J APPL POULT RES 2007. 16:546-554. doi:10.3382/japr.2007-00025
© 2007 Poultry Science Association
Marginality and Needs of Dietary Valine for Broilers Fed Certain All-Vegetable Diets1
A. Corzo*,2,
M. T. Kidd*,
W. A. Dozier, III
and
S. L. Vieira
* Department of Poultry Science, Mississippi State University, Mississippi State 39762; USDA, Agricultural Research Service, Mississippi State, MS 39762; and Department of Animal Science, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
Correspondence: 2 Corresponding author: acorzo{at}poultry.msstate.edu
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SUMMARY
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Valine is likely the fourth limiting amino acid in most diets based on corn and soybean meal (C/SBM). However, the exact needs for Val are not well known, and information regarding it is sparse. A series of studies was conducted to validate the limitation of Val in all-vegetable diets fed to broilers, and subsequently to quantify an adequate ratio to Lys in high-yield late-developing broilers (Ross x Ross 708) from 21 to 42 d. A preliminary study was designed to evaluate the supplementation of different amino acids likely to be fourth limiting on a C/SBM-based diet, where Lys, TSAA, and Thr were supplemented but no other critical amino acids were given minimums in the formulation. Results obtained for BW gain, abdominal fat weight, and abdominal fat percentage showed that birds were more responsive (P < 0.05) to L-Val supplementation. A follow-up study using a corn-peanut meal (C/PM)-based diet formulated to be deficient in Val validated (P < 0.05) a Val deficiency based on poor growth performance and resulted in an immediate return to good performance when this amino acid was supplemented. Furthermore, the C/PM diet was compared with a nutritionally similar C/SBM diet, and no difference was observed in the performance of broilers fed these diets, thus validating the ability of the C/PM-based diet to support adequate growth of these broilers. This C/PM-based diet was used to feed gradual concentrations of Val, from levels that would be considered deficient (0.59% digestible) up to adequate (0.84% digestible Val). Results indicate that a ratio of Val to Lys of 78, or a minimum dietary value of 0.74% digestible Val (0.82% total Val), should be adequate for this high-yield broiler grown from 21 to 42 d of age.
Key Words: breast meat yield • broiler • lysine • valine
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DESCRIPTION OF PROBLEM
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With the availability of Lys, Met, and Thr as feed grade amino acids ready for supplementation, constraints on dietary CP supply in broiler diets can be alleviated during times of increasing cost of soybean meal or animal protein by-products. Because L-Thr is now being accepted and used worldwide, the focus is now set on satisfying the needs of the fourth limiting amino acid in the diet if an adequately balanced dietary protein is to be fed. Regardless of whether that fourth limiting amino acid need is being satisfied in the formulation by a ratio to Lys (ideal protein) or as a nutrient minimum, the identity of this amino acid will depend completely on the feed ingredients that will constitute the diet. Recently, Kidd and Hackenhaar [1] created scenarios that varied in the type of feed ingredients being used, and hypothesized which would be the next limiting amino acid after Thr for each of those conditions. The authors suggested that when using corn and soybean meal (C/SBM) as the primary protein contributing ingredients in a broiler diet, Val was the fourth limiting amino acid based on their nutrient matrix values for dietary nutrients and nutrient ratio requirements [1].
The importance of maintaining adequate levels of dietary Val when reducing dietary CP, particularly in those diets based on C/SBM, has been described previously [2, 3, 4, 5, 6, 7]. When supplementing a C/SBM-based diet with Lys, Met, and Thr, dietary CP decreases, which often results in a concomitant decrease in diet cost. However, the ability of a diet to support optimal broiler performance will largely rely on maintaining adequate levels of those limiting amino acids subsequent to Thr. For that purpose, a series of studies was conducted to validate the importance of dietary Val in C/SBM-based diets and assess its need in a high-yield, late-developing broiler strain cross.
