挤奶机的系统真空和自动脱杯阈值对奶牛乳房健康的影响

发布时间：2018-01-03 17:24

本文关键词：挤奶机的系统真空和自动脱杯阈值对奶牛乳房健康的影响　出处：《中国农业大学》2017年博士论文　论文类型：学位论文

【摘要】：挤奶机是奶牛场乳房炎控制的关键点之一,其质量和使用状态的好坏关系到奶牛养殖业能否持续健康发展。针对挤奶机在整体设计上缺乏良好的基础理论和在使用过程中系统真空度及自动脱杯阈值缺乏科学设定依据的三大问题,该文构建了挤奶机系统的数学模型,提出了挤奶机系统动态特性的分析方法,分析了真空泵生产能力、系统内部体积以及管道横截面积等因素对挤奶机系统动态变化的影响;研究了挤奶机系统真空度不相同时的挤奶效果,试验以12头高产泌乳牛(单产7.4±0.4t)和12头低产泌乳牛(单产5.7±0.2t)为研究对象,以挤奶量、挤奶时间、平均奶流量、体细胞数(SCC)以及乳头末端壁厚变化率等参数作为挤奶效果评价指标,在系统真空设置在44至48 kPa的范围内,研究了系统真空度对挤奶过程不同阶段的内套真空度和挤奶杯口真空度的影响,量化了系统真空度对挤奶效果评价指标的影响,分析了内套真空度和挤奶杯口真空度与各挤奶效果评价指标的相关性;研究了挤奶机自动脱杯阈值对挤奶效果的影响,以每天两班次挤奶的新产奶牛群为研究对象,利用交叉实验设计的方案,评估了自动脱杯阈值设置(0.2kg/min和0.3kg/min)结合最大套杯时间(7.2min)对乳头末端状况、临床乳房炎、产奶量以及挤奶时间的影响。研究表明,应用键合图技术构建的挤奶机系统数学模型很好的描述了挤奶机系统的动态特征。挤奶机系统动力学研究表明,挤奶机系统内部的周期性扰动随系统内部体积的增加而减弱,不规律扰动则随真空泵生产能力的增加而减弱。当系统内部的周期性扰动的频率接近系统固有频率时,系统的动态变化随管道横截面积的减小而减弱。针对系统真空度的试验研究表明,当系统真空度从44 kPa增加至48 kPa时,奶牛在峰值流量期间和过挤奶期间,内套真空度增加率分别为4.9%(P0.001)和10.8%(P0.001),挤奶杯口真空度增加率分别为373.8%(P0.001)和53.7%(P0.001)。系统真空度从44 kPa增加至48 kPa,挤奶量、挤奶时间以及平均奶流量均没有显著差异,但log10SCC(P0.05)和乳头末端壁厚变化率(P0.05)均显著增加。结果表明,试验挤奶机用44 kPa的系统真空度比用46或48 kPa等更高的系统真空度的效果更好,挤奶特性保持较好,泌乳牛感染乳房炎的风险更低。自动脱杯阈值设置联合最大套杯时间控制的试验研究表明,当自动脱杯阈值从0.2kg/min增加至0.3kg/min时,挤后残奶量从0.12kg增加至0.23kg(P0.001),挤奶时间从6.82min减小至6.13min(P0.001),日挤奶量和体细胞数均无显著性差异(P0.05),临床乳房炎发病率也没有明显差异。结果表明,将自动脱杯阈值从0.2kg/min提高至0.3kg/min后,牛群乳头末端总体评分结果和基于长度、乳区位置以及单头牛乳头健康水平分类评分结果均优于自动脱杯阈值提高前的结果。
[Abstract]:Milking machine is one of the key points of field mastitis control in dairy cattle, the quality and the use of state is directly related to the sustained and healthy development of dairy industry. Due to the lack of a good theory and in the process of using the vacuum system and automatic cup threshold lack three big problems of science set on the basis of the milking machine in the overall design, the this paper constructs the mathematical model of the system of the milking machine, put forward the dynamic characteristic analysis of milking machine system, analyzes the influence of vacuum pump capacity, system internal volume and cross-sectional area of pipe and other factors on the dynamic system of milking machine change; research system of vacuum milking machine milking effect are not the same, to test 12 the head of high yield dairy cows (yield 7.4 + 0.4t) and 12 (low lactating cows yield 5.7 + 0.2T) as the research object, the milking, milking time, average milk flow, somatic cell count (SCC) and nipple At the end of the wall thickness of the rate of change of parameters such as milking effect evaluation index system in a vacuum, set in the range of 44 to 48 kPa, study the system of vacuum on the milking process at different stages within the set of vacuum and vacuum milking cup, to quantify the effects of the system of the vacuum milking effect evaluation index. Analysis of relationship between inner sleeve vacuum and vacuum milking cup evaluation and various milk effect indexes of milking machine; automatic stripping cup threshold effect on the effect of milking, milking time to two new dairy cow group as the research object, using cross experiment design, evaluation of automatic threshold setting (off the cup 0.2kg/min and 0.3kg/min) with the maximum time (7.2min) of the cup at the end of the nipple, clinical mastitis, milk production and milking time. The results show that the application of bonding mathematical system constructed by the technique of milking machine mould drawing Type is a good description of the dynamic characteristics of the system. The study on the dynamical system of milking machine milking machine milking machine system show that the periodic internal disturbance with the increase of system internal volume decreases, with the increase of the disturbance of vacuum pump capacity decreases. When the period of internal disturbance frequency is close to the natural system the frequency, the dynamic changes in the system decreases with decreasing pipe cross-sectional area. According to the experimental study on vacuum system show that when the vacuum system increased from 44 kPa to 48 kPa, during the peak flow during and after the cows in the milking, inner vacuum increase rate were 4.9% (P0.001) and 10.8% (P0.001), milking cup vacuum increase rate was 373.8% (P0.001) and 53.7% (P0.001). The degree of vacuum is increased from 44 kPa to 48 kPa, milking, milking time and average milk flow had no significant difference, but the log10SCC (P0.05 ) and teat end wall thickness change rate (P0.05) increased significantly. The results showed that the better effect of the vacuum system 44 kPa vacuum system compared with 46 or 48 kPa higher test for milking machines, milking characteristics to maintain good, dairy cow mastitis infection risk lower. Automatic and cup joint maximum threshold cup set time control test on set show that when automatically cup threshold increased from 0.2kg/min to 0.3kg/min, the residual amount of milk after extrusion increased from 0.12kg to 0.23kg (P0.001), milking time decreased from 6.82min to 6.13min (P0.001), there were no significant differences in daily milk production and somatic cell count (P0.05). Clinical mastitis incidence had no obvious difference. The results show that the automatic cup threshold increased from 0.2kg/min to 0.3kg/min, the end result and the overall score of cattle nipple based on the length, location and single cow milk nipple health level scoring results The result is better than the automatic cup thresholding.

【学位授予单位】：中国农业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S817.21

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