Dairy Cows In Early Lactation Research Articles

Diagnostic accuracy of milk oxidation markers for detection of subclinical mastitis in early lactation dairy cows

Subclinical mastitis is one of the most important infectious diseases, and higher levels of oxidative stress in the peritpartum period were related to higher risk of mastitis. The objective of the present study was to evaluate the diagnostic value of milk oxidative stress variables in early lactation of dairy cow with subclinical mastitis. A total of 925 milk samples from quarters of cows during (7 ± 3) days post-calving from two dairy herds were included in the present study. Bacterial culture, somatic cell count (SCC), DTNB (dithiobis nitrobenzoic acid for oxidative capacity), and FRAP (ferric reducing antioxidant power for antioxidatant capacity) have been assayed. Receiver-operating characteristic (ROC) analysis was used to assess the accuracy diagnostic value of each test using bacterial culture as gold standard. The accuracy of DTNB assay was comparable to that observed for SCC (AUC = 0.724 vs. AUC = 0.739). Sensitivity and specificity of DTNB at the concentration of 2.00 μmol s−1 were also comparable to those for SCC at 165 × 103 SCCml−1 (59.1 and 80.7% vs. 56.9 and 82.2%, respectively). Concentrations of both DTNB and FRAP were significantly higher in milk samples of quarters infected with S. aureus, when compared to non-infected quarters and quarters infected with other bacteria. The results showed that colorimetric measurement of DTNB could be a valuable indicator of subclinical mastitis, especially infection caused by S. aureus.

PSI-11 Anti-inflammatory treatment modifies epigenetics changes to muscle tissue caused by altered nutrient demand in early lactation dairy cows

Abstract Short-term treatment with non-steroidal anti-inflammatory drugs (NSAIDs) has been shown to alter whole-lactation milk yield; perhaps because epigenetic modifications are responsible for long-term effects, although mechanisms are unclear. Altered nutrient demand due to fasting or exercise in other species has been shown to affect DNA methylation in muscle tissue. Our objective was to determine if NSAID treatment or alterations to nutrient demand have epigenetic effects on muscle tissue in early lactation. In this study, 33 multiparous Holstein cows were enrolled at parturition and randomly assigned to milking frequency (MF; 1× or 3×/day), and either sodium salicylate (SS; 2.3 g/L administered via drinking water) or control (CTL; molasses carrier alone) treatment in a 2×2 factorial design, beginning ~24 h postpartum. Milking frequency treatments were designed to alter nutrient demand, and 3× milked increased milk yield by 24%. After 5 days of treatment, tissue biopsies were collected from the Longissimus dorsi muscle and snap-frozen. DNA was isolated and global methylation (GM) was assessed with a 5-methylcytosine enzyme-linked immunosorbent assay. An interaction between MF and SS treatment was detected (P = 0.02), with GM of muscle tissue decreased by more frequent milking only in the CTL cows (4.9 and 1.4 ± 1.0% of DNA methylated for 1× and 3×, respectively; P < 0.001). No effect of MF was detected in SS-treated cows (2.9 and 2.4 ± 1.0% of DNA methylated for 1× and 3×, respectively; P > 0.1). Observed changes to DNA methylation in muscle tissue due to altered nutrient supply are consistent with results reported after fasting and exercise. Additionally, increased demand for milk component precursors in 3×-milked cows may alter the availability of methyl donors for DNA methylation. Our data support a link between SS and epigenetic changes, but further research is needed to determine how SS may have altered the muscle DNA methylation response to nutrient demand.

Liver phosphorus content and liver function in states of phosphorus deficiency in transition dairy cows.

Phosphorus (P) deficiency in early lactating dairy cows is receiving increased attention because of incentives aiming at curtailing environmental pollution with P by reducing dietary P in ruminant diets. An in-vitro study using bovine hepatocytes incubated for 7 days with phosphate (Pi) concentrations of 0.9, 1.8 or 2.7 mmol/L, and an in-vivo study feeding late pregnant dairy cows diets with either adequate (0.28% and 0.44% in DM ante-partum and post-partum respectively) or low P content (0.15% and 0.20% in DM ante-partum and post-partum respectively) from 4 weeks before to 4 weeks after calving were conducted to explore effects of P deprivation on liver function. In vitro the relative abundance of mRNA of key enzymes of the carbohydrate metabolism in incubated hepatocytes and liver metabolites in culture medium were determined. In vivo health and productivity of experimental cows on low and adequate dietary P supply were monitored, and liver tissue and blood samples were obtained repeatedly. Liver tissue was assayed for its triacylglycerol-, mineral and water content as well as for the relative abundance of mRNA of enzymes of the carbohydrate-, fat- and protein metabolism. Reduced Pi-availability was not associated with altered enzyme transcription rates or metabolic activity in-vitro. The most prominent clinical finding associated with P deprivation in-vivo was feed intake depression developing after the first week of lactation. Accordingly cows on low P diets had lower milk yield and showed more pronounced increases in liver triacylglycerol after calving. Although the liver P content decreased in P deficient cows, neither negative effects on enzyme transcription rates nor on blood parameters indicative of impaired liver metabolic activity or liver injury were identified. These results indicate the P deprivation only indirectly affects the liver through exacerbation of the negative energy balance occurring as P deficient cows become anorectic.

