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      反光膜對(duì)舍內(nèi)溫?zé)岘h(huán)境及青年奶牛血液生化指標(biāo)的影響

      2023-01-16 09:47:00趙俐辰趙心念宋連杰王亞男李永亮郭建軍高玉紅
      關(guān)鍵詞:反光膜表面溫度鋪設(shè)

      趙俐辰,趙心念,馮 曼,宋連杰,王亞男,李永亮,郭建軍,高玉紅

      反光膜對(duì)舍內(nèi)溫?zé)岘h(huán)境及青年奶牛血液生化指標(biāo)的影響

      趙俐辰1,趙心念1,馮 曼2,宋連杰2,王亞男2,李永亮1,郭建軍2,高玉紅1※

      (1. 河北農(nóng)業(yè)大學(xué)動(dòng)物科技學(xué)院,保定 071001; 2. 承德市農(nóng)林科學(xué)院畜牧研究所,承德 067000)

      針對(duì)夏季單彩鋼屋頂結(jié)構(gòu)的奶牛棚舍隔熱性能差、舍溫高的生產(chǎn)難題,該研究對(duì)單彩鋼屋頂進(jìn)行改造,彩鋼板外側(cè)鋪設(shè)反光膜(鋪膜舍),未鋪設(shè)反光膜的相同結(jié)構(gòu)牛舍作為對(duì)照舍,每棟舍飼養(yǎng)90頭青年奶牛。測(cè)定7-8月和9-10月份牛舍溫?zé)岘h(huán)境、舍中青年奶牛的生理指標(biāo)、血液生化指標(biāo)及生產(chǎn)性能,通過(guò)對(duì)比分析鋪膜舍與對(duì)照舍各指標(biāo)評(píng)價(jià)鋪膜緩解牛熱應(yīng)激的效果。結(jié)果表明:1)7—8月份和9—10月份中午時(shí)段鋪膜舍屋頂內(nèi)表面溫度較對(duì)照舍分別降低10.48 ℃和8.16 ℃(<0.01),且舍溫在7—8月份的09:30-13:30降低0.87~1.04℃(<0.05);2)7-8月份鋪膜舍青年奶牛的呼吸頻率較對(duì)照舍降低12.51%(<0.01),且10:00-14:00躺臥比例增加7.90%~18.77%(<0.05),而9-10月份兩棟舍未表現(xiàn)出顯著性差異(>0.05)。產(chǎn)犢后鋪膜舍的產(chǎn)奶量較對(duì)照舍表現(xiàn)出增加趨勢(shì),且乳蛋白率提高4.85%(<0.05);3)7-8月份鋪膜舍青年牛的血清超氧化物歧化酶和總抗氧化能力水平較對(duì)照舍分別提高5.71%和10.47%(<0.05),血清白細(xì)胞介素4及其mRNA水平分別提高24.78%和25.43%(<0.01),且血清熱應(yīng)激蛋白HSP60和HSP70含量?jī)蓷澤嶂g也表現(xiàn)出顯著性差異(<0.05),鋪膜舍較對(duì)照舍分別降低14.06%和15.87%,且HSP70 mRNA表達(dá)量也表現(xiàn)出顯著性降低(<0.05)。綜上,單彩鋼屋頂進(jìn)行鋪膜改造后,能顯著降低牛舍溫度(7-8月份),有效緩解青年奶牛的熱應(yīng)激,提高青年奶牛產(chǎn)犢后的泌乳性能。

      溫度;奶牛;濕度;奶牛舍;抗氧化性能;免疫性能

      0 引 言

      隨著全球氣候變暖,奶牛遭受熱應(yīng)激的風(fēng)險(xiǎn)逐漸增加。據(jù)聯(lián)合國(guó)政府間氣候變化專門委員會(huì)IPCC第五次評(píng)估報(bào)告(AR5),預(yù)計(jì)到2035年全球地表平均溫度將升高0.3~0.7 ℃[1]。高溫環(huán)境下,奶牛內(nèi)源性產(chǎn)熱無(wú)法有效擴(kuò)散,加之從外界環(huán)境獲得的熱量,導(dǎo)致體溫升高,產(chǎn)生熱應(yīng)激反應(yīng)[2]。研究已經(jīng)證實(shí),熱應(yīng)激條件下奶牛呼吸頻率和體溫增加,采食量下降,產(chǎn)奶量降低25%~40%[3-4],尤其對(duì)頭胎青年奶牛而言,這個(gè)時(shí)期是胎兒快速發(fā)育和乳腺更新?lián)Q代的重要階段,熱應(yīng)激勢(shì)必會(huì)影響奶牛的泌乳性能及初生犢牛的生長(zhǎng)發(fā)育。因此,做好預(yù)防青年奶牛的防暑降溫工作尤為重要。

