EFFECTS OF LEVEL OF DIETARY FIBER FROM WHEAT BRAN ON DIGESTIBILITY OF NUTRIENTS, DIGESTIVE ENZYMES AND PERFORMANCE IN THE EUROPEAN LARGE WHITE AND CHINESE MEI SHAN PIG

Fourteen castrated pigs of the Large White (LW) and Mei Shan (MS) breeds weighing 45-50 kg liveweight were used in a balance trial for the measurement of the apparent digestibility of nutrients and fibrous components supplied by wheat bran in the diet (Exp. 1). Twenty additional animals at the same stage were used to compare the effect of a low and a very high level of fibre originated from wheat and wheat bran, supplying 3.3 and 7.9% of ADF, respectively (Exp. 2). The digestibility of fibrous compounds was determined in both experiments. The body composition and the level of pancreatic and intestinal enzymes at 173 days of age were determined in Exp. 2. The presence of a high or a very high level of fibre depressed the apparent digestibility of all dietary components in animals of both breeds. For an increase of 1 per cent of ADF, the digestibility of energy decreased by 4.8 and 2.8 unit percentage in experiment 1 and 2, respectively, that of nitrogen by 3.3 and 1.6 unit percentage in the same conditions. The apparent digestibility of cellulose (ADF-ADL) or hemicellulose (NDF-ADF) was relatively similar, but it was linearly decreased by an increase in the dietary ADF content. In addition, MS animals utilized better fibrous components only in case of very high levels of dietary ADF and in the presence of high digestible protein sources. Despite a significant increase in the fresh weight of the empty colon in the MS pigs, such data on the digestive tract were not informative. In addition, no difference in the activity of pancreatic enzymes and intestinal disaccharidases including cellobiase observed between breeds and levels of fibre. Daily nitrogen retention which was 14.4 g d-1 for LW pigs was considerably reduced to 10.5 g d-1 for MS; it was also significantly reduced by an increase in the level of dietary fibre in a conventional diet to 8.3 and 5.8 g d-1 for LW and MS, respectively. Mei Shan pigs were also fatter than LW ones and fibrous feeds failed to decrease the fatness of these animals.