Splanchnic metabolism of dairy cows during the transition from late gestation through early lactation

Graduate Student Literature Review: Exploring choline's important roles as a nutrient for transition dairy cows

In late gestation and in the first weeks postpartum, lipid droplets accumulate in the hepatic tissue resulting in approximately 40% to 50% of the dairy cows developing hepatic lipidosis in the first weeks of lactation. Elevated concentrations of triacylglycerol in the hepatic tissue are associated with increased risk of peripartum diseases and impaired productive performance. Cows with hepatic lipidosis need to dispose the excess of hepatic triacylglycerol, but this is a slow process in the bovine liver and relies on primary mechanisms such as complete oxidation and ketogenesis because of the limited export of triacylglycerols as lipoproteins. Choline is a lipotropic compound because, among other functions, it facilitates the export of lipids from the liver. Supplementing choline as rumen-protected choline (RPC) to diets of feed-restricted dairy cows reduces the degree of triacylglycerol infiltration into the hepatic parenchyma in part by enhancing export of triacylglycerol as nascent lipoprotein. The reduced accumulation of triacylglycerol in hepatic tissue in feed-restricted cows fed RPC might affect secondary pathways involved in hepatic disposal of fatty acids such as increased cellular autophagy and lipophagy and minimize endoplasmic reticulum stress response and hepatocyte inflammation. Collectively, these effects on secondary pathways might further reduce the severity of hepatic lipidosis in cows. One of the benefits of supplementing RPC is improved fat digestibility, perhaps because choline, through phosphatidylcholines, facilitates lipid transport within the enterocyte by increasing the synthesis of chylomicrons. Finally, when supplemented during the transition period, RPC improves productive performance of cows, irrespective of their body condition, that extends well beyond the period of supplementation. This review summarizes the current understanding of hepatic lipidosis in early lactation, recapitulates the absorption, transport and metabolism of choline, and discusses its role on hepatic metabolism and gastrointestinal functions, which collectively results in improved performance in dairy cows.

Metabolism and Nutrition of L-Glutamate and L-Glutamine in Ruminants

Although both L-glutamate (Glu) and L-glutamine (Gln) have long been considered nutritionally nonessential in ruminants, these two amino acids have enormous nutritional and physiological importance. Results of recent studies revealed that extracellular Gln is extensively degraded by ruminal microbes, but extracellular Glu undergoes little catabolism by these cells due to the near absence of its uptake. Ruminal bacteria hydrolyze Gln to Glu plus ammonia and, intracellularly, use both amino acids for protein synthesis. Microbial proteins and dietary Glu enter the small intestine in ruminants. Both Glu and Gln are the major metabolic fuels and building blocks of proteins, as well as substrates for the syntheses of glutathione and amino acids (alanine, ornithine, citrulline, arginine, proline, and aspartate) in the intestinal mucosa. In addition, Gln and aspartate are essential for purine and pyrimidine syntheses, whereas arginine and proline are necessary for the production of nitric oxide (a major vasodilator) and collagen (the most abundant protein in the body), respectively. Under normal feeding conditions, all diet- and rumen-derived Glu and Gln are extensively utilized by the small intestine and do not enter the portal circulation. Thus, de novo synthesis (e.g., from branched-chain amino acids and α-ketoglutarate) plays a crucial role in the homeostasis of Glu and Gln in the whole body but may be insufficient for maximal growth performance, production (e.g., lactation and pregnancy), and optimal health (particularly intestinal health) in ruminants. This applies to all types of feeding systems used around the world (e.g., rearing on a milk replacer before weaning, pasture-based production, and total mixed rations). Dietary supplementation with the appropriate doses of Glu or Gln [e.g., 0.5 or 1 g/kg body weight (BW)/day, respectively] can safely improve the digestive, endocrine, and reproduction functions of ruminants to enhance their productivity. Both Glu and Gln are truly functional amino acids in the nutrition of ruminants and hold great promise for improving their health and productivity.

Variation in protein metabolism biomarkers during the transition period and associations with health, colostrum quality, reproduction, and milk production traits in Holstein cows

The aims of this study were to assess (1) the variation of protein metabolism biomarkers and factors affecting them during the transition period, (2) the association of each biomarker with skeletal muscle reserves and their changes, and (3) the association of these biomarkers with postpartum health, colostrum quality, reproduction, and milk production. For this purpose, 238 multiparous Holstein cows from 6 herds were used in a prospective cohort study. Plasma concentrations of 3-methylhistidine (3-MH) and 1-methylhistidine (1-MH) and serum concentrations of total protein (TP), albumin (ALB), urea nitrogen (BUN), and creatinine (SCR) were determined for each cow at -21, -7, 7, 21, and 28 d relative to calving. Clinical diseases were recorded during the first 28 d postcalving, and presence of subclinical ketosis (scKET) was investigated at 7 and 21 d. Colostrum quality was estimated by Brix refractometry. Reproduction data by 150 d in milk (DIM) and milk production records were also available. Linear mixed models including the fixed effects of time point, herd, parity, body condition score (-21 d), duration of dry period and postparturient diseases were fitted to assess the variation in each biomarker's concentration. The association between the biomarkers' concentration during the prepartum period with the odds for each postparturient disease and for a combined trait (CD_1-28), defined as the presence of at least one clinical condition during the first 28 d after calving, were assessed with separate binary logistic models for time points -21 d and -7 d. The relationship of each biomarker's concentration with longissimus dorsi thickness (LDT) and the changes in LDT (ΔLDT) was assessed with pairwise correlations. Separate general linear models were used to assess the association of each biomarker with colostrum Brix values and milk production traits. Finally, the associated hazard for first artificial insemination (AI) and for pregnancy by 150 DIM (PREG_150DIM) was assessed with Cox proportional hazard models, whereas odds for pregnancy to the first AI (PREG_1stAI) were assessed with binary logistic models. The level of 3-MH was affected mainly by herd, time points, and their interaction. Higher 3-MH was associated with increased odds for metritis and CD_1-28, increased hazard for PREG_150 DIM and with increased milk production. 1-Methylhistidine was affected mainly by herd, scKET and occurrence of displaced abomasum. Higher 1-MH was associated with better colostrum quality, increased odds for scKET, increased hazard for first AI by 150 DIM and with decreased milk production. Both 3-MH and 1-MH were weakly to moderately negatively correlated with LDT and moderately to strongly negatively correlated with ΔLDT at the corresponding time periods. Additionally, higher TP was associated with increased odds for metritis and CD_1-28 and increased milk production, while higher ALB was associated with increased odds for scKET and increased milk production. Moreover, higher BUN was associated with decreased odds for scKET, increased odds for PREG_1stAI and increased milk production. Higher SCR was associated with decreased odds for retained fetal membranes, metritis, and CD_1-28. Periparturient protein metabolism is significantly associated with postpartum health, colostrum quality, reproduction, and milk production; mechanisms involved require further investigation.

Hepatic mitochondrial bioenergetics and metabolism across lactation and in response to heat stress in dairy cows

Lactation is energetically demanding for the dairy cow. Numerous morphological and metabolic changes orchestrated across different tissues in the body partition nutrients for milk synthesis. The liver is a key organ coordinating modifications in metabolism that increase substrate availability for the mammary gland. Impaired capacity to make the needed physiological adjustments for lactation, such as occurs with heat stress, can result in metabolic disease and poor lactation performance. At the cellular level, increases in mitochondrial density and bioenergetic and biosynthetic capacity are critical adaptations for successful lactation, providing energy and substrates for milk synthesis. Mitochondria are also involved in coordinating adaptation to a variety of stressors by providing the metabolic foundation to enlist a stress response. Heat stress can damage mitochondrial structures and impair mitochondrial function, with implications for pathogenesis and production. This systematic review focuses on the hepatic mitochondrial adaptations to lactation and the mitochondrial responses to heat stress. Future research directions are also discussed that may lead to improvements in managing the metabolic needs of the lactating cow and diminishing the adverse production and health consequences from environmental stress.

Evaluation of hepatic AMPK, mTORC1, and autophagy-lysosomal pathway in cows with mild or moderate fatty liver

The aim of the present study was to investigate the activity of AMPK and mTORC1 as well as TFEB transcriptional activity and autophagy-lysosomal function in the liver of dairy cows with mild fatty liver (FL) and cows with moderate FL. Liver and blood samples were collected from healthy dairy cows (n = 10; hepatic triglyceride content <1% wet weight) and cows with mild FL (n = 10; 1% ≤ hepatic triglyceride content < 5% wet weight) or moderate FL (n = 10; 5% ≤ hepatic triglyceride content < 10% wet weight) that had a similar number of lactations (median = 3, range = 2-4) and days in milk (median = 6 d, range = 3-9). Blood parameters were determined using a Hitachi 3130 autoanalyzer with commercially available kits. Protein and mRNA abundances were determined using western blotting and quantitative real-time PCR, respectively. Activities of calcineurin and β-N-acetylglucosaminidase were measured with commercial assay kits. Data were analyzed using one-way ANOVA with subsequent Bonferroni correction. Blood concentrations of glucose were lower in moderate FL cows (3.03 ± 0.21 mM) than in healthy (3.71 ± 0.14 mM) and mild FL cows (3.76 ± 0.14 mM). Blood concentrations of β-hydroxybutyrate (BHB, 1.37 ± 0.15 mM in mild FL, 1.88 ± 0.17 mM in moderate FL) and free fatty acids (FFA, 0.69 ± 0.05 mM in mild FL, 0.96 ± 0.09 mM in moderate FL) were greater in FL cows than in healthy cows (BHB, 0.76 ± 0.12 mM; FFA, 0.42 ± 0.04 mM). Compared with healthy cows, phosphorylation of AMPK was greater and phosphorylation of its downstream target acetyl-CoA carboxylase 1 was lower in cows with mild and moderate FL. Phosphorylation of mTOR was lower in cows with mild FL compared with healthy cows. In cows with moderate FL, phosphorylation of mTOR and its downstream effectors was greater than in healthy cows and cows with mild FL. The mRNA abundance of TFEB was downregulated in cows with moderate FL compared with healthy cows and mild FL cows. In mild FL cows, the mRNA and protein abundances of TFEB were greater than in healthy cows. Compared with healthy cows, the mRNA abundances of autophagy markers sequestosome-1 and microtubule-associated protein 1 light chain 3-II, and the protein and mRNA abundances of lysosome-associated membrane protein 1 and cathepsin D were increased in mild FL cows but decreased in moderate FL cows. Compared with healthy cows, the mRNA abundance of mucolipin 1 and activities of β-N-acetylglucosaminidase and calcineurin were higher in cows with mild FL but lower in cows with moderate FL. These data demonstrate that hepatic AMPK signaling pathway, TFEB transcriptional activity, and autophagy-lysosomal function are increased in dairy cows with mild FL; the hepatic mTORC1 signaling pathway is inhibited in mild FL cows but activated in moderate FL cows; and activities of AMPK and TFEB as well as autophagy-lysosomal function are impaired in moderate FL cows.

