Alterations in nutrient digestibility and performance of heat-stressed dairy cows by dietary L-theanine supplementation

The impact of rumen microbial composition on apparent digestibility, rumen fermentation and metabolism in Sanhe cows and Holstein cows of different parities under identical dietary conditions

Previous studies have discussed the association between serum metabolism and lactation performance among Sanhe and Holstein cows of different parities and found that the metabolic profiles of these two breeds vary differently with parity. Since the rumen is the central organ for nutrient absorption and production transformation in dairy cows, it remains unknown whether the differences observed under the same dietary conditions are related to the structure of the rumen microbiome. This study measured the apparent digestibility and rumen fermentation parameters of Sanhe cows (S1/S2/S3/S4) and Holstein cows (H1/H2/H3/H4) across four parities and generated a comprehensive rumen microbiome dataset using high-throughput sequencing technology. Significant differences in dry matter digestibility (p = 0.001) and ammonia nitrogen (p = 0.024) were observed among the S groups, with higher trends of various VFA contents in S1 (0.05 < p < 0.1). The H group showed significant differences in crude protein digestibility (p = 0.001), higher isovaleric acid content in H1 (p = 0.002), and the lowest acetate to propionate ratio (p = 0.002) in H3. Metagenomic sequencing results indicated consistency between rumen microbiome patterns and metabolic changes, with S1 distinctly different from S2/S3/S4, and H1 and H2 different from H3 and H4. The species composition of the rumen microbiome was similar between Sanhe and Holstein cows, but differences in abundance were noted. Rhizophagus , Neocallimastix, and Piromyces were more abundant in S1, H1, and H2, and pathways such as autophagy-animal, plant-pathogen interaction, and endocytosis were significantly enriched in these parities. Multiparous Sanhe cows had higher abundances of ATP-binding cassette transporters pathways. Additionally, CAZymes such as GH84 and GH37 were significantly associated with differential physiological indicators and milk traits. In conclusion, this study reveals the complex relationship between rumen microbiota and metabolic characteristics in Sanhe and Holstein cows of different parities, indicating that changes in the structure of the rumen microbiome may be key factors affecting lactation performance and metabolic differences in dairy cows.

High leucine bioavailability improves beef quality by altering serum metabolism in beef cattle

This study aimed to investigate the effect of dietary L-Leu supplementation on amino acid composition, serum metabolism, and meat quality characteristics in beef cattle. Twenty-four Angus cows of similar initial weight (575.5 ± 22.1 kg) were randomly assigned to two treatment groups with six replicate pens (two cattle per pen). The groups were fed a basal diet (CON) or a basal diet supplemented with 6.0 g/100 kg BW per day of L-Leu for 120 days pre-slaughter. Feeding L-Leu significantly increased average daily gain and decreased feed-to-weight-gain ratio (P < 0.05). L-Leu improved plasma free leucine bioavailability (P < 0.05), increased the concentrations of tyrosine and glutamine (P < 0.05), and decreased the concentrations of threonine and valine (P < 0.05). It also increased the content of total protein in plasma (P < 0.05). Supplementation with L-Leu tended to increase the marbling score (P = 0.06) and decrease subcutaneous fat thickness (P = 0.06), as well as the content of C10:0 (P < 0.05), C14:0 (P = 0.05), C20:0 (P < 0.05), and C18:2n-6 t (P = 0.07) in the longissimus thoracis muscle. However, L-Leu significantly increased the crude protein content in the longissimus thoracis muscle (P < 0.05). Correlation analysis revealed that L-Leu downregulated the relative abundance of metabolites associated with subcutaneous fat thickness and beef fatty acid synthesis (P < 0.01), and upregulated the relative abundance of metabolites associated with crude protein and ether extract in the longissimus thoracis muscle (P < 0.01). In conclusion, dietary L-Leu supplementation increases leucine bioavailability and improves meat quality in fattening beef cattle by altering host serum metabolism.