      為了緩解夏季高溫對(duì)奶牛造成的影響,華北地區(qū)大部分奶牛場(chǎng)通過(guò)“風(fēng)扇+噴淋”降溫模式以緩解熱應(yīng)激[5],但對(duì)于單彩鋼屋頂結(jié)構(gòu)的棚舍,該降溫模式仍難以有效緩解奶牛的熱應(yīng)激。目前中國(guó)仍有部分奶牛舍屋頂使用單層彩鋼板,其隔熱性能遠(yuǎn)低于復(fù)合板結(jié)構(gòu)[6-7],若將單彩鋼屋頂改造為復(fù)合板結(jié)構(gòu),成本會(huì)大大增加,養(yǎng)殖場(chǎng)/戶難以接受。反光膜作為一種新型建筑材料,通常為鋁箔、鍍鋁膜或者鋁塑膜結(jié)構(gòu),因其具備良好的隔熱效果,已廣泛應(yīng)用于建筑物或構(gòu)筑物的表面[8],目前反光膜應(yīng)用于畜禽建筑以緩解熱應(yīng)激的研究報(bào)道較少[9]?;诖?,本試驗(yàn)對(duì)單彩鋼板結(jié)構(gòu)的棚舍進(jìn)行外表面鋪設(shè)反光膜的改造,并對(duì)棚舍外圍護(hù)結(jié)構(gòu)的內(nèi)表面溫度和舍內(nèi)環(huán)境溫濕度進(jìn)行測(cè)定,通過(guò)檢測(cè)青年奶牛生理指標(biāo)、血清抗氧化酶活性和免疫性能,了解反光膜對(duì)奶牛夏季熱應(yīng)激的緩解效果,以期為單彩鋼棚舍的改造提供依據(jù)。

      1 材料與方法

      1.1 試驗(yàn)時(shí)間和地點(diǎn)

      試驗(yàn)于2020年6—10月份在河北保定市某規(guī)模化奶牛場(chǎng)進(jìn)行。

      1.2 試驗(yàn)設(shè)計(jì)

      選擇2棟結(jié)構(gòu)完全相同、屋頂材料為1 mm厚藍(lán)色單層彩鋼板的南北向棚舍,一棟舍作為試驗(yàn)舍,在單彩鋼板外表面鋪設(shè)0.375 mm厚的灰色鍍鋁層反光膜,即鋪膜舍。另一棟舍作為對(duì)照舍,屋頂表面不做任何處理。2棟舍跨度均為31 m,長(zhǎng)度50 m,檐高5.5 m,脊高13 m,雙列單走道,設(shè)置對(duì)頭臥床。每棟舍飼養(yǎng)90頭(體質(zhì)量為(380±20)kg,(16±0.4)月齡)健康的青年荷斯坦奶牛,每頭牛占舍面積為15 m2。牛舍建筑結(jié)構(gòu)如圖1所示。

      注:A1-A3、B1-B3、C1-C3為屋頂內(nèi)表面溫度測(cè)點(diǎn);D1、D4為臥床溫度測(cè)點(diǎn);D2、D3為料道溫度測(cè)點(diǎn);E1-E8為承重柱溫度測(cè)點(diǎn)。

      整個(gè)試驗(yàn)分2個(gè)階段進(jìn)行,即7-8月份和9-10月份,2棟舍的降溫措施均采用吹風(fēng)+噴淋,風(fēng)機(jī)(1.2 m,0.75 kW)裝于舍內(nèi)立柱上,高度2.1 m,傾斜角度25°,相鄰間距6 m,當(dāng)外界環(huán)境溫度超過(guò)23 ℃時(shí),開(kāi)啟風(fēng)機(jī)和噴淋;噴淋采取間歇方式(噴1 min,停5 min),噴頭安裝高度1.8 m,相鄰噴頭間隔1.5 m。整個(gè)試驗(yàn)期2棟舍青年奶牛均飼喂相同的全混合日糧(Total Mixed Ration, TMR),每日撒料2次(06:00和18:00),自由采食,自由飲水,刮糞板機(jī)械化清糞,每隔2 h清糞1次。全期試驗(yàn)牛的飼養(yǎng)管理完全一致。

      1.3 檢測(cè)指標(biāo)及方法

      1.3.1 外圍護(hù)結(jié)構(gòu)內(nèi)表面溫度測(cè)定

      按牛舍長(zhǎng)軸方向均勻選擇3個(gè)截面,利用紅外熱成像儀(Testo-890,德國(guó))分別采集3個(gè)截面的外圍護(hù)結(jié)構(gòu)內(nèi)表面(屋頂、料道、承重柱等)清晰的紅外熱像圖,每個(gè)截面均勻布置21個(gè)外圍護(hù)結(jié)構(gòu)溫度測(cè)點(diǎn)(A1,A2,A3,B1,……,E8),如圖1所示。每個(gè)溫度測(cè)點(diǎn)提取3個(gè)相鄰的溫度信息作為重復(fù),以3個(gè)重復(fù)的均值溫度作為采樣點(diǎn)的實(shí)測(cè)值。每周連續(xù)檢測(cè)3 d,即,早晨(06:00-07:00)、中午(12:00-13:00)和晚上(18:00-19:00)。

      1.3.2 牛舍環(huán)境溫濕度和溫濕指數(shù)的測(cè)定

      利用電子溫濕度記錄儀(KTH-350-I型,法國(guó))對(duì)舍內(nèi)外溫度和相對(duì)濕度進(jìn)行連續(xù)測(cè)定,每0.5 h自動(dòng)采集溫度和濕度數(shù)據(jù),檢測(cè)高度均為垂直地面1.7 m,分別于南、北兩側(cè)臥床及中間料道兩側(cè),每棟舍共設(shè)12個(gè)溫濕度測(cè)點(diǎn);舍外設(shè)3個(gè)采樣點(diǎn),均勻布置于場(chǎng)區(qū)凈道。試驗(yàn)結(jié)束后,繪制24 h的溫濕度連續(xù)曲線,并計(jì)算溫濕指數(shù)(Temperature and Humidity Index, THI)[10]。

