This study aimed to develop a compensatory growth model using growing beef cattle by changing dietary protein and to investigate the underlying mechanisms of compensatory protein deposition in muscle tissue. Twelve Charolais bulls were randomly assigned to one of two groups with two periods: 1) a control group (CON) fed a 13% crude protein (CP) diet for 6 weeks; 2) a treatment group (REC) fed a 7% CP diet for 4 weeks (restriction period) and fed a 13% CP diet in the following 2 weeks (re-alimentation period). Growth performance, digestibility, nitrogen balance, targeted metabolomics of amino acids (AA) in plasma, and transcriptional profiling in muscle tissue were analyzed. Protein restriction decreased average daily gain (ADG; P < 0.05), while protein re-alimentation increased ADG relative to the CON (P < 0.05). Compared to the CON, REC reduced retained N (P < 0.05), and protein re-alimentation increased retained N and N utilization efficiency (P < 0.05), due to reduced urinary urea, hippuric acid, and creatinine excretions (P < 0.05). Ruminal NH₃-N in the REC was lower than that in the CON in the protein re-alimentation period (P < 0.05). However, there was no difference in microbial protein and plasma urea nitrogen concentrations. Dietary protein restriction decreased plasma valine and aspartic acid concentrations relative to the CON (P < 0.05), and increased proline and 3-methyl-L-histidine concentrations (P < 0.05). After dietary protein re-alimentation, REC increased plasma citrulline concentrations (P < 0.05). The transcriptional profiling revealed that REC upregulated the AA transporter SLC3A1, and protein re-alimentation downregulated SLC7A8 in the muscle cell membrane. Within the muscle cell, upregulated cytosolic arginine sensor for mTORC1 subunit 2 (CASTOR2) inhibited protein synthesis by inhibiting the mammalian target of rapamycin complex 1 phosphorylation in the protein restriction period, while DNA-damage-inducible transcript 4 (DDIT4) activated the mTOR signaling pathway and promoted protein synthesis in the protein re-alimentation period. In summary, the targeted metabolomics and transcriptomics analyses demonstrated that protein re-alimentation following restriction can promote protein synthesis and reduce muscle breakdown by regulating AA metabolism and functional transcripts related to AA transporters and the mTOR signaling pathway.

The use of reduced protein diets in broiler chicken production provides potential benefits for performance and environmental footprint of production. The effectiveness of β-Mannanase supplementation in wheat and soy based standard protein (SP) and reduced protein (RP) diets was tested for growth performance, nutrient utilisation and selected intestinal gene expression of broiler chickens. In a 2 × 2 factorial arrangement of treatments, two main factors included dietary protein (standard and reduced protein) and β-Mannanase supplementation (with or without). All diets contained phytase and carbohydrases (xylanase and glucanase). A total of 480 Ross 308 male off-sex day-old chickens were assigned to the four experimental diets in a 35-d study. Each diet was replicated 12 times with 10 birds per replicate. Using an additional 160 birds, separate apparent metabolizable energy (AME) and nutrient digestibility assays were undertaken for the 4 experimental diets from d 21 to 24 of age. Selected genes involved in gut integrity, inflammation and immune response were quantified using quantitative PCR assays. There was no interaction between β-Mannanase and dietary protein for any of the studied parameters except ileal viscosity. Enzyme had no effect on feed intake but tended to increase body weight gain (BWG) from d 0 to 35 of age (P = 0.079). Birds fed RP diet consumed more feed when assessed from d 0 to 35 of age (P = 0.029). At the same time, β-Mannanase tended to reduce feed conversion ratio independent of dietary protein (P = 0.069). β-Mannanase reduced ileal viscosity of the birds fed RP diet (P < 0.001). Reducing dietary protein increased nitrogen retention, nitrogen digestibility coefficient and digestibility coefficients of 11 amino acids (P < 0.001). β-Mannanase significantly improved digestibility coefficients of nitrogen and Arg, Gly, Thr, Lys, and Ile (P < 0.05). Dietary treatments had no effect on AME or gene expression of selected tight junction proteins, interleukin-10, interleukin-1β, mucin-2 and nuclear factor-kappa B. In conclusion, supplementation of β-Mannanase tended to improve feed efficiency and increased nutrient digestibility of broilers fed wheat-based diets independent of a moderate reduction in dietary protein. Complementary mode of actions of β-Mannanase for intestinal health requires further investigation.

