Search Results (997)

Organic amendments derived from agro-livestock residues offer a promising approach for soil restoration and nutrient recycling within circular economy frameworks. Nevertheless, their agronomic efficacy and environmental suitability may be contingent upon the formulation of the amendments and the properties of the soil. This study presents a preliminary evaluation of customized organic amendments derived from solid materials, such as biochar and green compost, and liquid residues, including cattle manure slurry, urban compost tea, and cattle digestate. These were applied either individually or as solid–liquid mixtures to two distinct Iberian soils. The study involved amendment characterization, seed germination assays, and a two-month greenhouse experiment with barley (Hordeum vulgare L.) to assess the effects on soil physicochemical properties, microbial activity, and plant development. The solid–liquid impregnation process facilitated the transfer of nutrients and potentially limiting elements from liquid residues to solid matrices, thereby altering amendment composition and mitigating some risks associated with the direct application of liquid residues. Mixtures based on biochar and compost generally alleviated excessive salinity and trace metal constraints, although responses varied depending on the liquid amendment and soil type. Biochar-containing amendments markedly increased soil total carbon, suggesting their potential to contribute to soil carbon sequestration. The effects of amendments were strongly dependent on soil type: acidic soil exhibited more pronounced pH improvement, whereas the carbonate-rich alkaline soil buffered several chemical changes but was more susceptible to alkalinization and sodium inputs. Urban compost tea consistently exhibited inhibitory effects on germination, plant development, and dehydrogenase activity, although these effects were partially mitigated when combined with solid amendments. Overall, the findings underscore the potential of tailored amendment mixtures to enhance residue valorisation, while highlighting the necessity for soil-specific evaluation prior to field application. Full article

The use of crossbreeding between dairy and beef breeds has been adopted as a strategy to add value to male calves from dairy systems, improve productive efficiency, and reduce economic and animal welfare concerns. This study evaluated the effects of Holstein × Angus crossbreeding on productive performance, metabolism, ruminal fermentation, nutrient digestibility, carcass characteristics, meat quality, and fatty acid profile during the feedlot finishing phase. Twenty-four uncastrated male cattle (8 Holstein, 8 Angus, and 8 crossbreds) were confined for 130 days and fed an isoenergetic and isonitrogenous diet. No significant differences were observed among breeds for weight gain, dry matter intake, feed efficiency, or nutrient digestibility (p > 0.05). However, Angus and crossbred cattle showed higher carcass yield compared to Holstein cattle (p ≤ 0.05). Angus and crossbred animals presented higher concentrations of total volatile fatty acids, acetate, and propionate in the rumen (p ≤ 0.05). Breed differences were also observed in erythrocyte indices and serum urea concentrations (p ≤ 0.05). Meat from crossbred animals showed superior quality attributes compared to Holstein, including lower ultimate pH, higher lightness, greater water-holding capacity, and an intermediate lipid profile between the parental breeds (p ≤ 0.05). It is concluded that Holstein × Angus crossbreeding improves carcass yield, ruminal fermentation efficiency, and meat quality, without compromising productive performance, representing a viable strategy for adding value to male calves from dairy herds under tropical production conditions. Full article

This study evaluated the effects of dietary LC inclusion (0, 50, 100, 200, and 400 mg/kg) in Pekin ducklings from 7 to 65 days of age on growth performance, carcass traits, metabolic profile, immune status, and economic efficiency. A total of 250 unsexed 7-day-old Pekin ducklings were randomly allocated to five dietary treatment groups, each comprising five replicates of 10 ducklings. The linear response plateau analysis estimated LC breakpoints of approximately 50 mg/kg diet for body weight gain and feed conversion ratio. Additionally, LC significantly improved carcass yield and crude protein content of the meat, as well as enhanced its antioxidant capacity. Physiologically, LC enhanced hematological indices, lipid metabolism, and thyroid hormone activity, without adversely affecting liver function. Moreover, LC favorably modulated the intestinal microbiota by increasing the abundance of beneficial Lactobacillus spp. and reducing pathogenic bacteria. Furthermore, it improved immune status, as indicated by higher immunoglobulin levels, lysozyme and phagocytic activities, and lymphocyte proliferation. LC significantly enhanced the mentioned parameters without inducing any adverse effects; however, the magnitude of the response plateaued and subsequently declined at higher inclusion levels (200–400 mg/kg). The improvements in performance and health status were attributed to the enhanced fatty acid oxidation, energy metabolism, antioxidant defense, and immunomodulatory effects of LC. In conclusion, including 50 mg L-carnitine/kg in the diet represents an effective and appropriate nutritional strategy under the conditions of the present study to optimize growth performance, carcass quality, nutrient digestibility, health status, and economic profitability in Pekin duck production systems. Full article

