Ileal starch digestibility of different cereal grains fed to growing pigs

The objective of the present study was to determine, in growing pigs, the ileal starch digestibility and ileal digestible starch content of 8 different genotypes of barley, rye, triticale, and wheat each. Therefore, 4 experiments were conducted with 34 ileally cannulated growing pigs (initial BW of 24 to 32 kg) in total. The experimental diets were formulated to contain 1 of the 8 genotypes of each cereal grain at an inclusion level of 95%. Cereal grains were ground through a 2-mm sieve and were the sole dietary source of starch. All diets were supplemented with plant oil, minerals and vitamins, and titanium dioxide as an indigestible marker. The experiments were arranged either as a row-column design with 8 periods of 6 d each and 9 pigs (for barley and wheat) or according to an 8 x 8 Latin square design with 8 periods of 6 (rye) or 7 d (triticale) and 8 pigs. Experimental periods comprised 4 (barley, rye, and wheat) or 5 d (triticale) for adaptation followed by 2 d for ileal digesta collection. The daily feed intake amounted to 4% of pigs' average BW, corresponding to about 3 times the animals' energy requirement for maintenance (106 kcal of ME [as-fed basis]/kg of metabolic BW). Ileal starch digestibility was different (P < 0.05) within barley and triticale genotypes, with values ranging between 90.1 and 95.0% for barley and between 96.5 and 98.1% for triticale and tended to differ within rye genotypes (P < 0.1). Ileal digestible starch content was different (P < 0.05) within all cereal grains. On average, ileal starch digestibility amounted to 92.7, 95.0, 97.3, and 92.2% for barley, rye, triticale, and wheat, respectively, and was different among cereal grains (P < 0.001). Average ileal digestible starch content was greatest (P < 0.001) in triticale (68.3%, DM basis) followed by wheat (66.1%, DM basis), rye (61.1%, DM basis), and barley (57.6%, DM basis). Differences in ileal starch digestibility and ileal digestible starch content within and among grain genotypes may reflect variations in contents of several fiber fractions such as NDF, ADF, and nonstarch polysaccharides (NSP). For most cereal grains, ileal starch digestibility and ileal digestible starch content decreased (P < 0.05) with increasing contents of soluble, insoluble, and total NSP. In conclusion, in the present study, triticale is superior when compared with the other cereal grains due to its relatively low fiber and high starch content and its high ileal starch digestibility values.