In lambs, weaning imposes stress that can contribute to impaired rumen epithelial barrier functionality and immunological dysregulation. In this study, the effects of a yeast co-culture consisting of Saccharomyces cerevisiae and Kluyveromyces marxianus (NM) on rumen health in lambs was evaluated, with a focus on parameters including growth performance, ruminal fermentation, and epithelial barrier integrity, ruminal metabolic function, and the composition of the ruminal bacteria. In total, 24 lambs were grouped into four groups of six lambs including a control (C) group fed a basal diet, and N, M, and NM groups in which lambs were fed the basal diet respectively supplemented with S. cerevisiae yeast cultures (30 g/d per head), K. marxianus yeast cultures (30 g/d per head), and co-cultures of both yeasts (30 g/d per head), the experiment lasted for 42 d. Subsequent analyses revealed that relative to the C group, the average daily gain (ADG) of lambs in the NM group was significantly greater and exhibited significant increases in a range of mRNA relative expression including monocarboxylate transporter 1 (MCT1), (Na⁺)/hydrogen (H⁺) exchanger 1 (NHE1), (Na⁺)/hydrogen (H⁺) exchanger 3 (NHE3), proton-coupled amino acid transporter 1 (PAT1), vacuolar H⁺-ATPase (vH+ ATPase), claudin-1, occludin in the rumen epithelium (P < 0.05). Compared with the C group, the pH of the rumen contents in the NM group was significantly decreased , and the concentrations of acetate, propionate, and butyrate were significantly increased (P < 0.05). Analysis of the rumen bacteria showed that the NM group exhibited increases in the relative abundance of Prevotella, Treponema, Moryella, Fibrobacter, CF231 and Ruminococcus (P < 0.05). Metabolomics analyses revealed an increase in the relative content of phthalic acid and cinnamaldehyde in the NM group as compared to the C group (P < 0.05), together with the greater relative content of L-tyrosine, L-dopa, rosmarinic acid, and tyrosol generated by the tyrosine metabolic pathway (P < 0.05). Spearman's correlation analyses revealed relative abundance levels of Fibrobacter and Ruminococcus were positively correlated with the mRNA relative expression levels of PAT1, NHE3, and zonula occluden-1 (ZO-1), as well as with tyrosol, phthalic acid, and cinnamaldehyde levels (P < 0.05). Ultimately, these results suggest that dietary supplementation with NM has a wide range of beneficial effects on weaned lambs and is superior to single bacterial fermentation. These effects include improvements in daily gain and rumen epithelial barrier integrity, as well as improvements in the composition of the rumen microbiome, and alterations in tyrosine metabolic pathways.

In recent years, marine macroalgae have been recognized as potential alternative and sustainable feeding resources for livestock. Differences in nutritional values and biomass yield across macroalgal species are critical factors while aiming to utilize them as animal feed components. A brown macroalga, Saccharina latissima, also known as sugar kelp, has a promising biomass yield and high nutritional and bioactive compounds that can benefit both ruminant and monogastric animals. For example, the dietary inclusion of S. latissima in dairy and beef cattle can enhance milk yield, meat quality, and iodine content in milk and meat while reducing enteric methane emissions in vitro. However, high iodine content and the presence of some potentially toxic elements (arsenic, cadmium, etc.) lead to critical challenges, demanding careful consideration while determining the inclusion level of S. latissima in the livestock feed. To address these challenges, effective post-harvest biomass processing techniques, particularly hydrothermal treatments, have shown promise in reducing heavy metals and minerals of concern (e.g., iodine) and enhancing their safety as animal feed. It is thus essential to evaluate the sustainability of post-harvest processing techniques as they are usually energy-demanding and can negatively influence nutrient utilization in animals as certain digestible fractions can disappear during processing. Furthermore, variations in the nutritional and bioactive composition of S. latissima due to seasonal and spatial factors can create challenges for commercial exploitation. In this context, multiple harvesting of biomass and choosing the appropriate harvesting seasons can maximize the nutritional potential of S. latissima. In conclusion, S. latissima can be a novel feed ingredient for livestock, but year-round biomass availability and identifying cost-effective and energy-efficient post-harvest biomass processing methods that optimize both nutritional values and digestibility of S. latissima are critical for improving animal production, performance, and health.

