Review: Lipid biology in the periparturient dairy cow: contemporary perspectives

Changes in adiponectin levels of subclinical ketosis cows and their effects on steroid hormone secretion and proliferation in follicular granulosa cells

In dairy cows, the occurrence of subclinical ketosis (SCK) is particularly high during early lactation. Previously, we documented alterations in the abundance of adiponectin (ADPN) in anestrus cows with SCK in comparison to cows in estrus. In the present study, 60 cows were divided into two groups: control (C, n = 30) and SCK (n = 30). Based on cow's estrus situation in two group at 55-60 days postpartum, 15 anestrus SCK cows and estrus cows were designated the SCK-A group and C-E group, respectively. The SCK-A group had downregulated serum and follicular fluid ADPN levels compared with the C-E group. The serum ADPN level was positively correlated with the insulin level and follicle growth rate, and there was a positive correlation between ADPN and glucose in the follicular fluid. Primary culture of dairy cow granulosa cells (GCs) was established to observe the effect of low glucose (Glu) and/or ADPN on GCs cyclins and proteins important for steroid synthesis. The results showed that the addition of 1 µg/mL ADPN alleviated the negative effects of low Glu treatment on the proliferation of GCs and the expression of steroid secretion related protein proteins. Treatment with LY294002 (PI3K inhibitor) four experimental GCs groups: control (0 µg/mL ADPN), 1 µg/mL ADPN, LY294002 inhibitor, and 1 µg/mL ADPN+LY294002. The results showed that ADPN promotes the secretion of steroid hormones by GCs through the PI3K-AKT. In summary, ADPN plays a crucial role in ameliorating postpartum anestrus in dairy cows with SCK.

Rumen microbiota succession throughout the perinatal period and its association with postpartum production traits in dairy cows: A review

The transition period for dairy cows usually refers to the 3 weeks pre-calving to the 3 weeks post-calving. During this period, dairy cows undergo metabolic and physiological adaptations because of their susceptibility to metabolic and infectious diseases. Poor feeding management under these circumstances may adversely affect the health and subsequent production performance of the cows. Owing to long-term adaptation and evolution, the rumen has become a unique ecosystem inhabited by a complex microbial community closely associated with its natural host. Dietary components are metabolized by the rumen microbiota, and volatile fatty acids and microbial protein products can be used as precursor substances for synthesizing meat and milk components. The successful transition of perinatal dairy cows includes changes in diet, physiology, and the rumen microbiota. Rumen microbial profiles have been confirmed to be heritable and repairable; however, adverse circumstances affect rumen microbial composition, host digestion and metabolism, as well as postpartum production traits of dairy cows for a certain period. Preliminary evidence indicates a close relationship between the rumen microbiota and animal performance. Therefore, changes in rumen microbes during the transition period and the intrinsic links between the microbiota and host postpartum phenotypic traits need to be better understood to optimize production performance in ruminants.

Role of diacylglycerol O-acyltransferase 1 (DGAT1) in lipolysis and autophagy of adipose tissue from ketotic dairy cows

High-yielding dairy cows in early lactation often encounter difficulties in meeting the energy requirements essential for maintaining milk production. This is primarily attributed to insufficient dry matter intake, which consequently leads to sustained lipolysis of adipose tissue. Fatty acids released by lipolysis can disrupt metabolic homeostasis. Autophagy, an adaptive response to intracellular environmental changes, is considered a crucial mechanism for regulating lipid metabolism and maintaining a proper cellular energy status. Despite its close relationship with aberrant lipid metabolism and cytolipotoxicity in animal models of metabolic disorders, the precise function of diacylglycerol o-acyltransferase 1 (DGAT1) in bovine adipose tissue during periods of negative energy balance is not fully understood, particularly regarding its involvement in lipolysis and autophagy. The objective of the present study was to assess the effect of DGAT1 on both lipolysis and autophagy in bovine adipose tissue and isolated adipocytes. Adipose tissue and blood samples were collected from cows diagnosed as clinically ketotic (n = 15) or healthy (n = 15) following a veterinary evaluation based on clinical symptoms and serum concentrations of BHB, which were 3.19 mM (interquartile range = 0.20) and 0.50 mM (interquartile range = 0.06), respectively. Protein abundance of DGAT1 and phosphorylation levels of unc-51-like kinase 1 (ULK1), were greater in adipose tissue from cows with ketosis, whereas phosphorylation levels of phosphoinositide 3-kinase (PI3K), protein kinase B (AKT), and mammalian target of rapamycin (mTOR) were lower. Furthermore, when adipocytes isolated from the harvested adipose tissue of 15 healthy cows were transfected with DGAT1 overexpression adenovirus or DGAT1 small interfering RNA followed by exposure to epinephrine (EPI), it led to greater ratios and protein abundance of phosphorylated hormone-sensitive triglyceride lipase (LIPE) to total LIPE and adipose triglyceride lipase (ATGL), while inhibiting the protein phosphorylation levels of ULK1, PI3K, AKT, and mTOR. Overexpression of DGAT1 in EPI-treated adipocytes reduced lipolysis and autophagy, whereas silencing DGAT1 further exacerbated EPI-induced lipolysis and autophagy. Taken together, these findings indicate that upregulation of DGAT1 may function as an adaptive response to suppress adipocytes lipolysis, highlighting the significance of maintaining metabolic homeostasis in dairy cows during periods of negative energy balance.

Diacylglycerol O-acyltransferase (DGAT) isoforms play a role in peridroplet mitochondrial fatty acid metabolism in bovine liver

Hepatocellular lipid accumulation characterizes fatty liver in dairy cows. Lipid droplets (LD), specialized organelles that store lipids and maintain cellular lipid homeostasis, are responsible for the ectopic storage of lipids associated with several metabolic disorders. In recent years, non-ruminant studies have reported that LD-mitochondria interactions play an important role in lipid metabolism. Due to the role of diacylglycerol acyltransferase isoforms (DGAT1 and DGAT2) in LD synthesis, we explored mechanisms of mitochondrial fatty acid transport in ketotic cows using liver biopsies and isolated primary hepatocytes. Compared with healthy cows, cows with fatty liver had massive accumulation of LD and high protein expression of the triglyceride (TAG) synthesis-related enzymes DGAT1 and DGAT2, LD synthesis-related proteins perilipin 2 (PLIN2) and perilipin 5 (PLIN5), and the mitochondrial fragmentation-related proteins dynamin-related protein 1 (DRP1) and fission 1 (FIS1). In contrast, factors associated with fatty acid oxidation, mitochondrial fusion and mitochondrial electron transport chain complex were lower compared with those in the healthy cows. In addition, transmission electron microscopy revealed significant contacts between LD-mitochondria in liver tissue from cows with fatty liver. Compared with isolated cytoplasmic mitochondria, expression of carnitine palmitoyl transferase 1A (CPT1A) and DRP1 was lower, but mitofusin 2 (MFN2) and mitochondrial electron transport chain complex was greater in isolated peridroplet mitochondria from hepatic tissue of cows with fatty liver. In vitro data indicated that exogenous free fatty acids (FFA) induced hepatocyte LD synthesis and mitochondrial dynamics consistent with in vivo results. Furthermore, DGAT2 inhibitor treatment attenuated the FFA-induced upregulation of PLIN2 and PLIN5 and rescued the impairment of mitochondrial dynamics. Inhibition of DGAT2 also restored mitochondrial membrane potential and reduced hepatocyte reactive oxygen species production. The present in vivo and in vitro results indicated there are functional differences among different types of mitochondria in the liver tissue of dairy cows with ketosis. Activity of DGAT2 may play a key role in maintaining liver mitochondrial function and lipid homeostasis in dairy cows during the transition period.

Dietary Supplementation with Naringin Improves Systemic Metabolic Status and Alleviates Oxidative Stress in Transition Cows via Modulating Adipose Tissue Function: A Lipid Perspective

Dairy cows face metabolic challenges around the time of calving, leading to a negative energy balance and various postpartum health issues. Adipose tissue is crucial for cows during this period, as it regulates energy metabolism and supports immune function. Naringin, one of the main flavonoids in citrus fruit and their byproducts, is a potent antioxidant and anti-inflammatory phytoconstituent. The study aimed to evaluate the effects of supplemental naringin on performance, systemic inflammation, oxidative status, and adipose tissue metabolic status. A total of 36 multiparous Holstein cows (from ~21 d prepartum through 35 d postpartum) were provided a basal control (CON) diet or a CON diet containing naringin (NAR) at 30 g/d per cow. Supplemental NAR increased the yield of raw milk and milk protein, without affecting dry matter intake. Cows fed NAR showed significantly lower levels (p < 0.05) of serum non-esterified fatty acid (NEFA), C-reactive protein, IL-1β, IL-6, malonaldehyde, lipopolysaccharide (LPS), aspartate aminotransferase, and alanine aminotransferase, but increased (p < 0.05) glutathione peroxidase activity relative to those fed CON. Supplemental NAR increased (p < 0.05) adipose tissue adiponectin abundance, decreased inflammatory responses, and reduced oxidative stress. Lipidomic analysis showed that cows fed NAR had lower concentrations of ceramide species (p < 0.05) in the serum and adipose tissue than did the CON-fed cows. Adipose tissue proteomics showed that proteins related to lipolysis, ceramide biosynthesis, inflammation, and heat stress were downregulated (p < 0.05), while those related to glycerophospholipid biosynthesis and the extracellular matrix were upregulated (p < 0.05). Feeding NAR to cows may reduce the accumulation of ceramide by lowering serum levels of NEFA and LPS and increasing adiponectin expression, thereby decreasing inflammation and oxidative stress in adipose tissue, ultimately improving their systemic metabolic status. Including NAR in periparturient cows' diets improves lactational performance, reduces excessive lipolysis in adipose tissue, and decreases systemic and adipose tissue inflammation and oxidative stress. Integrating lipidomic and proteomic data revealed that reduced ceramide and increased glycerophospholipids may alleviate metabolic dysregulations in adipose tissue, which in turn benefits systemic metabolic status.