In this study, targeted metabolomics and transcriptomics were applied for the first time to compare fatty acid contents, vitamin levels, and gene expression profiles between Stage II and Stage IV ovaries of LBG. The data revealed a rise in total SFA and PUFA as the ovary progressed from Stage II to Stage IV. The marked increase in n-3 PUFA from 11.5% in Stage II to 26.8% in Stage IV ovaries was primarily attributed to DHA. Despite a reduction in n-6 PUFA, ARA and its metabolism-related fatty acids all increased, suggesting indispensable roles for both ARA and DHA in the vitellogenesis of LBG. Consistent with the changes in fatty acid profiles during ovarian maturation, transcriptome analysis revealed that many upregulated differentially expressed genes (DEGs) showed significant enrichment in fatty acid biosynthesis, arachidonic acid metabolism, and steroid hormone synthesis pathways. The concentrations of VC and VE increased, whereas VA declined during ovarian development from Stage II to Stage IV. Accordingly, many upregulated DEGs exhibited significant enrichment in ascorbate and aldarate metabolism, as well as vitamin digestion and absorption pathways. In addition to VC and VE, our transcriptome data also highlighted the importance of several B vitamins in oocyte development of LBG, warranting further investigation. Overall, these findings suggest that DHA, ARA, VC, and VE are key nutrients governing oocyte maturation in LBG. This study provides a solid theoretical basis for developing broodstock nutritional enhancement strategies in the artificial propagation of LBG. Full article

Rapid population growth, urbanization, and industrialization are continuously increasing global energy demand while intensifying climate change associated with fossil fuel consumption. In this context, renewable energy production from organic waste has gained increasing attention as a sustainable and environmentally friendly strategy. Anaerobic digestion (AD) offers significant potential for simultaneous waste stabilization and biomethane generation. However, many previous studies investigating lignocellulosic or nutrient-rich substrates have relied on physical, chemical, or thermal pretreatment methods to enhance biodegradability, despite their additional operational costs, energy consumption, and environmental impacts. Therefore, developing low-cost and pretreatment-free co-digestion strategies remains an important research need. This study investigated the biomethane production potentials of untreated chicken manure (CM) and duckweed (Lemna minor-LM) collected from the final sedimentation tanks of wastewater treatment plants under mono-digestion and co-digestion conditions. The study hypothesized that rapidly growing and widely available LM biomass could enhance methane production without requiring pretreatment. Among all reactors, CM0.75 (75% of the total TS derived from CM and 25% from LM and inoculum) achieved the highest performance with a cumulative biogas production of 5350 mL (74.2% of CH4) and a methane yield of 327 mL CH4/g VS, while mono-digestion of CM resulted in the lowest methane yield of 104 mL CH4/g VS. The results demonstrated that LM biomass naturally proliferating in wastewater treatment plants can be directly utilized as an effective co-substrate to improve biomethane production from poultry wastes. The proposed approach provides a cost-efficient, eco-friendly, and circular-economy-oriented alternative by eliminating the need for pretreatment while simultaneously valorizing problematic biomass generated in wastewater treatment facilities. Full article