A 10-week feeding trial, followed by 24-h nitrite stress, was performed to evaluate the effects of dietary selenium-L-methionine (Se-Met) on growth, Se accumulation, antioxidant capacity, transcripts of selenoproteins and histological changes of muscle as well as resistance to nitrite stress in spotted seabass (Lateolabrax maculatus) reared at optimal (27℃) and high (33℃) temperatures. Five experimental diets were formulated to contain Se-Met at 0, 0.9, 1.8, 3.5, and 7.0 mg/kg. Each diet was fed to fish (2.60 ± 0.2 g) in two parallel treatments at 27 or 33℃. The results showed that elevated temperature (33℃) induced thermal stress in fish, and fish under thermal stress exhibited lower weight gain and hepatosomatic index but a higher condition factor compared to those reared at 27℃. However, the growth and feed utilisation were promoted in L. maculatus with 0.9 to 3.5 mg/kg Se-Met treatments. The protein and lipid content in the muscle increased with the dietary Se-Met level, and the total Se level in the whole body and muscle showed a linear increase with dietary Se-Met supplementation. Thermal stress changed the histology of the muscle, leading to raised levels of malondialdehyde (MDA), reduced antioxidant parameters in the serum and liver, and a decrease in the transcripts of selenoprotein genes in the muscle. Meanwhile, increased antioxidant capacity of serum and liver and up-regulated transcripts of selenoprotein of muscle were observed in L. maculatus reaching a maximum with 3.5 mg Se-Met/kg treatment. After 24 h of nitrite stress, thermal stress exacerbated oxidative damage caused by nitrite stress in L. maculatus. In contrast, dietary Se-Met enhanced the resistance to nitrite stress of L. maculatus fed with Se-Met enriched diets containing 0.9 to 1.8 mg Se-Met/kg. Based on the effects of dietary Se-Met on the growth, antioxidant capacity and resistance to nitrite stress of L. maculatus, this study suggests that the optimal range of Se-Met supplementation in L. maculatus diets is 1.80 to 2.39 mg Se-Met/kg of diet at 27℃ and 1.80 to 4.46 mg Se-Met/kg of diet at 33℃.

Intramuscular fat (IMF) content influences various meat quality traits, including tenderness, flavor, juiciness and nutritional value. This study aimed to investigate the effects of dietary inositol supplementation on meat quality, metabolic profiles, and gut microbiota composition of finishing pigs. A total of 144 finishing pigs (initial body weight 70.41 ± 0.78 kg) were randomly divided into control, 0.075%, 0.15%, and 0.3% inositol groups. The data showed that inositol increased backfat thickness at the 6th to 7th rib and 10th rib, IMF content, and improved tenderness (P ≤ 0.05, n = 8). Paralleling an increase in fat deposition, 0.3% inositol also increased the protein level of PPARγ in the subcutaneous fat (P ≤ 0.05) and longissimus thoracis (LT) muscle (P = 0.062). Inositol elevated the content of amino acids in LT muscle and enhanced amino acid metabolism of finishing pigs, including lysine degradation, tyrosine metabolism, and arginine and proline metabolism. The 16S ribosomal RNA (rRNA) sequencing showed that 0.3% inositol supplementation altered the profiles of microbes in the colon, particularly decreasing the abundance of Firmicutes (P < 0.01) and increasing the abundance of Bacteroidota (P ≤ 0.05). Correlation analysis showed that differential microbes had strong correlation with differential metabolites in serum, including amino acids. In conclusion, this study demonstrated that dietary inositol supplementation could effectively improve IMF content and tenderness of pork, enhance amino acid metabolism, and regulate gut microbiota composition of finishing pigs.

