Energy Metabolism Of Dairy Cows Research Articles

The Effects of Grass Silage Additive Type and Barley Grain Preservation Method on Rumen Function, Microbial Ecology, and Energy Metabolism of Dairy Cows

The effects of grass silage and barley grain preservation methods on dairy cows were evaluated using four Nordic Red dairy cows placed in respiration chambers in a 4 × 4 Latin square. Silage was conserved using a formic acid-based product (AS) or a homofermentative lactic acid bacteria inoculant (IS), while grains were dried (DB) or crimped and ensiled (EB). Fermentation profile of silages and the chemical composition of the mixed diets were very similar. The dietary treatments did not affect feed intake, milk production, and rumen fermentation except molar proportion of butyrate, and energy metabolism. Digestibility of dry matter and organic matter were higher (p < 0.05) and that of crude protein was lower (p < 0.05) for AS than IS. Feeding EB compared to DB decreased (p < 0.05) diet organic matter and starch digestibility. The cows receiving AS tended (p = 0.06) to emit more methane per day than those receiving IS, but methane yield and intensity were not different between dietary treatments. Bacteria alpha diversity was higher (p < 0.01) in barley samples than grass silages and was not affected by the diet in rumen samples. All freshly prepared rations were dominated by Lactobacillaceae, Erwiniaceae, and Pseudomonadaceae but rations based on AS than IS remained more stable over 2 days. In conclusion, grass silage and barley grain preservation methods did not affect the measured parameters in dairy cows and the preservation method can be selected based on practical on-farm factors.

Feeding rumen-protected Capsicum oleoresin to dairy cows during the transition period and early lactation: Effects on nutrient digestibility, blood metabolites, and performance

Capsicum oleoresin (CAP), a plant extract derived from chili pepper plants, contains bioactive compounds reported to influence the energy metabolism in dairy cows. This study investigated the effects of feeding rumen-protected CAP during the transition period and early lactation on total-tract apparent digestibility of nutrients, serum metabolites [glucose, urea-N, non-esterified fatty acids (NEFA), and beta-hydroxybutyrate (BHB)], and milk yield and composition in dairy cows. Twenty-four healthy Holstein cows (12 multiparous and 12 primiparous) were enrolled to this study at − 4 wk from the expected calving date. Animals were blocked according to parity and expected calving date. Cows within block were randomly assigned to a control (CON) treatment without feed additives or to the CAP treatment, dietary supply of rumen-protected CAP at 100 mg/d. Pre-partum and post-partum data were analyzed separately. Dry matter intake and related dietary variables were not affected by treatments during the pre- or post-partum period. No differences were detected on digestibility of DM, organic matter, or crude protein during the pre-partum and post-partum periods. Serum metabolite concentrations were similar between treatment groups either during the pre-partum or post-partum periods. Milk yield tended to be greater (P = 0.07) in cows fed CAP than CON (31.7 and 28.5 kg/d, respectively). Fat-corrected milk yield was increased (P = 0.03) by feeding CAP. Milk fat yield (1.20 vs. 1.05 kg/d) and feed efficiency (1.72 vs. 1.50 kg milk/kg DM intake) were significantly greater (P ≤ 0.03) in cows fed CAP than CON. Feeding rumen-protected CAP at 100 mg/d during the transition period and early lactation increased fat-corrected milk yield, and improved milk fat and feed efficiency of dairy cows.

Comparison of Glucose Levels in Blood Samples Taken from Coccygeal, Jugular and Mammary Vein of Cows in Lactation

Blood glucose level is one of the most commonly used parameters in assessing the energy metabolism in dairy cows. The presented study aimed to compare the glucose concentrations in blood samples taken from the coccygeal vein, jugular vein, and mammary vein from the same animals at the same time. Healthy Holstein-Friesian dairy cows (n=25) in their second and third lactation were selected for the study. The blood samples were taken from the coccygeal vein, jugular vein, and V. subcutanea abdominis (mammary vein) at the same time from each animal. To analyze blood glucose, Free Style Optium Blood Glucose Test Strip (Abbott, Istanbul, TURKIYE) was used. In comparison to the blood taken from both the jugular vein and coccygeal vein, glucose levels in blood samples taken from the mammary vein were significantly low (P<0.001). As a result, the determination of glucose levels in blood samples taken from the mammary veins may cause erroneous interpretations. Therefore, the mammary vein for blood glucose must not be used as a sampling site.

