Does the use of distiller's dried grains with solubles (DDGS) in layer diets affect the nutrients digestibility and manure pollution by nitrogen and phosphorous?

The objective of the current study was to examine the effect of the inclusion levels of distiller's dried grains with solubles (DDGS) which partially and fully replaced soybean meal (SBM) in laying hen diets with or without enzyme or vitamin E supplementation on nutrients digestibility and excreted nitrogen and phosphorous. For these purposes, a total of 180 Hisex Brown laying hens at 22 weeks of age were randomly distributed into 15 treatment groups in a 5 × 3 factorial design experiment including five levels of DDGS (0, 5.5, 11, 16.5 and 22% replaced for the same percent of SBM which represents 0, 25, 50, 75 and 100% respectively in the diet) and three levels of feed additives (without, 250 mg enzyme/kg diet or 200 mg vitamin E/kg diet) through 22-42 weeks of age. Results revealed that digestion coefficient values of nutrients including DM, OM, CP, EE, NFE and CF were more preferable in hens fed diets involved 25% DDGS instead of SBM than that of the control diet and other treatment groups. In contrast, hens fed 100% substitution of DDGS caused significant (P ≤ 0.01) decrease in digestibility coefficients of all nutrients. The amount of daily excreted N was decreased in hens fed 25 or 50% DDGS substitution, whilst feeding 75 or 100% DDGS led to an elevation in N excretion. The proportion of excreted phosphorous was statistically (P ≤ 0.01) decreased as the level of DDGS increased. Generally, neither enzyme nor vitamin E supplementation had any significant effect on the studied parameters. It could be concluded that DDGS could be used up to 50% as a replacement of SBM (11% of the diet) without any adverse effects on nutrients digestibility. Laying hen farms using DDGS up to 25 or 50% substituted for SBM in its diets (5.5 or 11% of the diet) will have clearer environment of nitrogen and phosphorous pollution than others whose diets free of DDGS.