228 President Oral Presentation Pick: Milk biomarkers for determining the incidence of sub-acute ruminal acidosis

Abstract

Abstract In order to test the validity of milk amyloid A (MAA) as a biomarker for inflammation and subacute ruminal acidosis (SARA), 320 milk samples from 24 commercial dairy farms in Quebec were tested for milk amyloid A using a commercial kit. These farms were divided into low risk of SARA farms and high risk of SARA farms according to the proportions of short chain and polyunsaturated fatty acids content in the bulk tank of the farms. It was assumed that farms at risk of SARA had a lower proportion of short chain and a higher proportion of polyunsaturated fatty acids compared to farms that were not at risk of SARA. Farms were also blocked in groups of two farms by geographical location and management. Each block included an at-risk and a not-at-risk farm. On each farm, 7 early- to mid-lactation and 7 mid- to late-lactation cows were randomly selected for MAA analysis. Cows with a somatic cell count (SCC) of over 200,000 in pooled milk samples were not included. Data were analyzed using SAS Proc. Mixed with Stage of lactation and Risk of SARA as fixed factors, and Block as a random factor. The model also included somatic cell counts (SCC) and parity as a covariates. The concentrations of MAA ranged from non-detectable, i.e. below 0.1 ug/ml, to 3267.9 ug/ml with an average of 336.28 ug/ml.The effects of Block, Stage of lactation, and Risk of SARA on MAA were not significant. However, SCC and parity were significantly (P < 0.01) correlated (P < .001) with MAA with correlation coefficients of 0.34 and 0.26, respectively. The results show that measurement of MAA may be a suitable biomarker for subclinical inflammations such as subclinical mastitis, but not for the Risk of SARA.