Yeast biomass represents a renewable source of single-cell protein that can be used as an alternative feed ingredient in laying hen diets. The objective of this study was to determine the amino acid (AA) digestibility and excreta bacterial populations of whole yeast and autolysed yeast in caecectomised laying hens. Six caecectomised laying hens were housed individually in metabolism cages and fed either a basal diet or one of two diets, containing either whole yeast or autolysed yeast. The diets and hens were applied in a duplicate 3 × 3 Latin square design. In each period, the laying hens were fed their respective diet for 8 d and excreta samples were collected quantitatively twice daily during days 5-8. On day 9, a sterile plastic bag was attached to the cloaca of each hen to collect excreta for microbiota analysis. The crude protein (CP) contents were 342 and 334 g/kg dry matter (DM) in the whole yeast and autolysed yeast, respectively. The contents of neutral detergent fibre and acid detergent fibre were higher in the whole yeast (158 and 21 g/kg DM, respectively) than in the autolysed yeast (65 and 1 g/kg DM, respectively). Both in vitro protein digestibility and AA digestibility in the caecectomised laying hens were higher (p < 0.05) in the autolysed yeast than in the whole yeast. However, there were no differences (p > 0.05) in the gene copy numbers of bacteria among the experimental diets. This suggests that yeast products derived from sugarcane ethanol production could be considered alternative protein sources. Accurate information on the AA digestibility of yeast products is important for estimating their contribution to digestible AA supply and for their appropriate inclusion in laying hen diets.

This study investigated the effects of graded levels of dietary silymarin (SM) supplementation at 0, 2, 4, 6, 8, 10 and 12 [g/kg] diet on growth performance, energy and nutrient availability, intestinal morphology, mucous cell populations and hepatic antioxidant status in unchallenged broiler chickens. Growth performance variables, including daily feed intake, weight gain and mortality‑corrected feed conversion ratio, were not influenced (p > 0.05) by SM inclusion. Although N-corrected apparent metabolisable energy, dry matter and nitrogen retention coefficients differed among treatments (p < 0.001), these effects were inconsistent and displayed no dose-dependent pattern (p > 0.05). No changes in breast meat colour were observed (p > 0.05). Jejunal villus morphometry and mucous cell types were largely unaffected by dietary treatments. Villus height and width did not vary among diets (p > 0.05), and although crypt depth, mucosal thickness and mucous cell subtype counts showed some treatment-specific differences (p < 0.001), none followed a consistent dose-response dependent trend. All measured values fell within expected physiological ranges for broilers at this age, indicating that SM exerted no substantive impact on intestinal structure or mucosal secretory function. Similarly, hepatic responses to SM were minimal, as the relative liver weight did not differ among treatments (p > 0.05). Compared to the control, hepatic coenzyme Q10 concentration increased in 12 [g/kg] SM (p < 0.05). However, the rest of the hepatic antioxidants showed limited or no sensitivity to SM supplementation, and no clear dose-related effects were detected (p > 0.05). Overall, SM supplementation significantly affected some variables related to gut physiology, hepatic antioxidant status and energy and nutrient availability, although these effects were not consistently related to dietary SM inclusion level.

