This experiment aimed to investigate whether supplementation of calves with different doses of oregano essential oil (OEO) could promote the development of the gastrointestinal tract and enhance the immune ability of calves by regulating the rumen microbiota. Twenty-four 70-day-old healthy and disease-free Holstein male calves were randomly divided into four groups, with the control group fed a basal diet, and the treatment group provided 4 g, 6 g, and 8 g of oregano essential oil per day in addition to the basal diet. After the 14-day pre-test, a 56-day formal test was conducted. At days 0 and 56 of the standard test period, calves were weighed, the average daily weight gain of calves during the test period was calculated, and serum samples were collected to measure the concentration of immunoglobulins (IgA, IgG, and IgM) in the serum; at day 56 of the formal test period, rumen fluid was collected from the calves, and 16SrRNA was sequenced to analyze changes in the rumen microbiota of the calves. The changes in the rumen microbiota of calves were analyzed by 16SrRNA sequencing. The results of the study showed that (1) OEO supplementation in calves significantly increased end weight and average daily gain (p < 0.05); (2) OEO supplementation in calves significantly increased serum concentrations of immunoglobulins IgA and IgM (p < 0.05); (3) OEO supplementation in calves significantly increased the abundance and diversity of rumen microbial organisms (p < 0.05); (4) OEO supplementation in calves significantly regulates the relative abundance of some species, and biomarkers with significant differences were screened by LEfSe analysis: g_Turicibacter, g_Romboutsia, f_Peptostreptococcaceae, f_Clostridiaceae, g_Clostridium_sensu_stricto_1, o_Clostridiales, g_unclassified_f_Synergistaceae, c_Coriobacteriia, o_Coriobacteriales, f_Atopobiaceae, g_Olsenella, p_Actinobacteriota, g_Defluviitaleaceae_UCG-011, f_Defluviitaleaceae, o_Corynebacteriales, g_Corynebacterium, f_Corynebacteriaceae, g_Shuttleworthia, f_Hungateiclostridiaceae, o_norank_c_Clostridia, g_Saccharofermentans, g_Streptococcus, f_Streptococcaceae, g_unclassified_o_Oscillospirales, and f_unclassified_o_Oscillospirales (p < 0.05, LDA ≥ 3); and (5) OEO supplementation in calves significantly enriched the metabolism of cofactors and vitamins pathway (p < 0.05). (6) Using Superman’s correlation analysis, we screened unclassified_c_Clostridia, Shuttleworthia, and Christensenellaceae_R-7_group, three beneficial strains for calves. (7) Daily supplementation with 8g of OEO significantly affected rumen microbiota regulation in calves.

This study hypothesized that combining oregano essential oil (OEO) and yeast cultures (YCs) would modulate rumen microbiota to promote gastrointestinal homeostasis and function. Twenty-four newborn, healthy, disease-free, crossbred Simmental male calves (birth weight ≥ 35 kg) were assigned to one of four treatments based on birth data. Treatments were as follows: (1) Control (CON), calves fed calf starter without additives; (2) OEO, calves fed calf starter containing 60 mg/kg body weight (BW) of OEO per day; (3) YCs, calves fed calf starter containing 45 mg/kg BW of YC per day; and (4) MIX, calves fed calf starter with OEO (60 mg/kg, BW) and YC (45 mg/kg, BW) combination. The experimental period lasted 70 days. Rumen fluid was collected on the final day, and 16S rRNA sequencing was performed to assess alterations in rumen microbiota. Calves fed MIX exhibited significantly greater microbial richness, species diversity, and lineage diversity (p < 0.05) compared with calves in the other groups. MIX-fed calves also showed changes (p < 0.05) in the relative abundance of certain rumen species, identified as through LEfSe analysis (LDA > 4, p < 0.05). These biomarkers included f_Rikenellaceae, g_Rikenellaceae_RC9_gut_group, g_Erysipelotrichaceae_UCG-002, c_Saccharimonadia, o_Saccharimonadales, f_Saccharimonadaceae, and g_Candidatus_Saccharimonas. Pathways enriched (p < 0.05) in MIX-fed calves involved nucleotide metabolism, lipid metabolism, glycan biosynthesis and metabolism, amino acid metabolism, terpenoids and polyketides metabolism, antimicrobial drug resistance, xenobiotic biodegradation and metabolism, antineoplastic drug resistance, and excretory system pathways. In conclusion, this study demonstrates that the OEO and YC combination enhances rumen microbial community modulation in calves more effectively than OEO or YCs fed individually or with the control diet.