Dietary Capsaicin Supplementation Mitigates Calving-Induced Stress and Enhances Antioxidant Capacity, Immune Function, and Gut Microbiota in Periparturient Dairy Cows

This study investigated the effects of dietary capsaicin supplementation on antioxidant capacity, immune function, and gut microbiota in periparturient dairy cows. Twenty Holstein cows with an average parity of 2.5 ± 0.76, milk production of 31.30 ± 2.39 kg, and 36.10 ± 2.38 days to calving were randomly assigned to either a control group fed a basal diet or a treatment group supplemented with 1.2 g/head/day of capsaicin. The supplementation was administered during an evaluation period spanning from 28 days before delivery to 21 days after delivery using a randomized block experimental design. Results showed that capsaicin significantly reduced milk somatic cell count and pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) while enhancing serum antioxidant enzymes (SOD, GSH-Px, and CAT) and immunoglobulin levels (IgG, IgA, and IgM). Moreover, capsaicin altered gut microbiota composition, increasing the relative abundance of beneficial genera. These findings suggest that dietary capsaicin supplementation during the transition period improves lactation performance and supports immune function, as well as alleviates oxidative stress. This study highlights the potential of capsaicin as a practical dietary strategy for enhancing productivity in dairy farming.

Rumen-mammary gland axis and bacterial extracellular vesicles: Exploring a new perspective on heat stress in dairy cows

Heat stress poses a significant threat to the global livestock industry, particularly impacting dairy cows due to their higher metabolic heat production and increased susceptibility. The rumen microbiota plays a crucial role in regulating heat stress in dairy cows. Moreover, the rumen-mammary gland axis has been recently unveiled, indicating that rumen bacteria and their metabolites can influence mammary gland health and function. Extracellular vesicles, cell-derived vesicles, are known to carry various biomolecules and mediate intercellular communication and immune modulation. This review proposes the hypothesis that heat stress poses a threat to dairy cows via the rumen-mammary gland axis by regulating rumen microbiota and their secreted extracellular vesicles. It summarizes existing knowledge on bacterial extracellular vesicles and the rumen-mammary gland axis, suggesting that targeting the rumen microbiota and their extracellular vesicles, while enhancing mammary gland health through this axis, could be a promising strategy for preventing and alleviating heat stress in dairy cows. The aim of this review is to offer new insights and guide future research and development efforts concerning heat stress in dairy cows, thereby contributing to a deeper understanding of its pathogenesis and potential interventions.

Dietary saccharin sodium supplementation improves the production performance of dairy goats without residue in milk in summer

The purpose of this study was to investigate the effects of dietary saccharin sodium supplementation on production performance, serum biochemical indicators, and rumen fermentation of dairy goats in summer. Twelve Guanzhong dairy goats with similar body weight, days in milk, and milk yield were randomly divided into two dietary treatments: (1) CON: basal diet; (2) SS: basal diet + 150 mg/kg saccharin sodium on the basis of dry matter. The experiment lasted 35 d, including 7 d for adaptation and 28 d for dietary treatments, sampling and data collection. Each dairy goat was housed individually in a clean separate pen with ad libitum access to diet and water. The goats fed SS diet had increased dry matter intake (DMI; P = 0.037), 4% fat corrected milk yield (P = 0.049), energy corrected milk yield (P = 0.037), milk protein yield (P = 0.031), and total solids yield (P = 0.036). Serum activity of aspartate aminotransferase (P = 0.047) and concentrations of 70-kDa heat shock protein (P = 0.090), malondialdehyde (P = 0.092), and total protein (P = 0.057) were lower in goats fed SS diet than those fed CON diet. Supplementation of saccharin sodium tended to increase activity of glutathione peroxidase in serum (P = 0.079). The concentrations of rumen total volatile fatty acid (P = 0.042) and butyrate (P = 0.038) were increased by saccharin sodium supplementation. Dietary supplementation of saccharin sodium increased the relative abundance of Lachnobacterium (P = 0.022), Pseudoramibacter (P = 0.022), Shuttleworthia (P = 0.025), and Syntrophococcus (P = 0.037), but reduced the relative abundance of Prevotella_1 (P = 0.037) and Lachnospiraceae_UCG_008 (P = 0.037) in rumen. Saccharin sodium was observed in feces and urine of goats fed diet supplemented with saccharin sodium, but saccharin sodium was undetectable in the milk of goats receiving SS diet. In conclusion, administration of saccharin sodium was effective in increasing fat and energy corrected milk yield by increasing DMI and improving rumen fermentation and antioxidant capacity of dairy goats in summer. In addition, saccharin sodium residue was undetectable in the milk.

