抗生素是目前比較迫切的需要,其中,皂甙作為一種植物提取物,具有能夠驅(qū)除原蟲、促生長(zhǎng)、降低飼料蛋白質(zhì)損失和提高機(jī)體免疫力等功能[1]。本研究室先前的體外試驗(yàn)也表明無患子皂甙有調(diào)控瘤胃發(fā)酵、減少甲烷排放等功能[2],因此本試驗(yàn)以一種含無患子皂甙的精料為原料,研究其對(duì)25～28月齡后備牛生產(chǎn)性能和瘤胃發(fā)酵等指標(biāo)的影響,為無患子皂甙在生產(chǎn)中的應(yīng)用提供參考。

1材料與方法

1.1試驗(yàn)設(shè)計(jì)

試驗(yàn)選取16頭平均月齡25.75±0.94、估測(cè)平均體質(zhì)量(515.13±42.38) kg、產(chǎn)前(144.94±22.98) d的健康中國(guó)荷斯坦后備奶牛,采用配對(duì)試驗(yàn)設(shè)計(jì),按照體質(zhì)量、月齡和預(yù)產(chǎn)期相近的原則分為對(duì)照組和試驗(yàn)組。

1.2試驗(yàn)日糧

試驗(yàn)日糧由羊草、青貯玉米秸和精料構(gòu)成,精粗比40∶60(干物質(zhì)基礎(chǔ))。對(duì)照組精料使用牛場(chǎng)原飼料配方;試驗(yàn)組精料由浙江科盛飼料股份有限公司加工,營(yíng)養(yǎng)水平與對(duì)照組精料基本一致,但額外添加了0.15%自制無患子皂甙(含皂甙量80%)、1.5%小蘇打、0.6%氧化鎂。與牧場(chǎng)原有飼喂模式保持一致,精粗分飼并保證每組各喂4 kg精料(折算后無患子皂甙的添加量為4.8 g/d),調(diào)整粗飼料飼喂量,使2組試驗(yàn)牛的各個(gè)營(yíng)養(yǎng)成分?jǐn)z入量基本一致。試驗(yàn)日糧營(yíng)養(yǎng)水平和攝入量分別見表1和表2。

表1　試驗(yàn)日糧

DM:干物質(zhì);CP:粗蛋白;EE:粗脂肪;NDF:中性洗滌纖維;ADF:酸性洗滌纖維.a)總能為實(shí)測(cè)值。

DM: Dry matter; CP: Crude protein; EE: Ether extract; NDF: Neutral detergent fiber; ADF: Acid detergent fiber. a) Gross energy was measured.

表2　營(yíng)養(yǎng)物質(zhì)攝入量

DM:干物質(zhì);CP:粗蛋白;EE:粗脂肪;NDF:中性洗滌纖維;ADF:酸性洗滌纖維.a)日糧構(gòu)成：羊草5.96 kg,精料4 kg,青貯玉米秸2.15 kg;b)日糧構(gòu)成：羊草5.68 kg,精料4 kg,青貯玉米秸2.20 kg;c)總能為實(shí)測(cè)值。

DM: Dry matter; CP: Crude protein; EE: Ether extract; NDF: Neutral detergent fiber; ADF: Acid detergent fiber. a) Formulation of diets: Chinese wild rye grass 5.96 kg, concentrate 4 kg, corn stover silage 2.15 kg; b) Formulation of diets: Chinese wild rye grass 5.68 kg, concentrate 4 kg, corn stover silage 2.20 kg; c) Gross energy was measured.

1.3飼養(yǎng)管理

試驗(yàn)牛均為拴系式飼養(yǎng),采用牧場(chǎng)原有飼喂模式,日飼喂3次(08:00、15:00和22:00),精粗分開飼喂,飼喂順序?yàn)榍噘A玉米秸、精料、羊草。試驗(yàn)周期95 d,其中預(yù)飼期7 d,正式期88 d。

1.4測(cè)定項(xiàng)目

預(yù)飼第1天、正式期第25、55和89天,在清晨飼喂后3 h分別測(cè)定各頭牛的胸圍、體斜長(zhǎng)與體高,體質(zhì)量根據(jù)公式[3]估測(cè)[體質(zhì)量/kg=(胸圍/m)2×體斜長(zhǎng)/m×90.0];正式期第23天和第84天采集飼料樣品并測(cè)定采食量(連續(xù)測(cè)定2 d后取平均值)。

