Postmortem changes in skeletal muscle, particularly rigor mortis and the subsequent tenderization process, play a central role in determining meat quality and palatability. Proper progression of rigor mortis is essential, as its disruption leads to severe deterioration in meat texture and eating quality. Although the biochemical mechanisms underlying rigor mortis have been extensively studied, most investigations rely on simplified experimental systems and largely neglect the contribution of endogenous low-molecular-weight compounds present in muscle tissue. Imidazole dipeptides, such as carnosine, are abundant in skeletal muscle and are known to contribute to intracellular homeostasis through antioxidant and metal-chelating properties. Recently, these compounds have also been implicated in the regulation of calcium sensitivity in muscle contraction models. In the present study, we investigated the potential involvement of carnosine in rigor mortis by examining its effects on actomyosin ATPase activity under postmortem-like conditions. Under acidic and low-calcium conditions, which are unfavorable for actomyosin ATP hydrolysis, carnosine significantly enhanced ATPase activity. This enhancement was accompanied by increased tryptophan autofluorescence in the myosin head region upon ATP addition, suggesting an increased affinity between myosin and ATP. These findings indicate that carnosine facilitates the actomyosin ATPase cycle under postmortem conditions by enhancing calcium sensitivity and stabilizing ATP-myosin interactions. Our results suggest that endogenous carnosine contributes to the orderly progression of rigor mortis by promoting ATP depletion and contractile activity in postmortem skeletal muscle, providing new insight into the biochemical factors influencing meat quality and postmortem muscle behavior.

Tannin extracts (TE), composed of condensed tannins from quebracho and hydrolyzable tannins from chestnut, have been studied as functional feed additives to improve growth performance in beef cattle, but reported effects vary with TE composition, dose, dietary protein, and co-additive. This meta-analysis evaluated TE supplementation effects on average daily gain (ADG), dry matter intake (DMI), and gain:feed (G:F) in growing and finishing beef cattle, using 162 treatment records from 43 published studies involving > 22,000 animals, mostly bulls and feedlot-based studies including grazing and individually pen trials. Additional analyses included conditional independence tests for monensin use, forest and mosaic plots, and subset analyses for diets with or without monensin. Meta-regression indicated that TE supplementation was associated with increases in ADG (P < 0.001), DMI (P < 0.001), and G:F (P = 0.024). The ADG response was nonlinear; quadratic models indicated an optimal inclusion of ∼0.30% of dietary DM for maximizing weight gain. The disproportionate increase in ADG relative to DMI is consistent with improved nutrient utilization. The TE-ADG relationship was stronger at lower crude protein intake (P = 0.0525), however, because crude protein intake is not a direct proxy for rumen-degradable nitrogen supply and may co-vary with diet formulation and co-additives (e.g., ionophores and/or NPN sources), this pattern should be interpreted as context-dependent rather than as evidence of a universal mechanism. A conditional independence test also suggested that the TE-associated ADG responses were not independent of monensin use, suggesting a possible synergy effect, though additional studies are needed to confirm this pattern. Overall, TE appears to be a context-dependent additive rather than a universal growth promoter, and responses did not necessarily require doses near the model-derived optimum; benefits were also detectable at lower inclusions (e.g., ∼0.08% of dietary DM) in some contexts. Further research is needed to refine dosing strategies, better characterize TE chemistry, and evaluate environmental outcomes in dedicated studies.

