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ANIMAL NUTRITION |
* University of Missouri, Columbia 65211 and
and
Novus International Inc., St. Louis, MO 63304
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionImplicationsLiterature Cited |
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0.09) and G:F (P 0.05). Three different methods were used to estimate the optimal TID SAA:LYS ratio for each experiment. The two-slope broken-line regression model, x-intercept value of the broken-line and quadratic curve, and 95% of upper asymptote across the four experiments indicated that the average optimal TID SAA:LYS ratios were 59.3, 60.1, and 57.7% for ADG and 60.6, 61.7, and 60.1% for G:F, respectively. Thus, the optimal TID SAA:LYS ratio for 8- to 26-kg pigs based on the average value of these three estimates was 59.0% for ADG and 60.8% for G:F.
Key Words: Methionine • Growth • 2-Hydroxy-4-(methylthio)Butanoic Acid • Pigs • Sulfur Amino Acid
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionImplicationsLiterature Cited |
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; Knight et al., 1998; Jansman and de Jong, 1999). Based on N balance studies, HMTBA was reported to have lower bioefficacy than DL-Met (Schmidt et al., 1998; Schindler et al., 2000; Kim et al., 2005); however, in each of these reports, the results were analyzed on a nonequimolar basis, either assuming a lower molar efficacy for HMTBA than DL-Met or not accounting for differences in the DM content. Moreover, the results in these reports were contradictory to the findings of Romer and Abel (1999), in which HMTBA and DL-Met were found to have the equal bioefficacy based on N balance for pigs and chickens when both Met sources were supplemented on an equimolar basis. Thus, if the nursery pig can utilize HMTBA and DL-Met with equal effectiveness, one would expect that the estimated sulfur AA (SAA) requirement of the pig would be the same regardless of Met source.
The current available research evaluating the SAA requirement of nursery pigs is limited to one Met source (Chung and Baker, 1992b; Owen et al., 1995a, b; Matthews et al., 2001), with some disparity in the estimates for the weight ranges as defined by NRC (1998). Furthermore, there are limited data on the SAA needs of modern lean-genotype pigs. Recent experiments conducted by our laboratory (Kendall et al., 2002; Gaines et al., 2003) have demonstrated that modern lean-genotype nursery pigs have a higher true ileal digestible (TID) Lys requirement than suggested by current NRC (1998) estimates. Thus, the objective of this research was to determine the ideal ratio of TID SAA:Lys (SAA:LYS) in modern lean-genotype nursery pigs at two different BW ranges using both DL-Met and HMTBA as Met sources.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionImplicationsLiterature Cited |
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On d 14 after weaning, a total of 1,549 nursery pigs (Triumph 4 x PIC Camborough 22; initial BW 8.3 ± 0.08 kg) were allotted to one of nine dietary treatments in a randomized complete block design with eight replicate pens per treatment. Pigs were housed (20 to 22 pigs per pen) in an environmentally controlled research nursery facility located on a commercial farm. Pens (3.05 m x 1.82 m) were equipped with a one-cup water unit and a six-hole nursery feeder. Body weights and feed intakes were recorded at trial initiation (d 0) and termination (d 21). The basal diet (Diet 1) was a semi-complex corn-soybean meal-based diet formulated to provide 1.32% TID Lys (Table 1; as-fed basis), which should have been marginally limiting based on a requirement estimate of 1.42% TID Lys for 7- to 14-kg pigs of this genotype (Gaines et al., 2003). The basal diet contained 0.26% L-Lys·HCl with no supplemental HMTBA or DL-Met (47.7% TID SAA:LYS ratio). Diets 2 to 9 consisted of the basal diet supplemented on an as-fed basis with four equimolar levels of DL-Met or HMTBA (HMTBA was supplied in Exp. 1 to 4 by 88% aqueous solution of ALIMET feed supplement; Novus International, Inc., St. Louis, MO) that corresponded to TID SAA:LYS ratios of 52.7, 57.7, 62.7, and 67.7%, respectively.
