Elimination of ceftiofur hydrochloride residue in postpartum cows' milk after intramammary infusing at dry-off

The purpose of this study was to investigate the residue elimination of ceftiofur hydrochloride in milk of postpartum cows after intramammary infusing at dry-off. An ultra-high performance liquid chromatography-tandem mass spectrometry （UPLC-MS/ MS） method was developed and validated to detect ceftiofur hydrochloride residue in milk. Through preprocessing, ceftiofur hydrochloride was derivatized into a more stable compound dedfuroyl ceftiofur acetamide （DCA） for further analysis. The linear range of DCA was 0.1 to 50 μg kg-1. Average recoveries of DCA were 82.52-105.86％. The intra-day and interday coefficients of variation （CV） were 2.95-9.82 and 6.41-7.43％, respectively. The limit of detection （LOD） and limit of quantitation （LOQ） scores were 0.05 and 0.1 μg kg-1, respectively. These parameters showed this method was reliable and valid. Twelve cows were administrated 10 mL ceftiofur hydrochloride by intramammary infusion （corresponding to 500 mg ceftiofur） to each udder after the last milking before the dry-off period. Milk was collected from each udder of cow at 12, 24, 36, 48, 60 and 72 h after calving and was mixed for each time point and each cow, then subjected to UPLC-MS/MS analysis. The results showed, the DCA concentrations in all milk samples were less than LOQ and the maximum residue limit （MRL） 100 μg kg-1, which suggested the withdrawal time of ceftiofur hydrochloride intramammary infusion used for preventing and curing mastitis in dry cows was 0 day. The study provided guidance for the clinical applications of ceftiofur hydrochloride intramammary infusion （dry cow）.

Accuracy comparison of dry matter intake prediction models evaluated by a feeding trial of lactating dairy cows fed two total mixed rations with different forage source

Dry matter intake （DMI） prediction models of NRC （2001）, Fox et aL （2004） and Fuentes-Pila et aL （2003） were targeted in the present study, and the objective was to evaluate their prediction accuracy with feeding trial data of 32 lactating Holstein cows fed two total mixed rations with different forage source. Thirty-two cows were randomly assigned to one of two total mixed ration groups： a ration containing a mixed forage （MF） of 3.7% Chinese wildrye, 28.4% alfalfa hay and 26.5% corn silage diet and another ration containing 33.8% corn stover （CS） as unique forage source. The actual DMI was greater in MF group than in CS group （P=0.064）. The NRC model to predict DMI resulted in the lowest root mean square prediction error for both MF and CS groups （1.09 kg d-1 vs. 1.28 kg d-1） and the highest accuracy and precision based on concordance correlation coefficient for both MF and CS diet （0.89 vs. 0.87）. Except the NRC model, the other two models presented mean and linear biases in both MF and CS diets when prediction residuals were plotted against predicted DMI values （P〈0.001）. The DMI variation in MF was caused by week of lactation （55.6%）, milk yield （13.9%）, milk fat percentage （7.1%） and dietary neutral detergent fiber （13.3%）, while the variation in CS was caused by week of lactation （50.9%）, live body weight （28.2%）, milk yield （8.4%）, milk fat percentage （5.2%） and dietary neutral detergent fibre （3.8%）. In a brief, the NRC model to predict DMI is comparatively acceptable for lactating dairy cows fed two total mixed rations with different forage source.

Effects of Dietary Supplement of Fermented Tomato Pomace on Dry Matter Intake and Nutrient Apparent Digestibility of Dairy Cows

This study was carried out to evaluate the effects of replacing corn silage with ensiled tomato pomace on dry matter intake and apparent digestibility of diets.Eight close up dry Holstein cows were used in 2 × 2 Latin square design.The animals were fed control(0% tomato pomace silage) and experimental(10% corn silage replaced by tomato pomace silage) diets.The result showed that dry matter intake in experimental group was 9.77 ± 0.44 kg/d,which was significantly higher than in control group(p < 0.05).Dry matter digestibility in experimental and control group was 73.9% and 70.2%,respectively,but there was no difference between two groups(p > 0.05).The substitution of tomato pomace silage in diet was associated with an increase of dry matter intake,dietary supplement of ensiled tomato pomace without any adverse effect on their health performance.

