Effect of the Replacement of Wheat Straw by Spent Mushroom Substrate in the Diet of Dairy Ewes during Late Lactation on Milk Production, Composition, Oxidation Stability and Udder Health

The aim of the present study was to investigate the effects of different dietary levels of spent mushroom substrate (SMS) at the expense of wheat straw (WS) on milk characteristics in dairy sheep. Thirty ewes at their final stage of lactation (145 +/- 5 days after parturition) were randomly assigned into three groups; control (C), provided with a diet consisting of concentrates, alfalfa hay and WS, and SMS1 and SMS2, where WS was replaced by SMS at 50 or 100%, respectively. The experiment lasted for 28 days, and milk yield, composition, somatic cell count (SCC) and oxidative stability were monitored weekly, while milk fatty acid and immune cell profile were also determined on day 28. No significant differences were found in produced milk quantity, fat, protein, lactose, total solids non-fat, SCC and fatty acid profile between the experimental groups. However, milk oxidative stability was significantly improved as an effect of SMS (p < 0.001). At the same time, milk polymorphonuclear leukocyte percentage was decreased in SMS2 group (p < 0.05). As indicated, SMS seems to be a promising agro-industrial by-product for ewes' diet that could improve milk oxidative stability, without negatively affecting milk yield, composition and ewe health status, contributing in the context of sustainability, circular economy and protection of natural resources.