Modeling the effects of standardized ileal digestible valine to lysine ratio on growth performance of nursery pigs. Transl Anim Sci 2017;1:448-457. [PMID: 32704668 PMCID: PMC7204984 DOI: 10.2527/tas2017.0049]

The biological functions and metabolic pathways of valine in swine

Valine is an essential amino acid and a type of branched-chain amino acid. Due to the involvement of branched-chain amino acids in various metabolic pathways, there has been a surge of interests in valine nutrition and its role in animal physiology. In pigs, the interactions between valine and other branched-chain amino acids or aromatic amino acids are complex. In this review, we delve into the interaction mechanism, metabolic pathways, and biological functions of valine. Appropriate valine supplementation not only enhances growth and reproductive performances, but also modulates gut microbiota and immune functions. Based on past observations and interpretations, we provide recommended feed levels of valine for weaned piglets, growing pigs, gilts, lactating sows, barrows and entire males. The summarized valine nutrient requirements for pigs at different stages offer valuable insights for future research and practical applications in animal husbandry.

Evaluation of branched-chain amino acid interactions in 10 to 20 kg nursery pigs using a central composite design

Two groups of 240 pigs (PIC 337 × 1050, PIC Genus, Hendersonville, TN) were used to investigate the interactions between leucine, isoleucine, and valine on the growth performance of approximately 10 to 20 kg nursery pigs. At weaning, pigs were placed into 40 pens with three barrows and three gilts per pen and fed a common diet for 3 wk. On day 21 postweaning, pens were randomly assigned to 1 of 15 dietary treatments in a central composite design. Diets were formulated to various levels of standardized ileal digestible (SID) Leu, Ile, and Val by supplementing L-Leu, L-Ile, and L-Val. Levels of the branched-chain amino acids, expressed as ratios to SID Lys, ranged from 98% to 180%, 46% to 64%, and 51% to 78% for Leu, Ile, and Val, respectively. Diets were formulated to be iso-Lys, isonitrogenous, and isocaloric. Pig weights and feed intake were measured for the 21-d experiment to calculate average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency (G:F). Growth performance data were analyzed using the lm() function in R version 4.2.2 (R Core Team, 2022). The second-order polynomial model included the linear and quadratic effects of Leu, Ile, and Val, their three two-way interactions, and initial body weight. Pen was the experimental unit, and parameters were considered significant at P ≤ 0.10. A linear and quadratic effect of Val was observed for ADG and G:F (P < 0.001). There was an interaction between Leu and Ile for ADG (P = 0.069) and G:F (P = 0.032), where increasing Leu and decreasing Ile, and the inverse, improved ADG and G:F. However, growth and efficiency were negatively impacted as Leu and Ile increased in the diet. There was an interaction between Leu and Val for ADFI (P = 0.060), where Leu negatively impacted feed intake at low levels of Val but had little impact as Val increased above NRC (2012) recommendations. In conclusion, Val linearly and quadratically impacted ADG and G:F, regardless of Leu and Ile levels in the diet, while ADG and G:F were reduced with high levels of Leu and Ile, which was resolved as either Leu or Ile was reduced. Furthermore, ADFI was negatively impacted by increased Leu when Val was below NRC (2012) recommendations but was not affected by Leu at higher Val levels. Together, the results of this experiment emphasize the complexity of amino acid metabolism in nursery pigs and the importance of considering potential interactions among amino acids when conducting requirement studies.