Steviol glycosides (stevioside, STE) are natural, non-caloric sweeteners derived from Stevia rebaudiana that possess antioxidant, anti-inflammatory, and metabolic-regulatory properties potentially beneficial for livestock production, but their effects in growing-finishing pigs remain largely unexplored. We hypothesised that dietary STE supplementation would improve antioxidant status and thereby enhance carcass traits and pork quality in growing-finishing pigs. A total of 36 pigs (initial body weight 28.00 ± 0.41 kg) were randomly allotted to two dietary treatments (six replicate pens per treatment, three pigs per pen) and fed a basal diet with or without 200 mg/kg STE for 90 days. Dietary STE improved average daily gain (ADG) and the feed-to-gain ratio (F/G) during the early growing phase (25-50 kg; p < 0.05) and tended to increase final body weight over the entire trial. STE supplementation reduced serum urea and malondialdehyde (MDA) concentrations and increased serum immunoglobulin G (IgG), glutathione peroxidase (GSH-Px) activity, and total antioxidant capacity (T-AOC) (p < 0.05); in muscle, GSH-Px and total superoxide dismutase (T-SOD) activities increased and MDA concentration decreased (p ≤ 0.05), with no effect on T-AOC or catalase (CAT) activity. STE also increased carcass weight, carcass length, loin eye area, 24-h meat redness (a * 24 h), and intramuscular fat content (p < 0.05), but did not affect muscle protein content (p = 0.970). At the transcriptional level, STE downregulated myosin heavy chain (MyHC) IIb and upregulated MyHC IIa expression in the longissimus dorsi, and increased fatty acid synthase (FASN) mRNA expression in muscle while decreasing FASN, insulin-like growth factor 1 (IGF-1), and hormone-sensitive lipase (HSL) mRNA expression in liver. These gene expression changes are consistent with, but do not directly demonstrate, a shift towards a more oxidative muscle fibre profile and tissue-specific regulation of lipid metabolism; histological or protein-level confirmation is warranted. Overall, dietary supplementation with 200 mg/kg STE improved early-phase growth performance, antioxidant status, and several carcass and meat quality traits in growing-finishing pigs, supporting its potential as a functional feed additive; further dose-response studies are needed to identify the optimal inclusion level.

Efficient utilisation of dietary protein improves ruminant performance and reduces nitrogen losses to the environment. Soybean meal (SBM) serves as a major protein source in ruminant nutrition but exhibits high ruminal crude protein (CP) degradability. Tannins reduce ruminal protein degradation, yet the effect of hydration duration during tannin treatment remains poorly defined. In this in-vitro study, we evaluated how three hydration durations (8 h, 16 h, 24 h) combined with chestnut wood extract (CWE) and quebracho wood extract (QUE) tannins at 50 and 100 g/kg influence dry matter (DM) and CP degradability and digestibility of SBM. Hydration duration significantly interacted with tannin treatment for DM degradability and digestibility (p < 0.05). Descriptively, tannin-treated samples showed lower in-vitro CP degradability than the corresponding controls across hydration durations. The lowest CP degradability was observed for CWE at 100 g/kg (380 ± 24.8 g/kg CP) at 8 h hydration, whereas CP digestibility for this treatment was lowest after 16 h hydration and increased to 984 ± 2.8 g/kg CP after 24 h. The highest by-pass CP values were observed after 8 h hydration, ranging from 397 ± 38.9 g/kg CP (QUE 50 g/kg) to 591 ± 25.3 g/kg CP (CWE 100 g/kg). DM degradability decreased by 7% (QUE 100 g/kg at 24 h) to 26% (CWE 100 g/kg at 8 h). These results suggest an 8 h hydration duration may provide the most favourable balance between protein protection and maintained nutrient digestibility.

The nutritional evaluation of concentrated lipid sources is essential for improving the precision of energy values used in pig diet formulation. This study evaluated the effects of soybean oil, poultry fat, and pork fat on in vivo digestibility, in vitro dry matter digestibility, and net energy estimates in growing pigs. Twenty castrated male pigs were assigned to a completely randomised design with four treatments and five replicates. The experimental diets consisted of a control diet without added oil or fat and diets with 8% replacement of the control diet with soybean oil, poultry fat, or pork fat. Mean values were compared with the control diet using Dunnett's test. Concentrated lipid sources increased ether extract digestibility and dietary energy values compared with the control diet. Estimated net energy values were 8,139, 8,222, and 8,161 kcal/kg for soybean oil, poultry fat, and pork fat, respectively. None of the lipid-containing diets differed from the control diet in in vitro dry matter digestibility, indicating limited sensitivity of the assay to detect effects of lipid source inclusion. Overall, the results suggest that concentrated lipid sources increase dietary energy utilisation in growing pigs. Net energy values should be considered experiment-specific estimates.