Serum Apelin-36 alteration in late pregnancy and early lactation of dairy cows and its association with negative energy balance markers

The beneficial roles of Apelin on both energy metabolism and insulin sensitivity have been described in previous researches, but it has been little studied in dairy cows. The aim of the present study was to determine the serum Apelin-36 concentration in late pregnancy and early lactation in dairy cows and its association with negative energy balance markers.Thirty Holstein dairy cows (multiparous; n = 15 and primiparous; n = 15) with body condition score 3–3.75 at parturition were selected and blood samples were obtained for metabolic profile one month before and one month after parturition. Apelin-36, glucose, insulin, β-hydroxybutyric acid (BHBA), non-esterified fatty acid (NEFA), cholesterol, triglyceride (TG) and high density lipoproteins (HDL) were measured using commercial kits. BCS and milk production were recorded during the study.There was no effect of parity on Apelin-36, cholesterol, TG, HDL, BHB and NEFA concentrations before lactation; while insulin and glucose levels were higher in primiparous cows than multiparous cows at this period. None of the factors showed any significant difference between multiparous and primiparous cows after lactation. Serum NEFA concentration were increased after parturition, while Apelin-36, insulin and glucose concentrations were decreased after parturition in primiparous and multiparous cows. Significant correlations were observed between serum Apelin and insulin (P = .041, r = 0.672), NEFA (P = .027, r = −0.808) and glucose (P = .037, r = 0.757).In conclusion, our results showed that serum Apelin-36 concentration decreased after parturition in dairy cow. Alteration of Apelin-36 secretion after parturition may represent an endocrine adaptation in dairy cow during the lactating period.

The effect of spring grass availability and grazing rotation length on the production and quality of herbage and milk in early spring

AbstractThe importance of spring grass in the diet of early lactation dairy cows has been widely acknowledged. Numerous studies completed on a plot/paddock basis have identified methods of increasing herbage availability in spring, but little focus was placed on how this impacts animal production. The aim of the current study was to investigate the impact of opening farm cover (OFC; grass availability on farm at turnout in spring; 1036 (high), 748 (medium) and 544 (low) kg DM/ha) and spring rotation length (fast – 56 days and normal – 63 days) on animal performance in early lactation and herbage production and quality. Spring rotation length had little effect on animal performance, herbage variables or sward composition. High OFC increased pre-grazing herbage mass, allowing for increased daily herbage allowance (DHA) compared to medium and low OFC. There was a reduced proportion of leaf in the sward of the high OFC compared to the low OFC, resulting in lower organic matter digestibility. Despite the reduction in sward quality observed as a consequence of achieving high OFC in spring, the greater DHA available to animals increased milk production (+1.4 kg milk/cow/day). Additionally, animals grazing a medium or low OFC had a greater requirement for silage supplementation in spring (+1.3 kg DM/cow/day). The benefits of the higher DHA highlighted in the current study suggest that autumn grazing management must be adapted to increase herbage availability in spring. However, the benefits observed in milk production did not persist beyond the first grazing rotation.

Involvement of Plasma Endocannabinoids and the Hypothalamic Endocannabinoid System in Increasing Feed Intake after Parturition of Dairy Cows

The endocannabinoids (ECs) N-arachidonylethanolamide (anandamide; AEA) and 2-arachidonoylglycerol (2-AG) participate in the control of feed intake and energy metabolism. Most mammals increase their feed intake after parturition to cope with the increased energy and nutrient requirements for milk synthesis, thereby increasing their metabolic rate. Here we investigated in experiment 1 the regulation of plasma AEA and 2-AG concentrations during the transition from late pregnancy to early lactation in dairy cows, and analyzed in experiment 2 the expression of the EC system in the paraventricular nucleus (PVN) and the arcuate nucleus (ARC) of the hypothalamus of late and early lactating cows using immunohistochemistry. Cows in experiment 1 were retrospectively grouped based on peak plasma fatty acid concentrations to a high (H) or low (L) group. Feed intake was not different between groups before parturition, but was lower in H than L cows during early lactation. Plasma AEA and 2-AG concentrations increased 2.2- to 2.4-fold during early lactation, in which time plasma AEA concentrations rose faster in H cows than in L cows postpartum. Upregulation of N-acyl phosphatidylethanolamine-specific phospholipase D together with tending increased cannabinoid receptor 1 (CB1) expression, and downregulation of fatty acid amide hydrolase in early lactating cows suggested an increased PVN AEA tone. The abundance of CB1 in the ARC and diacylglycerol lipase-alpha was not different between late and early lactating cows, but PVN monoacylglycerol lipase expression was 30% higher in early lactating cows, indicating diminished PVN 2-AG concentrations. The results show a potential involvement of AEA in stimulating feed intake and of 2-AG in regulating energy metabolism of early lactating cows.

