Technical note: Analysis of total lipid and triacylglycerol content in small liver biopsy samples in cattle

Short-term exposure of dairy cows to pyrrolizidine alkaloids from tansy ragwort (Jacobaea vulgaris Gaertn.): effects on organs and indicators of energy metabolism

Preserved feed from meadows contaminated with ragwort (Jacobaea vulgaris, Gaertn.) may expose livestock to pyrrolizidine alkaloids (PA). Dairy cows are considered to be very susceptible animals and a PA ingestion can lead to liver and further organ damages and even death. Due to the lack of data, the present study aimed to evaluate critical PA doses based on organ effects, with a special focus on liver lesions and on indicators of energy metabolism. Therefore, 16 dairy cows (n = 4 per group) were exposed to increasing PA doses (group: CONMolasses: <0.001 mg PA/kg body weight (BW)/day (d); PA1: 0.47 mg PA/kg BW/d; PA2: 0.95 mg PA/kg BW/d; PA3: 1.91 mg PA/kg BW/d) for 28 days. Constant dosing was ensured by a defined PA extract administered orally once daily. Histological examinations of the livers showed infiltration by immune cells, higher proportions of apoptotic cells and enlargement of hepatocyte nuclei in the highest exposed group. In addition, bile volume increased with PA dose, which may indicate a cholestasis. Despite the signs of incipient liver damage, liver lipid content and clinical chemical parameters related to energy metabolism, such as glucose, non-esterified fatty acids and βhydroxybutyrate, remained unaffected. Fat depot masses were also not significantly altered over time, suggesting that PA exposure did not induce a wasting syndrome. The liver showed slight microscopic changes already at a dosage of 0.95 mg PA/kg BW/d. However, the short-term metabolic indicators of energy status, lipolysis and ketogenesis, glucose, NEFA and BHB, as well as changes in fat depot, which serves as a longer-term indicator of lipolysis, remained unaffected in all treatment groups in the chosen scenario. These findings suggest that despite histopathological and clinical-chemical evidence of PA-associated hepatocellular lesions, liver function was not compromised.

Longitudinal characterization of the metabolome of dairy cows transitioning from one lactation to the next: Investigations in blood serum

The objective of this study was to characterize changes in the serum metabolome and various indicators of oxidative balance in dairy cows starting 2 wk before dry-off and continuing until wk 16 of lactation. Twelve Holstein dairy cows (body weight 745 ± 71 kg, body condition score 3.43 ± 0.66; mean ± SD) were housed in a tiestall barn from 10 wk before to 16 wk after parturition. Cows were dried off 6 wk before the expected calving date (mean dry period length = 42 d). From 8 wk before calving to 16 wk after calving, blood samples were taken weekly to study redox metabolism by determining antioxidant capacity, measured as the ferric-reducing ability of plasma, reactive oxidative metabolites, oxidative stress index, oxidative damage of lipids, measured as thiobarbituric acid reactive substances, and glutathione peroxidase activity. According to these results, dairy cows had the lowest serum antioxidant capacity and greater levels of oxidative stress during the dry-off period and the early postpartum period. For metabolomics, a subset of serum samples including wk -7 (before dry-off), -5 (after dry-off), -1, 1, 5, 10, and 15 relative to calving were used. A targeted metabolomics approach was performed using liquid chromatography and flow injection with electrospray ionization triple quadrupole mass spectrometry using the MxP Quant 500 kit (Biocrates Life Sciences AG). A total of 240 metabolites in serum were used in the final data analysis. Principal component analysis revealed a clear separation by days of sampling, indicating a remarkable shift in metabolic phenotype between the dry period and late and early lactation. Changes in many non-lipid metabolites associated with one-carbon metabolism, the tricarboxylic acid cycle, the urea cycle, and AA catabolism were observed in the study, with changes in AA serum concentrations likely related to factors such as energy and nitrogen balance, digestive efficiency, and changing diets. The study confirmed an extensive remodeling of the serum lipidome in peripartum dairy cows, highlighting the importance of changes in acylcarnitine (acylCN), phosphatidylcholines (PC), and triacylglycerols (TG), as they play a crucial role in lipid metabolism. Results showed that short-chain acylCN increased after dry-off and decreased thereafter, whereas lipid-derived acylCN increased around parturition, suggesting that more fatty acids could enter mitochondria. Phospholipids and sphingolipids in serum showed changes during lactation. In particular, concentrations of sphingomyelins, PC, and lysoPC decreased around calving but increased in mid- and late lactation. In contrast, concentrations of TG remained consistently low after parturition. The serum concentrations of bile acids fluctuated during the dry period and lactation, with glycocholic acid, cholic acid, glycodeoxycholic acid, and taurocholic acid showing the greatest concentrations. These changes are likely due to the interplay of diet, liver function, and the ability of the gut microbiota to convert primary to secondary bile acids. Overall, these descriptive results may aid in hypothesis generation and in the design and interpretation of future metabolite-based studies in dairy cows. Furthermore, they contribute to our understanding of the physiological ranges in serum metabolites relative to the lactation cycle of the dairy cow.