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On d 21 after weaning, a total of 330 nursery pigs (Triumph 4 x PIC Camborough 22; initial BW 11.4 ± 0.10 kg) were allotted to one of nine dietary treatments in a randomized complete block design with six replicate pens per treatment. Pigs were housed (five to six pigs per pen) in an environmentally controlled research nursery facility at the University of Missouri. Pens (1.20 m x 1.20 m) were equipped with a one-nipple water unit and a six-hole nursery feeder. Body weights and feed intakes were recorded on d 0 (trial initiation) and 21 (termination). The basal diet (Diet 1) was a corn-soybean meal-based diet formulated to provide 1.15% TID Lys (Table 1
), which should have been marginally limiting based on a requirement estimate of 1.32% TID Lys (Kendall et al., 2002; Fu et al., 2004) for 11- to 29-kg pigs of this genotype. The basal diet contained 0.30% L-Lys·HCl with no supplemental HMTBA or DL-Met (49% TID SAA:LYS ratio). Diets 2 to 9 consisted of the basal diet supplemented on an as-fed basis with four equimolar levels of DL-Met or HMTBA that corresponded to TID SAA:LYS ratios of 54, 59, 64, and 69%, respectively.
Experiment 3
On d 21 after weaning, a total of 1,544 nursery pigs (Triumph 4 x PIC Camborough 22; initial BW 12.4 ± 0.13 kg) were allotted to one of nine dietary treatments in a randomized complete block design with eight replicate pens per treatment. Pigs were housed (20 to 23 pigs per pen) in the same facilities as Exp. 1. Body weights and feed intakes were recorded at trial initiation and termination (d 0 and 20, respectively). Dietary treatments were identical to the diets used in Exp. 2.
Experiment 4
On d 21 after weaning, a total of 343 nursery pigs (Genetiporc; initial BW 12.7 ± 0.24 kg) were allotted to one of six dietary treatments in a randomized complete block design with six replicate pens per treatment. Pigs were housed (9 to 10 pigs per pen) in an environmentally controlled research nursery facility located on a commercial farm. Pens (1.82 m x 1.52 m) were equipped with a one-nipple water unit and a six-hole nursery feeder. Body weights and feed intakes were recorded at trial initiation (d 0) and termination (d 21). The basal diet (Diet 1) was formulated to provide 1.05% TID Lys (Table 1). Based on a previous unpublished experiment by our laboratory, the Lys requirement for this genotype was determined to be 1.20% TID Lys (D. C. Kendall A. M. Gaines, and G. L. Alloe, unpublished data). Thus, the basal diet should have been marginally deficient in dietary Lys. The basal diet contained 0.34% L-Lys·HCl with no supplemental Met (49% TID SAA:LYS ratio). Diets 2 to 5 consisted of the control diet supplemented on an as-fed basis with four levels of DL-Met that corresponded to TID SAA:LYS ratios of 54, 59, 64, and 69%, respectively. Diet 6 was the basal diet supplemented on an as-fed basis with one equimolar level of HMTBA to satisfy 59% TID SAA:LYS ratio.
The University of Missouri-Columbia Animal Care and Use Committee reviewed and approved all animal protocols in the present research.
Diet Analyses
Amino acid composition of the diets was determined after acid hydrolysis, whereas total SAA content was determined after performic acid oxidation, and Trp content was determined after alkaline hydrolysis (AOAC, 1995). Dietary HMTBA was analyzed at the feed analytical laboratory of Novus International, Inc. using the HPLC method adapted from Ontiveros et al. (1987). The dietary addition of the Met sources was verified by laboratory analysis, in which the analyzed supplemental DL-Met and HMTBA had a correlation >95% with the theoretical calculations across experiments.