      1.3.3 青年奶牛生理指標(biāo)的測(cè)定

      每棟舍隨機(jī)選擇8頭青年奶牛,分別于各試驗(yàn)階段末3 d采用頸枷將牛固定,選擇中午12:00-14:00時(shí)段對(duì)青年奶牛的呼吸頻率、直腸溫度和皮溫進(jìn)行測(cè)定。呼吸頻率測(cè)定時(shí),利用秒表和計(jì)數(shù)器記錄連續(xù)3 min牛的呼吸次數(shù),連續(xù)測(cè)3次。直腸溫度利用獸用體溫計(jì)進(jìn)行測(cè)量,將體溫計(jì)消毒并涂上潤(rùn)滑劑后插入肛門3~5 min后記錄體溫。皮溫的測(cè)量參照《家畜環(huán)境衛(wèi)生學(xué)》(第4版)的計(jì)算方法[11]。利用紅外熱成像儀(Testo-890,德國(guó))采集青年奶牛清晰的紅外熱像圖,并對(duì)牛的軀干上部(軀干上部)、軀干下部(軀干下部)、四肢上部(四肢上部)、四肢下部 (四肢下部)、頸部(頸部)和耳部(耳部)分別選取3個(gè)位點(diǎn)提取溫度信息,以3個(gè)位點(diǎn)的均值作為實(shí)測(cè)值,平均皮溫(Average skin temperature, AST)計(jì)算式如下:

      AST(℃)=0.25軀干上部+0.25軀干下部+0.32四肢上部+

      0.12四肢下部+0.04頸部+0.02耳朵(1)

      1.3.4 青年奶牛行為的測(cè)定

      分別于7-8月份和9-10月份對(duì)青年奶牛行為進(jìn)行記錄,每2周連續(xù)測(cè)定3 d,每天選擇8個(gè)時(shí)間點(diǎn)(06:00、08:00、10:00、12:00、14:00、16:00、18:00和20:00)對(duì)躺臥、站立、采食和飲水的牛群數(shù)量進(jìn)行記錄并計(jì)算各種行為的比例。

      1.3.5 奶牛泌乳性能的測(cè)定

      青年奶牛產(chǎn)犢后測(cè)定一個(gè)泌乳周期(305 d)的產(chǎn)奶量,記錄每天每頭牛的產(chǎn)奶量,并將產(chǎn)奶量轉(zhuǎn)化為4%校正乳(Fat Correction Milk, FCM)[12]。另外,整個(gè)泌乳周期的每個(gè)月末連續(xù)3 d采集每次擠奶時(shí)的奶樣,每日擠奶3次(05:00、12:00和18:00),每次各舍采集100 mL奶樣,將3個(gè)時(shí)間點(diǎn)的奶樣按4∶3∶3比例加入盛有重鉻酸鉀的試管中搖勻[13],送至河北省種畜禽質(zhì)量監(jiān)測(cè)站DHI中心檢測(cè)乳成分。

      1.3.6 青年奶牛血清抗氧化酶含量的測(cè)定

      分別于各試驗(yàn)階段末的前一天晚上對(duì)牛進(jìn)行禁水禁食,次日早晨進(jìn)行空腹采血??紤]到奶牛在妊娠期因采血可能會(huì)受到刺激而導(dǎo)致不良后果,每組隨機(jī)選取8頭牛,使用一次性采血針和抗凝真空牛尾靜脈采血10 mL,裝入EDTA抗凝真空采血管中,經(jīng)3 000 r/min離心15 min,取上層血清分裝,一部分用于血清抗氧化酶和免疫分子指標(biāo)蛋白含量的測(cè)定,?20 ℃保存;另一部分用于基因定量表達(dá)測(cè)定的血清樣品立即放入抗降解RNA的離心管中,?80 ℃保存。

      測(cè)定的抗氧化酶含量包括丙二醛(Malondialdehyde,MDA)、超氧化物歧化酶(Superoxide Dismutase,SOD)、谷胱甘肽-S轉(zhuǎn)移酶(Glutathione-S Transferase,GSH-ST)、總抗氧化能力(Total Antioxidant Capacity,T-AOC),該4種酶活的測(cè)定方法按照南京建成生物工程所的試劑盒說(shuō)明書進(jìn)行操作,使用ECA2000B半自動(dòng)生化分析儀直接讀取數(shù)據(jù)。

      1.3.7 青年奶牛血清免疫指標(biāo)含量的測(cè)定

      測(cè)定的血清免疫指標(biāo)包括2種白細(xì)胞介素(IL-4和IL-6)、3種免疫球蛋白(IgA、IgG和IgM)和3種熱休克蛋白(HSP60、HSP70和HSP90),白細(xì)胞介素和免疫球蛋白含量按照ELISA試劑盒(南京建成生物工程研究所)說(shuō)明書使用酶標(biāo)儀(華衛(wèi)德朗DR-200BS)進(jìn)行測(cè)定;熱休克蛋白含量采用酶聯(lián)免疫吸附雙抗體夾心法(ELISA)進(jìn)行測(cè)定。

      1.3.8 血清基因定量表達(dá)水平的測(cè)定

      選擇上述血清抗氧化酶和免疫指標(biāo)中效果顯著的指標(biāo)進(jìn)行基因定量表達(dá)水平的測(cè)定。

      采用TRNzol提取樣品總RNA并通過(guò)凝膠電泳和波長(zhǎng)260 nm檢測(cè)RNA提取質(zhì)量,OD260 nm/OD280 nm為1.8~2.1時(shí)可進(jìn)行反轉(zhuǎn)錄,按照反轉(zhuǎn)錄試劑盒說(shuō)明書進(jìn)行。主要操作如下:37 ℃孵育15 min,然后85 ℃ 5 s進(jìn)行反轉(zhuǎn)錄,cDNA保存放?20℃冰箱備用。再根據(jù)SYBR GreenⅠReal Time PCR檢測(cè)系統(tǒng)說(shuō)明書進(jìn)行實(shí)時(shí)熒光定量PCR反應(yīng),PCR 擴(kuò)增程序?yàn)椋?5 ℃預(yù)變性10 min;95 ℃變性10 s;60 ℃退火60 s;95 ℃延伸15 s,循環(huán)40次。擴(kuò)增反應(yīng)結(jié)束后形成PCR產(chǎn)物的熔解曲線。所測(cè)基因的引物序列見(jiàn)表1。

