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Our primary objective was to determine the effects of the abomasal infusion of 16-carbon (16C) and 22-carbon (22C) fatty acids (FA) on apparent FA digestibility, plasma FA concentrations, and their incorporation into milk fat in cows. Our secondary objective was to study the effects of 1-carbon donors choline and l-serine on these variables. Five rumen-cannulated Holstein cows (214 ± 4.9 d in milk; 3.2 ± 1.1 parity) were enrolled in a 5 × 5 Latin square experiment with experimental periods lasting 6 d. Abomasal infusates consisted of (1) palmitic acid (PA; 98% 16:0 of total fat), (2) PA + choline chloride (PA+CC; 50 g/d of choline chloride), (3) PA + l-serine (PA+S; 170 g/d of l-serine), (4) behenic acid (BA; 92% 22:0 of total fat), and (5) docosahexaenoic acid algal oil (DHA; 47.5% DHA of total fat). Emulsions were formulated to provide 301 g/d of total FA and were balanced to provide a minimum of 40 and 19 g/d of 16:0 and glycerol, respectively, to match the content found in the infused algal oil. Apparent digestibility of FA was highest in DHA, intermediate in PA, and lowest in BA. Digestibility of 16C FA was lowest in BA and highest in PA. The digestibility of 22C FA was highest in DHA relative to BA (99 vs. 58%), whereas 1-carbon donors had no effect on 22C FA digestibility. Plasma 16C FA concentrations were greatest with PA treatment, and 22C FA concentrations were ~3-fold greater in DHA-treated cows relative to all other treatments. Milk fat 16:0 content was highest in PA relative to BA and DHA (e.g., 37 vs. 27% in PA and DHA), whereas the milk yield of 16:0 was higher in PA relative to DHA (i.e., 454 vs. 235 g/d). Similarly, milk 22:0 content and yield were ~10-fold higher in BA relative to all other treatments, whereas DHA treatment resulted in higher content and yield of 22:6 in milk fat relative to all other treatments (41- and 38-fold higher, respectively). Consequently, the content of FA >16C (i.e., preformed) was higher in milk fat from cows infused with BA and DHA relative to PA. De novo FA content in milk did not differ between PA, PA+CC, and PA+S (~16% of milk fat) but was higher in BA and DHA treatments (19 and 21%, respectively). We conclude that FA carbon chain length and degree of saturation affected FA digestibility and availability for absorption as well as their incorporation into milk fat. The abomasal infusion of choline chloride and l-serine did not modify these variables relative to infusing palmitic acid alone.

Deoiled soy lecithin is a feed additive enriched in phospholipids. Our study evaluated the effects of dietary deoiled soy lecithin supplementation on (1) milk production and composition, (2) plasma and milk fatty acid (FA) content and yield, and (3) apparent FA digestibility and absorption in lactating dairy cows fed fractionated palm fat. In a split-plot Latin square design, 16 Holstein cows (160 ± 7 days in milk; 3.6 ± 1.2 parity) were randomly allocated to a main plot receiving a corn silage and alfalfa haylage-based diet with palm fat containing either moderate (MPA) or high palmitic acid (HPA) content at 1.75% of ration dry matter (72 or 99% palmitic acid, respectively; n = 8/palm fat diet). On each palm fat diet, deoiled soy lecithin was top-dressed at 0, 0.12, 0.24, or 0.36% of ration dry matter in a replicated 4 × 4 Latin square design. Following a 14-d covariate period, lecithin supplementation spanned 14 d, with milk and blood collected during the final 3 d. Milk composition and pooled plasma markers were measured. The statistical model included the fixed effects of palm fat type, lecithin dose, period, and the interaction between palm fat type and lecithin dose. The random effect of cow nested within palm fat group was also included. Lecithin linearly decreased dry matter intake. In cows fed HPA, lecithin feeding reduced milk fat content and tended to decrease milk fat yield. Although no changes in milk yield were observed, a quadratic reduction in 3.5% fat-corrected milk was observed with increasing lecithin dose. Lecithin linearly increased energy-corrected milk efficiency in cows fed MPA. Lecithin supplementation also decreased milk urea nitrogen, relative to unsupplemented cows. The proportion of 16-carbon FA in milk fat decreased linearly with lecithin dose, whereas 18-carbon FA increased linearly. Lecithin reduced de novo FA (16-carbon) content and tended to increase preformed FA (16-carbon) content in a linear manner. Compared with MPA, HPA diets reduced apparent total and 16-carbon FA digestibility and absorption. Deoiled soy lecithin feeding did not modify FA digestibility or absorption. Our observations suggest that soy lecithin feeding modifies rumen digestion to reduce dry matter intake and change milk composition.

