Evaluation of Phase-Feeding Strategies and Lysine Specifications for Grow-Finish Pigs on Growth Performance and Carcass Characteristics

The objective of this study was to compare phase-feeding strategies for grow-finish pigs using the estimated Lys requirements for optimal growth and feed efficiency compared to a standard strategy. A total of 1,188 pigs (PIC 359×1050, initial BW 28±0.8 kg) were used in a 117-d growth trial with 27 pigs per pen and 11 pens per treatment in a randomized complete block design. Treatments consisted of: MAX, a 4-phase feeding program with Lys levels for maximum growth (1.13, 0.96, 0.82, and 0.77% standardized ileal digestible (SID) Lys in phases 1-4, respectively); STD, a standard 4-phase feeding program for optimal income over feed cost (IOFC; 1.02, 0.87, 0.76, and 0.67% SID Lys in phases 1-4, respectively); STD/MAX, a 4-phase feeding program with standard Lys levels in early finishing and Lys levels for maximum growth in late finishing (1.02, 0.87, 0.82, and 0.77% SID Lys in phases 1-4, respectively); and 2-PHASE, a 2-phase feeding program based on average estimated Lys requirements for maximum growth with 0.96% SID Lys for phases 1-3 and 0.77% SID Lys during phase 4. The 4 phases were from approximately 27-50, 50-72, 72-100, and 100-127 kg BW. Pigs fed the 2-PHASE regimen had increased ADG (P<0.05) compared to pigs fed the STD regimen, and feeding either the MAX or STD/MAX regimen was intermediate. There was no evidence for differences in ADFI, G:F, final BW, or in carcass traits (HCW, yield, backfat, loin depth, and lean percentage). The STD feeding program resulted in the lowest (P<0.001) feed cost per pig and feed cost per kg of gain. Revenue and IOFC were similar across the feeding programs. In conclusion, feeding Lys levels for maximum growth and efficiency in either a 2- or 4-phase feeding program results in the same growth performance and feed cost. Thus, feeding a simpler 2-phase program may have benefits in reducing feed manufacturing costs and increasing overall economic return. Also, this suggests the range in Lys specifications tested herein can be utilized in grow-finish diets without compromising IOFC.

	MAX	STD	STD/MAX	2-PHASE		SEM
d 0 to 117
ADG, kg	0.876ab	0.855b	0.870ab	0.880a		0.006
ADFI, kg	2.29	2.26	2.28	2.29		0.022
G:F	0.382	0.379	0.381	0.385		0.003
HCW, kg	94.2	92.7	94.0	94.6		0.810
Lean, %	57.0	56.6	56.6	56.7		0.222
Feed cost/kg gain, $	0.468a	0.454b	0.464a	0.469a		0.003
IOFC, $/pig	65.08	65.41	65.72	65.42		0.827
abP<0.05