This experiment investigated the effects of clove essential oil (CEO) and a commercial condensed tannin (CT) on digestibility, rumen fermentation, blood metabolites, milk yield, milk composition, and fatty acid profile in lactating goats. Nine multiparous goats were used in a triplicated 3 × 3 Latin square design over three 21-d periods, with 14 d for diet adaptation and 7 d for data and sample collection. Goats were fed a basal diet without supplementation (CON), supplemented with CEO at 2 g/goat/d (CEO diet), or with CT at 2% of CT on a dry matter (DM) basis (CT diet). Digestibility of DM, organic matter, crude protein, and neutral detergent fibre was higher (p < 0.05) with the CEO diet than with the CON and CT diets. Total volatile fatty acid concentration and acetate proportion were increased (p < 0.05) in the CEO diet compared to the CT and CON diets. Both the CEO and CT diets lowered (p < 0.05) ruminal ammonia-N concentration and rumen methane production per kg DM compared with the CON diet. Blood urea concentration decreased (p = 0.02) on the CEO and CT diets versus the CON diet. Daily milk yield and the yields of fat-corrected milk, fat, protein, lactose, non-fat solids, and milk fat concentration were higher (p < 0.05) with the CEO diet than with the CT and CON diets. Polyunsaturated fatty acids (PUFA) increased (p < 0.01) while saturated fatty acids (SFA) decreased (p = 0.001) in the CON and CT diets compared with the CON diet. The CEO diet further increased monounsaturated fatty acids (MUFA) (p = 0.01) and improved the SFA/MUFA ratio (p < 0.01) compared to the CON diet. The proportion of C18: 0 (stearic acid) increased (p = 0.05) in the CEO diet compared with the CT and CON diets. In addition, C18: 1 n-9c (oleic acid) increased (p < 0.01) most in the CEO diet, followed by the CT diet, and then the CON diet. Compared with the CON diet, the proportions of C18: 2 n-6c (linoleic acid) and C18: 2 trans (TT) also increased (p < 0.05) in both the CT and CEO diets. In conclusion, both additives successfully mitigated environmental impacts by suppressing ruminal methane emissions and ammonia-N concentration. However, CEO demonstrated clear superiority over CT by simultaneously enhancing nutrient digestibility, increasing milk and component yields, and optimising the milk fat profile by reducing SFA while increasing MUFA and oleic acid content.

The strategic focus on improving the quality of eggs, which are foundational and nutritious foods, offers a straightforward method to elevate the nutritional value of diets. However, studies on strategies to improve egg quality remain limited. Lycopene, a lipophilic carotenoid derived from red fruits and vegetables, enhances growth performance, lowers blood lipid levels, and improves antioxidant capacity. Therefore, in this study, a total of 360 laying hens were randomly divided into four groups. The CON group was fed a basal diet, the LYC group was supplemented with 120 mg/kg lycopene, whereas the CCBA group was supplemented with 60 mg/kg β-carotene, 250 mg/kg curcumin, 250 mg/kg allicin, and 500 mg/kg sodium butyrate, the CLYC group replaced β-carotene with lycopene, while other ingredients remained the same. For the yolk score, the LYC group significantly increased at days 14, 21, 28, 35, and 42 compared to the CON group (p < 0.05). The UFA and Vitamin A contents were significantly elevated in the LYC group compared to the CON group (p < 0.05). The result of lipid metabolism genes expression showed that the relative expression of ACC, LXR-α, and PPAR-α significantly increased in the CLYC and CCBA groups compared with the CON group (p < 0.05), the relative expression of LXR-α in the LYC group remarkably higher than that in the CON group (p < 0.05). Additionally, heatmap analysis showed that Turicibacter and Veillonella were enriched in the LYC group. The results of this study indicated that lycopene supplementation significantly improved egg quality, hepatic lipid metabolism, and systemic immunity in laying hens. Furthermore, analysis of gut revealed that lycopene increased ileal goblet cell numbers and IgA production, while enriching beneficial microbiota.

