Effects of salseed (Shorea robusta) tannins, restricted feed intake and age on relative pancreas weight and activity of digestive enzymes in male broilers

Abstract

Three groups of 15 male broilers (2 weeks old) were employed as experimental animals. Two isonitrogenous and isoenergetic diets, one containing salseed meal (SSM) and the other containing barley (control) as a major energy source were fed to the birds for 4 weeks. These diets were fed ad libitum to the SSM and control groups. In addition, a pair-fed group was fed the control diet at the same intake level as SSM birds. Blood, digesta, mucosa and pancreas samples were collected by killing the birds on days 8, 18 and 28 (five birds per group per slaughter date). Birds fed the ad libitum control diet utilised their feed more efficiently than the SSM and pair-fed birds. Pancreas weight of SSM and pair-fed birds were 3.9 and 2.9 g kg−1 liveweight, respectively, compared with 2.4 g kg−1 liveweight of those fed ad libitum, indicating that the presence of tannin in the diet and limited feeding induced an enlargement of the pancreas. However, age had a negative linear effect on the relative weight of the pancreas. Unlike trypsin (EC 3.4.21.4), the activity of α-amylase (EC 3.2.1.1) of the birds fed the SSM diet was much lower (81 units g−1 pancreatic tissue) than that of birds fed the tannin-free diet ad libitum (178 units g−1 pancreatic tissue). Activities of trypsin and α-amylase were markedly lower, 3837 and 186 units g−1 dry chyme, respectively, in the jejunal digesta of the birds fed the SSM diet but the linear relationship between the activities of these enzymes and pancreatic tryptic activity was significant. Lower feed intake also caused a reduction in α-amylase activity compared with ad libitum feeding, the activities being 873 and 1365 units g−1 dry chyme, respectively. Dipeptidase (EC 3.4.13.11) and disaccharidase activities were significantly depressed in duodenal and jejunal mucosa of the tannin fed birds, the only exception being maltase (EC 3.2.1.20) activity in the jejunal mucosa, which remained unaffected. The linear effect resulted in a gradual increase in the activities of these enzymes with age. The only effect for enterokinase (EC 3.4.21.9) was the higher activity (532 units g−1 mucosa) in the duodenal mucosa of the SSM birds than in birds fed the control diet ad libitum (416 units g−1). Concentrations of thyroxine were not affected by treatment or age. The interactions between treatment and time in all instances were non-significant.