Treatment and post-treatment effects of dietary supplementation with safflower oil and linseed oil on milk components and blood metabolites of Canadian Holstein cows

The treatment and residual effects of linseed oil (LSO) and safflower oil (SFO) supplementation on milk and blood metabolites of cows was investigated. Twenty-six cows were grouped according to parity and days in milk and assigned equally to one of two treatments: a control diet + 5%SFO or 5%LSO for 28 days (treatment period, TP). The TP was preceded by a control period of 28 days (all animals on control diet). After treatment, animals were returned to control diet for 28 days (posttreatment period, PTP). Blood and milk samples were collected weekly. Feed intake decreased with LSO and SFO (p <.05), while body weight (BW) increased steadily (p <.0001) throughout. Non-esterified fatty acid (NEFA) and triacylglyceride (TAG) increased (p <.0001) during treatments. Beta-hydroxybutyric acid increased (p <.0001) with SFO only. Milk urea nitrogen (MUN) and fat decreased (p <.0001) with both supplements. NEFA/MUN and milk fat content returned to control levels one week or three weeks after treatment, respectively. TAG did not return to initial concentrations by the end of PTP. The residual effects of feeding LSO or SFO on the physiology of cows were still active up to three weeks after cessation of treatments