The Protective Role of Vitamin E against Oxidative Stress and Immunosuppression Induced by Non-Esterified Fatty Acids in Bovine Peripheral Blood Leukocytes

High levels of non-esterified fatty acids (NEFAs) during the transition period lead to increased oxidative stress and immunosuppression in cows. Feeding them a vitamin-E-supplemented diet reduces reactive oxygen species (ROS) levels in the blood and diminishes immunosuppression in the transition period. However, whether the restoration of immune cell function occurs through the direct action of vitamin E in cells is still a topic that requires further discussion. Therefore, in this experiment, we aimed to investigate the effect of NEFAs on peripheral blood leukocytes (PBLs) and whether vitamin E mitigates the impact of NEFAs. We employed three groups: (1) blank, (2) NEFA only, and (3) pre-culturing with vitamin E before NEFA treatment (VENEFA). In peripheral blood mononuclear cells (PBMCs), there were no differences in vitamin E content among the three groups. However, in the vitamin E pre-treatment group, the vitamin E levels of polymorphonuclear neutrophils (PMNs) were significantly higher than those in the other two groups. NEFA levels increased malondialdehyde (MDA) levels in PBMCs, but pre-treatment with vitamin E reduced accumulation of MDA levels. Regarding the expression of proinflammatory genes, NEFAs increased the expression of interleukin-1β in PBMCs and colony-stimulating factor 2 in PMNs. Vitamin E pre-treatment restored the increase in interleukin-1β levels caused by NEFAs in PBMCs. None of the groups affected the phagocytosis of PMNs. Few studies have confirmed that NEFAs cause oxidative stress in bovine PBLs. In summary, this study found that NEFAs induce oxidative stress in PBLs and alter the expression of inflammation-related genes; meanwhile, vitamin E can reduce some of the effects caused by NEFAs. This result may suggest that vitamin E can assist bovine PBLs in resisting the immune suppression caused by an NEB during the transition period.

Disrupted one-carbon metabolism in heifers negatively affects their health and physiology

The objective of this study was to determine the dose-dependent response of one-carbon metabolite (OCM: methionine, choline, folate, and vitamin B12) supplementation on heifer dry matter intake on fixed gain, organ mass, hematology, cytokine concentration, pancreatic and jejunal enzyme activity, and muscle hydrogen peroxide production. Angus heifers (n = 30; body weight [BW] = 392.6 ± 12.6 kg) were individually fed and assigned to one of five treatments: 0XNEG: total mixed ration (TMR) and saline injections at days 0 and 7 of the estrous cycle, 0XPOS: TMR, rumen-protected methionine (MET) fed at 0.08% of the diet dry matter, rumen-protected choline (CHOL) fed at 60 g/d, and saline injections at days 0 and 7, 0.5X: TMR, MET, CHOL, 5-mg B12, and 80-mg folate injections at days 0 and 7, 1X: TMR, MET CHOL, 10-mg vitamin B12, and 160-mg folate at days 0 and 7, and 2X: TMR, MET, CHOL, 20-mg vitamin B12, and 320-mg folate at days 0 and 7. All heifers were estrus synchronized but not bred, and blood samples were collected on days 0, 7, and at slaughter (day 14) during which tissues were collected. By design, heifer ADG did not differ (P = 0.96). Spleen weight and uterine weight were affected cubically (P = 0.03) decreasing from 0XPOS to 0.5X. Ovarian weight decreased linearly (P < 0.01) with increasing folate and B12 injection. Hemoglobin and hematocrit percentage were decreased (P < 0.01) in the 0.5X treatment compared with all other treatments. Plasma glucose, histotroph protein, and pancreatic α-amylase were decreased (P ≤ 0.04) in the 0.5X treatment. Heifers on the 2X treatment had greater pancreatic α-amylase compared with 0XNEG and 0.5X treatment. Interleukin-6 in plasma tended (P = 0.08) to be greater in the 0XPOS heifers compared with all other treatments. Lastly, 0XPOS-treated heifers had reduced (P ≤ 0.07) hydrogen peroxide production in muscle compared with 0XNEG heifers. These data imply that while certain doses of OCM do not improve whole animal physiology, OCM supplementation doses that disrupt one-carbon metabolism, such as that of the 0.5X treatment, can induce a negative systemic response that results in negative effects in both the dam and the conceptus during early gestation. Therefore, it is necessary to simultaneously establish an optimal OCM dose that increases circulating concentrations for use by the dam and the conceptus, while avoiding potential negative side effects of a disruptive OCM, to evaluate the long-term impacts of OCM supplementation of offspring programming.

Effect of a Dietary Essential Oil Blend in Dairy Cows during the Dry and Transition Period on Blood and Metabolic Parameters of Dams and Their Calves

Cows face severe challenges of immunosuppression and negative energy balance during transition periods. The current study was designed to investigate the effects of essential oil blend supplementation in dairy cow's ration during dry periods on the health of the cow and calf. In the current study, 45 dry Holstein dairy cows were divided into three groups, each consisting of 15 animals. The control group was without any supplementation; the positive control group was only injected with 0.2 mg/kg levamisole (intramuscular) at 2 months before parturition and 1 month before parturition; and the treatment group was supplemented with 3 g/day for each cow essential oil blend mixed in total mixed ration (TMR). A mixed vaccine against E. coli, Rotavirus, and Coronavirus was administered to all cows before 42 days and after 21 days of calving. The day of the calving of the animal was accepted as day 0. Blood samples were collected from the coccygeal vein of all cows at -60, -45, -30, -15, -7, 0, 1 and 2 days, and the colostrum samples were taken on days 0, 1, and 2. Blood samples were also collected from the jugular vein (V. Jugularis) of the newborn calves on days 0, 1, and 2. The results of the hematological parameters revealed no difference in the total red blood cell count, hemoglobin amount, hematocrit, MCV, MCH, MCHC, RDW, PLT, MPV, and PCT values in both prenatal and postnatal blood of the cows (p > 0.05). In terms of immunological parameters, the total IgG level was significantly higher in the experimental group on the 7th day before birth compared to the other two groups, while the total leukocyte count, lymphocyte count, monocyte count and granulocyte counts were found to be lower after birth (p < 0005). Blood NEFA and BHBA levels were also lower in the experimental group compared to the other two groups (p < 0.005), and the blood glucose level was not different (p > 0.05). In calves, no difference was found between the groups in any of the parameters examined (p > 0.05). It is concluded that the dietary addition of an essential oil blend during the transition period enhanced the immune status and energy metabolism of cows without any effect on the health status of newborn calves.

Nuciferine protects bovine hepatocytes against free fatty acid-induced oxidative damage by activating the transcription factor EB/peroxisome proliferator-activated receptor γ coactivator 1 alpha pathway

Excessive free fatty acid (FFA) oxidation and related metabolism are the major cause of oxidative stress and liver injury in dairy cows during the early postpartum period. In nonruminants, activation of transcription factor EB (TFEB) can improve cell damage and reduce the overproduction of mitochondrial reactive oxygen species. As a downstream target of TFEB, peroxisome proliferator-activated receptor γ coactivator 1 α (PGC-1α, gene name PPARGC1A) is a critical regulator of oxidative metabolism. Nuciferine (Nuc), a major bioactive compound isolated from the lotus leaf, has been reported to possess hepatoprotective activity. Therefore, the objective of this study was to investigate whether Nuc could protect bovine hepatocytes from FFA-induced lipotoxicity and the underlying mechanisms. A mixture of FFA was diluted in RPMI-1640 basic medium containing 2% low fatty acid bovine serum albumin to treat hepatocytes. Bovine hepatocytes were isolated from newborn calves and treated with various concentrations of FFA mixture (0, 0.3, 0.6, or 1.2 mM) or Nuc (0, 25, 50, or 100 μM), as well as co-treated with 1.2 mM FFA and different concentrations of Nuc. For the experiments of gene silencing, bovine hepatocytes were transfected with small interfering RNA targeted against TFEB or PPARGC1A for 36 h followed by treatment with 1.2 mM FFA for 12 h in presence or absence of 100 μΜ Nuc. The results revealed that FFA treatment decreased protein abundance of nuclear TFEB, cytosolic TFEB, total (t)-TFEB, lysosome-associated membrane protein 1 (LAMP1) and PGC-1α and mRNA abundance of LAMP1, but increased phosphorylated (p)-TFEB. In addition, FFA treatment increased the content of malondialdehyde (MDA) and hydrogen peroxide (H2O2) and decreased the activities of catalase (CAT) and glutathione peroxidase (GSH-Px) in bovine hepatocytes. Moreover, FFA administration enhanced the activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactose dehydrogenase (LDH) in the medium of FFA-treated hepatocytes, but reduced the content of urea. In FFA-treated bovine hepatocytes, Nuc administration increased TFEB nuclear localization and the protein abundance of t-TFEB, LAMP1, and PGC-1α and mRNA abundance of LAMP1, decreased the contents of MDA and H2O2 and the protein abundance of p-TFEB, and enhanced the activities of CAT and GSH-Px in a dose-dependent manner. Consistently, Nuc administration reduced the activities of ALT, AST, and LDH and increased the content of urea in the medium of FFA-treated hepatocytes. Importantly, knockdown of TFEB reduced the protein abundance of p-TFEB, t-TFEB, LAMP1, and PGC-1α and mRNA abundance of LAMP1, and impeded the beneficial effects of Nuc on FFA-induced oxidative damage in bovine hepatocytes. In addition, PPARGC1A silencing did not alter Nuc-induced nuclear translocation of TFEB, increase of the protein abundance of t-TFEB, LAMP1, and PGC-1α and mRNA abundance of LAMP1, or decrease of the protein abundance of p-TFEB, whereas it partially reduced the beneficial effects of Nuc on FFA-caused oxidative injury. Taken together, Nuc exerts protective effects against FFA-induced oxidative damage in bovine hepatocytes through activation of the TFEB/PGC-1α signaling pathway.

