Study on the Growth Promoting Effect of Crossbred Buffalo Calves Immunized with DNA Vaccine of Co-expression of Somatostatin and Cortistatin

The purpose of this study was to investigate the growth promoting effect and the safety of the vaccine in crossbred buffalo calves immunized with somatostatin and corticostatin co-expression DNA vaccine.The identified plasmid of pVGS/2SS-2A-S/CST-asd was electroporated into attenuated Salmonella Choleraesuis C500 to construct the co-expression live vector vaccine of somatostatin and corticostatin,and evaluate the effect on the growth performance of the crossbreds buffalo after nasal immunization.Twenty four 2-6 months of age crossbred buffalo calves with similar body weight were randomly divided into 4 groups immunized with the vaccine in low dosage group (TL),middle dosage group (TM),high dosage group (TH) and negative control group (NC).Immunization was performed once a day for 3 consecutive days,and a booster was given 2 weeks late.The results showed that the antibody of SS and CST could be produced on 2 weeks after the primary immunization,and TL group was the best,showing higher antibody level and positive rate.At 7 weeks,the positive rate of experimental group showed a downward trend.The daily gain of each experimental group was higher than that of control group at 2 and 7 weeks after the primary immunization,but there was no significant difference between experimental groups (P>0.05),while the average daily gain of antibody positive group (P) was significantly higher than that of negative group (N) at 2 weeks (P<0.05).The results of related hormones showed that the levels of growth hormone (GH) and insulin growth factor 1 (IGF-1) were higher in experimental groups at 2 and 7 weeks after the primary immunization.In each experimental group,TL group showed the best performance,both extremely significantly higher than that of control group except GH level at 7 weeks after the primary immunization (P<0.01),antibody positive group was also significantly higher than negative group (P<0.05).Cytokine test results showed that the interleukin 4 (IL-4) level in experimental groups at 2 weeks after the primary immunization was higher than that of control group,and the IL-4 level in TL and TM groups was extremely significantly higher than that of control group (P<0.01),especially in TL group.The IL-4 level in TL and TH groups at 7 weeks after the primary immunization was significantly higher than that of control group (P<0.05).At 2 weeks after the primary immunization,the level of immune interferon γ (INF-γ) in control group was extremely significantly higher than that of experimental groups (P<0.01),but at 7 weeks after immunization was significantly lower than that of TL and TH groups (P<0.05).The levels of IL-4 and INF-γ in antibody positive group were significantly higher than that of negative group at 2 and 7 weeks after the primary immunization (P<0.05),respectively,and there was no significant difference among other groups (P>0.05).The levels of blood glucose (GLU),total protein (TP),total cholesterol (CH) and urea nitrogen (BUN) in serum showed that except that the level of total protein in TL group at 2 weeks after the primary immunization was significantly higher than that of control group (P<0.05),there was no significant difference of other indexes among each group (P>0.05).In order to confirm the safety of the vaccine,the genes of water,soil and fecal samples after immunization were amplified,which were not detected in PCR sensitivity range.The results indicated that the vaccine could achieve a good immune effect,make the body produce a significant immune response,and the effect of the low dosage group was the best.The vaccine did not cause adverse effects on the environment.     

Pharmacokinetics, urinary excretion and dosage regimen of levofloxacin following a single intramuscular administration in cross bred calves

The pharmacokinetics and urinary excretion following single intramuscular administration of levofloxacin at a dose of 4 mg/kg was investigated in seven male cross bred calves. Appreciable plasma concentration of levofloxacin (0.38 ± 0.06 µg/ml) was detected at 1 min after injection and the peak plasma level of 3.07 ± 0.08 µg/ml was observed at 1 h. The drug level above MIC₉₀ in plasma was detected up to 12 h after administration. Rapid absorption of the drug was also evident by the high value of the absorption rate constant (2.14 ± 0.24 /h). The overall systemic bioavailability of levofloxacin, after intramuscular administration, was 56.6 ± 12.4%. The high value of AUC (7.66 ± 0.72 mg . h/ml) reflected the vast area of body covered by drug concentration. Extensive distribution of the drug into various body fluids and tissues was noted by the high value of Vd_area (1.02 ± 0.05 l/kg). The high ratio of AUC/MIC (76.6 ± 7.25) obtained in this study indicated excellent clinical and bacteriological efficacy of levofloxacin in calves. The elimination half-life and MRT were 3.67 ± 0.4 h and 5.57 ± 0.51 h, respectively. The total body clearance (Cl_B) was 204.9 ± 22.6 ml/kg/h. On the basis of the pharmacokinetic parameters, a suitable intramuscular dosage regimen for levofloxacin in calves would be 1.5 mg/kg repeated at 12 h intervals.     