Statistical Analyses
Data were subjected to analysis of variance using the GLM procedures of SAS (SAS Inst., Inc., Cary, NC). With the exception of Exp. 4, data were analyzed for Met source, TID SAA:LYS ratio, and source x ratio interactions. This analysis did not include the basal diet because it did not contain supplemental Met. The initial analysis indicated that there were no Met source or interaction effects; thus, these variables were not included in the final statistical model. The final statistical model included the effects of weight block and TID SAA:LYS ratio, with pen as the experimental unit. In all experiments, orthogonal polynomial contrast coefficients were used to determine linear and quadratic effects of increasing TID SAA:LYS ratio. Because there were no three-way interactions of Met source, SAA:LYS ratio, or experiment, data from Exp. 2 and 3 were pooled for statistical analysis. In Exp. 4, there was no differences between Met sources at the 59% TID SAA:LYS ratio, and data were pooled for statistical analysis. Three different methods were used to estimate the optimal TID SAA:LYS ratio for each experiment. The first estimate was obtained using the two-slope broken-line regression model as described by Robbins (1986). The second estimate was determined by establishing the first point where the quadratic curve intersected the broken-line (above the breakpoint) after modifying the methodology of Parr et al. (2003). The methodology was modified using the two-slope broken-line regression model because this statistical method provided a better fit than the one-slope broken-line regression model. The third estimate was based on the 95% upper asymptote (95% quadratic maximum) calculated from the quadratic model.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionImplicationsLiterature Cited |
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Increasing the TID SAA:LYS ratio (47.7 to 67.7%) improved ADG (quadratic; P = 0.09) and G:F (quadratic; P = 0.05) during the 21-d period (Table 2). There were no differences in ADFI with increasing TID SAA:LYS ratio (P = 0.33). Based on estimates using the two-slope broken-line model, the first x-intercept value of the broken-line and quadratic model, and 95% of upper asymptote, the optimal TID SAA:LYS ratio estimate for ADG was 59.2, 60.2, and 57.3%, respectively (Table 3), whereas for G:F, the optimal ratios were 59.5, 61.0, and 58.0%, respectively (Table 3).
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As previously mentioned, because there was no three-way interaction of Met source, SAA:LYS ratio, or experiment, data from Exp. 2 and 3 were pooled for statistical analysis. Furthermore, pigs used in both experiments were of the same genotype and were housed at similar stocking densities. Increasing the TID SAA:LYS ratio increased ADG (quadratic; P < 0.01) and improved G:F (quadratic; P < 0.001; Table 4). There was no difference in ADFI with increasing TID SAA:LYS ratio (P = 0.46). Based on estimates using the two-slope broken-line model, the first x-intercept value of the broken-line and quadratic model, and 95% of upper asymptote, the optimal TID SAA:LYS ratio estimate for ADG was 59.1, 60.0, and 58.7%, respectively (Figure 1; Table 3). For G:F, the optimal ratios were 60.6, 61.5, and 61.3%, respectively (Figure 2; Table 3).
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In Exp. 4, there was no difference in growth performance between Met sources at 59% TID SAA:LYS ratio (P = 0.16); therefore, the data were pooled for statistical analysis. Increasing the TID SAA:LYS ratio increased ADG (quadratic; P = 0.05) and improved G:F (quadratic; P = 0.03; Table 5). There was no difference in ADFI with increasing TID SAA:LYS ratio (P = 0.30). Based on estimates using the two-slope broken-line model, the first x-intercept value of the broken-line and quadratic model, and 95% of upper asymptote, the optimal TID SAA:LYS ratio estimate for ADG was 59.7, 60.2, and 57.0% respectively (Table 3), whereas for G:F, the optimal ratios were 61.6, 62.5, and 61.0%, respectively (Table 3).