Provision of cow–calf contact (CCC) in combination with pair housing may enhance welfare and stimulate greater intake of both milk and starter feed, thereby improving the performance and health of calves reared under cold conditions. This study was conducted to investigate the effects of combining partial daily CCC (5 h/d) with pair housing (19 h/d) in dairy calves reared in outdoor pens during winter, when the mean ambient temperature was 6.2 ± 0.4 °C throughout the study period. A total of 30 Holstein calves (birth weight = 37.4 ± 3.4 kg) were enrolled at birth. Fourteen calves received daily dam contact and were pair-housed (DC-PH), while the remaining 16 calves had no dam contact (NC); of these, 8 were pair-housed (NC-PH) and 8 were individually housed (NC-IH). Dam contact was maintained until day 60, after which all calves were weaned and group-housed until day 80. Milk consumption was greater in DC than NC calves (7.4 vs. 5.5 L/d). During the pre-weaning period, body weight and average daily gain did not differ between treatments. However, DC-PH calves had greater body weight at day 80 and higher average daily gain between days 60 and 80 than NC-PH calves (p = 0.01 and p = 0.02, respectively). Pre-weaning starter feed intake and feed efficiency did not differ across treatment groups. Dry matter digestibility was significantly greater in NC-PH than in NC-IH calves (87.7% vs. 81.4%; p = 0.03), but no significant effects were observed on NDF and DM digestibility between NC-PH and DC-PH calves. On day 54 (the pre-weaning phase), compared with NC-PH calves, DC-PH calves had higher blood glucose (p = 0.05), lower cortisol (p = 0.02), tended to have lower βHBA concentrations (p = 0.06), and a greater ruminal protozoal count on day 35 (p = 0.01). Total health score tended to be higher in DC-PH than NC-PH calves (p = 0.06) and was higher in NC-IH than in NC-PH calves (p = 0.05). During an 8-h behavioral recording prior to weaning, DC-PH calves were observed less frequently performing non-nutritive oral behaviors, such as licking the stall or fences and sucking on other calves, and tended to be more frequently standing, contacting other calves, playing alone, walking, and ruminating than NC-PH calves. After weaning, DC-PH calves were observed more frequently eating, resting, walking, and engaging in social interactions than NC-PH calves. Likewise, after weaning, NC-IH calves were observed more frequently playing, vocalizing, and walking, but less eating than NC-PH calves. Overall, our findings indicated that while social interaction (NC-IH vs. NC-PH) significantly improved dry matter digestibility and health, the addition of dam contact (DC-PH) maintained nutrient digestibility at levels comparable to NC-PH, but tended to reduce health status. Also, calves in the DC-PH treatment, which voluntarily consumed more milk than NC calves, exhibited greater post-weaning growth, more favorable behavioral responses, and improved pre-weaning metabolic profiles (lower cortisol and βHBA concentrations and higher blood glucose). These findings indicate that the partial dam contact management system, together with greater voluntary milk intake, was associated with enhanced post-weaning performance and metabolic status, as well as differences in rumen microbial development. However, as milk intake was not standardized across treatments, these responses cannot be attributed solely to maternal contact. Overall, under the conditions of this study, partial dam contact represents a feasible management strategy to support calf welfare and development, provided that appropriate environmental management is implemented to minimize disease risks. Full article

Feed efficiency classification based on residual feed intake (RFI) and residual intake and gain (RIG) is widely used to identify biologically efficient animals, yet it remains unclear whether this classification reflects consistent differences in digestive, fermentative, and metabolic processes. This study evaluated the effects of RFI and RIG classification on nutrient intake, apparent digestibility, ruminal fermentation, nitrogen metabolism, microbial protein synthesis, and gaseous emissions in confined lambs. Thirty-eight weaned Texel ewe lambs underwent a 60-day performance test using an automated feed intake system and were classified as high-efficiency, neutral, or low-efficiency based on both indices. Animals were individually housed in respirometric chambers where emissions of methane, carbon dioxide, nitrous oxide, and ammonia were assessed by cavity ring-down spectroscopy; apparent digestibility was determined from total collections of feed, orts, faeces, and urine; microbial protein synthesis was estimated from urinary purine derivatives; and ruminal short-chain fatty acid profiles were determined by gas chromatography. Feed efficiency classification did not significantly affect body weight, nutrient intake, apparent digestibility, ruminal fermentation parameters, nitrogen balance, microbial protein synthesis, or greenhouse gas emissions. Principal component analysis revealed two major biological gradients related to nutrient intake and utilisation (42.9%) and ruminal fermentation and gaseous emissions (23.3%), together explaining 66.2% of total variance, but showing no clear separation among efficiency groups. These findings indicate that the digestive, fermentative, and nitrogen metabolism variables evaluated in this study did not account for the observed variation in feed efficiency. Because the regression underlying RIG explained little additional variation (R² = 0.01), these conclusions primarily reflect feed efficiency as classified by RFI, suggesting that other physiological mechanisms may play a more important role in determining feed efficiency in confined Texel ewe lambs. Full article