Effect of reduced energy density of close-up diets on dry matter intake,lactation performance and energy balance in multiparous Holstein cows

Energy intake prepartum is critically important to health, milk performance, and profitability of dairy cows. The objective of this study was to determine the effect of reduced energy density of dose-up diets on dry matter intake （DMI）, lactation performance and energy balance （EB） in multiparous Holstein cows which were housed in a free-stall barn and fed for ad libitum intake. Thirty-nine dry cows were blocked and assigned randomly to three groups fed a high energy density diet [HD, n = 13; 6.8 MJ of net energy for lactation （NEL）/kg; 14.0% crude protein （CP） ], or a middle energy density diet （MD, n = 13; 6.2 MJ NEh/kg; 14.0% CP）, or a low energy density diet （LD, n = 13; 5.4 MJ NEh/kg; 14.0% CP） from d 21 before expected day of calving. After parturition, all cows were fed the same lactation diet to d 70 in milk （DIM）. The DMI and NEE intake prepartum were decreased by the reduced energy density diets （P 〈 0.05）. The LD group consumed 1.3 last 24 h before calving. The milk yield and the postpartum kg/d （DM） more diet compared with HD group in the DMI were increased by the reduced energy density diet prepartum （P 〈 0.05）. The changes in BCS and BW prepartum and postpartum were not affected by prepartum diets HD group had higher milk fat content and lower lactose content compared with LD group during the first 3 wk of lactation （P 〈 0.05）. The energy consumption for HD, MD and LD groups were 149.8%, 126.2% and 101.1 % of their calculated energy requirements prepartum （P 〈 0.05）, and 72.7%, 73.1% and 7.5.2% during the first 4 wk postpartum, respectively. In conclusion, the low energy density prepartum diet was effective in controlling NF_L intake prepartum, and was beneficial in increasing DMI and milk yield, and alleviating negative EB postpartum.

Effects of Dietary Energy Density in the Dry Period on the Production Performance and Metabolism of Dairy Cows

Thirty healthy Holstein dairy cows in the dry period were randomly divided into three groups and fed diets with different net energy for lactation (group A: 1.2 Mcal/kg DM, group B: 1.3 Mcal/kg DM, and group C: 1.4 Mcal/kg DM) for 8 weeks prepartum. Thereafter, dairy cows were fed a diet of the same formulation (1.66 Mcal/kg DM) for 12 weeks postpartum. The effects of different dietary energy densities in the dry period on postpartum performance and metabolic parameters of dairy cows were observed. Milk yield was reduced by 14.5% in the low-energy diet group;however, there were no differences in milk composition between the three groups. Postpartum plasma β-hydroxybutyrate, non-esterified fatty acid, growth hormone, and glucagon levels were significantly decreased whereas leptin and neuropeptide levels were elevated in the low-energy diet group. Moreover, body fat mobilization was attenuated, and the decline in postpartum body condition was reduced in the low-energy diet group, thus effectively reducing the postpartum negative energy balance.

干乳期奶牛隐性乳腺炎主要致病菌的分离、鉴定及2种抗菌药物的体外抗菌效果评价

[目的]对新疆维吾尔自治区奶牛隐性乳腺炎常见致病菌进行分离、鉴定,评价头孢洛宁和利福昔明对临床分离菌株的体外抗菌效果。[方法]采用兰州隐性乳腺炎诊断液对新疆维吾尔自治区昌吉回族自治州某奶牛养殖场的干乳期奶牛进行诊断;利用平板划线法及细菌16S rDNA序列分析法对采集的74份乳样进行细菌分离及种属鉴定;应用微量肉汤稀释法测定头孢洛宁和利福昔明对致病菌临床分离株的最低抑菌浓度(MIC)以及最低杀菌浓度(MBC)。[结果]从74份乳样中共分离、鉴定致病菌9种、103株,其中,金黄色葡萄球菌35株,占总菌株数量的33.98%;大肠杆菌24株,占总菌株数量的23.30%;产色葡萄球菌15株,占总菌株数量的14.56%;模仿葡萄球菌(10株)、表皮葡萄球菌(6株)、屎肠球菌(5株)、溶血性葡萄球菌(4株)、地衣芽孢杆菌(3株)和腐生葡萄球菌(1株)的数量分别占总菌株数量的9.70%、5.83%、4.85%、3.88%、2.91%、0.97%。体外抗菌试验结果显示,头孢洛宁对金黄色葡萄球菌、大肠杆菌、产色葡萄球菌、溶血性葡萄球菌、表皮葡萄球菌、腐生葡萄球菌、屎肠球菌、模仿葡萄球菌和地衣芽孢杆菌的MIC分别为0.12、3.91、0.98、0.06、0.98、0.98、3.91、0.06、0.49μg/mL,MBC分别为0.24、7.81、1.95、0.12、1.95、1.95、7.81、0.24、1.95μg/mL;利福昔明对金黄色葡萄球菌、大肠杆菌、产色葡萄球菌、溶血性葡萄球菌、表皮葡萄球菌、腐生葡萄球菌、屎肠球菌、模仿葡萄球菌和地衣芽孢杆菌的MIC分别为0.20、6.25、1.56、0.78、1.56、1.56、12.50、0.20、0.20μg/mL,MBC分别为0.78、12.50、3.13、1.56、3.13、3.13、12.50、0.78、1.56μg/mL。[结论]引起该养殖场干乳期奶牛隐性乳腺炎的主要致病菌为金黄色葡萄球菌、大肠杆菌、产色葡萄球菌;头孢洛宁和利福昔明对临床分离的致病菌株均有良好的抑菌效果。

