Optimal standardized ileal digestible lysine levels in low-protein diets: Effects on performance of lactating sows and their offspring.

> 0.05). A nonlinear fitting of sensitive indicators with linear and quadratic effects was conducted to estimate optimal SID Lys requirements for lactating sow. Breakpoints for 14 d SUN, maximizing piglet benefits (weaning litter weight and individual weight), and sow BW loss were 0.80%, 0.81%, and 0.85% using the broken-line linear model, and 0.86%, 0.90%, and 0.90% using the broken-line quadratic model. In conclusion, the LP diet containing 0.78% SID Lys did not adversely affect sow performance but affected piglet growth performance. Reducing dietary SID Lys in LP diets impaired the growth and development of 21 d suckling piglets, whereas increasing SID Lys and supplementing CAAs (Met, Thr, Trp, and Val) restored performance and mitigates adverse effects. The broken-line linear and quadratic models suggest the optimal range of SID Lys in LP diets for sows is between 0.80% and 0.90%.