Pcr studies on the potential sites for latency of BHV-4 in calves

The aim of the study was to examine various tissues of experimentally infected calves for the BHV-4 genome so as to detect in which cells the virus persists during the latent phase of the infection. The presence of the bovine herpesvirus type 4 genome was detected by a nested PCR in a variety of tissues collected from two susceptible calves experimentally infected 62 days earlier. Mild clinical signs of bronchitis, an elevated body temperature for 2–3 days, and a slightly increased number of blood leukocytes were observed in both inoculated calves. BHV-4 was demonstrated in seven samples from the 12 different parts of the nervous system tested from each calf (29.1%), from the cornea, from lymph nodes near to the inoculation site, from the gallbladder and from the bone marrow. Thus a member of the predominantly lymphotropic Gammaherpesvirinae subfamily was detected in neural tissue and other organs that have never been associated with persistence.     

Serum enzyme changes in newborn calves fed colostrum

In 10 newborn Holstein calves, which were initially bottle-fed on pooled colostrum, there were transient increases in several serum enzymes. Within a few hours, the mean serum gamma-glutamyl transferase (gammaGT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), acid phosphatase (ACP), and lactate dehydrogenase (LDH) activities increased 62.5, 2.4, 2.0, 1.8 and 1.3 fold, respectively. In two other calves given initial feeds of enzyme-free pasteurized milk, there were similar increases in serum enzymes, except serum gammaGT. Correct interpretation of serum enzyme activities in newborn calves must take into account the normal increases which occur after feeding colostrum. Serum gammaGT was the only enzyme to increase markedly as a result of its absorption from colostrum. The other serum enzymes are presumably released from the tissues of the calf. The increased activities of serum CK observed in some newborn calves probably resulted from trauma during birth or increased muscular activity after birth.     

Muscarinic receptor subtypes, β-adrenoceptors and cAMP in the tracheal smooth muscle of conventional and double-muscled calves

The total muscarinic (M₁ + M₂ + M₃) and -adrenergic receptors in the tracheal smooth muscle of conventional and double-muscled calves were identified and characterized with the non-specific antagonists [³H]quinuclidinyl benzilate ([³H]QNB) and [³H]dihydroalprenolol ([³H]DHA) respectively.Although the quantity of -adrenoceptors in double-muscled calves was 25% lower (p<0.05) than in conventional calves (B _max=327±89 fmol/mg protein), adenylate cyclase assays indicated that the basal adenylate cyclase activity and the (–)-isopropylnoradrenaline (ISO)- and sodium fluoride (NaF)-stimulated values were not significantly different between these calves. However, the density of muscarinic receptors in double-muscled calves was 40% higher (p<0.01) than in conventional calves (B _max=2955±625 fmol/mg protein). Subtypes of muscarinic receptors were studied with [³H]telenzepine (M₁-receptors), [³H]AF-DX 384 (M₂-receptors) and [³H]4DAMP (M₁ and M₃-receptors). It was found that in both double-muscled and conventional calves about 40% of the receptors were of the M₃-subtype, the remaining 60% being M₂-receptors.From these results, it is suggested that inflammation of the respiratory tract in double-muscled calves may be complicated by an imbalance between the cholinergic bronchoconstrictor and the -adrenergic bronchodilator components of the autonomic nervous system.     

不同代乳品及饲喂方式对荷斯坦奶公犊生产犊牛白肉影响的研究

为研究代乳粉(主要含乳类制品)液态饲喂和代乳料(主要含植物类饲料等)干喂对荷斯坦奶公犊生产犊牛白肉的影响,试验选用20头健康无病、体重和出生日期相近的荷斯坦奶公犊,随机分为2组,每组10头,进行了120 d的生长育肥试验。Ⅰ组饲喂市售的代乳粉(粗蛋白质22%,粗脂肪16%);Ⅱ组饲喂配制的代乳料(粗蛋白质22%,消化能16 MJ/kg)。结果表明:①Ⅱ组犊牛0~90 d平均日增重高于Ⅰ组犊牛,91~120 d平均日增重显著低于Ⅰ组犊牛(P< 0.05),但两组犊牛0~120 d平均日增重和试验末重均无显著差异(P> 0.05)。②不同代乳品及饲喂方式对奶公犊营养物质表观消化率均无显著影响(P> 0.05)。③Ⅰ组犊牛的胴体重、屠宰率和眼肌面积均显著高于Ⅱ组犊牛(P< 0.05),分别比Ⅱ组高11.88%、11.04%和8.12%,但两组间的胴体产肉率无显著差异(P> 0.05);两组犊牛背最长肌的pH、剪切力、蒸煮损失和肉色均无显著差异(P> 0.05),但Ⅰ组犊牛的失水率比Ⅱ组犊牛高20.83%(P< 0.01);Ⅰ组犊牛背最长肌中粗脂肪含量极显著高于Ⅱ组犊牛(P< 0.01),但两组犊牛背最长肌中水分、粗蛋白质、粗灰分、钙、磷和铁的含量均无显著差异(P> 0.05)。④Ⅱ组犊牛的饲养成本比Ⅰ组降低45.38%。综上所述,饲喂代乳料的犊牛可获得与饲喂代乳粉犊牛相似的生长性能和肉品质,显著降低饲养成本。     

