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Interestingly, a nutritional survey of commercially available GFB published by our group highlighted important differences among beef from grass-finishing systems [21]. The n-6:n-3 ratio varied from 1.8:1 to as high as 28.3:1 and some GFB was devoid of β-carotene. These differences were hypothesized to be due to a wide variety of feeding practices that were reflected in the nutritional profile of beef [21]. Feeding fresh forages to cattle usually results in the most beneficial nutritional profile of beef [19,21]. However, producers may rely on conserved forages and other supplemental feeds when fresh grass is not available [30]. Unfortunately, conserved forages made by drying (hay) or fermentation (baleage) often display lower nutritional quality compared to fresh forages with lower concentrations of antioxidants and phenolic compounds [31,32]. The processing of fresh forages into conserved feeds results in oxidation of PUFAs and an increase in palmitic acid [33,34]. These changes in the nutritional profile of feeds modify FA metabolism in the rumen, resulting in variations in the FA content of beef [35,36]. Although not allowed by the American Grassfed Association [26], soybean hulls are also used as supplemental feed by some producers in the U.S. [19,21]. The effects of feeding soybean hulls to cattle remain controversial in the literature. Some studies found no differences in CLA, trans vaccenic acid (TVA), n-3 PUFAs, and the n-6:n-3 ratio among cattle fed soybean hulls or fresh forage in the finishing phase [20,21]. On the other hand, another study reported that cattle supplemented with soybean hulls had more total fat, less n-3 PUFAs, and a higher n-6:n-3 ratio compared to cattle fed only fescue [37].

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