Brigitte Lemay's Masters Defence

This thesis is an investigation on the effects of replacing wheat straw with switchgrass in the ration of lactating Holstein cows on production and health. In two studies, mid-lactation Holstein cows were tested on various dietary rations, and yield, production components, and blood metabolites were measured. In study 1, n=24 cows were assigned a ration containing either switchgrass or straw for a 21-d period in a cross-over design. In study 2, n=12 cows were assigned a ration containing either wheat straw, fall-baled switchgrass or spring-baled switchgrass for 14-d periods in a 3x3 Latin Square Design. Milk production and components, along with performance were largely unaffected by the treatment rations. The results of these studies suggest that there is potential for switchgrass to be used as a replacement for wheat straw, and that fall-baled switchgrass may offer additional benefits.