O161 Hepatic energy metabolism of dairy cows in grazing systems with or without environmental control during lactation

O161 Hepatic energy metabolism of dairy cows in grazing systems with or without environmental control during lactation

Effects of intracerebroventricular anandamide administration on feed intake and milk yield of dairy cows

Among the endocannabinoids, N-arachidonylethanolamide (AEA; anandamide) plays a key role in regulating energy homeostasis and energy intake. Recent studies suggest the existence of a peripheral mechanism by which AEA increases feed intake in the short term and modulates whole-body energy metabolism in dairy cows. Here, we aimed to test the hypothesis that AEA has a long-lasting central effect in increasing feed intake that leads to an increase in milk yield of dairy cows. In the present pilot study, 3 nonpregnant Holstein dairy cows were equipped with an intracerebroventricular (i.c.v.) catheter. Cows were deprived from feed for 2 h and received either no injection or an i.c.v. injection of either 12 μg of AEA or DMSO (control), followed by measurement of feed intake for 10 h and milk yield. Administration of AEA increased 10-h dry matter intake (DMI) by between 1.13 and 2.06 kg, whereas 22-h DMI was only marginally altered. However, compared with the control treatment, AEA reduced daily milk yield by 0.3 to 1.4 L/d in all 3 cows. The results demonstrate that i.c.v. administration of 12 µg of AEA increased 10-h DMI but decreased daily milk yield by a central mechanism.

Effects of endocannabinoids on feed intake, stress response and whole-body energy metabolism in dairy cows

Endocannabinoids, particularly anandamide (AEA) and 2-arachidonoylglycerol (2-AG), are instrumental in regulating energy homeostasis and stress response. However, little is known about the endocannabinoid system (ECS) in ruminants, although EC could improve dairy health and productivity, at least by increasing feed intake. In this study, we report if intraperitoneal (i.p.) AEA and 2-AG administration affects feed intake, whole-body macronutrient metabolism, isolation and restraint stress, and whether diet composition modulates circulating endocannabinoid concentrations in cows. Twenty Simmental cows in late lactation were fed a grass silage and a corn silage based diet. On each diet, cows received daily i.p. injections with either AEA (5 µg/kg; n = 7), 2-AG (2.5 µg/kg; n = 6) or saline (n = 7) for 8 days. Endocannabinoid administration for 5 days under free-ranging (non-stressed) conditions had no effect on feed intake or energy balance, but attenuated the stress-induced suppression of feed intake when housing changed to individual tie-stalls without social or tactile interaction. Endocannabinoids increased whole-body carbohydrate oxidation, reduced fat oxidation, and affected plasma non-esterified fatty acid concentrations and fatty acid contents of total lipids. There was no effect of endocannabinoids on plasma triglyceride concentrations or hepatic lipogenesis. Plasma AEA concentrations were not affected by diet, however, plasma 2-AG concentrations tended to be lower on the corn silage based diet. In conclusion, endocannabinoids attenuate stress-induced hypophagia, increase short-term feed intake and whole-body carbohydrate oxidation and decrease whole-body fat oxidation in cows.

Effects of exogenous Fibroblast Growth Factor-21 on characteristic parameters related to energy metabolism in dairy cows

Negative energy balance (NEB) is a common pathological foundation of fatty liver and ketosis. Liver and fat tissue are the major organs of lipid metabolism, which is also a key metabolic pathway that regulates NEB development during the perinatal period. Fibroblast growth factor-21 (FGF-21) is a protein hormone that plays an important role in adipose lipid metabolism and liver gluconeogenesis. Our aim was to investigate the effects of exogenous FGF-21 on characteristic parameters related to energy balance in dairy cows. Ten non-pregnant, non-lactating Holstein-Friesian dairy cows were randomly allocated into two groups. The interventions were exogenous FGF-21 injection group received 1 ug/kg BW (body weight) of recombinant bovine FGF-21 by intravenous injection, and control group received physiological saline injections by intravenous injection. In comparison to saline injections, intravenous injections of FGF-21 either increased or tended to increase concentrations of FGF-21 (p < 0.05), BHBA (p < 0.05), adiponectin, leptin and HDL-C. FGF-21 injections decreased or tended to decrease concentrations of insulin, glucose, glucagon (p < 0.05), ALT/GPT (p < 0.05), AST/GOT (p < 0.05), urate, creatinine (p < 0.05), BUN, triglyceride (p < 0.05), T-CHO and LDL-C (p < 0.05). The results indicate that FGF-21 has only negative effects on the metabolites and metabolic hormones related to NEB in serum of dairy cows, but it has more beneficial effects on prominent adipokines, liver function index, renal function index, lipoprotein profiles related to the pathological changes that occurred in NEB.