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MATERIALS AND METHODS
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Bird Husbandry
For all studies, the following experimental conditions applied. Ross x Ross 708 [8] 1-d-old male chicks were used. They were randomly distributed into floor pens in a closed-sided house equipped with thermostatically controlled heating, curtains, and cross-ventilation. Built-up litter was used in all pens, and pens were equipped with a nipple drinker line (3 nipples/pen) and a hanging feeder (22.5 kg capacity). Feed and water were offered ad libitum. The lighting program consisted of 23 h of light and 1 h of dark. Ventilation was accomplished by negative air pressure. Chicks were vaccinated for Marek’s disease (via in ovo administration at d 18), Newcastle disease, and infectious bronchitis (via coarse spray at hatch). From placement to 21 d of age, the birds received common C/SBM feeds formulated to meet or exceed nutrient recommendations [9], and feeds were provided in crumbled form.
At 21 d of age, bird numbers were equalized among all pens (12 birds/pen; 0.1 m2/bird), and treatments were assigned to pens to provide a similar distribution of average bird weight at the start of the experiments.
Evaluation Criteria
The mean bird weight of all pens was recorded at the initiation (21 d) and termination (42 d) of the experimental phase for all experiments. Feed consumption and mortality were recorded. Feed conversion was corrected for mortality and represents grams of feed consumed by all birds in a pen divided by grams of BW gain per pen plus the BW of the birds that died. For experiments 1 and 3, 6 birds per pen were weighed at d 42 and cooped 12 h before processing. Carcass and abdominal fat weights were obtained and recorded. Carcasses were chilled for 4 h and the breast muscles (boneless-skinless) were manually deboned, weighed, and recorded.
Statistical Analyses
Data obtained from each experiment were evaluated by ANOVA by using a randomized complete block design. Pen was used as the experimental unit for analysis. Percentage data for mortality were transformed to arcsine square root percent for analysis. All data were analyzed by the GLM procedure of SAS [10]. Treatment effects were tested and means were separated by using a Tukey test with an 
of 0.05. For experiment 3, data were evaluated for linear, quadratic, or cubic responses. Only linear and quadratic effects are displayed, because significance (P > 0.05) was not observed in higher order polynomials. Regression analysis was used to estimate Val optimization (95% of the maximum response) whenever a significant quadratic response (P < 0.05) was observed.
Diets and Experiments
Calculated total and digestible amino acid values of feed ingredients used in all studies were obtained from Ajinomoto Heartland Inc. [11] (true digestibility of essential amino acids for poultry). Composite samples of dietary treatments were obtained and analyzed for protein bound and supplemented amino acids [12] to ensure that calculated and analyzed total amino acid values were in agreement. Experiment 1 was designed to measure amino acid supplementation to a diet that was formulated to meet Lys, TSAA, and Thr needs of growing broilers, but that disregarded the amino acid levels of other potential limiting amino acids (Table 1
). Supplementation was done by adding L-Ile, L-Arg, L-Val, or Gly to a test diet at the expense of an inert filler (sand). A diet with a higher CP that ensured that all the other (Ile, Arg, Val, Gly + Ser) limiting amino acids would be supplied at adequate levels served as the control (CS-1). Diets were fed in pellet form. The 6 treatments were replicated 6 times, with each experimental unit consisting of a floor pen (0.9 x 1.2 m) composed of 12 broilers.
Experiment 2 was designed to validate a deficiency in dietary Val, and to observe whether L-Val supplementation would result in the return of satisfactory performance. This study was also intended to validate the use of a corn-peanut meal (C/PM)-based diet as a dose-response diet, to be used in experiment 3, by comparing it with the performance obtained by birds fed a C/SBM-based diet with similar nutritional characteristics (CS-2). Diets were fed in pellet form. A total of 3 treatments were fed, each replicated 6 times, with each experimental unit consisting of a floor pen (0.9 x 1.2 m) composed of 12 broilers.
The final study (experiment 3) attempted to estimate the optimal Val-to-Lys ratio of broilers fed a dose-response diet deficient in dietary Val (0.59% digestible Val), consisting of 6 different graded levels of dietary Val accomplished by the addition of L-Val at 0.05% of the diet at the expense of an inert filler (sand). The dose-response diet was a C/PM-based diet fed in pellet form and formulated to minimize Val content while ensuring the minimal levels of all other essential amino acids in a manner that would meet or exceed current recommendations [9]. However, dietary Lys was formulated to be slightly marginal (0.95% digestible) so that an overestimation of the Val-to-Lys ratio would not occur. A total of 6 progressive dietary Val levels were replicated 8 times, with each experimental unit consisting of a floor pen (0.9 x 1.2 m) composed of 12 broilers. All animal procedures were approved by the university’s Institutional Animal Care and Use Committee.
