Impact of a protein feeding strategy on performance and lysine utilization efficiency in weaned piglets

Dietary reduction of crude protein (CP) can alleviate post-weaning diarrhea (PWD) in piglets but often limits growth even with crystalline amino acid supplementation. This study evaluated how high- or low-protein diets provided for short (10 d) or long (18 d) duration post-weaning affected growth performance and Lys utilization efficiency. A total of 101 piglets (26-28-d-old; 7.02 ± 0.09 kg) were fed with a high-protein diet (HP; 188 g/kg CP and 12.4 g/kg standardized ileal digestible [SID] Lys) or a low-protein diet (LP; 162 g/kg CP and 10.6 g/kg SID Lys) for 10 or 18 d before transitioning to a common starter diet (179 g/kg CP and 11.8 g/kg SID Lys). Individual feed intake and individual body weight (BW) were continuously monitored using an electronic feeder and weighing station. Individual fecal consistency was assessed on d 6, 10, 14, 18, and 22. The daily SID Lys intake, theoretical SID Lys used for performance, Lys utilization efficiency, and residual SID Lys were calculated or estimated. The effect of protein feeding strategy was analyzed using a mixed model with treatment as a fixed effect and pen as a random effect. Linear and quadratic regressions assessed the relationship of SID Lys intake per metabolic BW (independent variable) with average daily gain (ADG), feed efficiency, Lys utilization efficiency, and residual SID Lys intake (dependent variables) across distinct post-weaning phases. Short-term LP feeding (LP10) did not impair growth, whereas long-term LP feeding (LP18) reduced ADG (P = 0.009) and feed efficiency (P = 0.010) during d 0 to 18 without affecting daily feed intake. Long-term HP feeding (HP18) piglets had higher SID Lys intake than LP18 pigs during d 11 to 18 (P = 0.035) and d 0 to 18 (P = 0.051). Lys utilization efficiency did not differ among treatments within 18 d post-weaning but was lower in HP18 than LP18 during d 19 to 39 and d 0 to 39 (P = 0.002), consistent with residual SID Lys intake. Lys utilization efficiency was positively associated with SID Lys intake per metabolic BW during d 0 to 10, but negatively associated thereafter (P < 0.001). Overall, prolonged feeding of a LP diet compromised growth but enhanced Lys utilization efficiency post-weaning.