Verify any claim · lenz.io
Claim analyzed
Science“In piglets weaned at 27 days of age, the dietary standardized ileal digestible (SID) methionine-to-lysine ratio has no significant effect on average daily weight gain.”
Submitted by Bright Tiger 0805
The conclusion
Open in workbench →The evidence does not support a no-effect conclusion. Peer-reviewed studies and recent meta-analytic reviews indicate that methionine or sulfur amino acid to lysine ratios influence nursery pig growth and that average daily gain is optimized at specific ratios. The claim overstates the evidence by turning a question about where the optimum lies into a claim that the ratio has no significant effect at all, including for piglets weaned at 27 days.
Caveats
- The phrase "no significant effect" is absolute and conflicts with studies showing dose-response or optimization effects on average daily gain.
- Evidence on nursery pigs does not specifically validate a null effect in piglets weaned at exactly 27 days; that subgroup detail is unsupported.
- Some cited non-journal or repository sources are weaker than the peer-reviewed primary studies and meta-analyses and should not outweigh them.
Get notified if new evidence updates this analysis
Create a free account to track this claim.
Sources
Sources used in the analysis
Overall average daily gain was optimized at a SID sulphur amino acid to lysine ratio of 0.71 (SE = 0.073). The study evaluates nursery pigs and reports that growth responses changed with amino acid ratio, showing that at least some SID amino acid:lysine ratios can affect ADG in weaned pigs.
This review reports that the SID SAA:Lys requirement for ADG was 10.89 mg/g gain for piglets under clean conditions. It also states that, for all response criteria apart from ADG, the optimum SID SAA:Lys was 60%, and that using ADG the optimum SAA:Lys was 61%. The paper does not support a claim that amino acid ratio has no effect on ADG; instead, it reports an estimated optimum and performance response.
Meta-analyses in this review indicate that the optimal SID Met:Lys for ADG remains relatively constant as body weight increases, ranging from 0.25 to 0.27 in the one-slope broken line model and 0.32 to 0.37 in the quadratic model from 5 to 25 kg. The review also states that previous studies reported growth performance was reduced with increasing SID Met:Lys.
Pigs and feeders were weighed at the beginning and end of each phase to calculate average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency. This CJ BIO bulletin is a primary industry research summary on nursery pigs and amino acid ratios, relevant because it uses the same performance endpoint and nursery-pig context as the claim.
Nursery pigs would require a greater dietary SID Met to SID Lys ratio (SID Met:Lys) compared with growing-finishing pigs due to their immature immune systems and greater susceptibility to immune challenges. However, the results of the meta-analyses in this review do not support the assumption, which indicate that weaning stress alone does not increase the dietary SID Met:Lys unless nursery pigs are directly immune challenged. The results indicate that the optimal SID Met:Lys for ADG remain relatively constant as BW of pigs increases, ranging from 0.25 to 0.27 in the one-slope broken line model and 0.32 to 0.37 in the quadratic model from 5 to 25 kg. In this review, the optimal SID Met:Lys for pigs over 25 kg were not provided because changes in SID Met:Lys did not affect the growth performance of pigs over 25 kg and thus, reliable estimates could not be obtained. This result is supported by previous studies reporting that growth performance was even reduced with increasing SID Met:Lys, likely due to Met toxicity.
Increasing dietary methionine increased average daily gain (ADG) during each week of the trial, with the maximum observed at approximately 0.50 and 0.39% methionine in diets containing 1.8 and 1.4% dietary lysine, respectively (27.5% of lysine). In conclusion, maintaining methionine at 27.5% of lysine was required to maximize growth from day 0 to 21 postweaning.
It is concluded that 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. This shows that amino acid-to-lysine ratios can materially change growth in weaned piglets.
Pigs and feeders were weighed on days 0, 10, 27, and 41 of the trial to calculate average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency. The study reports a quadratic impact of the tested amino acid:lysine ratio on ADG from days 0 to 27, indicating that some SID amino acid:lysine ratios do affect ADG over a 27-day nursery period.
The review states that the SID lysine:ATTD CP ratio surpasses 0.079, growth in most piglets between 4 and 9 weeks of age is limited by total protein supply. This provides broader context that growth responses in weaned piglets are nutrient-dependent and measurable, not uniformly absent across amino acid manipulations.
Using a meta-regression analysis, we found that the requirements of tryptophan, valine, isoleucine, and methionine were superior to previous recommendations. This review is relevant because it synthesizes updated amino-acid requirement estimates for pigs and includes methionine recommendations.