The fungal isolate myriocin inhibits serine palmitoyltransferase and de novo ceramide synthesis in rodents; however, the effects of myriocin on ceramide concentrations and metabolism have not been previously investigated in ruminants. In our study, 12 non-lactating crossbred ewes received an intravenous bolus of myriocin (0, 0.1, 0.3, or 1.0 mg/kg/body weight [BW]; CON, LOW, MOD, or HIGH) every 48 h for 17 d. Ewes consumed a high-energy diet from day 1 to 14 and were nutrient-restricted (straw only) from day 15 to 17. Blood was collected preprandial and at 1, 6, and 12 h relative to bolus and nutrient restriction. Tissues were collected following euthanasia on day 17. Plasma was analyzed for free fatty acids (FFAs), glucose, and insulin. Plasma and tissue ceramides were quantified using mass spectrometry. HIGH selectively decreased metabolizable energy intake, BW, and plasma insulin, and increased plasma FFA (Dose, P < 0.05). Myriocin linearly decreased plasma very-long-chain (VLC) ceramide and dihydroceramide (DHCer) by day 13 (Linear, P < 0.05). During nutrient restriction, fold-change in FFA was lower with increasing dose (P < 0.05). Nutrient restriction increased plasma C16:0-Cer, an effect suppressed by MOD and HIGH (Dose × Time, P < 0.05). Myriocin linearly decreased most ceramide and DHCer species in the liver and omental and mesenteric adipose, VLC ceramide and DHCer in the pancreas, and C18:0-Cer in skeletal muscle and subcutaneous adipose tissue (Linear, P ≤ 0.05). We conclude that the intravenous delivery of 0.3 mg of myriocin/kg of BW/48 h decreases circulating and tissue ceramide without modifying energy intake in ruminants.

Dietary lecithin is a source of choline. Our objective was to evaluate the effects of dietary deoiled soy lecithin feeding on circulating choline, choline metabolites, and the plasma phospholipid profile in lactating dairy cows fed fractionated palm fatty acids. In a split-plot Latin square design, 16 Holstein cows (160 ± 7 d in milk; 3.6 ± 1.2 parity) were randomly allocated to a main plot receiving a corn silage and alfalfa haylage-based diet with palm fat containing either moderate or high palmitic acid content at 1.75% of ration dry matter (moderate and high palmitic acid containing 72 or 99% palmitic acid in fat supplement, respectively; n = 8/palm fat diet). Within each palm fat group, deoiled soy lecithin was top-dressed at 0, 0.12, 0.24, or 0.36% of ration dry matter in a replicated 4 × 4 Latin square design with 14-d experimental periods. A 14-d covariate period was used to acclimate cows to palm fat feeding without lecithin supplementation. Blood sampling occurred during the final 3 d of each experimental period. Plasma choline and choline metabolites were quantified using liquid chromatography and mass spectrometry. Plasma phospholipids were profiled using time-of-flight mass spectrometry. Whereas no effects of treatments were detected for plasma choline or methionine, lecithin feeding increased the plasma concentrations of choline metabolites trimethylamine N-oxide and dimethylglycine (24 and 11%, respectively). Plasma phosphatidylcholine (PC) and sphingomyelin (SM) concentrations increased with deoiled lecithin feeding (e.g., PC 16:0/22:6 and SM d18:1/18:3). Lecithin supplementation also increased plasma lysophosphatidylcholine (LPC) concentrations (e.g., LPC 18:0) while reducing plasma phosphatidylethanolamine (PE) concentrations (e.g., PE 16:0/20:5). Although increases in microbial-derived trimethylamine N-oxide suggest gastrointestinal lecithin degradation, elevations in plasma dimethylglycine, PC, LPC, and SM suggest that choline availability was improved by lecithin feeding in cows, thus supporting enhanced endogenous phospholipid synthesis.