This experiment evaluated growth, physiological responses, and puberty attainment in heifers reared in drylots with different stocking densities. A total of 240 heifers (75% Angus × 25% Brahman) were used. Heifers were ranked by age (270 ± 1 d), body weight (BW on d -3; 232 ± 2 kg) and temperament score on d 0, and assigned to drylot pens with: a) 14 m2/heifer (HDENS), b) 28 m2/heifer (MDENS), c) 42 m2/heifer (LDENS), or to pastures with 1,380 m2/heifer (CON). Each pen or pasture (n = 6/treatment) housed 10 heifers. Negligible forage was available for CON, and all treatments received the same limit-fed diet (∼9 kg/heifer daily, dry matter basis). Shrunk BW was recorded on d -3 and 171 to calculate BW gain. Heifers were fitted with an ear tag on d 0 to record behavioral responses. Blood samples were collected weekly for plasma progesterone analysis. Whole blood samples were collected on d 0, 58, 114, and 170 for mRNA isolation. Hair samples from the tail switch were collected on d 0, 30, 58, 85, 114, 142, and 170. Data were analyzed with pen or pasture as experimental unit. No treatment effects were detected (P = 0.92) for BW gain (∼0.647 kg/d). Heifers from CON spent more time eating (P < 0.01) and less time in other activity categories (active, highly active, and non-active; P ≤ 0.05) compared with heifers reared in drylots. Hair cortisol concentrations were greater (P ≤ 0.02) for HDENS compared with CON and MDENS on d 30, greater (P ≤ 0.04) for HDENS compared with all other treatments on d 58 and 142, and less (P ≤ 0.05) for CON compared with all drylot treatments on d 170 (treatment × day; P = 0.08). Expression of heat shock protein (HSP)-70 mRNA was greater (P ≤ 0.02) for HDENS compared with all other treatments on d 170 (treatment × day; P = 0.04). Expression of HSP-72 mRNA was greater (P < 0.01) for LDENS compared with all other treatments on d 114, and greater (P < 0.01) in HDENS compared with all other treatments on d 170 (treatment × day; P < 0.01). A greater (P ≤ 0.05) proportion of CON were pubertal by week 22 of the experiment compared with all other treatments, and compared with MDENS and HDENS on week 23 (treatment × day; P < 0.01). In summary, rearing heifers in drylots with high stocking density (14 m2/heifer) increased chronic stress and delayed puberty compared with pasture heifers, whereas reducing drylot stocking density (28 or 42 m2/heifer) attenuated stress responses but did not benefit heifer reproductive development.

Tail biting compromises the welfare and performance of pigs. Understanding the dynamics of this behavior is essential for developing management strategies to minimize outbreaks. We used social network analysis (SNA) to evaluate the effect of group size on tail-biting interactions among pigs and to examine differences in tail-biting network position between barrows and gilts, and biters and non-biters. Pigs (n = 315, initial weight = 22.1 ± 3.76 kg) with intact tails of mixed sexes were housed in small (9 pigs/pen) or large (18 pigs/pen) pens on slatted floors for 14 weeks until market weight (120.2 ± 11.47 kg). Floor and feeder space allowances were identical for pigs in both group sizes. Growth performance, tail injury, and behavior were recorded. Videos recorded the day before the first TBO were manually reviewed to document tail-biting events and identify pig roles. The top 25% of pigs responsible for the most tail-biting incidents were classified as tail-biters, and the remaining pigs as non-biters. Tail-biting network metrics were calculated using RStudio. Data were analyzed using SAS. Pigs in small pens exhibited higher density, reciprocity, out- and in-degree centrality, betweenness centrality, and closeness centrality (all P < 0.05), suggesting greater direct and indirect involvement in tail-biting interactions than pigs in large pens. Gilts had higher out-degree centrality (P < 0.01), indicating they initiated more tail biting than barrows. Both sexes had similar in-degree centrality, suggesting they were bitten equally. In gilts, biters tended to have lighter final weight (P = 0.08) and lower ADG (P = 0.10) and were injured less frequently (P = 0.02) by tail biting than non-biters. In both sexes, biters and non-biters had similar in-degree centrality, suggesting that they were bitten equally. These results indicate that pigs housed in different group sizes exhibit different social structures and positions in tail-biting networks, which potentially affects tail damage. Further research should evaluate network metrics across a wider range of group sizes and during multiple TBO.

Dietary fiber is defined as the undigestible carbohydrates and lignin fractions of plant-feed ingredients. The most complete and representative analysis of fiber is the total dietary fiber (TDF) analysis, which includes the soluble dietary fiber (SDF) and the insoluble dietary fiber (IDF). There is, however, a lack of data for concentrations of SDF, IDF, and TDF in feed ingredients commonly used in diets for pigs. Therefore, work was conducted to quantify fiber fractions of plant feed ingredients to establish a database for SDF, IDF, and TDF in feed ingredients commonly used in animal nutrition. A total of 846 samples were analyzed for dry matter (DM) and for IDF and SDF, and TDF was calculated as the sum of IDF and SDF. Analyzed values for SDF, IDF, and TDF were corrected to 88% DM. For each feed ingredient, means and standard deviation were calculated. Results indicated that values for TDF were in the range of 3% to 35% for cereal grains, from 0% to 68% for cereal grain coproducts, from 3% to 68% for oilseeds and oilseed co-products, and in the range of 3% to 82% for other plant-based feed ingredients. In conclusion, the present work resulted in generation of a database for SDF, IDF, and TDF in feed ingredients often included in diets for pigs and other animals.

