Investigation of Risk Factors of Subclinical Ketosis in Dairy Cows in Central Taiwan Using Ketone Body Assay

• Main Authors: Kuo-Jung Shen, 申國榮
• Other Authors: Chung-Hsi JiuJiu Chou
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/85320070228392015598

碩士 === 國立臺灣大學 === 獸醫學研究所 === 100 === 　　Ketosis is an important metabolic disease in dairy cows during early lactation and is associated with losses in milk production and several other periparturient diseases. Cows are defined subclinical ketosis when their concentration of blood BHBA (β-hydroxybutyrate) was over 1.4 mmol/L. Subclinical and clinical ketosis differ in prevalence, course of development, and clinical findings. Cows were at significantly higher risk of developing clinical ketosis than those cows with their BHBA less than 1.4 mmol/L. Subclinical ketosis in dairy cows can lead to economic losses through decreased milk production, decreased reproductive performance, increased risk of displaced abomasum, and increased risk of clinical ketosis. When subclinical ketosis is diagnosed, the cow can be treated and monitored during the following days. Therefore, determination of BHBA in blood samples is an important tool in the diagnosis of ketosis in dairy cows. We developed an assay system to determine BHBA in our lab. This method is based on the oxidation of BHBA to acetoacetate by the enzyme s-hydroxybutyrate dehydrogenase. During this reaction, an equimolar amount of nicotinamide adenine dinucleotide (NAD+) is reduced to nicotine adenine dinucleotide (NADH). During the oxidation of NADH to NAD+ by diaphorase, WST-1 was reduced to WST-1 formaiton. The WST-1 fromation absorbs light at 450 nm, and the increase in absorbance is directly proportional to the BHBA concentration in the sample. In this study, the BHBA assay described gave a linear standard curve between 0.02~5.0 mmol/L. We evaluated the specificity of our assays with respect to acetoacetone, lactose and glucose. Sensitivity is 3 μmol/L. All specimens were analyzed within the stability periods in within-run and between-run procession. It’s highly precision in our assay. To assess the accuracy of our assay, we added known amounts of BHBA to plasma samples and we got the analytical recovery, 97.6%. 　　A total of 228 Holstein and Jersey cows (under 7 years old) from eight commercial dairy herds in central Taiwan were included in the study. The cows had one to six lactation, with milk yield ranging from 21.0~26.0 kg/day during the study. Sampling was carried out during the winter housing period from October 2011 until December 2011. The samples were taken during 1 week pre parturition and 1~4 weeks post parturition. The analytic measurement (497 measurements) range is given as 0.31~3.73 mmol/L for BHBA. Average incidence rate of subclinical ketosis in dairy herds in central Taiwan is 23%. Ketone body titer in dairy cows, which have occurred subclinical ketosis, of 1~2 weeks and 3~4 weeks post parturition were 1.66 ± 0.75 mmol/L and 1.99 ± 0.81 mmol/L, respectively. It is indicated that during subclinical ketosis occurring in cows, the ketone body titer will gradually increase. If no treatment has been performed, the ketone body titer will go higher. Parturition has been regarded as a risk factor of subclinical ketosis (OR: 15.282, 95% CI: 4.742-49.250). However, breed, farm size and herd density in this study has not been considered as risk factors of subclinical ketosis. In this report, management factors affect disease incidence. Ketone body titer in dairy cows at 1 week prior of parturition in diligent management and idle management farms were 0.78 ± 0.01 and 0.94 ± 0.25 mmol/L, respectively. The titer of 1~2 weeks post parturition increased to 0.92 ± 0.03 and 1.44 ± 0.29 mmol/L in diligent management and idle management farms. A statistically significant difference was found between them (p < 0.05), therefore, type of management factors has been recognized as an important risk factor of subclinical ketosis in Taiwan.