Exploring the effect of auditory stimuli as environmental enrichment in a Holstein herd using glucocorticoids as biomarker

Health and welfare are inextricably linked within efficient and sustainable dairy production. There are several potential risk factors which may affect the well-being of dairy cows, including chronic stress. Even though environmental enrichment can be used as a tool to decrease the potential stress that cows might experience, it is seldom applied to livestock production systems outside of research purposes. The aim of this study was to explore the effect of auditory stimuli as environmental enrichment in a Holstein herd through the use of glucocorticoid concentrations. Non-invasive methods, namely faecal glucocorticoid metabolites (fGCM) and milk glucocorticoid (mGC) concentrations, were employed as stress-associated biomarkers. Activity level and milk yield formed additional parameters for the study. Nine cows in their second- and third-lactation were divided into three groups (A-C) and through the use of a Latin Square as experimental design, each group was exposed to three treatments, namely constant exposure (CE), limited exposure (LE), and no exposure (NE) to slow classical music. Both faecal and milk samples were analyzed for fGCM and mGC concentrations using respective enzyme immunoassays (EIA). A comparison between generated hormone concentrations indicated that fGCM concentrations were more meaningful in its use as a non-invasive biomarker. Cows exposed to constant music had lower stress-related fGCM concentrations (P = 0.012), as well as higher milk yields (P > 0.0001) and lowered activity levels during the morning activity period (named activity 1) and the evening activity period (named activity 3) (Activity 1: P = 0.005; Activity 3: P = 0.048). During no exposure to music, the cows had higher fGCM concentrations, lower milk production and higher activity levels. These findings indicate that auditory stimuli as a form of environmental enrichment have economic benefits to the producer, by potentially reducing the number of cows needed for profitable production as well as the amount of agricultural land required for production. Environmental enrichment will also assist in improving the way that consumers think about dairy farms and dairy production.