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RESULTS AND DISCUSSION
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Experiment 1: Marginality of Val in C/SBM-Based Diets
Total amino acid analyses of the experimental diets showed that the test diet had marginal dietary Ile, Val, Arg, and Gly + Ser levels compared with those observed in the control diet (Table 1
, footnote 8). The reduction in CP can lead to other amino acids becoming limiting when those are not considered during formulation. The effects of feeding a high-CP diet, a low-CP diet (test) supplemented with Lys, Met, and Thr but with limiting levels of other potential amino acids, and their subsequent individual additions to that low-CP test diet are displayed in Table 2. It should be noted that only those parameters that resulted in a significant treatment effect during experiment 1 are displayed.
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Table 2. Live performance and abdominal fat percentage of broiler chickens fed supplemental dietary levels of Val, Ile, Arg, or Gly (experiment 1)1
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A depression in growth and feed conversion concurrent with an increase in abdominal fat absolute and relative weights was the result of feeding the test diet when compared with the control and some of the other dietary treatments. These data illustrate that amino acid minima or ratios should be used during formulation to prevent depression of growth and feed conversion when feeding a reduced dietary CP in an attempt to decrease cost, nitrogen excretion, or both. Interestingly, only the addition of dietary Val resulted in broilers with BW gain, abdominal fat weight, and abdominal fat percentage similar to those fed the control diet (Table 2). Even though those broilers supplemented with L-Val failed to separate themselves statistically from most of the other supplemented amino acids, it was the only dietary treatment that resulted in intermediate responses that were similar to those seen in broilers fed the control diet. Even though data suggest that a nitrogen response may have been observed for most of the supplemented amino acids used in this study, it was only Val supplementation that statistically equaled the control group, indicating that, perhaps more than a nitrogen response, a dietary limitation likely occurred. The composite of responses elucidates the importance of Val as a potential fourth limiting amino acid in C/SBM-based diets, particularly when a reduction in CP takes place. Similar observations have been reported previously [2, 5], in agreement with the limitation for Val when feeding C/SBM-based diets. Values and responses very similar to those reported here for abdominal fat percentage were previously documented [3]. This similarity in abdominal fat percentage between the control diet and the test Val-supplemented diet can be partially explained by the unique ability of this amino acid to reduce certain lipogenic pathways [13].
Experiment 2: Val Deficiency and Dose-Response Diet Validation
The diets used for the second study were a C/SBM-based diet and a nutritionally similar diet based on C/PM. The C/PM diet was formulated to validate a nutritional deficiency of Val. As expected, total dietary Val values differed when comparing the experimental diets used in this second study (Table 1). One can observe how the nutrient composition of the CS-2 diet and the C/PM diet differed only in their dietary Val levels (Table 1, footnote 8). Table 3 shows how growth, in the form of BW gain and feed conversion, was impaired by the C/PM Val-deficient diet. Data in Table 3 also demonstrate how the Val deficiency was overcome in this same C/PM diet with L-Val supplementation at the expense of an inert filler. The Val deficiency, and its subsequent correction via L-Val supplementation, was further demonstrated when comparing those responses against the growth obtained by broilers fed a nutritionally similar CS-2-based diet. Equally as important as validating a Val deficiency with the use of this C/PM-based diet was the fact that L-Val supplementation corrected this deficiency, as judged by comparison with the CS-2-based diet. The similar responses observed between the broilers fed the CS-2 diet and those fed the nutritionally Val-adequate C/PM diet validate the ability of the latter to support adequate growth and feed efficiency. Furthermore, this diet allowed for an estimation of dietary Val needs via the dose-response methodology as in experiment 3. The ability of a C/PM-based diet to support satisfactory growth when compared with more conventional diets is in agreement with previous work that used a C/PM-based diet during Thr-based studies in broilers [14]. For that purpose, experiment 3 used this C/PM diet as a way to estimate the Val needs of broilers as a proportion of dietary Lys.
