Amino Acids Nutrition and Health in Farm Animals

A special issue of Animals (ISSN 2076-2615). This special issue belongs to the section "Animal Nutrition".

Deadline for manuscript submissions: 31 October 2026 | Viewed by 6756

Special Issue Editor


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Guest Editor
State Key Laboratory of Animal Nutrition and Feeding, China Agricultural University, Beijing 100193, China
Interests: animal nutrition physiology; regulation of nutrition and metabolism; the interaction between intestinal microorganisms and intestinal epithelial cells; immunity and intestinal health

Special Issue Information

Dear Colleagues,

Protein nutrition is critical for the health of farm animals due to multiple functional roles in cell proliferation, intestinal health, and the maintenance of biological processes, such as immune response, embryo attachment and implantation, fetal survival and development, disease recovery, and the production of meat, milk, and eggs. It is generally believed that peptides and amino acids are the predominant mediators that confer to these functions in humans and animals.

Original papers, including research papers and review papers related to protein, peptide, amino acids, and the nutrition and health of farm animals, are welcome to be submitted to this Special Issue. All submitted papers will be reviewed according to the Animals journal guidelines.

Prof. Dr. Zhenlong Wu
Guest Editor

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Keywords

  • protein
  • peptide
  • amino acids
  • intestinal health
  • immune response
  • oxidative stress
  • feeding and management
  • metabolism

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Published Papers (5 papers)

