Effects of Added Potassium to Diets with High or and Low Effects of Added Potassium to Diets with High or and Low Crystalline Lysine on Finishing Pig Growth Performance Crystalline Lysine on Finishing Pig Growth Performance

Summary This experiment was conducted to evaluate the effect of balancing dietary cation-anion difference (DCAD) levels, via added potassium bicarbonate (KHCO 3 ), to diets containing low or high levels of L-Lys HCL on growth performance of growing-fin-ishing pigs. A total of 1,944 pigs (PIC L337 × 1050; initially 77.6 ± 1.88 lb BW) were used in a 120-d study to determine the effect of added potassium bicarbonate to diets containing low or high levels of crystalline lysine on growth performance and carcass characteristics of finishing pigs. Pens of pigs were blocked by BW and randomly allotted to 1 of 4 dietary treatments in a randomized complete block design arranged in a 2 × 2 factorial with main effects of KHCO 3 (0 vs. 0.4%), and L-Lys HCl level (low vs. high). There were 27 pigs per pen and 18 replicates per treatment and a similar number of barrows and gilts placed in each pen. Treatment diets were corn-soybean meal-based and formulated in four dietary phases (approximately 80 to 130 lb, 130 to 185 lb, 185 to 230 lb, and 230 to 285 lb). 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. Additionally, the diet with a low level of L-Lys HCl with KHCO 3 was formulated to have the highest DCAD in each phase, while the diet with a high level of L-Lys HCl without KHCO 3 was formulated to have the lowest DCAD. 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.


Introduction
The use of crystalline lysine (L-Lys HCl) to replace a portion of the lysine provided by feeding soybean meal to growing-finishing pigs is common in modern swine production.Several studies have indicated that adding more than 0.15% L-Lys HCl without the addition of other feed-grade amino acids can limit growth performance due to resulting deficiencies in other amino acids. 3The development and inclusion of various crystalline amino acids in swine diets in recent years has helped to address this issue.However, it has also been shown that the resulting reduction in DCAD that is caused by adding high levels of Cl -, via L-Lys HCl, may result in decreased performance. 4It is possible that this could be rectified by the addition of monovalent cations, such as Na + or K + , to balance intracellular anions, thus regaining lost performance.Therefore, the objective of this study was to evaluate the effect of balancing DCAD levels, via added potassium bicarbonate (KHCO 3 ), to diets containing low or high levels of L-Lys HCl on growth performance of growing-finishing pigs.

Procedures
The Kansas State University Institutional Animal Care and Use Committee approved the protocol used in this experiment.This study was conducted at a commercial research-finishing site in southwest Minnesota (New Horizon Farms, Pipestone, MN).The barns were naturally ventilated and double-curtain-sided, with completely slatted concrete flooring over deep pits for manure storage.Each pen (10 × 18 ft) was equipped with a 5-hole stainless steel dry feeder (Thorp Equipment, Inc., Thorp, WI) and a pan waterer for ad libitum access to feed and water.