Abstract Exploring how residual methane production (RMP) relates to productivity may reveal opportunities for selecting animals with lower methane emissions without impacting performance. This trial aimed to evaluate differences in average daily gain (ADG), dry matter intake (DMI), feed efficiency, body composition and gaseous exchange in growing beef heifers with divergent phenotypes for RMP. Growing beef heifers (n = 97; initial BW = 264 ± 25 kg) with high genetic variability were assigned randomly to one of two blocks. Both blocks were evaluated during an 84-day feed efficiency test using individual feed bunks (American Calan Inc.), during which time individual DMI and BW were recorded to determine ADG and feed efficiency. Carcass ultrasound data were collected at the end of the study. Each animal also participated in an energy metabolism study, that included four consecutive days of total fecal and urine collections and one day of methane (CH4), carbon dioxide (CO2), and oxygen (O2) exchange measurements using headboxes (HB) through an indirect calorimetry method. All heifers were fed a common diet of 80% corn silage, 15% dried distillers grains, and 5% supplement (DM basis), offered ad libitum. Residual methane production was calculated within block from the regression of CH4 on metabolic body weight (MBW) and DMI measured while heifers were in the HB. Heifers were divided into one of three RMP classes (± 0.5 SD from the mean block RMP). Data were analyzed using a mixed model including RMP classification and block as fixed effects. Low RMP heifers emitted 27.8% less CH4 (g/d; P &amp;lt; 0.001) and 32.3% less CH4 yield (g/kg DMI; P &amp;lt; 0.001). Similarly, compared to high RMP heifers, low RMP heifers produced 10.4% less CO2 (g/d; P = 0.033) and consumed 11.6% less O2 (g/d; P = 0.011). During the feed efficiency test, there were no differences in initial and ending BW, ADG, DMI, gain-to-feed ratio, longissimus muscle area or intramuscular fat (P &amp;gt; 0.399) between heifers with high and low RMP phenotypes. In terms of metabolism traits, there were no differences for MBW, DMI, or dry matter digestibility (P &amp;gt; 0.691) between heifers with divergent RMP phenotypes. Using Pearson’s correlations, DMI during the feed efficiency test was positively associated with ADG (r = 0.55; P &amp;lt; 0.001) and DMI measured in the headbox was positively associated with CH4 production (r = 0.66; P &amp;lt; 0.001), highlighting the role of feed intake in growth and CH4 emissions. Gain (r = 0.16; P = 0.128) and feed efficiency (r = -0.04; P = 0.674) were not associated with RMP; however, low RMP heifers emitted 27.8% less methane (g/d). These results suggest that selecting for reduced RMP could lower methane emissions without impacting productivity.

Genetic selection for high growth performance has markedly improved poultry production efficiency. However, gastrointestinal responses to selection for high body weight (HBW) remain poorly characterized. In this study, ten chickens from each of the primitive and HBW lines of Lueyang Black-boned chickens were monitored for growth performance from 1 to 180 days of age, and gastrointestinal morphology and microbial composition were compared at 180 days. Gastrointestinal structural traits were analyzed using t-tests, whereas microbial profiles were evaluated using non-parametric statistical methods. Compared with the primitive line, the HBW line exhibited: 1) Growth performance: no differences in body weight at 1 and 45 days, but significantly higher at 120 (39.82%) and 180 days (29.17%) (P < 0.05), along with a significantly lower feed conversion ratio during 45-120 days (10.17%) (P < 0.05); 2) Serum parameters: increased serum biomarkers associated with lipid transport (P < 0.05), with upward trends in glucose and uric acid concentrations (P < 0.10); 3) Organ morphology: increased weights of the crop (35.93%), gizzard (30.90%), duodenum (46.07%), cecum (33.80%), pancreas (32.74%), and liver (38.11%) (P < 0.05), while glandular stomach weight remained unchanged; and elevated villus height-to-crypt depth ratios in the duodenum (130.18%) and ileum (40.95%) (P < 0.05). 4) Microbial alterations: Segment-specific microbial alterations indicated an adaptive pattern characterized by enhanced nutrient utilization but attenuated immune-related functions. Specifically, enriched nutrient-associated taxa included crop Enterococcus and Bacillus, duodenal Lactobacillus, ileal Enterococcus, and cecal Bacteroidales. In contrast, immune-related functional shifts were characterized by crop xenobiotic biodegradation pathways, suppressed duodenal Salmonella- and immune-related signaling pathways, altered ileal alanine, aspartate, and glutamate metabolism, and cecal isoquinoline alkaloid and peptidoglycan biosynthesis pathways. Collectively, this study demonstrates that genetic selection for HBW has driven enhanced nutrient utilization in the gastrointestinal tract while attenuating microbiota-related immune functions, thereby providing a theoretical basis for precision nutrition strategies in poultry.