Impact of increasing standardized ileal digestible valine: lysine in diets containing 30% dried distiller grains with solubles on growing pig performance

A total of 2,430 pigs (DNA 600 × Topigs Norsvin 70, initially 39.4 kg) were used in a 28-d trial to determine the standardized ileal digestible (SID) Val:Lys requirement for pigs fed with diets containing 30% DDGS. Treatments included five diets containing 30% DDGS with SID Val:Lys ratios of 60%, 65%, 70%, 75%, and 80%, plus a corn soybean meal (SBM) diet, for a total of six dietary treatments. Diets were formulated to be isocaloric through the inclusion of fat and to contain equal amounts of SID Lys within phase. Pens were assigned to dietary treatment in a randomized complete block design with initial body weight (BW) as the random blocking factor. Each dietary treatment was replicated 15 times and pens contained 27 pigs, balanced for sex. Increasing the SID Val:Lys ratio in diets containing 30% DDGS increased (Quadratic; P ≤ 0.007) 14-d BW, final BW, average daily gain (ADG), average daily feed intake (ADFI), and gain:feed (G:F) for all periods. Providing an SID Val:Lys ratio of 75% resulted in the heaviest 14-d BW and final BW as well as greater ADG and ADFI of pigs fed with 30% DDGS for all periods. The G:F response was maximized when an SID Val:Lys ratio of 70% was provided from day 0 to 14 while an SID Val:Lys ratio of 75% maximized G:F from day 14 to 28 and for the cumulative period. The SID Val:Lys requirement was estimated at 66.6% (95% CI [65.9, 67.4]), 65.7 (95% CI: [64.8, 66.5]), and 68.4% (95% CI [66.0, 70.8]) for ADG, ADFI, and G:F, respectively, using the straight broken line (SBL) method and 69.9% (95% CI [68.2, 71.5]), 67.6 (95% CI [65.4, 69.8]), and 72.8% (95% CI [69.8, 75.8]) for the quadratic broken line (QBL) method. Pigs fed the corn-SBM diet had heavier 14-d BW, final BW, and greater ADG, ADFI, G:F (P ≤ 0.032) compared to pigs fed diets containing 30% DDGS, except for cumulative ADFI compared to pigs receiving 75% SID Val:Lys (P = 0.167). In conclusion, these results suggest that when feeding 30% DDGS during the growing period, an SID Val:Lys ratio of 68% would yield more than 99% and 97% of the maximum ADG and G:F response for the 39 to 68 kg pigs. However, growth performance of pigs fed diets containing 30% DDGS did not equate to pigs consuming the corn-SBM diet regardless of the SID Val:Lys ratio.

The Optimal Valine to Lysine Ratio for Performance Parameters in Weaned Piglets

Simple Summary

Animal production has an impact on environmental issues, like global warming. Reducing the protein level in animal feed has the potential to decrease fecal and urinary nitrogen excretion and consequently reduces the environmental nitrogen load. The usage of crystalline L-valine is a potential solution to maintain growth performance of piglets when feeding low protein diets. Aim of this study was to determine the optimal valine requirement in weaned piglets. Therefore, 200 weaned piglets were allotted to five feeding groups and received diets with consecutive increasing amounts of L-valine. The supplementation of L-valine to a valine-deficient basal diet led to an increase in growth and feed intake of weaned piglets. Supplementary valine has the potential to decrease the amount of excess dietary nitrogen, namely through meeting valine requirements via supplementary valine instead of increasing dietary crude protein content.

Abstract

The optimal digestible (d) Valine (Val) to d Lysine (Lys) ratio (dVal:dLys) in weaned piglets was determined using two different regression models. A total of 200 piglets were allotted to five feeding groups and fed a corn-soybean meal based basal diet supplemented with consecutive increasing amounts of crystalline L-valine in order to reach dVal:dLys of 0.59, 0.63, 0.67, 0.71, 0.75 in the pre-starter (0–13 days) and 0.57, 0.62, 0.66, 0.70, 0.75 in the starter phase (13–43 days). In the starter phase and during the whole period, supplementing the basal diet with L-valine resulted in an improvement in body weight gain and feed intake. An exponential asymptotic (EA) and a curvilinear-plateau (CLP) regression model were fit to feed intake and body weight gain data. The estimated dVal:dLys for body weight gain was found to be 0.68 (EA, 95% of maximum response) and 0.67 (CLP) in the starter phase and 0.65 (EA, 95% of maximum response and CLP) in the total trial period. It is concluded that the supplementation of a valine-deficient basal diet for weaned piglets with L-valine improves the piglet’s weight gain and feed intake and that a dVal:dLys of 0.68 is recommended to optimize body weight gain.

