Apparent and true digestibility of amino acids in high tannin sorghum and low tannin sorghum cultivars

The apparent and true amino acid digestibilities of high tannin sorghum (HTS) and low tannin sorghum (LTS) were determined using adult cockerels (30 weeks of age). About 24 adult White Leghorn cockerels were used in the present study. The tannin content of low tannin sorghum was 0.07% and that of high tannin sorghum was 1.85%. The first group of birds (8n) was fed with high tannin sorghum and the second group was fed with low tannin sorghum individually as per Farrell's “Rapid ME” method. The third group of birds was precision fed with nitrogen free diet. The excreta of each cockerel were oven dried individually at 80oC for 24h and stored at −24oC until further analysis. The apparent digestibilities of almost all the 15 amino acids studied were significantly higher (p<0.01 to 0.001) in low tannin sorghum as compared to high tannin sorghum. The difference in digestibility varied from 4 per cent to 21.62 per cent. The maximum difference was observed in cystine and histidine digestibilities (20.22 and 21.62 per cent respectively). The difference was minimal in aspartic acid digestibility. The true digestibilities of amino acids also followed the same trend. The amino acid digestibility of LTS was significantly (p<0.001) higher in comparison to HTS. The difference in digestibility ranged from 13.17 per cent to 35.05 per cent. The maximum difference was observed in cystine and histidine digestibilities (35.05 and 33.82 per cent respectively). The present observations revealed that the high tannin content of HTS contributed to the lower amino acid digestibility values.