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Effects of standardized ileal digestible valine:lysine ratio on nursery pig performance
A total of 280 pigs (PIC 327 × 1050; initially 6.53 kg BW) were used in a 28-d trial to evaluate the effects of increasing standardized ileal digestible (SID) Val:Lys ratio on nursery pig growth performance. Pigs were weaned at 21 d of age and 5 pigs allotted to each nursery pen according to BW and gender. A common diet was fed for 5 d when pens were assigned to 1 of 7 dietary treatments in a randomized block design with 8 pens per treatment. Experimental diets were fed from d 0 to 14 followed by a common diet from d 14 to 28. The 7 dietary treatments were 50, 57, 63, 68, 73, 78, and 85% SID Val:Lys. A prior experiment demonstrated a Lys requirement of 1.44 and 1.45% SID Lys for ADG and G:F, respectively, for pigs in this facility. Thus, diets were formulated to 1.24% SID Lys to ensure pigs were below the Lys requirement. As SID Val:Lys increased, ADG, ADFI, and G:F increased (quadratic, P<0.05). Growth response variables were fitted using linear and non-linear dose-response models with pen as the experimental unit and initial BW as a covariate with ADG and G:F fitted using heterogeneous and homogenous residual variance, respectively. Models fit were quadratic polynomial (QP), broken-line linear (BLL), and broken-line quadratic with best fit determined according to Bayesian information criterion. For ADG, the best fitting model was BLL and maximum ADG was achieved with a minimum of 62.9% SID Val:Lys (95% CI: [52.2, 73.7%]). For G:F, the best fitting model was QP [0.010294+0.017526*(Val:Lys)–0.000122*(Val:Lys)2] using a 6.53 kg initial BW. This resulted in a maximum G:F at 71.7% SID Val:Lys and 99% of maximum achieved at a 64.4% ratio. In summary, the SID Val:Lys requirement ranged from 62.9 to 71.7% depending on the response model.
|
SID Val:Lys, % |
|
Probability, P < |
|||||||
Item: |
50 |
57 |
63 |
68 |
73 |
78 |
85 |
SEM |
Linear |
Quadratic |
d 0 to 14 |
|
|
|
|
|
|
|
|
|
|
ADG, g |
190 |
221 |
249 |
249 |
248 |
251 |
238 |
11.2 |
0.001 |
0.001 |
ADFI, g |
331 |
363 |
394 |
388 |
403 |
390 |
386 |
17.2 |
0.012 |
0.030 |
G:F |
0.579 |
0.613 |
0.635 |
0.646 |
0.614 |
0.645 |
0.617 |
0.0189 |
0.101 |
0.039 |
Keywords: valine, amino acids, nursery pigs