Reproduction in the era of genomics and automation

Much progress has been made in the reproductive efficiency of lactating dairy cows across the USA in the past 20years. The standardisation of evaluation of reproductive efficiency, particularly with greater focus on metrics with lesser momentum and less lag-time such as 21-day pregnancy rates (21-day PR), and the recognition that subpar reproductive efficiency negatively impacted profitability were major drivers for the changes that resulted in such progress. Once it became evident that the genetic selection of cattle for milk yield regardless of fertility traits was associated with reduced fertility, geneticists raced to identify fertility traits that could be incorporated in genetic selection programs with the hopes of improving fertility of lactating cows. Concurrently, reproductive physiologists developed ovulation synchronisation protocols such that after sequential treatment with exogenous hormones, cows could be inseminated at fixed time and without detection of oestrus and still achieve acceptable pregnancy per service. These genetic and reproductive management innovations, concurrently with improved husbandry and nutrition of periparturient cows, quickly started to move reproductive efficiency of lactating dairy cows to an upward trend that continues today. Automation has been adopted in Israel and European countries for decades, but only recently have these automated systems been more widely adopted in the USA. The selection of dairy cattle based on genetic indexes that result in positive fertility traits (e.g. daughter pregnancy rate) is positively associated with follicular growth, resumption of ovarian cycles postpartum, body condition score and insulin-like growth factor 1 concentration postpartum, and intensity of oestrus. Collectively, these positive physiological characteristics result in improved reproductive performance. Through the use of automated monitoring devices (AMD), it is possible to identify cows that resume cyclicity sooner after calving and have more intense oestrus postpartum, which are generally cows that have a more successful periparturient period. Recent experiments have demonstrated that it may be possible to adopt targeted reproductive management, utilising ovulation synchronisation protocols for cows that do not have intense oestrus postpartum and relying more heavily on insemination at AMD-detected oestrus for cows that display an intense oestrus postpartum. This strategy is likely to result in tailored hormonal therapy that will be better accepted by the public, will increase the reliance on oestrus for insemination, will improve comfort and reduce labour by reducing the number of injections cows receive in a lactation, and will allow for faster decisions about cows that should not be eligible for insemination.

Effects of dietary starch and ruminally undegraded protein on glucogenic precursors in lactating dairy cows

Gluconeogenesis is a large contributor to the blood supply of glucose carbons. The impact of varying dietary starch and ruminally degraded protein (RDP) on glucose entry, and the contributions of propionate and lactate to total plasma glucose entry were evaluated. Six cannulated, lactating, Holstein cows were fed one of four treatment diets arranged as a 2 × 2 factorial within a 4 × 4 partially replicated Latin Square design: (1) 8% RDP (LRDP) and 16% starch (LSt), (2) LRDP and 30% starch (HSt), (3) 11% RDP (HRDP) and LSt, or (4) HRDP and HSt. On d 12 of each period, 2-[13C]-sodium propionate (0.15 g/h) was ruminally infused for 4 h; on d 13, 1,2-[13C2]-glucose (0.2 g/h) was infused into the jugular vein for 1 h followed by 1-[13C]-lactate (0.1 g/h) for 1 h. Blood samples were serially collected starting prior to the infusions, and analyzed for plasma glucose, propionate, and lactate isotopic ratios. A one-compartment, glucose carbon model with inputs from lactate, propionate, and other glucogenic precursors (Oth, primarily absorbed glucose plus amino acids) was fitted to the isotope ratio data to derive glucose entry rates and conversion of the precursors to glucose. Milk protein production additively increased when HSt and HRDP were fed (P = 0.05 and P = 0.02, respectively). Plasma glucose and propionate concentrations increased with HSt (P = 0.04 and P = 0.01, respectively) and LRDP (P = 0.02 and P < 0.01, respectively). Total glucose and Oth entry increased (P = 0.03 and P = 0.03, respectively) with HSt, indicating greater glucose absorption from the small intestine or conversion of amino acids to glucose in the liver. However, neither entry rate was affected by RDP. The lack of an RDP effect suggests the increase in microbial outflow in response to RDP did not significantly alter glucose precursor supplies. Entry rates of propionate and lactate carbon to glucose carbon were not affected by treatment suggesting that neither starch nor RDP significantly affected fermentation or lactate production. Derivation of absolute entry rates and contributions to glucose using isotopic tracers is complicated by single carbon removals in the pentose phosphate (PPP), tri-carboxylic acid (TCA), and gluconeogenic pathways, and label randomization with the PPP and TCA pathways. Multiple tracers must be used to avoid assumptions regarding the proportional entries. These results provide insights on glucose supply and contributors, and draw attention to significant label cycling when utilizing isotope techniques.

Effects of an Hourly Bolus Postruminal Infusion of Flaxseed Oil or Palm Oil on Circulating Fatty Acid Concentrations and Hepatic Expression of Pyruvate Carboxylase and Phosphoenolpyruvate Carboxykinase in Dairy Cattle

Palmitic (C16:0), α-linolenic acid (C18:3n-3 cis), and propionate regulate bovine pyruvate carboxylase (PC) and phosphoenolpyruvate carboxykinase (PCK1) expression in vitro. The objective of this experiment was to determine the impact of C16:0, C18:3n-3 cis, propionate, and acetate postruminal infusions on hepatic PC and PCK1 expression. We hypothesized that circulating fatty acids alter hepatic PC and PCK1 in lactating dairy cows. Acetate, propionate, palm oil, and flaxseed oil were supplied postruminally to lactating cows (n = 4) using two 4 × 4 Latin square studies. For Experiment 1, cows were infused on an hourly basis with either a bolus of propionate, acetate, or the combination of propionate and palm oil, or acetate and palm oil, and Experiment 2 was similar, but flaxseed oil replaced palm oil. Flaxseed infusions increased plasma concentration and the molar percent of C18:3n-3 cis and decreased C16:0 but did not affect PC or PCK1 expression. Palm infusions did not affect blood metabolites or the hepatic expression of PC or PCK1. The lack of responses to short-chain fatty acid infusions and changes in circulating long-chain fatty acids in mature cattle are not suitable models to study the effects of α-linolenic acid and propionate on bovine PC and PCK1 expression previously observed in vitro.

Changes in Uterine Metabolome Associated with Metritis Development and Cure in Lactating Holstein Cows

The objective of this study was to identify alterations in the vaginal discharge (VD) metabolome and potential biomarkers to predict metritis development and a cure in dairy cows. This prospective cohort study was conducted on two dairies located in CA and TX. Vaginal discharge was evaluated and collected using the Metricheck® device. Cows were examined for metritis at 4, 7, and 9 days in milk (DIM). Cows with a fetid, watery, and reddish-brown uterine discharge were classified as having metritis and randomized to receive ceftiofur (n = 10) or remain untreated (n = 7). A cure was defined as the absence of a fetid, watery, reddish-brown uterine discharge at 14 d after enrollment. Vaginal discharge samples were collected from 86 cows within 6 h after parturition, at 4 and 7 DIM, at metritis diagnosis, and at 4 and 7 days after metritis diagnosis. Cows with metritis (MET; n = 17) were paired with counterparts without metritis (HTH) of a similar DIM and parity (n = 34). The uterine metabolome was evaluated using untargeted gas chromatography time-of-flight mass spectrometry (GC-TOF-MS). Metabolomic data were analyzed using the MetaboAnalyst 5.0. Data were log-transformed and auto-scaled for normalization. Univariate analyses, including the fold-change, were performed to identify the metabolites linked to metritis development and its cure and principal component analysis and partial least squares discriminant analysis were performed to explain metabolite variance between animals developing or not developing metritis and being cured or not being cured of metritis. Comparing HTH with MET cows at calving, 12 metabolites were upregulated, and one was downregulated. At four and seven DIM, 51 and 74 metabolites, respectively, were altered between MET and HTH cows. After metritis development, three and five metabolites were upregulated in cows that were cured and in cows that received treatment and were cured, respectively. In all scenarios, the metabolites lignoceric, malic, and maleic acids, ornithine, and hypotaurine, which are associated with arginine/aminoacyl-tRNA biosynthesis and taurine/purine metabolism, were upregulated in HTH cows. Metritis was associated with changes in the uterine metabolome. Cows not being cured of metritis had changes in the uterus metabolome independent of receiving ceftiofur or remaining untreated. Metabolome analysis may be an important tool to understand the vaginal discharge changes during postpartum and the dynamics of metritis development and cures and help to identify biomarkers to predict metritis being cured.

Developmental Programming, Evolution, and Animal Welfare: A Case for Evolutionary Veterinary Science

The conditions animals experience during the early developmental stages of their lives can have critical ongoing effects on their future health, welfare, and proper development. In this paper we draw on evolutionary theory to improve our understanding of the processes of developmental programming, particularly Predictive Adaptive Responses (PAR) that serve to match offspring phenotype with predicted future environmental conditions. When these predictions fail, a mismatch occurs between offspring phenotype and the environment, which can have long-lasting health and welfare effects. Examples include metabolic diseases resulting from maternal nutrition and behavioral changes from maternal stress. An understanding of these processes and their evolutionary origins will help in identifying and providing appropriate developmental conditions to optimize offspring welfare. This serves as an example of the benefits of using evolutionary thinking within veterinary science and we suggest that in the same way that evolutionary medicine has helped our understanding of human health, the implementation of evolutionary veterinary science (EvoVetSci) could be a useful way forward for research in animal health and welfare.

Fatty acid challenge shifts cellular energy metabolism in a substrate-specific manner in primary bovine neonatal hepatocytes

Adipose tissue mobilization increases circulating fatty acid (FA) concentrations, leads to increased hepatic FA uptake, and influences hepatic metabolism. Our objective was to trace carbon flux through metabolic pathways in primary bovine neonatal hepatocytes challenged with FA, and to examine the effect of FA challenge on oxidative stress. Primary bovine neonatal hepatocytes were isolated from 4 Holstein bull calves and maintained for 24 h before treatment with either 0 or 1 mM FA cocktail. After 21 h, either [1-14C]C16:0 or [2-14C]sodium pyruvate was added to measure complete and incomplete oxidation and cellular glycogen. Cellular and media triglyceride (TG), and glucose and ß-hydroxybutyrate (BHB) export were quantified, as well as reactive oxygen species and cellular glutathione (GSH/GSSH). Fatty acid treatment increased cellular, but not media TG, and although complete oxidation of [1-14C]C16:0 was not affected by FA, BHB export was increased. Reactive oxygen species were increased with FA treatment and GSSH was marginally increased such that the ratio of GSH:GSSG was marginally decreased. Glucose export increased, and cellular glycogen marginally increased with FA treatment while [2-14C]sodium pyruvate oxidation was decreased. These data suggest that FA treatment shifts cellular energy metabolism in a substrate-specific manner, spares pyruvate carbon from oxidation, and stimulates glucose synthesis.