云南保山市干热河谷种养循环母牛养殖模式研究

[目的]研究干热河谷“种养结合”生态循环利用母牛养殖模式,提高养殖效益、加强环境保护和增加土地综合利用率。[方法]以云南省保山市2个干热河谷区域的6个养殖户为试验研究对象,每年在2000 m^(2)土地上种植一季玉米、两季蔬菜,再配套种植667 m^(2)王草,每户养殖能繁母牛3头,通过对单独种植效益与种养结合效益进行对比分析,确定适合该区域种养循环母牛养殖的最佳模式。[结果]利用好2000 m^(2)土地,种植两季扁豆、一季玉米可产鲜豆7.26 t、豆秸12.06 t、全株玉米11.37 t,配套种植667 m^(2)王草,年产鲜草34.8 t,满足饲养3头母牛及所产2.5头犊牛的粗饲料需求;年产生30 t鲜粪作有机肥还田。年出售鲜豆收益2.19万元,出售半岁犊牛收益1.75万元,达到种养结合循环利用,增加种养效益。[结论]该种养循环养殖模式适合当地的种植业与肉牛养殖业融合发展,值得推广。

硫酸头孢喹肟乳房注入剂中头孢喹肟含量HPLC通用性测定方法的建立

建立了适用于国内硫酸头孢喹肟乳房注入剂(泌乳期和干乳期)中头孢喹肟含量测定的HPLC通用性方法。采用与《中国兽药典》硫酸头孢喹肟原料含量测定一致的高效色谱条件,使用有机溶剂破乳后加入流动相超声的提取方法,保证了方法的一致性和适用性。方法验证结果显示,本方法专属性较强,准确度较高,重复性和耐用性良好,适用于对国内硫酸头孢喹肟乳房注入剂的含量测定,被收载入2020年版《中国兽药典》。

Productive Performance of Double-Muscled Piemontese Culled Cows in Finishing Period

The aims of the study were to evaluate productive performances and environmental impact of double-muscled Piemontese culled cows. In two trials, 39 Piemontese culled cows aged from 46 to 176 mon were fattened using diets commonly applied in farm conditions. The animals were weighed at the beginning and end of the trials. Concentrate and hay intake were recorded daily. After slaughtering, meat, fat and bone yields were recorded and dressing percentage was calculated. The backward linear regression model was employed for statistical analysis. Results showed average body weight （ABW） of cows as （556.97± 55.99） kg and relatively low dry matter intake （DMI） [（9.17± 0.35） kg d^-1] during the fattening period. The ratio between DMI and ABW, i.e., ratio between intake and weight （RIW）, （1.66±0.18）% was negatively influenced by initial body weight （IBW） and duration of finishing period （D）, but age had no effect on RIW. Average daily gain （ADG） was relatively low [（0.55 ±0.21） kg d^-1, and was negatively correlated with IBW and D, which implied that lower IBW and shorter D could have higher ADG and vice versa. The dressing percentage （DP） was （59.80± 1.83）% and the carcass red meat yield （MY） was （75.17±3.10）%. Nevertheless, N efficiency was very low [（4.35 ± 1.76）%], which must be considered in relation to environmental protection so both animal requirements and a well balanced diet need more attention. In conclusion when Piemontese cows will be culled and fattened, IBW and D should be considered carefully in order to get a reasonable ADG and N efficiency to guarantee productive benefits and environmental protection at the same time.