      表1 所測(cè)基因的引物序列

      1.4 數(shù)據(jù)分析

      利用SPSS22.0統(tǒng)計(jì)軟件分析試驗(yàn)數(shù)據(jù),兩棟舍數(shù)據(jù)比較的統(tǒng)計(jì)分析采用獨(dú)立樣本檢驗(yàn),<0.05表示差異顯著,<0.01表示差異極顯著,0.05<<0.1表示存在顯著性趨勢(shì)。數(shù)據(jù)以平均值±標(biāo)準(zhǔn)誤表示。另外,利用熱成像分析軟件(Testo IRSoft2)對(duì)熱譜圖像進(jìn)行處理,提取溫度信息;并利用GraphPad Prism 9.2對(duì)青年奶牛的血清熱休克蛋白含量及其基因表達(dá)量進(jìn)行繪圖。

      2 結(jié)果與分析

      2.1 屋頂鋪設(shè)反光膜對(duì)牛舍外圍護(hù)結(jié)構(gòu)內(nèi)表面溫度的影響

      單彩鋼屋頂外表面鋪設(shè)反光膜對(duì)外圍護(hù)結(jié)構(gòu)內(nèi)表面溫度的影響如表2所示。7-8月份12:00-13:00時(shí)段2棟舍外圍護(hù)結(jié)構(gòu)表面溫度均達(dá)到峰值,且該時(shí)段鋪膜舍屋頂?shù)膬?nèi)表面溫度和料道表面溫度與對(duì)照舍比較均表現(xiàn)出顯著性差異(<0.05),屋頂內(nèi)表溫度較對(duì)照舍降低10.48℃(<0.01),料道溫度較對(duì)照舍降低1.97 ℃(<0.05)。如圖2所示,7-8月份12:00-13:00時(shí)段對(duì)照舍屋頂內(nèi)表面溫度最高可達(dá)45.5 ℃,而鋪膜舍為34.5 ℃,2棟舍表現(xiàn)出極顯著差異(<0.01);9-10月份12:00-13:00鋪膜舍較對(duì)照舍降低8.16 ℃(<0.01)。06:00-07:00和18:00-19:00各外圍護(hù)結(jié)構(gòu)(屋頂、承重柱、料道及臥床)的表面溫度2棟舍之間均未表現(xiàn)出顯著性差異(>0.05)。

      表2 不同時(shí)段牛舍的外圍護(hù)結(jié)構(gòu)內(nèi)表面溫度

      Table 2 Inner surface temperature of cowshed enclosure in different periods ℃

      注:各試驗(yàn)期同一時(shí)段同列不同大寫字母表示差異極顯著(<0.01),不同小寫字母表示差異顯著(<0.05),無(wú)字母標(biāo)注表示差異不顯著(>0.05),下同。

      Note: At same time stage for each period, different capital letters in same column mean extremely significant difference (<0.01), and different small letters mean significant difference (<0.05); no letter means no significant difference (>0.05), the same as below.

      圖2 7—8月份屋頂內(nèi)表面溫度對(duì)比圖(12:00—13:00)

      2.2 屋頂鋪設(shè)反光膜對(duì)牛舍環(huán)境溫濕度的影響

      屋頂鋪設(shè)反光膜對(duì)牛舍環(huán)境溫濕度的影響如圖3所示。7-8月份鋪膜舍和對(duì)照舍環(huán)境溫度變化范圍分別為22.95~29.39 ℃(平均溫度26.03 ℃)和22.92~30.23 ℃(平均溫度26.19 ℃),濕度分別為69.65%~90.77%(平均濕度82.71%)和67.99%~89.91%(平均濕度82.61%)。如表3所示,全天中09:30~13:30時(shí)段鋪膜舍溫度較對(duì)照舍顯著降低(<0.05),降溫范圍達(dá)0.87~1.04 ℃(平均溫度0.96 ℃),而9-10月份鋪膜舍和對(duì)照舍環(huán)境溫度變化范圍分別為11.01~22.75 ℃(平均溫度15.86 ℃)和11.48~21.78 ℃(平均溫度15.78 ℃),差異不顯著(>0.05)。

      圖3 屋頂鋪設(shè)反光膜對(duì)牛舍溫濕度的影響

      表3 屋頂鋪設(shè)反光膜對(duì)牛舍環(huán)境溫度的影響(7-8月份)

      注:同行不同小寫字母表示差異顯著(<0.05)。

      Note: Small letters in the same trade mean significant difference (<0.05)。

      2.3 屋頂鋪設(shè)反光膜對(duì)牛舍溫濕指數(shù)的影響

      屋頂鋪設(shè)反光膜對(duì)舍內(nèi)THI的影響如圖4所示。根據(jù)中華人民共和國(guó)農(nóng)業(yè)行業(yè)標(biāo)準(zhǔn)關(guān)于奶牛熱應(yīng)激評(píng)價(jià)技術(shù)規(guī)范[NYT2363-2013],當(dāng)72