With the increasing incorporation of plant-based ingredients into the grouper diet, the issue of aflatoxin B1 (AFB1) contamination in the diet has become a significant concern. In this study, the negative effects of AFB1 on the growth and liver health of hybrid groupers (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂) were investigated in the context of growth, liver histology, serum biochemical indices, and integrated transcriptomic and metabolomic data. A total of 540 healthy hybrid groupers, initially weighing 11.59 ± 0.03 g, were randomly divided into six groups (three replicates of 30 fish each): the control group was fed a basal diet, and the experimental groups were supplemented with 7 (AF7), 30 (AF30), 111 (AF111), 445 (AF445) and 2230 μg/kg AFB1 (AF2230) in the basal diet respectively, for 56 days. Groups control, AF445, and AF2230 were selected for subsequent histological, muscle fatty acid, and transcriptomic and metabolomic analyses based on the results of hybrid grouper growth and serum biochemical indices. Compared to the control group, both whole-body crude lipid and muscle crude lipid contents showed significant decreases in the AF2230 group (P < 0.05), while only muscle crude lipid content showed a significant decrease in the AF445 group (P = 0.001). Liver damage was seen in the histology of the liver of AF445 and AF2230 groups. Muscle fatty acid results showed that the addition of 445 and 2230 μg/kg AFB1 to the diets increased saturated fatty acids and monounsaturated fatty acids and decreased polyunsaturated fatty acids and highly unsaturated fatty acids in muscle (P < 0.05). Transcriptome analyses revealed multiple metabolic pathways associated with AFB1 metabolism, and metabolomics analyses further confirmed changes in the activity of these pathways. The results of the combined transcriptomic and metabolomic analyses indicated that AFB1 causes liver injury mainly by affecting liver retinol metabolism, metabolism of xenobiotics by cytochromes P450, drug metabolism-cytochromes P450 and biosynthesis of unsaturated fatty acids. In conclusion, dietary AFB1 levels above 445 μg/kg resulted in growth inhibition, liver injury, liver AFB1 accumulation, and reduced muscle polyunsaturated fatty acid content in groupers, thereby affecting muscle quality. This study provides novel insights into the detrimental effects of AFB1 on aquatic species and contributes to the scientific basis for the health and sustainability of aquaculture practices.

This study investigated whether vitamin A (VA) administration during the neonatal stage could increase the number of intramuscular adipocytes in Hu sheep by promoting vascularity. A total of 56 newborn male Hu sheep were divided into four groups and received intramuscular injections of either 0, 7500 IU retinoic acid (RA), 7500 IU VA, or a combination of 7500 IU VA and 5 mg SU5416 (an angiogenic inhibitor), at 1, 7, 14, and 21 days of age. At 15 days of age, 6 sheep from each group were randomly selected and sacrificed for intramuscular adipogenic capacity analysis. The remaining 8 sheep in each group were raised until they were 8 months old. VA-treated sheep exhibited an increase in preadipocytes, elevated expression of adipogenic genes (CCAAT enhancer binding protein alpha [CEBPA] and CCAAT enhancer binding protein beta [CEBPB]) and angiogenic genes (vascular endothelial growth factor A [VEGFA]), and stromal vascular fraction cells in the longissimus dorsi (LD) muscle with enhanced adipogenic capacity (P < 0.05). These effects were entirely negated by SU5416. Upon slaughter, VA increased final weight, carcass weight, and average daily gain (P < 0.05) but did not affect feed intake at 21 to 32 weeks (P = 0.824). VA increased the number of intramuscular adipocytes in the LD and semitendinosus (ST) muscle (P < 0.05) without changing the adipocyte number of the omentum, perirenal and subcutaneous fats (P > 0.05). VA injections also increased intramuscular triglyceride (TG) content (P = 0.016) without changing the omentum fat weight or subcutaneous fat thickness (P > 0.05), but it did increase the perirenal fat weight (P = 0.011). Consistently, SU5416 mitigated the effects of VA on intramuscular TG content and adipocyte count, correlating with a decrease in vascularity. In contrast, RA injections didn't affect the intramuscular fat (P = 0.744) but reduced the TG content of the omentum and perirenal fat (P < 0.05). In conclusion, intramuscular injections of VA but not RA at the neonatal stage improved the growth performance of Hu sheep, increasing the number of intramuscular adipocytes and marbling by promoting angiogenesis.

