Impact of dried distillers grains with solubles (DDGS) and diet formulation method on dry matter, calcium, and phosphorus retention and excretion in nursery pigs

Phosphorus (P) is an expensive component in swine diets, and dietary P levels above the pig's requirement can result in excess P excreted in manure and potential environmental concerns. Consequently, utilization of dietary P by pigs must be optimized in order to minimize diet cost and P excretion in manure. Phosphorus and calcium (Ca) balance was evaluated in nursery pigs fed a control maize–soybean meal (M–SBM) diet formulated on a total P (TP) basis, and four experimental diets containing maize dried distillers grains with solubles (DDGS; 100 or 200g/kg) formulated on either a TP or available P (AP) basis. Barrow pigs (n=39, initial body weight=10.37±0.37kg) were randomly assigned to one of five diets for a 7d adaptation period followed by a 5d period of total, separate collection of both urine and feces. Compared to the M–SBM diet, dry matter (DM) digestibility coefficients were reduced in pigs fed diets containing 100 or 200g/kg DDGS by approximately 0.02 and 0.04 units, respectively (P<0.01). Feed and total P intake were similar among pigs fed control and DDGS diets, but P intake was lower (P<0.01) for pigs fed diets formulated on an AP compared to TP basis. Fecal P concentration was reduced (P<0.01) when diets contained DDGS compared to the M–SBM diet, and when DDGS diets were formulated on an AP basis compared to a TP basis. Total P excretion, retention, and apparent total tract digestibility coefficients were not affected by diet formulation method (FM) or level of DDGS inclusion (P>0.05). Calcium intake tended to be higher (P=0.06), and fecal Ca concentration and retention were higher (P<0.05) for pigs fed the M–SBM diet compared with those fed the DDGS diets. Feeding the 200g/kg DDGS diets tended to increase (P=0.08) fecal Ca excretion, and reduced (P<0.05) Ca retention, retention coefficient, and apparent total tract digestibility compared to feeding the 100g/kg DDGS diets. There were no significant effects of FM or DDGS×FM for Ca intake, retention, excretion, or apparent total tract digestibility. These results indicate that increasing dietary DDGS inclusion levels for nursery pigs decreases DM digestibility and fecal P concentration, but does not affect P excretion, retention, or digestibility. Formulating DDGS diets (100 or 200g/kg) on a TP or AP basis had no effect on P digestibility or total excretion, but total dietary P content is reduced when diets are formulated on an AP basis.