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

An experiment was conducted to deter-mine the relationship between in vitro assays to esti-mate 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 vitreous-ness. Six of the 12 sources of corn had similar proxi-mate 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 con-sisted of corn sources with 0.50% Ti02- In total, 504 (12 per pen; 0.039 m2 per bird) Ross x 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 TÌO2, GE, N, CF, and starch content. Ileal digestibil-ity of N (apparent), CF, and starch did not differ (P > 0.05) among sources of corn. Apparent ileal digest-ible 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. [ABSTRACT FROM AUTHOR]