Effects of high-protein distillers dried grains on growth performance of nursery pigs

A total of 300 pigs (DNA 400 × 200, Columbus, NE), initially 11.1 kg, were used in a study to evaluate the effects of increasing amounts of high-protein distillers dried grains (HP DDG) on growth performance and to estimate its energy value relative to corn. Pigs were weaned, placed in pens with five pigs each, and fed a common diet for 21 d after weaning. Then, pens were assigned to treatments in a randomized complete block design. There were 5 treatments with 12 replicates per treatment. Treatments consisted of 0, 10, 20, 30, or 40% HP DDG, formulated by changing only the amounts of corn and feed-grade amino acids. Pigs were weighed weekly for 21 d to evaluate average daily gain (ADG), average daily feed intake (ADFI), and gain-to-feed ratio (G:F). Caloric efficiency was obtained by multiplying ADFI by kcal of net energy (NE) per kg of diet and dividing by ADG. The NE values for corn and soybean meal were obtained from NRC (2012), and initial estimates for HP DDG NE were derived from the Noblet et al. (1994) equation. The energy of HP DDG was estimated based on caloric efficiency relative to the diet without HP DDG. Pigs fed diets with increasing HP DDG had a linear decrease (P < 0.01) in ADG, ADFI, and final body weight. There was a tendency for a quadratic response (P = 0.051) in G:F, with the greatest G:F observed for pigs fed diets with 40% HP DDG. There was a linear reduction (P < 0.05) in caloric efficiency with increasing amounts of HP DDG, indicating the initial NE estimate of HP DDG was underestimated. The use of caloric efficiency to estimate the energy value of HP DDG presents several limitations. This approach assumes that the NE values of corn and soybean meal are accurate and does not take into account possible changes in body composition, which can influence the G:F response as leaner pigs are more efficient. In conclusion, increasing HP DDG in the diet linearly decreased ADG and ADFI. Using caloric efficiency to estimate energy content relative to corn, the HP DDG used in this study was estimated to be 97.3% of the energy value of corn. Direct or indirect calorimetry is needed to confirm this value.

Effects of amino acid biomass or feed-grade amino acids on growth performance of growing swine and poultry

Three experiments were conducted to determine the effect of three fermented amino acids (AA) with their respective biomass compared to crystalline AA on the growth performance of swine and poultry. In experiment 1, 315 barrows (DNA 200 × 400, initially 11.3 ± 0.69 kg) were allotted to 1 of 4 dietary treatments with 5 pigs per pen and 15 or 16 pens per treatment. Dietary treatments included a negative control (16% standardized ileal digestible [SID] Tryptophan:lysine [Trp:Lys] ratio), positive control (21% SID Trp:Lys ratio from crystalline Trp), or diets containing Trp with biomass to provide 21 or 23.5% SID Trp:Lys ratios, respectively. Pigs fed the positive control or low Trp with biomass diet had increased (P < 0.05) ADG compared to pigs fed the negative control diet, with pigs fed the high Trp with biomass diet intermediate. Pigs fed the low Trp with biomass diet had increased (P < 0.05) G:F compared to the negative control diet, with others intermediate. In experiment 2, 1,320 1-d-old male broilers (Cobb 500, initially 45.2 g) were allotted to one of four dietary treatments with 33 birds per pen and 10 pens per treatment. Dietary treatments included a negative control (58/58% Threonine:lysine [Thr:Lys] ratio), positive control (65/66% Thr:Lys ratio from crystalline Thr), or diets containing Thr with biomass to provide 65/66 or 69/70% Thr:Lys ratios in starter and grower diets, respectively. Broilers fed the positive control or Thr with biomass diets had increased (P < 0.05) ADG compared to broilers fed the negative control diet. Broilers fed the positive control or the low Thr with biomass diet had increased (P < 0.05) G:F compared to the negative control and high Thr with biomass treatments. In experiment 3, 2,100 one-day-old male broilers (Cobb 500, initially 39.4 g) were allotted to one of four dietary treatments with 35 birds per pen and 15 pens per treatment. Dietary treatments included a negative control (59/63% Valine:lysine [Val:Lys] ratio), positive control (75/76% Val:Lys ratio from crystalline Val), or diets containing Val with biomass to provide 75/76 or 84/83% Val:Lys ratios in starter and grower diets, respectively. Broilers fed the positive control or Val with biomass diets had increased (P < 0.05) ADG, ADFI, and G:F compared to those fed the negative control diet. In conclusion, Trp, Thr, or Val with their respective biomass appear to be equally bioavailable and a suitable alternative to crystalline AA in swine and poultry diets.