Analyse of Relationships Between Some Milk Indicators of Cow Energy Metabolism and Ketosis State

Good health is important for animal reproduction and support of foodstuff chain quality and safety. Milk is suitable for noninvasive monitoring. Analyses of milk composition and result interpretation along environmental conditions and physiological principles plays important role in health control. Ketosis is a disorder of energy metabolism in dairy cows. It deteriorates milk yield (MY) and quality and animal reproduction and can have a fatal impact. Aim was to analyse relationships between milk energy metabolism indicators as acetone (AC) and component quotients which can serve in health control and estimate their thresholds. AC and fat/lactose (F/L) and fat/crude protein (F/CP) ratio could represent good ketosis indicators. There were 960 individual milk samples from the Holstein (H) and Czech Fleckvieh (CF) dairy cows (1:1). Their whole lactations, first third of lactations (FTL) and summer and winter seasons were analysed. Lactation MY of included herds (7) varied from 5,500 to 10,000 kg. Milk AC levels did not differ (P > 0.05) between H and CF breed in whole lactation but differed in FTL (H 3.88 and CF 2.72 mg.l–1; P < 0.05). This difference 1.16 mg.l–1is equal to 29.9 % and this is not too much essential. The F/L ratio was not affected (P > 0.05) by parity and season in whole lactation but was influenced (P < 0.01 and < 0.05) in this way during FTL. As maximum there can be explained only 17.8 % of variability (correlation index 0.42; P < 0.001) in log AC values by F/L quotient variability for CF in FTL in summer season. As maximum there can be explained up to 84.4 % of variations (correlation index 0.92; P < 0.001) in F/CP values by F/L quotient variations for H in FTL in summer season. Equations were used for model calculation of AC and F/L cut‑off limits to subclinical ketosis indication in FTL period. These were from 2.05 to 3.29 mg.l–1about AC and from 0.84 to 0.87 about F/L according to breeds (CF and H) and lactation parity (1stand others). The results can be used in methods of cow health problem identification, prevention, treatment and troubleshooting during lactation.

Prepartal overfeeding alters the lipidomic profiles in the liver and the adipose tissue of transition dairy cows

Physiological adaptations in the energy metabolism of dairy cows during the periparturient period are partly mediated by insulin resistance (IR), which may subsequently induce metabolic disorders postpartum. The molecular mechanisms underlying IR in dairy cows are largely unknown. This study aimed to find a novel insight into the molecular mechanisms underlying IR in dairy cows during the periparturient period by analyzing the effects of prepartal overfeeding on the lipidomic profiles in the liver and adipose tissue (AT). Sixteen cows were allocated to controlled-energy and high-energy feeding groups. Lipidomic profiling was conducted on liver and adipose tissue samples collected at 8 days prior to the predicted parturition, and 1 day (only AT) and 9 days after the actual parturition. Five ceramides (Cers) were identified to be significantly increased by prepartal overfeeding in AT in the analysis of the variance between groups within time points. Principal component-linear discriminant analysis showed that lipidomic profiles between the feeding groups were mainly characterized by phosphatidylcholines (PC), phosphatidylethanolamines (PE), lysophophosphatidylcholines (LysoPC), and lysophosphatidylethanolamines (LysoPE) in the liver, and by Cer, PE, and phosphatidylinositols (PI) in AT. Lipid class levels indicated that prepartal overfeeding elevated the concentration of PE, PI, LysoPC, LysoPE, and sphingomyelin in the liver, and increased the concentration of Cer in AT during the periparturient period. Prepartal overfeeding significantly altered the concentrations of various sphingolipids, phospholipids, and lysophospholipids in the liver and AT of dairy cows during the periparturient period.