      2.4 屋頂鋪設(shè)反光膜對(duì)青年奶牛生理指標(biāo)的影響

      屋頂鋪設(shè)反光膜對(duì)青年奶牛生理指標(biāo)的影響如表4所示。7-8月份2棟舍青年奶牛的呼吸頻率分別為58.33和66.67次/min,存在顯著性差異(<0.01),鋪膜舍較對(duì)照舍降低12.51%,9-10月份差異不顯著(>0.05)。同時(shí)整個(gè)試驗(yàn)期2棟舍青年奶牛的直腸溫度和體表溫度均未達(dá)到差異顯著性水平(>0.05)。

      圖4 屋頂鋪設(shè)反光膜對(duì)舍內(nèi)溫濕指數(shù)的影響

      表4 屋頂鋪設(shè)反光膜對(duì)青年奶牛生理指標(biāo)的影響

      2.5 屋頂鋪設(shè)反光膜對(duì)青年奶牛行為的影響

      屋頂鋪設(shè)反光膜對(duì)青年奶牛行為的影響如圖5所示。7—8月份每天的10:00、12:00和14:00鋪膜舍青年奶牛的躺臥比例較對(duì)照舍表現(xiàn)出顯著性提高(<0.05),分別提高7.90%、18.77%和9.08%,同時(shí),2棟舍青年奶牛的站立比例也存在顯著性差異(<0.05),鋪膜舍較對(duì)照舍分別降低5.74%、11.63%和8.12%。7—8月份其余時(shí)間點(diǎn)和9—10月份全天2棟舍青年奶牛的躺臥、站立、飲水和采食4種行為比例均未表現(xiàn)出顯著性差異(>0.05)。

      圖5 屋頂鋪設(shè)反光膜對(duì)妊娠奶牛行為的影響

      2.6 屋頂鋪設(shè)反光膜對(duì)奶牛泌乳性能的影響

      屋頂鋪設(shè)反光膜對(duì)奶牛泌乳性能的影響如表5所示。7-8月份青年奶牛舍鋪膜對(duì)產(chǎn)犢后(305 d)奶牛的產(chǎn)奶量表現(xiàn)出增加的趨勢(shì)(=0.08),較對(duì)照舍增加了7.20%。2棟舍奶牛的乳蛋白率也表現(xiàn)出顯著性差異(<0.05),鋪膜舍較對(duì)照舍提高了4.85%。其余各項(xiàng)乳指標(biāo)均未表現(xiàn)出顯著性差異(>0.05)。

      表5 屋頂鋪設(shè)反光膜對(duì)奶牛泌乳性能的影響

      2.7 屋頂鋪設(shè)反光膜對(duì)青年奶牛血清抗氧化酶活性的影響

      屋頂鋪設(shè)反光膜對(duì)青年奶牛血清抗氧化活性的影響如表6所示。7-8月份鋪膜舍青年奶牛血清MDA、SOD和T-AOC的含量與對(duì)照舍之間表現(xiàn)出顯著性差異(<0.05),SOD和T-AOC含量較對(duì)照舍分別提高5.71%和10.47%,MDA含量降低15.45%,而GSH-ST含量2棟舍間未達(dá)到顯著性差異水平(>0.05)。9-10月份各種抗氧化酶活性2棟舍間均未達(dá)顯著水平(>0.05)。

      2.8 屋頂鋪設(shè)反光膜對(duì)青年奶牛血清免疫指標(biāo)的影響

      屋頂鋪設(shè)反光膜對(duì)青年奶牛血清免疫分子蛋白含量的影響如表7所示。7-8月份鋪膜舍青年奶牛血清中IgG、IgM、IL-4和IL-6的含量較對(duì)照舍表現(xiàn)出顯著性差異(<0.05),其中IL-4較對(duì)照舍提高了24.78%,差異達(dá)極顯著水平(<0.01),IgG、IgM和IL-6較對(duì)照舍分別提高了18.58%、21.23%和9.06%,差異達(dá)顯著水平(<0.05)。9-10月份鋪膜舍青年奶牛血清IL-4的含量較對(duì)照舍提高了23.62%(<0.05),IgA、IgG、IgM和IL-6未表現(xiàn)出顯著性差異(>0.05)。

      表6 屋頂鋪設(shè)反光膜對(duì)青年奶牛血清抗氧化酶含量的影響

      表7 屋頂鋪設(shè)反光膜對(duì)青年奶牛血清免疫指標(biāo)的影響

      屋頂鋪設(shè)反光膜對(duì)青年奶牛HSP含量的影響如圖6所示。7-8月份鋪膜舍青年奶牛血清中HSP60和HSP70含量均顯著低于對(duì)照舍(<0.05),分別降低14.06%和15.87%。而非熱季前期上述3種HSP含量2棟舍間均未表現(xiàn)出顯著性差異(>0.05)。

      2.9 屋頂鋪設(shè)反光膜對(duì)青年奶牛血清基因mRNA表達(dá)的影響

      從上述檢測(cè)的血清生化指標(biāo)中選擇反光膜影響極顯著的2種HSP(HSP60和HSP70)和白細(xì)胞介素IL-4進(jìn)行基因mRNA表達(dá)測(cè)定,結(jié)果如圖7所示。7-8月份鋪膜舍青年奶牛HSP70 mRNA表達(dá)量較對(duì)照舍顯著降低(<0.05),降低了24.48%,IL-4的mRNA表達(dá)量較對(duì)照舍顯著升高(<0.01),升高幅度達(dá)25.43%,但9-10月份上述3個(gè)基因表達(dá)量2棟舍均未表現(xiàn)出顯著性差異(>0.05)。