試驗(yàn)結(jié)束前1周每組隨機(jī)選取6頭后備牛,采集糞樣、瘤胃液和血液。采用酸不溶灰分法測(cè)定營(yíng)養(yǎng)物質(zhì)消化率,連續(xù)3 d直腸采糞,每次采集100 g裝于塑封袋內(nèi),-20 ℃保存;正式期第88天清晨飼喂后3 h口腔采集瘤胃液50 mL,用Sartorius PB-20型pH計(jì)立即測(cè)定樣品pH值,取瘤胃液1 mL加入1 mL原蟲染色液(甲基綠0.5 g、NaCl 8.5 g溶于1 000 mL甲醛溶液)中,-4 ℃保存(1周內(nèi)鏡檢原蟲),剩余樣品-20 ℃保存。同時(shí)使用肝素管進(jìn)行頸靜脈采血,每頭牛采集5 mL,然后3 000g,離心15 min制備血漿,并于-20 ℃保存。

1.5樣品分析

飼料樣和糞樣烘干后過40目篩粉碎,用于測(cè)定干物質(zhì)、粗蛋白、粗脂肪、中性洗滌纖維、酸性洗滌纖維和粗灰分等常規(guī)指標(biāo)。瘤胃參數(shù)的測(cè)定參照王曉霞等[2]的方法,用氣相色譜儀(GC-2010,Shimadzu)測(cè)定揮發(fā)性脂肪酸(volatile fatty acids,VFA);使用嘌呤法測(cè)定微生物蛋白(microbial crude protein,MCP);比色法測(cè)定瘤胃液中氨態(tài)氮質(zhì)量濃度(ammonia-nitrogen,NH3-N);顯微鏡檢測(cè)瘤胃原蟲數(shù)量(protozoa counts,PC)。使用日立7020全自動(dòng)生化儀測(cè)定總蛋白(total protein,TP)、白蛋白(albumin,ALB)、球蛋白(globulin,GLOB)、血漿尿素氮(urea nitrogen,BUN)、葡萄糖(glucose,GLU)、肌酐(creatinine,CREA)、總膽紅素(total bilirubin,TBIL)、總膽固醇(total cholesterol,CHOL)、三酰甘油(triglyceride,TG)、游離脂肪酸(non-esterified fatty acid,NEFA)、谷丙轉(zhuǎn)氨酶(glutamic-pyruvic transaminase，ALT)、谷草轉(zhuǎn)氨酶(glutamic-oxalacetic transaminase,AST)、堿性磷酸酶(alkaline phosphatase，ALP)、超氧化物歧化酶(superoxide dismutase，SOD)、β-羥丁酸(β-hydroxybutyrate,BHB)等指標(biāo),試劑盒購(gòu)自寧波美康生物科技股份有限公司。

1.6統(tǒng)計(jì)分析

采用SAS 9.1.3混合線性模型對(duì)生產(chǎn)性能、表觀消化率、瘤胃發(fā)酵和血液生化指標(biāo)進(jìn)行統(tǒng)計(jì)分析,P<0.10表示有變化的趨勢(shì),P<0.05表示差異有統(tǒng)計(jì)學(xué)意義,P<0.01表示差異有高度統(tǒng)計(jì)學(xué)意義。

2結(jié)果

2.1生產(chǎn)性能

飼喂含無患子皂甙精料對(duì)25～28月齡后備牛生產(chǎn)性能的影響見表3和表4。2組試驗(yàn)牛的各項(xiàng)體尺數(shù)據(jù)和估測(cè)體質(zhì)量均隨著月齡的增加而增加,且試驗(yàn)組的增幅高于對(duì)照組?？赡苡捎谠囼?yàn)前期變化不顯著,導(dǎo)致整個(gè)試驗(yàn)期內(nèi)組間差異不顯著,處理和月齡之間也沒有顯著的交互作用,但試驗(yàn)后期試驗(yàn)組后備牛體質(zhì)量增幅明顯高于對(duì)照組,試驗(yàn)組全期日增質(zhì)量比對(duì)照組提高31%(P=0.05);試驗(yàn)組的相對(duì)增長(zhǎng)也較對(duì)照組有提高的趨勢(shì)(P<0.10),飼料質(zhì)量比也有降低的趨勢(shì)(P<0.10)?？梢?飼喂含無患子皂甙的精料能夠促進(jìn)25～28月齡后備牛生長(zhǎng),提高飼料利用效率,對(duì)企業(yè)生產(chǎn)效益的提高有重要意義。