Experiment 3: Val Needs Relative to Lys
The third study was designed to extrapolate a dietary Val value expressed relative to Lys, therefore expressing its requirement by using the ideal protein concept. Because of the lack of data regarding Val nutritional needs and the fact that its nutritional adequacy is always met by the inclusion of proteinaceous feed ingredients such as soybean meal, it was the objective of this study to obtain such a ratio, foreseeing its practicality and applicability in the industry. For that purpose, the C/PM-based diet formulated to obtain this ratio was set to meet or exceed nutrient recommendations [9] for all limiting amino acids involved, except for Val. Actual total Val analysis of the experimental basal diet showed that the C/PM diet used for titration was deficient in dietary Val (0.66% total Val; Table 1). The calculated digestible Val value (0.59%) matches the reported total Val value of the experimental C/PM diet.
Results for BW gain showed how a quadratic response was observed with dietary Val (Table 4). Regression analysis revealed that a Val-to-Lys ratio of 78 was optimal for maximizing BW gain under these experimental conditions (Table 5). Baker et al. [15] reported a similar Val-to-Lys ratio (77.5), using BW gain and feed efficiency as evaluation criteria. However, it should be noted that Baker et al. used a different broiler strain cross and estimated this ratio at a younger age. Mack et al. [16] fed graded levels of Val, among other amino acids, and estimated an ideal ratio of Val to Lys of 81. Although the work by Mack et al. closely resembled the age used during our experiment, the bird strain used did not, and that may explain the slight difference in ratio. Feed conversion was improved and displayed a linear effect with increasing Val supplementation (Table 4). As expected, increased dietary Val supplementation led to a linear effect for Val intake. No effect derived from dietary Val status was observed for the incidence of mortality. After processing the broilers, a linear increase with Val supplementation was observed for carcass weight, but not yield (Table 6). Perhaps this effect closely reflects the response observed for BW gain. In contrast to the abdominal fat responses observed in the first study, no effect was observed for abdominal fat weight or percentage caused by dietary Val (Table 6). Removal of breast muscles showed numerous effects attributable to dietary Val (Table 7). Quadratic effects for both types of pectoral muscles (fillets: pectoralis major; tenders: pectoralis minor) and their composite were seen. Yield values displayed significant quadratic responses for fillets, tenders, and breast meat yield only when proportionate to carcass weight. Total breast meat yield value expressed relative to the live BW reached borderline significance (P = 0.07), and its quadratic response yielded a Val optimization ratio to Lys similar to that seen when expressed relative to the carcass weight. The absolute weight of these muscles and their composite was maximized with Val-to-Lys ratios between 76 and 77, whereas their yield was optimized between 72 and 74 (Table 5). A similar effect was observed previously [16], in which Val was optimized with a lower amount for breast meat yield compared with BW gain and feed conversion. Furthermore, the resultant Val-to-Lys ratio of Mack et al. [14] was considerably less for breast meat yield because they reported a higher need for Lys for optimization of breast meat yield. This is not unusual because of the demanding role of Lys in protein accretion and maintenance in the breast muscle of chickens [17, 18]. Thus, the Lys roles for maintenance change considerably when comparing growth vs. breast meat, but the Val maintenance need for breast meat tissue did not appear to increase proportionally to the Lys needs, perhaps explaining why the resultant Val-to-Lys ratios were lower when considering breast meat yield as the evaluation criterion.
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Table 5. Quadratic regression equations of measurements having significant quadratic response by broiler males after receiving progressive dietary levels of Val
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It can be concluded that Val is likely the fourth limiting amino acid in C/SBM-based diets, and particular attention should be given to the resultant dietary Val level when attempting to reduce CP. Furthermore, Val needs may be of greater relevance in certain regions of the world where the use of animal by-products in the manufacture of poultry feeds is prohibited. We demonstrated that if a certain dietary Val level is not considered in the formulation, the efficiency of a diet could lead to a decrease in production. A Val-to-Lys ratio of 78 (0.74% digestible Val; 0.82% total Val) is recommended for this broiler strain under this time frame, closely agreeing with the recommendations by Baker et al. [15].