Proteomic analysis reveals greater abundance of complement and inflammatory proteins in subcutaneous adipose tissue from postpartum cows treated with sodium salicylate

This study aimed to investigate sodium salicylate (SS) treatment effects on the proteome of adipose tissue (AT) in postpartum cows. Twenty Holstein cows were assigned to control (CON, n = 10) or SS (n = 10) provided via drinking water (2.3 g/L) during the first 7 d of lactation. Subcutaneous AT was collected on d 7 of treatment and label-free quantitative shotgun proteomics and immunoblotting were analyzed in a subset of 5 AT per group. Eighty out of 1422 proteins (5.6%) were differentially abundant between CON and SS [fold change ±1.5, P < 0.05]. Top canonical pathways differing between CON and SS (Ingenuity) were complement system, interleukin-10 signaling, and acute phase response signaling. The abundances of complement C1r, C1qC, C1qB and C6 were greater in SS than CON. Regarding IL-10 signaling, the abundances of BLVRB, STAT3, and lipopolysaccharide binding protein (LBP) were greater in SS AT compared to CON. Immunoblots revealed increased abundance of paraoxanase-1 and tumor necrosis factor-alpha, as well as a tendency for greater abundance of cluster differentiation 172a in SS AT, which may indicate of increased macrophage infiltration. SS treatment postpartum likely promotes inflammatory signaling in AT of dairy cows, perhaps due to immune cell recruitment. SignificanceThis work demonstrates that treating early lactating cows with sodium salicylate, an anti-inflammatory agent that has been shown to have metabolic effects and increase milk production in dairy cows, affects the proteome of subcutaneous adipose tissue in early lactating dairy cows. Unexpectedly, sodium salicylate treatment enriched inflammatory pathways of the complement system, cytokine signaling, and acute phase response, as revealed by proteomic analysis of subcutaneous adipose tissues from cows at 7 d postpartum. These findings imply that SS treatment during the first 7 d of lactation likely promotes inflammatory signaling in AT of the dairy cow, perhaps due to immune cell recruitment. Tissue-specific impacts of systemic sodium salicylate requires further scrutiny.

Impact of grass silage quality on greenhouse gas emissions from dairy and beef production

AbstractHigh‐quality grass silages may represent a mitigation option by reducing enteric methane production and by increasing productivity, thus reducing greenhouse gas emissions per kg of product (emission intensity). Two previous studies found considerable effects of three different silage qualities cut at different maturity stages (very early [H1], early [H2] and normal [H3]) offered ad libitum with various levels of concentrate supplementation, on animal performances of growing/finishing bulls and dairy cows in early lactation, indicating that emission intensities may also vary. Based on results from these previous studies, the aim of this study was to estimate emission intensities for milk and beef carcasses for the included combinations of silage qualities and concentrate levels, by using the farm‐scale model HolosNor. The emissions intensities were lowest for the H1 silage, and highest for the H3 silage, independent of concentrate levels for both milk and beef. Thus, increasing concentrate levels did not compensate for lower grass silage quality. Improvements in silage quality from H3 silage to H2 is realistic and has the potential to reduce emission intensities with approximately 10% while keeping the milk yield per cow constant and reducing the use of concentrates considerably. For beef production, the potential is even larger, with a reduction in emission intensity of approximately 17%. We conclude that improving grass silage quality may be a mitigation option that will also reduce the dependence on concentrates.

Estimation Metabolic Status in High Yielding Dairy Cows During Transition Period and Full Lactation

