LAUSR

There is little information on the fatty acid dynamics of forages under grazing. The objectives of this study were to determine the fatty acid compositions of fall-planted rye (Secale cereale L.) and wheat (Triticum aestivum L.) forages while rotationally grazed by steers (Bos Taurus L.) for seven weeks in the spring and summer in Minnesota, USA. With respect to the total fatty acids in forages, the concentration of α-linolenic acid (C18:3n-3) decreased linearly while the concentration of linoleic acid (C18:2n-6) increased quadratically over the grazing interval. Simultaneously, the omega-6 to omega-3 fatty acid ratio increased quadratically in forages. The fatty acid composition had a greater magnitude of variation in wheat compared to rye over the course of the grazing interval. The omega-6 to omega-3 fatty acid ratio was lower in wheat compared to rye for at least the first five weeks, but was ≤ 0.21 for both forages during the entire grazing interval. Results from this study indicated that forage fatty acid compositions varied based on number of days of the grazing interval and forage species, informing producers of potential grazing schedule adjustments to manage the dietary fatty acid intake of grazing cattle.