Ion - mobility spectrometry based electronic nose - a promising tool for the evaluation of metabolic status of dairy cows
Abstract
Ketosis is a cattle illness caused by the lack of energy and can be mostly found around peak lactation. Ketosis causes economic losses due to decreased milk production, impaired fertility and increased risk of displaced abomasums. Ketosis is classified clinically and sub-clinically. Sub-clinical ketosis is more deleterious than clinical ketosis. Ketosis is clinically diagnosed if the milk acetone level in milk sample is more than 50 mg/L. When the acetone level in milk is between 25 - 50 mg/L or the blood beta-hydroxybutyrate (BHBA) is over 1200 micromol/L ketosis status is sub-clinical. However, due to the losses in the milk production, acetone concentration of 14,5 mg/L has been suggested as a threshold value for sub-clinical ketosis (Geishauer et al. 2001). The status of ketosis can be tested in milk by the methods based on the colour changes but they are not precise enough in the case of sub-clinical ketosis. Ion mobility based spectrometry was applied for the assessment of cow's metabolic status by using the MGD-1 gas detector as an electronic nose. Expiration air and milk samples of those cows preliminarily scored as having clinical or sub-clinical ketosis were measured. Measurings were conducted at MTT Agrifood Research Finland, North-Savo, Maaninka. Five cows calved at the turn of the year were chosen for measuring and treated with nutrition imbalance. Also five reference cows were used for measuring. Measuring was carried out during morning feeding, when cows were given concentrated feed. The cow was tied to the feeding station in a way that it could not remove its head from the feeding station. Each cow was measured for approximately one minute and measuring data was collected to a file. Milk and blood samples were collected from the same cows. Milk samples were analysed with the measuring equipment. Ketone concentration was determined as a reference measuring at the Valio milk laboratory. BHBA and acetoacetate were analysed from the blood samples. The control cows showed no signs of ketosis. The scoring was made on the basis of milk acetone measurements. The milk samples measured with MGD-1 gas detector based electronic nose can separate the control cows from the cows with ketosis or sub-clinical ketosis (P<0,01, Mann-Whitney U-Test). This indicates that ion mobility technique used in MGD-1 detector provides a basis for a quality control tool for milk production chain. However, much more research and technical development is needed for the development of commercial system suitable for on-line measurement of ketosis from milk of individual cows.