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.

Aspects of transition cow metabolomics-Part III: Alterations in the metabolome of liver and blood throughout the transition period in cows with different liver metabotypes

The liver plays a central role in the postpartum (PP) energy metabolism of the transition dairy cow; however, studies describing the liver metabolome during this period were lacking. The aim of the presented study was therefore to compare the alterations in the liver and blood metabolome of transition dairy cows. For this purpose, an on-farm trial with 80 German Holstein cows (mean lactation number: 3.9; range: 2-9) was performed, with thorough documentation of clinical traits and clinical chemistry, as well as production data. Liver biopsies and blood samples were collected at d 14 (mean: 12 d, range: 1-26 d) antepartum (AP), d 7 (7, 4-13) and 28 (28, 23-34; mean, earliest-latest) PP for targeted mass spectroscopy-based metabolomics analysis using the AbsoluteIDQ p180 kit (Biocrates Life Sciences). Statistical analysis was performed using multivariate (partial least squares discriminant analysis) as well as univariate methods (linear mixed model). Multivariate data analysis of the liver metabolome revealed 3 different metabotypes (A = medium, B = minor, C = large alterations in the liver metabolome profile between AP and PP). In metabotype C, an increase of almost all acylcarnitines, lysophosphatidylcholines (lysoPC), sphingomyelins, and some phosphatidylcholines (PC, mainly at 7 d PP) was observed after calving. In contrast to metabotype C, the clinical data of the metabotype B animals indicated a higher PP lipomobilization and occurrence of transition cow diseases. The liver metabolome profile of these animals most likely mirrors a failure of adaptation to the PP state. This strong occurrence of metabotypes was much less pronounced in the blood metabolome. Additionally, differences in metabolic patterns were observed across the transition period when comparing liver and blood matrices (e.g., in different biogenic amines, acylcarnitines and sphingolipids). In summary, the blood samples at 7 d PP showed lower acylcarnitines and PC, with minor alterations and a heterogeneous pattern in AA, biogenic amines, and sphingomyelins compared with 14 d AP. In contrast to 7 d PP, the blood samples at 28 PP revealed an increase in several AA, lysoPC, PC, and sphingomyelins in comparison to the AP state, irrespective of the metabotype. In the liver biopsies metabotype B differed from metabotype C animals ante partum by following metabolites: higher α aminoadipic acid, lower AA, serotonin, taurine, and symmetric dimethylarginine levels, lower or higher concentrations of certain acylcarnitines (higher: C2, C3, C5, C4:1; lower: C12:1, C14:1-OH, C16:2), and lower lysoPC (a C16:0, C18:0, C20:3, C20:4) and hexose levels. In blood samples, fewer differences were observed, with lower serotonin, acylcarnitine C16:2, lysoPC (a C16:0, C17:0, C18:0 and C18:1), PC aa C38:0, and PC ae C42:2. The results show that the use of only the blood metabolome to assess liver metabolism may be hampered by the fact that blood profiles are influenced by the metabolism of many organs, and metabolomics analysis from liver biopsies is a more suitable method to identify distinct metabotypes. Future studies should investigate the stability and reproducibility of the metabotype and phenotypes observed, and the possible predictive value of the metabolites already differing AP between metabotype B and C.

