The present study was conducted to examine the effect of soybean silage as a crude protein supplement for corn silage in the diet of Hanwoo steers. The first experiment was conducted to evaluate the effect of replacing corn silage with soybean silage at different levels on rumen fermentation characteristics in vitro. Commercially-purchased corn silage was replaced with 0, 4, 8, or 12% of soybean silage. Half gram of the substrate was added to 50 mL of buffer and rumen fluid from Hanwoo cows, and then incubated at 39°C for 0, 3, 6, 12, 24, and 48 h. At 24 h, the pH of the control (corn silage only) was lower (p<0.05) than that of soybeansupplemented silages, and the pH numerically increased along with increasing proportions of soybean silage. Other rumen parameters, including gas production, ammonia nitrogen, and total volatile fatty acids, were variable. However, they tended to increase with increasing proportions of soybean silage. In the second experiment, 60 Hanwoo steers were allocated to one of three dietary treatments, namely, CON (concentrate with Italian ryegrass), CS (concentrate with corn silage), CS4% (concentrate with corn silage and 4% of soybean silage). Animals were offered experimental diets for 110 days during the growing period and then finished with typified beef diets that were commercially available to evaluate the effect of soybean silage on animal performance and meat quality. With the soybean silage, the weight gain and feed efficiency of the animal were more significant than those of the other treatments during the growing period (p<0.05). However, the dietary treatments had little effect on meat quality except for meat color. In conclusion, corn silage mixed with soybean silage even at a lower level provided a greater ruminal environment and animal performances, particularly with increased carcass weight and feed efficiency during growing period.

The soybean [Glycine max (L.) Merr.], an ediblelegume, has a high protein content in both its hay andgrain, so it is often used as a supplement for other foragesthat have a deficient protein concentration. Therefore, thisstudy investigated the forage quality and yield in the caseof mixed planting of soybean and corn. The forage yield andquality were assessed for three cropping patterns: soybeanmono planting, corn mono planting, and mixed planting ofsoybean and corn. For planting, this study used a forage corncultivar, Kwangpyeongok, and three recombinant inbreed lines,W2, W4, and W11, selected from Glycine soja (PI483463)×G. max (Hutcheson). The mixed planting of soybean and cornproduced a higher forage yield than the corn mono cropping.The crude protein and crude fat content were also increasedwith the mixed planting of soybean and corn when comparedwith the corn mono cropping. Some decrease of ADF andNDF, and increase for RFV in mixed planting of soybeanand corn than corn mono cropping. Therefore, the resultsshow that mixed planting of soybean and corn is aneffective cropping system to improve the forage quality.