      注:**表示同一指標(biāo)2棟舍存在極顯著差異(P<0.01),*表示2棟舍存在顯著差異(P<0.05)。

      圖7 屋頂鋪設(shè)反光膜對(duì)青年奶牛敏感基因mRNA表達(dá)的影響

      3 討 論

      3.1 單彩鋼屋頂外鋪反光膜對(duì)舍內(nèi)溫?zé)岘h(huán)境的影響

      單層彩鋼屋頂是目前牛羊舍應(yīng)用較為普遍的結(jié)構(gòu),由于其熱阻低,隔熱性能差,往往導(dǎo)致夏季舍內(nèi)的高熱環(huán)境。鄧?yán)姷萚14]研究發(fā)現(xiàn),單彩鋼屋頂?shù)母魺嵝阅懿?,不僅體現(xiàn)在屋頂?shù)谋砻鏈囟雀?,而且升溫快。本文試?yàn)牛舍的單彩鋼屋頂厚度僅1 mm,7-8月份單彩鋼板的內(nèi)表面溫度高達(dá)42.82 ℃,當(dāng)單彩鋼板屋頂外側(cè)鋪設(shè)反光膜后,屋頂內(nèi)表面溫度降低,尤其中午時(shí)段(12:00-13:00),屋頂內(nèi)表面溫度降低了10.48 ℃,此時(shí)段舍內(nèi)溫度降低范圍達(dá)0.92~0.97 ℃,即使在9-10月份的非熱季期,12:00-13:00鋪膜舍屋頂?shù)膬?nèi)表面溫度較對(duì)照舍也有所降低,達(dá)8.16 ℃,此時(shí)段舍內(nèi)溫度降低0.80~1.01 ℃,明顯改善了舍內(nèi)的溫?zé)岘h(huán)境,與THI分析得到的結(jié)果一致。

      3.2 反光膜對(duì)青年奶牛生理指標(biāo)及泌乳性能的影響

      呼吸頻率和直腸體溫是反映家畜熱應(yīng)激生理特征的公認(rèn)指標(biāo)[15]。陳少侃等[16]研究認(rèn)為,呼吸頻率會(huì)隨熱應(yīng)激程度的增加而升高。彭丹丹[17]關(guān)于奶牛熱應(yīng)激的研究發(fā)現(xiàn),高THI環(huán)境下,奶牛直腸溫度可達(dá)到39.51 ℃,顯著高于低THI環(huán)境下的直腸溫度(39.22 ℃),且隨著熱應(yīng)激程度的增加,奶牛乳蛋白率和乳脂率顯著降低。本文試驗(yàn)中雖然兩棟舍青年奶牛的呼吸頻率均超過(guò)正常范圍,但單彩鋼屋頂鋪設(shè)反光膜明顯降低了青年奶牛在7-8月份的呼吸頻率,在一定程度上緩解了牛的熱應(yīng)激,從本文試驗(yàn)檢測(cè)到的牛行為變化也進(jìn)一步說(shuō)明了鋪膜后牛的熱應(yīng)激得到一定程度的緩解。行為是奶牛適應(yīng)環(huán)境并應(yīng)對(duì)環(huán)境變化最早出現(xiàn)反應(yīng)且容易觀察的指標(biāo),尤其躺臥與奶牛健康和泌乳性能息息相關(guān)。本文試驗(yàn)中屋頂鋪膜顯著提高了7-8月份青年奶牛的躺臥比例,10:00-14:00時(shí)段鋪膜舍牛的躺臥比例較對(duì)照舍提高了7.90%~18.77%,分析原因可能與09:30-13:30時(shí)段鋪膜舍的環(huán)境溫度較對(duì)照舍降低0.96 ℃密切相關(guān)。同時(shí),7-8月份鋪膜舍青年奶牛每天的站立時(shí)間較對(duì)照舍相應(yīng)減少。相關(guān)研究也表明,舒適的條件下奶牛往往選擇躺臥,而暴露于高溫環(huán)境下的奶牛經(jīng)常選擇站立[18],且隨著環(huán)境溫度的升高,奶牛的站立次數(shù)增加,站立時(shí)間延長(zhǎng),這可能是由于站立增加了身體表面與外界空氣的接觸面積,使體熱盡可能散發(fā)且耗能少,以此緩解高溫帶來(lái)的負(fù)效應(yīng)[19]。Allen 等[20]研究也表明,處于中度或重度熱應(yīng)激時(shí),奶牛站立比例高達(dá)68.2%,較無(wú)熱應(yīng)激狀態(tài)下奶牛的站立比例增加24.6%。本文試驗(yàn)中,7-8月份12:00時(shí)鋪膜舍(THI為80.89)青年奶牛站立比例較對(duì)照舍(THI為79.89)減少11.63%;14:00時(shí)鋪膜舍(THI為81.71)青年奶牛站立比例較對(duì)照舍(THI為80.49)減少8.12%。另外,本文試驗(yàn)中熱季期青年奶牛舍的屋頂進(jìn)行鋪膜改造后明顯改善了后期產(chǎn)犢后奶牛的泌乳性能。大量研究已經(jīng)證實(shí),熱環(huán)境顯著影響奶牛的產(chǎn)奶量和乳質(zhì)[21-22]。研究認(rèn)為,當(dāng)THI>72時(shí),每增加1個(gè)單位,產(chǎn)奶量降低0.2 kg[23]。本文試驗(yàn)中,妊娠階段鋪膜改造增加了產(chǎn)犢后奶牛的產(chǎn)奶量,較對(duì)照舍增加了7.20%,且乳質(zhì)也得到一定改善,乳蛋白含量顯著性提高。

