Short communication: Estimation of the dietary standardized ileal digestible valine to lysine ratio required for 40 to 130 kg pigs during the finisher periods.

Background: Three experiments were conducted separately to determine the optimum standardized ileal digestible (SID) valine (Val) to lysine (Lys) ratio for early finishing (Experiment 1, 40 to 75 kg bodyweight), finishing (Experiment 2, 75 to 100 kg bodyweight), and late finishing (Experiment 3, 100 to 130 kg bodyweight) pigs. Dietary SID Val: Lys ratios were designed at 0.61, 0.65, 0.69, 0.73, and 0.77. The optimal SID Val: Lys ratio was estimated by different regression models, including a quadratic polynomial model, a two-slope quadratic broken-line model, a curvilinear-plateau model, and a one-slope straight broken-line model.

Results: In Exp.1, a total of 550 early finishing pigs (initially 40.3 kg bodyweight) were used in a 38-day growth trial. Pigs consuming 0.61 dietary SID Val: Lys ratio had lower final bodyweight compared to those fed 0.69 in diets. Using regression models, the optimal dietary SID Val: Lys requirement for average daily gain (ADG) was between 0.63 and 0.68, and for feed to gain ratio (F: G) was between 0.62 and 0.68, respectively. In Exp.2, 525 finishing pigs (initially 76.4 kg) were used in a 26-day trial. Based on regression models, estimate of the required SID Val: Lys for ADG was between 0.65 and 0.71, and for F: G was between 0.64 and 0.70, respectively. In Exp.3, 640 late finishing pigs (102 kg bodyweight) were used in a 27-day trial. No significant improvement was found for performance parameters of pigs from 100 to 130 kg, while 0.73 SID Val: Lys ratio resulted in the highest ADG and the lowest F: G from a numerical point of view.

Conclusions: These findings indicated that the optimum SID Val: Lys requirement for pigs from 40 to 75 kg was between 0.62 and 0.68, and for pigs from 75 to 100 kg was estimated to be between 0.64 and 0.71, using different regression models.