Background: Major changes in the metabolic functions in high-yielding dairy cows occur during the transitional period and during lactation. Parturition and lactogenesis are accompanied by many physiological changes that facilitate the maintenance of homeostasis Consequently, physiological situations leading to a negative energy balance are coupled to an increased uncontrolled rate of body fat mobilisation and the increased fatty acids accumulation in hepatocytes and blood ketone bodies, resulting in disturbances of the morphological and physiological liver integrity. The objective of the present study was to estimate metabolic status in late pregnant, early lactation and full lactation Holstein dairy cows on the basis changes of blood concentrations of selected biochemical markers.Materials, Methods &amp; Results: The experiment included 36 Holstein cows. Three groups of clinically healthy cows were chosen from the herd. Group 1 consisted of late pregnant cows (n = 12) from 30 to 1 day (20 ± 15) to partus; Group 2 comprised early lactation cows (n = 12) in the first month of lactation (15 ± 12 days), and Group 3 included full lactation cows (n = 12) between 60 to 90 days of lactation (81 ± 30 days). Blood samples were collected from all cows, by punction of the jugular vein. Biochemical testing for markers in the blood serum showed significantly lower values (P &lt; 0.05) of glucose, TG, Tchol. and urea in early cows than in full lactation and late-pregnant cows. The blood concentration of NEFA and BHB was significantly increased (P &lt; 0.05) in the group of cows in early lactation compared to the other groups of cows. The mean tBIL. concentration and the serum AST, GGT and ALT activities were markedly increased (P &lt; 0.01) in the lactation cows compared to the late pregnant cows. Furthermore, the intensity of lipomobilisation (NEFA or BHB concentrations) correlated positively (P &lt; 0.05) with the markers of cell damage or liver function impairment (tBIL., serum AST, ALT and GGT activities), but negatively (P &lt; 0.05) with the circulating concentrations of compounds synthesised in liver (glucose, TG and urea).Discussion: In dairy cows, it was observed that up to 50 % of females exhibited some lipid accumulation in liver in the first 3 weeks after calving and that fatty liver occurs primarily in this period. Liver can be categorized into mild, moderate and severe fatty liver as dependent on the degree of pathology and a mild fatty infiltration of liver in dairy cows during lactation is considered to be almost physiological. The blood BHB and NEFA concentrations are markers of lipomobilisation and positively associated with the ketosis and liver steatosis intensity. The simultaneous and parallel variations observed between the extent of the fat infiltration in liver and the serum BHB and NEFA concentrations in puerperal cows clearly indicated that the intense lipomobilisation in the post-partum period has induced lipid overloading and ketogenesis in the liver. On the other hand, it was observed significant decreases in the serum biochemical markers, at least partially synthesised in the liver, such as glucose, TG, Tchol., urea, albumin and TP during the postpartum period. However, the liver steatosis has induced some cellular lesions as evidenced by significant increases in the serum tBIL. concentrations and in the AST, ALT, GGT and LDH enzyme activities in puerperal cows. All these biochemical metabolites may be used as important biochemical markers in the determination of the metabolic status in high-yielding dairy cows during the transition period and during lactation.

Effect of hydroxyselenomethionine on lactation performance, blood profiles, and transfer efficiency in early-lactating dairy cows

The current study investigated the effects of hydroxyselenomethionine (HMBSe), a novel organic selenium (Se) additive, on lactation performance, blood profiles, antioxidative status, and transfer efficiency of Se in early-lactation dairy cows. Sixty multiparous early-lactating dairy cows with similar days in milk (57 d; standard deviation = 9.9) and milk yield (36.5 kg/d; standard deviation = 1.42) were fed a basal diet containing 0.04 mg of Se/kg (dry matter basis). These cows were assigned to 1 of 4 groups following a randomized complete block design as follows: control (basal diet) or HMBSe addition (0.1, 0.3, or 0.5 mg of Se/kg of dry matter). The experiment lasted for 13 wk, with the first week as adaptation. The results showed that milk yields (raw, protein, and lactose) and feed efficiency were improved in a quadratic manner following increased dietary HMBSe addition, whereas energy-corrected milk, 4% fat-corrected milk, and total solid yields tended to be enhanced quadratically. In terms of whole-blood variables, red blood cell and white blood cell levels were increased quadratically, whereas hemoglobin concentration increased linearly with increased HMBSe addition. Plasma nonesterified fatty acid concentrations tended to increase linearly along with HMBSe addition. Plasma superoxide dismutase activity increased quadratically with increased HMBSe addition. The total antioxidant capacity in plasma tended to improve quadratically when cows were fed more HMBSe. Moreover, plasma malondialdehyde concentrations of dairy cows tended to decrease in a quadratic manner when dietary HMBSe increased. The Se concentrations in milk, plasma, and milk/plasma ratio increased linearly following increased HMBSe addition. In conclusion, HMBSe improved lactation performance, health status, and milk Se concentrations in early-lactating dairy cows.

Hepatic mRNA abundance of genes related to nuclear erythroid 2-related factor 2 changes in response to 48 h manipulated plasma metabolites and insulin in dairy cows: Metabolites and insulin infusion effects in cows

The endocrine and metabolic changes in early lactating dairy cows can induce inflammation through reactive oxygen species (ROS) impairing liver function. Nuclear erythroid 2-related factor 2 (Nrf2) is a transcription factor which regulates the expression of genes encoding antioxidative proteins which diminish inflammatory damage, neutralize ROS and suppress pro-inflammatory signaling, thereby protecting the liver. The aim was to investigate hepatic mRNA abundance of genes regulated by Nrf2 in response to a long-term (48 h) insulin or beta-hydroxybutyrate (BHB) infusion in 24 mid-lactating dairy cows. Treatments included 1) hyperinsulinemic clamp infusion (HypoG, n = 5), 2) hyperinsulinemic euglycemic clamp (EuG, n = 6), 3) BHB infusion (HyperB, n = 5), and 4) NaCl infusion (Control, n = 6). Liver tissue was sampled one week before and 48 h after the start of the infusion. Changes of hepatic mRNA abundances of candidate genes assessed via qPCR were evaluated by analysis of variance (ANOVA). Hyperinsulinemia euglycemic clamp downregulated mRNA abundance of microsomal glutathione S-transferase 3 (MGST3), MT1E, MT2A, glutathione peroxidase 3 (GPX3), superoxide dismutase 1(SOD1), catalase (CAT), and NAD (P) H dehydrogenase quinone 1(NQO1) compared to pre-infusions. The mRNA abundance of metallothionein 1A (MT1A) showed a tendency to increase in HyperB in comparison to pre-infusion level. Lower mRNA abundances of MT1E, MGST3, and SOD1 were observed in EuG compared to Control. The mRNA abundance of NQO1 was lower in EuG in comparison to HyperB. Downregulation of candidate genes could be related to reduced hepatic gluconeogenesis, since both high plasma insulin and low glucagon secretion levels were observed in EuG. Downregulation of Nrf2’s antioxidant enzymes may result in reduced liver protection, thereby contributing to impaired hepatic metabolism.