A combined pig model to determine the net absorption of volatile fatty acids in the large intestine under different levels of crude fiber

BACKGROUND

This study aimed to develop a combined model to quantify the net absorption of volatile fatty acids (VFA) in the large intestine (LI) of pigs.

METHODS

Fifteen female growing pigs (Duroc × Large White × Landrace) were ranked by body weight (30 ± 2.1 kg) on day 0 and assigned to one of three treatments, namely the basal diet containing different crude fiber (CF) levels (LCF: 3.0% CF, MCF: 4.5% CF, and HCF: 6.0% CF). The pigs were implanted with the terminal ileum fistula and the cannulation of the ileal mesenteric vein (IMV), portal vein (PV), and left femoral artery (LFA) from days 6 to 7. [13 C]-Labeled VFA and P-aminohippuric acid were constantly perfused into the terminal ileum fistula and the cannulation of the IMV (day 15), respectively. Blood samples were collected from the PV and the LFA during perfusion (5 h), and LI samples were collected.

RESULTS

The net flux of [12 C]-acetic acid in the PV was greater for LCF versus MCF (p = 0.045), but no difference was observed in the net flux of [12 C]-propionic acid (p = 0.505) and [12 C]-butyric acid (p = 0.35) in the PV among treatments. The deposition of [12 C]-acetic acid in the LI was greater for LCF versus MCF (p = 0.014), whereas the deposition of [12 C]-propionic acid (p = 0.007) and [12 C]-butyric acid (p = 0.037) in the LI was greater for LCF versus HCF.

CONCLUSIONS

In conclusion, this pig model was found conducive to study the net absorption of VFAs in the LI, and LCF had more net absorption of VFAs in the LI than MCF and HCF.

Influence of the concentrate inclusion level in a grass silage-based diet on hepatic transcriptomic profiles in Holstein-Friesian dairy cows in early lactation

Excessive negative energy balance in early lactation is linked to an increased disease risk but may be mitigated by appropriate nutrition. The liver plays central roles in both metabolism and immunity. Hepatic transcriptomic profiles were compared between 3 dietary groups in each of 40 multiparous and 18 primiparous Holstein-Friesian cows offered isonitrogenous grass silage-based diets with different proportions of concentrates: (1) low concentrate (LC, 30% concentrate + 70% grass silage); (2) medium concentrate (MC, 50% concentrate + 50% grass silage), or (3) high concentrate (HC, 70% concentrate + 30% grass silage). Liver biopsies were taken from all cows at around 14 d in milk for RNA sequencing, and blood metabolites were measured. The sequencing data were analyzed separately for primiparous and multiparous cows using CLC Genomics Workbench V21 (Qiagen Digital Insights), focusing on comparisons between HC and LC groups. More differentially expressed genes (DEG) were seen between the primiparous cows receiving HC versus LC diets than for multiparous cows (597 vs. 497), with only 73 in common, indicating differential dietary responses. Multiparous cows receiving the HC diet had significantly higher circulating glucose and insulin-like growth factor-1 and lower urea than those receiving the LC diet. In response to HC, only the multiparous cows produced more milk. In these animals, bioinformatic analysis indicated expression changes in genes regulating fatty acid metabolism and biosynthesis (e.g., ACACA, ELOVL6, FADS2), increased cholesterol biosynthesis (e.g., CYP7A1, FDPS, HMGCR), downregulation in hepatic AA synthesis (e.g., GPT, GCLC, PSPH, SHMT2), and decreased expression of acute phase proteins (e.g., HP, LBP, SAA2). The primiparous cows on the HC diet also downregulated genes controlling AA metabolism and synthesis (e.g., CTH, GCLC, GOT1, ODC1, SHMT2) but showed higher expression of genes indicative of inflammation (e.g., CCDC80, IL1B, S100A8) and fibrosis (e.g., LOX, LUM, PLOD2). This potentially adverse response to a HC diet in physically immature animals warrants further investigation.

Review: State of the knowledge on the importance of folates and cobalamin for dairy cow metabolism

Synthesis of B vitamins by the rumen microbiota is usually sufficient to avoid the appearance of clinical deficiency symptoms in dairy cows under normal feeding conditions. Nevertheless, it is now generally accepted that vitamin deficiency is much more than the appearance of major functional and morphological symptoms. Subclinical deficiency, which is present as soon as the supply is lower than the need, causes cellular metabolic changes leading to a loss of metabolic efficiency. Folates and cobalamin, two B vitamins, share close metabolic relationships. Folates act as co-substrates in one-carbon metabolism, providing one-carbon unit for DNA synthesis and de novo synthesis of methyl groups for the methylation cycle. Cobalamin acts as a coenzyme for reactions in the metabolism of amino acids, odd-numbered chain fatty acids including propionate and de novo synthesis of methyl groups. Both vitamins are involved in reactions to support lipid and protein metabolism, nucleotide synthesis, methylation reactions and possibly, maintenance of redox status. Over the last decades, several studies have reported the beneficial effects of folic acid and vitamin B12 supplements on lactation performance of dairy cows. These observations indicate that, even when cows are fed diets adequately balanced for energy and major nutrients, B-vitamin subclinical deficiency could be present. This condition reduces casein synthesis in the mammary gland and milk and milk component yields. Folic acid and vitamin B12 supplements, especially when given together, may alter energy partitioning in dairy cows during early and mid-lactation as indicated by increased milk, energy-corrected milk, or milk component yields without affecting DM intake and BW or even with reductions in BW or body condition loss. Folate and cobalamin subclinical deficiency interferes with efficiency of gluconeogenesis and fatty acid oxidation and possibly alters responses to oxidative conditions. The present review aims to describe the metabolic pathways affected by folate and cobalamin supply and the consequences of a suboptimal supply on metabolic efficiency. The state of knowledge on the estimation of folate and cobalamin supply is also briefly mentioned.

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.

Predicting Pregnancy Outcome in Dairy Cows: The Role of IGF-1 and Progesterone

The purpose of this study was to determine the link between insulin-like growth factor 1 (IGF-1), progesterone (PROG), non-esterified fatty acids (NEFAs), β-hydroxybutyrate (BHB), and glucose (GLU) and pregnancy probability after the first artificial insemination (AI) and during the first 100 days in milk (DIM), during the critical transition period. We determined levels of serum IGF-1, PROG, NEFA, BHB, and GLU in Holstein dairy cows via ELISA, using blood samples collected 7 days before parturition (DAP) until 21 days postparturition (DPP). The group was split into cows diagnosed pregnant at 100 DIM (PREG) and those that did not conceive at 100 and 150 DIM (NPREG). Serum IGF-1 and PROG median levels at 7 DAP were significantly higher in PREG vs. NPREG (p = 0.029), the only statistically significant differences across the subgroups. At 7 DAP, IGF-1 levels within the initial group showed a strong negative correlation with PROG (r = -0.693; p = 0.006), while for the PREG subgroup, the IGF-1 levels exhibited a very strong positive correlation with GLU (r = 0.860; p = 0.011) and NEFA (r = 0.872; p = 0.013). IGF-1 and PROG levels detected at 7 DAP may be useful to predict pregnancy at 100 DIM. The positive correlation of NEFA and GLU levels during the transition period demonstrates that the initial group is not in NEB; thus, the NEFA level was not a decisive factor for reproduction success.

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.

[The lipidosis of the liver of dairy cows: Part 1 - Role of insulin and the Growth Hormone-IGF-1 axis]

Lipidosis of the liver of dairy cows is a metabolic disease known since many years and is caused by an uptake of nonesterified fatty acids (NEFA) into the liver cells, limited metabolism of NEFA (oxidation and production of β-hydroxybutyrate), and resynthesis in relation to a low efflux as triglyceride (TG). The pathogenesis of lipidosis includes a) an augmented release of NEFA by mobilisation of adipose tissue, b) uptake of NEFA into the liver cells, c) metabolism of NEFA and d) re-synthesis of triglyceride and e) an efflux of TG as very low density lipoprotein (VLDL). The steps a-e are postpartum modified by hormones as an increase of growth hormone, a pronounced insulin resistance in combination with a decreased insulin and of IGF-1 concentrations. These hormonal changes are related to an uncoupling of the growth hormone-IGF-1-axis with enhanced lipolysis and consequences mentioned above. These alterations are associated with inflammation, oxidative and endoplasmatic stress. The metabolic and hormonal alterations are the result of the selection of dairy cows primarily for milk production without adequate food intake with the consequence of lipidosis, ketosis and further health risks (production diseases).

Lactation stages modulate the hematological, serum biochemical, and endocrinological profiles and oxidative stress markers in crossbred cows under tropical humid island ecosystem of Andaman and Nicobar Islands

The present study was designed to assess the interrelationship between hematological, serum biochemical, and endocrinological profiles and oxidative stress markers and lactational stages in crossbred (CB) dairy cows of Andaman and Nicobar Islands (ANI). Healthy (n = 6) CB cows (50-62.50% exotic inheritance; Holstein Friesian × Andaman local) of 4^th parity with age of 7-9 years and body weight of 350-400 kg were selected from Cattle Breeding Farm, ICAR-Central Island Agricultural Research Institute (ICAR-CIARI), Port Blair, ANI. These experimental cows were synchronized with Ovsynch protocol, and parturition was planned to happen in the month of May-June. Lactation was allowed for 305 days. Hematological profiles, serum biochemical profiles, oxidative stress markers and endocrinological profiles were measured at a 15-day interval from day 07 to 305 of lactation (after 6 days of colostrum). The lactation period was divided into first (day 07 to 90), second (day 91 to 180), and third (day 181 to 305) stage of lactation. Average daily milk yield (L) did not vary among the stages of lactations; however, first (8.56 ± 1.26) and second (9.79 ± 0.87) stages had higher milk yield compared to third (7.93 ± 0.79) stage of lactation. Hematological profiles did not vary among the stages of lactation; however, these values were within the range of bovine species at lactation. Serum glucose, triglyceride, total cholesterol, total protein, globulin, and blood urea nitrogen (BUN) increased (P < 0.05) and albumin and creatinine decreased (P < 0.05) gradually as lactation stages advanced. Activity of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) and concentration of calcium, phosphorous, and magnesium were nearly similar among the stages of lactation. Similarly, triiodothyronine (T3), and thyroxine (T4) increased and prolactin and cortisol decreased (P < 0.05) gradually as stages of lactation advanced. Total antioxidant capacity (TAC) increased and malondialdehyde (MDA) decreased (P < 0.05) as lactation stages advanced. The results of the present study indicated that the lactating CB cows suffered nutritional stress (deficiency of protein, carbohydrate, lipids, and minerals), physiological stress (higher cortisol), oxidative stress (higher MDA and deficiency of total antioxidant capacity), and hormonal imbalance (higher prolactin and cortisol and deficiency of thyroid hormones) during the early stages of lactation. Thus, the first and second stages are more stressful events compared to the third stage of lactation in the CB cows in ANI. Therefore, regular monitoring of blood components and accordingly suitable feeding strategies with balanced nutrients and minerals, supplementation of suitable antioxidants, and appropriate management practices need to be implemented to mitigate these stresses and to prevent metabolic disorders with maximum milk production during different stages of lactation in CB cows under humid tropical island ecosystem of Andaman and Nicobar Islands.