This study was conducted to investigate the effects of feeding oregano essential oil, butyrate, and its mixture on the intestinal microbial diversity of calves. A completely randomized experimental design was used. Sixty-four healthy neonatal Holstein female calves with birth weight ≥ 35 kg were randomly divided into one control and three treatments (16 calves per group). The control group was fed normally, and the treatment group was fed oregano essential oil, butyrate, and their mixture, respectively. The experiment lasted for 70 days, and the lactation period lasted for 56 days. On days 55 and 70, rectal fecal samples from five calves were collected from each group for 16S rRNA amplification and sequencing. The results showed as follows: (1) the three treatments had no significant effects on the intestinal microbial community diversity, community uniformity, and community pedigree diversity of calves (p > 0.05). (2) At the phylum level, Firmicutes, Bacteroidota, Spriochatetota, Actinobacteriota, Firmicutes, and Bacteroidota gates of the main bacteria were detected in feces. (3) At the genus level, the top ten species with relative abundance detected are: norank_ F_Muribaaculaceae, Ruminococcus, unclassified_ F_ Lachnospiraceae, UCG-005, Prevotelaceae_NK3B31_Group, Prevotella, Bacteroides, Rikenellaceae_RC9_Gut_Group, and Faecalibacterium, Alloprevotella. (4) LEfSe analysis results show that the species with significant differences in the control group were f__Lachnospiraceae, o__Lachnospirales, o__Coriobacteriales, and c__Coriobacteriia, g__Megasphaera; in the essential oil group were g__Lachnospiraceae_AC2044_group, o__Izemoplasmatales, g__norank_f__norank_o__Izemoplasmatales, and f__norank_o__Izemoplasmatales; in the sodium butyrate group were g__Lachnospiraceae_NK4A136_group, and g__Sharpea, g__Fournierella; in the mixed group were g__Flavonifractor, and g__UBA1819. (5) The functional prediction analysis of calf gut microbes, found on the KEGG pathway2, shows that essential oil significantly improved membrane transport, Sodium butyrate inhibits lipid metabolism and improves the body’s resistance to disease. (p < 0.05). (6) The effects of each treatment on the intestinal microbial structure of calves did not last for 14 days after the treatment was stopped. In conclusion, the addition of oregano essential oil, butyrate, and its mixtures to milk fed to calves can modulate the microbial structure, and it is recommended that oregano essential oil and butyrate be used separately, as a mixture of the two can increase the rate of diarrhea in calves.

Previous research demonstrated the growth-promoting benefits of an essential oil and oligosaccharide blend (Stay Strong, Ralco, Inc.; EO) or an encapsulated sodium butyrate (C4; Ultramix GF, Adisseo, Inc.) fed to neonatal calves. The possibility exists that these technologies may be additive based on their individual mechanisms of action. The study objective was to evaluate EO and C4 alone or in combination when fed to Holstein heifers raised on a commercial Chinese dairy operation. Sixty-four heifers were blocked by calving day and randomly assigned to 1 of 4 treatments (n = 16/treatment) using a randomized complete block design. Treatments were: (1) Control: CON; milk fed 3×/d; (2) EO added to the milk at the rate of 1.50 g/d per head; (3) C4 added to the milk at 1.70 g/d per head; and (4) E4: EO and C4 added to the milk at the rates of 1.50 and 1.70 g/d per head, respectively. Heifers were fed acidified waste milk using an increasing- and decreasing-phase feeding program with weaning on d 56 for a 70-d experiment. Heifer birth weight was a significant covariate with heifers fed EO, C4, and E4, demonstrating greater BW (42.4, 47.0, 46.6, and 48.0 kg for CON, EO, C4, and E4, respectively) gains and ADG (605.0,672.5, 665.7, and 686.7 g/d, respectively) compared with heifers fed CON. Calf starter intake (0.558, 0.584, 0.692, and 0.624 kg/d, respectively) was greater for heifers fed C4 compared with heifers fed CON, with heifers fed EO and E4 being intermediate and similar. Feed conversions (0.439, 0.480, 0.444, and 0.477 kg/kg, respectively) were greater for calves fed EO and E4 compared with calves fed CON. Total days of fecal score = 0 was greater for heifers fed EO and lowest for heifers fed E4, with heifers fed CON and C4 being intermediate. Gains in body length and hip width were greater for heifers fed EO compared with heifers fed CON, C4, and E4. Total-tract apparent fiber (NDF and ADF) digestibility was greater in heifers fed EO and C4, intermediate for heifers fed E4, and lowest for heifers fed CON. Heifers fed EO demonstrated lower fecal Salmonella counts compared with heifers fed CON, C4, and E4. Heifers fed EO and C4 demonstrated greater blood serum total volatile fatty acid concentrations (9.75, 12.91, 11.22, 10.89 µM, respectively, for CON, EO, C4, and E4) compared with heifers fed CON, with heifers fed E4 being intermediate and similar. Heifers fed EO, C4, and E4 demonstrated greater growth performance, but the combination of EO and C4 did not further improve growth performance.