Effects of combined supplementation with plant bioactive lipid compounds and biotin on ruminal fermentation, body condition and energy metabolism in transition dairy cows

The negative energy balance during early lactation often leads to excessive mobilization of body reserves and increases the risk for ketosis. The present study proceeded from the hypothesis that combined supplementation of a commercial blend of plant bioactive lipid compounds (essential oils) plus biotin throughout the transition period could have a positive impact on energy metabolism in dairy cows postpartum, partly, by improving ruminal production of propionate as a precursor for hepatic gluconeogenesis. Thirty five multiparous Holstein-Friesian dairy cows were divided into two groups. The control group (CON; n=16) received a total mixed ration plus individual concentrate feeding (increasing gradually after parturition up to 6kg/d at peak lactation). The other group received the same diet supplemented with 1.3g/d plant bioactive lipid compounds and 33mg/d biotin (PBLC+B, n=19) from day (D)-21 before until D37 after parturition. Assessment of body condition score (BCS) and back fat thickness (BFT), as well as collection of blood serum samples was performed weekly until D58. Samples of ruminal fluid were acquired by stomach tube at D37 and D58. Cows in the PBLC+B group maintained better body condition after calving; BCS was higher than CON at days (D)23, D37 and D44 (P≤0.05), and tended to be higher on days D16, D30, D51 and D58 (P≤0.1). Towards the end of the study period, BFT was also numerically higher in PBLC+B cows (P=0.107 at D44 and D51). Serum concentrations of glucose, β-hydroxybutyric acid, non-esterified fatty acids, triglycerides, cholesterol, urea, aspartate transaminase, cholesterol, γ-glutamyltranspeptidase and glutamate dehydrogenase did not differ between groups. Cows in the PBLC+B group showed a faster decrease of serum bilirubin after parturition (P≤0.05 to CON at D30). Propionate concentration in ruminal fluid was higher in PBLC+B compared to CON at D37 (P≤0.05) but not D58 after parturition. It is concluded that combined addition of plant bioactive lipid compounds and biotin to the diet of transition dairy cows led to improved ruminal propionate fermentation and decreased loss of body condition postpartum. Differences in serum bilirubin may indicate improved hepatic metabolism in PBLC+B cows. Therefore, a mix of plant bioactive lipid compounds and biotin may ameliorate the metabolic challenges in the transition period of dairy cows.

Variable liver fat concentration as a proxy for body fat mobilization postpartum has minor effects on insulin-induced changes in hepatic gene expression related to energy metabolism in dairy cows

The liver plays a central role in adaptation for energy requirements around calving, and changes in the effects of insulin on hepatic energy metabolism contribute to metabolic adaptation in dairy cows. Hepatic insulin effects may depend on body fat mobilization. The objective of this study was to investigate the effects of insulin on the hepatic gene expression of enzymes involved in energy metabolism and factors related to nutrition partitioning in cows with high and low total liver fat concentration (LFC) after calving. Holstein cows were retrospectively grouped according to their LFC after calving as a proxy for body fat mobilization. Cows were classified as low (LLFC; LFC <24% fat/dry matter; n = 9) and high (HLFC; LFC >24.4% fat/dry matter; n = 10) fat-mobilizing after calving. Euglycemic-hyperinsulinemic clamps [6 mU/(kg × min) of insulin for 6 h] were performed in wk 5 antepartum (ap) and wk 3 postpartum (pp). Before and at the end of the euglycemic-hyperinsulinemic clamps, liver biopsies were taken to measure the mRNA abundance of enzymes involved in carbohydrate and lipid metabolism, expression related to the somatotropic axis, and adrenergic and glucocorticoid receptors. The mRNA abundance of pyruvate carboxylase, cytosolic phosphoenolpyruvate carboxykinase (PEPCK; PCK1), acyl-CoA-dehydrogenase very long chain (ACADVL), and hydroxyl-methyl-glutaryl-CoA-synthase 1 increased, but the mRNA abundance of solute carrier family 2 (SLC2A2 and SLC2A4), growth hormone receptor 1A (GHR1A), insulin-like growth factor 1 (IGF1), sterol regulatory element binding factor 1, adrenoceptor α 1A, and glucocorticoid receptor decreased from ap to pp. Insulin treatment was associated with decreased PCK1, mitochondrial PEPCK, glucose-6-phosphatase, propionyl-CoA-carboxylase α, carnitine-palmitoyl-transferase 1A, ACADVL, and insulin receptor mRNA, but increased IGF1 and SLC2A4 mRNA ap and pp and GHR1A mRNA pp. The mRNA abundance of SLC2A4 was greater, and the mRNA abundance of GHR1A and IGF1 tended to be lower in LLFC than in HLFC. Administration of insulin, albeit at a supraphysiological dose, was associated with inhibition of gene expression related to glucose production and β-oxidation, but we observed variable effects in the degree of insulin depression of individual genes. Insulin status is important for regulation of nutrient partitioning, but different LFC pp had very little influence on changes in hepatic gene expression following administration of insulin.