Effect of heat stress on blood biochemistry and energy metabolite of the Dazu black goats

The objective of this study was to determine the effects of heat stress (HS) on physiological, blood biochemical, and energy metabolism in Dazu black goats. Six wether adult Dazu black goats were subjected to 3 experimental periods: high HS (group H, temperature-humidity index [THI] > 88) for 15 d, moderate HS (group M, THI was 79-88) for 15 d, and no HS (group L, THI < 72) for 15 d. Rectal temperature (RT) and respiratory rate (RR) were determined on d 7 and 15 of each period, and blood samples were collected on d 15 of each period. All goats received glucose (GLU) tolerance test (GTT) and insulin (INS) tolerance test on d 7 and d 10 of each period. The results showed that HS decreased dry matter intake (DMI) and INS concentration (p < 0.05), and increased RT, RR, non-esterified fatty acid (NEFA), cortisol (COR), and total protein (TP) concentrations (p < 0.05). Compared to group L, the urea nitrogen (BUN) concentration increased and GLU concentration decreased in group H (p < 0.05). During the GTT, the area under the curve (AUC) of GLU concentrations increased by 12.26% (p > 0.05) and 40.78% (p < 0.05), and AUC of INS concentrations decreased by 26.04 and 14.41% (p < 0.05) in groups H and M compared to group L, respectively. The INS concentrations were not significant among the three groups (p > 0.05) during the ITT. A total of 60 differentially expressed metabolites were identified in response to groups H and M. In HS, changes in metabolites related to carbohydrate metabolism and glycolysis were identified (p < 0.05). The metabolites related to fatty acid β-oxidation accumulated, glycogenic and ketogenic amino acids were significantly increased, while glycerophospholipid metabolites were decreased in HS (p < 0.05). HS significantly increased 1-methylhistidine, creatinine, betaine, taurine, taurolithocholic acid, inosine, and hypoxanthine, while decreasing vitamin E in blood metabolites (p < 0.05). In summary, HS changed the metabolism of fat, protein, and energy, impaired GLU tolerance, and mainly increased amino acid metabolism to provide energy in Dazu black goats.

The protective effect of L-theanine on the intestinal barrier in heat-stressed organisms

Heat stress caused by heatwaves, extreme temperatures, and other weather can damage the intestinal barrier of organisms. L-Theanine (LTA) attenuates heat stress-induced oxidative stress, inflammatory responses, and impaired immune function, but its protective effect on the intestinal barrier of heat-stressed organisms is unclear. In this study, low (100 mg kg-1 d-1), medium (200 mg kg-1 d-1), and high (400 mg kg-1 d-1) dosages of LTA were used in the gavage of C57BL/6J male mice that were experimented on for 50 d. These mice were subjected to heat stress for 2 h d-1 at 40 ± 1 °C and 60 ± 5% RH in the last 7 d. LTA attenuated the heat stress-induced decreases in body mass and feed intake, and the destruction of intestinal villi and crypt depth; reduced the serum levels of FITC-dextran and D-LA, as well as the DAO activity; and upregulated the colonic tissues of Occludin, Claudin-1, and ZO-1 mRNA and occludin protein expression. The number of goblet cells in the colon tissue of heat-stressed organisms increased in the presence of LTA, and the expression levels of Muc2, Muc4 mRNA, and Muc2 protein were upregulated. LTA increased the abundance of Bifidobacterium and Turicibacter, and decreased the abundance of Enterorhabdus and Desulfovibrio in the intestinal tract of heat-stressed organisms and restored gut microbiota homeostasis. LTA promoted the secretion of IL-4, IL-10, and sIgA and inhibited the secretion of TNF-α and IFN-γ in the colon of heat-stressed organisms. The expressions of Hsf1, Hsp70, Hsph1, TLR4, P38 MAPK, p-P65 NF-κB, MLCK mRNA, and proteins were downregulated by LTA in the colon of heat-stressed organisms. These results suggest that LTA protects the intestinal barrier in heat-stressed organisms by modulating multiple molecular pathways. Therefore, this study provides evidence on how tea-containing LTA treatments could be used to prevent and relieve intestinal problems related to heat stress.