干奶期奶牛乳房炎防控

乳房炎是影响奶牛健康、牛奶产量及品质、造成牧场经济损失最严重的疾病之一。约2个月的干奶期是防治奶牛乳房炎最关键的时期。本文基于干奶期的乳腺变化,分析干奶期乳房炎高发原因,提出全群及选择性干奶治疗、乳头末端保护方法、营养及卫生方面的饲养管理方法,为防控奶牛乳房炎、提高牛群生产表现及牧场经济效益提供科学参考。

解淀粉芽孢杆菌对奶牛瘤胃干物质消化率、发酵参数及代谢物的影响

本试验旨在研究解淀粉芽孢杆菌对奶牛瘤胃干物质消化率、发酵参数和代谢物的影响。试验1:选择6头胎次(2~3胎)、体重[(662±57)kg]、泌乳天数[(160±22)d]、产奶量[(36.1±3.8)kg/d]相近的安装永久性瘘管的奶牛,随机分为3组,每组2头。采用3×3拉丁方设计进行试验,每组分别补饲0(对照组)、5×109、5×1010CFU/d解淀粉芽孢杆菌。试验期为3期,每期13 d,其中预试期10 d,正试期3 d,在正试期开始时用尼龙袋法测定奶牛瘤胃干物质消化率。试验2:选用30头胎次[(2.5±0.3)胎]、初始体重[(559.2±37.4)kg]、产奶量[(35.2±1.5)kg/d]、泌乳天数[(99±2)d]相近的奶牛,随机分为3组,每组10头。3组分别补饲0(对照组)、5×109、5×1010CFU/d解淀粉芽孢杆菌,预试期10 d,正试期42 d。正试期最后1 d采集奶牛瘤胃液,测定奶牛瘤胃发酵参数以及代谢物。结果显示:与对照组相比,1)补饲5×1010CFU/d解淀粉芽孢杆菌在12、24、36、48、72 h时均可显著提高奶牛瘤胃干物质消化率(P<0.05),补饲5×109CFU/d解淀粉芽孢杆菌在36和48 h时可显著提高奶牛瘤胃干物质消化率(P<0.05);2)补饲5×109CFU/d解淀粉芽孢杆菌可以显著提高奶牛瘤胃中异丁酸、丁酸、异戊酸、戊酸、总挥发性脂肪酸和微生物蛋白含量(P<0.05),补饲5×1010CFU/d解淀粉芽孢杆菌可以显著提高奶牛瘤胃中异丁酸和异戊酸含量,显著降低乙酸/丙酸(P<0.05),补饲5×109、5×1010CFU/d解淀粉芽孢杆菌对奶牛瘤胃pH、氨态氮含量没有显著影响(P>0.05);3)检测发现11个差异代谢物相关的代谢通路,富集差异显著的代谢通路为抗坏血酸和藻酸盐代谢(P<0.05)。综上所述,解淀粉芽孢杆菌可以通过影响瘤胃代谢物含量,改善瘤胃发酵功能,提高奶牛瘤胃干物质消化率。综合分析认为,奶牛补饲5×109CFU/d解淀粉芽孢杆菌效果较佳。

基于Fluent流场模拟的半干式连续厌氧发酵反应器的设计及中试试验

为实现干清粪便的无害化处理,提高干清粪便的厌氧发酵效率,设计了一款300 m^(3)适合干清粪便的半干式连续厌氧发酵反应器。介绍了半干式连续厌氧反应器的基本构造与工作原理,通过对发酵罐体的结构参数,主要装置部件等设计计算,利用有限元分析进行强度的校核,并利用Fluent流场模拟软件对物料运动状态进行仿真,确定了厌氧发酵反应器结构参数,并进行中试试验。试验结果表明:半干式连续厌氧反应器可在工作过程中维持稳定的工作环境,并且能够迅速将发酵原料进行厌氧消化反应,能够维持平均日产气量在410.6 m^(3),容积产气率达1.37 m^(3)·m^(-3)d^(-1)。针对畜禽干清粪便厌氧发酵来说,半干式连续厌氧发酵更为适合,并且能够维持较高的产气效率,沼气工程整体运行稳定,工作性能可靠。

选择性干奶期治疗在奶牛场中的应用与关键点控制

奶牛乳房炎是造成奶牛场经济损失最严重的疾病之一,干奶期是治疗奶牛乳房炎的关键时期,干奶期奶牛饲养管理及健康状况将直接影响下一个泌乳期的牛奶品质、产量及奶牛场的经济效益。本文综合阐述了选择性干奶治疗在欧洲、美国等全球奶业发达国家及地区奶牛场中的应用情况,并分析了影响选择性干奶期治疗的管理因素,针对干奶前、干奶期和干奶后期分析了不同阶段的管理操作要点,以期为指导奶牛场实际生产提供参考依据。