A total of 96 26-day-old weaned piglets were randomly assigned to four groups with three replicates per group: (1) CON group (basal diet), (2) PRS group (protease supplementation), (3) AMS group (amylase supplementation), and (4) combined protease and amylase group (PAS group) (protease and amylase supplementation). Compared to the CON group, AMS group reduced feed-to-gain ratio (p < 0.05). Additionally, all treatments increased ether extract digestibility (p < 0.05). The PRS and AMS groups reduced serum urea nitrogen level (p < 0.01). PAS group increased total protein, and decreased total cholesterol (p < 0.05). PRS and/or AMS supplementation increased serum glutathione peroxidase. IgM and IgG were higher in the AMS group. Furthermore, levels of D-Lactate and diamine oxidase were reduced (p < 0.05). PRS group exhibited increased fecal acetic acid and valeric acid levels (p < 0.05). Microbiota analysis showed that PRS or/and AMS supplementation enriched bacteria, including Anaerovoracaceae and Blautia. Metabolomics analysis revealed that health-promoting differential metabolites, including S-nitrosoglutathione and kynurenic acid, were further enriched, indicating enhanced immune regulation and intestinal homeostasis. Taken together, PRS or/and AMS supplementation can effectively promote nutrient digestion, intestinal microbiota structure and metabolism, and enhance intestinal barrier, thereby improving growth performance in weaned piglets. Full article

Poly(3-hydroxypropionate) (P3HP) is a biodegradable member of the polyhydroxyalkanoate family that can be degraded into 3-hydroxypropionic acid, a three-carbon organic acid with potential biological activity. Although P3HP has attracted considerable interest for its microbial production and industrial applications, its potential as a feed ingredient in monogastric animals remains largely unexplored. Therefore, we aim to assess the effects of dietary P3HP supplementation on growth performance, nutrient digestibility, fecal N retention and apparent N absorption, selected culturable fecal bacterial counts, and in vitro fecal fermentation in growing pigs. A total of 100 [Duroc × (Landrace × Yorkshire) pigs; initial body weight 25.03 ± 1.70 kg] were assigned to four dietary treatments containing 0, 0.1, 0.2, and 0.3% P3HP for 6 weeks. At the end of the experimental period, dietary P3HP supplementation did not significantly (p > 0.05) affect final body weight, average daily gain, dry matter digestibility, nitrogen digestibility, apparent nitrogen absorption variables, or in vitro fecal fermentation in growing pigs but exhibited linear or quadratic trends (p < 0.1), with the most favorable numerical responses observed at the 0.2% inclusion level. In summary, although dietary P3HP supplementation did not significantly affect the principal measured outcomes, the favorable trends observed support further investigation of its potential as a novel feed additive for growing pigs. Full article