The hepatic synthesis and export of ceramide is enhanced in diabetic monogastrics. Moreover, ceramide in lipoproteins can mediate the development of insulin resistance. We have previously demonstrated that circulating ceramide increases during the progression of insulin resistance in postpartum dairy cows. Considering that the origins of circulating ceramide required investigation, our objective was to develop a method to characterize the ceramide profile of lipoprotein fractions collected from dairy cows. Serum was collected from 4 nonpregnant and nonlactating Holstein dairy cows. Serum lipoproteins were isolated using size exclusion chromatography by fast protein liquid chromatography (SEC-FPLC). Measurement of triacylglycerol (TAG), phospholipid, total cholesterol, and protein was performed using standard colorimetry practices. Following lipid extraction, fractions were analyzed using electrospray ionization tandem mass spectrometry. Data were analyzed as repeated measures using a mixed model. Lipoprotein isolation using SEC-FPLC and subsequent colorimetric analyses confirmed the presence of 4 distinct fractions: TAG-rich, low density (LDL), and large (buoyant) and small (dense) high density lipoprotein (HDL) subclasses. As expected, the fraction representing mixed very low density lipoproteins and chylomicrons primarily contained TAG. Low density lipoprotein fractions were equally enriched with cholesterol and phospholipid. Buoyant HDL contained elevated levels of cholesterol, phospholipid, and protein. In contrast, the fraction containing dense HDL primarily contained protein. Our method revealed that LDL are enriched with ceramides. Ceramides were also compartmentalized to a lesser extent within both HDL subclasses and TAG-rich lipoproteins. Comparable to whole serum, C16:0-ceramide was the predominant ceramide quantified in all lipoprotein subclasses. Interestingly, the proportion of C24:0-ceramide to total ceramide was elevated in TAG-rich lipoproteins, relative to all other lipoprotein subclasses. We conclude that SEC-FPLC coupled with mass spectrometry is a means to quantify ceramides in lipoprotein fractions. Moreover, ceramides are enriched within bovine LDL, and lipoprotein ceramide profiles reflect levels observed in whole serum. Future investigation will need to determine the biological importance of lipoprotein ceramides with distinct C-chains at amide residues.

Introducción: la lesión renal aguda es una complicación frecuente en pacientes con COVID-19 y su aparición es un potencial indicador de disfunción multiorgánica y de gravedad de la enfermedad. Objetivo: desarrollar, mediante un consenso de expertos, recomendaciones para la prevención, el diagnóstico y el manejo de la lesión renal aguda en pacientes con infección por SARS-CoV-2/COVID-19 con base en la evidencia disponible. Materiales y métodos: a partir de una rápida revisión sistemática en las bases de datos EMBASE y PubMed y en los portales de algunas sociedades científicas, se formularon recomendaciones preliminares, las cuales fueron consultadas a un colectivo experto a través de una herramienta en línea. Se definió acuerdo respecto a las recomendaciones cuando se obtuvo aprobación en al menos el 70 %. La calidad de la evidencia se evalúo de acuerdo con el tipo de documento incluido y la fuerza de las recomendaciones se clasificó como fuerte o débil. Resultados: la consulta al colectivo de expertos tuvo lugar entre el 24 y 29 de mayo de 2020. El rango de acuerdo osciló entre 75,5 % y 100 % y 50 expertos clínicos declararon su conflicto de interés. Se lograron establecer recomendaciones para prevenir, diagnosticar y manejar la lesión renal aguda en pacientes con infección por SARS CoV2/COVID-19. Conclusiones: aunque la información disponible de buena calidad respecto a lesión renal aguda en paciente con COVID-19 es escasa, las recomendaciones aquí presentadas permitirán orientar la toma de decisiones clínicas y estratégicas alrededor de pacientes con esta complicación; de igual forma se garantizará un cuidado centrado en las personas y con altos estándares de calidad, y la generación de políticas de seguridad, salud y bienestar para los equipos multidisciplinarios de atención

Changes in maternal insulin sensitivity and circulating lipids typically occur during the metabolic transitions of pregnancy and lactation. Although ceramides can cause insulin resistance in mammals, their potential roles during pregnancy and lactation are unknown. We hypothesized that changes in lipids like ceramide and triglycerides could occur across different reproductive states and relate to insulin resistance. Our objectives were to comprehensively characterize lipids in the plasma of pregnant, lactating, and nonpregnant and nonlactating (NPNL) women, and to evaluate the relationship between ceramides and the triglyceride index, a proxy of insulin resistance. Middle-aged Hutterite women from the South Dakota Rural Bone Health Study were classified by reproductive status as nonpregnant and nonlactating (NPNL; 19 observations), pregnant (14 observations), or lactating (31 observations). Several plasma lipids were elevated in pregnancy such as ceramides, triglycerides, and total- and high-density lipoprotein cholesterol. The triglyceride index was highest during pregnancy and was positively associated with long- and very long-chain ceramides. Lipidomics revealed lipid signatures specific to reproductive state, including triglycerides, phosphatidylcholines, sphingomyelins, and cholesteryl esters, which were also related to the triglyceride index. Our data support the possibility that ceramides contribute to the development of insulin resistance during pregnancy, and reveal distinct lipid signatures associated with pregnancy and lactation.

