Effect of crude protein content on growth performance and carcass characteristics of late-fattening Hanwoo steers

초록

Hanwoo is a unique breed of cattle in Korea, and is mainly raised to produce beef. Various efforts are being made to reduce the cost of raising ruminants and to shorten the breeding period in various ways to reduce methane and manure produced by ruminants. Among them, a method of improving beef productivity and shortening the breeding period by adjusting the protein content of cocentrate feed is being reviewed.This study investigated the effects of crude protein (CP) content of concentrate feed (CF) on rumen fermentation, growth performance, and carcass characteristics of late- fattening Hanwoo steers. In vitro and in situ experiments were conducted using three Hanwoo cows (423.0 +/- 44.8 kg) equipped with rumen fistulas. The experimental diets were classified into three categories based on CP content: CF-I, CF-II, and CF-III containing 15.5, 16.5, and 17% CP, respectively. A total of 24 late-fattening Hanwoo steers (619.3 +/- 65.7 kg) were randomly assigned to either a control group fed CF-I or a treatment group fed CF-II. The disappearance rates of ruminal dry matter were higher in CF-II and CF-III than in CF-I after 48 h of incubation (p<0.01). CP disappearance rates were higher in CF-I compared to CF-II and CF-III throughout the incubation period (p<0.05). Propionate concentrations after 48 h of incubation were higher in CF-II and CF-III than in CF-I (p<0.01). Concentrations of total volatile fatty acids (VFAs) at 24 h of incubation were higher in CF-II and CF-III than in CF-I (p<0.05), with a trend of increasing VFAs concentration at 48h correlating with higher CP content in CF. Although average daily gain was higher in the treatment group than in the control group, the difference was not significant. Roughage intake was higher in the treatment group than in the control group (p<0.05). Plasma glucose concentration was higher in the control group (p<0.05), whereas total protein concentration was higher in the treatment group (p<0.05). Carcass weight and rib eye area were slightly, but not significantly, higher in the treatment group than in the control group. Marbling score did not differ significantly between groups. While the CP content in CF influenced CP disappearance rates, VFAs concentrations, and plasma total protein concentrations, increasing CP content alone, without considering the energy content of CF, appears unwarranted given the environmental implications and productivity outcomes for late-fattening Hanwoo steers.

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