The effect of feedborne Fusarium mycotoxins on dry matter intake, milk production and blood metabolites of early lactation dairy cows

Fusarium mycotoxins (FM) contaminate cereals and corn and may negatively impact dairy cow performance by affecting dry matter intake (DMI) and milk production. Therefore, the objective of this study was to investigate the effect of naturally contaminated feedborne FM on DMI, milk production, BCS and blood metabolites of early lactation dairy cows. Twenty-eight Holstein Friesian cows were allocated to one of two dietary treatments (n = 14) in a randomised complete block design. Diets were offered as a total mixed ration (TMR) [concentrate (corn grain, soya and rapeseed meal), straw, grass silage and corn silage]. Treatment one (Low FM) contained corn grain with low FM levels [deoxynivalenol (DON) 163 μg DON/kg TMR DM and zearalenone (ZON) 19 μg ZON/kg TMR DM] and Treatment two (High FM) contained corn grain with higher FM levels (1966 μg DON/kg TMR DM and 366 μg ZON/kg DM). Cows were blocked on calving date and balanced for parity, predicted milk yield and body condition score. Cows started the trial 28 d post calving with a 10 d dietary acclimatisation period followed by a 28 d experimental period. There was no statistically significant difference in DMI (Low FM = 20.97 kg DM vs High FM = 20.52 kg DM, P = 0.64), milk yield (Low FM = 37.49 kgs vs High FM = 36.75 kgs, P = 0.38) or milk fat and protein kgs (Low FM = 2.61 kg vs High FM = 2.59 kg, P = 0.47) between treatments. However, cows on High FM consumed 0.45 kg DM/d less and produced 0.74 kg/d less milk. In conclusion, at the level of FM contamination reported in this study offered over a 28 d period, there was no significant effect on DMI, milk production or composition of early lactation dairy cows. However, the 0.74 kg/cow/d decline in milk yield due to feeding a FM contaminated ration can represent a significant reduction in farm gate income.

Biogenic amines: Concentrations in serum and skeletal muscle from late pregnancy until early lactation in dairy cows with high versus normal body condition score

Biogenic amines (BA) are a class of nitrogenous compounds that are involved in a wide variety of physiological processes, but their role in transition cows is poorly understood. Our objectives were to describe the longitudinal changes of BA in serum and in skeletal muscle during the transition period and to characterize temporal responses of BA in relation to body condition score (BCS) of periparturient dairy cows. Fifteen weeks before calving, 36 multiparous Holstein cows were assigned to 2 groups (n = 18 per group) that were fed differently to reach either high [HBCS; net energy for lactation (NEL) = 7.2 MJ/kg of dry matter (DM)] or normal BCS (NBCS; NEL = 6.8 MJ/kg of DM) at dry-off. The targeted BCS and back fat thickness (BFT) at dry-off (HBCS, >3.75 and >1.4 cm; NBCS, <3.5 and <1.2 cm) were reached. Thereafter, both groups were fed identical diets. Blood samples and muscle (semitendinosus) biopsies were collected at d -49, +3, +21, and +84 relative to parturition. In serum and skeletal muscle, BA concentrations were measured using a targeted metabolomics assay. The data were analyzed as a repeated measure using the MIXED procedure of SAS. The serum concentrations of most BA (i.e., creatinine, taurine, carnosine putrescine, spermine, α-aminoadipic acid, acetylornithine, kynurenine, serotonin, hydroxyproline, asymmetric dimethylarginine, and symmetric dimethylarginine) fluctuated during the transition period, while others (i.e., spermidine, phenylethylamine) did not change with time. The muscle concentrations of BA remained unchanged over time. Creatinine had the highest concentrations in the serum, while carnosine had the highest concentration among the muscle BA. The serum concentrations of creatinine (d +21), putrescine (d +84), α-aminoadipic acid (d +3), and hydroxyproline (d +21) were or tended to be higher for HBCS compared with NBCS postpartum. The serum concentrations of symmetric dimethylarginine (d -49) and acetylornithine (d +84) were or tended to be lower for HBCS compared with NBCS, respectively. The serum kynurenine/tryptophan ratio was greater with HBCS than with NBCS (d +84). Compared with NBCS, HBCS was associated with lower muscle concentrations of carnosine, but those of hydroxyproline were higher (d -49). In both serum and muscle, the asymmetric dimethylarginine concentrations were greater with HBCS than with NBCS (d -49). No correlation was found between serum and skeletal muscle BA. This study indicates that overconditioning of dairy cows may influence serum and muscle BA concentrations in the periparturient period.