Aspects of transition cow metabolomics-Part II: Histomorphologic changes in the liver parenchyma throughout the transition period, in cows with different liver metabotypes and effects of a metaphylactic butaphosphan and cyanocobalamin treatment

The aims of this study were to evaluate histopathologic changes during the transition period, describe the histopathological features of the metabotypes identified in Part I (Schären et al., 2021b), and investigate effects of a metaphylactic treatment with butaphosphan and cyanocobalamin (BCC) on the liver parenchyma. Eighty German Holstein cows (mean 305-d production: 10,957 kg, range: 6,480-15,193 kg; mean lactation number: 3.9, range: 2-9) from a commercial dairy farm in Saxony, Germany, were enrolled in a randomized, prospective, triple-blinded study. Two groups received a treatment with BCC (5 or 10 mL/100 kg of body weight 10% butaphosphan and 0.005% cyanocobalamin, Catosal, Bayer Animal Health, n = 20 each) and one group a placebo treatment (NaCl 0.9%, n = 40). Liver biopsy specimens were collected 14 d antepartum (AP) and 7, 28, and 42 d postpartum (PP), routinely processed for histologic examination, and stained with hematoxylin and eosin, Sudan III, periodic acid-Schiff, and picrosirius red stains. The sections were assessed for fat and glycogen content and degenerative, inflammatory, fibrotic, and proliferative changes. The statistical analysis included the effects of the sampling day, the lactation number, the treatment, and the metabotype (A = medium, B = minor, C = large alterations in the liver metabolome profile between AP and PP status). There was mild to moderate fat infiltration in the liver of 37% of cows in the last 2 wk AP, and moderate to severe fat infiltration in 66% of cows in the first days PP. The degree of fat infiltration increased from 2 wk AP until the end of the first week PP, and then decreased until the end of the study period, at which time about 25% of cows had moderate to severe fatty infiltration. Lipidosis was positively correlated with the severity of liver cell degeneration, and negatively correlated with the degree of glycogen deposits. Complete glycogen depletion of hepatocytes was not observed in cows, even in the presence of severe hepatic lipidosis. Moderate to severe lymphocytic hepatitis was seen in 39% of cows throughout the study period, and cows with lactation numbers 5 or greater had perisinusoidal fibrosis more often than younger cows. Severe fibrosis and cirrhosis of the liver did not occur. Metabotype B animals exhibited a higher chance of fatty infiltration, lower glycogen storage, and perisinusoidal fibrosis and for this metabotype positive correlations were calculated between increased fat deposition in the liver and marked glycogen depletion, and increased degenerative, inflammatory, fibrotic, and proliferative changes of hepatic tissue. For the treatment with BCC, no significant effect was observed. In summary, during the transition period, the liver of dairy cows is characterized by fat accumulation and glycogen depletion and histologic signs of hepatitis and hepatocyte degeneration. These histomorphologic changes were accentuated in animals exhibiting little alterations in their liver metabolome profile across the transition period (metabotype B) and support the assumption of a decreased grass silage quality as a causative factor.

Characterization of the Plasma Lipidome in Dairy Cattle Transitioning from Gestation to Lactation: Identifying Novel Biomarkers of Metabolic Impairment

The discovery of novel biomarkers for peripartal diseases in dairy cows can improve our understanding of normal and dysfunctional metabolism, and lead to nutritional interventions that improve health and milk production. Our objectives were to characterize the plasma lipidome and identify metabolites associated with common markers of metabolic disease in peripartal dairy cattle. Multiparous Holstein cows (n = 27) were enrolled 30 d prior to expected parturition. Blood and liver samples were routinely collected through to d 14 postpartum. Untargeted lipidomics was performed using quadrupole time-of-flight mass spectrometry. Based on postpartum measures, cows were categorized into low or high total fatty acid area under the curve (total FAAUC; d 1-14 postpartum; 4915 ± 1369 vs. 12,501 ± 2761 (μmol/L × 14 d); n = 18), β-hydroxybutyrate AUC (BHBAAUC; d 1-14 postpartum; 4583 ± 459 vs. 7901 ± 1206 (μmol/L × 14 d); n = 18), or liver lipid content (d 5 and 14 postpartum; 5 ± 1 vs. 12 ± 2% of wet weight; n = 18). Cows displayed decreases in plasma triacylglycerols and monoalkyl-diacylglycerols, and the majority of phospholipids reached a nadir at parturition. Phosphatidylcholines (PC) 32:3, 35:5, and 37:5 were specific for high total FAAUC, PC 31:3, 32:3, 35:5, and 37:5 were specific for high BHBAAUC, and PC 31:2, 31:3, and 32:3 were specific for high liver lipid content. PC 32:3 was specific for elevated total FA, BHBA, and liver lipid content. Lipidomics revealed a dynamic peripartal lipidome remodeling, and lipid markers associated with elevated total FA, BHBA, and liver lipid content. The effectiveness of nutrition to impact these lipid biomarkers for preventing excess lipolysis and fatty liver warrants evaluation.