Repeated inoculation with rumen fluid accelerates the rumen bacterial transition with no benefit on production performance in postpartum Holstein dairy cows

BACKGROUND

The dairy cow's postpartum period is characterized by dramatic physiological changes, therefore imposing severe challenges on the animal for maintaining health and milk output. The dynamics of the ruminal microbiota are also tremendous and may play a crucial role in lactation launch. We aim to investigate the potential benefits of early microbial intervention by fresh rumen microbiota transplantation (RMT) and sterile RMT in postpartum dairy cows. Twelve fistulated peak-lactation dairy cows were selected to be the donors for rumen fluid collection. Thirty postpartum cows were divided into 3 groups as the transplantation receptors respectively receiving 10 L fresh rumen fluid (FR), 10 L sterile rumen fluid (SR), or 10 L saline (CON) during 3 d after calving.

RESULTS

Production performance, plasma indices, plasma lipidome, ruminal microbiome, and liver transcriptome were recorded. After fresh and sterile RMT, we found that the molar proportion of propionic acid was increased on d 7 in the FR and SR groups and the bacterial composition was also significantly changed when compared with the CON group. A similarity analysis showed that the similarities between the CON group and FR or SR group on d 7 were 48.40% or 47.85%, whereas the similarities between microbiota on d 7 and 21 in the FR and SR groups were 68.34% or 66.85%. Dry matter intake and feed efficiency were not affected by treatments. Plasma β-hydroxybutyrate concentration in the FR group was decreased and significantly different lipids mainly included phosphatidylcholine and lysophosphatidylcholine containing polyunsaturated fatty acids. Hepatic transcriptomics analysis indicated acute-phase response pathways were upregulated in the SR group.

CONCLUSIONS

Our study suggests that RMT can shorten the transition process of the ruminal microbiota of postpartum dairy cows with no benefit on dry matter intake or feed efficiency. Inoculation with rumen fluid may not be a useful approach to promote the recovery of postpartum dairy cows.

Inhibition of cluster antigen 36 protects against fatty acid-induced lipid accumulation, oxidative stress, and inflammation in bovine hepatocytes

When ketosis occurs, supraphysiological concentrations of nonesterified fatty acids (NEFA) display lipotoxicity and are closely related to the occurrence of hepatic lipid accumulation, oxidative stress, and inflammation, resulting in hepatic damage and exacerbating the progression of ketosis. However, the mechanism of these lipotoxic effects caused by high concentrations of NEFA in ketosis is still unclear. Cluster antigen 36 (CD36), a fatty acid transporter, plays a vital role in the development of hepatic pathological injury in nonruminants. Thus, the aim of this study was to investigate whether CD36 plays a role in NEFA-induced hepatic lipotoxicity in dairy cows with clinical ketosis. Liver tissue and blood samples were collected from healthy (n = 10) and clinically ketotic (n = 10) cows at 3 to 15 d in milk. In addition, hepatocytes isolated from healthy calves were treated with 0, 0.6, 1.2, or 2.4 mM NEFA for 12 h; or infected with CD36 expressing adenovirus or CD36 silencing small interfering RNA for 48 h and then treated with 1.2 mM NEFA for 12 h. Compared with healthy cows, clinically ketotic cows had greater concentrations of serum NEFA and β-hydroxybutyrate and activities of aspartate aminotransferase and alanine aminotransferase but lower serum glucose. In addition, dairy cows with clinical ketosis displayed excessive hepatic lipid accumulation. More importantly, these alterations were accompanied by an increased abundance of hepatic CD36. In the cell culture model, exogenous NEFA (0, 0.6, 1.2, or 2.4 mM) treatment could dose-dependently increase the abundance of CD36. Meanwhile, NEFA (1.2 mM) increased the content of triacylglycerol, reactive oxygen species and malondialdehyde, and decreased the activities of glutathione peroxidase and superoxide dismutase. Moreover, NEFA upregulated phosphorylation levels of nuclear factor κB (NF-κB) and the inhibitor of NF-κB (IκB) α, along with the upregulation of protein abundance of NLR family pyrin domain containing 3 (NLRP3) and caspase-1, and mRNA abundance of IL1B, IL6, and tumor necrosis factor α (TNFA). These alterations induced by NEFA in bovine hepatocytes were associated with increased lipid accumulation, oxidative stress and inflammation, which could be further aggravated by CD36 overexpression. Conversely, silencing CD36 attenuated these NEFA-induced detriments. Overall, these data suggest that CD36 may be a potential therapeutic target for NEFA-induced hepatic lipid accumulation, oxidative stress, and inflammation in dairy cows.

N-3 Polyunsaturated Fatty Acids as a Nutritional Support of the Reproductive and Immune System of Cattle-A Review

This paper focuses on the role of n-3 fatty acids as a nutrient crucial to the proper functioning of reproductive and immune systems in cattle. Emphasis was placed on the connection between maternal and offspring immunity. The summarized results confirm the importance and beneficial effect of n-3 family fatty acids on ruminant organisms. Meanwhile, dietary n-3 fatty acids supplementation, especially during the critical first week for dairy cows experiencing their peripartum period, in general, is expected to enhance reproductive performance, and the impact of its supplementation appears to be dependent on body condition scores of cows during the drying period, the severity of the negative energy balance, and the amount of fat in the basic feed ration. An unbalanced, insufficient, or excessive fatty acid supplementation of cows' diets in the early stages of pregnancy (during fetus development) may affect both the metabolic and nutritional programming of the offspring. The presence of the polyunsaturated fatty acids of the n-3 family in the calves' ration affects not only the performance of calves but also the immune response, antioxidant status, and overall metabolism of the future adult cow.

White Adipose Tissue Heterogeneity in the Single-Cell Era: From Mice and Humans to Cattle

Adipose tissue is a major modulator of metabolic function by regulating energy storage and by acting as an endocrine organ through the secretion of adipokines. With the advantage of next-generation sequencing-based single-cell technologies, adipose tissue has been studied at single-cell resolution, thus providing unbiased insight into its molecular composition. Recent single-cell RNA sequencing studies in human and mouse models have dissected the transcriptional cellular heterogeneity of subcutaneous (SAT), visceral (VAT), and intramuscular (IMAT) white adipose tissue depots and revealed unique populations of adipose tissue progenitor cells, mature adipocytes, immune cell, vascular cells, and mesothelial cells that play direct roles on adipose tissue function and the development of metabolic disorders. In livestock species, especially in bovine, significant gaps of knowledge remain in elucidating the roles of adipose tissue cell types and depots on driving the pathogenesis of metabolic disorders and the distinct fat deposition in VAT, SAT, and IMAT in meat animals. This review summarizes the current knowledge on the transcriptional and functional cellular diversity of white adipose tissue revealed by single-cell approaches and highlights the depot-specific function of adipose tissue in different mammalian species, with a particular focus on recent findings and future implications in cattle.

Metabolic Changes Associated with Different Levels of Energy Deficits in Mediterranean Buffaloes during the Early Lactation Stage: Type and Role of the Main Lipid Fractions Involved

Cell function and energy redistribution are influenced by lipid classes (phospholipids (PLs), free fatty acids (FFAs), triglycerides (TGs), and cholesterol esters (CEs)). The aim of this study was to investigate metabolic alterations that are related to changes in lipid classes according to different levels of energy deficits in early lactating Mediterranean buffaloes (MBs). Sixty-three MBs were enrolled at the beginning of lactation using an observational study with a cross-sectional experimental design. Serum β-hydroxybutyrate (BHB) levels were used to group the animals into a healthy group (Group H; n = 38; BHB < 0.70 mmol/L) and hyperketonemia risk group (Group K; n = 25; BHB ≥ 0.70 mmol/L). Statistical analysis was performed using a linear model that included the effect of the group and body condition score to assess differences in fatty acid (FA) concentrations. A total of 40 plasma FAs were assessed in each lipid class. Among the FAs, eight PLs, seven FFAs, four TGs, and four CEs increased according to BHB levels, while three FFAs, three TGs, and one CE decreased. The changes among lipid class profiles suggested the influence of inflammatory response, liver metabolism, and the state of body lipid reserves. In addition, the possible similarities of buffaloes at risk of hyperketonemia with ketotic cows suggest the necessity of further investigations in these ruminants.

Biofortification of cow milk through dietary supplementation with sunflower oil: fatty acid profile, atherogenicity, and thrombogenic index

The present study aimed to assess the effects of replacing the starchy ingredients of concentrate by increasing the levels of sunflower oil on the production, composition, fatty acid profile, and evaluate the atherogenicity and thrombogenic index of Jersey cow's milk. Eight Jersey cows were arranged in a double Latin square and distributed in treatments consisting of supplementation with increasing levels of sunflower oil replacing the corn grain and wheat bran of concentrate, including the following: T0 (control diet), without sunflower oil and with 38 g ether extract (EE)/kg dry matter (DM); T1 = 65 g EE/kg DM; T2 = 86 g EE/kg DM; and T3 = 110 g EE/kg DM. The daily milk production was measured, and the corrected milk production was calculated. Milk samples were analyzed by infrared spectroscopy to determine fat, protein, lactose, and total solids, whereas the lipid profile was assessed by gas chromatography. Milk production, energy-corrected milk production, fat content, daily fat production, lactose, and total solids were not affected by the treatments. Protein, lactose, and total solids concentrations decreased. Short-, medium-, and odd-chain fatty acids decreased with an increase in sunflower oil levels. Conversely, linear increases in long-chain, monounsaturated, and polyunsaturated fatty acid concentrations were observed. There were significant increases in stearic and elaidic acids and conjugated linoleic acid isomers, especially in vaccenic and rumenic acids. There was a positive effect on the milk atherogenicity, thrombogenicity, and nutraceutical indices. Dietary supplementation with sunflower oil changes the milk FA profile, decreases the atherogenicity and the thrombogenicity indices, and improve the nutraceutical index up to the addition of 86 g EE/kg DM de sunflower oil in the diets of Jersey cows.