The present study evaluated the effects of different dietary oil and fat sources on growth performance, serum biochemical profile, nutrient digestibility and carcass characteristics of broiler chickens. A total of 300 day-old Cobb 430Y broiler chicks were randomly allotted to five dietary treatments, each comprising six replicates of ten birds. Birds were fed iso-caloric and iso-nitrogenous diets containing different lipid sources: soybean oil (T1), palm oil refinery by-product (T2), palm oil (T3), rice bran oil (T4) and lard (T5). Oils and fats were included at 3.0% during the pre-starter phase and 5.0% during the starter and finisher phases. Broilers fed lard (T5) exhibited significantly higher (p < 0.05) body weight gain, improved feed conversion ratio and the highest performance index (p < 0.01), followed by T2 and T1. The best protein efficiency ratio (p < 0.05) was observed in T1, followed by T5 and T2. Feed intake during the overall period was significantly higher (p < 0.01) in T2, T4 and T5. Serum biochemical analysis revealed significantly higher (p < 0.01) total protein and albumin levels in T5. The lowest LDL cholesterol concentration (p < 0.01) was recorded in T2, followed by T1 and T3, while serum triglycerides and total cholesterol were significantly elevated in T5 and T4. Dry matter and crude protein digestibility were significantly improved (p < 0.05) in T1, T2 and T5. Ether extract digestibility was lower (p < 0.01) in T2, whereas nitrogen-free extract digestibility was higher (p < 0.01) in all treatments except T4. Carcass yield, dressing percentage and breast meat yield were significantly higher (p < 0.01) in T1, T2 and T5. In conclusion, dietary lipid source significantly influences broiler performance and metabolic responses. Palm oil refinery by-product demonstrated comparable performance to conventional oils and may serve as a potential alternative energy source under practical feeding conditions.

This study evaluated the effects of graded dietary phytase (PHY) inclusion on feed intake (FI), weight gain (WG), feed conversion ratio (FCR), nitrogen-corrected apparent metabolisable energy (AMEn), nutrient and mineral utilisation, and phytate degradation in growing turkeys. A positive control (PC) diet was formulated to meet or exceed breeder recommendations for nutrient content. A negative control (NC) diet was reformulated from the PC to contain the same calcium (Ca) to P ratio, but a reduced total P. The NC diet was subdivided and supplemented with PHY at 0, 100, 1000, 10,000, or 100,000 FTU/kg, resulting in six experimental diets. Seventy-two female BUT Premium turkey poults (mean body weight 1,885 g; SD ± 210 g) were randomly allocated to 36 raised-floor pens (two birds per pen; 0.36 m2 per pen). Each diet was fed for 9 days, from 68 to 77 days of age to six replicate pens following randomisation. Birds fed the NC diet exhibited significantly reduced FI, WG, dry matter retention (DMR), and AMEn compared with birds fed the PC diet, confirming the adverse effects of marginal phosphorus supply. Supplementation with PHY at inclusion levels ≥1000 FTU/kg largely alleviated these deficiencies. Increasing dietary PHY concentration resulted in significant positive dose-dependent responses in WG, FCR, DMR, nitrogen retention, and AMEn. Marked reductions (p < 0.001) in excreta inositol phosphates (IP) were observed at PHY doses ≥1000 FTU/kg. Concentrations of IP and free inositol (IN) followed expected responses to increasing PHY dose, involving linear and quadratic components. Mineral retention coefficients were generally lower in turkeys fed the NC diet than in those fed the PC diet, except for phosphorus retention, which did not differ between control diets. Increasing PHY dose produced significant positive linear responses (p < 0.001) in the retention of calcium, magnesium, iron, potassium, manganese, zinc, and phosphorus, particularly at ≥1000 FTU/kg, Overall, the results confirm that turkeys respond to high PHY inclusion in a manner broadly consistent with broilers. Very high PHY levels (super- and mega-doses) provided continued additional benefits for growth performance beyond 1000 FTU/kg, along with continued improvements in nutrient retention, and the data suggest the optimum dose was beyond that investigated in this study.