Effects of Energy Supply from Roughage and Concentrates and the Occurrence of Subclinical Ketosis on Blood Chemistry and Liver Health in Lactating Dairy Cows during Early Lactation

The objectives of this study were to examine the effects of varying dietary energy supply as well as the impacts of subclinical ketosis (SCK) on blood chemistry and liver health. A total 63 German-Holstein cows were housed from three weeks antepartum until sixteen weeks postpartum. After calving, cows were assigned to one of four treatment groups receiving either moderate or high energy concentrations in roughage and secondly moderate or high amounts of concentrates. Retrospectively, cows were additionally grouped according to their β-hydroxybutyrate concentration (SK: cows with SCK vs. CON: cows without SCK). The different energy supply of treatment groups had little effects on blood and liver variables; greater differences occurred between SK and CON cows. Liver fat content of SK cows was 34% higher compared to CON cows. Also, the activity of aspartate aminotransferase and γ-glutamyl transferase, bilirubin concentration, and percentage of granulocytes were increased in SK cows. The results indicate that cows were able to adjust their metabolism to different dietary energy supplies without having a clearly increased risks for metabolic disorders. However, individual animals of all groups developed a metabolic derailment during the postpartum period resulting in SCK, which is closely connected with impaired liver function, compromised immune-responsiveness, and elevated oxidative stress.

Malnutrition as the cause of recumbency in suckler cows associated with Trypanosoma theileri infection

Background

Recumbent cows are a diagnostic challenge because of a wide range of differential diagnoses, which include trauma, neurological and metabolic disorders, malnutrition and mineral deficiencies. This case report describes recumbent suckler cows that presented as a herd problem. In addition to weakness due to inanition, Cu and Se deficiencies were considered as possible aetiologies of the recumbency. Furthermore, Trypanosoma (T.) theileri, a blood parasite of unknown importance in Germany, was detected in the blood of some cows.

Case presentation

Three recumbent cows were referred to the Clinic for Ruminants and Swine, Faculty of Veterinary Medicine of the University of Leipzig. They were unable to rise and had low body condition scores and rough hair coats. Haematological and serum biochemical analyses showed neutrophilia, electrolyte imbalances, increased activities of muscle and liver enzymes and decreased concentrations of trace elements, especially Copper (Cu) and Selenium (Se). T. theileri was detected in a routine blood smear from one cow. The cows did not respond to an intensive care protocol, which included intravenous fluids and electrolytes, mineral substitution, non-steroidal anti-inflammatories and antibiotics, and were therefore euthanized or died. Postmortem examination showed cachexia, subcutaneous and scleral oedema and muscular dystrophy, especially in the hind limbs. Follow-up examination of the herd of origin produced similar findings including the detection of T. theileri in a large proportion of the herd. Ration analysis revealed considerable undersupply of several nutrients.

Conclusions

Based on all findings, an aetiological diagnosis of trace mineral and nutrient deficiency with possible involvement of T. theileri was made.

Methyl donor supplementation suppresses the progression of liver lipid accumulation while modifying the plasma triacylglycerol lipidome in periparturient Holstein dairy cows