Ruminal tissue uptake of amino acids in Holstein cows when supply of nutrients within the rumen differs

Characterisation of amino acid (AA) use by the ruminal vein-drained viscera (RDV) has not been assessed in vivo in dairy cattle, and thus, the extent of ruminal AA use from arterial and postabsorptive blood supplies is unclear. Understanding the complete use of AA by the splanchnic bed may lead to alternative feeding programmes that maximise animal N efficiency. The objective of this work was to determine how different nutritional manipulations affect RDV net appearance and apparent affinity for arterial AA in lactating dairy cattle. Data from two arterio-venous (A-V) difference studies, that used a common set of multicatheterised lactating Holstein cows, assigned to different nutritional treatments, were used to assess ruminal metabolism. Study 1 consisted of three dietary treatments at calving [an alfalfa-glucogenic diet, a glucogenic diet (GLCG), or a ketogenic diet (KETO)] to investigate the effects of dietary nutrients and increasing intake postpartum on RDV metabolism of AA at -14, +4, +15, and +29 days relative to calving (DRTC). Study 2 consisted of two dietary levels of CP (17 or 13%) and three ruminal buffers (ammonia, butyrate, and control) to investigate the level of dietary CP and ruminal fermentation products on RDV metabolism of AA. Blood was collected at 9, 20, and 30 min after buffer administration. Regardless of dietary nutrients or fermentation products present in ruminal fluid, net RDV uptake was positive for most AA, excepting Asp, Cys, Glu, and Ser, which were consistently negative. The general positive net uptakes indicate that any AA potentially absorbed from the rumen were not adequate to meet apparent needs. Ruminal plasma flow and net RDV uptake of Trp, Ala, Gly, and Pro increased linearly with increased DRTC. Feeding KETO or GLCG diets increased ruminal plasma flow, and net RDV uptake of Thr and Gly. Feeding high CP diets increased ruminal uptake of Leu, Phe, and Val. The increased AA uptakes were partially driven by increased plasma flow, however, tissue affinity as reflected in clearance rates also increased or tended to for Met, Trp, Ala, Gly, Pro, and Tyr suggesting that changes in RDV uptake were regulated and not due solely to mass action. In conclusion, splanchnic tissue bed responses to dietary and washed rumen conditions were in part driven by changes in RDV nutrient demand and metabolic activity. The adaptive responses alter the fraction of absorbed AA utilised for non-productive purposes and thus the efficiency of conversion of those AA to product.

Complementary hepatic metabolomics and proteomics reveal the adaptive mechanisms of dairy cows to the transition period

The transition period from late pregnancy to early lactation is a vital time of the lifecycle of dairy cows due to the marked metabolic challenges. Besides, the liver is the pivot point of metabolism in cattle. Nevertheless, the hepatic physiological molecular adaptation during the transition period has not been elucidated, especially from the metabolomics and proteomics view. Therefore, the present study aims to investigate the hepatic metabolic alterations in transition cows by using integrative metabolomics and proteomics methods. Gas chromatography quadrupole-time-of-flight mass spectrometry-based metabolomics and data-independent acquisition-based quantitative proteomics methods were used to analyze liver tissues collected from 8 healthy multiparous Holstein dairy cows 21 d before and after calving. In total, 44 metabolites and 250 proteins were identified as differentially expressed from 233 metabolites and 3,539 proteins detected from the liver biopsies during the transition period. Complementary functional analysis of different metabolites and proteins indicated the upregulated gluconeogenesis, tricarboxylic acid cycles, AA degradation, fatty acid oxidation, AMP-activated protein kinase signaling pathway, peroxisome proliferator-activated receptor signaling pathway, and ribosome proteins in postpartum dairy cows. In terms of the metabolites and proteins, glucose-6-phosphate, fructose-6-phosphate, carnitine palmitoyltransferase 1A, and phosphoenolpyruvate carboxykinase played a significant role in these pathways. The upregulated oxidative status may be accompanied by the pathways mentioned above. In addition, the upregulated glucagon and insulin signaling pathways also indicated the significant requirement for glucose in postpartum dairy cows. These outcomes, from the view of global metabolites and proteins, may present a better comprehension of the biology of the transition period, which can be helpful in further developing nutritional regulation strategies targeting the liver to help cows overcome this metabolically challenging time.

Symposium review: Fueling appetite: Nutrient metabolism and the control of feed intake

Conceptual models developed over the past century describe 2 key constraints to feed intake (FI) of healthy animals: gut capacity and metabolic demand. Evidence that greater energy demands (e.g., greater milk production) drive a corresponding increase in caloric intake led to the dominant concept that animals "eat to energy requirements." Although this model provides reasonable initial estimates of FI, it lacks a proposed physiological basis for the control system, does not consider nutrient constraints beyond energy, and fails to explain differential energy intake responses to different fuels. To address these gaps, research has focused on mechanisms for sensing nutrient availability and providing feedback to hypothalamic centers that integrate signals to control feeding behavior. The elimination of FI response to certain nutrients by vagotomy suggests that peripheral tissues play a role in nutrient sensing. These findings and the central role of the liver in metabolic flux led to the development of the hepatic oxidation theory (HOT). According to the HOT, liver energy charge is the regulated variable that induces dietary intake changes and consequently affects whole-body energy balance. Evidence in support of HOT includes associations between hepatic energy charge and meal patterns, increased FI in response to phosphate trapping, and reduced FI in response to phosphate loading. In accordance with the HOT, infusion studies in dairy cattle have consistently demonstrated that providing fuels that either oxidize or stimulate oxidation in the liver decreases FI and energy intake to a greater extent than fuels that bypass the liver. Importantly, this holds true for glucose, which is readily oxidized by nerve cells, but is rarely taken up by the bovine liver. Although the brain integrates multiple signals including those related to gastric distention and illness, the HOT provides a physiological framework for understanding the dominant role the liver likely plays in sensing short-term energy status. Understanding this model provides insights into how to use or bypass the regulatory system to manage FI of animals.

Yeast-fermented cassava as a protein source in cattle feed: systematic review and meta-analysis

The present study evaluated the effect of the inclusion of cassava fermented with Saccharomyces cerevisiae yeasts on performance, feed intake, nutrient digestibility, rumen microorganisms and ruminal fermentation of cattle through a systematic review and meta-analysis. The effects of yeast-fermented cassava (YFC) in the diet of cattle were evaluated using the mean difference as a measure of the effect size, considering a confidence interval of 95%. Subgroup and meta-regression analysis were performed to investigate the origin of heterogeneity. The database included eight experiments. Three studies were related to dairy heifers, three related to dairy cow and the remaining two studies were associated to beef heifers. The inclusion of YFC in the bovine diet increased the dry matter intake %BW (P < 0.01) and nutrient digestibility (P < 0.05). We observed an increase in mean ruminal pH (P < 0.01), volatile fatty acid (P < 0.01) and propionic acid concentration (P < 0.01). There was a significant increase in the population of bacteria (P < 0.01) and fungi (P < 0.01), and a reduction in the protozoan count in the rumen fluid (P < 0.01) in the animals fed with YFC. Lactating cows fed YFC produced 1.02 kg/day more (P < 0.01) milk than non-supplemented cows. In addition, there was an increase of 7.4% in the fat (P = 0.03), 6.3% in the protein (P < 0.01) and 2.8% in lactose (P = 0.02) of milk of cows supplemented with YFC. The results of the present meta-analysis showed that the total or partial inclusion of YFC in cattle concentrate improves fermentation and rumen efficiency, dry matter intake, nutrient digestibility, milk yield, and milk composition.

Invited review: Muscle protein breakdown and its assessment in periparturient dairy cows

Mobilization of body reserves including fat, protein, and glycogen is necessary to overcome phases of negative nutrient balance typical for high-yielding dairy cows during the periparturient period. Skeletal muscle, the largest internal organ in mammals, plays a crucial role in maintaining metabolic homeostasis. However, unlike in liver and adipose tissue, the metabolic and regulatory role of skeletal muscle in the adaptation of dairy cows to the physiological needs of pregnancy and lactation has not been studied extensively. The functional integrity and quality of skeletal muscle are maintained through a constant turnover of protein, resulting from both protein breakdown and protein synthesis. Thus, muscle protein breakdown (MPB) and synthesis are intimately connected and tightly controlled to ensure proper protein homeostasis. Understanding the regulation of MPB, the catabolic component of muscle turnover, and its assessment are therefore important considerations to provide information about the timing and extent of tissue mobilization in periparturient dairy cows. Based on animal models and human studies, it is now evident that MPB occurs via the integration of 3 main systems: autophagy-lysosomal, calpain Ca²⁺-dependent cysteine proteases, and the ubiquitin-proteasome system. These 3 main systems are interconnected and do not work separately, and the regulation is complex. The ubiquitin-proteasomal system is the most well-known cellular proteolytic system and plays a fundamental role in muscle physiology. Complete degradation of a protein often requires a combination of the systems, depending on the physiological situation. Determination of MPB in dairy cows is technically challenging, resulting in a relative dearth of information. The methods for assessing MPB can be divided into either direct or indirect measurements, both having their strengths and limitations. Available information on the direct measures of MPB primarily comes from stable isotopic tracer methods and those of indirect measurements from assessing expression and activity measures of the components of the 3 MPB systems in muscle biopsy samples. Other indirect approaches (i.e., potential indicators of MPB), including ultrasound imaging and measuring metabolites from muscle degradation (i.e., 3-methylhistidine and creatinine), seem to be applicable methods and can provide useful information about the extent and timing of MPB. This review presents our current understanding, including methodological considerations, of the process of MPB in periparturient dairy cows.

Short-term feeding of defatted bovine colostrum mitigates inflammation in the gut via changes in metabolites and microbiota in a chicken animal model

BACKGROUND

Nondrug supplement strategies to improve gut health have largely focused on the effects of individual compounds to improve one aspect of gut homeostasis. However, there is no comprehensive assessment of the reproducible effects of oral, short-term, low-level colostrum supplementation on gut inflammation status that are specific to the ileum. Herein, a chicken animal model highly responsive to even mild gut inflammatory stimuli was employed to compare the outcomes of feeding a standard diet (CON) to those of CON supplemented with a centrifuge-defatted bovine colostrum (BC) or a nonfat dried milk (NFDM) control on the efficiency of nutrient use, ileal morphology, gut nitro-oxidative inflammation status, metabolites, and the composition of the microbiota.

