The amount of soybean meal in the each diet was adjusted to equalize the CP content. Extra amino acids were incorporated into diets based on the SID AA concentration derived from Exp. 1. All diets (Table 3) met or exceeded recommendations for required nutrients (NRC, 1998).
The piglets were housed in pens with half cement floor and half woven mesh floor. All pigs had free access to feed and water throughout the 28 d experiment. The temperature of the pig barn was controlled between 23 and 28◦C, and relative humidity was controlled at 60–70%. Pigs and feed were weighed at the beginning and end to determine average daily gain(ADG), average daily feed intake (ADFI) and feed conversion efficiency (G:F). Piglets were observed for clinical signs of diarrhea every day, and a scoring system was applied to indicate the presence and severity of diarrhea as following: 1 = hard feces; 2 = slightly soft feces; 3 = soft, partially formed feces; 4 = loose, semiliquid feces; and 5 = watery, mucous-like feces.