Co-supplementation of methyl donors may lower hepatic lipid content in transition cows. To define the ability of methyl donor supplementation (MDS) to reduce hepatic lipid content and modify the plasma lipidome, 30 multiparous Holstein cows (2.04 ± 0.69 lactations; 689 ± 58 kg of body weight; 3.48 ± 0.10 units of body condition score) were fed a ration with or without rumen-protected methyl donors (22 g/d of Met, 10 g/d of choline chloride, 3 g/d of betaine, 96 mg/d of riboflavin, and 1.4 mg/d of vitamin B₁₂) from d -28 before expected calving through d 14 postpartum. Cows were randomly enrolled based on predefined selection criteria (body condition score and parity). Base diets without MDS were formulated for gestation (15.4% crude protein with a predicted Lys-to-Met ratio of 3.25; 1.44 Mcal of net energy for lactation/kg of dry matter) and lactation (16.6% crude protein with a predicted Lys-to-Met ratio of 3.36; 1.64 Mcal of net energy for lactation/kg of dry matter). Blood sampling occurred from d -28 relative to expected calving through d 14 postpartum. Liver tissue was biopsied at d -28 relative to expected calving and on d 5 and 14 postpartum. In addition to routine analyses, serum AA concentrations on d 10 and 12 were quantified using mass spectrometry. Plasma triacylglycerol (TAG) and cholesteryl esters (CE) were qualitatively measured using time-of-flight mass spectrometry. Data were analyzed using a mixed model with repeated measures. Dry matter intake and milk yield were not modified by MDS. The transition from d -28 relative to expected parturition to d 14 postpartum was characterized by increased plasma fatty acid (0.15 to 0.71 mmol/L) and β-hydroxybutyrate (0.34 to 0.43 mmol/L) levels and liver lipid content (3.91 to 9.16%). Methyl donor supplementation increased the serum Met level by 26% and decreased the serum Lys-to-Met ratio by 21% on d 10 and 12, respectively. Moreover, the increase in hepatic lipid content from d 5 through 14 postpartum was suppressed with MDS relative to control (3.57 vs. -0.29%). Dietary MDS modified the TAG and CE lipidome. For example, MDS increased plasma TAG 46:3 (carbon number:double bond) by 116% relative to control cows on d 5 postpartum. Moreover, MDS tended to increase plasma CE 34:6. In contrast, MDS lowered plasma TAG 54:8 by 39% relative to control cows on d 5 postpartum. We concluded that in the absence of gains in dry matter intake and milk and milk protein yields, dietary MDS slows the progression of hepatic lipid accumulation and modifies the plasma TAG lipidome in transition cows.

Effects of a Change from an Indoor-Based Total Mixed Ration to a Rotational Pasture System Combined with a Moderate Concentrate Feed Supply on the Health and Performance of Dairy Cows

In spring, the transition from a total mixed ration (TMR) to pasture requires metabolic adaptions for the cow. It had been shown that supply of low amounts of concentrate after transition to full-time grazing caused energy deficits, resulting in a lower milking performance and changes in a variety of variables indicative for energy metabolism. The present study aimed to investigate how a moderate concentrate supply (4.5 kg dry matter cow/day) after transition to pasture influences health and production indicators. Over a 12-week trial period dairy cows were observed during transition from confinement to pasture (pasture group: PG) and compared to cows fed TMR indoors (confinement group: CG). On average, the PG consumed less feed and energy than the CG and mobilized body reserves, which is mirrored in a decrease of body condition and various fat depots. These effects were paralleled by elevated serum concentrations of non-esterified fatty acids and ketone bodies as well as an increase in liver fat content. The physical activity (elevated walking, eating, decreasing rumination time) of the PG was significantly higher than that of the CG, which intensified the energy deficiency and resulted in a lower milk yield. In conclusion, the moderate concentrate supply was insufficient to counterbalance the lower energy intake from pasture during transition.

Effects of TNF receptor blockade on in vitro cell survival and response to negative energy balance in dairy cattle

Background

Associative data and some controlled studies suggest that the inflammatory cytokine tumor necrosis factor (TNF) α can induce fatty liver in dairy cattle. However, research demonstrating that TNFα is a necessary component in the etiology of bovine fatty liver is lacking. The aim of this work was to evaluate whether blocking TNFα signaling with a synthetic cyclic peptide (TNF receptor loop peptide; TRLP) would improve liver metabolic function and reduce triglyceride accumulation during feed restriction.