Reductions in insulin sensitivity in periparturient dairy cows develop as a means to support lactation; however, excessive mobilization of fatty acids (FA) increases the risk for peripartal metabolic disorders. Our objectives were to investigate the effect of prepartum body condition score (BCS) on systemic glucose and insulin tolerance, and to compare direct and indirect measurements of insulin sensitivity in peripartal lean and overweight dairy cows. Fourteen multiparous Holstein cows were allocated into two groups according to their BCS at day -28 prepartum: lean (n = 7; BCS ≤ 3.0) or overweight; (n = 7; BCS ≥ 4.0). Liver biopsies were performed on day -27, -14 and 4, relative to expected parturition. Intravenous insulin or glucose tolerances tests were performed following each liver biopsy. Relative to lean cows, overweight cows exhibited lower dry matter intake, lost more BCS and displayed increased plasma FA and β-hydroxybutyrate concentrations and elevated liver lipid content during peripartum. Glucose clearance rate was lower for all cows postpartum. Prepartum BCS had minimal effects on insulin and glucose tolerance; however, the ability of the cow to restore blood glucose levels following an insulin challenge was suppressed by increased BCS. Glucose-dependent parameters of insulin and glucose tolerance were not correlated with surrogate indices of insulin sensitivity. We conclude that prepartum BCS had minimal effect on systemic insulin sensitivity following parturition. The observed inconsistency between surrogate indices of insulin sensitivity and direct measurements of insulin and glucose tolerance adds support to growing concerns regarding their usefulness as tools to estimate systemic insulin action in periparturient cows.

Our study evaluated the dose-dependent effects of a palmitic acid-enriched supplement in basal diets with or without the inclusion of whole cottonseed on nutrient digestibility and production responses of dairy cows. Sixteen Holstein cows (149 ± 56 days in milk) were used in a split plot Latin square design experiment. Cows were blocked by 3.5% fat-corrected milk (FCM) and allocated to a main plot receiving either a basal diet with soyhulls (SH, = 8) or a basal diet with whole cottonseed (CS, = 8) that was fed throughout the experiment. A palmitic acid-enriched supplement (PA 88.5% C16:0) was fed at 0, 0.75, 1.50, or 2.25% of ration DM in a replicated 4 × 4 Latin Square design within each basal diet group. Periods were 14 d with the final 4 d used for data collection. PA dose increased milk fat content linearly, and cubically affected yields of milk fat and 3.5% FCM. The PA dose did not affect milk protein and lactose contents, BW, and BCS, but tended to increase yields of milk, milk protein, and milk lactose. Also, PA dose reduced DMI and 16-carbon fatty acid digestibility quadratically, and increased 18-carbon fatty acid digestibility quadratically. There were no effects of basal diet on the yield of milk or milk components, but DMI tended to decrease in CS compared with SH, increasing feed efficiency (3.5% FCM/DMI). Compared with SH, CS diets increased yield of preformed milk fatty acids and 16-carbon fatty acid digestibility, and tended to decrease 18-carbon fatty acid digestibility. We observed basal diet × PA dose interactions for yields of milk and milk protein and for 16-carbon and total fatty acid digestibility, as well as tendency for yields of milk fat and 3.5% FCM. Also, there was a tendency for an interaction between basal diet and PA dose for NDF digestibility, which increased more for CS with increasing PA than for SH. PA dose linearly decreased digestibility of total fatty acids in SH diets but did not affect it in CS diets Results demonstrate that responses to PA dose are affected by the dietary basal diet. Additionally, the decrease in fatty acid digestibility only in the SH diets suggests that digestibility is impacted mainly by the profile of 16- and 18-carbon fatty acids reaching the duodenum. Under the dietary conditions evaluated, the yield of 3.5% FCM and milk fat were optimal when PA was fed at 1.5% of ration DM.