Hepatic Global Transcriptomic Profiles of Holstein Cows According to Parity Reveal Age-Related Changes in Early Lactation

Cows can live for over 20 years, but their productive lifespan averages only around 3 years after first calving. Liver dysfunction can reduce lifespan by increasing the risk of metabolic and infectious disease. This study investigated the changes in hepatic global transcriptomic profiles in early lactation Holstein cows in different lactations. Cows from five herds were grouped as primiparous (lactation number 1, PP, 534.7 ± 6.9 kg, n = 41), or multiparous with lactation numbers 2-3 (MP2-3, 634.5 ± 7.5 kg, n = 87) or 4-7 (MP4-7, 686.6 ± 11.4 kg, n = 40). Liver biopsies were collected at around 14 days after calving for RNA sequencing. Blood metabolites and milk yields were measured, and energy balance was calculated. There were extensive differences in hepatic gene expression between MP and PP cows, with 568 differentially expressed genes (DEGs) between MP2-3 and PP cows, and 719 DEGs between MP4-7 and PP cows, with downregulated DEGs predominating in MP cows. The differences between the two age groups of MP cows were moderate (82 DEGs). The gene expression differences suggested that MP cows had reduced immune functions compared with the PP cows. MP cows had increased gluconeogenesis but also evidence of impaired liver functionality. The MP cows had dysregulated protein synthesis and glycerophospholipid metabolism, and impaired genome and RNA stability and nutrient transport (22 differentially expressed solute carrier transporters). The genes associated with cell cycle arrest, apoptosis, and the production of antimicrobial peptides were upregulated. More surprisingly, evidence of hepatic inflammation leading to fibrosis was present in the primiparous cows as they started their first lactation. This study has therefore shown that the ageing process in the livers of dairy cows is accelerated by successive lactations and increasing milk yields. This was associated with evidence of metabolic and immune disorders together with hepatic dysfunction. These problems are likely to increase involuntary culling, thus reducing the average longevity in dairy herds.

Gene co-expression network and differential expression analyses of subcutaneous white adipose tissue reveal novel insights into the pathological mechanisms underlying ketosis in dairy cows

Ketosis is a common nutritional metabolic disease during the perinatal period in dairy cows. Although various risk factors have been identified, the molecular mechanism underlying ketosis remains elusive. In this study, subcutaneous white adipose tissue (sWAT) was biopsied for transcriptome sequencing on 10 Holstein cows with type II ketosis [blood β-hydroxybutyric acid (BHB) >1.4 mmol/L; Ket group] and another 10 cows without type II ketosis (BHB ≤1.4 mmol/L; Nket group) at d 10 after calving. Serum concentrations of nonesterified fatty acids (NEFA) and BHB, as indicators of excessive fat mobilization and circulating ketone bodies, respectively, were significantly higher in the Ket group than in the Nket group. Aspartate transaminase (AST) and total bilirubin (TBIL), as indicators of liver damage, were higher in the Ket group than in the Nket group. Weighted gene co-expression network analysis (WGCNA) of the sWAT transcriptome revealed modules significantly correlated with serum BHB, NEFA, AST, TBIL, and total cholesterol. The genes in these modules were enriched in the regulation of the lipid biosynthesis process. Neurotrophic tyrosine kinase receptor type 2 (NTRK2) was identified as the key hub gene by intramodular connectivity, gene significance, and module membership. Quantitative reverse transcription PCR analyses for these samples, as well as a set of independent samples, validated the downregulation of NTRK2 expression in the sWAT of dairy cows with type II ketosis. NTRK2 encodes tyrosine protein kinase receptor B (TrkB), which is a high-affinity receptor for brain-derived neurotrophic factor, suggesting that abnormal lipid mobilization in cows with type II ketosis might be associated with impaired central nervous system regulation of adipose tissue metabolism, providing a novel insight into the pathogenesis underlying type II ketosis in dairy cows.

Effects of perinatal stress on the metabolites and lipids in plasma of dairy goats

Dairy goats experience metabolic stress during the peripartal period, and their ability to navigate this stage of lactation is related to the occurrence and development of metabolic diseases. Unlike dairy cows, there is a lack of comprehensive analysis of changes in the plasma profiles of peripartal dairy goats, particularly using high-throughput techniques. A subset of 9 clinically-healthy dairy goats were used from a cohort of 96 primiparous Guanzhong dairy goats (BCS, 2.75 ± 0.15). Blood samples were collected at seven time points around parturition (d 21, 14, 7 before parturition, the day of kidding, and d 7, 14, 21 postpartum), were analyzed using untargeted metabolomics and targeted lipidomics. The orthogonal partial least squares discriminant analysis model revealed a total of 31 differential metabolites including p-cresol sulfate, pyruvic acid, cholic acid, and oxoglutaric acid. The pathway enrichment analysis identified phenylalanine metabolism, aminoacyl-tRNA biosynthesis, and citrate cycle as the top three significantly-altered pathways. The Limma package identified a total of 123 differentially expressed lipids. Phosphatidylserine (PS), free fatty acids (FFA), and acylcarnitines (ACs) were significantly increased on the day of kidding, while diacylglycerols (DAG) and triacylglycerols (TAG) decreased. Ceramides (Cer) and lyso-phosphatidylinositols (LPI) were significantly increased during postpartum period, while PS, FFA, and ACs decreased postpartum and gradually returned to antepartum levels. Individual species of FFA and phosphatidylcholines (PC) were segregated based on the differences in the saturation and length of the carbon chain. Overall, this work generated the largest repository of the plasma lipidome and metabolome in dairy goats across the peripartal period, which contributed to our understanding of the multifaceted adaptations of transition dairy goats.

The Effect of the Feeding System on Fat Deposition in Yak Subcutaneous Fat

Fat deposition is very important to the growth and reproduction of yaks. In this study, the effect of the feeding system on fat deposition in yaks was explored by transcriptomics and lipidomics. The thickness of the subcutaneous fat in yaks under stall (SF) and graze feeding (GF) was evaluated. The transcriptomes and lipidomes of the subcutaneous fat in yaks under different feeding systems were detected by RNA-sequencing (RNA-Seq) and non-targeted lipidomics based on ultrahigh-phase liquid chromatography tandem mass spectrometry (UHPLC-MS), respectively. The differences in lipid metabolism were explored, and the function of differentially expressed genes (DEGs) was evaluated by gene ontology (GO) and Kyoto encyclopedia of genes and genome (KEGG) analysis. Compared with GF yaks, SF yaks possessed stronger fat deposition capacity. The abundance of 12 triglycerides (TGs), 3 phosphatidylethanolamines (PEs), 3 diglycerides (DGs), 2 sphingomyelins (SMs) and 1 phosphatidylcholine (PC) in the subcutaneous fat of SF and GF yaks was significantly different. Under the mediation of the cGMP-PKG signaling pathway, the blood volume of SF and GF yaks may be different, which resulted in the different concentrations of precursors for fat deposition, including non-esterified fatty acid (NEFA), glucose (GLU), TG and cholesterol (CH). The metabolism of C16:0, C16:1, C17:0, C18:0, C18:1, C18:2 and C18:3 in yak subcutaneous fat was mainly realized under the regulation of the INSIG1, ACACA, FASN, ELOVL6 and SCD genes, and TG synthesis was regulated by the AGPAT2 and DGAT2 genes. This study will provide a theoretical basis for yak genetic breeding and healthy feeding.

Untargeted metabolomics and lipidomics to assess plasma metabolite changes in dairy goats with subclinical hyperketonemia

Subclinical hyperketonemia (SCHK) is the major metabolic disease observed during the transition period in dairy goats, and is characterized by high plasma levels of nonesterified fatty acids (NEFA) and β-hydroxybutyrate (BHB). However, no prior study has comprehensively assessed metabolomic profiles of dairy goats with SCHK. Plasma samples were collected within 1 h after kidding from SCHK goats (BHB concentration >0.8 mM, n = 7) and clinically healthy goats (BHB concentration <0.8 mM, n = 7) with similar body condition score (2.75 ± 0.15, mean ± standard error of the mean) and parity (primiparous). A combination of targeted and untargeted mass spectrometric approaches was employed for analyzing the various changes in the plasma lipidome and metabolome. Statistical analyses were performed using the GraphPad Prism 8.0, SIMCA-P software (version 14.1), and R packages (version 4.1.3). Plasma aminotransferase, nonesterified fatty acids, and BHB concentrations were greater in the SCHK group, but plasma glucose concentrations were lower. A total of 156 metabolites and 466 lipids were identified. The analysis of untargeted metabolomics data by principal component analysis and orthogonal partial least squares discriminant analysis revealed a separation between SCHK and clinically healthy goats. According to the screening criteria (unpaired t-test, P < 0.05), 30 differentially altered metabolites and 115 differentially altered lipids were detected. Pathway enrichment analysis identified citrate cycle, alanine, aspartate and glutamate metabolism, glyoxylate and dicarboxylate metabolism, and phenylalanine metabolism as significantly altered pathways. A greater concentration of plasma isocitric acid and cis-aconitic acid levels was observed in SCHK goats. In addition, AA such as lysine and isoleucine were greater, whereas alanine and phenylacetylglycine were lower in SCHK dairy goats. Dairy goats with SCHK also exhibited greater oleic acid, acylcarnitine, and phosphatidylcholine and lower choline and sphingomyelins. Acylcarnitines, oleic acid, and tridecanoic acid displayed positive correlations with several lipid species. Alanine, hippuric acid, and histidinyl-phenylalanine were negatively correlated with several lipids. Overall, altered metabolites in SCHK dairy goats indicated a more severe degree of negative energy balance. Data also indicated an imbalance in the tricarboxylic acid (TCA) cycle, lipid metabolism, and AA metabolism. The findings provide a more comprehensive understanding of the pathogenesis of SCHK in dairy goats.