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Based on the average value of estimates using the two-slope broken-line model, the first x-intercept value of the broken-line and quadratic model, and 95% of upper asymptote, the optimal TID SAA:LYS estimate for ADG was 59.3, 60.1, and 57.7%, respectively (Table 3). For G:F, the optimal ratios were 60.6, 61.7, and 60.1%, respectively. Using the average value of these objective estimates, the optimal TID SAA:LYS ratio for 8- to 26-kg pigs was 59.0% for ADG and 60.8% for G:F.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionImplicationsLiterature Cited |
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, using feather meal-corn-soybean meal-dried whey diets, suggested both 5- to 10-kg and 10- to 20-kg pigs have the same true digestible Met and total SAA requirements (i.e., 0.29 and 0.58%, respectively) and implied that the ideal ratio of SAA:LYS seems to increase from approximately 50% in 5- to 10-kg pigs to approximately 60% in 10- to 20-kg pigs. These findings in the 10- to 20-kg pig agree with the current research using practical corn-soybean meal-AA-supplemented diets. Based on the existing data, it seems that the ratio is <60% for younger or lighter pigs. Owen et al. (1995a), using starter pig diets containing blood products, reported that the segregated early-weaned pig (5- to 10-kg) required approximately 0.41 to 0.42% total dietary Met (0.36 to 0.37% apparent digestible) to maximize growth performance from d 0 to 14 after weaning. When these results are expressed on a ratio relative to Lys, a Met:Lys ratio of 26% is obtained. Assuming that Cys can furnish up to 50% of the young pig’s total SAA requirement (Chung and Baker, 1992c), this value corresponds to a SAA:LYS ratio of 52%. Additional work by Owen et al. (1995b) evaluating Met requirements in 3.5- to 12-kg nursery pigs fed diets containing spray-dried blood indicated that 0.48 to 0.52% total dietary Met (0.44 to 0.48% apparent digestible) or 27.5% of total Lys is needed to maximize growth performance. This corresponds to a SAA:LYS ratio of 55%, which is in close agreement with the earlier work from the same laboratory. Similarly, Matthews et al. (2001) using complex nursery diets determined that the SAA requirement of pigs from 5-to 10-kg was 0.64% on an apparent digestible basis, which, based on NRC (1998) Lys requirement estimates for this weight-range pig, corresponds to a 57.7% SAA:LYS ratio. The aforementioned estimates are intermediate to those proposed by Chung and Baker (1992b) and the current research.
Based on the known TID Lys requirement (Kendall et al., 2002; Gaines et al., 2003; Fu et al., 2004) and the TID SAA:LYS ratio estimated in the current research, it would seem that the SAA requirement is greater in today’s modern genotype pig. For example, the current research suggest that the TID SAA requirement for 12-to 26-kg pigs (Triumph-4 x Camborough-22) is approximately 0.78% (based on 1.32% TID Lys requirement and 59% TID SAA:LYS ratio), whereas the NRC (1998) estimate for pigs of this weight range is 0.58%. This finding agrees with our previous report, in which TID SAA requirement for 13- to 25-kg pigs is 0.73 to 0.77% for maximal ADG and 0.80 to 0.83% for optimal feed efficiency (Gaines et al., 2004). Similarly, if one compares modern pigs of a different genotype (i.e., Genetiporc), the TID SAA requirement (i.e., 0.71% based on 1.20% TID Lys requirement and 59% TID SAA:LYS ratio) would be greater than NRC (1998) estimates, which is consistent with the TID SAA requirement estimation of Genetiporc pigs by Schneider et al. (2004). The current research data also suggest that, similar to other AA such as Lys, differences in the SAA requirement may exist across today’s modern genotypes of pigs. In light of a greater SAA and Lys requirement in the modern lean-genotype pig, it is likely that the optimal SAA:LYS ratio has not changed much. Rather, the disparity between the current research and previous reports could be attributed to analytical problems in SAA analysis, lack of information regarding Met and Cys bioavailability in basal diets, or differences in feed ingredients used for studies (Chung and Baker, 1992b). Furthermore, differences could be attributed to how the SAA:LYS ratio was calculated or the methodology used to determine the estimated requirement.