The aim of this study was to evaluate the effects of a Bacillus subtilis-derived postbiotic on apparent total tract nutrient digestibility, faecal fermentation characteristics, gut microbiota, immune response, blood biochemistry, hematological parameters, serum trace minerals, and coat quality in healthy senior dogs. Twenty-one healthy senior Golden Retriever dogs (9 ± 1.0 years old) were randomly allocated to three dietary treatments for 28 days: a control diet (CON) or the same diet supplemented with 0.3 (POS1) or 0.6 mL/day (POS2) of a Bacillus subtilis-derived postbiotic. Apparent nutrient digestibility, faecal characteristics, blood variables, and coat quality were evaluated, whereas faecal bacterial communities were characterized by 16S rRNA gene amplicon sequencing, followed by taxonomic classification and alpha- and beta-diversity analyses. Postbiotic supplementation significantly improved crude protein and crude fiber digestibility while reducing faecal pH and ammonia concentrations and increasing acetate, propionate, and total short-chain fatty acid concentrations (p < 0.05). Alpha diversity was minimally affected, with a significant difference observed only for amplicon sequence variant (ASV) richness, whereas beta diversity analyses demonstrated significant alterations in overall microbial community composition. Postbiotic supplementation increased the relative abundance of Faecalibacterium, Ligilactobacillus, Bifidobacterium, Prevotella, Turicibacter, and Fusobacterium, while reducing Bacteroides and Achromobacter. Serum IgG concentrations increased, whereas cholesterol and triglyceride concentrations decreased in supplemented dogs (p < 0.05). Coat morphology and gloss also improved, without adverse effects on hematological, biochemical, or serum trace mineral parameters. In conclusion, Bacillus subtilis-derived postbiotic supplementation improved nutrient utilization, beneficially modulated faecal microbial ecology and fermentation, enhanced selected metabolic and immune responses, and improved coat quality, supporting its potential as a functional dietary strategy for promoting gastrointestinal and systemic health in healthy senior dogs. Full article

This study examined the effects of replacing 25% (P25) or 50% (P50) of concentrate dry matter (DM) with sun-dried carob (Ceratonia siliqua L.) pods on growth performance, apparent nutrient digestibility, carcass traits, meat quality, serum biochemistry, and rumen microbiology in growing Assaf lambs. Twenty-four weaned male Assaf lambs (initial body weight [BW] 27.0 ± 0.5 kg; 2.5 months of age) were randomly assigned to three dietary treatments (n = 8 per group) in a completely randomized design and fed for 16 weeks. P50 achieved the highest ANCOVA-adjusted least squares mean final BW (53.0 kg) and average daily gain (ADG) (220.8 g/d), followed by P25 (51.1 kg; 203.3 g/d) and the control (46.2 kg; 160.2 g/d) (p < 0.001). Feed conversion ratio (FCR) improved from 8.99 in the control to 6.16 and 6.11 in P25 and P50, respectively, with no significant difference between the two carob-supplemented groups (p < 0.001). Apparent DM and organic matter (OM) digestibility increased with carob inclusion at both 3 and 6 months of age (p ≤ 0.0001). Cold carcass weight (CCW) was higher in carob-supplemented lambs (p < 0.001), whereas carcass muscle proportion did not differ among treatments (p = 0.688), and carcass fat proportion was higher in P25 than in the control (p = 0.039). Warner–Bratzler shear force declined progressively with carob inclusion (p < 0.001), indicating improved meat tenderness. Serum total protein was highest in P25, whereas blood urea nitrogen (BUN), low-density lipoprotein (LDL), and glutamate oxaloacetate transaminase (GOT) decreased with carob inclusion (p < 0.001). Rumen pH was highest in P25 (6.40), total bacterial and lactic acid bacteria (LAB) counts increased, and protozoa counts declined (p < 0.001). Because carob pods replaced concentrate, rather than being added to an isonitrogenous diet, the combined effects of pods per se, reduced crude protein supply, and altered energy density must all be considered when interpreting the results. These findings support carob pods as a practical, locally available partial substitute for concentrate feed in Assaf lamb production under Mediterranean and Near Eastern conditions. Full article