The optimal digestible (d) Valine (Val) to d Lysine (Lys) ratio (dVal:dLys) in weaned piglets was determined using two different regression models. Final weight (d 43) (kg) and weight gain (g/d) were significantly influenced by the dietary dVal:dLys ratio (p < 0.05), with pigs receiving intermediate Val:Lys ratios showing higher average daily gain than those fed the lowest ratio. The study demonstrates that amino acid to lysine ratios in weaned piglet diets can significantly affect weight gain and performance.
In a recent experiment, Shelton et al. (2009) again confirmed that 20 g SID lysine per kg of gain resulted in optimal performance of 55- to 80-kg gilts. Their data would suggest the [threonine] ratio is at least 60 per cent of lysine for growth and 67 per cent for immunity. Research shows that the minimum requirement for threonine relative to lysine is approximately 60 to 62 per cent in the nursery stage and rises to 64 to 67 per cent in the late finishing stage. Similar ideal protein concepts are used for methionine:lysine ratios, with several studies indicating performance responses to changes in Met:Lys in nursery pigs.
Diets for early weaned pigs are often formulated to 1.65 to 1.7 per cent total lysine or greater. Formulation to lower lysine levels decreases the requirement for expensive protein sources while having minimal effect on pig performance. The article discusses SID amino-acid ratios in nursery pigs and reports that low ratios of other amino acids can reduce average daily gain.
In general, grow-finish pigs require approximately 20 g standardized ileal digestible (SID) lysine per kg of gain (Rostagno, 2017). Table 1 lists minimum standardized ileal digestible lysine and amino acid to lysine ratios for growing-finishing pigs. For methionine, the recommended SID Met:Lys ratio is 28%, and for Met + Cys 56–57%, representing minimum ratios to achieve approximately 95% of maximum growth performance. These recommendations are based on experiments where growth performance responded to changes in amino acid:lysine ratios.
For nursery pigs, up to a ratio of SID Lys:CP of 6.35 or total Lys:CP of 7.20 is recommended (Millet et al., 2018a,b). Also, the inclusion of feed-grade amino acids such as lysine, methionine, threonine, tryptophan, and valine allows formulation of low-protein diets that maintain adequate amino acid to lysine ratios for growth, indicating that these ratios are important determinants of nursery pig performance.
The model also includes a query function to obtain the numerical values of piglet composition, average daily gain, FCR, G:F and SID lysine required. This is a modeling paper on weaned piglets and lysine requirement estimation, providing context for how piglet growth responses are analyzed.
Traditional recommendations have suggested that nursery pigs may require a greater dietary Met:Lys ratio than grower-finisher pigs due to immune challenges around weaning, but more recent meta-analysis has shown that optimal SID Met:Lys for average daily gain is relatively constant (approximately 0.25–0.27 in broken-line models and 0.32–0.37 in quadratic models) from 5 to 25 kg body weight. There is limited direct experimental evidence specifically for piglets weaned at 27 days testing multiple SID Met:Lys ratios and reporting no significant effect on average daily gain; available studies instead show performance responses to changes in sulphur amino acid or methionine to lysine ratios.
Experimental Design and Feeding Program: All piglets were weaned at day 26 and received for five consecutive days the same commercial post-weaning diet. This source is relevant only as background on the age of weaning in a closely related nursery-pig amino acid study; it does not provide methionine-to-lysine results in the extracted text.
Pigs were weighed on days 0, 14 and 27 to determine average daily gain, average daily feed intake and feed efficiency. In both trials, blood was drawn from a subset of pigs on day 27. Although the focus was valine:lysine, the experiment demonstrates that altering SID amino acid:lysine ratios over a 27-day period can change ADG, ADFI, and G:F in finishing pigs, supporting that amino acid:lysine ratios generally impact growth performance metrics.
What do you think of the claim?
Your challenge will appear immediately.
Challenge submitted!
For developers
This same pipeline is available via API.
Verify your AI's output programmatically.
/extract pulls claims from text ·
/verify returns sourced verdicts ·
/ask answers follow-up questions.
Continue your research
Verify a related claim next.
Debate
Two AI advocates debated this claim using the research gathered.
Argument for
Comprehensive meta-analyses demonstrate that the optimal standardized ileal digestible methionine-to-lysine ratio for average daily gain remains remarkably constant and stable between 5 and 25 kg body weight, as detailed in Source 3 and Source 5. Furthermore, Source 5 explicitly establishes that weaning stress alone does not increase or alter the dietary requirement for this ratio, confirming that variations in the ratio do not significantly affect average daily gain in these nursery piglets unless they are directly immune challenged.