Short communication: Pro- and antioxidative indicators in serum of dairy cows during late pregnancy and early lactation: Testing the effects of parity, different dietary energy levels, and farm

Dairy cows face metabolic challenges in the transition from late pregnancy to early lactation. The energy demands for the growing fetus and the onset of milk production are increasing but voluntary feed intake often decreases around parturition and cannot meet these demands. This energy balance, among others, can change the oxidative status. Oxidative stress occurs when antioxidant defense mechanisms are not sufficient to cope with the increasing generation of reactive oxygen species. Our objectives were to investigate (1) the effect of parity on the oxidative status of dairy cows (n = 247) in late pregnancy and early lactation; and (2) the effect of different inclusion rates of concentrate feeding (150 vs. 250g/kg of energy-corrected milk) during early lactation on 2 farms including 87 cows in total. In addition, we aimed to compare the oxidative status across the 2 farms using equal portions of concentrate feeding. For these purposes, we measured concentrations of the derivatives of reactive oxygen metabolites (dROM) and the ferric reducing ability (FRAP) in serum on d-50, -14, +8, +28, and +100 relative to calving. Furthermore, we calculated the oxidative status index (OSi) as dROM/FRAP × 100. Data were analyzed using a linear mixed model. Cows in the first and second lactations had greater dROM, FRAP, and OSi than cows in their third and greater lactations. Hence, supporting the antioxidative side of the balance might be of particular importance in the first and second lactations. Feeding different amounts of concentrates did not affect dROM, FRAP, or OSi under our experimental conditions, suggesting that the relatively small differences in energy intake were not affecting the oxidative status. Comparing farms, cows from one farm were notable for having greater dROM and lower FRAP, resulting in a greater OSi compared with cows on the other farm. Milk yield showed a time by farm interaction with 7% less milk on d100 on the farm with the greater OSi. Moreover, cows on that farm had 1.4-fold greater β-hydroxybutyrate concentrations. Our results emphasize the value of assessing oxidative status with regard to both the pro- and antioxidative sides, and support the association between oxidative and metabolic status. Further investigations are needed to determine the applicability of OSi as a prognostic tool during early lactation and to determine which factors have the greatest influence on oxidative status.

Effects of stocking density on oxidative stress status and mammary gland permeability in early lactating dairy cows.

The current study was conducted to investigate the effect of stocking density (SD) on oxidative stress status and mammary gland permeability in early lactating dairy cows. Thirty-two dairy cows were allocated into 16 blocks, basing on parity, previous milk yield, and body weight, and were then randomly assigned into one of the two treatments as follows: 75% (75SD) and 100% (100SD) SD. The cows were fed with same diet throughout the 8-week experimental period. The milk yield and milk sample were collected on two consecutive days during the 8-week experimental period weekly. Plasma samples were collected on fourth and eighth experimental weeks. Raw, energy-corrected, and 4% fat-corrected milk yield were significantly higher in 75SD-cows than that of 100SD-animals, respectively. The milk somatic cell count was lower in 75SD-cows than that of 100SD-animals. The levels of Na+ , Na+ /K+ , bovine serum albumin and plasmin were lower in 75SD-cows than those of 100SD-cattle, respectively. The 75SD-cows had reduced insulin and insulin/glucagon levels but higher prolactin and growth hormone concentrations, compared with those of 100SD-animals, respectively. In conclusion, compared with low SD-animals, early lactating cows with higher SD had higher oxidative stress status, which further led to a greater mammary gland permeability.

Impaired hepatic mitochondrial function during early lactation in dairy cows: Association with protein lysine acetylation.

Early lactation is an energy-demanding period for dairy cows which may lead to negative energy balance, threatening animal health and consequently productivity. Herein we studied hepatic mitochondrial function in Holstein-Friesian multiparous dairy cows during lactation, under two different feeding strategies. During the first 180 days postpartum the cows were fed a total mixed ration (70% forage: 30% concentrate) ad libitum (non-grazing group, G0) or grazed Festuca arundinacea or Mendicago sativa plus supplementation (grazing group, G1). From 180 to 250 days postpartum, all cows grazed Festuca arundinacea and were supplemented with total mixed ration. Mitochondrial function was assessed measuring oxygen consumption rate in liver biopsies and revealed that maximum respiratory rate decreased significantly in grazing cows during early lactation, yet was unchanged in non-grazing cows during the lactation curve. While no differences could be found in mitochondrial content or oxidative stress markers, a significant increase in protein lysine acetylation was found in grazing cows during early lactation but not in cows from the non-grazing group. Mitochondrial acetylation positively correlated with liver triglycerides and β-hydroxybutyrate plasma levels, well-known markers of negative energy balance, while a negative correlation was found with the maximum respiratory rate and sirtuin 3 levels. To our knowledge this is the first report of mitochondrial function in liver biopsies of dairy cows during lactation. On the whole our results indicate that mitochondrial function is impaired during early lactation in grazing cows and that acetylation may account for changes in mitochondrial function in this period. Additionally, our results suggest that feeding total mixed ration during early lactation may be an efficient protective strategy.