Reduced insulin action is a key adaptation that facilitates glucose partitioning to the mammary gland for milk synthesis and enhances adipose tissue lipolysis during early lactation. The progressive recovery of insulin sensitivity as cows advance toward late lactation is accompanied by reductions in circulating nonesterified fatty acids (NEFA) and milk yield. Because palmitic acid can promote insulin resistance in monogastrics through sphingolipid ceramide-dependent mechanisms, palmitic acid (C16:0) feeding may enhance milk production by restoring homeorhetic responses. We hypothesized that feeding C16:0 to mid-lactation cows would enhance ceramide supply and ceramide would be positively associated with milk yield. Twenty multiparous mid-lactation Holstein cows were enrolled in a study consisting of a 5-d covariate, 49-d treatment, and 14-d posttreatment period. All cows were randomly assigned to a sorghum silage-based diet containing no supplemental fat (control; n=10; 138±45 d in milk) or C16:0 at 4% of ration dry matter (PALM; 98% C16:0; n=10; 136±44 d in milk). Blood and milk were collected at routine intervals. Liver and skeletal muscle tissue were biopsied at d 47 of treatment. Intravenous glucose tolerance tests (300mg/kg of body weight) were performed at d -1, 24, and 49 relative to start of treatment. The plasma and tissue concentrations of ceramide and glycosylated ceramide were determined using liquid chromatography coupled with tandem mass spectrometry. Data were analyzed as repeated measures using a mixed model with fixed effects of treatment and time, and milk yield served as a covariate. The PALM treatment increased milk yield, energy-corrected milk, and milk fat yield. The most abundant plasma and tissue sphingolipids detected were C24:0-ceramide, C24:0-monohexosylceramide (GlcCer), and C16:0-lactosylceramide. Plasma concentrations of total ceramide and GlcCer decreased as lactation advanced, and ceramide and GlcCer were elevated in cows fed PALM. Palmitic acid feeding increased hepatic ceramide levels, a response not observed in skeletal muscle tissue. Plasma ceramides (e.g., C24:0-ceramide) were positively correlated with plasma NEFA and milk yield, and positively correlated with NEFA levels following a glucose challenge. Our data demonstrate a remodeled plasma and hepatic sphingolipidome in mid-lactation dairy cows fed PALM. The potential involvement in ceramide in homeorhetic nutrient partitioning to support lactation requires further consideration.

Feeding saturated fatty acids may enhance milk yield in part by decreasing insulin sensitivity and shifting glucose utilization toward the mammary gland. Our objective was to evaluate the effects of palmitic acid (C16:0) on milk production and insulin sensitivity in cows. Twenty multiparous mid-lactation Holstein cows were enrolled in a study consisting of a 5-d covariate, 49-d treatment, and 14-d posttreatment period. All cows received a common sorghum silage-based diet and were randomly assigned to a diet containing no supplemental fat (control; n=10; 138±45d in milk) or C16:0 at 4% of ration DM (PALM; 98% C16:0; n=10; 136±44d in milk). Blood and milk were collected at routine intervals. Intravenous glucose tolerance tests (300mg/kg of body weight) were performed at d −1, 24, and 49 relative to start of treatment. Data were analyzed as repeated measures using a mixed model with fixed effects of treatment and time, and milk yield served as a covariate. The PALM treatment increased milk yield by wk 7. Furthermore, PALM increased milk fat yield and energy-corrected milk at wk 3 and 7. Changes in milk production occurred in parallel with enhanced energy intake. Increased milk fat yield during PALM treatment was due to increased C16:0 and C16:1 incorporation; PALM had no effect on concentration of milk components, BW, or body condition score. Two weeks posttreatment, energy-corrected milk and milk fat yield remained elevated in PALM-fed cows whereas yields of milk were similar between treatments. Increased milk fat yield after PALM treatment was due to increased de novo lipogenesis and uptake of preformed fatty acids. The basal concentration of nonesterified fatty acids (NEFA) in plasma increased by d 4, 6, and 8 of PALM treatment, a response not observed thereafter. Although PALM supplementation did not modify insulin, glucose, or triacylglycerol levels in plasma, total cholesterol in plasma was elevated by wk 3. Estimated insulin sensitivity was lower during the first week of PALM treatment; however, glucose disposal following glucose tolerance tests was not modified. In contrast, C16:0 feeding reduced glucose-stimulated NEFA disappearance by wk 7. Results demonstrate that increasing dietary energy from C16:0 for 7wk improves milk yield and milk composition without modifying systemic glucose tolerance. Reduced glucose-stimulated NEFA disappearance with C16:0 feeding and elevated circulating NEFA may reflect changes in adipose tissue insulin sensitivity.