增氧和施有机肥对土壤肥效及水稻生长的影响

研究土壤增氧条件下施加绿肥(紫云英)和施加农家肥(干牛粪)对水稻生长和产量的影响。于水稻生长过程中不同时期采集处理组土壤样品,分析其碱解氮含量、速效磷含量和速效钾含量的变化;于水稻成熟后测定各处理组水稻的分蘖数、叶面积指数和产量等农艺性状指标。结果表明:增氧处理能够促进有机肥肥效元素的释放,提高土壤有效态肥效元素含量;增氧条件下,施加绿肥和农家肥均可促进水稻的分蘖生长,OAF(增氧施绿肥)和OCF(增氧施农家肥)处理的总分蘖数分别为51.34和50.16,对照组总分蘖数为36.93;增氧施农家肥处理比单施农家肥处理组的叶面积指数显著提高,增氧施绿肥处理与不增氧施绿肥处理组叶面积指数的差异无统计学意义;增氧施加有机肥处理组水稻的稻穗长度、穗结实粒数、每株谷粒质量均显著大于单施有机肥处理组,大于对照组。增氧与施有机肥相结合可有效提高土壤的肥效,促进作物生长。

新疆荷斯坦干奶牛与泌乳牛四季CO_2 24h排放量变化的研究

【目的】试验在密闭的牛舍内,对干乳牛与泌乳牛分别测定分析CO2的浓度变化趋势和排放量,为我国节能减排、调控反刍动物温室气体提供基础理论依据。【方法】试验于2011年7月至2012年7月在同一栋牛舍内对20头干奶牛和20头泌乳牛分别进行了四季的CO2排放量测定,每种牛在每个季节的季初、季中、季末测定三次,每次测定24 h。【结果】干奶牛春、夏、秋、冬四个季节的CO2排放量分别约为293.06、308.97、283.21和270.93 kg。泌乳牛春、夏、秋、冬四个季节的CO2排放量分别约为330.45、335.63、322.22和308.33kg。干奶牛一年的CO2排放量约为1 135.5 kg。泌乳牛一年的CO2排放量约为1 314.4 kg。【结论】四季温度的变化对奶牛排放CO2有一定的影响。奶牛CO2的排放量与奶牛的采食量呈正相关。

同一日粮下泌乳牦牛与干奶牦牛消化代谢能力的比较研究

在同一日粮条件下，对泌乳牦牛和干奶牦牛的消化代谢能力进行了比较研究。结果表明，在泌乳牦牛和干奶牦牛体内，日粮消化率间无明显差异（Ｐ＞０．０５），能量代谢率间差异极显著（Ｐ＜０．０１）；蛋白质代谢在干奶牦牛体内为正平衡，而在泌乳牦牛体内为负平衡；在干奶牦牛体内，钙、磷代谢均为负平衡，而在泌乳牦牛体内，钙为正平衡，磷为负平衡。

硫酸头孢喹肟乳房注入剂治疗干乳期奶牛乳房炎的研究

为研究硫酸头孢喹肟乳房注入剂对干乳期奶牛乳房炎的预防与治疗效果,试验选择100头临近干乳期的奶牛,随机分成5组进行临床疗效观察,其中I、II、III组分别给予高、中、低剂量的硫酸头孢喹肟乳房注入剂（300、150、75 mg）治疗;IV组给予对照药物氨苄西林钠＋氯唑西林钠乳房注入剂4.5 g（氨苄西林0.25 g＋氯唑西林0.5 g）/支治疗;V组为空白对照组。间隔3周,各组随机选择10头奶牛以相同剂量追加一次用药。试验结果显示,高、中剂量硫酸头孢喹肟乳房注入剂治疗干乳期奶牛乳房炎的头、乳区清除率均为75%~100%,头、乳区新增感染率分别为0~16%、0~7%;1次用药和2次用药对治疗奶牛乳房炎效果无显著性差异（P〉0.05）。综合比较后认为,每个乳区单次注入1支（3 g∶150 mg）硫酸头孢喹肟乳房注入剂效果更好,能显著降低乳房内链球菌、金黄色葡萄球菌、大肠杆菌等的细菌感染率（P〈0.01）,并能有效预防和治疗干乳期奶牛乳房炎。