Symposium review: The impact of absorbed nutrients on energy partitioning throughout lactation

Most nutrition models and some nutritionists view ration formulation as accounting transactions to match nutrient supplies with nutrient requirements. However, diet and stage of lactation interact to alter the partitioning of nutrients toward milk and body reserves, which, in turn, alters requirements. Fermentation and digestion of diet components determine feeding behavior and the temporal pattern and profile of absorbed nutrients. The pattern and profile, in turn, alter hormonal signals, tissue responsiveness to hormones, and mammary metabolism to affect milk synthesis and energy partitioning differently depending on the physiological state of the cow. In the fresh period (first 2 to 3 wk postpartum), plasma insulin concentration and insulin sensitivity of tissues are low, so absorbed nutrients and body reserves are partitioned toward milk synthesis. As lactation progresses, insulin secretion and sensitivity increase, favoring deposition instead of mobilization of body reserves. High-starch diets increase ruminal propionate production, the flow of gluconeogenic precursors to the liver, and blood insulin concentrations. During early lactation, the glucose produced will preferentially be used by the mammary gland for milk production. As lactation progresses and milk yield decreases, glucose will increasingly stimulate repletion of body reserves. Diets with less starch and more digestible fiber increase ruminal production of acetate relative to propionate and, because acetate is less insulinogenic than propionate, these diets can minimize body weight gain. High dietary starch concentration and fermentability can also induce milk fat depression by increasing the production of biohydrogenation intermediates that inhibit milk fat synthesis and thus favor energy partitioning away from the mammary gland. Supplemental fatty acids also impact energy partitioning by affecting insulin concentration and insulin sensitivity of tissues. Depending on profile, physiological state, and interactions with other nutrients, supplemental fatty acids might increase milk yield at the expense of body reserves or partition energy to body reserves at the expense of milk yield. Supplemental protein or AA also can increase milk production but there is little evidence that dietary protein directly alters whole-body partitioning. Understanding the biology of these interactions can help nutritionists better formulate diets for cows at various stages of lactation.

Multi-Tissue Transcriptome Study of Innate Immune Gene Expression Profiling Reveals Negative Energy Balance Altered the Defense and Promoted System Inflammation of Dairy Cows

Negative energy balance (NEB) during the perinatal period leads to metabolic and immunological disorders in dairy cows, resulting in systemic responses and inflammation. The innate immune system is crucial for the host's protection and inflammatory response. However, systematic research is still lacking on how NEB affects the innate immune system to alter the 'host defense capability and inflammatory response. In this investigation, raw transcriptome data of adipose, blood, endometrial, hypothalamus, and liver tissues were downloaded from a public database, cleaned, aligned, quantified, and batch-corrected. The innate immune gene list was retrieved from innateDB, followed by the expression matrix of innate immune genes in various tissues for differential expression analysis, principle component analysis (PCA), and gene set enrichment analysis (GSEA). Under the effect of NEB, adipose tissue had the most differentially expressed genes, which were predominantly up-regulated, whereas blood GSEA had the most enriched biological processes, which were predominantly down-regulated. The gene sets shared by different tissues, which are predominantly involved in biological processes associated with defense responses and inflammation, were dramatically down-regulated in endometrial tissues and highly up-regulated in other tissues. Under the impact of NEB, LBP, PTX3, S100A12, and LCN2 play essential roles in metabolism and immunological control. In conclusion, NEB can downregulate the defensive response of innate immune genes in endometrial, upregulate the immune and inflammatory response of other tissues, activate the host defense response, and increase the systemic inflammatory response. The analysis of the effects of NEB on innate immune genes from the multiple tissues analysis provides new insights into the crosstalk between metabolism and immunity and also provides potential molecular targets for disease diagnosis and disease resistance breeding in dairy cows.

Medium chain fatty acid supplementation improves animal metabolic and immune status during the transition period: A study on dairy cattle

The transition period is the stage of the high incidence of metabolic and infectious diseases in dairy cows. Improving transition dairy cows' health is crucial for the industry. This study aimed to determine the effects of dietary supplementation medium-chain fatty acids (MCFAs) on immune function, metabolic status, performance of transition dairy cows. Twenty multiparous Holstein cows randomly assigned to two treatments at 35 d before calving. 1) CON (fed the basal 2) MCFA treatment (basal diet was supplemented at an additional 20 g MCFAs mixture every day) until 70 d after calving. The results showed that the serum amyloid A myeloperoxidase concentrations in the blood of cows in MCFA treatment significantly decreased during the early lactation (from 1 d to 28 d after calving) 0.03, 0.04, respectively) compared with the CON, while the tumor necrosis factor concentration was significantly decreased at 56 d after calving (P = 0.02). In addition, the concentration of insulin in the pre-calving (from 21 d before calving to calving) blood of cows in MCFA treatment was significantly decreased (P = 0.04), and concentration of triglyceride also showed a downward trend at 28 d after calving 0.07). Meanwhile, MCFAs supplementation significantly decreased the concentrations of lithocholic acid, hyodeoxycholic acid, and hyocholic acid in the blood at 1 d calving (P = 0.02, < 0.01, < 0.01, respectively), and the level of hyocholic acid taurocholic acid concentrations (P < 0.01, = 0.01, respectively) decreased dramatically at 14 d after calving. However, compared with the CON, the pre-calving dry matter intake and the early lactation milk yield in MCFA treatment were significantly decreased (P = 0.05, 0.02, respectively). In conclusion, MCFAs supplementation transition diet could improve the immune function and metabolic status of dairy cows, and the health of transition cows might be beneficial from the endocrine status.

Effects of the central melanocortin system on feed intake, metabolic hormones and insulin action in the sheep

Voluntary feed intake is insufficient to meet the nutrient demands associated with late pregnancy in prolific ewes and early lactation in high-yielding dairy cows. Under these conditions, peripheral signals such as growth hormone and ceramides trigger adaptations aimed at preserving metabolic well-being. Recent work in rodents has shown that the central nervous system-melanocortin (CNS-MC) system, consisting of alpha-melanocyte-stimulating hormone (α-MSH) and agouti-related peptide (AGRP) acting respectively as agonist and antagonist on central MC receptors, contributes to the regulation of some of the same adaptations. To assess the effects of the CNC-MC on peripheral adaptations in ruminants, ewes were implanted with an intracerebroventricular cannula in the third ventricle and infused over days with artificial cerebrospinal fluid (aCSF), the α-MSH analog melanotan-I (MTI), or AGRP. Infusion of MTI at 0.03 nmol/h reduced intake, expressed as a fold of maintenance energy requirement (M), from 1.8 to 1.1 M (P < 0.0001), whereas AGRP at 0.3 nmol/h increased intake from 1.8 to 2.0 M (P < 0.01); these doses were used in all subsequent experiments. To assess the effect of MTI on plasma variables, sheep were fed ad libitum and infused with aCSF or MTI or pair-fed to MTI-treated sheep and infused with aCSF (aCSFPF). Feed intake of the MTI and aCSFPF groups was 40% lower than the aCSF group (P < 0.0001). MTI increased plasma triiodothyronine and thyroxine in an intake-independent manner (P < 0.05 or less) but was devoid of effects on plasma glucose, insulin, and cortisol. None of these variables were altered by AGRP infusion in sheep fed at a fixed intake of 1.6 M. To assess the effect of CNS-MC activation on insulin action, ewes were infused with aCSF or MTI over the last 3 d of a 14-d period when energy intake was limited to 0.3 M and studied under basal conditions and during hyperinsulinemic-euglycemic clamps. MTI had no effect on plasma glucose, plasma insulin, or glucose entry rate under basal conditions but blunted the ability of insulin to inhibit endogenous glucose production during hyperinsulinemic-euglycemic clamps (P < 0.0001). Finally, MTI tended to reduce plasma leptin in sheep fed at 0.3 M (P < 0.08), and this effect became significant at 0.6 M (P < 0.05); MTI had no effect on plasma adiponectin irrespective of feeding level. These data suggest a role for the CNC-MC in regulating metabolic efficiency and peripheral insulin action.

The Focus on Core Genetic Factors That Regulate Hepatic Injury in Cattle Seems to be Important for the Dairy Sector’s Long-Term Development

The cattle during the perinatal period, as well as malnutrition, generate oxidative stress which leads to high culling rates of calves after calving across the world. Although metabolic diseases have such a negative impact on the welfare and economic value of dairy cattle, that becomes a serious industrial concern across the world. According to research, genetic factors have a role or controlling fat deposition in the liver by influencing the biological processes of hepatic lipid metabolism, insulin resistance, gluconeogenesis, oxidative stress, endoplasmic reticulum stress, and inflammation, all of which contribute to hepatic damage. This review focuses on the critical regulatory mechanisms of VEGF, mTOR/AKT/p53, TNF-alpha, Nf-kb, interleukin, and antioxidants that regulate lipid peroxidation in the liver via direct or indirect pathways, suggesting that they could be a potential critical therapeutic target for hepatic disease.

Effects of acute intravenous lipopolysaccharide administration on the plasma lipidome and metabolome in lactating Holstein cows experiencing hyperlipidemia

INTRODUCTION

The effects of lipopolysaccharides (i.e., endotoxin; LPS) on metabolism are poorly defined in lactating dairy cattle experiencing hyperlipidemia.

OBJECTIVES

Our objective was to explore the effects of acute intravenous LPS administration on metabolism in late-lactation Holstein cows experiencing hyperlipidemia induced by intravenous triglyceride infusion and feed restriction.

METHODS

Ten non-pregnant lactating Holstein cows (273 ± 35 d in milk) were administered a single bolus of saline (3 mL of saline; n [Formula: see text] 5) or LPS (0.375 [Formula: see text]g of LPS/kg of body weight; n [Formula: see text] 5). Simultaneously, cows were intravenously infused a triglyceride emulsion and feed restricted for 16 h to induce hyperlipidemia in an attempt to model the periparturient period. Blood was sampled at routine intervals. Changes in circulating total fatty acid concentrations and inflammatory parameters were measured. Plasma samples were analyzed using untargeted lipidomics and metabolomics.