Effects of rutin and buckwheat seeds on energy metabolism and methane production in dairy cows

Flavonoids are secondary plant metabolites with several health promoting effects. As dairy cows often suffer from metabolic imbalance and health problems, interest is growing in health improvements by plant substances such as flavonoids. Our group has recently shown that the flavonoids quercetin and rutin (a glucorhamnoside of quercetin) are bioavailable in cows when given via a duodenal fistula or orally, respectively, affect glucose metabolism, and have beneficial effects on liver health. Furthermore, flavonoids may reduce rumen methane production in vitro through their antibacterial properties. To test the hypothesis that rutin has effects on energy metabolism, methane production, and production performance in dairy cows, we fed rutin trihydrate at a dose of 100mg/kg of body weight to a group of 7 lactating dairy cows for 2wk in a crossover design. In a second experiment, 2 cows were fed the same ration but were supplemented with buckwheat seeds (Fagopyrum tartaricum), providing rutin at a dose comparable to the first experiment. Two other cows receiving barley supplements were used as controls in a change-over mode. Blood samples were taken weekly and respiration measurements were performed at the end of each treatment. Supplementation of pure rutin, but not of rutin contained in buckwheat seeds, increased the plasma quercetin content. Methane production and milk yield and composition were not affected by rutin treatment in either form. Plasma glucose, β-hydroxybutyrate, and albumin were increased by pure rutin treatment, indicating a possible metabolic effect of rutin on energy metabolism of dairy cows. In addition, we did not show that in vivo ruminal methane production was reduced by rutin. In conclusion, we could not confirm earlier reports on in vitro methane reduction by rutin supplementation in dairy cows in established lactation.

Increasing serotonin concentrations alter calcium and energy metabolism in dairy cows.

A 4×4 Latin square design in which varied doses (0, 0.5, 1.0, and 1.5 mg/kg) of 5-hydroxy-l-tryptophan (5-HTP, a serotonin precursor) were intravenously infused into late-lactation, non-pregnant Holstein dairy cows was used to determine the effects of serotonin on calcium and energy metabolism. Infusion periods lasted 4 days, with a 5-day washout between periods. Cows were infused at a constant rate for 1 h each day. Blood was collected pre- and 5, 10, 30, 60, 90, and 120 min post-infusion, urine was collected pre- and post-infusion, and milk was collected daily. All of the 5-HTP doses increased systemic serotonin as compared to the 0 mg/kg dose, and the 1.0 and 1.5 mg/kg doses increased circulating glucose and non-esterified fatty acids (NEFA) and decreased beta-hydroxybutyrate (βHBA) concentrations. Treatment of cows with either 1.0 or 1.5 mg/kg 5-HTP doses decreased urine calcium elimination, and the 1.5 mg/kg dose increased milk calcium concentrations. No differences were detected in the heart rates, respiration rates, or body temperatures of the cows; however, manure scores and defecation frequency were affected. Indeed, cows that received 5-HTP defecated more, and the consistency of their manure was softer. Treatment of late-lactation dairy cows with 5-HTP improved energy metabolism, decreased loss of calcium into urine, and increased calcium secretion into milk. Further research should target the effects of increasing serotonin during the transition period to determine any benefits for post-parturient calcium and glucose metabolism.

Short communication: Plasma concentration of glucose-dependent insulinotropic polypeptide may regulate milk energy production in lactating dairy cows