Objective: Although yak meat is valued for its distinctive flavor profile, little is known about the mechanisms underlying flavor variation among different muscle types. This study aimed to systematically investigate the differences in flavor precursors, metabolic enzyme activities, gene expression profiles, and volatile flavor compounds among three muscles-longissimus thoracis (LT), triceps brachii (TB), and semimembranosus (SM) of the Tianzhu white yak, and to elucidate the underlying regulatory mechanisms.Methods: A comprehensive approach was employed, integrating targeted metabolomics, untargeted metabolomics, flavoromics, real-time quantitative polymerase chain reaction, and histochemical staining to compare the biochemical characteristics of the three muscles.Results: The results of volatile profiles and sensory evaluation demonstrated that the TB muscle exhibited more favorable flavor-related traits. The TB muscle was enriched in key flavor precursors, including glutamic acid, glutamine, arginine, and total free amino acid content (p<0.05). Concurrently, the expression levels of key lipogenic genes (FASN, ELOVL4, SREBP1) were significantly higher in the TB muscle (p<0.05). Flavoromics analysis further revealed that the TB muscle exhibited greater diversity and higher relative abundance of key volatile compounds, such as aldehydes, ketones, and alcohols (p<0.05). Sensory evaluation further indicated that the TB muscle exhibited stronger sweet and fruity flavors. Untargeted metabolomics and pathway enrichment analysis indicated that this profile was associated with enrichment of arginine and proline metabolism and unsaturated fatty acid biosynthesis.Conclusion: This study demonstrates that flavor enhancement in yak meat is associated with the coordinated upregulation of lipid synthesis genes, thereby promoting the accumulation of flavor precursors. This process provides sufficient substrates for the Maillard reaction and lipid oxidation, facilitating the generation of volatile flavor compounds. These findings provide a theoretical basis for yak meat quality evaluation and precision processing.

(1) Background: Hair growth can function as an indicator of an animal’s health and nutritional status, furnishing a valuable means for early diagnosis and timely modifications to management practices, and is influenced by hormones, the immune system, and the levels of minerals within the animal’s body. (2) Methods: In this study, a total of 81 yaks were selected and divided into three groups according to their ages (1–2 years, 3–4 years, 5–6 years), and the concentrations of melatonin, dihydrotestosterone, IgA, IgG, and IgM in their blood serum and the levels of Ca, Mg, Zn, Fe, and P in both their blood serum and hair were detected. (3) Results: The levels of melatonin and dihydrotestosterone in yaks aged 1–2 years were significantly higher than those of other age groups (p < 0.001). In addition, the concentration of melatonin in male yaks was markedly greater than that in female yaks (p < 0.05). When it came to immunoglobulins, the IgA level in 1–2-year-old yaks was strikingly higher than those in yaks aged 3–4 years and 5–6 years (p < 0.05). In terms of mineral elements, the concentrations of calcium, magnesium, zinc, and iron in the blood serum of 1–2-year-old and 5–6-year-old yaks were significantly elevated compared to those in 3–4-year-old yaks. However, there was no notable difference between the 1–2-year-old and 5–6-year-old groups. The correlation analysis showed that there was a significant correlation between DHT and the levels of melatonin and IgA in yaks. Additionally, a significant correlation was observed between IgA and IgG, as well as between IgA and the levels of Fe, Mg, and Ca. It is likely that they jointly regulate the hair growth and immune processes of yaks. (4) Conclusions: There are positive correlations among melatonin, dihydrotestosterone, and IgA in the blood serum and the content of Fe and Mg in the hair to varying degrees, implying these indicators may jointly regulate yak hair growth and immune status. These research findings provide data support for applied research into evaluating the overall health status of yaks through the growth status of hair or by measuring the mineral content in hair in a non-invasive way.