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Research

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21 pages, 1742 KB  
Article
Effects of Methionine Supplementation in Low-Protein Diets on Growth Performance, Fur Quality, Blood Indices, and Intestinal Microbiota of Blue Foxes (Vulpes lagopus) During the Fur-Growing Period
by Huali Shi, Sibo Cheng, Zhongbo Sun, Chengkai Yang, Xinyan Cao, Chongshan Yuan and Aiwu Zhang
Animals 2026, 16(4), 573; https://doi.org/10.3390/ani16040573 - 12 Feb 2026
Viewed by 581
Abstract
This study evaluated the effects of supplementing methionine to a low-protein diet on nutrient digestibility, nitrogen (N) metabolism, growth performance, serum biochemical parameters, fur quality, and intestinal microbiota composition in blue foxes (Vulpes lagopus) during the fur-growing period. Fifty 17-week-old blue [...] Read more.
This study evaluated the effects of supplementing methionine to a low-protein diet on nutrient digestibility, nitrogen (N) metabolism, growth performance, serum biochemical parameters, fur quality, and intestinal microbiota composition in blue foxes (Vulpes lagopus) during the fur-growing period. Fifty 17-week-old blue foxes were randomly allocated to five experimental groups (n = 10 per group). The control group received a diet containing 28% crude protein (CP), while the experimental groups were fed a 22% CP diet supplemented with 0%, 0.35%, 0.55%, or 0.75% methionine on a dry matter (DM) basis, designated as M0, M1, M2, and M3, respectively. Results demonstrated that the final body weight (FW), total weight gain (TW), and average daily gain (ADG) of the M3 group were comparable to the control group (p > 0.05). Methionine supplementation significantly enhanced fur quality and stimulated hair follicle development (p < 0.05). Although the reduction in dietary protein level led to decreased N intake and fecal N excretion, the M2 and M3 groups exhibited significantly higher N retention compared to the control, M0, and M1 groups (p < 0.05). Regarding nutrient digestibility, the M2 and M3 groups showed higher DM digestibility (p < 0.05), while the M3 group maintained organic matter (OM) digestibility comparable to the control group (p > 0.05). The highest CP digestibility was observed in the M3 group (p < 0.05). Additionally, ether extract (EE) digestibility was significantly improved in the methionine-supplemented groups (M1–M3) relative to the control (p < 0.05). Serum analysis revealed dose-dependent increases in total protein (TP), albumin (ALB), and high-density lipoprotein (HDL) concentrations in the M2 and M3 groups. Conversely, low-density lipoprotein (LDL) levels were elevated in these groups compared to the control and M0 groups (p < 0.05). Liver function parameters were also significantly improved in the M2 and M3 groups (p < 0.05). Furthermore, methionine supplementation enhanced the diversity and richness of the intestinal microbiota and altered its composition at the phylum and genus levels. In conclusion, supplementing low-protein diets with methionine can maintain growth performance, improve fur quality, enhance nutrient utilization efficiency, and support intestinal microbiota homeostasis in blue foxes. The optimal supplementation level is 0.75%, resulting in a total dietary methionine concentration of 1.1% on a DM basis. Full article
(This article belongs to the Special Issue Amino Acids Nutrition and Health in Farm Animals)
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26 pages, 836 KB  
Article
Establishment of an Amino Acid Nutrition Prediction Model for Laying Hens During the Brooding and Early-Growing Period
by Jiatong Li, Meng Hou, Weidong Yuan, Xin Zhang, Xing Wu, Yijie Li, Ruirui Jiang, Donghua Li, Yujie Guo, Xiangtao Kang, Yujie Gong, Yongcai Wang and Yadong Tian
Animals 2025, 15(21), 3178; https://doi.org/10.3390/ani15213178 - 31 Oct 2025
Cited by 1 | Viewed by 1193
Abstract
The aim of this study was to develop a dynamic factorial model for predicting amino acid requirements in Hy-Line Gray laying hens during critical early growth stages (0–84 days), addressing the need for precision feeding in modern poultry production systems. Methods: Four sequential [...] Read more.
The aim of this study was to develop a dynamic factorial model for predicting amino acid requirements in Hy-Line Gray laying hens during critical early growth stages (0–84 days), addressing the need for precision feeding in modern poultry production systems. Methods: Four sequential trials were conducted. In Trial 1, growth curves and protein deposition equations were developed based on fortnightly body composition analyses, with parameters evaluated using the Akaike and Bayesian information criteria (AIC and BIC). In Trial 2, the carcass and feather amino acid profiles were characterized via HPLC. And established the amino acid composition patterns of chicken feather protein and carcass protein (AAF and AAC). In Trial 3, maintenance requirements were quantified through nitrogen balance studies, and in Trial 4, amino acid patterns of feather protein (APD) and apparent protein digestibility (ADD) were established using an endogenous indicator method. These datasets were integrated through factorial modeling to predict age-specific nutrient demands. Results: The developed model revealed the following quantitative requirements (g/day) for 18 amino acids across developmental stages: aspartic acid (0.1–0.863), glutamic acid (0.170–1.503), serine (0.143–0.806), arginine (0.165–0.891), glycine (0.258–1.279), threonine (0.095–0.507), proline (0.253–1.207), alanine (0.131–0.718), valine (0.144–0.737), methionine (0.023–0.124), cysteine (0.102–0.682), isoleucine (0.086–0.458), leucine (0.209–1.067), phenylalanine (0.086–0.464), histidine (0.024–0.133), lysine (0.080–0.462), tyrosine (0.050–0.283), and tryptophan (0.011–0.060). The model demonstrated strong predictive validity throughout the 12-week growth period. Conclusion: This integrative approach yielded the first dynamic requirement model for Hy-Line Gray layers during early development. The factorial framework enables precise adjustment of amino acid provisions to match changing physiological needs and has high potential value in optimizing feed efficiency and supporting sustainable layer production practices. Full article
(This article belongs to the Special Issue Amino Acids Nutrition and Health in Farm Animals)
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18 pages, 2479 KB  
Article
Dietary Supplementation with Fermented Milk Improves Growth Performance and Intestinal Functions in Intrauterine Growth-Restricted Piglets
by Qing Yang, Lu Cui, Yang Yang, Ying Yang, Zhaolai Dai and Zhenlong Wu
Animals 2025, 15(10), 1367; https://doi.org/10.3390/ani15101367 - 9 May 2025
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Abstract
Intrauterine growth restriction (IUGR) commonly occurs in pigs and poses a significant challenge to the swine industry. This study investigated the effect of fermented milk on growth performance and intestinal health in IUGR-affected piglets. A total of 24 28-day-old weaned piglets with IUGR [...] Read more.
Intrauterine growth restriction (IUGR) commonly occurs in pigs and poses a significant challenge to the swine industry. This study investigated the effect of fermented milk on growth performance and intestinal health in IUGR-affected piglets. A total of 24 28-day-old weaned piglets with IUGR were randomly assigned to a corn-soybean basal diet (control) or a basal diet mixed with fermented milk (3:1 w/v, treatment). The results showed that fermented milk increased the average daily gain and decreased the feed-to-gain ratio (p < 0.05). Fermented milk increased the villus height in the duodenum and decreased the jejunal crypt depth (p < 0.05). Pigs in the treatment showed higher activities of lipase, α-amylase, and sucrase in the duodenum, along with an elevation in jejunal sucrase activity (p < 0.05). The ileal glutathione concentration was increased by the treatment (p < 0.05). Moreover, fermented milk upregulated the protein expression of occludin and claudin-3 while decreasing the gene expression of interleukin 1 beta, interleukin 6, and tumor necrosis factor αlpha in the jejunum (p < 0.05). Collectively, these results indicate that dietary supplementation with fermented milk significantly improved growth performance through the enhancement of intestinal functions in IUGR piglets, highlighting the potential of fermented milk as a nutritional strategy to improve postnatal growth in IUGR piglets. Full article
(This article belongs to the Special Issue Amino Acids Nutrition and Health in Farm Animals)
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14 pages, 8085 KB  
Article
Methionine Antagonizes Liver and Kidney Antioxidant Function Damage in Heat-Stressed Rex Rabbits
by Shu Li, Xiaosong Wang, Gongyan Liu, Lei Liu and Fuchang Li
Animals 2025, 15(8), 1148; https://doi.org/10.3390/ani15081148 - 16 Apr 2025
Viewed by 1858
Abstract
Heat stress triggers systemic oxidative stress that compromises physiological homeostasis. This study evaluated methionine’s effects on hepatic and renal antioxidant capacity in heat-stressed Rex rabbits. Rabbits were divided into five groups (30 replicates/group): control (20–25 °C, basal diet), heat stress (HS, 30–34 °C, [...] Read more.
Heat stress triggers systemic oxidative stress that compromises physiological homeostasis. This study evaluated methionine’s effects on hepatic and renal antioxidant capacity in heat-stressed Rex rabbits. Rabbits were divided into five groups (30 replicates/group): control (20–25 °C, basal diet), heat stress (HS, 30–34 °C, basal diet), and HS +0.15%, 0.3%, or 0.45% methionine-supplemented groups. After 21 days, serum, skin, liver, and kidney samples were analyzed for biochemical parameters, oxidative stress markers, and gene expression. Results showed that 0.15–0.3% methionine supplementation under heat stress increased methionine apparent digestibility and suppressed amino acid catabolism; decreased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels; reduced skin malondialdehyde (MDA) and elevated (MSRA) activity; attenuated hepatic central venous congestion and renal tubular vacuolization; enhanced hepatic superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities (0.3% group); and modulated antioxidant gene expression via Nrf2/HO-1 and Nrf2/NQO1 pathways. Pathological analysis confirmed reduced fibrosis and cellular damage in liver/kidney tissues. Optimal methionine supplementation (0.3%) effectively mitigated heat-induced oxidative organ damage by enhancing endogenous antioxidant defenses and regulating redox-sensitive signaling pathways. These findings provide a nutritional strategy for alleviating heat stress-related metabolic disorders in rabbits. Full article
(This article belongs to the Special Issue Amino Acids Nutrition and Health in Farm Animals)
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Other

