185 Evaluation of SID lysine to energy ratio based on NRC or National Swine Nutrition Guide on pig performance

The objective of this study was to investigate standardized ileal digestible (SID) Lys to energy ratio based on NRC (2012) or National Swine Nutrition Guide (NSNG, 2010) on wean-to-finish pig growth performance. A total of 243 weaned piglets (BW 6.8 ± 0.9 kg, 18 d old) were blocked by weight and gender and assigned (9 pens/treatment, 9 pigs/pen) to 1 of 3 dietary treatments: NRC1, NRC2, and NSNG. Split-sex feeding was applied with 5 pens of barrows and 4 pens of gilts per treatment. Pigs were fed in a 6-phase (d 1–7, 7–21, 21–42, 42–77, 77–109, and 109–144) feeding program with a common diet from d 1 to 7. The SID Lys:ME ratios (g/Mcal) were, for NRC1, NRC2, and NSNG respectively, 3.672, 3.672, 3.780 (d 7–42); 2.970, 2.970, 3.282 (d 42–77); 2.636, 2.636, 2.925 (d 77–109); and 2.333, 2.333, 2.328 (d 109–144). Concentration of ME was 3.350, 3.685, 3.307 Mcal/kg from d 7 to 42, and 3.300, 3.465, 3.351 from d 42 to 144 for NRC1, NRC2, and NSNG, respectively. Ratios of SID Met, Met + Cys, Thr, or Trp to Lys were based on NRC (2012) for NRC1 and NRC2 and National Swine Nutrition Guide (2010) for NSNG. Pen was the experimental unit. The growth performance data are shown in Table 185. The interaction between gender and dietary treatment was not significant (P > 0.05). Significant differences (P < 0.05) in overall ADFI and feed efficiency were observed between treatments. In conclusion, at a similar level of ME, the NSNG-based SID Lys:ME ratios led to better feed efficiency than the NRC-based ratios, but the NRC-based ratios at a higher level of ME resulted in better feed efficiency compared with the NSNG-based ratios. Note: Means within a row without common upper (P < 0.05) or lower (P < 0.1) case letters differ. Note: Means within a row without common upper (P < 0.05) or lower (P < 0.1) case letters differ.