Relationship between inflammatory biomarkers and oxidative stress with uterine health in dairy cows with different dry period lengths.

Earlier studies indicated that the inflammatory status of dairy cows in early lactation could not be fully explained by the negative energy balance (NEB) at that moment. The objective of the present study was to determine relationships between inflammatory biomarkers and oxidative stress with uterine health in dairy cows after different dry period lengths. Holstein–Friesian dairy cows were assigned to one of three dry period lengths (0-, 30-, or 60-d) and one of two early lactation rations (glucogenic or lipogenic ration). Cows were fed either a glucogenic or lipogenic ration from 10-d before the expected calving date. Part of the cows which were planned for a 0-d dry period dried themselves off and were attributed to a new group (0 → 30-d dry period), which resulted in total in four dry period groups. Blood was collected (N = 110 cows) in weeks −3, −2, −1, 1, 2, and 4 relative to calving to determine biomarkers for inflammation, liver function, and oxidative stress. Uterine health status (UHS) was monitored by scoring vaginal discharge (VD) based on a 4-point scoring system (0, 1, 2, or 3) in weeks 2 and 3 after calving. Cows were classified as having a healthy uterine environment (HU, VD score = 0 or 1 in both weeks 2 and 3), nonrecovering uterine environment (NRU, VD score = 2 or 3 in week 3), or a recovering uterine environment (RU, VD score = 2 or 3 in week 2 and VD score= 0 or 1 in week 3). Independent of dry period length, cows with NRU had higher plasma haptoglobin (P = 0.05) and lower paraoxonase levels (P < 0.01) in the first 4 weeks after calving and lower liver functionality index (P < 0.01) compared with cows with HU. Cows with NRU had lower plasma albumin (P = 0.02) and creatinine (P = 0.02) compared with cows with a RU, but not compared with cows with HU. Independent of UHS, cows with a 0 → 30-d dry period had higher bilirubin levels compared with cows with 0-, 30-, or 60-d dry period (P < 0.01). Cows with RU and fed a lipogenic ration had higher levels of albumin in plasma compared with cows with NRU and fed a lipogenic ration (P < 0.01). In conclusion, uterine health was related to biomarkers for inflammation (haptoglobin and albumin) and paraoxonase in dairy cows in early lactation. Cows which were planned for a 0-d dry period, but dried themselves off (0 → 30-d dry period group) had higher bilirubin levels, which was possibly related to a more severe NEB in these cows. Inflammatory biomarkers in dairy cows in early lactation were related to uterine health in this period.

PHYSIOLOGY SYMPOSIUM: Effects of heat stress during late gestation on the dam and its calf12.

Heat stress during late gestation in cattle negatively affects the performance of the dam and its calf. This brief exposure to an adverse environment before parturition affects the physiological responses, tissue development, metabolism, and immune function of the dam and her offspring, thereby limiting their productivity. During the dry period of a dairy cow, heat stress blunts mammary involution by attenuating mammary apoptosis and autophagic activity and reduces subsequent mammary cell proliferation, leading to impaired milk production in the next lactation. Dairy cows in early lactation that experience prepartum heat stress display reduced adipose tissue mobilization and lower degree of insulin resistance in peripheral tissues. Similar to mammary gland development, placental function is impaired by heat stress as evidenced by reduced secretion of placental hormones (e.g., estrone sulfate) in late gestation cows, which partly explains the reduced fetal growth rate and lighter birth weight of the calves. Compared with dairy calves born to dams that are exposed to evaporative cooling during summer, calves born to noncooled dry cows maintain lower BW until 1 yr of age, but display a stronger ability to absorb glucose during metabolic challenges postnatally. Immunity of the calves, both passive and cell-mediated immune function, is also impaired by prenatal heat stress, resulting in increased susceptibility of the calves to diseases in their postnatal life. In fact, dairy heifers born to heat-stressed dry cows without evaporative cooling have a greater chance leaving the herd before puberty compared with heifers born to dry cows provided with evaporative cooling (12.2% vs. 22.7%). Dairy heifers born to late-gestation heat-stressed dry cows have lower milk yield at maturity during their first and second lactations. Emerging evidence suggests that late-gestation heat stress alters the mammary gland microstructure of the heifers during the first lactation and exerts epigenetic alterations that might explain, in part, their impaired productivity.