RESULTS

A repeated design, iterative multiple regression model was developed to analyze how BC affected ileal digesta-associated anti-inflammatory metabolite abundance coincident with observed changes in the ileal microbiome, mitigation of epithelial inflammation, and ileal surface morphology. An improved whole body nutrient use efficiency in the BC group (v CON and NFDM) coincided with the observed increased ileum absorptive surface and reduced epithelial cell content of tyrosine-nitrated protein (NT, biomarker of nitro-oxidative inflammatory stress). Metabolome analysis revealed that anti-inflammatory metabolites were significantly greater in abundance in BC-fed animals. BC also had a beneficial BC impact on microbiota, particularly in promoting the presence of the bacterial types associated with eubiosis and the segmented filamentous bacteria, Candidatus Arthromitus.

CONCLUSION

The data suggest that an anti-inflammatory environment in the ileum was more evident in BC than in the other feeding groups and associated with an increased content of statistically definable groups of anti-inflammatory metabolites that appear to functionally link the observed interactions between the host's improved gut health with an observed increase in whole body nutrient use efficiency, beneficial changes in the microbiome and immunometabolism.

The mechanistic target of rapamycin complex 1 pathway involved in hepatic gluconeogenesis through peroxisome-proliferator-activated receptor γ coactivator-1α

Cattle can efficiently perform de novo generation of glucose through hepatic gluconeogenesis to meet post-weaning glucose demand. Substantial evidence points to cattle and non-ruminant animals being characterized by phylogenetic features in terms of their differing capacity for hepatic gluconeogenesis, a process that is highly efficient in cattle yet the underlying mechanism remains unclear. Here we used a variety of transcriptome data, as well as tissue and cell-based methods to uncover the mechanisms of high-efficiency hepatic gluconeogenesis in cattle. We showed that cattle can efficiently convert propionate into pyruvate, at least partly, via high expression of acyl-CoA synthetase short-chain family member 1 (ACSS1), propionyl-CoA carboxylase alpha chain (PCCA), methylmalonyl-CoA epimerase (MCEE), methylmalonyl-CoA mutase (MMUT), and succinate-CoA ligase (SUCLG2) genes in the liver (P < 0.01). Moreover, higher expression of the rate-limiting enzymes of gluconeogenesis, such as phosphoenolpyruvate carboxykinase (PCK) and fructose 1,6-bisphosphatase (FBP), ensures the efficient operation of hepatic gluconeogenesis in cattle (P < 0.01). Mechanistically, we found that cattle liver exhibits highly active mechanistic target of rapamycin complex 1 (mTORC1), and the expressions of PCCA, MMUT, SUCLG2, PCK, and FBP genes are regulated by the activation of mTORC1 (P < 0.001). Finally, our results showed that mTORC1 promotes hepatic gluconeogenesis in a peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) dependent manner. Collectively, our results not only revealed an important mechanism responsible for the quantitative differences in the efficiency of hepatic gluconeogenesis in cattle versus non-ruminant animals, but also established that mTORC1 is indeed involved in the regulation of hepatic gluconeogenesis through PGC-1α. These results provide a novel potential insight into promoting hepatic gluconeogenesis through activated mTORC1 in both ruminants and mammals.

Plasma Metabolomic Analysis Reveals the Relationship between Immune Function and Metabolic Changes in Holstein Peripartum Dairy Cows

Dairy cows undergo dynamic physiological changes from late gestation to early lactation, including metabolic changes and immune dysfunction. The aim of this study was to investigate the relationship between immune function and metabolic changes in peripartum dairy cows. Fifteen healthy Holstein dairy cows were enrolled 14 days prior to parturition, and plasma was collected on day −7, 0, 7, and 21 relative to calving. Plasma non-esterified fatty acids (NEFAs), glucose, β-hydroxybutyric acid (BHBA), immunoglobulin G (IgG), tumor necrosis factor alpha (TNF-α), and interleukin-2 levels were measured, and metabolic profiles were determined using ultra-high-performance liquid chromatography−quadrupole time-of-flight mass spectrometry. The data were analyzed using Tukey−Kramer adjustment for multiple comparisons, and multivariate and univariate statistical analyses were performed to screen for differential metabolites. The results showed that the concentrations of NEFAs, glucose, BHBA, and TNF-α in the plasma significantly increased and concentrations of IgG and interleukin-2 in plasma significantly decreased from −7 d to the calving day (p < 0.05). Additionally, the concentrations of glucose, IgG, and TNF-α significantly decreased from 0 to +7 d, and concentrations of NEFAs decreased significantly from +7 to +21 d (p < 0.05). The following six primary metabolic pathways were identified in all time point comparisons, and L-glutamate, linoleic acid, taurine, and L-tryptophan were involved in these major metabolic pathways. Correlation and pathway analyses indicated that a negative energy balance during the transition period adversely affects immune responses in cows, and L-tryptophan exerts immunomodulatory effects through the Trp-Kyn pathway, resulting in depletion of Trp and elevation of Kyn.

Residual feed intake in peripartal dairy cows is associated with differences in milk fat yield, ruminal bacteria, biopolymer hydrolyzing enzymes, and circulating biomarkers of immunometabolism

Residual feed intake (RFI) measures feed efficiency independent of milk production level, and is typically calculated using data past peak lactation. In the current study, we retrospectively classified multiparous Holstein cows (n = 320) from 5 of our published studies into most feed-efficient (M-eff) or least feed-efficient (L-eff) groups using performance data collected during the peripartal period. Objectives were to assess differences in profiles of plasma biomarkers of immunometabolism, relative abundance of key ruminal bacteria, and activities of digestive enzymes in ruminal digesta between M-eff and L-eff cows. Individual data from cows with ad libitum access to a total mixed ration from d -28 to d +28 relative to calving were used. A linear regression model including dry matter intake (DMI), energy-corrected milk (ECM), changes in body weight (BW), and metabolic BW was used to classify cows based on RFI divergence into L-eff (n = 158) and M-eff (n = 162). Plasma collected from the coccygeal vessel at various times around parturition (L-eff = 60 cows; M-eff = 47 cows) was used for analyses of 30 biomarkers of immunometabolism. Ruminal digesta collected via esophageal tube (L-eff = 19 cows; M-eff = 29 cows) was used for DNA extraction and assessment of relative abundance (%) of 17 major bacteria using real-time PCR, as well as activity of cellulase, amylase, xylanase, and protease. The UNIVARIATE procedure of SAS 9.4 (SAS Institute Inc.) was used for analyses of RFI coefficients. The MIXED procedure of SAS was used for repeated measures analysis of performance, milk yield and composition, plasma immunometabolic biomarkers, ruminal bacteria, and enzyme activities. The M-eff cows consumed less DMI during the peripartal period compared with L-eff cows. In the larger cohort of cows, despite greater overall BW for M-eff cows especially in the prepartum (788 vs. 764 kg), no difference in body condition score was detected due to RFI or the interaction of RFI × time. Milk fat content (4.14 vs. 3.75 ± 0.06%) and milk fat yield (1.75 vs. 1.62 ± 0.04 kg) were greater in M-eff cows. Although cumulative ECM yield did not differ due to RFI (1,138 vs. 1,091 ± 21 kg), an RFI × time interaction due to greater ECM yield was found in M-eff cows. Among plasma biomarkers studied, concentrations of nonesterified fatty acids, β-hydroxybutyrate, bilirubin, ceruloplasmin, haptoglobin, myeloperoxidase, and reactive oxygen metabolites were overall greater, and glucose, paraoxonase, and IL-6 were lower in M-eff compared with L-eff cows. Among bacteria studied, abundance of Ruminobacter amylophilus and Prevotella ruminicola were more than 2-fold greater in M-eff cows. Despite lower ruminal activity of amylase in M-eff cows in the prepartum, regardless of RFI, we observed a marked linear increase after calving in amylase, cellulase, and xylanase activities. Protease activity did not differ due to RFI, time, or RFI × time. Despite greater concentrations of biomarkers reflective of negative energy balance and inflammation, higher feed efficiency measured as RFI in peripartal dairy cows might be associated with shifts in ruminal bacteria and amylase enzyme activity. Further studies could help address such factors, including the roles of the liver and the mammary gland.

Alterations in the Milk Metabolome of Dairy Cows Supplemented with Different Levels of Calcium Propionate in Early Lactation

This study aimed to investigate the effects of dietary supplementation with different levels of calcium propionate on the lactation performance, blood energy metabolite parameters, and milk metabolites of dairy cows in early lactation. Thirty-two multiparous Holstein cows were randomly divided into 4 groups, which were orally drenched with 0, 200, 350, and 500 g/d calcium propionate per cow supplemented to a basal diet for 5 weeks from calving. The milk and blood of the dairy cows were sampled and measured every week. The milk samples from the last week were used for the metabolomic analysis via liquid chromatography–mass spectrometry (LC-MS). The results showed that the calcium propionate supplementation quadratically increased the dry matter intake, energy-corrected milk yield, and 4% fat-corrected milk yield; linearly reduced the milk protein and milk lactose concentrations; and quadratically decreased the somatic cell count in the milk. With the increase in calcium propionate, the serum glucose content showed a linear increase, while the serum insulin content showed a quadratic increase. The diets supplemented with calcium propionate quadratically decreased the β-hydroxybutyric acid and linearly decreased the non-esterified fatty acid content in the serum. The metabolomic analysis revealed that eighteen different metabolites were identified in the milk samples of the dairy cows supplemented with calcium propionate at 350 g/d, which decreased the abundance of genistein and uridine 5-monophosphate and increased the abundance of adenosine, uracil, protoporphyrin IX, and sphingomyelin (d 18:1/18:0) compared with the control group. The milk metabolic analysis indicated that the calcium propionate effectively improved the milk synthesis and alleviated the mobilization of adipose tissue and bone calcium. In summary, the calcium propionate could improve the lactation performance and energy status and promote the milk metabolic profile of dairy cows in early lactation. Calcium propionate (350 g/d) is a well-recommended supplement for dairy cows for alleviating negative energy balance and hypocalcemia in early lactation.