This study evaluated the effects of Fibrafid, a plant-based functional feed additive, on growth performance, carcass traits, meat quality, and intestinal histomorphometry of broilers fed standard or moderately nutrient-reduced diets. A total of 432 one-day-old Ross 308 chicks (initial body weight, 44.9 ± 0.30 g) were randomly allocated to a 2 × 3 factorial arrangement comprising two dietary nutrient densities (standard or diets with 1.5% lower metabolizable energy and 5% lower digestible amino acid density) and three Fibrafid inclusion levels (0, 1.5, or 2.5 kg/ton). Each treatment comprised six replicates of 12 birds (six males and six females) and was evaluated from day 1 to 24. Dietary nutrient reduction affected growth performance and breast meat quality pH and ultimate lightness values, whereas Fibrafid supplementation, particularly at 2.5 kg/ton, improved overall gain by 5.3%, grower-phase feed conversion ratio by 4.0%, EPEF by 8.08%, relative thymus weight by 64.8%, while reducing abdominal fat deposition by 27.1% relative to the unsupplemented control (p < 0.05). Several breast meat quality traits were also improved, including greater water-holding capacity and myofibril fragmentation index and lower drip and cooking losses (p < 0.05). Jejunal morphology was enhanced, as indicated by increased villus dimensions and goblet cell density (p < 0.05). Significant Diet × Fibrafid interactions were observed for grower performance, EPEF, overall feed intake, and several intestinal morphological variables (p < 0.05). In conclusion, Fibrafid supplementation, particularly at 2.5 kg/ton, was associated with improved growth performance, EPEF, selected carcass and breast meat quality traits, and jejunal morphology during the first 24 days of age. These findings suggest that Fibrafid may be a promising natural feed additive for broiler diets formulated at standard or moderately reduced nutrient densities. However, further studies extending to market age and evaluating nutrient digestibility, intestinal microbiota, blood biochemical indices, and economic returns are warranted to clarify its mechanisms and practical value under commercial production conditions. Full article

To investigate the effects of 5-hydroxymethylfurfural (5-HMF) on ruminal fermentation characteristics and bacterial community structure, 5-HMF was supplemented at the levels of 0, 7500, and 30,000 mg/kg DM under two dietary concentrate-to-roughage ratios (20:80, T1; 80:20, T2) in in vitro rumen incubation, mainly focusing on gas production, fermentation parameters, nutrient digestibility and bacterial community. The results showed that 24 h gas production (GP₂₄), 72 h gas production (GP₇₂), the gas production rate (c) and dry matter digestibility (DMD) in T2 were higher than those in T1 (p < 0.01). With increasing levels of 5-HMF supplementation, GP₇₂ and asymptotic gas production (B) increased linearly and quadratically (p < 0.05). T2 also had a higher butyrate concentration and a lower acetate/propionate (A/P) ratio than T1 (p < 0.05). With the increase in 5-HMF supplementation level, ruminal ammonia nitrogen (NH₃-N) concentration showed a quadratic response. In contrast, the concentrations of total volatile fatty acids (TVFAs), acetate and isobutyrate decreased linearly. Propionate concentration showed linear and quadratic decreasing trends, while the A/P ratio exhibited linear and quadratic increasing trends (p < 0.05). The supplementation of 5-HMF at 30,000 mg/kg DM reduced propionate and isobutyrate concentrations under both dietary conditions (p < 0.05). No differences were observed in the alpha diversity indices of the bacterial community among different 5-HMF levels or substrates (p > 0.05). PCoA and PERMANOVA revealed that community structure differed between the 7500 mg/kg DM group and the 0 mg/kg DM group in the T1 diet (p = 0.011), whereas no difference was detected among T2 treatments. LEfSe revealed that 6 and 13 differential bacterial taxa were identified in T1 and T2 at the 5-HMF level of 7500 mg/kg DM, respectively. Correlation analysis revealed that, in T1, GP₇₂ was positively correlated with Pseudomonadota, and the A/P ratio was positively correlated with fibrolytic taxa including Rikenellaceae_RC9_gut_group and Christensenellaceae_R-7_group. In T2, c was positively correlated with Fibrobacterota and Fibrobacter, while NH₃-N was positively correlated with Desulfovibrio, indicating diet-specific microbial associations with rumen fermentation (p < 0.05). In conclusion, the high-concentrate diet exhibited stronger rumen fermentation activity. 5-HMF exerted diet-specific effects: In the low-concentrate diet, 5-HMF at 7500 mg/kg DM enriched fibrolytic microbes and shifted fermentation toward an acetate-type pattern. In the high-concentrate diet, it modulated hydrogen-metabolizing bacteria while selectively enriching Pseudomonadota capable of participating in carbohydrate metabolism. The 30,000 mg/kg DM level inhibited rumen fermentation. The findings provide a theoretical reference for the application of 5-HMF in ruminant feeds. However, further in vivo trials are required to validate its effects, and future studies with refined dose gradients based on realistic 5-HMF concentrations in feedstuffs are needed to comprehensively evaluate its efficacy and safety. Full article