In dairy cows, an increase in plasma concentration of glucose-dependent insulinotropic polypeptide (GIP) is associated with an increase in metabolizable energy intake, but the role of GIP in energy partitioning of dairy cattle is not certain. The objective of this study was to examine the relationship between plasma GIP concentrations and energy partitioning toward milk production. Four mid-lactation, primiparous, rumen-fistulated Holstein-Friesian cows were fed a control diet of 55% forage and 45% concentrate [dry matter (DM) basis] in a 4×4 Latin square design with 4-wk periods. The 4 treatments were (1) control diet fed at 1000 and 1600h, and (2) once-daily (1000h) feeding, (3) twice-daily (1000 and 1600h) feeding, and (4) 4 times/d (1000, 1600, 2200 and 0400h) feeding of the control diet plus 1 dose (1.75kg on a DM basis at 0955h) into the rumen of supplemental vegetable proteins (Amino Green; SCA NuTec Ltd., Thirsk, UK). Measurements of respiratory exchange and energy balance were obtained over 4d during the last week of each period while cows were housed in open-circuit respiration chambers. Blood was collected from the jugular vein every 30min for 12h, using indwelling catheters, starting at 0800h on d 20 of each period. Plasma GIP concentration was measured in samples pooled over each 5 consecutive blood samplings. The relationships between plasma GIP, DM intake, heat production, respiratory quotient (RQ), milk yield, and milk energy output were analyzed using linear correlation procedures, with metabolizable intake as a partial variant. Plasma GIP concentration was not correlated with heat production, or milk yield, but was positively correlated with milk energy yield (correlation coefficient=0.67) and negatively correlated with RQ (correlation coefficient=−0.72). The correlations between GIP with RQ and milk energy output do not imply causality, but support a role for GIP in the regulation of energy metabolism in dairy cows.

Milk production is unaffected by replacing barley or sodium hydroxide wheat with maize cob silage in rations for dairy cows

Starch is an important energy-providing nutrient for dairy cows that is most commonly provided from cereal grains. However, ruminal fermentation of large amounts of easily degradable starch leads to excessive production and accumulation of volatile fatty acids (VFA). VFA not only play a vital role in the energy metabolism of dairy cows but are also the main cause of ruminal acidosis and depressed feed intake. The aim of the present study was to compare maize cob silage (MCS) as an energy supplement in rations for dairy cows with highly rumen-digestible rolled barley and with sodium hydroxide wheat (SHW), which has a higher proportion of by-pass starch than barley. Two studies were carried out: (1) a production study on 45 Danish Holstein cows and (2) an intensive study to determine digestibilities, rumen fermentation patterns and methane emission using three rumen-cannulated Danish Holstein cows. Both studies were organised as a 3×3 Latin square with three experimental periods and three different mixed rations. The rations consisted of grass-clover silage and maize silage (~60% of dry matter (DM)), rapeseed cake, soybean meal, sugar beet pulp and one of three different cereals as a major energy supplement: MCS, SHW or rolled barley (~25% of DM). When MCS replaced barley or SHW as an energy supplement in the mixed rations, it resulted in a lower dry matter intake; however, the apparent total tract digestibilities of DM, organic matter, NDF, starch and protein were not different between treatments. The energy-corrected milk yield was unaffected by treatment. The fat content of the milk on the MCS ration was not different from the SHW ration, whereas it was higher on the barley ration. The protein content of the milk decreased when MCS was used in the ration compared with barley and SHW. From ruminal VFA patterns and pH measures, it appeared that MCS possessed roughage qualities with respect to rumen environment, while at the same time being sufficiently energy rich to replace barley and SHW as a major energy supplement for milk production. The environmental impact, expressed as methane emissions, was not different when comparing MCS, SHW and barley.

Effect of conjugated linoleic acid supplementation on body composition, body fat mobilization, protein accretion, and energy utilization in early lactation dairy cows

