Effects of feeding sodium metabisulfite-treated fruit and vegetable discards to Hanwoo heifers and cows

Objective: Two series of experiments were conducted to determine how the incremental levels of sodium metabisulfite (SMB)-treated fruit and vegetable discards (FVD) in diet of Hanwoo heifers and cows affect their performance and health. Methods: In Exp. 1, 36 Hanwoo heifers were stratified by age (13.3±0.83 mo) and initial body weight (305±19.7 kg), and divided randomly to one of three diets containing 0%, 10%, or 20% SMB-treated FVD (as-fed basis). The experiment lasted 110 d, including 20 d of adaptation. In Exp. 2, 24 multiparous Hanwoo cows were divided into three groups based on age (48.2±2.81 mo) and initial body condition score (2.64±0.33). Cows in each block were assigned randomly to one of three diets containing 0%, 11%, or 22% SMB-treated FVD (as-fed basis). The experiment lasted 80 d, including a 20-d adaptation period. In both experiments, SMB-treated FVD was used as a replacement for wet brewers grain in total mixed ration (TMR). Results: Growing heifers exhibited no differences in their daily feed intake (6.58±0.61 kg/d dry matter [DM]), average daily gain (0.60±0.07 kg/d), and body condition score when they consumed the incremental levels of SMB-treated FVD. Although most blood metabolites were unaffected by treatments, blood urea-N and β-hydroxybutyrate levels decreased linearly as the SMB-treated FVD level increased in TMR. Similar to Exp. 1, minor differences were found in daily feed intake (8.27±0.72 kg DM/d) and body condition score of Hanwoo cows. Most blood metabolites remained unaffected by treatments, but blood urea-N decreased as the SMB-treated FVD level in TMR increased. Conclusion: Our findings suggest that SMB-treated FVD could be safely incorporated into the diet of Hanwoo heifers and cows, potentially improving N-use efficiency in the body while not impairing performance or health.