Effect of sorghum on performance, digestibility of dietary components and activities of pancreatic and intestinal enzymes in the weaned piglet

Abstract

Six samples of six different varieties of sorghum ( Bianco, Rosso I, Pau, Argence + Rosato, Rosso II and Argor) varying in their tannin content (1.6, 4.3, 2.2, 3.1, 9.2 and 40.1 g kg −1 of catechin equivalents, respectively) were used in diets formulated for piglets weaned at 21 days of age to test their effect on growth and digestibility. In Experiment 1, 18 weanling castrated male and 18 weanling female crossbred Pietrain × Large White pigs were penned individually and randomly assigned in a complete block design to one of the three diets based on maize, Bianco or Rosso I sorghum varieties from 7 to 25 kg live weight. Animals were fed either on maize or only one sorghum diet ( Pau) between 25 and 50 kg live weight and the same control diet from 50 kg to 100 kg live weight. Significant effects on growth performance among diets were only found in the growing phase, when daily weight gain was 510 and 467 g ( P < 0.05) for animals receiving maize and sorghum based diets, respectively. As a consequence a reduction in growth performance of animals fed on sorghum ( P < 0.10) for the overall period was been observed. No residual effect of sorghum tannins was observed on carcass composition. In Experiment 2, thirty weanling castrated males were used to determine total tract (28–35 days of age) and ileal (42–56 days of age) apparent digestibility coefficients of dietary components of four diets containing either maize or sorghum. Total tract apparent digestibility coefficients (TTAD) for energy and nitrogen, respectively, were similar for maize (90.7 and 88.2%) and low tannin sorghum diet ( Argence + Rosato: 90.9 and 86.9%), both being significantly higher than the medium ( Rosso II: 87.9 and 83.7%) and high ( Argor: 86.7 and 81.0%) tannin sorghum varieties. A significant depressive effect of tannins ( P < 0.05) on the ileal apparent digestibility coefficient (IAD) for energy was observed, 85.1, 85.8, 81.9 and 83.2%, and there was also a similar trend for nitrogen, 77.3, 78.3, 74.7 and 75.2%, respectively for the same four diets. Thus TTAD and IAD of energy and nitrogen were affected by tannin levels exceeding 2.5 g kg −1 in the diet. Chymotrypsin ( P < 0.05) and lipase activities measured in the pancreas after slaughter at 56 days of age were increased and trypsin activity was reduced by an increase in tannin content in the diet. In the intestinal mucosa, the activities of maltase and γ-glutamyl transferase were adversely affected by the presence of tannin but peptidases or alkaline phosphatase activities were unchanged. The lower activity of proteolytic enzymes in the pancreas (trypsin) and brush border (γ-glutamyl transferase) could explain the lower digestibility of nitrogen in the small intestine and, consequently, in the total digestive tract.