      3.3 反光膜對(duì)青年奶??寡趸阅艿挠绊?/h3>

      高溫環(huán)境中反芻動(dòng)物機(jī)體的抗氧化系統(tǒng)往往遭到破壞,抗氧化酶的活性會(huì)降低,體內(nèi)的含氧自由基得不到及時(shí)清除,容易導(dǎo)致生物膜中不飽和脂類發(fā)生脂質(zhì)過(guò)氧化并形成脂質(zhì)過(guò)氧化物,其最終產(chǎn)物形成MDA[24]。研究指出,高熱環(huán)境下為了清除熱應(yīng)激誘導(dǎo)的多余自由基,血清中抗氧化酶系統(tǒng)(如SOD、T-AOC等)被大量消耗,抗氧化酶系統(tǒng)平衡因此被打破,從而加快了組織的脂質(zhì)過(guò)氧化。本文試驗(yàn)中鋪膜舍青年奶牛在7—8月份血清SOD和T-AOC的含量顯著升高,同時(shí)MDA的含量顯著降低,這說(shuō)明單彩鋼屋頂鋪膜在某種程度上緩解了牛的熱應(yīng)激,降低了因熱應(yīng)激導(dǎo)致的抗氧化系統(tǒng)破壞的風(fēng)險(xiǎn)。王換換等[25]研究認(rèn)為,熱應(yīng)激導(dǎo)致了機(jī)體抗氧化系統(tǒng)的失衡,處于熱應(yīng)激狀態(tài)下的奶牛肝臟中MDA的含量顯著增加,SOD和GSH-ST含量顯著下降,而無(wú)熱應(yīng)激發(fā)生的環(huán)境下抗氧化酶活性相對(duì)穩(wěn)定,本文試驗(yàn)與前人研究結(jié)果基本一致。由此可見(jiàn),熱應(yīng)激條件下單彩鋼屋頂鋪設(shè)反光膜可有效減少熱應(yīng)激對(duì)奶??寡趸到y(tǒng)的破壞,保護(hù)機(jī)體免受氧化應(yīng)激的損傷。

      3.4 反光膜對(duì)青年奶牛血清免疫性能的影響

      熱應(yīng)激容易破壞反芻動(dòng)物的免疫系統(tǒng),使機(jī)體的抵抗力下降[26]。Tao等[27]研究認(rèn)為,妊娠后期奶牛遭受熱應(yīng)激導(dǎo)致出生后犢牛的血清IgG含量顯著下降。本文試驗(yàn)中,7—8月份間單彩鋼屋頂鋪膜可使青年奶牛血清中IgG、IgM、IL-4和IL-6的含量顯著增加,甚至應(yīng)激期過(guò)后IL-4含量仍有所提高,降低了熱應(yīng)激對(duì)青年奶牛免疫性能的負(fù)面影響。IL-4作為一種具多種生物效應(yīng)的白細(xì)胞因子,對(duì)B細(xì)胞、T細(xì)胞、肥大細(xì)胞、巨噬細(xì)胞等均具免疫作用,可以增強(qiáng)IgG和IgE的免疫效果,促進(jìn)細(xì)胞免疫[28]。本文試驗(yàn)中IL-4的血清含量及其基因mRNA表達(dá)鋪膜舍均表現(xiàn)出顯著性增加,說(shuō)明鋪膜降溫措施在增強(qiáng)青年奶牛免疫功能方面起到了積極作用。

      HSP作為免疫反應(yīng)的部分指標(biāo),對(duì)熱應(yīng)激反應(yīng)非常敏感,這已在雞[29]、豬[30]、牛[31]和羊[32]的研究中被證實(shí),尤其HSP60和HSP70在熱應(yīng)激調(diào)控中扮演著重要的角色[33-34]。研究認(rèn)為,熱應(yīng)激條件下,HSP往往表現(xiàn)為蛋白表達(dá)量和基因表達(dá)上調(diào),減少變性或異常蛋白的積累以抵抗熱應(yīng)激反應(yīng)[35]。Dangi等[36]研究發(fā)現(xiàn),山羊在熱應(yīng)激狀態(tài)下HSP70和HSP90的基因與蛋白質(zhì)表達(dá)量均高于非熱應(yīng)激狀態(tài)。本文試驗(yàn)中,7—8月份間鋪膜舍青年奶牛的血清HSP60和HSP70蛋白含量及其基因表達(dá)水平均顯著降低,尤其是HSP70含量降低幅度高達(dá)15.87%。目前關(guān)于動(dòng)物熱應(yīng)激誘導(dǎo)HSP70表達(dá)的文獻(xiàn)報(bào)道很多[37-38]。Arnal等[39]研究指出,HSP70可通過(guò)激活抗氧化酶系統(tǒng)來(lái)減少活性氧的產(chǎn)生,從而保護(hù)機(jī)體免受氧化損傷,這與本研究中抗氧化酶活性的結(jié)果基本吻合。

      4 結(jié) 論

      1)單彩鋼棚舍屋頂鋪設(shè)反光膜有效降低了7-8月份和9-10月份外圍護(hù)結(jié)構(gòu)的內(nèi)表面溫度,中午屋頂內(nèi)表面溫度的降低幅度分別高達(dá)10.48 ℃和8.16 ℃。7-8月份舍溫的降低幅度達(dá)0.87~1.04 ℃(09:30~13:30),且青年奶牛每天處于中度熱應(yīng)激時(shí)間減少了2.08%,呼吸頻率降低了12.51%。

      2)單彩鋼棚舍屋頂鋪設(shè)反光膜提高了7-8月份青年奶牛的抗氧化性能和免疫性能,血清MDA含量降低了15.45%,SOD和T-AOC分別提高了5.71%和10.47%。IL-4血清含量及其mRNA水平顯著上調(diào),而HSP60和HSP70的血清含量及HSP70的mRNA水平顯著下調(diào)。

