Effects of Amino Acid-enriched Ruminally Protected Fatty Acids on Plasma Metabolites, Growth Performance and Carcass Characteristics of Hanwoo Steers

This study was conducted to determine the effects of amino acid-enriched ruminally protected fatty acid (AARPFA) on plasma fatty acids and amino acids, growth performance and carcass characteristics of Korean native steers (Hanwoo) by simultaneous supply of fatty acids and limiting amino acids (methionine and lysine). Eighteen finishing Hanwoo steers, 18 months of age and weighing an average of 459.0 +/- 38.9 kg, were used for studies of the metabolism of plasma fatty acids and amino acids during supplementation of AARPFA. Also, 45 finishing Hanwoo steers, 16 months of age and weighing an average of 408.6 +/- 26.5 kg, were used for growth performance and carcass characteristics during supplemention of AARPFA. There were three treatments which comprised a basal diet supplemented with AARPFA at 0 g (T1), 50 g (T2) or 100 g (T3), respectively. Concentrations of saturated, unsaturated and total fatty acids in plasma were increased in T3 compared with other treatments (p<0.05). Concentrations of methionine and lysine in plasma were linearly increased with increasing levels of AARPFA (p<0.01). Average daily gain, dry matter intake and feed conversion ratio were not different among the treatments. Marbling score measured by ultra-sound scanning was higher in T3 than in T1 at 24 months of age (p<0.05). Rib eye area, back fat thickness, yield index and yield grade score were similar across the treatments. Marbling score and quality grade score were higher in T3 compared with other treatments (p<0.01). Thus, plasma fatty acids, methionine and lysine metabolism were affected by supplementing with 100 g of AARPFA which also had positive effects on marbling score and meat quality grade of finishing Hanwoo steers.