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13 pages, 3518 KB  
Technical Note
Physics-Informed Neural Networks for Modeling Postprandial Plasma Amino Acids Kinetics in Pigs
by Zhangcheng Li, Jincheng Wen, Zixiang Ren, Zhihong Sun, Yetong Xu, Weizhong Sun, Jiaman Pang and Zhiru Tang
Animals 2026, 16(4), 634; https://doi.org/10.3390/ani16040634 - 16 Feb 2026
Viewed by 514
Abstract
Postprandial plasma amino acid (AA) kinetics serve as essential indicators of digestive efficiency and systemic metabolic status in pigs. Traditional kinetic analysis relies on Non-Linear Least Squares (NLS) regression using compartmental models, yet these methods typically demand repeated blood sampling and precise initialization [...] Read more.
Postprandial plasma amino acid (AA) kinetics serve as essential indicators of digestive efficiency and systemic metabolic status in pigs. Traditional kinetic analysis relies on Non-Linear Least Squares (NLS) regression using compartmental models, yet these methods typically demand repeated blood sampling and precise initialization to ensure convergence. In this study, we developed a Physics-Informed Neural Network (PINN) framework by integrating mechanistic Ordinary Differential Equations (ODEs) directly into the deep learning loss function. The framework was evaluated using a benchmark dataset. Specifically, we performed a retrospective analysis by downsampling the original high-frequency data to simulate dense and sparse sampling strategies. The results demonstrate that while both models exhibit high fidelity under dense sampling, PINN maintains superior robustness and predictive accuracy under data-constrained conditions. Under the sparse sampling scenario, PINN reduced the Root Mean Square Error (RMSE) compared to NLS in key metabolic profiles, such as Methionine in the FAA group (p < 0.01) and Lysine in the HYD group (p < 0.05). Unlike NLS, which is sensitive to initial guesses, PINN successfully utilized physical laws as a regularization term to robustly solve the inverse problem, demonstrating superior parameter identification stability and predictive consistency under data-constrained conditions compared to NLS. We concluded that the PINN framework provides a reliable and consistent alternative for modeling the AA dynamics. In the future, it may be possible to reconstruct highly accurate physiological trajectories under optimized sparse sampling conditions. Full article
(This article belongs to the Special Issue Amino Acids Nutrition and Health in Farm Animals)
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