硫酸头孢喹肟乳房注入剂(干乳期)对奶牛安全性的研究

【目的】了解硫酸头孢喹肟乳房注入剂(干乳期)对健康奶牛的正常体温、日产奶量、奶中体细胞数和乳房内菌群的影响。【方法】选用初产和经产健康泌乳期奶牛各6头,所选奶牛在试验前30日内未全身性或乳房内给予任何抗生素,奶牛正常饲养管理,日粮和饮水中不含有任何抗菌药物。给药前1和0日统计记录各试验奶牛的直肠温度、日产奶量(早、中、晚3次产奶量的加和)、检测每个乳区采集奶样的体细胞数,并对给药前0日的奶样进行病原菌分离鉴定。4个乳区分别单次给予硫酸头孢喹肟乳房注入剂(干乳期)。给药后的第1、3、5、7、10天分别统计记录每头奶牛的日产奶量,给药后的第12 h、3、5、7、10天分别采集奶样进行体细胞检测,同时检查直肠温度;给药后的第10天,采集奶样进行病原菌分离鉴定。比较奶牛用药前后直肠温度、日产奶量、牛奶体细胞数和奶中病原菌的变化。整个试验期间连续观察给药奶牛是否出现红、肿、热、痛等临床症状。【结果】给药前1天、0天和最后一次给药后的第1、3、5、7、10天,试验奶牛的日产奶量平均值分别为28.8、27.7、28.1、28.7、28.8、29.2和29.6 kg,卡方检验显示无显著性差异(P>0.05);各时间点采集的奶中体细胞数大都维持在30—50万个/m L之间;各时间点测得的奶牛直肠温度平均值分别为38.3、38.4、38.3、38.3、38.3、38.2和38.3℃,无显著性差异(P>0.05);病原菌检测结果显示,在给药前0日采集的奶样中,分离到大肠杆菌8株、链球菌5株和葡萄球菌7株,给药后第10天采集的奶样中大肠杆菌、链球菌和葡萄球菌各分离到1株,明显减少,且没有增加新的病原菌。【结论】硫酸头孢喹肟乳房注入剂(干乳期)对奶牛正常体温、产奶量和奶中体细胞数等没有不良影响,该制剂用于奶牛是安全的。

奶牛常用饲料干物质和蛋白质瘤胃降解特性及小肠消化率研究

选用装有瘤胃瘘管和十二指肠瘘管成年荷斯坦奶牛3头,采用尼龙袋法测定奶牛常用饲料干物质(DM)和粗蛋白质(CP)瘤胃降解参数和小肠消化率。结果表明,DM瘤胃降解率由高到低依次为:麦麸皮、苜蓿、豆粕、DDGS、干啤酒糟、米糠、胡麻饼、全株玉米青贮、羊草、白酒糟;CP瘤胃降解率由高到低依次为:麦麸皮、苜蓿、干啤酒糟、DDGS、豆粕、米糠、胡麻饼、全株玉米青贮、羊草、白酒糟。DM小肠消化率由高到低依次为:豆粕、胡麻饼、DDGS、米糠、麦麸皮、白酒糟、干啤酒糟、全株玉米青贮、苜蓿、羊草。CP小肠消化率由高到低依次为:豆粕、胡麻饼、DDGS、米糠、麦麸皮、干啤酒糟、全株玉米青贮、白酒糟、苜蓿、羊草。试验表明,不同饲料瘤胃降解特性不同,为小肠提供各种可吸收蛋白质潜力也不同。

用表达人溶菌酶基因的重组质粒防治干乳期奶牛乳腺炎

将人溶菌酶(human lysozyme,hLYZ)cDNA插入由pcDNA3改造而成的pcDNAK表达载体,用获得的重组载体pcDNAKLYZ转染COS-1细胞,经免疫荧光试验证明能进行正确表达。将重组载体注射于哺乳母鼠,取其乳汁进行溶菌酶活性测定,结果显示,分泌在乳汁中的重组hLYZ高达139mg/L。根据乳汁体细胞检测结果,选择健康奶牛和乳腺炎阳性奶牛,分别在干奶时和产犊前2周2次注射重组质粒pcDNAKLYZ,注射途径为乳腺基部穿刺,注射剂量为300μg/乳区,于产犊后1个月采集奶样进行体细胞检测,结果显示,对前一泌乳期发生的奶牛乳腺炎的治愈率为91.5%,对下一泌乳期奶牛乳腺炎的预防有效率至少为96.97%。由此认为,构建的表达hLYZ基因的重组表达质粒,可以替代抗菌素类油乳剂用于干乳期乳腺炎的防治。