The objective of the study was to investigate the effects of trans-10,cis-12 and cis-9,trans-11 conjugated linoleic acid (CLA) supplementation on body composition, mobilization or accretion of body fat and protein mass, as well as the energy metabolism of dairy cows during the first 105 d in milk (DIM). For this purpose, a comparative slaughter experiment was conducted with 25 primiparous German Holstein cows. The experiment started at 1 DIM with the slaughter of 5 animals of an initial group receiving no CLA supplement. The remaining animals were fed a CLA supplement (n=10) or a stearic acid-based control fat supplement (CON; n=10) from 1 DIM up to slaughter. After 42 DIM, 5 more cows from each treatment (42-CLA and 42-CON) were slaughtered. The remaining 5 cows in each treatment were slaughtered after 105 DIM (105-CLA and 105-CON). The animals of the CLA groups consumed 6.0g/d of trans-10,cis-12 CLA and 5.7g/d of cis-9,trans-11 CLA. During the slaughter process, the empty body mass was recorded and partitioned into 9 fractions (meat, bone, offal, hide, mammary gland, retroperitoneal fat, omental fat, mesenteric fat, and s.c. fat). The fractions were analyzed for dry matter, ether extract, crude protein, and ash to calculate the body composition of the empty body mass at the different slaughter times. The principle of the comparative slaughter technique was applied to estimate body fat or protein mobilization and accretion in the viewed periods from 1 DIM until 42 and 105 DIM. The heat production (HP) was calculated by subtracting the energy in milk and energy changes in body mass from the metabolizable energy intake. The body composition was not affected by CLA supplementation. However, the mobilization of body fat mass from 1 until 42 DIM was 24.1kg in the 42-CON group and 14.3kg in the 42-CLA group. This resulted in a trend to lower body mass (fat and protein) mobilization of 10.5kg in the 42-CLA group. Energy mobilization from body mass was 21.2 MJ/d in the 42-CON and 11.5 MJ/d in the 42-CLA group. The HP was unchanged for the 42-CON and 42-CLA group with 123.0 and 116.9 MJ/d, respectively. From 1 until 105 DIM, the protein accretion was 4.3kg and the daily energy retention in body protein was 1.0 MJ higher for CLA-supplemented cows. The HP was decreased in this period for the 105-CLA group (115.5 MJ/d) as compared with the 105-CON group (125.9 MJ/d). Overall, the trend for a decreased body mass mobilization suggested a protective effect of CLA supplementation against excessive use of body reserves within 42 DIM. Continuous CLA supplementation until 105 DIM increased protein accretion. The effects on body mass mobilization and protein accretion in combination with the decreased HP in the CLA-fed cows suggested a more efficient utilization of metabolizable energy in CLA-supplemented early lactation dairy cows.

A Meta-Analysis of the Impact of Monensin in Lactating Dairy Cattle. Part 1. Metabolic Effects

A meta-analysis of the impact of monensin on metabolism of dairy cattle was conducted following a search of the literature. A total of 59 studies with monensin feeding in dairy cattle were identified in which 30 papers and 45 trials contained metabolic data. The β-hydroxybutyrate (BHBA) data were obtained from over 4,000 cows and 115 trial sites. Data for each trial were extracted and analyzed using meta-analysis software in Stata. Estimated effect sizes of monensin were calculated on blood concentrations of BHBA, acetoacetate, nonesterified fatty acids (NEFA), glucose, cholesterol, urea, calcium, insulin, and milk urea. Monensin use in lactating dairy cattle significantly reduced blood concentrations of BHBA 13%, acetoacetate 14%, and NEFA 7%. Monensin increased glucose 3% and urea 6%. Monensin had no significant effect on cholesterol, calcium, milk urea, or insulin. Heterogeneity was significant for BHBA and cholesterol [I2 (measure of variation beyond chance) = 37 and 54%, respectively]; therefore, random effects models were used for those analytes. Publication bias existed with the monensin effect on BHBA, with a tendency for studies to be published if there was a significant reduction in this ketone. Meta-regression analysis of the effect sizes obtained from the metabolic data showed that method of delivery, timing of administration, stage of lactation, and diet were influential in modifying effect size of monensin treatment. Use of top dress or delivery via a controlled release capsule reduced the magnitude of effect on BHBA (coefficient +0.353); however, top dress use compared with controlled release capsule or total mixed ration enhanced the monensin effect on glucose (coefficient +0.296). There was a greater impact with monensin on reducing BHBA in early lactation (coefficient −0.151) and in pasture-based trials (coefficient −0.194). Use of monensin in both the pre- and postcalving periods was associated with an enhanced impact on NEFA (coefficient −0.254). Monensin had less impact on serum glucose in the pre-calving time period (coefficient −0.237). These findings demonstrate an improvement in the energy metabolism of dairy cows supplemented with monensin.

Effect of Isoflupredone Acetate With or Without Insulin on Energy Metabolism, Reproduction, Milk Production, and Health in Dairy Cows in Early Lactation

