Intestinal growth and function of broiler chicks fed sorghum based diets differing in condensed tannin levels

Abstract

The effect of feeding sorghum condensed tannins on intestinal growth, function and histology was investigated in an 8-week broiler growth trial. Four sorghum varieties of different proanthocyanidins (PA) content; DC75 (DC - 2.48 A550nm/g DM) Chirimaugute (CH - 1.68 A550nm/g DM), Brown Tsweta (BT - 0.2 A550nm/g DM), SV2 (SV - 0.07 A550nm/g DM) and maize (MA) were used to formulate four diets each with one sorghum variety (CH, BT and SV) and maize included as the principal energy source. DC75 was used to replace 50 (DC50) and 100% (DC100) w/w maize to form the other two treatment diets. Relative weights of the small intestine differed significantly at 21 days of age. However, the decrease in weight did not correspond to the increase in PA level in a linear manner. Villus height and crypt depth were reduced at seven (7%) and 14 days (15%) in broilers fed DC and CH diets and thereafter was similar to MA and SV fed birds. The liver total and esterified cholesterol was reduced in DC100, DC50 and CH fed birds. Grain sorghum contains other phytochemicals such as policosanols and sterols besides PA which compound the observations in the liver. The effect of age on the severity of local liver lesions was not significant. The DC100 fed chicks showed mild crypt necrosis and/or sub-acute crypt distortion. There was a significant increase in the goblet cell number/mm2 measured in the jejunum of chicks fed CH, DC50 and DC100 diets. Sucrase but not maltase activity was significantly reduced with increased PA content in the 7-, 14- and 21-days age groups. From the results it appears that the dietary PA levels are not limiting factors in the development of the gastrointestinal tract of broiler chicks.

Keywords: Sorghum; condensed tannins; intestinal adaptation; villus height; goblet cell density

South African Journal of Animal Science Vol. 37 (3) 2007: pp.202-214