Branched-chain amino acid interactions in growing pig diets

The branched-chain amino acids (BCAA) Leu, Ile, and Val share the first steps of their catabolism due to similarities in their structure. The BCAA are reversibly transaminated in skeletal muscle through the activity of branched-chain aminotransferase and then transported to the liver. They undergo an irreversible decarboxylation catalyzed by the branched-chain α-keto acid dehydrogenase complex. Both enzymes are common to Leu, Ile, and Val and increased enzymatic activity stimulated by an excess of one of them will increase the catabolism of all BCAA, which can result in antagonisms. Leucine and its keto acid are the most potent stimulators of BCAA catabolic enzymes. Moreover, BCAA and large neutral amino acids (LNAA) share common brain transporters. Research has shown that high concentrations of BCAA, especially Leu, can decrease the absorption of LNAA, such as Trp, which is a precursor of serotonin and can have a significant impact in feed intake regulation. Finally, high Leu concentrations have the ability to overstimulate the mTOR signaling pathway, resulting in an inhibitory effect on feed intake. Most of the research conducted to evaluate the impact of BCAA on growth performance of pigs seems to agree that high levels of Leu decrease weight gain, mostly due to a reduction in feed intake. However, some studies, mostly with finishing pigs, observed no evidence for an impact on growth performance even with extremely high levels of Leu. It could be hypothesized that these inconsistencies are driven by the entire dietary amino acid profile as opposed to only considering the level of Leu. Grow-finish diets typically contain high levels of Leu, but the other BCAA are also well above the requirement and could potentially mitigate the negative impact of Leu on BCAA catabolism. Indeed, some studies suggest that when diets contain high levels of Leu, more Ile and Val are needed to optimize growth performance. However, the precise relationship between BCAA and their balance in swine diets is not fully understood. More research is needed to understand and quantify the relationship between LNAA and BCAA.

Meta-regression analysis to predict the influence of branched-chain and large neutral amino acids on growth performance of pigs1