      3)單彩鋼棚舍屋頂鋪設(shè)反光膜提高了青年奶牛產(chǎn)犢后的泌乳性能,產(chǎn)奶量增加了7.20%,乳蛋白率提高了4.85%。

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      Effects of reflective film on the thermal environment in shed and blood biochemical parameter of growing dairy cows

      Zhao Lichen1, Zhao Xinnian1, Feng Man2, Song Lianjie2, Wang Yanan2, Li Yongliang1, Guo Jianjun2, Gao Yuhong1※

      (1.,,071001,2.,,067000,)

      Dairy cows are suffering from serious heat stress in the shed with a single-color steel roof. In this study,a reflective film was pasted over the floor for better thermal insulation from the roof at ambient temperature. Two cowsheds were simulated with a similar building structure, one of which was reformed by pasting a reflective film over a single-color steel roof (film shed), and another of which was not reformed as a control (control shed). 90 growing dairy cows were raised in each shed. The measurement was performed on the inner surface temperature of the enclosure structure in the cowsheds and the indoor temperature. Moreover, the physiological parameters, antioxidant, immune properties, and production performance of cows were utilized to evaluate the effects of a single-color steel roof covered with the reflective film on the heat stress of cows in the hot season (from July to August) and non-hot season (from September to October). The results were as follows. 1) The inner surface temperature of the roof in the film shed decreased by 10.48 ℃ for the noon period from 12:00 to 13:00, compared with the control shed (<0.01), whereas, the indoor ambient temperature decreased by 0.87 to 1.04 ℃ (<0.05) for the phase from 09:30 to 13:30, during the hot season from July to August. The surface temperature of the roof in the film shed decreased by 8.16 ℃ for the noon phase, compared with the control shed (<0.01) during the non-hot season from September to October. Besides, the duration of cows under moderate heat stress was 2.08% less in the film shed than that in the control shed every day during the period from July to August. By contrast, there was no heat stress in the two experimental sheds during September and October. 2) The respiratory rate of cows in the film shed was 58.33 times per minute, which was 12.51% lower than that in the control shed (<0.01); the lying ratio of cows from 10:00 to 14:00 increased by 7.90% to 18.77% (<0.05) during the period from July to August. After the growing dairy cows calved, the film shed demonstrated an increase of 7.20% in the milk yield (=0.08) and 4.85% in milk protein rate (<0.05) compared with control shed. 3) The concentrations of serum superoxide dismutase and total antioxidant capacity in the film shed increased by 5.71% and 10.47%, respectively (<0.05), and the malondialdehyde concentration was reduced by 15.45% (<0.05) from July to August, compared with the control shed. The serum concentrations of interleukin-4, interleukin-6, immunoglobulin G, and immunoglobulin M in the film shed were higher than those in the control shed (<0.05) during the period from July to August. Particularly, the serum concentration and mRNA expression level of IL-4 increased by 24.78% and 25.43% respectively (<0.01). In addition, the serum concentrations of interleukin-6, immunoglobulin G, and immunoglobulin M in the film shed increased by 9.06%, 18.58%, and 21.23%, respectively, compared with the control shed. The serum concentrations of HSP60 and HSP70 decreased by 14.06% and 15.87% during the hot season, respectively (<0.05), compared with the control shed, and the expression level of HSP70 mRNA also decreased (<0.05). However, there was no significant difference in the parameters between the two sheds during the period from September to October (>0.05). In conclusion, the reformed single-steel roof had a significant heat-insulating effect during the period from July to August, and improved the blood physiological indicators, antioxidant and immune properties of growing dairy cows, which would effectively alleviate heat stress of cows, and improved its lactation performance after calving.

      temperature; cows; humidity; cowsheds; antioxidant property; immune property

      10.11975/j.issn.1002-6819.2022.17.023

      S823

      A

      1002-6819(2022)-17-0214-10

      趙俐辰,趙心念,馮曼,等. 反光膜對(duì)舍內(nèi)溫?zé)岘h(huán)境及青年奶牛血液生化指標(biāo)的影響[J]. 農(nóng)業(yè)工程學(xué)報(bào),2022,38(17):214-223.doi:10.11975/j.issn.1002-6819.2022.17.023 http://www.tcsae.org

      Zhao Lichen, Zhao Xinnian, Feng Man, et al. Effects of reflective film on the thermal environment in shed and blood biochemical parameter of growing dairy cows[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2022, 38(17): 214-223. (in Chinese with English abstract) doi:10.11975/j.issn.1002-6819.2022.17.023 http://www.tcsae.org

      2022-07-27

      2022-08-30

      河北省現(xiàn)代農(nóng)業(yè)產(chǎn)業(yè)技術(shù)體系奶牛創(chuàng)新團(tuán)隊(duì)建設(shè)項(xiàng)目(HBCT2018120202);河北省奶業(yè)振興重大技術(shù)創(chuàng)新專項(xiàng)項(xiàng)目(19226632D)

      趙俐辰,研究方向?yàn)閯?dòng)物營(yíng)養(yǎng)與環(huán)境工程。

      高玉紅,博士,教授,研究方向?yàn)樾笄莪h(huán)境控制和環(huán)境工程。Email:gyhsxs0209@126.com

      中國(guó)工程學(xué)會(huì)會(huì)員:高玉紅(中國(guó)農(nóng)業(yè)工程學(xué)會(huì)畜牧工程分會(huì)理事:E040800011M)

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