Animal Science Abstract
Effects of graded levels of soya-bean protein on endogenous ileal lysine loss and amino acid digestibility in growing pigs
H. L. Zhang1, S. Y. Qiao1,A, X. J. Chen1, X. Wang1, J. J. Xing1 and Y. L. Yin2
ACorresponding author. E-mail: qiaoshy@mafic.ac.cn
1College of Animal Science and Technology, China Agricultural University, Beijing, No. 2. Yuanmingyuan West Road, Beijing, Post Code 100094, People’s Republic of China2Key Laboratory of Subtropical Agro-ecology, Institute of Subtropical Agriculture, The Chinese Academy of Sciences, Box 10, Changsha 410125, People’s Republic of China
Abstract
This experiment investigated the effects of feeding graded levels of a soya-bean protein product (HP300, Hamlet Protein A/S Company, Denmark) on endogenous ileal lysine loss, apparent ileal amino acid digestibility, standardized true ileal amino acid digestibility determined using the protein-free ( PF) method, and real ileal amino acid digestibility determined using the homoarginine (HA) method. The soya-bean protein product was obtained by purifying and defattening soya bean via a proprietary microbial process that decreased the level of trypsin inhibitors and other anti-nutritional factors in soya bean. Six barrows, with an initial body weight of 37·4 ± 1·3 kg, were surgically fitted with simple T-cannulae at the distal ileum and offered six maize-starch-based diets according to a 6 × 6 Latin-square design. The six diets were formulated to provide 0, 50, 100, 150, 200, or 250 g crude protein (CP) per kg by dietary inclusion of 0, 90, 182, 274, 367 or 460 g/kg of soya-bean protein. Five kg of soya-bean protein product was guanidinated in order to estimate endogenous amino acid flow and real ileal amino acid digestibility. Chromium III oxide (5 g/kg) was included in the non-guanidinated diets while dysprosium chloride (0·1 g/kg) was included in the guanidinated diets as an indigestible marker. The experimental periods lasted 8 days. On day 6 of each period, ileal digesta was collected for 24 h to determine apparent and standardized true ileal amino acid digestibility of the non-guanidinated diets. At 08:00 h on day 8, the pigs were given a single meal of the diets containing guanidinated protein and their ileal digesta was collected for 24 h in order to determine the total HA flow and the real ileal digestibility of lysine. Endogenous ileal lysine flow appeared to follow a sigmoid curve starting at about 370 mg/kg dry matter (DM) intake for pigs given the PF diet and continuing asymptotically to about 750 mg/kg DM intake when the inclusion level of the soya-bean protein product was increased to 182 g/kg (100 g/kg of CP). The endogenous P>0·05) to that of pigs given 90 g/kg soya-bean protein (50 g/kg of P<0·05) as the level of soya-bean protein increased from 90 to 182 g/kg (50 to 100 g/kg of P>0·05). With an increase in soya-bean protein, there was a quadratic increase P<0·01) in the apparent ileal digestibilities for all amino acids except valine and phenylalanine. Standardized true ileal P<0·05) with an increase in soya-bean protein level. However, real ileal amino acid P>0·05) by soya-bean protein in the diet at levels between 90 and 367 g/kg (50 and 200 g/kg of CP). In conclusion, endogenous ileal lysine flow was not constant and was significantly affected by soya-bean protein level. The results of this study suggest that standardized true ileal amino acid digestibility should be measured between 100 and 200 g/kg of CP (182 and 367 g/kg soya-bean protein) while real ileal amino acid digestibility is unaffected by protein levels between 50 and 200 g/kg of CP (90 and 367 g/kg soya-bean protein).
Keywords: amino acids, digestibility, lysine, pigs, soya-bean protein.
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