A meta-analysis was conducted to evaluate the effects of branched-chain amino acids (BCAA), their interactions, and interactions with large neutral amino acids (LNAA) to develop prediction equations for growth performance of pigs. Data from 25 papers, published from 1995 to 2018, for a total of 44 trials and 210 observations were recorded in a database. Diets were reformulated using the NRC (2012) loading values to estimate nutrient concentrations. The response variables were average daily gain (ADG), average daily feed intake (ADFI), and gain-to-feed ratio (G:F). The predictor variables tested included average body weight (BW), crude protein, neutral detergent fiber, Ile:Lys, Leu:Lys, Val:Lys, BCAA:Lys, Ile:Leu, Val:Leu, Ile:Val, (Ile+Val):Leu, Trp:Lys, Leu:Trp, Ile:Trp, Val:Trp, BCAA:Trp, Met:Lys, Leu:Met, Ile:Met, Val:Met, BCAA:Met, His:Lys, Leu:His, Ile:His, Val:His, BCAA:His, Thr:Lys, Leu:Thr, Ile:Thr, Val:Thr, BCAA:Thr, (Phe+Tyr):Lys, Leu:(Phe+Tyr), Ile:(Phe+Tyr), Val:(Phe+Tyr), BCAA:(Phe+Tyr), LNAA:Lys, Leu:LNAA, Ile:LNAA, Val:LNAA, and BCAA:LNAA. Amino acids were expressed on standardized ileal digestible basis. The MIXED procedure of SAS (SAS Institute Inc., Cary, NC) was used to develop the equations. The inverse of squared SEM was used to account for heterogeneous errors using the WEIGHT statement. Models were selected with a step-wise manual forward selection. In order to be included in the final model, predictor variables had to be statistically significant (P < 0.05) and provide an improvement of at least 2 points in Bayesian information criterion. The optimum equations were: ADG, g = - 985.94 + (15.2499 × average BW (kg)) - (0.08885 × average BW × average BW) + (1.063 × Leu:Lys) + (20.2659 × Ile:Lys) - (0.1479 × Ile:Lys × Ile:Lys) + (9.2243 × (Ile+Val):Leu) - (0.03321 × (Ile+Val):Leu × (Ile+Val):Leu) - (0.4413 × Ile:Trp); G:F, g/kg = 648.3 - (6.2974 × average BW (kg)) + (0.02051 × average BW × average BW) + (0.5396 × Ile:Lys) + (1.7284 × Val:Lys) - (0.00795 × Val:Lys × Val:Lys) - (1.7594 × Met:Lys); and ADFI, kg = predicted ADG/predicted G:F. Overall, the prediction equations suggest that increasing Leu:Lys negatively impacts ADG due to a reduction in G:F and ADFI caused by insufficient levels of other BCAA and LNAA relative to Leu. According to the model, the addition of Val, Ile, and Trp, alone or in combination, has the potential to counteract the negative effects of high dietary Leu concentrations on growth performance.

Effects of standardized ileal digestible histidine to lysine ratio on growth performance of 7- to 11-kg nursery pigs

Histidine may be the sixth limiting amino acid (AA) in practical nursery diets supplemented with high amounts of feed-grade AA. Therefore, 2 experiments were conducted to determine the standardized ileal digestible (SID) His:Lys ratio requirement estimate for growth performance of 7- to 11-kg nursery pigs. A total of 360 and 350 pigs (DNA 241 × 600, Columbus, NE; initially 7.1 ± 0.31 and 6.6 ± 0.36 kg) were used in Exp. 1 and 2, respectively. There were 5 pigs per pen with 12 replicates per treatment in Exp. 1 and 10 replicates per treatment in Exp. 2. After weaning, pigs were fed a common pelleted diet for 10 d in Exp. 1 and 7 d in Exp. 2. Then, pens were assigned to treatments in a randomized complete block design with body weight (BW) as the blocking factor. Dietary treatments consisted of SID His:Lys ratios of 24%, 28%, 32%, 36%, 40%, and 44% in Exp. 1 and 24%, 28%, 30%, 32%, 34%, 36%, and 42% in Exp. 2. Experimental diets were fed in pellet form for 10 or 14 d in Exp. 1 and 2, followed by a common mash diet for 15 or 14 d, respectively. Data were analyzed using the GLIMMIX and NLMIXED procedures of SAS, fitting data with heterogeneous variance when needed. The competing statistical models utilized were quadratic polynomial, broken-line linear (BLL), and broken-line quadratic. In Exp. 1, increasing SID His:Lys ratio increased (quadratic, P = 0.001) ADG, ADFI, G:F, and day 10 BW. In Exp. 2, ADG, G:F, and day 14 BW increased (quadratic, P = 0.001), and ADFI increased linearly (P = 0.001) with increasing SID His:Lys ratio. The best-fitting model for all response variables analyzed was the BLL. In Exp. 1, requirement estimates were 29.7%, 29.1%, and 29.8% SID His:Lys ratio for ADG, ADFI, and G:F, respectively. In Exp. 2, the SID His:Lys ratio requirement estimates were 31.0% for ADG and 28.6% for G:F. These results suggest that the SID His requirement estimate for growth performance is no more than 31% of Lys and that the NRC (2012) SID His requirement of 34% of Lys may be overestimated for 7- to 11-kg pigs.