Animals and diets
A total of 1,944 pigs (PIC L337 × 1050; initially 77.6 ± 1.88 lb BW) were used in a 120-d study, split between 2 barns with 27 pigs per pen and 18 replicates per treatment.Pens of pigs were blocked by initial BW and randomly assigned to 1 of 4 dietary treatments in a randomized complete block design arranged in a 2 × 2 factorial with main effects of KHCO 3 (0 vs. 0.4%), and L-Lys HCl level (low vs. high).Daily feed additions to each pen were accomplished using a robotic feeding system (FeedPro, Feedlogic  Corp., Wilmar, MN) able to record feed amounts for individual pens.All treatment diets were manufactured at the New Horizon Farms Feed Mill in Pipestone, MN, and formulated to meet or exceed NRC 5 requirement estimates for growing-finishing pigs for their respective weight ranges (Table 1).Diets were fed in meal form in four dietary phases from approximately 80 to 130 lb, 130 to 185 lb, 185 to 230 lb, and 230 to 285 lb.
Experimental diets were corn-soybean meal-based and formulated with either low or high levels of L-Lys HCl with the addition of other feed-grade amino acids.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.Additionally, the diet with a low level of L-Lys HCl with KHCO 3 was formulated to have the highest DCAD in each phase, 3 De la Llata, M., S. S. Dritz, M. D. Tokach, R. D. Goodband, and J. L. Nelssen.2002.Effects of increasing L-lysine HCL in corn-or sorghum-soybean meal-based diets on growth performance and carcass characteristics of growing-finishing pigs.J. Anim.Sci., 80:2420-2432.doi:10.1093/ansci/80.9.2420. 4Dersjant-Li, Y., H. Schulze, J. W. Schrama, J. A. Verreth, and M. W. A. Verstegen.2001.Feed intake, growth, digestibility of dry matter and nitrogen in young pigs as affected by dietary cation-anion difference and supplementation of xylanase.J. Anim. Physiol., 85:101-109. doi: 10.1046/j.1439-0396.2001.00307.x. 5 National Research Council. 2012.Nutrient Requirements of Swine: Eleventh Revised Edition.Washington, DC: The National Academies Press.https://doi.org/10.17226/13298.

Swine Day 2022
Kansas State University Agricultural Experiment Station and Cooperative Extension Service while the diet with a high level of L-Lys HCl without KHCO 3 was formulated to have the lowest DCAD (Table 2).
Pens of pigs were weighed, and feed disappearance was measured approximately every 14 d from d 0 to 120 of the trial to determine ADG, ADFI, and F/G.The 3 heaviest pigs from each pen were marketed on d 98 (group 1) and d 99 (group 2).These pigs were included in the growth performance data, but not in carcass data.
At completion of the study, final pen weights were taken, individual pigs were tattooed with a pen identification number, and pigs were transported to a commercial abattoir (JBS, Worthington, MN) for processing and carcass data collection.Carcass measurements included HCW, backfat depth, loin depth, and percentage lean.Carcass yields were then calculated by the pen average HCW from the plant divided by the pen average final BW on the farm.

Statistical analysis
Data were analyzed as a randomized complete block design for one-way ANOVA using the lmer function from the lme4 package in R (Version 3.5.2,R Core Team, Vienna, Austria), with pen considered as the experimental unit, initial BW as a blocking factor, and treatment as a fixed effect.Preplanned contrasts were used to evaluate the main effects and interactions of dietary KHCO 3 and L-Lys HCl.Results were considered significant at P ≤ 0.05, and marginally significant at P ≤ 0.10.

Results and Discussion
Analyzed crude protein (CP) levels in treatment diets for phases 1 and 2 were similar to formulated values and followed the trend of reducing CP with the addition of L-Lys HCl (Table 2).The treatment diets in phases 3 and 4 had lower analyzed CP than calculated; however, these diets still followed the trend of reducing CP with increasing L-Lys HCl.Most analyzed mineral and DCAD values are similar to our estimated values when accounting for variation in mineral concentrations of corn-soybean meal from NRC 5 estimates, as well as analytical variation.
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 responses.For carcass characteristics, there was no evidence (P > 0.10) for a KHCO 3 × L-Lys HCl interaction or main effect for any observed response.
In summary, these results suggest that supplementing KHCO 3 to finishing pig diets with either high or low levels of L-Lys HCl and the associated changes in DCAD values did not significantly impact growth performance or carcass characteristics.

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Table 1 .
Diet composition by phase (as-fed basis) 1 Kansas State University Agricultural Experiment Station and Cooperative Extension Service

Table 2 .
Analysis of diets (as-fed basis) Kansas State University Agricultural Experiment Station and Cooperative Extension Service

Table 3 .
Effects of potassium bicarbonate with high and low crystalline lysine levels on growing-finishing pig performance 1 Kansas State University Agricultural Experiment Station and Cooperative Extension Service

Table 4 .
Main effects of potassium bicarbonate and high or low crystalline lysine levels on growing-finishing pig performance 1