表3　飼喂含無患子皂甙精料對(duì)25～28月齡后備牛生產(chǎn)性能的影響

表4飼喂含無患子皂甙精料對(duì)25～28月齡后備牛生產(chǎn)性能的影響

Table 4Effect of feeding Sapindoside-containing concentrate on productive performance of 25-28 month-old heifers

項(xiàng)目Item對(duì)照組Control試驗(yàn)組Experiment標(biāo)準(zhǔn)誤StandarderrorP值P-value采食量Feedintake/kg9.118.840.220.26日增質(zhì)量Averagedailymassgain/kg0.490.710.070.05相對(duì)增長(zhǎng)a)Relativegrowtha)/%9.2213.371.380.07飼料質(zhì)量比b)F/Gb)24.4814.033.87<0.10

a)相對(duì)增長(zhǎng)=(末質(zhì)量-初始質(zhì)量)/初始質(zhì)量×100%;b)飼料質(zhì)量比=日采食量/日增質(zhì)量。

a) Relative growth= (final mass - initial mass)/initial mass×100%; b) F/G=feed intake/average daily mass gain.

2.2營(yíng)養(yǎng)物質(zhì)消化率

飼喂含無患子皂甙精料對(duì)25～28月齡后備牛營(yíng)養(yǎng)物質(zhì)消化率的影響見表5。試驗(yàn)組DM(P<0.01)、OM(P<0.01)、CP(P<0.01)、NDF(P<0.05)、ADF(P<0.01)和粗灰分(P<0.01)的表觀消化率都高于對(duì)照組,EE的表觀消化率也略有升高，但差異無統(tǒng)計(jì)學(xué)意義。

表5飼喂含無患子皂甙精料對(duì)25～28月齡后備牛營(yíng)養(yǎng)物質(zhì)表觀消化率的影響

Table 5Effect of feeding Sapindoside-containing concentrate on apparent digestibility of 25-28 month-old heifers

%

DM:干物質(zhì);OM:有機(jī)物；CP:粗蛋白;NDF:中性洗滌纖維;ADF:酸性洗滌纖維；EE:粗脂肪.

DM: Dry matter; OM：Organic matter； CP: Crude protein; NDF: Neutral detergent fiber; ADF: Acid detergent fiber； EE: Ether extract.

2.3瘤胃發(fā)酵參數(shù)

飼喂含無患子皂甙精料對(duì)25～28月齡后備牛瘤胃發(fā)酵參數(shù)的影響見表6。飼喂含無患子皂甙精料后,試驗(yàn)組與對(duì)照組相比,原蟲密度、氨態(tài)氮質(zhì)量濃度、總VFA以及乙酸和丙酸都沒有發(fā)生顯著變化,但pH值顯著升高(P<0.05),微生物蛋白質(zhì)量濃度、丁酸濃度和估測(cè)甲烷產(chǎn)量明顯降低(P<0.05),乙酸丙酸濃度之比下降極顯著，差異有高度統(tǒng)計(jì)學(xué)意義(P<0.01)。

表6飼喂含無患子皂甙精料對(duì)25～28月齡后備牛瘤胃發(fā)酵參數(shù)的影響

Table 6Effect of feeding Sapindoside-containing concentrate on rumen fermentation parameters of 25-28 month-old heifers

項(xiàng)目Item對(duì)照組Control試驗(yàn)組Experiment標(biāo)準(zhǔn)誤StandarderrorP值P-valuepH6.326.660.11<0.05原蟲密度PC/(105/mL)7.405.671.460.42ρ/(氨態(tài)氮)NH3-N/(mg/dL)14.8314.270.910.67ρ/(微生物蛋白)MCP/(mg/mL)2.561.530.32<0.05c/(總揮發(fā)性脂肪酸)TotalVFA/(mmol/L)62.7555.553.690.20c/(乙酸)Acetate/(mmol/L)48.2940.642.730.08c/(丙酸)Propionate/(mmol/L)10.8112.340.810.21c/(丁酸)Butyrate/(mmol/L)3.652.560.290.03乙酸/丙酸Acetatetopropionateratio4.483.310.15<0.01c/(甲烷)a)Methanea)/(mmol/L)20.2215.921.150.02

