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Abstract A total of 2,160 mixed-gender pigs [PIC 337 × 1050; initial body weight (BW) = 24.9 ± 0.97 kg) were used in the 120-d study to compare feeding strategies (phase feeding vs complete diet blending) at different SID Lys levels (90 vs 100% of suggested requirement estimates) on finishing pig growth performance, carcass characteristics, and economics. Pens of 27 pigs were assigned to 1 of 4 treatments in a completely randomized block design with barn and initial BW as blocking factors resulting in 20 pens/treatment. The treatments included two feeding programs: a 5-phase feeding strategy at either 90% (Phase-90) or 100% of SID Lys requirement estimates (Phase-100) or blending of complete diets with pre-defined mixing proportions of a low and high SID Lys diet to meet 90 (Blend-90) or 100% (Blend-100) of the SID Lys curve requirement estimates for 23 to 127 kg pigs. Lysine levels were based on PIC 2021 requirement estimates. The 90% SID Lys diets were formulated to contain 4.38, 3.73, 3.06, 2.66 and 2.44 g SID Lys per Mcal NE for phases 1 to 5, respectively. The 100% SID Lys diets were formulated to contain 4.86, 4.15, 3.40, 2.96 and 2.71 g SID Lys per Mcal NE for phases 1 to 5, respectively. Pigs in phase-feeding strategies were fed on a feed budget with 21, 65, 67, 63 and 62 kg per pig for phases 1 to 5, respectively. Final BW and overall average daily gain (ADG; d 0 to 120) were not affected by the feeding strategy nor by diet SID Lys levels. In contrast, overall average daily feed intake (ADFI0 of pigs fed by diet blending was less than those fed by phase feeding (P = 0.002) resulting in increased gain to feed ratio (G:F; P 0.001) for pigs fed by diet blending (table). The SID Lys levels did not influence overall ADFI or G:F. Hot carcass weight, carcass yield, percentage lean, fat depth and loin depth were not affected by the feeding program. Despite the decreased overall ADFI and increased G:F of pigs fed by diet blending, feeding strategy resulted in no significant differences in economic criteria except for reduced feed cost per kg gain at high price scenario (P = 0.049) for diet blending. With low diet cost, the 90% SID Lys level resulted in decreased feed cost per pig and feed cost per kg gain than 100% SID Lys (P 0.001), but differences were not detected in income over feed cost (IOFC). In conclusion, diet blending at either 90 or 100% of the SID Lys requirement estimate reduced ADFI and increased G:F without impacting average daily gain (ADG) or carcass characteristics. At ingredient prices used in this study, feeding strategies at either 90 or 100% SID Lys did not significantly affect IOFC, but feeding 90% of SID Lys recommendation reduced feed cost.
Navales et al. (Wed,) studied this question.