Metabolic Changes in Serum and Milk of Holstein Cows in Their First to Fourth Parity Revealed by Biochemical Analysis and Untargeted Metabolomics

The performance of dairy cows is closely tied to the metabolic state, and this performance varies depending on the number of times the cows have given birth. However, there is still a lack of research on the relationship between the metabolic state of Holstein cows and the performance of lactation across multiple parities. In this study, biochemical analyses and metabolomics studies were performed on the serum and milk from Holstein cows of parities 1-4 (H1, N = 10; H2, N = 7; H3, N = 9; H4, N = 9) in mid-lactation (DIM of 141 ± 4 days) to investigate the link between performance and metabolic changes. The results of the milk quality analysis showed that the lactose levels were highest in H1 (p = 0.036). The total protein content in the serum increased with increasing parity (p = 0.013). Additionally, the lipase activity was found to be lowest in H1 (p = 0.022). There was no difference in the composition of the hydrolyzed amino acids in the milk among H1 to H4. However, the free amino acids histidine and glutamate in the serum were lowest in H1 and highest in H3 (p < 0.001), while glycine was higher in H4 (p = 0.031). The metabolomics analysis revealed that 53 and 118 differential metabolites were identified in the milk and serum, respectively. The differential metabolites in the cows' milk were classified into seven categories based on KEGG. Most of the differential metabolites in the cows' milk were found to be more abundant in H1, and these metabolites were enriched in two impact pathways. The differential metabolites in the serum could be classified into nine categories and enriched in six metabolic pathways. A total of six shared metabolites were identified in the serum and milk, among which cholesterol and citric acid were closely related to amino acid metabolism in the serum. These findings indicate a significant influence of blood metabolites on the energy and amino acid metabolism during the milk production process in the Holstein cows across 1-4 lactations, and that an in-depth understanding of the metabolic changes that occur in Holstein cows during different lactations is essential for precision farming, and that it is worthwhile to further investigate these key metabolites that have an impact through controlled experiments.

Effect of Slow-Release Urea Partial Replacement of Soybean Meal on Lactation Performance, Heat Shock Signal Molecules, and Rumen Fermentation in Heat-Stressed Mid-Lactation Dairy Cows

This study aimed to assess the effects of partially substituting soybean meal in the diet with slow-release urea (SRU) on the lactation performance, heat shock signal molecules, and environmental sustainability of heat-stressed lactating cows in the middle stage of lactation. In this study, 30 healthy Holstein lactating dairy cattle with a similar milk yield of 22.8 ± 3.3 kg, days in milk of 191.14 ± 27.24 days, and 2.2 ± 1.5 parity were selected and randomly allocated into two groups. The constituents of the two treatments were (1) basic diet plus 500 g soybean meal (SM) for the SM group and (2) basic diet plus 100 g slow-release urea and 400 g corn silage for the SRU group. The average temperature humidity index (THI) during the experiment was 84.47, with an average THI of >78 from day 1 to day 28, indicating the cow experienced moderate heat stress conditions. Compared with the SM group, the SRU group showed decreasing body temperature and respiratory rate trends at 20:00 (p < 0.1). The substitution of SM with SRU resulted in an increasing trend in milk yield, with a significant increase of 7.36% compared to the SM group (p < 0.1). Compared to the SM group, AST, ALT, and γ-GT content levels were significantly increased (p < 0.05). Notably, the levels of HSP-70 and HSP-90α were significantly reduced (p < 0.05). The SRU group showed significantly increased acetate and isovalerate concentrations compared with the SM group (p < 0.05). The prediction results indicate that the SRU group exhibits a significant decrease in methane (CH4) emissions when producing 1 L of milk compared to the SM group (p < 0.05). In summary, dietary supplementation with SRU tended to increase the milk yield and rumen fermentation and reduce plasma heat shock molecules in mid-lactation, heat-stressed dairy cows. In the hot summer, using SRU instead of some soybean meal in the diet alleviates the heat stress of dairy cows and reduces the production of CH4.

L-Theanine and Immunity: A Review

L-theanine (N-ethyl-γ-glutamine) is the main amino acid in tea leaves. It not only contributes to tea flavor but also possesses several health benefits. Compared with its sedative and calming activities, the immunomodulatory effects of L-theanine have received less attention. Clinical and epidemiological studies have shown that L-theanine reduces immunosuppression caused by strenuous exercise and prevents colds and influenza by improving immunity. Numerous cell and animal studies have proven that theanine plays an immunoregulatory role in inflammation, nerve damage, the intestinal tract, and tumors by regulating γδT lymphocyte function, glutathione (GSH) synthesis, and the secretion of cytokines and neurotransmitters. In addition, theanine can be used as an immunomodulator in animal production. This article reviews the research progress of L-theanine on immunoregulation and related mechanisms, as well as its application in poultry and animal husbandry. It is hoped that this work will be beneficial to future related research.