PC: Protozoa counts; MCP: Microbial crude protein; VFA: Volatile fatty acids.

a)甲烷產(chǎn)量為估測(cè)值,估測(cè)公式為CH4/(mmol/L)=0.45C2-0.275C3+0.40C4,其中C2、C3、C4分別代表乙酸、丙酸、丁酸的產(chǎn)量[4]。

a) Methane production was calculated, formula: CH4content/(mmol/L)=0.45C2-0.275C3+0.40C4, where C2, C3 and C4 present the production of acetate, propionate and butyrate, respectively.

2.4血液生化指標(biāo)

飼喂含無患子皂甙精料對(duì)25～28月齡后備牛血液生化指標(biāo)的影響見表7。飼喂含無患子皂甙精料對(duì)免疫指標(biāo)(總蛋白、白蛋白、球蛋白、白蛋白與球蛋白濃度之比),代謝類指標(biāo)(尿素氮、葡萄糖、總膽固醇、三酰甘油、游離脂肪酸、β-羥丁酸),抗氧化指標(biāo)(超氧化物歧化酶),肝指標(biāo)(谷丙轉(zhuǎn)氨酶、堿性磷酸酶)和腎指標(biāo)(總膽紅素、肌酐)均沒有顯著影響,谷草轉(zhuǎn)氨酶略有降低(P<0.10)。

表7飼喂含無患子皂甙精料對(duì)25～28月齡后備牛血液生化指標(biāo)的影響

Table 7Effect of feeding Sapindoside-containing concentrate on plasma biochemical indictors of 25-28 month-old heifers

項(xiàng)目Item對(duì)照組Control試驗(yàn)組Experiment標(biāo)準(zhǔn)誤StandarderrorP值P-valueρ(總蛋白)TP/(g/L)76.2074.971.960.67ρ(白蛋白)ALB/(g/L)26.6927.530.580.33ρ(球蛋白)GLOB/(g/L)49.5147.452.250.53白蛋白/球蛋白A/G0.550.590.030.37c(尿素氮)BUN/(mmol/L)5.445.430.260.97c(葡萄糖)GLU/(mmol/L)2.492.440.120.75c(總膽固醇)CHOL/(mmol/L)2.312.270.120.78c(三酰甘油)TG/(mmol/L)0.270.280.030.71c(游離脂肪酸)NEFA/(μmol/L)137.33189.1729.640.24c(β-羥丁酸)BHBA/(μmol/L)344.33319.8315.720.30ρ(總膽紅素)TBIL/(mg/dL)0.781.670.160.12c(肌酐)CREA/(μmol/L)109.50104.006.860.58谷丙轉(zhuǎn)氨酶ALT/(U/L)20.4719.281.170.49谷草轉(zhuǎn)氨酶AST/(U/L)59.1752.182.590.09堿性磷酸酶ALP/(U/L)63.7558.325.820.52超氧化物歧化酶SOD/(U/mL)79.3785.682.830.15

TP: Total protein; ALB: Albumin; GLOB: Globulin; A/G: Albumin/globulin; BUN: Urea nitrogen; GLU: Glucose; CHOL: Total cholesterol; TG: Total cholesterol; NEFA: Non-esterified fatty acid; BHBA:β-hydroxybutyrate; TBIL: Total bilirubin; CREA: Creatinine; ALT: glutamic-pyruvic transaminase; AST: Glutamic-oxalacetic transaminase; ALP: Alkaline phosphatase; SOD: Superoxide dismutase.