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CONCLUSIONS AND APPLICATIONS
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- Dietary Val is the likely fourth limiting amino acid in C/SBM-based diets and C/PM-based diets.
- Based on the present results, the Val-to-Lys recommendation is 78 (0.74% digestible Val; 0.82% total Val) for high-yielding Ross x Ross 708 male broilers from 21 to 42 d of age.
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FOOTNOTES
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1 This is journal article number J11064 from the Mississippi Agricultural and Forestry Experiment Station, supported by MIS-322220. Use of trade names in this publication does not imply endorsement by the Mississippi Agricultural and Forestry Experiment Station or USDA-Agricultural Research Service of the products or of similar ones not mentioned. 
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REFERENCES AND NOTES
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- Kidd, M. T. and L. Hackenhaar. 2005. Dietary threonine for broilers: Dietary interactions and feed additive supplement use. CAB Rev. 1. No. 005.
- Edmonds, M. S., C. M. Parsons, and D. H. Baker. 1985. Limiting amino acids in low-protein corn-soybean meal diets fed to growing chicks. Poult. Sci. 64:1519–1526.[ISI]
- Mendoca, C. X., and L. S. Jensen. 1989. Influence of valine level on performance of older broilers fed low protein diet supplemented with amino acids. Nutr. Rep. Int. 40:247–252.[ISI]
- Han, Y., H. Suzuki, C. M. Parsons, and D. H. Baker. 1992. Amino acid fortification of a low protein corn-soybean meal diet for maximal weight gain and feed efficiency of the chick. Poult. Sci. 71:1168–1178.[ISI][Medline]
- Fernandez, S. R., S. Aoyagi, Y. Han, C. M. Parsons, and D. H. Baker. 1994. Limiting order of amino acids in corn and soybean meal for growth of the chick. Poult. Sci. 73:1887–1896.[ISI][Medline]
- Corzo, A., E. T. Moran Jr., and D. Hoehler. 2004. Valine needs of male broilers from 42 to 56 days of age. Poult. Sci. 83:946–951.[Abstract/Free Full Text]
- Thronton, S. A., A. Corzo, G. T. Pharr, W. A. Dozier III, D. M. Miles, and M. T. Kidd. 2006. Valine requirements for immune and growth responses in broilers from 3 to 6 weeks of age. Br. Poult. Sci. 47:190–199.[CrossRef][ISI][Medline]
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- SAS Institute. 2000. SAS Proprietary Software, Release 8.1. SAS Inst. Inc., Cary, NC.
- Ajinomoto Heartland Inc., Chicago, IL.
- Llames, C. R., and J. Fontaine. 1994. Determination of amino acids in feeds. Collaborative Study. J. AOAC Int. 77:1362–1402.[ISI]
- Taylor, W. M., and M. L. Halperin. 1975. Effect of valine on the control of fatty acid synthesis in white adipose tissue of the rat. Can. J. Biochem. 53:1054–1060.[ISI][Medline]
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- Baker, D. H., A. B. Batal, T. M. Parr, N. S. Augspurger, and C. M. Parsons. 2002. Ideal ratio (relative to lysine) of tryptophan, threonine, isoleucine, and valine for chicks during the second and third weeks posthatch. Poult. Sci. 81:485–494.[Abstract/Free Full Text]
- Mack, S., D. Bercovici, G. DeGroote, B. Leclercq, M. Lippens, M. Pack, J. B. Schutte, and S. Van Cauwenberghe. 1999. Ideal amino acid profile and dietary lysine specification for broiler chickens of 20 to 40 days of age. Br. Poult. Sci. 40:257–265.[CrossRef][ISI][Medline]
- Tesseraud, S., M. Larbier, A. M. Chagneau, and P. A. Geraert. 1992. Effect of dietary lysine on muscle protein turnover in growing chickens. Reprod. Nutr. Dev. 32:163–171.[CrossRef][ISI][Medline]
- Tesseraud, S., S. Temim, E. Le Bihan-Duval, and A. M. Chagneau. 2001. Increased responsiveness to dietary lysine deficiency of pectoralis major muscle protein turnover in broilers selected on breast development. J. Anim. Sci. 79:927–933.[Abstract/Free Full Text]
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SUMMARY
DESCRIPTION OF PROBLEM
