Determination and Comparison of Amino Acids Digestibility of Nine Sorghum Grain Varieties, Corn, Wheat and Barley in Poultry

ABSTRACT: This study was conducted to determine profile and amino acid (AA) digestibility values for different grain sorghum cultivars (GSC), using the true metabolizable energy (TME) assay. So nine SG varieties along with corn, wheat and barley were planted at the same condition and after seed harvesting, the grains were analyzed for proximate analysis, AA profile and tannin content. AA digestibility was determined by using adult Hy-line seacectomized rooster. The results showed that the amounts of AAs for nine SG varieties, especially those are the limiting AAs for poultry, are considered to vary significantly. Among SG varieties, the No.4 & 5 for most essential amino acids were higher than the other varieties, except for Threonine which No 2 & 7 were placed before two last varieties. Also for Lysine and Tryptophan SG 4 was placed in the third and SG 5 in the sixth category, respectively. The highest standard deviation belonged to Glutamic acid (SD=0.32), SG 5 with 3.27% and SG 3 with 2.35% had the highest and the lowest Glutamic acid, respectively. SG varieties compared to the other grains ( corn, wheat and barley) were rich in most AAs. All essential AAs for corn was lower than SG varieties, wheat and barley, except two SG varieties had lower Lysine and Cystine than corn. The first and the second limiting AAs for SG varieties were Methionine (0.198%) and Cystine (0.228%), respectively. For corn Methionine (0.117%) and tryptophane (0.137%), for wheat tryptophane (0.120%) and Methionine (0.176%) and for barley Methionine (0.165%) and Histidine (0.187%), were the first and the second limiting AAs, respectively. Apparent AA digestibility (AAAD) for low tannin sorghum (LTS), medium tannin sorghum (MTS) and high tannin sorghum (HTS) was 77.64, 43.03, and 35.83 percent, respectively, compared to corn (68.10%), wheat (73.71%) and barley (53.28%), (P 0.05). True AA digestibility (TAAD) of LTS (93.73%) corn (91.92%) and wheat (91.30%) was the highest whereas, corresponding value for MTS (61.72%) and HTS (52.04%) was significantly lower (P 0.05). The correlation between tannin and digestibility of all of the AAs was negative and significant (r 0.78, P 0.001). However, the digestibility of proline was the most affected by tannin, which was 98.55% for LTS, and 26.13% for HTS (r 0.96, P 0.001). Results of the present study indicate that profile and AAs digestibility of GSC are different and are not in agreement with standard tables. So it is necessary to determine AAs profile and their digestibility of feedstuff produce in Iran.