Effects of adding potassium bicarbonate to diets with high or low crystalline lysine to influence dietary cation-anion difference on finishing pig growth performance.

Dietary cation-anion difference (DCAD), calculated as Na + + K + - Cl - in mEq/kg of the diet, represents the influence that monovalent cations and anions from these minerals have on the acid-base status of the animal. However, the recommended range of DCAD for optimal grow-finish swine performance is variable, which may indicate an interaction between DCAD and other ingredients. The hypothesis for this study was that the addition of potassium bicarbonate (KHCO 3 ) to increase diet DCAD when high levels of l-Lys HCl (>0.35% diet) are used may potentially improve growth performance. A total of 1,944 pigs (PIC L337 × 1050, initially 35.2 ± 0.85 kg) were used in a 120-d study. Pens of pigs were blocked by BW and randomly allotted to 1 of 4 dietary treatments in a randomized complete block design. Treatments were arranged in a 2 × 2 factorial with main effects of KHCO 3 (0% or 0.4%), and l-Lys HCl level (low or high). l-Lys HCl was included between 0.13% and 0.21% in low diets, and between 0.36% and 0.43% in high diets. There were 27 pigs per pen and 18 replicates per treatment. Treatment diets were corn-soybean meal-based and formulated in four dietary phases (35-60 kg, 60-85 kg, 85-105 kg, and 105-130 kg). Dietary treatments were formulated such that in each phase the diet containing a low level of l-Lys HCl without KHCO 3 and the diet containing a high level of l-Lys HCl with KHCO 3 had similar calculated DCAD values (169-232 mEq/kg). Additionally, the diet with a low level of l-Lys HCl with KHCO 3 was formulated to have the highest DCAD in each phase (220-281 mEq/kg), while the diet with a high level of l-Lys HCl without KHCO 3 was formulated to have the lowest DCAD (118-182 mEq/kg). Overall, there was no evidence ( P > 0.10) for a KHCO 3 × l-Lys HCl interaction or main effect for final BW or any observed growth response or carcass characteristics. The results of this study suggest that supplementing KHCO 3 to finishing pig diets with either high or low levels of l-Lys HCl and the corresponding changes in DCAD values did not impact growth performance or carcass characteristics.