Research has demonstrated the essential functions of circular RNAs (circRNAs) in testosterone production and spermatogenesis across various ruminant species. Nevertheless, the expression dynamics and biological activities of circRNAs in Leydig cells (LCs) are still not well understood. Herein, we identified a circular RNA that mediates LCs proliferation and testosterone synthesis, circCSNK1G3, and elucidated its underlying mechanisms. Multiple functional assays were performed to determine the biological functions of circCSNK1G3 and miR-29b in vitro. Furthermore, the relationship between circCSNK1G3 and miR-29b was confirmed using RNA pull-down analysis, fluorescence in situ hybridization (FISH), and dual-luciferase reporter experiments. Functionally, circCSNK1G3 increased testosterone levels by promoting LCs proliferation and stimulating testosterone production. Mechanistically, circCSNK1G3 operates mechanistically as an endogenous sponge for miR-29b in the cytoplasm of LCs, leading to enhanced expression of IGF1. By acting as a competitive endogenous RNA, circCSNK1G3 stimulates the biosynthesis of testosterone and the growth of LCs via the miR-29b/IGF1 axis, which may provide a potential basis for using circRNAs as target drugs to treat orchitis and azoospermia.

This study aimed to evaluate the effects of supplementing two vitamin D sources on reproductive performance, egg quality, and plasma biochemical indices of aged duck breeders, and to estimate vitamin D requirements and relative bioavailability from these two sources. A total of 180 laying Pekin ducks (64 wk of age) were randomly assigned to 9 different treatments, each containing 10 replicates with 2 birds per replicate. The birds were fed a basal diet with no vitamin D supplementation or supplemented with cholecalciferol (VD3) or 25-hydroxycholecalciferol (25-OH-D3) at 250, 500, 1000, or 2000 IU/kg of feed for 15 wk. The two-way ANOVA (2 × 4 factors, without a control group) and one-way ANOVA were employed to compare the differences between 25-OH-D3 and VD3. In comparison to ducks fed the basal diet, the egg production (9 to 15 wks), ovarian weight, and the number and weight of dominant follicles increased with increasing VD3 or 25-OH-D3 levels (linear and quadratic, P < 0.05). The egg Haugh unit exhibited a linear increase with rising VD3 levels (P = 0.021) and a quadratic increase with rising 25-OH-D3 levels (P = 0.042). Additionally, the plasma calcium content increased linearly as dietary 25-OH-D3 levels increased (P = 0.001). Furthermore, diets supplemented with 25-OH-D3 resulted in higher plasma 25-OH-D3 concentrations compared to those fed VD3 (P < 0.001). According to the quadratic broken-line model, the VD3 requirements of duck breeders in terms of enhancing egg production, ovarian weight, and dominant follicle number were 906, 359, and 730 IU/kg, respectively, whereas the 25-OH-D3 requirements were 260, 324, and 308 IU/kg, respectively. Based on slope ratio comparison from multiple linear regressions of ovarian weight, dominant follicle number, and plasma 25-OH-D3 concentration, the bioavailability of 25-OH-D3 were 147%, 191%, and 211%, respectively, relative to VD3.

Efficient genetic improvement of complex traits in pigs requires a deep understanding of their genetic architecture and a comprehensive catalog of molecular markers. Here, we conducted a genome-wide association study (GWAS) and conditional analysis in 4,144 Yorkshire pigs, using 10.4 million imputed sequence variants and phenotype data on average backfat thickness at 100 kg (BFT_100). We identified 11 independently significant variants and prioritized 17 candidate genes. By integrating the Pig Genotype-Tissue Expression (PigGTEx) resources, we further performed a transcriptome-wide association study (TWAS) and colocalization analyses, revealing 27 TWAS-significant genes and 13 colocalized genes. These integrative strategies enhanced the functional signals capturing capability based on conventional GWAS, providing a deeper understanding of BFT_100 biology. Notably, NFIA, FCN1, and DBH emerged as novel candidate genes that are not previously implicated for similar traits in either the Animal QTLdb or PigBiobank. Our findings provide a reference for dissecting the genetic architecture of porcine BFT_100 and offer potential markers for precision breeding.