RESULTS

Endotoxin increased circulating serum amyloid A, LPS-binding protein, and cortisol concentrations. Endotoxin administration decreased plasma lysophosphatidylcholine (LPC) concentrations and increased select plasma ceramide concentrations. These outcomes suggest modulation of the immune response and insulin action. Lipopolysaccharide decreased the ratio of phosphatidylcholine to phosphatidylethanomanine, which potentially indicate a decrease in the hepatic activation of phosphatidylethanolamine N-methyltransferase and triglyceride export. Endotoxin administration also increased plasma concentrations of pyruvic and lactic acids, and decreased plasma citric acid concentrations, which implicate the upregulation of glycolysis and downregulation of the citric acid cycle (i.e., the Warburg effect), potentially in leukocytes.

CONCLUSION

Acute intravenous LPS administration decreased circulating LPC concentrations, modified ceramide and glycerophospholipid concentrations, and influenced intermediary metabolism in dairy cows experiencing hyperlipidemia.

Relationships between Milk and Blood Biochemical Parameters and Metabolic Status in Dairy Cows during Lactation

This study aimed to determine blood and milk metabolic parameters and their correlations for the purpose of evaluating metabolic status in dairy cows. Blood and milk samples were collected from 100 Holstein dairy cows during morning milking. The cows were allocated to four groups according to the production period, including cows in early (n = 18), full (n = 26), mid (n = 25) and late (n = 31) lactation. The value of non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHB), glucose, triglycerides (TG), total cholesterol (TChol), total protein (TP), albumin, globulin, urea, total bilirubin (TBil), aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), and lactate dexydrogenase (LDH) in the blood were determined. The following milk parameters were measured: fat, protein, lactose, urea, AST, ALT, ALP, GGT, LDH and BHB. Blood serum NEFA, BHB, TBil, AST, ALT, ALP and LDH were higher in early lactation cows, whereas glucose, TP, globulin and urea levels were significantly lower in early lactation cows. Milk fat and lactose levels were lower in early lactation cows, whereas milk protein and the activities of AST, ALT, ALP and LDH in milk were highly greater in early lactation cows. Milk fat was positively correlated with glucose, TP and TG, and negatively correlated with BHB, NEFA, TBil, ALT, LDH and ALP levels in the blood. Enzyme activities in milk were positively correlated with those in blood and with blood NEFA, BHB and TBil levels, and negatively correlated with blood glucose, TChol and TG. A significant positive correlation existed between blood and milk BHB values. Many correlations showed the same slope during all lactation periods. In conclusion, similar changes in blood and milk metabolite concentration during lactation and milk to blood correlations confirm that milk has great potential in predicting of blood metabolites and metabolic status of cows.

Ceramide metabolism associated with chronic dietary nutrient surplus and diminished insulin sensitivity in the liver, muscle, and adipose tissue of cattle

High dietary energy and protein supply is common practice in livestock nutrition, aiming to maximize growth and production performance. However, a chronic nutritional surplus induces obesity, promotes insulin insensitivity, and triggers low-grade inflammation. Thirty Holstein bulls were randomly assigned to two groups, low energy and protein (LEP), and high energy and protein (HEP) intake, provided from the 13th to the 20th month of life. Body weight, carcass composition, laminitis score, and circulating insulin and glucose concentrations were assessed. The expression and extent of phosphorylation of insulin signaling proteins were measured in the liver, muscle, and adipose tissue. The sphingolipid metabolome was quantified by a targeted liquid chromatography-mass spectrometry based metabolomics approach. The HEP bulls were obese, had hyperinsulinemia with euglycemia, and expressed clinical signs of chronic laminitis. In the liver, protein kinase B (PKB) phosphorylation was decreased and this was associated with a higher tissue concentration of ceramide 16:0, a sphingolipid that diminishes insulin action by dephosphorylating PKB. In the adipose tissue, insulin receptor expression was lower in HEP bulls, associated with higher concentration of hexosylceramide, which reduces the abundance of functional insulin receptors. Our findings confirm that diet-induced metabolic inflammation triggers ceramide accumulation and disturbs insulin signaling. As insulin insensitivity exacerbates metabolic inflammation, this self-reinforcing cycle could explain the deterioration of metabolic health apparent as chronic laminitis. By demonstrating molecular relationships between insulin signaling and sphingolipid metabolism in three major tissues, our data extend our mechanistic understanding of the role of ceramides in diet-induced metabolic inflammation.

Weighted Gene Co-expression Network Analysis Identifies Specific Modules and Hub Genes Related to Subacute Ruminal Acidosis

Weighted gene co-expression network analysis (WGCNA) was used to understand the pathogenesis of subacute ruminal acidosis (SARA) and identify potential genes related to the disease. Microarray data from dataset GSE143765, which included 22 cows with and nine cows without SARA, were downloaded from the NCBI Gene Expression Omnibus (GEO). Results of WGCNA identified highly correlated modules of sample genes, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses allowed further biological insights into SARA-related modules. The protein-protein interaction (PPI) network, modules from the PPI network, and cistron annotation enrichment of modules were also analyzed. A total of 14,590 DEGs were used for the WGCNA. Construction of a protein-protein network identified DCXR, MMP15, and MMP17 as hub genes. Functional annotation showed that DCXR mainly exhibited L-xylulose reductase (NADP+) activity, glucose metabolic process, xylulose metabolic process, and carbonyl reductase (NADPH) activity, which are involved in the pentose and glucuronate interconversion pathways. MMP15 and MMP17 mainly have a collagen catabolic process. Overall, the results of this study aid the clarification of the biological and metabolic processes associated with SARA at the molecular level. The data highlight potential mechanisms for the future development of intervention strategies to reduce or alleviate the risk of SARA.

Metabolic Responses to Epinephrine by Periparturient Dairy Cows Fed Prepartum Diets Differing in Predicted Metabolizable Protein Supply

We determined the effects of prepartum dietary metabolizable protein (MP) supply on lipolytic and glucose response to epinephrine stimulus during the periparturient period. Twelve non-lactating cows in second or greater pregnancies were assigned to a low MP (LMP) diet formulated to provide ~900 g/day MP or a high MP (HMP) diet to provide ~1,100 g/day MP. Cows received prepartum diets from 28 days before expected parturition to day of parturition and then received a common lactation diet until 35 days postpartum. Blood was sampled weekly to day −7, daily to day 7, and weekly through day 35 relative to parturition for analysis of glucose, non-esterified fatty acids (NEFAs), 3-hydroxybutyrate (BHB), urea N, and total protein concentrations. Epinephrine challenges were conducted on day −10 before expected parturition and days 7 and 14 postpartum. Epinephrine [1.4 μg/kg body weight (BW)] was administered via jugular vein and blood was collected from the opposite jugular vein from −45 min to +120 min relative to epinephrine administration. Plasma was analyzed for glucose and NEFA concentrations. Prepartum dry matter intake (DMI) (14.7 and 12.6 ± 1.5 kg/day for LMP and HMP, respectively), postpartum DMI (21.4 and 19.4 ± 1.3 kg/day for LMP and HMP, respectively), and 4% fat-corrected milk (FCM) (37.0 and 36.8 ± 1.5 kg/day for LMP and HMP, respectively) did not differ significantly between diets. Cows fed HMP had higher plasma concentrations of urea N prepartum than cows fed LMP (14.0 vs. 7.9 ± 0.8 mg/dl). Cows fed HMP tended to have greater prepartum concentrations of total protein in plasma than those fed LMP (7.5 vs. 7.0 ± 0.2 g/dl). The area under the curve (AUC) for NEFA response to epinephrine did not differ between diets, but differed by day relative to parturition [8,284, 29,018, and 18,219 ± 2,302 min × (μeq/l) for days −10, 7, and 14, respectively]. Maximal response of NEFA concentration to epinephrine was greater for HMP than for LMP (744 vs. 438 ± 72 μeq/l). The glucose AUC did not differ between diets or among days. Lipolytic response, but not glucose response, to epinephrine was enhanced during the early postpartum period relative to the late dry period. However, those responses were not affected by prepartum MP supply.

Effects of Different Prenatal Nutrition Strategies on the Liver Metabolome of Bulls and Its Correlation with Body and Liver Weight

This study investigated the effect of prenatal nutrition on liver metabolome and on body (BW) and liver weight (LW) of Nellore bulls at slaughter. Three treatments were applied in 126 cows during pregnancy: NP—control (mineral supplementation); PP—protein-energy supplementation in the third trimester; and FP—protein-energy supplementation during the entire pregnancy. Offspring BW and LW were evaluated, and a targeted metabolomics analysis was performed on their livers (n = 18, 22.5 ± 1 months of age). Data were submitted to principal component analysis (PCA), analysis of variance (ANOVA), enrichment analysis, and Pearson’s correlation analysis. The phenotypes did not show differences between treatments (p > 0.05). Metabolites PCA showed an overlap of treatment clusters in the analysis. We found significant metabolites in ANOVA (p ≤ 0.05; Glycine, Hydroxytetradecadienylcarnitine, Aminoadipic acid and Carnosine). Enrichment analysis revealed some biological processes (Histidine metabolism, beta-Alanine metabolism, and Lysine degradation). Pearson’s correlation analysis showed 29 significant correlated metabolites with BW and 1 metabolite correlated with LW. In summary, prenatal nutrition did not show effects on the phenotypes evaluated, but affected some metabolites and biological pathways, mainly related to oxidative metabolism. In addition, BW seems to influence the hepatic metabolome more than LW, due to the amount and magnitude of correlations found.

