【作者】 王杰；

【导师】 王振勇；

【作者基本信息】 山东农业大学 ， 兽医（专业学位）， 2023， 硕士

【摘要】 犊牛断奶应激,既会导致犊牛生长发育受阻,又会导致犊牛免疫力降低,而易发感染性疾病,另外,过度断奶应激还影响犊牛成年后的生产性能,导致初配日龄延长,产奶性能下降等。当前规模化奶牛场,对犊牛断奶应激缺乏足够的重视,尚未形成有效预防措施。鉴于此行业背景,本研究通过对某规模化牧场采集的数据进行分析,调查断奶应激对犊牛健康和生长发育的影响及犊牛断奶应激程度的相关影响因素,并研究母牛安抚素对犊牛断奶应激的缓解作用,旨在为牧场犊牛断奶应激的预防提供一定参考。本研究的研究对象为河北某规模化牧场2022年1月～6月出生的1652头犊牛,对其进行现场调查及试验。首先,研究断奶应激对犊牛采食量、腹泻及呼吸系统疾病发病率、腹泻及呼吸系统疾病持续天数、平均日增重及平均运动量的影响;其次,研究犊牛初生重、断奶体重及断奶前15 d内平均日增重三个指标对犊牛断奶应激程度的影响;最后,研究母牛安抚素对断奶应激所致犊牛采食量、平均日增重、腹泻及呼吸系统疾病发病率和持续天数、料肉比及血清中皮质醇、免疫球蛋白、结合珠蛋白、γ-干扰素和白细胞介素-1含量的影响。取得如下研究结果:(1)断奶应激对犊牛健康及生长发育的影响。结果表明,断奶后前4 d,犊牛的采食量呈显著下降趋势,断奶后5 d后采食量开始逐渐上升;断奶后15 d内腹泻及呼吸系统疾病发病率较断奶前15 d内分别增加21.74%和5.71%;断奶后15 d内犊牛腹泻及呼吸系统疾病发病主要集中于断奶后前7d;断奶后15 d内腹泻持续天数比断奶前15 d内腹泻持续天数显著增加1.67 d(P<0.01),断奶后15 d内呼吸系统疾病持续天数比断奶前15 d内呼吸系统疾病持续天数显著增加0.71 d(P<0.05);断奶后15 d内平均日增重较断奶前15 d内显著下降0.18 Kg/d(P<0.05);断奶后15 d内平均运动量较断奶前显著增加6030(P<0.01)。(2)犊牛断奶应激的影响因素。结果表明,随着犊牛初生重、断奶体重及断奶前15 d内平均日增重的增加,犊牛腹泻及呼吸系统疾病发病率均显著下降,表明这三者的增加有助于缓解犊牛的断奶应激程度。(3)母牛安抚素对断奶应激程度的缓解作用。结果表明,两组之间采食量无显著差异(P>0.05),但用药组犊牛的平均日增重显著高于对照组(P<0.05);用药组犊牛的平均运动量、腹泻及呼吸系统疾病发病率和持续时间及料肉比均显著低于对照组(P<0.05);用药组犊牛血清中γ-干扰素及免疫球蛋白的含量显著高于对照组(P<0.01);用药组犊牛血清中皮质醇、结合珠蛋白及白细胞介素-1的含量显著低于对照组(P<0.05),表明母牛安抚素可显著改善断奶应激对犊牛健康及生长发育的危害,有助于缓解犊牛断奶应激。综上所述,规模化奶牛场犊牛断奶应激可造成犊牛采食量和平均日增重显著下降,平均运动量、腹泻及呼吸系统疾病发病率及持续天数显著上升;初生重、断奶前15 d内平均日增重及断奶体重的增加,有助于缓解犊牛断奶应激程度;断奶前1 d使用母牛安抚素可显著缓解犊牛断奶应激。因此,当前牧场可通过增加犊牛断奶前平均日增重、增加犊牛断奶体重、断奶前1 d使用母牛安抚素等措施降低断奶应激对犊牛的不良影响。更多还原