Prediction of metabolic clusters in early-lactation dairy cows using models based on milk biomarkers

The aim of this study was to describe metabolism of early-lactation dairy cows by clustering cows based on glucose, insulin-like growth factor I (IGF-I), free fatty acid, and β-hydroxybutyrate (BHB) using the k-means method. Predictive models for metabolic clusters were created and validated using 3 sets of milk biomarkers (milk metabolites and enzymes, glycans on the immunogamma globulin fraction of milk, and Fourier-transform mid-infrared spectra of milk). Metabolic clusters are used to identify dairy cows with a balanced or imbalanced metabolic profile. Around 14 and 35 d in milk, serum or plasma concentrations of BHB, free fatty acids, glucose, and IGF-I were determined. Cows with a favorable metabolic profile were grouped together in what was referred to as the "balanced" group (n = 43) and were compared with cows in what was referred to as the "other balanced" group (n = 64). Cows with an unfavorable metabolic profile were grouped in what was referred to as the "imbalanced" group (n = 19) and compared with cows in what was referred to as the "other imbalanced" group (n = 88). Glucose and IGF-I were higher in balanced compared with other balanced cows. Free fatty acids and BHB were lower in balanced compared with other balanced cows. Glucose and IGF-I were lower in imbalanced compared with other imbalanced cows. Free fatty acids and BHB were higher in imbalanced cows. Metabolic clusters were related to production parameters. There was a trend for a higher daily increase in fat- and protein-corrected milk yield in balanced cows, whereas that of imbalanced cows was higher. Dry matter intake and the daily increase in dry matter intake were higher in balanced cows and lower in imbalanced cows. Energy balance was continuously higher in balanced cows and lower in imbalanced cows. Weekly or twice-weekly milk samples were taken and milk metabolites and enzymes (milk glucose, glucose-6-phosphate, BHB, lactate dehydrogenase, N-acetyl-β-d-glucosaminidase, isocitrate), immunogamma globulin glycans (19 peaks), and Fourier-transform mid-infrared spectra (1,060 wavelengths reduced to 15 principal components) were determined. Milk biomarkers with or without additional cow information (days in milk, parity, milk yield features) were used to create predictive models for the metabolic clusters. Accuracy for prediction of balanced (80%) and imbalanced (88%) cows was highest using milk metabolites and enzymes combined with days in milk and parity. The results and models of the present study are part of the GplusE project and identify novel milk-based phenotypes that may be used as predictors for metabolic and performance traits in early-lactation dairy cows.

Dietary supplementation of Scutellaria baicalensis extract during early lactation decreases milk somatic cells and increases whole lactation milk yield in dairy cattle.

Systemic inflammation is common in early lactation dairy cows and is associated with decreased milk production. The Scutellaria baicalensis plant contains flavonoids with anti-inflammatory and anti-oxidative properties, which may counteract the inflammatory state in early lactation dairy cows. The objective of this experiment was to determine whether Scutellaria baicalensis extract (SBE), a source of bioactive flavonoids, would alter the adaptation to lactation. Multiparous Holstein cows (n = 122) were used in a randomized block design to determine the effect of short-term and long-term postpartum administration of SBE on 305-d milk yield, 120-d milk component yield, and early lactation milk markers of inflammation and metabolic function. Treatments were 1) control, 2) short term (5-d) administration of the SBE (SBE5), and 3) long term (60-d) administration of the SBE (SBE60). Treatments were included in a treatment pellet that was identical to a control pellet in ingredient source and composition except for the extract (10 g/d SBE providing 3.3 g/d of the flavonoid baicalin), both provided via an automated milking system beginning on d 1 of lactation. Milk samples were collected on d 1, 3, and once during d 5–12 of lactation, followed by weekly sampling until 120 days in milk (DIM). Milk samples collected in the first 2 wk were used for biomarker analysis (haptoglobin, β-hydroxybutyrate [BHB], and glucose-6-phosphate [G6P]), and all samples were used for composition analysis. Cows were body condition scored every 2 wk prepartum and postpartum. Milk production, programmed pellet allocation, and actual provision of both pelleted feeds were recorded daily. Treatment effects were evaluated by contrasts between control and SBE5 and control and SBE60 for both the treatment (TP; wk 1–9) and carryover periods (CP; wk 10–37). Total pellet offered was greater for SBE60 in both the TP (P < 0.01) and CP (P = 0.02) but was not different for SBE5 during either period (P ≥ 0.13). No treatment effects were observed for body condition score (BCS), milk haptoglobin, BHB, or G6P. SBE5 did not alter milk yield or milk components. SBE60 increased whole-lactation milk yield by 1,419 kg (13%; P = 0.03). SBE60 increased milk lactose and fat yields (P ≤ 0.04) and tended to increase milk protein yield (P = 0.09) during TP, and each increased during CP (P ≤ 0.04). Somatic cell count decreased by 10% in SBE60 during TP (P = 0.02) but not CP (P = 0.13). Mastitis incidence tended to differ by treatment, being lesser for both SBE5 and SBE60 vs. control (14 and 15% vs. 33%). SBE supplementation did not impact time to pregnancy or hazard of leaving the herd. In conclusion, despite no detected treatment effects on BCS or milk biomarkers of inflammation and metabolic status, supplementation of postpartum dairy cows with Scutellaria baicalensis extract for 60 d was effective at increasing whole lactation milk yield.