A fundamental tenet to establish an ideal pattern among AA is that the reference AA, Lys, must be marginally deficient and in the linear portion of the response curve. With the exception of data by Owen et al. (1995b), one possible criticism of previous reports that have attempted to define an optimal SAA:LYS ratio is that the actual Lys requirement of the pigs used was not defined or shown to be limiting. Therefore, Lys intake could have exceeded the requirement, which would result in an inaccurate calculation of the minimum SAA:LYS ratio. In the present research, the Lys requirement was defined for the genotype, weight, and facility location (Kendall et al., 2002; Gaines et al., 2003; Fu et al., 2004). To ensure that diets were marginally deficient in Lys, dietary Lys was decreased by 8% in Exp. 1 and by 12% in Exp. 2, 3, and 4 below the established requirement. Furthermore, the current research used three different statistical methodologies (i.e., two-slope broken-line model, the first x-intercept value of the broken-line and quadratic model, and 95% of upper asymptote) to determine the optimal SAA:LYS ratio. In other SAA research, estimates were determined using either only an empirical estimate (Chung and Baker, 1992b), inflection point analysis (Owen et al., 1995a, b), or two-slope broken-line regression analysis (Matthews et al., 2001). In the current research, use of the three different methodologies yielded similar estimates for the optimal SAA:LYS ratio (Table 3). Furthermore, the current research used corn-soybean meal-AA-supplemented diets, which from a practical point of view allowed for economic comparisons. Interestingly, economic comparisons yielded similar estimates to the three different statistical methodologies used, which indicated that the optimal SAA:LYS ratio for 8- to 26-kg nursery pigs was approximately 60%. This finding was in agreement with a recent literature review by Peak (2005), in which the TID SAA:LYS ratio was suggested to be 60 to 62% for modern genotypic nursery and growing pigs. Chung and Baker (1992c) reported that in the dietary formulation of young pigs, no more than 50% of total SAA requirement could be furnished by Cys. By using the indicator AA oxidation technique, Shoveller et al. (2003) found that Cys can replace 40% of the Met requirement if Met is meeting 100% of the SAA requirement, and dietary Cys was equally effective in sparing dietary Met, whether fed enterally or parenterally for young pigs. Roth and Kirchgessner (1989) and Kirchgessner et al. (1994) suggested that optimal growth performance is obtained only when Met provides >50% of the SAA requirement for growing pigs; however, Curtin et al. (1952) estimated that 53% of SAA requirement could be supplied by Cys in weanling pig diets, and Baker et al. (1969) indicated that under ad libitum feeding conditions, the Cys replacement value was 56% for maximal weight gain. In the basal diets of our current studies, the TID Met:Cys ratios were 52:48 in Exp. 1, 48:52 in Exp. 2 and 3, and 49:51 in Exp. 4, respectively. Based on the existing data, there is considerable disparity with respect to the Cys replacement value. Thus, future research should be continued in this area because of the effect it may have on estimation of the SAA requirement.
There has been considerable debate over the biological efficacy of HMTBA relative to DL-Met. In the current research, growth performance responses were similar between Met sources, as evidenced by the lack of a Met source by TID SAA:LYS ratio interaction, which indicates that HMTBA and DL-Met supply equimolar amounts of Met activity. Nonetheless, this comparison might have its limitations because the practical diet formulations used in the current study were not severely deficient in Met as in previous bioefficacy comparisons (Chung and Baker, 1992a; Knight et al., 1998; Jansman and de Jong, 1999). Consequently, our laboratory has recently conducted a large-scale research trial evaluating the two Met sources and found no differences in the biological activity of DL-Met vs. HMTBA when diets are formulated on an equimolar basis (Gaines et al., 2005). For the Gaines et al. (2005) research, nonpractical corn-soybean meal-AA-supplemented diets (i.e., diet added with 0.70% L-Lys·HCl and other synthetic AA) were used with four levels of Met supplementation below the estimated requirement. In view of these data, it is our conclusion that the SAA requirement of pigs can be determined in either practical or nonpractical type diet formulations, regardless of Met source.
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Implications |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionImplicationsLiterature Cited |
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Footnotes |
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2 Data in this paper were presented in part at 2003 ASAS National Meeting (Abstract No. 551), 2004 ASAS Midwest Meeting (Abstract No. 127), and 2005 ASAS Midwest Meeting (Abstract No. 162).
3 Correspondence: Lab 111, Anim. Sci. Res. Center (phone: 573-882-7726; fax: 573-884-6093; e-mail: alleeg{at}missouri.edu).
Received for publication November 26, 2004. Accepted for publication July 5, 2005.
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Literature Cited |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionImplicationsLiterature Cited |
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G. F. Yi, A. M. Gaines, B. W. Ratliff, P. Srichana, G. L. Allee, K. R. Perryman, and C. D. Knight Estimation of the true ileal digestible lysine and sulfur amino acid requirement and comparison of the bioefficacy of 2-hydroxy-4-(methylthio)butanoic acid and DL-methionine in eleven- to twenty-six-kilogram nursery pigs J Anim Sci, July 1, 2006; 84(7): 1709 - 1721. [Abstract] [Full Text] [PDF]
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