Effect of Tannin on In Vitro Dry Matter and Protein Disappearance in Sorghum Grain¹

The purpose of this investigation was to determine the effect of tannin and added urea on in vitro dry matter disappearance (IVDMD) and in vitro protein disappearance (IVPD) in sorghum ( Sorghum bicolor (L.) Moench) grain. IVDMD of low and high tannin genotypes after 48 hours of fermentation was 72.5 and 46.4% respectively. The addition of urea increased IVDMD to 93.4 and 79.2% for the low and high tannin genotypes. IVPD of low and high tannin genotypes was not affected by urea and averaged 88.2 and 69.6%, respectively. After 96 hours of fermentation the IVDMD of low and high tannin genotypes was 93.8 and 85.8%, respectively, indicating a true difference in digestibiltiy of about 8 percentage units. The major factor limiting the utilization of high tannin sorghum is apparently the availability of protein. Undigestible protein and tannin complex may account for more than half of the difference in IVDMD between low and high tannin genotypes.