Estimation of Individual Glucose Reserves in High-Yielding Dairy Cows

Glucose plays a central role in numerous physiological processes in dairy cows related to immune defence and milk production. A lack of glucose impairs both objectives, although to different degrees. A method for the estimation of glucose balance (GB) in dairy cows was developed to assess glucose reserves in the intermediary metabolism. Digestive fluxes of glucogenic carbon were individually estimated via the Systool Web application based on data on body weight (BW), dry matter intake (DMI), and chemical analyses of feedstuffs. Fluxes of endogenous precursors glycerol, alanine and L-lactate and the glucose demand imposed by major glucose-consuming organs were deduced from BW, lactose yield and lactation stage. GB was calculated for 201 lactations (1 to 105 DIM) of 157 cows fed isoenergetic rations. Individual DMI, BW and milk yield were assessed on a daily basis. The results showed that the GB varied greatly between cows and lactation stages. In the first week of lactation, average daily GB reached levels close to zero (3.2 ± 13.5 mol C) and increased as lactation progressed. Most cows risk substantial shortages of glucose for maintenance during the first weeks of lactation. In face of the specific role of glucose for the functional capability of the immune function, the assessment of glucose reserves is a promising measure for the identification of cows at risk of impaired immunocompetence.

Hepatic triacylglycerol associations with production and health in dairy cows

The objectives were to evaluate the associations between hepatic triacylglycerol content and production, blood metabolites, incidence of diseases, reproduction, and survival in Holstein cows. Data were collected from 4 experiments including 329 cows in which hepatic tissue was sampled with a mean (± standard deviation) of 8.3 ± 1.5 d postpartum (6 to 11 d) and analyzed for triacylglycerol concentration. The mean (± standard deviation) concentration was 4.4 ± 2.8% on a wet basis and ranged from 0.4 to 16.1%. Intakes of dry matter (DM), energy balance, body weight (BW), body condition (BCS), productive performance, and incidence of diseases were evaluated for the first 105 d postpartum, whereas blood metabolites were assayed in the first 21 d postpartum. Reproductive performance and survival were monitored in the first 300 d postpartum. Mixed models were fitted to the data to investigate the linear and quadratic associations of hepatic triacylglycerol concentration with responses of interest. Increased concentration of hepatic triacylglycerol was associated with a quadratic increase in yields of milk, energy-corrected milk (ECM), and milk components. A change in hepatic triacylglycerol from 2.5 to 7.5% of the wet tissue was associated with an increase in yield of ECM of 1.8 kg/d, and with 0.2 kg more ECM per kg of DM intake. However, the increased efficiency was accompanied by decreases in DM intake, BCS, more exacerbated losses of BW, and a more negative body energy change. Increased concentration of hepatic triacylglycerol was associated with a quadratic increase in blood fatty acids and a linear increase in blood β-hydroxybutyrate concentrations, concurrent with linear decreases in concentrations of glucose and total Ca in blood. Moreover, a change in hepatic triacylglycerol from 2.5 to 7.5% was associated with linear increases in the relative risk of hyperketonemia by 2.5 times (15.2 vs. 37.5%), hypocalcemia by 1.7 times (30.3 vs. 52.4%), metritis by 2.1 times (12.5 vs. 25.7%), and diagnosis of multiple diseases postpartum by 2.4 times (8.7 vs. 21.1%). Survival in the herd by 300 d postpartum tended to decrease from 91.1 to 86.3% with an increase in hepatic triacylglycerol from 2.5 to 7.5% of the wet tissue, but no association was observed between hepatic triacylglycerol and measures of reproduction in the first 300 d postpartum. Concentrations of hepatic triacylglycerol in early lactation varied substantially, and increments resulted in quadratic association with productive performance, but at the expense of tissue reserves as those cows had increased tissue catabolism and risk of diseases that reduced survival.

Effects of higher plasma growth hormone levels on subclinical ketosis in postpartum Holstein cows

Ketosis is a major metabolic disorder that can lead to huge economic losses in postpartum dairy cows by influencing milk production and reproduction performance. Therefore, it is very important to understand the characteristics and significance of plasma GH levels and dynamic changes in postpartum dairy cows for finding pathogenesis of subclinical ketosis (SK). The present study aimed to determine the role of growth hormone (GH) from the onset of SK to the fifth week postpartum and to explain the variations in GH, and metabolic markers namely, β-hydroxybutyric acid (BHBA), non-esterified fatty acid (NEFA) and glucose (GLU) at early and later SK stages in postpartum Holstein cows. A 5-wk test and an intraday 12-h test were conducted in postpartum Holstein cows. Both tests were carried out every three hours from 10:00–22:00 for 7–14 days postpartum (12-h test: n = 16) to determine plasma concentrations of GH, BHBA, NEFA and GLU. The 5-wk test results showed that GH, BHBA and NEFA concentrations were significantly higher in the SK group during the five-weeks postpartum (p < 0.01); GLU concentration was significantly lower in the SK group (p < 0.01). Intraday 12-h test results revealed that the feeding time affected the plasma concentrations of GH, BHBA, NEFA and GLU. After 1-h of feeding time, GH concentrations decreased, while BHBA, NEFA and GLU concentrations increased. After 4-h of feeding time GH, BHBA and NEFA had the highest plasma concentrations, and GLU the lowest. In both experiments, GH was positively correlated with BHBA, NEFA, and negatively correlated with GLU. It can be suggested that GH has a potential role in development and aetiology of subclinical ketosis.

Calcium Propionate Supplementation Has Minor Effects on Major Ruminal Bacterial Community Composition of Early Lactation Dairy Cows

Calcium propionate is one kind of good source for preventing and treating hypocalcemia and ketosis for dairy cows in early lactation. However, little is known about the effects of different feeding levels of calcium propionate on the ruminal bacterial community of early lactation dairy cows. This study aimed to explore the effects of different calcium propionate feeding levels on the ruminal fermentation and bacterial community composition of early lactation dairy cows. Twenty-four multiparous cows were randomly allocated into control (CON), low calcium propionate (LCaP), medium calcium propionate (MCaP), and high calcium propionate (HCaP) groups with six cows per group after calving. The CON group cows were fed the normal total mixed ration (TMR), and the cows of the LCaP, MCaP, and HCaP groups were fed TMR supplemented with 200, 350, and 500 g/day calcium propionate for 35 days after calving, respectively. The rumen fermentation parameters were measured every week, and the ruminal bacterial community composition of the last week was analyzed by 16S rRNA gene sequencing. Under the same diet, the rumen pH showed no difference among the four groups, but the content of microbial crude protein (MCP) and ammonia nitrogen quadratically decreased and linearly increased with calcium propionate supplementation, respectively. The feeding of calcium propionate linearly increased the concentrations of total volatile fatty acid (VFA), acetate, propionate, butyrate, iso-valerate, and valerate in the rumen. In all the treatment groups, Bacteroidetes, Firmicutes, and Proteobacteria were the dominant phyla, and Prevotella_1 and Succiniclasticum were the dominant genera in the rumen. Compared with the CON group, the addition of calcium propionate to the early lactation dairy cows quadratically improved the alpha diversity index of Chao1 estimator and observed species, but had little effect on the relative abundance of the major bacterial at phyla and genera level. These results suggested different levels of calcium propionate supplementation improved the rumen fermentation and the ruminal bacterial diversity but had little impact on the major ruminal bacterial community composition of dairy cows in early lactation.

Qualitative and Quantitative Changes in Total Lipid Concentration and Lipid Fractions in Liver Tissue of Periparturient German Holstein Dairy Cows of Two Age Groups

Fatty liver syndrome (FLS) is a common disease in high-producing dairy cows. Studies in humans suggest that the different hepatic lipid fractions play a role in this context. In dairy cows, little is known about the composition of fat stored in the liver, its periparturient dynamics, and the effect of cows' age. Therefore, our goal was to generate primary data in healthy cows to serve as reference values for future studies. Eight healthy German Holstein cows (2nd lactation, n = 3; ≥3rd lactation, n = 5) were examined 14 d antepartum and 7, 28, and 42 d postpartum. The examinations included clinical assessment, liver biopsy, blood sampling, and recording of milk yield. Total lipids (TL) in liver tissue were measured gravimetrically. The TL were separated into lipid fractions (triacylglycerol, TAG; phospholipids, PL; non-esterified fatty acids, NEFA; and cholesterol esters) using thin-layer chromatography, followed by gas chromatography for fatty acid determination. Concentrations of NEFA, ß-hydroxybutyrate, and cholesterol were analyzed in blood. Concentrations of TL, TAG, NEFA, and cholesterol esters in liver tissue and NEFA in blood increased in the periparturient period. The older cows had higher hepatic TL, TAG, and PL concentrations, higher relative hepatic concentrations of TAG in TL, higher NEFA concentrations in blood, a greater decrease in body condition, and higher milk yields between d 9 and 40 than the younger cows. We proposed that due to higher milk yield, older cows mobilized and deposited more fat in the liver, and the increase in hepatic TAG concentration was longer-lasting than in younger cows. Higher levels of structural lipids (PL) in older cows could be explained by higher demand for storage of TAG and cholesterol esters in lipid droplets or for the export of TAG via very-low-density lipoproteins. Results show that hepatic fat storage is a reversible process and does not necessarily cause clinical disease. Nevertheless, older cows have a more sustained and greater increase in hepatic TAG concentration, which may explain their increased risk of FLS. The results are limited in their extrapolation due to the small sample size and thereby possible selection bias but present a valuable basis for future studies.

Differences in the serum metabolome profile of dairy cows according to the BHB concentration revealed by proton nuclear magnetic resonance spectroscopy (1H-NMR)

The mobilization of body reserves during the transition from pregnancy to lactation might predispose dairy cows to develop metabolic disorders such as subclinical ketosis or hyperketonemia. These conditions are not easily identifiable and are frequently related to other diseases that cause economic loss. The aim of this study was to evaluate the serum metabolome differences according to the β-hydroxybutyrate (BHB) concentration. Forty-nine Holstein Friesian dairy cows were enrolled between 15 and 30 days in milk. According to their serum BHB concentration, the animals were divided into three groups: Group 0 (G0; 12 healthy animals; BHB ≤ 0.50 mmol/L); Group 1 (G1; 19 healthy animals; 0.51 ≤ BHB < 1.0 mmol/L); and Group 2 (G2; 18 hyperketonemic animals; BHB ≥ 1.0 mmol/L). Animal data and biochemical parameters were examined with one-way ANOVA, and metabolite significant differences were examined by t-tests. Fifty-seven metabolites were identified in the serum samples. Thirteen metabolites showed significant effects and seemed to be related to the mobilization of body reserves, lipids, amino acid and carbohydrate metabolism, and ruminal fermentation.

