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The tryptophan:lysine requirement of grow-finish pigs
Twelve hundred grow-finish pigs (PIC 337X1050) were evaluated to determine the optimum Trp:Lys ratio for gain and feed conversion. The study was conducted in three phases: 23-41 kg, 55–77 kg, and 98–114 kg. Pigs were blocked by gender and weight starting at 23 kg and randomly assigned within block to one of six treatments (14, 16, 18, 20, 22, 24 SID Trp:Lys ratio) with 13 pens per treatment. Blocks either had 24 or 25 pigs per pen. Pigs were returned to a common diet that maintained a Trp:Lys ratio of 18 between each trial phase. The first phase diet consisted of corn/soybean meal/dried distiller’s grains with solubles and was formulated to 2549 kcal/kg NE. The other two phases consisted of corn/soybean meal and were formulated to 2666 and 2692 kcal/kg NE respectively. In all phases, soybean meal and fat was held constant and feed grade Trp was added to alter the Trp:Lys ratio. The SID Lys content was formulated 0.05% lower than the expected requirement for the heaviest weight of each phase across the study and all other nutrients met or exceeded the NRC requirements. Data were analyzed using Proc Mixed with linear and quadratic contrasts. Data were reported as LSMEANS. Broken line linear (BLL) and broken line quadratic (BLQ) analyses were conducted to determine the SID Trp:Lys requirement for growth parameters. In phase 1, pig ADG increased (0.76, 0.79, 0.79, 0.82, 0.83, 0.81 kg/day; L P<0.01, Q P<0.04) as the Trp:Lys ratio increased. In addition, there was a linear improvement in feed conversion (0.49, 0.49, 0.50, 0.50, 0.50, 0.50; P<0.08). In phase 2, pig ADG was not influenced by Trp:Lys ratio (0.96, 0.91, 0.98, 1.01, 0.98, 0.96; P=0.31), while feed conversion was improved linearly (0.38, 0.38, 0.39, 0.39, 0.39; P<0.03). In phase 3, pig ADG increased linearly (0.91, 0.93, 0.99, 1.00, 1.02, 0.97; P<.05) and feed conversion was improved (0.32, 0.33, 0.34, 0.34, 0.32; P<0.05) quadratically as the Trp:Lys ratio increased. Based on the data, the optimal ratio for ADG in grow-finish pigs is between 18.0 and 21.4. The optimal ratio for feed conversion is less consistent at about 15 for BLL and 19.5 or greater for BLQ.
|
|
BLL |
BLQ |
Phase 1 |
|
|
|
|
ADG |
19.8 |
21.4 |
|
G:F |
15.1 |
23.8 |
Phase 2 |
|
|
|
|
ADG |
18.0 |
19.7 |
|
G:F |
14.7 |
30.6 |
Phase 3 |
|
|
|
|
ADG |
18.4 |
20.8 |
|
G:F |
15.1 |
19.5 |
Keywords: grow finish, pig, tryptophan