Glucocorticoids are commonly used to treat cows with clinical ketosis and fatty liver disease, but their use is controversial. The objectives of the present study were to investigate the effects of isoflupredone acetate alone or with insulin on the energy metabolism of dairy cows in early lactation in a large double-blind, randomized clinical trial. A total of 1,162 Holstein cows and first-lactation heifers were randomly assigned to receive 1 of 3 treatments between the day of parturition and 8 DIM: group A, 20mg i.m. injection of isoflupredone and 100 units of insulin; group B, 20mg i.m. injection of isoflupredone; group C (control group), 10mL i.m. injection of sterile water. Treatments were randomized across 24 dairy farms located near Guelph, Ontario, Canada. Serum samples obtained at the time of treatment and at wk 1 and 2 following treatment were analyzed for β-hydroxybutyrate, nonesterified fatty acids, glucose, calcium, potassium, sodium, and chloride. Cows were assigned a body condition score at the time of enrollment. Data were analyzed using a repeated-measures mixed model that accounted for the effects of parity and body condition score, and the random effects of cow and farm. Cows that received isoflupredone with insulin and isoflupredone alone had higher β-hydroxybutyrate and nonesterified fatty acid concentrations 1 wk after treatment compared with control cows. Cows that received isoflupredone acetate plus insulin had lower glucose concentrations at 1 wk after treatment. Calcium concentrations 1 wk after treatment were lower for cows that received isoflupredone and insulin or isoflupredone only compared with control cows. Serum sodium, potassium, and chloride concentrations were not influenced by treatment. The effect of treatment on the proportion of cows with subclinical ketosis was evaluated with a logistic regression model. Over the 2 wk following treatment, a significant increase in the prevalence of subclinical ketosis was observed in the isoflupredone plus insulin group relative to the control group. Among 972 cows that were not ketotic at enrollment, cows that received isoflupredone acetate plus insulin or isoflupredone acetate only were, respectively, 1.72 and 1.59 times more likely than control cows to develop subclinical ketosis 1 wk after treatment. There were no treatment effects on test-day milk production, milk fat and protein percentages, or the intervals from calving to first insemination or pregnancy.

Production Responses of Dairy Cows to Dietary Supplementation with Conjugated Linoleic Acid (CLA) During the Transition Period and Early Lactation1,2

Holstein cows (n = 30) entering second or greater lactation were fed fat supplements (90 g/d of fatty acids) consisting of Ca salts of either palm fatty acid distillate (control) or a mixture of palm fatty acid distillate and mixed isomers of conjugated linoleic acid (CLA, 30.4 g/d) from 2 wk prepartum through 20 wk postpartum to determine whether CLA would inhibit milk fat synthesis during early lactation and, in turn, affect energy metabolism of dairy cows during the transition period and early lactation. Feeding CLA did not affect DMI or plasma concentrations of glucose, nonesterfied fatty acids, or β-hydroxbutyrate during the prepartum period and did not affect postpartum DMI. Feeding CLA reduced milk fat content by 12.5% during early lactation; however, cows fed CLA tended to produce approximately 3 kg/d more milk during the first 20 wk of lactation. Feeding CLA tended to decrease the contribution of short- and medium-chain (C≤16) fatty acids to milk fat. Changes in milk yield, milk fat content, and milk fatty acid composition were not apparent until after the second week of lactation. Yield of 3.5% fat-corrected milk, milk protein content, milk protein composition, and calculated energy balance were not affected by treatment. Postpartum concentrations of glucose, nonesterfied fatty acids, and β-hydroxbutyrate in plasma and hepatic content of glycogen and triglycerides were similar between treatments. These data imply that with CLA treatment in early lactation, dairy cows decreased milk fat synthesis and appeared to respond by partitioning more nutrients toward milk synthesis rather than improving net energy balance.

Energy metabolism of dairy cows fed on grass

Production performance of grass-fed dairy cows is often lower than expected from the estimated energy supply. To explain the overestimation of the energy content of grass for dairy cows, data from energy balance trials from three different laboratories (Wageningen, Lelystad and Hillsborough) were collected. The trials in Wageningen and Lelystad were carried out in the 1970s and those in Hillsborough in the 1990s. Regression analyses were carried out with the complete data set as well as per laboratory to identify differences per laboratory. Average net maintenance requirements per kg 3/4 (NE m) were 0.573 MJ, whereas the efficiency of metabolizable energy utilization for lactation ( k l) was 0.777. When NE m was fixed at the presently used value of 0.293 MJ/kg 3/4, k l was 0.60. Between-laboratory NE m varied between 0.294 (Lelystad) and 0.786 MJ/kg 3/4 (Hillsborough), whereas k l varied between 0.57 (Lelystad) and 0.84 (Hillsborough). For Wageningen and Hillsborough, NE m was high, whilst k l was also high. With the intercept fixed at 0.293 MJ/kg 3/4, efficiency varied between 0.53 (Hillsborough) and 0.62 (Wageningen). The k l and NE m are interrelated. Based on these data we surmise that the maintenance requirements for grass-fed dairy cows are 10% higher than presently assumed, with no change in k l.