Fatty acids and meat characteristics of different biological types of beef cattle developed under a management-intensive grazing system

Beef steers representing four biological types were evaluated for fatty acid profiles and meat characteristics in muscle tissue developed on grazed forages. Biological types included six large-framed, late maturing, nine medium-framed, late maturing, nine medium-framed, intermediate maturing, and nine medium-framed, early maturing steers. Longissimus dorsi muscles were removed and frozen after 7 days of dry aging. Tenderness and cook loss were similar between biological types. Significant differences (P < 0.05) in fatty acid profiles were found between biological types. The medium-framed, early maturing animals scored highest (P < 0.05) in marbling, had the highest (P < 0.05) concentration of total n-3 fatty acids, and had the lowest n-6/n-3 ratio at 1.03:1. All biological types had a mean n-6/n-3 ratio well below the recommended <4:1 for human cardiovascular health. Under this dietary management system, medium-framed, early maturing beef steers should be considered for producing grass-fed beef based on both carcass merit and fatty acid composition. Beef cattle that reach physiological maturity (i.e. puberty) earlier than their contemporaries should be selected for the production of grassfed beef if fully developed on forages. Those animals have the ability to deposit fat earlier than their later-maturing contemporaries. Additionally, medium-framed beef animals should be selected over larger-framed animals as skeletal frame does not contribute to meat quality but requires more nutritional input for growth and maintenance. This ability to deposit fat exclusively on forage nutrients, without energy or protein supplementation, should be exploited when developing grassfed beef. Fat deposition, particularly intramuscularly (IM), contributes positively to meat quality. Fatty acids, especially the ratio of n-6/n-3, are optimized when beef animals have been fully developed on nutrient-dense forages. Forages must be managed in such a way to capture those nutrients for animal intake and protect the plants for regrowth in a pasture setting.