3討論

3.1飼喂含無患子皂甙的精料對(duì)25～28月齡后備牛生產(chǎn)性能的影響

通常認(rèn)為驅(qū)除或抑制瘤胃原蟲有助于反芻動(dòng)物生產(chǎn)性能的提高。已有的研究表明皂甙的驅(qū)蟲活性能夠提高湖羊的生產(chǎn)性能[5],Khodabakhshi等[6]給泌乳牛飼喂一種富含皂甙的商品RumexSc后,產(chǎn)奶量顯著提高,Mirza等[7]在尿素糖蜜舔磚的基礎(chǔ)上給后備牛飼喂絲蘭皂甙后,飼料轉(zhuǎn)化效率明顯提高。本試驗(yàn)選取的后備牛體型已接近成年牛體型大小,因此體尺變化幅度有限,但在試驗(yàn)后期,試驗(yàn)組體尺逐漸高于對(duì)照組,從全期來看試驗(yàn)組日增質(zhì)量顯著高于對(duì)照組,相對(duì)增長(zhǎng)和飼料質(zhì)量比分別有提高和降低的趨勢(shì),雖然距離預(yù)期效果還有差距,但試驗(yàn)組表現(xiàn)出了比對(duì)照組更好的生產(chǎn)效果。

也有研究表明皂甙的添加量不足可能會(huì)影響動(dòng)物的生產(chǎn)性能。Holtshausen等[8]體外添加絲蘭皂甙和皂樹皂甙對(duì)瘤胃發(fā)酵促進(jìn)效果明顯,但體內(nèi)添加低劑量[10 g/(d·頭)]皂甙后對(duì)產(chǎn)奶量沒有影響,反而降低了產(chǎn)奶效率；Singer等[9]也發(fā)現(xiàn)5、10和15 g/(d·頭)的絲蘭皂甙對(duì)泌乳牛的奶產(chǎn)量、乳成分、體質(zhì)量變化以及原蟲數(shù)量、VFA等均沒有產(chǎn)生影響；Benchaar等[10]添加6 g/d的絲蘭皂甙也得到了同樣的結(jié)果。因此偏低的皂甙添加量可能對(duì)瘤胃發(fā)酵影響較小,進(jìn)而也不會(huì)顯著提高動(dòng)物的生產(chǎn)性能。本試驗(yàn)皂甙的添加量為4.8 g/d,添加量偏低可能是造成動(dòng)物生產(chǎn)性能提高幅度有限的主要原因,還需要進(jìn)一步增大劑量來觀察是否會(huì)促進(jìn)動(dòng)物的生產(chǎn)性能。

3.2飼喂含無患子皂甙的精料對(duì)25～28月齡后備牛營(yíng)養(yǎng)物質(zhì)消化率的影響

Lu等[11]發(fā)現(xiàn)苜蓿皂甙增加了有機(jī)物和纖維素的消化率；Goetsch等[12]研究發(fā)現(xiàn)絲蘭皂甙增加了淀粉和粗蛋白的消化率。在本試驗(yàn)中,試驗(yàn)組DM、OM、CP、NDF、ADF和粗灰分的消化率都高于對(duì)照組,可能是皂甙選擇性促進(jìn)了某些細(xì)菌的生長(zhǎng),這些細(xì)菌的增殖消化吸收了飼料底物。有研究表明,低劑量的皂甙可能會(huì)增加細(xì)胞膜的通透性[13],細(xì)胞就可以增加對(duì)營(yíng)養(yǎng)物質(zhì)的吸收；低劑量的皂甙也會(huì)增加瘤胃內(nèi)真菌的數(shù)量[14],而真菌比細(xì)菌能產(chǎn)生更多的酶,降解更多的底物,特別是真菌分泌的纖維素酶和木聚糖酶對(duì)降解植物細(xì)胞壁起重要作用。也有研究報(bào)道表明,皂甙能夠降低食糜在瘤胃內(nèi)的流通速率[11]和增加小腸黏膜的通透性[15],進(jìn)而提高飼料在瘤胃內(nèi)的降解率,吸收一些平時(shí)不能被滲透進(jìn)入小腸的物質(zhì)?？梢?皂甙可以通過多種途徑影響反芻動(dòng)物對(duì)營(yíng)養(yǎng)物質(zhì)的消化率,而本試驗(yàn)飼喂含無患子的精料能夠顯著提高后備牛對(duì)營(yíng)養(yǎng)物質(zhì)的消化率,這可能也是造成試驗(yàn)組采食量低于對(duì)照組,但生產(chǎn)性能沒有降低反而有提高趨勢(shì)的原因。

