Epsilon Archive for Student Projects

Abstract

Sub-acute rumen acidosis (SARA) is a problem with major economic importance in dairy production. The definition of SARA is a low pH (< 5.3-5.5) in the rumen during several hours in the day. Due to lack of other confirmatory
clinical sign, SARA is diagnosed by measuring pH of the ruminal fluid. According to the definition continuous measurement of rumen pH is needed to diagnose SARA but until now methods for that purpose only exist for fistulated animals. In recent years, diagnostic tools in the biological field based on wireless telemetric technology have been developed. A magnetoelastic sensor which can swell and shrink in response to different
pH levels was evaluated in this project. The sensor was tested in water, phosphate buffer, VOS buffer, McDougall’s buffer, rumen liquid as well and in vivo in a cannulated cow. This sensor was prepared by casting layers of polymer on a magnetic ribbon, set up this ribbon in a plastic frame and then wrap ping it with magnetic paper. A box like wooden structure was used in case of in vitro which can conserve heat and provide a continuous rumen temperature. The prepared sensor upon application of a magnetic field produced mechanical vibration and thus production of a magnetic flux which can be received by a pickup coil. The measurement system consisted of the magnetoelastic sensor, a coil for excitation and pick up of the sensors resonance frequency, a control unit and a computer for signal processing and evaluation. The signals received from the sensor seemed to be affected by the use of an electric stirrer and also by gas bubbles produced during mixing of acids in buffer. However, this sensor was able to provide specific and repeatable signals in different ionic concentration. The changes in pH level of the rumen liquid were detected within a wide range of pH (from 3 to 10) whereas for the cow a more narrow range in pH (5 to 7) is required.

Due to the too wide range of pH the change in frequency was difficult to calibrate against pH. Future work should be carried out with the aim to find a more appropriate polymer (e.g. peptide based) to increase the signal within the rumen pH range.