Abstract
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.
Highlights
The demand for organic animal products is increasing [1,2], which is partially driven by consumer interest in the health benefits of meat and milk from animals that consumed primarily forages [3].Saturated fatty acids dominate the fatty acid compositions of beef and milk
Concentrations of α-linolenic acid in the fatty acids of forages decreased during the grazing interval, while palmitic and linoleic acids increased (Table 2)
For the results of the current study, the percentage change in fatty acid compositions for rye forages are similar to the results reported in previous studies, but the percentage change in fatty acid compositions for wheat forages are much greater than previous reports
Summary
The demand for organic animal products is increasing [1,2], which is partially driven by consumer interest in the health benefits of meat and milk from animals that consumed primarily forages [3].Saturated fatty acids dominate the fatty acid compositions of beef and milk. Beef and milk have the potential to be sources of unsaturated fatty acids that are important for human health, such as omega-3 (n-3) fatty acids and conjugated linoleic acid (CLA) [4,5,6,7]. Previous research established that these particular fatty acids (i.e., n-3 and CLA) found in beef and milk have a positive relationship with the proportion of fresh forages in cattle diets, which improves (i.e., lowers) the omega-6:omega-3. Fresh forages are innately a major part of organic cattle diets, which can lead to improved fatty acid profiles in the resultant beef and milk products [12,13]
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