Light weaning body weight (LWBW) piglets exhibit inferior growth performance, and their energy requirement vary dynamically with increasing body weight. Although high-energy diets improve growth, they risk impairing liver health. Therefore, we investigated a multi-phase, high-net energy (HNE) regimen with stepwise-decreasing energy concentration with increasing body weight, assessing its impact on growth performance, liver health, and gut microbiota in LWBW piglets. Thirty LWBW piglets (28 days of age, initial body weight: 6.09 ± 0.47 kg) were randomly assigned to two groups; a high-net energy diet based on the energy requirement curve (HNE diet), and a low-net energy diet formulated according to NRC recommendations (NRC diet). Each treatment consisted of five physically separated pens (experimental unit and replicate, n = 5), with three piglets housed per pen throughout the 42-day trial. Results showed that the HNE diet tended to reduce feed to gain ratio (p = 0.075) but failed to improve average daily gain (ADG) in LWBW piglets. Relative to the NRC diet, the HNE diet exhibited significant elevations in serum concentrations of glucose, triglycerides, total cholesterol, bile acids, and alanine aminotransferase (p < 0.05), as well as in hepatic the content of malondialdehyde and the activity of total superoxide dismutase contents (p < 0.05). In addition, HNE diet upregulated the mRNA expression of lipogenic genes acetyl-CoA carboxylase (p < 0.05) and fatty acid synthase (p = 0.076), along with the protein levels of pro-inflammatory cytokines and endoplasmic reticulum stress marker glucose-regulated protein 78 (p < 0.05). Serum metabolomic profiling revealed that HNE diet induced alterations in a series of metabolites associated with oxidative stress, specifically increasing the concentrations of LysoPC, LysoPE, and guanosine while reducing levothyroxine abundance in LWBW piglets. Prevotella copri was the key microbe in the colon of HNE group piglets. Furthermore, HNE diet significantly elevated colonic concentrations of acetate, propionate, and butyrate (p < 0.05). Collectively, these findings suggest that the high-net energy diet reduced the feed-to-gain ratio, it did not significantly increase the ADG of piglets. This phenomenon may be associated with liver function and gut microbiota. Notably, the early high-net energy diet induces a systemic metabolic alteration that persists after dietary normalisation.

The aim of this experiment was to investigate the effects of dietary lipoic acid (LA) supplementation on meat quality and antioxidant regulation mechanisms in finishing pigs subjected to oxidative stress challenge induced by diquat (DQ). A 2 × 2 factorial design was applied using 24 Large White barrows (70.64 ± 3.61 kg; n = 6 per group) assigned to Control, LA (800 mg/kg LA), DQ (8 mg/kg BW) and DQ + LA treatments. DQ was administered intraperitoneally on day 15, and pigs were slaughtered on day 29 for collection of Longissimus dorsi samples. Carcass traits, meat quality traits (pH, colour, drip loss and shear force), Nrf2/Keap1 protein levels, myofiber-related genes expression (MyHC isoforms), and SOD activity and expression were analysed. We found that LA and DQ showed limited effects on carcass traits, except for a significant DQ × LA interaction on backfat thickness. DQ reduced pH24 h and increased L24 h, indicating accelerated post-mortem acidification and altered meat colour. LA increased a45 min and significantly affected shear force, with a pronounced interaction under oxidative stress. DQ markedly upregulated Nrf2 protein expression, while LA partially attenuated this increase without affecting Keap1. DQ and LA significantly modulated myofiber type-related genes, with stress-dependent interactions observed for MyHC I and MyHC IIb. Moreover, DQ enhanced SOD mRNA, protein expression and enzyme activity, whereas LA increased SOD mRNA expression independently of oxidative stress, with no significant interaction effects. In conclusion, dietary LA modulated antioxidant capacity and muscle fibre gene expression in finishing pigs challenged with DQ; However, its effects on meat quality were stress-dependent rather than uniformly beneficial, indicating that further studies are needed to clarify its role in maintaining overall pork quality under diquat-induced oxidative stress challenge.