Recombinant bovine somatotropin (rBST) changes metabolism to spare glucose for milk synthesis in cows. Ceramides inhibit insulin responsiveness in bovine adipocytes and are associated with insulin resistance and milk production in cows. The mechanisms by which rBST supports lactation may involve ceramide. Eight multiparous lactating Holstein cows were enrolled in a 2 × 2 replicated Latin square design with 14-d periods. Cows received a single rBST injection (Posilac; Elanco Animal Health, Indianapolis, IN; 0.062 mg/kg BW) or no injection (CON). An epinephrine challenge, insulin tolerance test, and liver biopsy were performed. Somatotropin enhanced the conversion of feed nutrients into milk components and increased plasma free fatty acid (FFA) concentrations (P < 0.01). Area-under-the-curves for FFA in response to epinephrine and insulin were greater in rBST-treated cows. In response to insulin, glucose concentrations (20- and 30-min post-challenge) and insulin area-under-the-curve were higher with rBST treatment (P < 0.05

Our objectives were to (1) determine whether the abomasal infusion of behenic acid (C22:0) elevated hepatic ceramide relative to palmitic acid (C16:0) or docosahexaenoic acid (C22:6n-3) infusion; (2) assess whether the abomasal infusion of choline chloride or l-serine elevated hepatic phosphatidylcholine (PC) in cows abomasally infused with C16:0; and (3) characterize the PC lipidome in cows abomasally infused with C22:6n-3, relative to C16:0 or C22:0 infusion. In a 5 × 5 Latin square design, 5 rumen-cannulated Holstein cows (214 ± 4.9 DIM; 3.2 ± 1.1 parity) were enrolled in a study with 6-d periods. Abomasal infusates consisted of (1) palmitic acid (PA; 98% C16:0); (2) PA + choline chloride (PA+C; 50 g/d choline chloride); (3) PA + l-serine (PA+S; 170 g/d l-serine); (4) behenic acid (BA; 92% C22:0); and (5) an algal oil rich in docosahexaenoic acid (DHA; 44% C22:6n-3). Emulsion infusates provided 301 g/d of total fatty acids containing a minimum of 40 g/d of C16:0. Cows were fed a corn silage-based diet. Milk was collected on d -2, -1, 5, and 6. Blood was collected and liver biopsied on d 6 of each period. Although we did not detect differences in milk yield, milk fat yield and content were lower in cows infused with DHA relative to PA. Plasma triacylglycerol concentrations were lower with DHA treatment relative to PA or BA. Cows infused with DHA had lower plasma insulin concentrations relative to cows infused with PA only. For objective 1, hepatic ceramide-d18:2/22:0 was highest in cows infused with BA relative to other treatments. For objective 2, plasma free choline concentrations were greater in PA+C cows relative to PA; however, we did not observe this effect with PA+S. Plasma total PC concentrations were similar for all treatments. Regarding the hepatic lipidome, a total of 18 hepatic PC were higher (e.g., PC-16:1/18:2) and 25 PC were lower (e.g., PC-16:0/22:6) with PA+C infusion relative to PA. In addition, 17 PC were higher (e.g., PC-20:3/22:5) and 21 PC were lower (e.g., PC-18:0/22:6) with PA+S infusion relative to PA. For objective 3, hepatic concentrations of many individual saturated PC (e.g., PC-18:0/15:0) were lower with DHA relative to other treatments. Hepatic concentrations of highly unsaturated PC with very-long-chain fatty acids (e.g., PC-14:0/22:6) were higher in DHA-infused cows relative to PA, PA+C, PA+S, or BA. The abomasal infusion of emulsions containing palmitic acid, palmitic acid with choline chloride or serine, behenic acid, or docosahexaenoic acid influence the hepatic ceramide and PC profiles of lactating cows.