Identification and characterization of dairy cows with different backfat thickness antepartum in relation to postpartum loss of backfat thickness: A cluster analytic approach

The objectives of this study were (1) to characterize the interindividual variation in the relationship between antepartum (ap) backfat thickness (BFT) and subsequent BFT loss during early lactation in a large dairy herd using cluster analysis; (2) to compare the serum concentrations of metabolites (nonesterified fatty acids, β-hydroxybutyrate), metabolic hormones (leptin and adiponectin), and an inflammatory marker (haptoglobin) among the respective clusters; and (3) to compare lactation performance and uterine health status in the different clusters. An additional objective was (4) to investigate differences in these serum variables and in milk yield of overconditioned (OC) cows that differed in the extent of BFT loss. Using data from a large study of 1,709 multiparous Holstein cows, we first selected those animals from which serum samples and BFT results (mm) were available at d 25 (±10) ap and d 31 (±3 d) postpartum (pp). The remaining 713 cows (parity of 2 to 7) were then subjected to cluster analysis: different approaches based on the BFT of the cows were performed. K-means (unsupervised machine learning algorithm) clustering based on BFT-ap alone identified 5 clusters: lean (5-8 mm BFT, n = 50), normal (9-12 mm, n = 206), slightly fat (SF; 13-16 mm, n = 203), just fat (JF; 16-22 mm, n = 193), and very fat (VF; 23-43 mm, n = 61). Clustering by difference between BFT-ap and BFT-pp (ΔBFT) also revealed 5 clusters: extreme loss (17-23 mm ΔBFT, n = 16), moderate loss (9-15 mm, n = 119), little loss (4-8 mm, n = 326), no loss (0-3 mm, n = 203), and gain (-8 to -1 mm, n = 51). Based on the blood variables measured, our results confirm that cows with greater BFT losses had higher lipid mobilization and ketogenesis than cows with less BFT loss. The serum variables of cows that gained BFT did not differ from normal cows. Milk yield was affected by the BFT-ap cluster, but not by the ΔBFT cluster. Cows categorized as VF had lesser milk yield than other clusters. We further compared the OC cows that had little or no BFT loss (i.e., 2% of VF, 12% of JF, and 31% of SF, OC-no loss, n = 85) with the OC cows that lost BFT (OC-loss, n = 135). Both NEFA and BHB pp concentrations and milk yield were greater in OC-loss cows compared with the OC-no loss cows. The serum concentration of leptin ap was greater in OC-loss than in the OC-no loss cows. Overall, OC cows lost more BFT than normal or lean cows. However, those OC cows with a smaller loss of BFT produced less milk than OC cows with greater losses.

Effects of the SLICK1 mutation in PRLR on regulation of core body temperature and global gene expression in liver in cattle

The SLICK1 mutation in bovine PRLR (c.1382del; rs517047387) is a deletion mutation resulting in a protein with a truncated intracellular domain. Cattle carrying at least one allele have a phenotype characterized by a short hair coat (slick phenotype) and increased resistance to heat stress. Given the pleiotropic nature of prolactin, the mutation may affect other physiological characteristics. The liver is one organ that could potentially be affected because of the expression of PRLR. The mutation is a dominant allele, and heterozygous animals have a similar hair coat to that of animals homozygous for the mutation. Present objectives were to determine whether inheritance of the SLICK1 mutation affects liver gene expression and if animals homozygous for the SLICK1 allele differ from heterozygotes in liver gene expression and regulation of body temperature during heat stress. In one experiment, rectal and ruminal temperatures were less for Holstein heifers that were heterozygous for the SLICK1 allele compared with wildtype heifers. There were 71 differentially expressed genes in liver, with 13 upregulated and 58 downregulated in SLICK1 heterozygotes. Among the ontologies characteristic of differentially expressed genes were those related to immune function and fatty acid and amino acid metabolism. In a prospective cohort study conducted with adult Senepol cattle, body temperature and hepatic gene expression were compared between animals heterozygous or homozygous for the SLICK1 mutation. There were no differences in ruminal temperatures between genotypes, rectal temperature was higher in animals homozygous for the SLICK1 mutation, and there was only one gene in liver that was differentially expressed. It was concluded that inheritance of the SLICK1 allele can exert functional changes beyond those related to hair growth although changes in liver gene expression were not extensive. Results are also consistent with the SLICK1 allele being dominant because there were few differences in phenotype between animals inheriting one or two copies of the allele.

Effects of Concentrate Levels in Prepartum Diet on Milk Performance, Energy Balance and Rumen Fermentation of Transition Montbéliarde-Holstein Crossbred Cows

This study was conducted to investigate the effect of three rates of prepartum dietary concentrate feeding on the milk performance, energy balance, and rumen fermentation of Montbéliarde−Holstein crossbred cows. Eighteen transition Montbéliarde−Holstein crossbred cows with similar days of gestation (258 ± 12 day) and body weights (622 ± 44 kg) were selected and randomly divided into three groups. In the prepartum period, the addition of concentrates accounted for 0.3% (low concentrate, LC), 0.6% (medium concentrate, MC), and 0.9% (high concentrate, HC) of the cow’s body weight. The forage was corn stover, which was fed to the cows ad libitum with free access to water. Postpartum, all of the cows were fed a common lactation total mixed ration. The experimental period lasted from 21 days prepartum to 28 days postpartum. The energy balance (EB), net energy intake (NEI), and dry matter intake (DMI) of the HC group were greater than those of the other groups (p < 0.05). Likewise, the non-esterified fatty acids (NEFA), β-hydroxybutyric acid (BHBA), and total bilirubin (TBIL) in the blood of the LC group had significantly higher concentrations than they did in the other groups (p < 0.05). Moreover, the increase in the level of dietary concentrate had no significant effect on the rumen fermentation parameters (p > 0.05), and the total intestinal digestibility of dry matter (DM), crude protein (CP), and ether extract (EE) in the HC group was significantly higher (p < 0.05) than it was in the other groups during the prepartum period. In conclusion, the administration of the MC diet in the prepartum period had no negative effect on the performance and rumen fermentation of postpartum dairy cows and can satisfy the energy needs of prepartum dairy cows. Therefore, under our experimental conditions, the 0.6% prenatal concentrate feeding amount was the most appropriate for Montbéliarde−Holstein crossbred cows.

Protective Mechanism of Leucine and Isoleucine against H2O2-Induced Oxidative Damage in Bovine Mammary Epithelial Cells

Leucine and isoleucine possess antioxidative and anti-inflammatory properties. However, their underlying protective mechanisms against oxidative damage remain unknown. Therefore, in this study, the protective mechanism of leucine and isoleucine against H₂O₂-induced oxidative damage in a bovine mammary epithelial cell lines (MAC-T cells) were investigated. Briefly, MAC-T cells exposed or free to H₂O₂ were incubated with different combinations of leucine and isoleucine. The cellular relative proliferation rate and viability, oxidative stress indicators, and inflammatory factors were determined by specific commercial kits. The genes related to barrier functions was measured by real-time quantitative PCR. The protein expression differences were explored by 4D label-free quantitative proteomic analyses and validated by parallel reaction monitoring. The results revealed that leucine and isoleucine increased cell proliferation, total antioxidant status (TAS), and the relative mRNA expression of occludin, as well as decreased malondialdehyde (MDA), total oxidant status (TOS)/TAS, IL-6, IL-1β, and TOS. When leucine and isoleucine were combined, MDA, TOS/TAS, and the relative mRNA expression levels of claudin-1, occludin, and zonula occludens-1 increased when compared to leucine or isoleucine alone. Proteomics analyses revealed that leucine significantly upregulated the propanoate metabolism; valine, leucine, and isoleucine degradation; and thermogenesis pathways, whereas isoleucine significantly upregulated the peroxisome and propanoate metabolism pathways. In conclusion, leucine protected MAC-T cells from H₂O₂-induced oxidative stress by generating more ATP to supplement energy demands, and isoleucine improved the deficit in peroxisome transport and promoted acetyl-CoA production. The findings of this study enhance our understanding of the protective mechanisms of leucine and isoleucine against oxidative damage.

Limiting factors for milk production in dairy cows: perspectives from physiology and nutrition

Milk production in dairy cows increases worldwide since many decades. With rising milk yields, however, potential limiting factors are increasingly discussed. Particularly, the availability of glucose and amino acids is crucial to maintain milk production as well as animal health. Limitations arise from feed sources, the rumen and digestive tract, tissue mobilization, intermediary metabolism and transport, and the uptake of circulating nutrients by the lactating mammary gland. The limiting character can change depending on the stage of lactation. Although physiological boundaries are prevalent throughout the gestation-lactation cycle, limitations are aggravated during the early lactation period when high milk production is accompanied by low feed intake and high mobilization of body reserves. The knowledge about physiological constraints may help to improve animal health and make milk production more sustainably. The scope of this review is to address contemporary factors related to production limits in dairy cows from a physiological perspective. Besides acknowledged physiological constraints, selected environmental and management-related factors affecting animal performance and physiology will be discussed. Potential solutions and strategies to overcome or to alleviate these constraints can only be presented briefly. Instead, they are thought to address existing shortcomings and to identify possibilities for optimization. Despite a scientific-based view on physiological limits, we should keep in mind that only healthy animals could use their genetic capacity and produce high amounts of milk.