【Abstract】 Weaning stress of calves is involved in decreased growth and development and immunity of calves,contributing to the occurrence of infectious diseases.In addition,excessive weaning stress can affect the adult performance of calves,resulting in prolonged initial mating age and decreased milk production performance.At present,the weaning stress of calves has not been paid enough attention and effective preventive measures have not been formed in large-scale dairy farms.Thus,this study analyzed the data collected from a large-scale pasture to investigate the effects of weaning stress on the health and growth of calves and the related influencing factors of the degree of weaning stress of calves.Furthermore,this study also elucidated the protection effect of cow pacifying hormone on weaning stress of calves,providing some reference for the prevention of weaning stress of calves.In this study,1652 calves born from January to June 2022 were investigated and tested in a scale pasture in Hebei Province.Firstly,the effects of weaning stress on feed intake,incidence of diarrhea and respiratory diseases,duration of diarrhea and respiratory diseases,average daily gain and average exercise of calves were studied.Next,the effects of birth weight,weaning weight and average daily gain during the first 15 days of ablactation on weaning stress of calves were evaluated.Finally,we investigated the effects of cow pacifying hormone on feed intake,average daily gain,incidence and duration of diarrhea and respiratory diseases,ratio of feed to meat,and serum levels of cortisol,immunoglobulin,binding globin,gamma-interferon,and interleukin-1 in weaning stress-induced calves.The results are as follows:(1)Effects of weaning stress on the health and growth of calves.The results showed that the feed intake of calves decreased significantly in the first 4 days after weaning,and gradually increased at 5days after weaning.The incidence of diarrhea and respiratory diseases in 15 days after weaning was 21.74% and 5.71% higher than that in 15 days before weaning.The incidence of diarrhea and respiratory diseases of calves in 15 days after weaning was mainly concentrated in the first7 days after weaning.The duration of diarrhea within 15 days after weaning was significantly increased by 1.67 days compared with 15 days before weaning(P < 0.01),and the duration of respiratory disease within 15 days after weaning was significantly increased by 0.71 days compared with 15 days before weaning(P < 0.05).The average daily gain in 15 days after weaning was significantly decreased by 0.18 Kg/d compared with 15 days before weaning(P< 0.05);The average physical activity in 15 days after weaning was significantly increased by6030 compared with that before weaning(P < 0.01).(2)Influencing factors of weaning stress of calves.The results showed that the incidence of diarrhea and respiratory diseases of calves decreased significantly with the increase of birth weight,weaning weight and average daily gain during the first 15 days of weaning,suggesting that the increase of these factors contributes to alleviating the weaning stress of calves.(3)The protective effects of cow pacifying hormone on weaning stress The results showed that there was no significant difference in feed intake between the two groups(P > 0.05),but the average daily gain of calves in the medication group was significantly increased compared with that in the control group.The average exercise amount,incidence and duration of diarrhea and respiratory diseases and feed/meat ratio of calves in medication group were significantly decreased compared with those in control group(P < 0.05).The levels of γ-interferon and immunoglobulin in serum of calves in medication group were significantly increased compared with those in control group(P < 0.01).The levels of cortisol,binding globin and interleukin-1 in serum of calves in the treated group were significantly decreased compared with those in the control group(P < 0.05),suggesting that cow pacifying hormone could evidently improve the harm of weaning stress on the health and growth of calves and alleviate the weaning stress of calves.In conclusion,weaning stress of calves on scale dairy farms significantly decreased feed intake and average daily gain of calves,and significantly increased average exercise amount,incidence and duration of diarrhea and respiratory diseases.Meanwhile,the increase of birth weight,average daily gain and weaning weight in 15 days before weaning contributes to alleviating the weaning stress of calves.Bovine pacification 1 d before weaning significantly relieved weaning stress of calves.Therefore,the adverse effects of weaning stress on calves can be reduced by increasing the average daily gain of calves before weaning,increasing the weaning weight of calves,and using cow pacifying hormone 1 day before weaning.更多还原