3.3飼喂含無患子皂甙的精料對(duì)25～28月齡后備牛瘤胃發(fā)酵的影響

在本試驗(yàn)中乙酸丙酸濃度比和估測(cè)的甲烷產(chǎn)量都有降低,其中乙酸丙酸濃度比降低使得瘤胃發(fā)酵從乙酸型向丙酸型轉(zhuǎn)變,促進(jìn)機(jī)體對(duì)能量的合成和轉(zhuǎn)化,甲烷產(chǎn)量降低則能夠減少能量消耗,提高機(jī)體對(duì)能量的利用效率。但皂甙的主要作用是降低瘤胃原蟲數(shù)量,其抗原蟲活性已經(jīng)被體外[2]和體內(nèi)試驗(yàn)證實(shí)[14]。在本試驗(yàn)中,試驗(yàn)組原蟲數(shù)量、氨態(tài)氮和揮發(fā)性脂肪酸略有減少,但差異不顯著;類似地,Baah等[16]發(fā)現(xiàn)在限制飼喂的條件下(每日飼喂85%的干物質(zhì)采食量),添加0.8 g/kg干物質(zhì)采食量皂樹皂甙對(duì)原蟲數(shù)量,氨態(tài)氮濃度和揮發(fā)性脂肪酸濃度沒有產(chǎn)生影響;Singer等[9]也發(fā)現(xiàn)5、10和15 g/(d·頭)的絲蘭皂甙對(duì)泌乳牛瘤胃內(nèi)原蟲數(shù)量、VFA等均沒有產(chǎn)生影響；Benchaar等[10]添加6 g/d的絲蘭皂甙也得到了同樣的結(jié)果。本試驗(yàn)皂甙的添加量為4.8 g/d,可能皂甙添加量偏低,導(dǎo)致其對(duì)原蟲的抑制效應(yīng)沒有發(fā)揮出來,而其中特定的一小部分促進(jìn)了某些細(xì)菌(比如反芻獸新月形單胞菌和產(chǎn)甲烷菌)的生長(zhǎng)或提高了其活性,因而使乙酸丙酸濃度比和估測(cè)的甲烷產(chǎn)量降低?？梢?飼喂含無患子的精料能夠促進(jìn)某些發(fā)酵參數(shù)的變化,但沒有能夠徹底改變25～28月齡后備牛瘤胃發(fā)酵模式,而這也在生產(chǎn)性能上得到了相應(yīng)的表現(xiàn),因此這也提示我們還需要加大皂甙的添加劑量來觀察其隨后的反應(yīng)。另外,Lu等[11]發(fā)現(xiàn)苜蓿皂甙降低了微生物蛋白的合成效率,同時(shí)細(xì)菌生長(zhǎng)也被抑制,在本試驗(yàn)中試驗(yàn)組MCP濃度低于對(duì)照組,是否也是因無患子皂甙降低了微生物蛋白的合成,有待進(jìn)一步研究。

3.4飼喂含無患子皂甙的精料對(duì)25～28月齡后備牛血液生化指標(biāo)的影響

本試驗(yàn)飼喂含無患子皂甙的精料對(duì)血液生化指標(biāo)沒有顯著影響,表明此階段后備牛機(jī)體代謝良好。如Li等[17]給綿羊飼喂絲蘭皂甙對(duì)血清尿素氮、肌酐、谷草轉(zhuǎn)氨酶、堿性磷酸酶、谷氨酰轉(zhuǎn)肽酶、乳酸脫氫酶沒有發(fā)生顯著影響,所有指標(biāo)均在正常范圍內(nèi)?？梢?飼喂含無患子皂甙的精料對(duì)反芻動(dòng)物的物質(zhì)代謝、免疫、肝功能、腎功能和抗氧化功能沒有不良影響。

4結(jié)論

對(duì)于25～28月齡的后備牛,飼喂含無患子皂甙的精料有提高其生產(chǎn)性能的趨勢(shì),在一定程度上促進(jìn)了瘤胃發(fā)酵,但還需增大皂甙的劑量做進(jìn)一步研究。

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*通信作者(Corresponding author):陳國(guó)宏,E-mail:ghchen@yzu.edu.cn

第一作者聯(lián)系方式:李麗,E-mail:576801792@qq.com

URL:http://www.cnki.net/kcms/detail/33.1247.s.20150519.1352.016.html