Longitudinal liver proteome profiling in dairy cows during the transition from gestation to lactation: Investigating metabolic adaptations and their interactions with fatty acids supplementation via repeated measurements ANOVA-simultaneous component analysis

Repeated measurements analysis of variance - simultaneous component analysis (ASCA) has been developed to handle complex longitudinal omics datasets and combine novel information with existing data. Herein, we aimed at applying ASCA to 64 liver proteomes collected at 4-time points (day -21, +1, +28, and + 63 relative to parturition) from 16 Holstein cows treated from 9 wk. antepartum to 9 wk. postpartum (PP) with coconut oil (CTRL) or a mixture of essential fatty acids (EFA) and conjugated linoleic acid (CLA) (EFA + CLA). The ASCA modeled 116, 43, and 97 differentially abundant proteins (DAP) during the transition to lactation, between CTRL and EFA + CLA, and their interaction, respectively. Time-dependent DAP were annotated to pathways related to the metabolism of carbohydrates, FA, and amino acid in the PP period. The DAP between FA and the interaction effect were annotated to the metabolism of xenobiotics by cytochrome P450, drug metabolism - cytochrome P450, retinol metabolism, and steroid hormone biosynthesis. Collectively, ASCA provided novel information on molecular markers of metabolic adaptations and their interactions with EFA + CLA supplementation. Bioinformatics analysis suggested that supplemental EFA + CLA amplified hepatic FA oxidation; cytochrome P450 was enriched to maintain metabolic homeostasis by oxidation/detoxification of endogenous compounds and xenobiotics. SIGNIFICANCE: This report is among the first ones applying repeated measurement analysis of variance-simultaneous component analysis (ASCA) to deal with longitudinal proteomics results. ASCA separately identified differentially abundant proteins (DAP) in 'transition time', 'between fatty acid treatments', and 'their interaction'. We first identified the molecular signature of hepatic metabolic adaptations during postpartum negative energy balance; the enriched pathways were well-known pathways related to mobilizing fatty acids (FA) and amino acids to support continuous energy production through fatty acid oxidation, TCA cycle, and gluconeogenesis. Some of the DAP were not previously reported in transition dairy cows. Secondly, we provide novel information on the mechanisms by which supplemented essential FA and conjugated linoleic acids interact with hepatic metabolism. In this regard, FA amplified hepatic detoxifying and oxidation capacity through ligand activation of nuclear receptors. Finally, we briefly compared the strengths and weaknesses of the ASCA model with PLS-DA and outlined why these methods are complementary.

Assessment of Metabolic Adaptations in Periparturient Dairy Cows Provided 3-Nitrooxypropanol and Varying Concentrate Proportions by Using the GreenFeed System for Indirect Calorimetry, Biochemical Blood Parameters and Ultrasonography of Adipose Tissues

Methanogenesis in ruminants contributes to both greenhouse gas emissions and feed energy losses whereby the latter becomes specifically important in energy-deficient periparturient cows. It was hypothesized that increased concentrate feed proportions (CFP) and feeding with the methane inhibitor 3-nitrooxypropanol (3-NOP), as well as their potential synergism, improve the energy status of peripartal cows. Periparturient dairy cows were fed low or high dietary CFP either tested without or combined with 3-NOP. The GreenFeed system was used to calculate the metabolic respiration quotient (RQmetabolic) and tissue energy retention (ERtissue) by methods of indirect calorimetry. The calorimetrically estimated ERtissue coincided with a conventionally calculated energy balance except for the antepartal period. Neither CFP nor 3-NOP affected the ultrasonographically assessed lipomobilization in adipose depots. In the group fed 3-NOP and a high concentrate feed proportion, the RQmetabolic significantly rose over the course of the experiment and the ERtissue was also increased. Serum non-esterified fatty acid concentrations were lower in the 3-NOP groups albeit ß-hydroxybutyrate (BHB) remained unaffected. Higher CFP reduced BHB and increased blood glucose levels. In conclusion, 3-NOP and high CFP improved the energy budget of the cows in an interactive manner, which was, however, not apparent in all of the examined parameters. The application of the GreenFeed system for indirect calorimetry is a promising approach, which needs further validation in the future.

The Role of Tea Tree Oil in Alleviating Palmitic Acid-Induced Lipid Accumulation in Bovine Hepatocytes

Tea tree oil (TTO) plays an important role in lipid metabolism, alleviating the inflammatory responses. Fatty liver is associated with lipid accumulation in hepatocytes, leading to inflammation. However, there is very limited information on the effects of TTO on lipid accumulation, and inflammation in bovine hepatocytes. This study aimed to evaluate whether TTO alleviates palmitic acid (PA)-induced lipid accumulation in bovine hepatocytes. Hepatocytes isolated from mid-lactating Holstein cows were pretreated with 100 μM PA for 72 h. Cells were either pretreated with PA alone (PA group) or with PA followed by 0.00625% TTO treatment for 12 h (PT group). Expression of fatty acid oxidant genes increased (P < 0.05) while fatty acid synthesis genes decreased (P < 0.05) in the PT group compared with the PA group. PA treatment resulted in increased (P < 0.05) expression of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), but these increases were less in the PT group (P < 0.05). Compared to the PA group, expression of phosphorylated (p)-p65 and p-inhibitor κBα (p-IκBα) was suppressed (P < 0.05) by TTO treatment. TTO treatment limited (P < 0.05) the increase in intracellular reactive oxygen species (ROS) and prevented (P < 0.05) a reduction in mitochondrial membrane potential observed in response to PA treatment. Expression of endoplasmic reticulum (ER) stress genes was reduced (P < 0.05) in the PT group compared with the PA group. Our results suggest that TTO treatment attenuates the effects of PA in hepatocytes, leading to fatty acid oxidation, decreased fatty acid synthesis, suppressed inflammatory response, and reduced ER stress. Taken together, the results of this study suggest that TTO treatment may be a promising therapeutic approach to imbalanced lipid homeostasis, inflammation and ER stress in dairy cows shortly before and after calving.

Metabolic and blood acid-base responses to prepartum dietary cation-anion difference and calcium content in transition dairy cows

Dairy cows commonly undergo negative Ca balance accompanied by hypocalcemia after parturition. A negative dietary cation-anion difference (DCAD) strategy has been used prepartum to improve periparturient Ca homeostasis. Our objective was to determine the influence of a negative DCAD diet with different amounts of dietary Ca on the blood acid-base balance, blood gases, and metabolic adaptation to lactation. Multiparous Holstein cows (n = 81) were blocked into 1 of 3 dietary treatments from 252 d of gestation until parturition: (1) positive DCAD diet and low Ca (CON; containing +6.0 mEq/100 g DM, 0.4% DM Ca); (2) negative DCAD diet and low Ca (ND; -24.0 mEq/100 g DM, 0.4% DM Ca); or (3) negative DCAD diet plus high Ca supplementation (NDCA; -24.1 mEq/100 g DM, 2.0% DM Ca). There were 28, 27, and 26 cows for CON, ND, and NDCA, respectively. Whole blood was sampled at 0, 24, 48, and 96 h after calving for immediate determination of blood acid-base status and blood gases. Serum samples collected at -21, -14, -7, -4, -2, -1, at calving, 1, 2, 4, 7, 14, 21, and 28 d relative to parturition were analyzed for metabolic components. Results indicated that cows fed ND or NDCA had lower blood pH at calving but greater pH at 24 h after calving compared with CON. Blood bicarbonate, base excess, and total CO₂ (tCO₂) concentrations of cows in ND and NDCA groups were less than those of cows in CON at calving but became greater from 24 to 96 h postpartum. The NDCA cows had lower blood bicarbonate, base excess, and tCO₂ at 48 h and greater partial pressure of oxygen after calving compared with ND. Cows fed ND or NDCA diets had lower serum glucose concentrations than CON cows before calving but no differences were observed postpartum. Serum concentrations of total protein and albumin were greater prepartum for cows in ND and NDCA groups than for those in CON. Postpartum serum urea N and albumin concentrations tended to be higher for ND and NDCA cows. Cows fed ND or NDCA diets had elevated serum total cholesterol concentration prepartum. During the postpartum period, triglycerides and NEFA of cows fed ND or NDCA diets tended to be lower than those of CON. Cows fed the NDCA diet had greater postpartum total cholesterol in serum and lower NEFA concentration at calving than ND. In conclusion, feeding a prepartum negative DCAD diet altered blood acid-base balance and induced metabolic acidosis at calving, and improved protein and lipid metabolism. Supplementation of high Ca in the negative DCAD diet prepartum was more favorable to metabolic adaptation to lactation in dairy cows than the negative DCAD diet with low Ca.

Oxidative Stress in Dairy Cows: Insights into the Mechanistic Mode of Actions and Mitigating Strategies

This review examines several molecular mechanisms underpinning oxidative stress in ruminants and their effects on blood and milk oxidative traits. We also investigate strategies to alleviate or repair oxidative damages by improving animal immune functions using novel feed additives. Microbial pathogenic cells, feeding management, and body condition score were some of the studied factors, inducing oxidative stress in ruminants. The predominance of Streptococcus spp. (24.22%), Acinetobacter spp. (21.37%), Romboutsia spp. (4.99%), Turicibacter spp., (2.64%), Stenotrophomonas spp. (2.33%), and Enterococcus spp. (1.86%) was found in the microbiome of mastitis cows with a decrease of d-mannose and increase of xanthine:guanine ratio when Streptococcus increased. Diversity of energy sources favoring the growth of Fusobacterium make it a keystone taxon contributing to metritis. Ruminal volatile fatty acids rose with high-concentrate diets that decreased the ruminal pH, causing a lysis of rumen microbes and release of endotoxins. Moreover, lipopolysaccharide (LPS) concentration, malondialdehyde (MDA), and superoxide dismutase (SOD) activities increased in high concentrate cows accompanied by a reduction of total antioxidant capacity (T-AOC), glutathione peroxidase (GPx), and catalase (CAT) activity. In addition, albumin and paraoxonase concentrations were inversely related to oxidative stress and contributed to the protection of low-density and high-density lipoproteins against lipid peroxidation, protein carbonyl, and lactoperoxidase. High concentrate diets increased the expression of MAPK pro-inflammatory genes and decreased the expression of antioxidant genes and proteins in mammary epithelial tissues. The expression levels of NrF2, NQO1, MT1E, UGT1A1, MGST3, and MT1A were downregulated, whereas NF-kB was upregulated with a high-grain or high concentrate diet. Amino-acids, vitamins, trace elements, and plant extracts have shown promising results through enhancing immune functions and repairing damaged cells exposed to oxidative stress. Further studies comparing the long-term effect of synthetic feed additives and natural plant additives on animal health and physiology remain to be investigated.