Results

Capability of TRLP to inhibit TNFα signaling was confirmed on primary bovine hepatocytes treated with recombinant bovine TNFα and 4 doses of TRLP (0, 1, 10, 50 μmol/L) over 24 h. Next, 4 lactating Holstein cows (parity 1.4 ± 0.5, 433 ± 131 d in milk) in an incomplete Latin rectangle design (3 × 2) were subcutaneously administered with different TRLP doses (0, 1.5, 3.0 mg/kg BW) every 4 h for 24 h, followed by an intravenous injection of TNFα (5 μg/kg BW). Before and for 2 h after TNFα injection, TRLP decreased plasma non-esterified fatty acid (NEFA) concentration (P ≤ 0.05), suggesting an altered metabolic response to inflammation. Finally, 10 non-pregnant, non-lactating Holstein cows (3.9 ± 1.1 yr of age) were randomly assigned to treatments: control (carrier: 57% DMSO in PBS) or TRLP (1.75 mg TRLP /kg BW per day). Treatments were administrated every 4 h for 7 d by subcutaneous injection to feed-restricted cows fed 30% of maintenance energy requirements. Daily blood samples were analyzed for glucose, insulin, β-hydroxybutyrate, NEFA, and haptoglobin concentrations, with no treatment effects detected. On d 7, cows completed a glucose tolerance test (GTT) by i.v. administration of a dextrose bolus (300 mg glucose/kg BW). Glucose, insulin, and NEFA responses failed to demonstrate any significant effect of treatment during the GTT. However, plasma and liver analyses were not indicative of dramatic lipolysis or hepatic lipidosis, suggesting that the feed restriction protocol failed to induce the metabolic state of interest. Injection site inflammation, assessed by a scorer blinded to treatment, was enhanced by TRLP compared to control.

Conclusions

Although the TRLP inhibited bovine TNFα signaling and altered responses to i.v. administration of TNFα, repeated use over 7 d caused apparent local allergic responses and it failed to alter metabolism during a feed restriction-induced negative energy balance. Although responses to feed restriction seemed atypical in this study, side effects of TRLP argue against its future use as a tool for investigating the role of inflammation in metabolic impacts of negative energy balance.

Temporal changes in sphingolipids and systemic insulin sensitivity during the transition from gestation to lactation

Reduced insulin action develops naturally during the peripartum to ensure maternal nutrient delivery to the fetus and neonate. However, increased insulin resistance can facilitate excessive lipolysis which in turn promotes metabolic disease in overweight dairy cattle. Increased fatty acid availability favors the accumulation of the sphingolipid ceramide and is implicated in the pathogenesis of insulin resistance, however, the relationship between sphingolipid metabolism and insulin resistance during the peripartum remains largely unknown. Our objectives were to characterize temporal responses in plasma and tissue sphingolipids in lean and overweight peripartal cows and to establish the relationships between sphingolipid supply and lipolysis, hepatic lipid deposition, and systemic insulin action. Twenty-one multiparous lean and overweight Holstein cows were enrolled in a longitudinal study spanning the transition from gestation to lactation (d -21 to 21, relative to parturition). Plasma, liver, and skeletal muscle samples were obtained, and sphingolipids were profiled using LC/MS/MS. Insulin sensitivity was assessed utilizing intravenous insulin and glucose challenges. Our results demonstrated the following: first, insulin resistance develops postpartum concurrently with increased lipolysis and hepatic lipid accumulation; second, ceramides and glycosylated ceramides accumulate during the transition from gestation to lactation and are further elevated in overweight cows; third, ceramide accrual is associated with lipolysis and liver lipid accumulation, and C16:0- and C24:0-ceramide are inversely associated with systemic insulin sensitivity postpartum; fourth, plasma sphingomyelin, a potential source of ceramides reaches a nadir at parturition and is closely associated with feed intake; fifth, select sphingomyelins are lower in the plasma of overweight cows during the peripartal period. Our results demonstrate that dynamic changes occur in peripartal sphingolipids that are influenced by adiposity, and are associated with the onset of peripartal insulin resistance. These observations are in agreement with a putative potential role for sphingolipids in facilitating the physiological adaptations of peripartum.

Variation in fat content between liver lobes and comparison with histopathological scores in dairy cows with fatty liver

Background

The assessment of a liver biopsy remains the gold standard for diagnosing and staging fatty liver in dairy cows, which is often necessary for diagnostic and research purposes. Accuracy of the diagnosis relays on the quality of the biopsy, the assumed representativeness of a small tissue sample for a disease process throughout the liver and accurate human evaluation of histologic specimens. The objective of the present study was to assess the distribution of triacylglycerol (TAG) infiltration throughout the parenchyma of livers with different degrees of fatty liver in dairy cows. In addition, histopathological scores from the corresponding specimens were compared to a quantitative measurement of TAG, as well as the agreement between two observers.

Methods

Thirty livers with different degrees of lipid infiltration were selected and 10 different locations throughout the liver were assessed. The TAG content was measured enzymatically, calculated in % or mg/g wet weight, and assigned to a scoring system. Corresponding tissue specimens were stained with hematoxylin-eosin (H&E) and Oil red O (ORO) for histopathological evaluation, using a scoring system.

