Study on the Rumen Fermentation, Growth Performance and Carcass Characteristics According to the Supplementation of Lupin Flake in Hanwoo Steers

This study was conducted to determine the rumen fermentation dynamics of lupin flakes and elucidate the effects of lupin flake supplementation on the growth performance, blood metabolites, and carcass characteristics of Hanwoo steers. <italic>In vitro</italic> and <italic>in situ</italic> trials of lupin grains and lupin flakes were conducted using three Hanwoo cows with rumen fistulas. The feeding trial included 40 early-fattening Hanwoo steers randomly divided into four groups: control, T1, T2, and T3. Their formula feed contained 0%, 3%, 6%, and 9% lupin flakes, respectively. <italic>In vitro</italic> rumen pH and ammonia concentrations were lower in the lupin flake group than in the lupin grain group after 6 and 24 h of incubation, respectively (<italic>P</italic>&lt;0.05). Concentrations of propionate, butyrate, and total volatile fatty acids were higher in the lupin flake group than in the lupin grain group after 12 h of incubation (<italic>P</italic>&lt;0.05), as was the crude protein disappearance rate at 9 and 12 h of rumen fermentation (<italic>P</italic>&lt;0.05). Supplementation with lupin flakes did not affect the average daily gain. Compared to that in the control group, dry matter intake was lower in the lupin flake–supplemented groups (<italic>P</italic>&lt;0.05); the feed conversion ratio was lower in T2 and T3 (<italic>P</italic>&lt;0.05); and plasma total protein concentration in 29-month-old steers was lower in T1 and T3 (<italic>P</italic>&lt;0.05). Plasma triglyceride concentration was lower in the lupin flake–supplemented groups than in the control group (<italic>P</italic>&lt;0.05). The incidence rate of yield grade A was higher in T1 and T2 than in the control group; the incidence rate of meat quality 1⁺ grade or higher was highest in T2. The carcass auction price was higher in T2 than in the other groups. Overall, compared to whole lupin grains, lupin flakes seem to more substantially affect rumen ammonia concentrations and crude protein disappearance rate. Additionally, we suggest that supplementation with 6% lupin flake formula feed exerts positive effects on the feed conversion ratio, yield grade, and quality grade of Hanwoo steers.