Transcriptomic and Metabolomic Analyses Reveal Inhibition of Hepatic Adipogenesis and Fat Catabolism in Yak for Adaptation to Forage Shortage During Cold Season

Animals have adapted behavioral and physiological strategies to conserve energy during periods of adverse conditions. Hepatic glucose is one such adaptation used by grazing animals. While large vertebrates have been shown to have feed utilization and deposition of nutrients—fluctuations in metabolic rate—little is known about the regulating mechanism that controls hepatic metabolism in yaks under grazing conditions in the cold season. Hence, the objective of this research was to integrate transcriptomic and metabolomic data to better understand how the hepatic responds to chronic nutrient stress. Our analyses indicated that the blood parameters related to energy metabolism (glucose, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, lipoprotein lipase, insulin, and insulin-like growth factor 1) were significantly (p &lt; 0.05) lower in the cold season. The RNA-Seq results showed that malnutrition inhibited lipid synthesis (particularly fatty acid, cholesterol, and steroid synthesis), fatty acid oxidation, and lipid catabolism and promoted gluconeogenesis by inhibiting the peroxisome proliferator-activated receptor (PPAR) and PI3K-Akt signaling pathways. For metabolite profiles, 359 metabolites were significantly altered in two groups. Interestingly, the cold season group remarkably decreased glutathione and phosphatidylcholine (18:2 (2E, 4E)/0:0). Moreover, integrative analysis of the transcriptome and metabolome demonstrated that glycolysis or gluconeogenesis, PPAR signaling pathway, fatty acid biosynthesis, steroid biosynthesis, and glutathione metabolism play an important role in the potential relationship between differential expression genes and metabolites. The reduced lipid synthesis, fatty acid oxidation, and fat catabolism facilitated gluconeogenesis by inhibiting the PPAR and PI3K-Akt signaling pathways to maintain the energy homeostasis of the whole body in the yak, thereby coping with the shortage of forages and adapting to the extreme environment of the Qinghai-Tibetan Plateau (QTP).

The Correlation between Extracellular Heat Shock Protein 70 and Lipid Metabolism in a Ruminant Model

Metabolic stress in early lactation cows is characterized by lipolysis, ketogenesis, insulin resistance and inflammation because of negative energy balance and increased use of lipids for energy needs. In this study the relationship between lipid metabolite, lipid-based insulin resistance, and hepatocyte functionality indexes and tumor necrosis factor alpha (TNF-α) with extracellular heat shock protein 70 (eHsp70) was investigated. The experiment included 50 cows and all parameters were measured in blood serum. In cows with a more pronounced negative energy balance, the following was determined: a higher concentration of eHsp70, TNF-α, non-esterified fatty acid (NEFA), beta-hydroxybutyrate (BHB), NEFA to insulin and NEFA to cholesterol ratio and lower concentration of cholesterol, very low-density lipoproteins (VLDL), low density lipoproteins (LDL) and liver functionality index (LFI). The eHsp70 correlated negatively with the values of cholesterol, VLDL, LDL, and triglycerides, while correlated positively with the level of NEFA and BHB. A higher concentration of eHsp70 suggests the development of fatty liver (due to a higher NEFA to cholesterol ratio and lower LFI) and insulin resistance (due to a lower revised quantitative insulin sensitivity check index RQUICKI-BHB and higher NEFA to insulin ratio). The eHsp70 correlated positively with TNF-α. Both TNF-α and eHsp70 correlated similarly to lipid metabolites. In cows with high eHsp70 and TNF-α values we found higher concentrations of NEFA, BHB, NEFA to insulin and NEFA to cholesterol ratio and a lower concentration of triglycerides and VLDL cholesterol compared to cows that had only high TNF-α values. Based on the positive correlation between eHsp70 and TNF-α, their similar relations, and the additional effect of eHsp70 (high TNF-α + eHsp70 values) on lipid metabolites we conclude that eHsp70 has pro-inflammatory effects implicating lipolysis, fatty liver, and fat tissue insulin resistance.

Metabogenomic analysis to functionally annotate the regulatory role of long non-coding RNAs in the liver of cows with different nutrient partitioning phenotype

Long non-coding RNAs (lncRNAs) hold gene regulatory potential, but require substantial further functional annotation in livestock. Applying two metabogenomic approaches by combining transcriptomic and metabolomic analyses, we aimed to identify lncRNAs with potential regulatory function for divergent nutrient partitioning of lactating crossbred cows and to establish metabogenomic interaction networks comprising metabolites, genes and lncRNAs. Through correlation analysis of lncRNA expression with transcriptomic and metabolomic data, we unraveled lncRNAs that have a putative regulatory role in energy and lipid metabolism, the urea and tricarboxylic acid cycles, and gluconeogenesis. Especially FGF21, which correlated with a plentitude of differentially expressed genes, differentially abundant metabolites, as well as lncRNAs, suggested itself as a key metabolic regulator. Notably, lncRNAs in close physical proximity to coding-genes as well as lncRNAs with natural antisense transcripts appear to perform a fine-tuning function in gene expression involved in metabolic pathways associated with different nutrient partitioning phenotypes.

The crucial role of lysine in the hepatic metabolism of growing Holstein dairy heifers as revealed by LC-MS-based untargeted metabolomics

The objective of this experiment was to evaluate the effect of supplementing rumen-protected Lys based on a Lys-deficient diet on liver metabolism in growing Holstein heifers. The experiment was conducted for 3 months with 36 Holstein heifers (initial body weight: 200 ± 9.0 kg; 7-month-old). Heifers were randomly assigned to 2 diets based on corn, soybean meal, alfalfa hay, and wheat bran: control, Lys-deficient diet (LD; 0.66% Lys in diet), and Lys-adequate diet (LA; 1.00% Lys in diet). The results showed no difference in growth performance between the 2 groups (P > 0.05). However, there was a clear trend of increasing feed conversion rate with Lys supplementation (0.05 < P < 0.01). The serum urea nitrogen concentration was significantly decreased, and the aspartate aminotransferase-to-alanine aminotransferase ratio was significantly decreased by Lys supplementation (P < 0.05). Moreover, growing heifers fed a Lys-adequate diet had lower levels of urine nitrogen excretion and higher levels of the biological value of nitrogen (P < 0.05). Metabolomic analysis revealed that 5 types of phosphatidylcholine and 3 types of ceramide were significantly increased and enriched in sphingolipid metabolism and glycerophospholipid metabolism (P < 0.05). His, Leu, and Asp levels were significantly decreased in the liver following Lys supplementation (P < 0.05). In conclusion, Lys supplementation may promote the synthesis of body tissue proteins, as evidenced by significantly decreased amino acids in the liver and urine N excretion, it also improves hepatic lipid metabolism by providing lipoprotein precursors.

Fibroblast growth factor 21 in dairy cows: current knowledge and potential relevance

Fibroblast growth factor 21 (FGF21) has been identified as an important regulator of carbohydrate and lipid metabolism, which plays an important role for metabolic regulation, particularly under conditions of energy deprivation or stress conditions. Dairy cows are subjected to a negative energy balance and various kinds of stress particularly during the periparturient phase and during early lactation. It has been shown that the plasma concentration of FGF21 in dairy cows is dramatically increased at parturition and remains high during the first weeks of lactation. This finding suggests that FGF21 might exert similar functions in dairy cows than in other species, such as mice or humans. However, the role of FGF21 in dairy cows has been less investigated so far. Following a brief summary of the previous findings about the function of FGF21 in humans and mice, the present review aims to present the current state of knowledge about the role of FGF21 in dairy cows. The first part of the review deals with the tissue localization of FGF21 and with conditions leading to an upregulation of FGF21 expression in the liver of dairy cows. In the second part, the influence of nutrition on FGF21 expression and the role of FGF21 for metabolic diseases in dairy cows is addressed. In the third part, findings of exogenous FGF21 application on metabolism in dairy cows are reported. Finally, the potential relevance of FGF21 in dairy cows is discussed. It is concluded that FGF21 might be of great importance for metabolic adaptation to negative energy balance and stress conditions in dairy cows. However, further studies are needed for a better understanding of the functions of FGF21 in dairy cows.

Effects of dietary l-carnitine supplementation on the response to an inflammatory challenge in mid-lactating dairy cows: Hepatic mRNA abundance of genes involved in fatty acid metabolism

This study aimed at characterizing the effects of dietary l-carnitine supplementation on hepatic fatty acid (FA) metabolism during inflammation in mid-lactating cows. Fifty-three pluriparous Holstein dairy cows were randomly assigned to either a control (CON, n = 26) or an l-carnitine supplemented (CAR; n = 27) group. The CAR cows received 125 g of a rumen-protected l-carnitine product per cow per day (corresponding to 25 g of l-carnitine/cow per day) from d 42 antepartum (AP) until the end of the trial on d 126 postpartum (PP). Aside from the supplementation, the same basal diets were fed in the dry period and during lactation to all cows. In mid lactation, each cow was immune-challenged by a single intravenous injection of 0.5 μg of LPS/kg of BW at d 111 PP. Blood samples were collected before and after LPS administration. The mRNA abundance of in total 39 genes related to FA metabolism was assessed in liver biopsies taken at d -11, 1, and 14 relative to LPS (d 111 PP) and also on d 42 AP as an individual covariate using microfluidics integrated fluidic circuit chips (96.96 dynamic arrays). In addition to the concentrations of 3 selected proteins related to FA metabolism, acetyl-CoA carboxylase α (ACACA), 5' AMP-activated protein kinase (AMPK), and solute carrier family 25 member 20 (SLC25A20) were assessed by a capillary Western blot method in liver biopsies from d -11 and 1 relative to LPS from 11 cows each of CAR and CON. On d -11 relative to LPS, differences between the mRNA abundance in CON and CAR were limited to acyl-CoA dehydrogenase (ACAD) very-long-chain (ACADVL) with greater mRNA abundance in the CAR than in the CON group. The liver fat content decreased from d -11 to d 1 relative to the LPS injection and remained at the lower level until d 14 in both groups. One day after the LPS challenge, lower mRNA abundance of carnitine palmitoyltransferase 1 (CPT1), CPT2, ACADVL, ACAD short-chain (ACADS), and solute carrier family 22 member 5 (SLC22A5) were observed in the CAR group as compared with the CON group. However, the mRNA abundance of protein kinase AMP-activated noncatalytic subunit gamma 1 (PRKAG1), ACAD medium-chain (ACADM), ACACA, and FA binding protein 1 (FABP1) were greater in the CAR group than in the CON group on d 1 relative to LPS. Two weeks after the LPS challenge, differences between the groups were no longer detectable. The altered mRNA abundance before and 1 d after LPS pointed to increased transport of FA into hepatic mitochondria during systemic inflammation in both groups. The protein abundance of AMPK was lower in CAR than in CON before the LPS administration. The protein abundance of SLC25A20 was neither changing with time nor treatment and the ACACA protein abundance was only affected by time. In conclusion, l-carnitine supplementation temporally altered the hepatic mRNA abundance of some genes related to mitochondrial biogenesis and very-low-density lipoprotein export in response to an inflammatory challenge, but with largely lacking effects before and 2 wk after LPS.