Feed scarcity during the long dry season is a major constraint to livestock production in the Sahel. During this period, fodder trees provide a valuable source of nutrients. This study assessed sheep feeding preferences for five woody species from Senegal's silvopastoral zone (Adansonia digitata, Acacia tortilis subsp. raddiana, Balanites aegyptiaca, Guiera senegalensis, Khaya senegalensis) and evaluated their enteric methane mitigation potential. A cafeteria-style trial quantified voluntary intake, feeding time and preference coefficients of four sheep for fresh and air-dried leaves over 5 consecutive days during daily 30-min sessions. In vitro gas production assays, conducted with and without polyethylene glycol (PEG), measured total gas, methane concentration, and estimated digestibility. Leaves of A. raddiana and B. aegyptiaca showed high crude protein contents (168.7 and 167.0 g/kg DM) and metabolisable energy values (8.7 and 12.1 MJ/kg DM). In contrast, G. senegalensis and K. senegalensis contained high fibre (aNDF: 586.6 and 484.8 g/kg DM) and condensed tannins (35.8 and 66.9 g/kg DM). PEG addition increased gas production in A. raddiana, G. senegalensis and K. senegalensis, confirming tannin inhibition of fermentation. Sheep showed a clear preference (p < 0.001) for ingesting fresh A. raddiana (298 g/animal) and B. aegyptiaca (270 g/animal) leaves; feeding time and preference coefficients followed the same pattern. Preference coefficients were positively associated with crude protein and negatively linked to fibre and tannin contents, while tannin-rich species also produced less methane in vitro. Overall, A. raddiana and B. aegyptiaca emerged as valuable indigenous fodder resources for improving dry-season nutrition and potentially contributing to climate-smart livestock systems in the West African Sahel.

Phosphorus (P) has several vital functions, and its excretion may have environmental impacts. Thus, an adequate P supply is of utmost importance to meet the requirements of the animals while avoiding unnecessary excretion. Calculation of the P requirement of dairy cows considers factors such as P secretion via milk and P deposition in growing or pregnant animals. Furthermore, a value for the efficiency of P utilisation is applied, which should be determined in animals fed at a marginal P supply to maximise absorption. The objective of the present meta-analysis was thus to estimate the efficiency of P utilisation, accounting for P supply in dairy cows. The dataset included 399 observations published in 77 studies on dairy cows. Data on P intake and faecal P excretion were used to calculate standardised P digestibility, corrected for faecal endogenous P losses. Furthermore, the P requirement and the P supply relative to the requirement were calculated. Linear and non-linear regressions were performed to analyse the relationship between P excretion via faeces and urine and standardised P digestibility with P intake and P supply. Phosphorus intake exceeding the net requirement of dairy cows was excreted with faeces to a large extent, while urinary P excretion had only minor quantitative importance below 5.2 g P/kg DM of feed. The estimated standardised P digestibility at a marginal P supply was 83% and was interpreted as the estimate for efficiency of P utilisation. The data did not indicate that differentiation in P utilisation efficiency between mineral and organic P sources in the feed or by lactation stage is helpful for adequate P supply of dairy cows.

