The effects of tannins on nutrient utilisation in the White Pekin duck

Author： King D. Fan M.Z. Ejeta G. Asem E.K. Adeola O.

ISSN： 1466-1799

Source： British Poultry Science, Vol.41, Iss.5, 2000-12, pp. : 630-639

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Abstract

1. Two experiments were conducted to determine the effects of tannins on nutrient utilisation in the White Pekin duck.2. Experiment 1 was a rapid nutrient balance assay to determine the nitrogen (N) retention and metabolisable energy (ME) of maize, low-tannin sorghum (P-954063) (Sorghum bicolor (L). Moench) and high-tannin sorghum (IS-4225) cultivars for ducks. The assay lasted 120 h, with an initial 24 h food-deprivation period, a 48 h excreta collection period for endogenous losses and a 48 h excreta collection period for ingredient losses. The true metabolisable energy (TME_n) content was lower (P<0.05) in the high-tannin sorghum cultivar (13.85 MJ/kg) than the maize (14.94 MJ/kg) and the low-tannin sorghum cultivar (14.39 MJ/kg). True N retention was lower ( P <0.05) for the high-tannin sorghum (0.24 g) than for maize (1.33 g) and low-tannin sorghum (1.31 g).3. In experiment 2, the brush-border membrane vesicles technique was used to determine whether tannic acid caused inhibition of L-threonine transport across duck intestinal brush-border membrane. The brushborder membrane vesicles were mixed with tannic acid solutions (pH 7.4) to give gradient tannic acid concentrations of 0, 0.05, 0.10, 0.25, 0.50, 1.00 and 2.50%. As a fraction of the control (no tannic acid), the maximal inhibition of L-threonine transport (I_max) under the sodium-gradient condition was 77.10% (P<0.05). Under the sodium-free condition, the maximal inhibition of L-threonine transport (I_max) was 45.15% (P<0.05).4. These results demonstrated that nutrient utilisation in the White Pekin duck was lower from the hightannin sorghum cultivar than from the low-tannin sorghum cultivar. The results also suggested that the antinutritive effects of tannins in foodstuffs are due partly to their inhibitory action on intestinal brushborder bound amino acid transporter proteins.