This study investigated the effects of dietary methionine (Met) on growth performance and protein synthesis in juvenile Chinese mitten crabs (Eriocheir sinensis) fed fish meal (FM)-free diets. Three diets free of FM containing 0.48% (LM), 1.05% (MM), and 1.72% (HM) Met were assessed, and the cysteine content in all the diets was adjusted to 0.46%. The control diet contained 35% FM without Met supplementation. Extra lysine was added to all of the FM-free diets to match the lysine level in the control diet. Juvenile E. sinensis (800 crabs weighing 0.74 ± 0.01 g each) were fed these four diets for eight weeks, with five replicates for each treatment. Both the LM and HM groups presented lower weight gain than all the other groups did (P = 0.002). The survival of the crabs was lower in the LM and HM groups than in the MM group (P = 0.005). Compared with those in the other groups, the growth performance of the crabs in the MM group improved, and lipid deposition and protein accumulation increased. These positive outcomes are associated with high protein expression linked to the mammalian target of the rapamycin (mTOR) pathway and low expression of genes and proteins linked to the PRKR-like endoplasmic reticulum kinase (PERK) pathway. The study of Met supplementation has explored the response of the PERK pathway through reducing glutathione (GSH) levels to promote protein synthesis. The injection of Met and L-buthionine-sulfoximine (BSO), an inhibitor of GSH synthesis, suppressed GSH production and altered the expression of genes and proteins related to protein synthesis pathways. This study suggests that Met supplementation in FM-free diets can increase the growth and protein synthesis of E. sinensis by modulating specific cellular pathways, particularly the mTOR and PERK pathways.

Indole-3-propionic acid (IPA) has anti-inflammatory properties, which can be beneficial for weaned piglets with underdeveloped immune systems. The study explores the impact of IPA supplementation on growth performance, oxidative stress, and inflammation response in weaned piglets. In Exp. 1, 90 weaned piglets were divided into six groups (5 replicates per group, 3 pigs per replicate), with each group receiving a basal diet with varying amounts of IPA (0, 50, 100, 200, 400, or 600 mg/kg) for 42 d. Piglets fed the diets with 50, 100, and 200 mg/kg of IPA exhibited reduced feed conversion ratios (F:G) compared to the control piglets (P = 0.035). Notably, 50 and 100 mg/kg IPA treatments significantly reduced diarrhea incidence and serum interleukin (IL)-6 content (P < 0.05). Conversely, a high dosage of 600 mg/kg IPA led to increased serum contents of tumor necrosis factor (TNF)-α, and IL-6 (P < 0.05). Optimal antioxidant benefits were observed at 100 mg/kg IPA supplementation, which significantly reduced malondialdehyde levels while enhancing serum total antioxidant capacity and total superoxide dismutase activity on d 14 (P < 0.05). Exp. 2 investigated the effects of IPA on lipopolysaccharide (LPS) challenge in weaned piglets. The study consisted of 32 weaned piglets allocated into 4 groups, with 8 replicates per group and 1 piglet per replicate: a control group, a LPS challenge group, a LPS challenge group supplemented with 100 mg/kg IPA, and a group supplemented with 100 mg/kg IPA alone. Upon administration of LPS or saline injection, the results indicated that dietary IPA supplementation in challenged piglets enhanced villus height: crypt depth, modulated IL-8 and IL-22 mRNA relative expression, and increased the tight junction protein claudin-1 mRNA relative expression in the intestinal mucosa (P < 0.05). These findings suggest that dietary supplementation of IPA at specific concentrations significantly improves growth performance, reduces diarrhea incidence, and mitigates inflammation and oxidative stress in weaned piglets. It may be concluded that incorporating IPA into the diet of weaned piglets can effectively improve their health and development.