Two isoenergetic (12.05 MJ/kg ME) and isonitrogenic (approximately 200 g/kg CP) basal diets were prepared using 670 g/kg of wheat with low fibre and/or high fibre contents. Each basal diet was divided into four portions: one remained as is and fed as control (C); the second was the C supplemented with 100 FXU/kg of a commercial xylanase (XYL); the third was the C plus 20 g/kg of inulin (IN) powder; and the fourth was the C supplemented with both XYL and IN at the same inclusion rates, resulting in a total of eight experimental diets. A study was conducted from 10 to 21 days of age involving 320 female Ross 308 broiler chickens. Each diet, in meal form, was fed ad libitum to eight pens, five birds each, following randomisation. Supplementary XYL increased dietary nitrogen corrected apparent metabolisable energy (AMEn) (p < 0.001), dry matter retention (DMR), daily feed intake (FI), weight gain (WG) and reduced feed conversion ratio (FCR) (p < 0.05). Dietary IN tended (p < 0.01) to increase WG and reduce FCR and dietary wheat did not have an impact on growth performance variables (p > 0.05). Birds fed XYL had reduced relative weight of the pancreas (p < 0.050) and there was XYL by IN interaction (p < 0.05) on relative weight of the caeca as it was greater for those fed XYL and IN. No other changes in relative weight of the gastrointestinal tract organs were observed (p > 0.05). Bird fed XYL or IN had greater (p < 0.05) butyric acid (BA) concentration in caecal content. Feeding XYL led to reduced acetic (AA) and propionic acid (PA) concentrations in caecal excreta (p < 0.05) and to a greater BA:AA ratio (p < 0.001). Dietary IN increased blood serum glutathione peroxidase (GSH-Px) (p < 0.05) and XYL increased concentration of hepatic coenzyme Q10 (p < 0.05). The type of dietary wheat did not have an impact on any of the studied variables, suggesting that birds were able to tolerate the fibre contents in this study. It seems that both IN and XYL, can serve as feed enhancers that potentially may promote antioxidant status of birds and help poultry to cope with various stress factors during production. The study further confirms that supplementing wheat-based diets with XYL may be a strategy to mitigate the reduction in available energy and to increase nutrient availability in broiler diets.

The nutrient composition of the pea grain fraction that escapes precaecal digestion may vary in response to the pea variant, affecting its fermentation characteristics in the hindgut. Quantifying the formation of fermentation end products in vivo remains challenging. Therefore, this study investigated the digestion and fermentation characteristics of 12 pea variants using two combined in vitro assays. In vitro indigestible solids (IVIS) of pea grains, representing the fraction of pea grains escaping precaecal digestion, were incubated for 48 h using a modified Hohenheim gas test with pig faeces as inoculum. Gas production was recorded at nine time points, and NH4[+]-N and volatile fatty acids (VFA) were measured at 8 and 24 h. Precaecal disappearance was high for starch and crude protein (>94%), whereas fibre fractions remained largely undigested (<16%) and were the most abundant and variable fraction in the IVIS. Incubated IVIS differed in potential gas production and maximum rate of gas production among pea variants (p < 0.001, 46.7 to 73.9 mL/200 mg dry matter and 2.9 to 5.1 mL/h, respectively). For metabolite concentrations, an effect of the IVIS was observed for NH4[+]-N and VFA at 8 and 24 h (p < 0.001). Multivariate regression showed a positive association of acid detergent fibre with the potential gas production (p < 0.001, R[2] = 0.82). The concentration of crude protein was positively associated with the NH4[+]-N concentration at 8 and 24 h (p < 0.001, R[2] = 0.85, R[2] = 0.86). The crude fibre concentration was negatively associated with the branched-chain fatty acid concentration at 24 h (p = 0.001, R[2] = 0.70). Starch concentration was positively associated with gas production at 2 h (p < 0.016, R[2] = 0.49) and propionate concentration at 8 h (p < 0.038, R[2] = 0.86). To conclude, early-stage propionate production is driven by the precaecal indigestible starch, whereas the fermentation potential is primarily determined by the precaecal indigestible fibre fractions. Formation of metabolites by protein fermentation depends on the concentration of precaecal indigestible protein but may be inhibited with higher fibre concentrations. The differences in fermentation characteristics among IVIS of pea variants were associated with the analysed nutrient composition of the IVIS but not with those of the original grains.