This study developed a compound enzyme-assisted microbially fermented concentrate for Yanbian steers. The enzyme formulation was optimized using response surface methodology, with acid-soluble protein/crude protein ratio (ASP/CP), ammonia-N/total N ratio (AN/TN), and pH as response variables. The optimized enzyme preparation contained 619.15 U/g protease, 742.08 U/g amylase, and 257.75 U/g β-mannanase. The measured ASP/CP, AN/TN, and pH values were 31.74%, 3.56%, and 4.32, respectively, closely agreeing with the predicted values of 32.00%, 3.55%, and 4.28. Membership function analysis, which normalized positive and negative indicators to a common 0–1 scale and integrated them into a comprehensive score, supported the selection of day 5 as the most balanced fermentation duration under the primary equal-indicator weighting scheme. Thirty Yanbian steers were randomly assigned to receive microbially fermented concentrate without compound enzyme addition (MF) or compound enzyme-assisted microbially fermented concentrate (MEF) at 500 g/head/day on an as-fed basis for 100 days. After adjustment for initial body weight using ANCOVA, MEF increased final body weight by 3.9% and average daily gain by 35.7% compared with MF (both p < 0.001). MEF also increased dry matter intake by 12.1% (p = 0.018) and reduced feed conversion ratio by 18.4% (p = 0.008). MEF increased dry matter, crude protein, neutral detergent fiber, and acid detergent fiber digestibility by 4.3%, 5.4%, 22.6%, and 15.6%, respectively, and reduced blood urea nitrogen by 18.9%. MEF also increased ruminal total volatile fatty acids and decreased ruminal NH₃-N and the acetate-to-propionate ratio (p < 0.05). Observed ASVs, Chao1, and Shannon indices did not differ between treatments, whereas PERMANOVA detected a significant difference in overall rumen bacterial community structure (R² = 0.180, p = 0.023). VIF-based redundancy analysis indicated that variation in rumen bacterial community structure were correlated with crude protein digestibility, total volatile fatty acids, and blood urea nitrogen. Overall, within the microbial-fermentation system evaluated in this study, compound enzyme addition increased growth performance and apparent nutrient digestibility, reduced ruminal NH₃-N and blood urea nitrogen concentrations, and improved feed efficiency in Yanbian steers. Full article

This study aimed to evaluate the effects of dietary supplementation with guanidinoacetic acid (GAA) on growth performance, antioxidant status, nutrient digestibility, ruminal fermentation, and meat quality in lambs through a meta-analysis. The electronic databases Scopus, Web of Science, ScienceDirect, and Google Scholar were used to identify the articles required for the meta-analysis using the Preferred Reporting Elements for Systematic Reviews and Meta-Analyses (PRISMA) methodology. The data used in this meta-analysis were obtained from 12 peer-reviewed English-language articles published in the last decade (January 2016 to April 2026). All data were analyzed using random-effects models. Dietary supplementation with GAA decreased the feed conversion ratio (p < 0.05) and increased (p < 0.05) dry matter intake, average daily gain, carcass weight and yield, and Longissimus dorsi muscle area. Dietary supplementation with GAA decreased (p < 0.001) serum malondialdehyde concentration and increased (p ≤ 0.05) serum concentrations of superoxide dismutase, catalase, glutathione peroxidase, and total antioxidant capacity. Dietary supplementation with GAA decreased (p < 0.001) ruminal pH and increased (p < 0.05) the digestibility of dry matter, organic matter, neutral detergent fiber, and acid detergent fiber, as well as the ruminal concentrations of total volatile fatty acids, acetate, and butyrate. Dietary supplementation with GAA decreased (p < 0.001) drip loss in meat and increased (p < 0.001) meat pH and meat protein content. In conclusion, guanidinoacetic acid can be used as a dietary additive to improve growth performance, antioxidant status, nutrient digestibility, ruminal fermentation, and meat quality in lambs. Full article