Low-density lipoprotein (LDL) ceramide causes insulin resistance in obese diabetic nonruminants. Because previous work suggests that liver-derived ceramide may impair insulin action in postpartum cows, our objectives were to characterize peripartal changes in lipoprotein ceramides. We further studied the effects of prepartum adiposity on lipoprotein ceramide levels. Twenty-eight pregnant Holstein cows (parity = 3.65 ± 1.62) with lean (body condition score, BCS = 2.97 ± 0.16; body weight, BW = 630 ± 55.2 kg; n = 15) or overweight (BCS = 3.93 ± 0.27; BW = 766 ± 46.1 kg; n = 13) body condition 28 d before expected parturition were evaluated. Sampling occurred on d -20.5 ± 1.74, -13.8 ± 1.71, -7.84 ± 4.07, -6.71 ± 1.00, -3.92 ± 0.64, and -1.28 ± 0.61 (before parturition); daily until d 8 postpartum; and on d 10, 12, 14, 21, and 28. Adipose tissue and liver were biopsied on d -7.84 ± 4.07 and 10. Postpartum insulin sensitivity was assessed using the hyperinsulinemic-euglycemic clamp. Lipoprotein fractions were isolated using liquid chromatography. Sphingolipids were quantified using mass spectrometry. Data were analyzed using a mixed model with repeated measures. Overweight cows had a higher BCS and BW at enrollment relative to lean cows, but BCS and BW were similar postpartum. Overweight cows lost more body condition (0.97 ± 0.36 vs. 0.55 ± 0.16 BCS units) and BW (291 ± 67.3 vs. 202 ± 54.5 kg) during transition relative to lean cows. Adipocyte volume and counts declined from prepartum to postpartum (50.4 and 13.7%, respectively), and adipocyte volume was greater (48.2%) in overweight cows prepartum relative to lean cows. Although DMI was comparable between BCS groups, milk yield tended to be greater in overweight cows. Plasma free fatty acid and β-hydroxybutyrate and liver lipid levels were 40, 16, and 37% greater, respectively, in overweight cows compared with lean cows. Glucose infusion rate during the hyperinsulinemic-euglycemic clamp tended to be lower in overweight cows. Ceramide levels within triacylglycerol-rich lipoprotein fractions declined postpartum, whereas LDL ceramide increased postpartum. Overweight cows had lower triacylglycerol-rich lipoprotein C16:0-ceramide levels relative to lean cows. Prepartum LDL C24:0-ceramide levels were greater in overweight cows relative to lean cows. Independent of prepartum adiposity, we concluded that serum LDL ceramide levels are elevated in early-lactation cows experiencing adipose tissue free fatty acid mobilization and hepatic steatosis.

Defects in mitochondrial fatty acid processing are associated with the development of fatty liver disease, inflammation, and insulin resistance in overweight nonruminants. Surplus fatty acids (FA) and defects in FA oxidation favor the accumulation of fatty acylcarnitines (FAC) and the sphingolipid ceramide. Moreover, elevated circulating FAC and ceramide concentrations are inversely related to insulin action. Because we have previously demonstrated that plasma ceramide levels increase during the transition from gestation to lactation, our aim was to determine whether changes in plasma medium- and long-chain FAC levels are related to circulating FA and sphingolipids in peripartal dairy cows. We hypothesized that plasma FAC levels would be higher in overweight cows experiencing increased lipolysis, and that FAC levels would be positively associated with elevations in plasma ceramides. Twenty-one multiparous Holstein cows were grouped according to body condition score (BCS) at d -30 prepartum as lean (BCS3.0; n = 10) or overweight (BCS4.0; n = 11). Blood was collected at d -30, -15, -7, and 4, relative to parturition. Circulating FAC and ceramide levels were determined using liquid chromatography and tandem mass spectrometry. To investigate the potential contributions of sphingomyelin (SM) hydrolysis to ceramide accrual, we also determined plasma SM levels during the peripartum period. Data were analyzed under a mixed model with the fixed effects of adiposity and time, and the random effect of cow. Relative to lean cows, overweight cows had elevated FAC during the transition from gestation to lactation. Circulating FAC levels were positively associated with FA, ceramide, and dihydro-SM levels. Although circulating FAC levels increased in all cows during the peripartum, enhanced prepartum adiposity contributed to a greater rise in plasma FA and FAC. Our results support on-going efforts to determine whether altered mitochondrial FA processing promotes the accumulation of the insulin resistance biomarker ceramide in blood and liver.