Results

The difference in TAG content between any locations was less than 2%. Based on the scoring system the TAG concentration was even distributed in 79.3% of the livers. Based on kappa statistics the agreement between two pathologists and staining technique in scoring histological specimens was moderate to fair.

Conclusions

Overall the distribution of TAG throughout the liver and the accuracy of human evaluation of liver biopsies may lead to acceptable diagnoses for clinical purposes. Within the liver lobules a common pattern of lipid distribution depending on severity could be observed. For the staging of lipid infiltration for research projects, some degree of variation needs to be considered.

Effects of Inhibiting Dipeptidyl Peptidase-4 (DPP4) in Cows with Subclinical Ketosis

The inhibition of dipeptidyl peptidase-4 (DPP4) via specific inhibitors is known to result in improved glucose tolerance and insulin sensitivity and decreased accumulation of hepatic fat in type II diabetic human patients. The metabolic situation of dairy cows can easily be compared to the status of human diabetes and non-alcoholic fatty liver. For both, insulin sensitivity is reduced, while hepatic fat accumulation increases, characterized by high levels of non-esterified fatty acids (NEFA) and ketone bodies.Therefore, in the present study, a DPP4 inhibitor was employed (BI 14332) for the first time in cows. In a first investigation BI 14332 treatment (intravenous injection at dosages of up to 3 mg/kg body weight) was well tolerated in healthy lactating pluriparous cows (n = 6) with a significant inhibition of DPP4 in plasma and liver. Further testing included primi- and pluriparous lactating cows suffering from subclinical ketosis (β-hydroxybutyrate concentrations in serum > 1.2 mM; n = 12). The intension was to offer effects of DPP4 inhibition during comprehensive lipomobilisation and hepatosteatosis. The cows of subclinical ketosis were evenly allocated to either the treatment group (daily injections, 0.3 mg BI 14332/kg body weight, 7 days) or the control group. Under condition of subclinical ketosis, the impact of DPP4 inhibition via BI 14332 was less, as in particular β-hydroxybutyrate and the hepatic lipid content remained unaffected, but NEFA and triglyceride concentrations were decreased after treatment. Owing to lower NEFA, the revised quantitative insulin sensitivity check index (surrogate marker for insulin sensitivity) increased. Therefore, a positive influence on energy metabolism might be quite possible. Minor impacts on immune-modulating variables were limited to the lymphocyte CD4⁺/CD8⁺ ratio for which a trend to decreased values in treated versus control animals was noted. In sum, the DPP4 inhibition in cows did not affect glycaemic control like it is shown in humans, but was able to impact hyperlipemia, as NEFA and TG decreased.

Effects of prepartal body condition score and peripartal energy supply of dairy cows on postpartal lipolysis, energy balance and ketogenesis: an animal model to investigate subclinical ketosis

Subclinical ketosis is a metabolic disorder which often goes undiagnosed and leads to constricted performance and an impairment of general condition. In the current study subclinical ketosis was characterised by a β-hydroxybutyrate (BHB) concentration of >1·2 mmol/l in blood serum. To generate this metabolic situation, an animal model was created. The model, based on group-specific interaction of dietary energy supply and body condition, is appropriate for testing the medical effectiveness of treating this kind of ketosis and its concomitants. During the trial, 18 dairy cows (primiparous and pluriparous) were assigned, according to their body condition score (BCS) 6 weeks before expected parturition, to a normal [6·78 MJ net energy for lactation (NEL)/kg dry matter; 20% concentrate] or to a high-energy feeding group (7·71 MJ NEL/kg dry matter; 60% concentrate). Therefore cows with the highest BCS were allocated to the high-energy group to enhance the contrast with the control group. Statistical analysis was done using the MIXED procedure of SAS. Effects were declared significant when P-values were ⩽0·05. Owing to the higher energy concentration and dry matter intake, the energy intake and balance was significantly higher in the high-energy feeding group, with strong effects on lipid metabolism and health in blood and liver post partum. Within the first 2 weeks after calving, 8 out of 9 cows (89%) of the high-energy group had BHB values indicative of subclinical ketosis. These cows also had significantly higher values of non-esterified fatty acids (NEFA), aspartate transaminase (AST) and glutamate dehydrogenase (GLDH) post partum, as well as a raised total lipid content of the liver. RQUICKI, a calculated parameter which is based on serum concentrations of glucose, insulin and NEFA to assess the insulin sensitivity, was not affected by treatment. Therefore, RQUICKI does not seem to be the right parameter for diagnosing decreased insulin sensitivity in cows affected by subclinical ketosis. The milk fat and the fat:protein ratio of the high-energy group was also higher, even though there was no decrease in milk yield for cows with subclinical BHB values.