犊牛超数排卵方法的研究

本试验采用不同超排处理方案对不同月龄犊牛(1~6月龄)进行超排处理,以得出犊牛超数排卵的最佳方案、最佳月龄和重复超排的最佳时间间隔。结果表明,超排方案4的超排效果最好,平均采卵数(80.0枚)、平均回收卵数(43.3枚)和平均可用卵数(37.8枚)均显著高于其他4个方案(P<0.05),表明超排方案4比较适合3月龄犊牛的超数排卵;2、3、4、5月龄犊牛应用超排方案4的超排效果较好,差异不显著,平均可用卵数分别为33.5、41.0、34.5、32.8枚,1、6月龄犊牛的超排效果显著差于其他4个月龄组(P<0.05),平均可用卵数分别为10.8、18.3枚,表明超排方案4处理犊牛的最佳月龄为2~5月龄;超排间隔2周组(6.3枚)平均可用卵数效果显著差于间隔3、4和5周组(16.7、23.7、23.0枚)(P<0.05),超排间隔3、4、5周组之间超排效果差异不显著,表明犊牛重复超排处理的最佳时间间隔为3~4周。     

不同蛋白水平对犊牛消化代谢及血清生化指标的影响

 【目的】研究蛋白水平对犊牛生长发育、营养物质消化吸收及血清生化代谢的影响。【方法】选取9头新生荷斯坦公犊牛,分为A、B、C 3组,分别饲喂等能值粗蛋白含量为18%、22%及26%的3种代乳品。分别在犊牛12～20日龄、22～30日龄、32～40日龄、42～50日龄和52～60日龄期间进行五期消化代谢试验。【结果】3组犊牛11～61日龄内各生长指标变化曲线相似,22%组犊牛增重速度比18%、26%组分别高9.75%、24.19%。随日龄增长犊牛对DM的消化率逐渐下降,对EE的消化率略有上升,对日粮氮的消化率有上升趋势;3组犊牛对日粮氮的平均消化率分别为69.39%、75.36%及74.55%。日粮钙磷的消化率和存留率全期内趋于稳定,26%组犊牛对日粮磷的平均消化率为63.83%,显著低于18%组的70.40%及22%组的69.73%。22%组血清TP、ALB、GLOB含量均显著高于其它两组;血清GLU含量以22%组为最高,试验结束时22%组为5.38 mmol•L-1,显著高于18％组的3.71 mmol•L-1及26%组的4.09 mmol•L-1。【结论】蛋白质水平和不同生理阶段影响犊牛生长性能、消化代谢及血清生化指标,22%蛋白含量组犊牛的相关性能优于其它两组。     

白头翁皂苷B4对犊牛生长性能、消化代谢和瘤胃发酵的影响

【目的】通过探究白头翁皂苷B4对犊牛生长性能、消化代谢和瘤胃发酵参数的影响。为新型饲料添加剂的开发提供理论基础。【方法】试验选取60头新生荷斯坦公犊牛,随机分为4组(每组15头),分别饲喂0(C组)、15(A1组)、30(A2组)、45(A3组)mg·d^-1的白头翁皂苷B4。试验周期为56d。在犊牛14、28、42和56日龄晨饲前称量体重,并在28、42和56日龄晨饲后2 h采集瘤胃液,测定瘤胃发酵参数。分别在42和63日龄进行两期消化代谢试验,测定营养物质表观消化率和能氮代谢指标。【结果】(1)白头翁皂苷B4对哺乳期犊牛体重和干物质采食量无显著影响(P>0.05),但犊牛14—28日龄的平均日增重与白头翁皂苷B4呈显著正相关(P<0.05),饲料转化比与添加量呈显著负相关(P<0.05),其中A3组犊牛的平均日增重显著高于C组(P<0.05),饲料转化比显著低于C组(P<0.05)。(2)A3组犊牛7—56日龄和7—14日龄的粪便评分和腹泻率显著低于C组(P<0.05),A2组犊牛15—28日龄的粪便评分和腹泻率显著低于C组(...     

肉牛繁育场哺乳犊牛腹泻探讨

哺乳犊牛腹泻由多种原因造成,是犊牛养殖中相对常见的问题,在发病初期如得不到及时控制将造成严重损失,笔者结合牧场实践与现实情况,重点阐述了肉牛繁育场哺乳犊牛腹泻发病原因,同时分析、总结相关问题,针对性的提出肉牛繁育场哺乳犊牛腹泻管控方案,为行业内养殖者在处理哺乳犊牛腹泻时提供参考依据。