Effects of rumen-protected choline supplementation in Holstein dairy cows during electric heat blanket-induced heat stress

Dairy cows experiencing heat stress (HS) attempt to thermoregulate through multiple mechanisms, such as reducing feed intake and milk production and altering blood flow to increase heat dissipation. Effects of choline on energy metabolism and immune function may yield it a viable nutritional intervention to mitigate negative effects of HS. The primary objective of this experiment was to determine if supplementation of rumen-protected choline during, or before and during, an increased heat load would ameliorate the negative effects of HS on production and immune status. Heat stress was induced via an electric heat blanket model with a 3-d baseline period and 7-d HS period for all cows. Multiparous mid-lactation (208 ± 31 days in milk) Holstein cows were fed the same basal herd diet, blocked by pre-experiment milk yield, and randomly assigned to receive one of the following: (1) no rumen-protected (RP) choline (n = 7); (2) RP choline (60 g/d) via top-dress during the HS period (n = 8); or (3) RP choline (60 g/d) via top-dress during the baseline and HS periods (n = 8). Imposing HS via electric heat blanket raised respiration rate with all cows surpassing the HS threshold of 60 breaths/min. The increase in respiration rate tended to be ameliorated with either schedule of RP choline supplementation. Milk yield tended to increase when RP choline was supplemented in both the baseline period and during HS. Supplementation of RP choline tended to reduce blood fatty acid and triglyceride and tended to increase the revised quantitative insulin sensitivity check index. The role of RP choline supplementation to partially ameliorate the effects of HS should be further explored as a potential nutritional strategy to mitigate the negative consequences of HS on health and production.

Muscle metabolome and adipose tissue mRNA expression of lipid metabolism-related genes in over-conditioned dairy cows differing in serum-metabotype

Over-conditioned dairy cows, classified by body condition score (BCS) and backfat thickness (BFT) are less able to metabolically adapt to the rapidly increasing milk yield after parturition. Based on serum metabolome and cluster analyses, high BCS cows (HBCS) could be classified into metabotypes that are more similar to normal (NBCS) cows, i.e., HBCS predicted normal (HBCS-PN) than the HBCS predicted high (HBCS-PH) cows—similar to the concept of obese but metabolically healthy humans. Our objective was to compare muscle metabolome and mRNA abundance of genes related to lipogenesis and lipolysis in adipose tissue between HBCS-PH (n = 13), HBCS-PN (n = 6), and NBCS-PN (n = 15). Tail-head subcutaneous fat was biopsied on d −49, 3, 21, and 84 relative to parturition. Potential differences in the oxidative capacity of skeletal muscle were assessed by targeted metabolomics in M. semitendinosus from d 21. Besides characteristic changes with time, differences in the mRNA abundance were limited to lipogenesis-related genes on d −49 (HBCS-PH > HBCS-PN). The HBCS-PH had more than two-fold higher muscle concentrations of short (C2, C4-OH, C6-OH) and long-chain acylcarnitines (C16, C18, and C18:1) than HBCS-PN, indicating a greater oxidative capacity for fatty acids (and utilization of ketones) in muscle of HBCS-PN than HBCS-PH cows.

Ketosis and its role in Bos taurus reproductive impairment

The analysis of relevant and significant scientific research on the physiological and biochemical aspects of ketosis, and the main mechanisms of influence on reproductive function in this metabolic pathology is presented. Strengthening breeding potential and creating conditions for its implementation through modern feeding and maintenance technologies led to the spread of diseases of non-communicable etiology, including ketosis diseases. Ketotic diseases cause various disorders in carbohydrate-lipid, protein, water-electrolyte and vitamin-mineral metabolism. The monitoring of studies on the biological role of ketosis showed its effect on animal fertility, quality of female gametes and fetal development. When considering ketosis, it is important to understand precisely the mechanisms of influence, since many methods for diagnosing and combating ketosis diseases are based on their knowledge. The key mechanisms of ketone bodies formation, the reasons for increase in their concentration were considered. It is of great practical importance for development of diagnostic tests that make it possible to determine the direction of disturbances in energy and plastic processes. Based on the data presented in the studies, conclusions were drawn about the role of -hydroxybutyric acid as a direct factor in reducing the reproductive function of Bos taurus .

Advances in fatty acids nutrition in dairy cows: from gut to cells and effects on performance

High producing dairy cows generally receive in the diet up to 5-6% of fat. This is a relatively low amount of fat in the diet compared to diets in monogastrics; however, dietary fat is important for dairy cows as demonstrated by the benefits of supplementing cows with various fatty acids (FA). Several FA are highly bioactive, especially by affecting the transcriptome; thus, they have nutrigenomic effects. In the present review, we provide an up-to-date understanding of the utilization of FA by dairy cows including the main processes affecting FA in the rumen, molecular aspects of the absorption of FA by the gut, synthesis, secretion, and utilization of chylomicrons; uptake and metabolism of FA by peripheral tissues, with a main emphasis on the liver, and main transcription factors regulated by FA. Most of the advances in FA utilization by rumen microorganisms and intestinal absorption of FA in dairy cows were made before the end of the last century with little information generated afterwards. However, large advances on the molecular aspects of intestinal absorption and cellular uptake of FA were made on monogastric species in the last 20 years. We provide a model of FA utilization in dairy cows by using information generated in monogastrics and enriching it with data produced in dairy cows. We also reviewed the latest studies on the effects of dietary FA on milk yield, milk fatty acid composition, reproduction, and health in dairy cows. The reviewed data revealed a complex picture with the FA being active in each step of the way, starting from influencing rumen microbiota, regulating intestinal absorption, and affecting cellular uptake and utilization by peripheral tissues, making prediction on in vivo nutrigenomic effects of FA challenging.

The Study of the Response of Fat Metabolism to Long-Term Energy Stress Based on Serum, Fatty Acid and Transcriptome Profiles in Yaks

Simple Summary

The serum, fatty acid and transcriptome profiles in the subcutaneous fat of yaks were measured to explore the effect of long-term energy stress (ES) on fat metabolism during the cold season. The study indicated that under long-term ES during the cold season, the amount of fat in yaks was less, and fat mobilization was one of the main ways by which energy was obtained in yaks. Yaks regulated fat metabolism in subcutaneous fat primarily through adenosine 5′-monophosphate-activated protein kinase (AMPK) signaling. Glucose (GLU) intake, fat catabolism, fatty acid synthesis and fatty acid oxidation in the subcutaneous fat of yaks were all inhibited, which resulted in the fat mobilization of yaks slowing as much as possible under long-term ES. In addition, the energy expenditures in fat cells were inhibited by regulating phosphatidylinositol 3’ -kinase (PI3K)-serine/threonine-protein kinase (Akt) andmammalian target of rapamycin (mTOR) signaling, and the limited energy obtained from GLU and fat was consumed by muscle and organs as much as possible. These factors led to an energy balance in yaks under long-term ES. The fat stored in yaks can be expended for as long as possible, and yaks can survive for as long as necessary under long-term ES.

Abstract

Long-term energy stress (ES) during the cold season is a serious problem for the breeding of yaks. In this paper, the response of fat metabolism in yaks to long-term ES during the cold season was studied. Gas chromatography (GC) analysis showed that the percentage of saturated fatty acids (SFAs) in the subcutaneous fat of the yaks in the ES group was 42.7%, which was less than the 56.6% in the CO group (p < 0.01) and the percentage of polyunsaturated unsaturated fatty acids (PUFAs) in the subcutaneous fat of the yaks in the ES group was 38.3%, which was more than the 26.0% in the CO group (p < 0.01). The serum analysis showed that fatty acid oxidation in yaks was increased under long-term ES. In the subcutaneous fat of yaks under long-term ES, the gene expression levels of glycerol-3-phosphate acyltransferase 4 (GPAT4), hormone-sensitive lipase (HSL), patatin-like phospholipase domain-containing protein 2 (PNPLA2), acyl-CoA dehydrogenase (ACAD), acyl-coenzyme A thioesterase 8 (ACOT8), facilitated glucose transporter (GLUT4), 3-oxoacyl-[acyl-carrier-protein] synthase (OXSM), oestradiol 17-beta-dehydrogenase 8 (HSD17B8) and malonate-Co-A ligase ACSF3 (ACSF3) were downregulated (q < 0.05), whereas the gene expression levels of aquaporin-7 (AQP7), long-chain-fatty-acid-CoA ligase (ACSL), elongation of very long chain fatty acids protein (ELOVL) and fatty acid desaturase 1 (FADS1) were upregulated (q < 0.05), indicating the inhibition of fat catabolism, fat anabolism, fatty acid oxidation, glucose (GLU) intake and SFA synthesis and the promotion of glycerinum (GLY) transportation and PUFA synthesis. Additional findings showed that the gene expression levels of leptin (LEP), adenosine 5′-monophosphate-activated protein kinase (AMPK) and phosphatidylinositol 3-kinase (PI3K) were upregulated (q < 0.05), whereas the gene expression levels of malonyl-CoA decarboxylase (MCD), sterol regulatory element-binding protein 1 (SREBF1), mammalian target of rapamycin (mTOR) and serine/threonine-protein kinase (AKT) were downregulated (q < 0.05), indicating that fat metabolism in the subcutaneous fat of yaks under ES was mainly regulated by AMPK signaling and mTOR and PI3K-AKT signaling were also involved. Energy consumption was inhibited in the subcutaneous fat itself. This study can provide a theoretical basis for the healthy breeding and genetic breeding of yaks.