Temporal relationship between milk MIR predicted metabolic disorders and lameness events

Lameness is an often occurring consequence of various metabolic disorders, such as sub-acute ruminal acidosis (SARA) or ketosis. Recent research showed that these metabolic disorders can be predicted with reasonable accuracy with mid-infrared (MIR) spectral data. In order to study the potentially complex temporal relationship between MIR predicted metabolic disorders and lameness events over the course of the lactation, data from 3895 cows on 122 farms, representing the Simmental, Brown-Swiss and Holstein breeds. A total of 38316 lameness and 11419 MIR records were collected over a period from July to December 2014 through the Efficient Cow Project. Lactations were subdivided into 30 days lactation stage classes. Milk MIR predicted metabolites such as ketone bodies, acetone, citrates and fatty acids (C18:1cis9), and lameness scores were averaged over animals and these classes. In order to assess the temporal link between occurrences of metabolic disorder and lameness events, correlations were computed between averaged metabolites and lameness scores across the lactation stage classes. Correlations tended to be higher when comparing predicted metabolites with lameness in the three following months, rather than the same one. Results showed differences between breeds, Simmentals showing lower correlations than Holsteins or Brown-Swiss. Especially very early values for milk MIR predicted metabolites (first month), and therefore suspected metabolic disorders, were correlated more strongly to later occurring lameness events in Brown Swiss. In Holsteins, higher correlation between metabolites and lameness were observed during later lactation. In general, given the use of classes, the correlations tended to be unstable. Alternative methods, such as covariance functions, might therefore be useful to get a clearer picture. However these first results seem to support the idea of temporal relationships between metabolic disorders and later lameness events during the
lactation.