The effects of dietary palmitic and stearic acids on feed intake, yields of milk and milk components, and feed efficiency of dairy cows were evaluated in an experiment with a crossover arrangement of treatments with a covariate period. Cows with a wide range of milk production (38 to 65 kg/d) were used to determine if response to fat supplementation varied according to production level. Thirty-two Holstein cows (143 ± 61 d in milk) were assigned randomly to a treatment sequence within level of milk production. Treatments were diets supplemented (2% of diet dry matter) with palmitic acid (PA; 97.9% C16:0) or stearic acid (SA; 97.4% C18:0). Treatment periods were 21 d and cows were fed a nonfat supplemented diet for 14 d immediately before the first treatment period. The final 4d of each period were used for sample and data collection. Milk production measured during the covariate period (preliminary milk yield) was used as the covariate. No interactions were detected between treatment and preliminary milk yield for the production response variables measured. Compared with SA, the PA treatment increased milk fat concentration (3.66 vs. 3.55%) and yield (1.68 vs. 1.59 kg/d), and 3.5% fat-corrected milk yield (47.5 vs. 45.6 kg/d). Treatment did not affect dry matter intake, milk yield, milk protein yield, body weight, or body condition score. Milk protein concentration was lower for PA compared with SA treatment (3.24 vs. 3.29%). The PA treatment increased feed efficiency (3.5% fat-corrected milk yield/dry matter intake) compared with SA (1.48 vs. 1.40). The increase in milk fat yield by PA was entirely accounted for by a 24% increase in 16-carbon fatty acid output into milk. Yields of de novo (3.2%) and preformed fatty acids (2.9%) were only slightly decreased by PA relative to SA. The PA treatment increased plasma concentration of nonesterified fatty acids (96.3 vs. 88.2 μEq/L) and glucose (56.6 vs. 55.7 mg/dL) compared with SA, but insulin and β-hydroxybutyrate were not altered by the treatments. Results demonstrate that palmitic acid is more effective than stearic acid in improving milk fat concentration and yield as well as efficiency of feed conversion to milk. Responses were independent of production level and without changes in body condition score or body weight. Further studies are required to test the consistency of these responses across different types of diets.

Previous work has indicated that dietary palmitic acid (C16:0) may increase milk fat yield. The effect of a dietary C16:0-enriched fat supplement on feed intake, yield of milk and milk components, and feed efficiency was evaluated in an experiment with a crossover arrangement of treatments with 25-d periods. A fermentable starch challenge on the last 4d of each period was utilized as a split-plot within period. Sixteen mid-lactation Holstein cows (249 ± 33 d in milk) were assigned randomly to treatment sequence. Treatments were either a C16:0-enriched (~85% C16:0) fat supplement (fatty acid treatment, FAT, 2% dry matter) or a control diet (CON) containing no supplemental fat. Diets containing dry ground corn grain were fed from d 1 through 21 of each period. On the last 4d of each period, dry ground corn was replaced by high-moisture corn grain on an equivalent dry matter basis to provide a fermentable starch challenge. Response variables were averaged for d 18 to 21 (immediately before the fermentable starch challenge) and d 22 to 25 (during the fermentable starch challenge). We observed no treatment effects on milk yield or milk protein yield. The FAT treatment increased milk fat concentration from 3.88 to 4.16% and fat yield from 1.23 to 1.32 kg/d compared with CON. The FAT treatment decreased dry matter intake by 1.4 kg/d and increased conversion of feed to milk (3.5% fat-corrected milk yield/dry matter intake) by 8.6% compared with CON. The increase in milk fat yield by FAT was entirely accounted for by a 27% increase in 16-carbon fatty acid output into milk. Yields of de novo and preformed fatty acids were not affected by FAT relative to CON. The fermentable starch challenge did not affect milk fat concentration or yield. Results demonstrate the potential for a dietary C16:0-enriched fat supplement to improve milk fat concentration and yield as well as efficiency of conversion of feed to milk. Further studies are required to verify and extend these results and to determine whether responses are similar across different diets and levels of milk production.

Resumen La infeccion por citomegalovirus (CMV) es la infeccion viral mas frecuente en pacientes trasplantados, pero es muy inusual el compromiso del tracto urinario. Solo se han informado unos pocos casos de uretritis por CMV en trasplantados renales. En los informes previos la presentacion clinica mas habitual es nefropatia obstructiva, a menudo en ausencia de enfermedad sistemica, o, algunas veces, puede simular un episodio de rechazo con minimos sintomas obstructivos. Nosotros describimos un caso mas de uretritis por CMV en un paciente trasplantado renal con ureterostomia y una presentacion muy inusual caracterizada por sintomas de infeccion de vias urinarias y ulceracion en la boca de la ureterostomia. El numero incrementado de informes de ureteritis por CMV en trasplantados renales plantea la posibilidad de un aumento en la incidencia de esta complicacion post-trasplante