Effects of corn source on the relationship between in vitro assays and ileal nutrient digestibility

An experiment was conducted to determine the relationship between in vitro assays to estimate quality and ileal nutrient and energy digestibility of various corn sources. Twelve samples of corn were analyzed for gross energy (GE), N, moisture, crude fat (CF), salt-soluble protein content (SSP), and vitreousness. Six of the 12 sources of corn had similar proximate composition but ranged in pairs as having low, moderate, or high quality based on protein solubility that varied from 25.7 to 49.2%. Experimental diets consisted of corn sources with 0.50% TiO2. In total, 504 (12 per pen; 0.039 m2 per bird) Ross×Ross 708 male broiler chicks were randomly distributed to 42 pens (7 replicates per treatment) at 1 d of age. Broilers were fed common starter and grower diets from 1 to 27 d of age and experimental diets from 28 to 30 d of age. At 30 d of age, 8 birds per cage were euthanized for digesta collection from 4 to 30 cm proximal to the ileocecal junction. Feed and digesta were analyzed for TiO2, GE, N, CF, and starch content. Ileal digestibility of N (apparent), CF, and starch did not differ (P>0.05) among sources of corn. Apparent ileal digestible energy (IDE) of the 6 corns averaged 3,323 kcal/kg. Salt-soluble protein concentration was correlated with IDE among the corns (r=0.5; P<0.001). Ileal N and fat digestibility were correlated with IDE (r=0.4 and 0.3, respectively; P<0.05). Apparent MEn ranged from 3,262 to 3,342 kcal/kg and was correlated with SSP (r=0.8; P<0.001) and IDE (r=0.36; P<0.05). These results indicated that sources of corn with similar proximate composition may vary in their digestible energy content, and in such a situation, SSP may be used to differentiate those with wide-ranging IDE or AMEn. However, further research is required to investigate the relationship between SSP and growth performance of broilers.