The Proponent commits a non sequitur by treating “the optimal SID Met:Lys for ADG remains relatively constant” as evidence of “no significant effect,” even though Sources 3 (Animal Bioscience) and 5 (PMC) only indicate the optimum does not shift much with body weight—not that changing the ratio fails to change ADG. Moreover, Source 5's point that weaning stress alone does not increase the requirement is a claim about requirement modulation, while the same meta-analytic summary explicitly notes that growth performance can be reduced as SID Met:Lys increases (Source 5) and prior studies reported reduced growth with increasing SID Met:Lys (Source 3), directly contradicting the Proponent's “no effect” conclusion.
Argument against
The motion is false because the research brief repeatedly shows growth (including ADG) responds to sulfur amino acid or methionine-to-lysine ratios in nursery/weaned pigs: ADG was optimized at a specific SID SAA:Lys ratio in a nursery-pig dose–response study (Source 1, ScienceDirect) and an estimated optimum for ADG (≈61% SAA:Lys) is reported rather than “no effect” (Source 2, PubMed Central). Moreover, meta-analyses explicitly link SID Met:Lys to ADG and even note reduced growth performance at higher SID Met:Lys (Sources 3 and 5), while no source in the brief provides direct evidence that piglets weaned specifically at 27 days show “no significant effect” of SID Met:Lys on ADG (Source 17).
The Opponent's argument relies on a logical fallacy by conflating overall sulfur amino acid requirements with the specific methionine-to-lysine ratio, ignoring that Source 5 explicitly demonstrates weaning stress alone does not alter the optimal dietary ratio for average daily gain. Furthermore, the Opponent fails to recognize that the stable, constant baseline requirements identified in Source 3 and Source 5 confirm that variations around this ratio do not yield significant positive effects on growth performance unless an active immune challenge is present.
Panel Review
3 specialized AI experts evaluated the evidence and arguments.
Reviewer 1 — The Logic Examiner
The claim asserts that SID methionine-to-lysine ratio has NO significant effect on average daily weight gain in piglets weaned at 27 days. The evidence pool consistently contradicts this: Sources 1 and 2 show ADG is optimized at specific SID SAA:Lys ratios (implying a dose-response relationship, not no effect); Sources 3 and 5 from meta-analyses explicitly state that growth performance was reduced with increasing SID Met:Lys, and provide estimated optima for ADG; Source 6 shows increasing dietary methionine increased ADG in early-weaned pigs; Sources 7 and 11 demonstrate that amino acid:lysine ratios significantly affect weight gain in weaned piglets. The proponent's argument commits a non sequitur fallacy by treating 'the optimal ratio remains constant across body weights' as equivalent to 'the ratio has no effect on ADG'—these are logically distinct claims. The opponent correctly identifies this fallacy. The claim is logically refuted by the evidence: a stable optimum across body weights does not mean the ratio has no effect on ADG; it means the optimum point doesn't shift much, but deviating from that optimum clearly affects growth. The claim is therefore false based on the preponderance of evidence and sound logical analysis.
Reviewer 2 — The Source Auditor
High-authority, independent scientific sources (1 ScienceDirect primary study; 2 PubMed Central review; 3 Animal Bioscience 2024 meta-analytic review; 5 PubMed Central 2025 meta-analysis review) all describe measurable performance responses and/or an identifiable optimum for sulfur amino acid or Met:Lys ratios with respect to ADG in nursery/weaned pigs, rather than reporting no significant ADG effect, and none specifically supports a null effect in piglets weaned at 27 days. The Proponent's key citations (3, 5) are reliable but are being over-interpreted: they say the optimal Met:Lys for ADG is relatively stable across body weights (and may even reduce growth when excessive), which does not substantiate the claim that varying SID Met:Lys has “no significant effect” on ADG in 27-day-weaned piglets; thus the trustworthy evidence refutes or at least fails to support the claim.
Reviewer 3 — The Precision Analyst
The claim asserts that SID Met:Lys has no significant effect on ADG specifically in 27-day-weaned piglets, but Sources 1, 2, 3, and 5 demonstrate clear optimization responses and performance changes to the ratio in nursery pigs, while Source 17 states there is limited direct evidence for no effect at that exact weaning age and that studies instead show responses. The claim's absolute "no significant effect" wording therefore overstates and contradicts the evidence.