TNFα altered inflammatory responses, impaired health and productivity, but did not affect glucose or lipid metabolism in early-lactation dairy cows

Inflammation may be a major contributing factor to peripartum metabolic disorders in dairy cattle. We tested whether administering an inflammatory cytokine, recombinant bovine tumor necrosis factor-α (rbTNFα), affects milk production, metabolism, and health during this period. Thirty-three Holstein cows (9 primiparous and 24 multiparous) were randomly assigned to 1 of 3 treatments at parturition. Treatments were 0 (Control), 1.5, or 3.0 µg/kg body weight rbTNFα, which were administered once daily by subcutaneous injection for the first 7 days of lactation. Statistical contrasts were used to evaluate the treatment and dose effects of rbTNFα administration. Plasma TNFα concentrations at 16 h post-administration tended to be increased (P<0.10) by rbTNFα administration, but no dose effect (P>0.10) was detected; rbTNFα treatments increased (P<0.01) concentrations of plasma haptoglobin. Most plasma eicosanoids were not affected (P>0.10) by rbTNFα administration, but 6 out of 16 measured eicosanoids changed (P<0.05) over the first week of lactation, reflecting elevated inflammatory mediators in the days immediately following parturition. Dry matter and water intake, milk yield, and milk fat and protein yields were all decreased (P<0.05) by rbTNFα treatments by 15 to 18%. Concentrations of plasma glucose, insulin, β-hydroxybutyrate, non-esterified fatty acids, triglyceride, 3-methylhistidine, and liver triglyceride were unaffected (P>0.10) by rbTNFα treatment. Glucose turnover rate was unaffected (P = 0.18) by rbTNFα administration. The higher dose of rbTNFα tended to increase the risk of cows developing one or more health disorders (P = 0.08). Taken together, these results indicate that administration of rbTNFα daily for the first 7 days of lactation altered inflammatory responses, impaired milk production and health, but did not significantly affect liver triglyceride accumulation or nutrient metabolism in dairy cows.

Transcutaneous vs. intraoperative quantitative ultrasound for staging bovine hepatic steatosis

The aim of this study was to test the hypothesis that quantitative analysis of transcutaneous (Transc) ultrasound (US) images can predict the liver fat content with similar accuracy and precision as using intraoperative (Intraop) US. The second goal was to investigate if a tissue mimicking phantom (TMP) might be used as reference for automatic gain compensation (AGC) vs. depth instead of using the data of a set of cows without hepatic alterations. A study was performed in post partum dairy cows (N = 151), as an animal model of human nonalcoholic fatty liver disease (NAFLD), to test these hypotheses. Five Transc and five Intraop US liver images were acquired in each animal and a liver biopsy was taken. In liver tissue samples, triacylglycerol (TAG) content was measured by biochemical analysis and hepatic alterations, other than hepatic steatosis, were excluded by clinical examination. Several preprocessing steps were performed before the ultrasound tissue characteristics (UTC) parameters of B-mode images were derived. Stepwise multiple linear regression analysis was performed on a training set (N = 76) and the results were used on the test group (N = 75) to predict the TAG content in the liver. In all cases, the residual attenuation coefficient (ResAtt) was the only selected parameter. Receiver operating characteristics (ROC) analysis was applied to assess the performance and area under the curve (AUC) of predicting TAG and to compare the sensitivity and specificity of the methods used. High ROC values for AUC (95%), sensitivity (87%) and specificity (83%) for both Intraop and Transc applications with control group as well as with phantom-based AGC were obtained. Consequently, it can be concluded that Transc results are equivalent to Intraop results. Furthermore, equivalent ROC values, when using TMP AGC, indicates the potential use of TMP-based corrections instead of normal group-based corrections. The high predictive values indicate that noninvasive quantitative US has a great potential for staging and screening on hepatic steatosis in cows.