Milk production in dairy cows has dramatically increased over the past few decades. The selection for higher milk yield affects the partitioning of available nutrients, with more energy being allocated to milk synthesis and less to physiological processes essential to fertility and fitness. In this study, the abundance of numerous milk metabolites in early and late lactation was systematically investigated, with an emphasis on metabolites related to energy metabolism. The aim of the study was the identification and correlation of milk constituents to the metabolic status of the cows. To investigate the influence of lactation stage on physiological and metabolic variables, 2 breeds of different productivity were selected for investigation by high-resolution nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry. We could reliably quantify 44 different milk metabolites. The results show that biomarkers such as acetone and beta-hydroxybutyrate are clearly correlated to the metabolic status of the individual cows during early lactation. Based on these data, the selection of cows that cope well with the metabolic stress of early lactation should become an option.

The objective was to compare the effects of 3 management systems in high-yielding dairy cows on metabolic profiles and milk production. Thirty-six multiparous Brown Swiss cows were randomly assigned to 1 of 3 treatment groups (n=12 cows/group): the control (C) group, in which cows were dried off 56 d before calving and milked twice daily throughout next lactation (305 d); the once daily milking (ODM) group, in which cows were dried off 56 d before calving and milked once daily for the first 4 wk of lactation and twice daily for the remaining lactation; and the continuous milking (CM) group, in which cows were milked twice daily until calving and also during the subsequent lactation. Serum glucose concentrations decreased between wk 1 and 4 exclusively in C cows. Serum concentrations of NEFA and BHBA in the first 4 wk of lactation were highest in C cows compared with ODM and CM cows. Decreased backfat thickness during early lactation and reduction of body condition score were markedly more pronounced in C cows compared with ODM and CM cows. Mean lactational milk yield of C cows [11,310+/-601 kg of energy-corrected milk (ECM)/305 d] was approximately 16% higher compared with ODM cows (9,531+/-477 kg of ECM/305 d) and CM cows (9,447+/-310 kg of ECM/305 d). The lactation curve of CM cows compared with C cows was characterized by a similar time of peak yield (wk 3), a reduced peak yield, and no obvious differences in persistency. Mean percentage of milk protein was significantly higher for CM cows (3.91%) compared with C cows (3.52%). In contrast, once daily milking was accompanied by a reduced and significantly delayed peak yield (wk 8) compared with the control treatment, whereas persistency was better and milk protein (3.79%) was higher in ODM cows than in C cows. In conclusion, continuous milking and once daily milking, targeting the interval before or after calving, respectively, substantially reduced the metabolic challenge of fresh cows and improved milk protein percentage. Continuous milking and once daily milking increased milk protein percentage markedly; furthermore, once daily milking during the first 4 wk of lactation improved the lactation curve.

The effect of somatic cell count (SCC) and milk fraction on milk composition, distribution of cell populations, and mRNA expression of various inflammatory parameters was studied. Therefore, quarter milk samples were defined as cisternal (C), first 400 g of alveolar (A1), and remaining alveolar milk (A2) during the course of milking. Quarters were assigned to 4 groups according to their total SCC: 1) <12 x 10(3)/mL, 2) 12 to 100 x 10(3)/mL, 3) 100 to 350 x 10(3)/mL, and 4) >350 x 10(3)/mL. Milk constituents of interest were SCC, fat, protein, lactose sodium, and chloride ions as well as electrical conductivity. Cell populations were classified into lymphocytes, macrophages, and neutrophils (PMN). The mRNA expression of the inflammatory factors tumor necrosis factor-alpha, interleukin-1beta, cyclooxygenase-2, lactoferrin, and lysozyme was measured via real-time, quantitative reverse transcription PCR. Somatic cell count decreased from highest levels in C to lowest levels in A1 and increased thereafter to A2 in all groups. Fat content increased from C to A2 and with increasing SCC level. Lactose decreased with increasing SCC level but remained unchanged during milking. Concentrations of sodium and chloride, and electrical conductivity increased with increasing SCC but were higher in C than in A1 and A2. Protein was not affected by milk fraction or SCC level. The distribution of leukocytes was dramatically influenced by milk fraction and SCC. Lymphocytes were the dominating cell population in group 1, but the proportion of lymphocytes was low in groups 2, 3, and 4. Macrophage proportion was highest in group 2 and decreased in groups 3 and 4, whereas that of PMN increased from group 2 to 4. The content of macrophages decreased during milking in all SCC groups whereas that of PMN increased. The proportion of lymphocytes was not affected by milk fraction. The mRNA expression of all inflammatory factors showed an increase with increasing SCC but minor changes occurred during milking. In conclusion, milk fraction and SCC level have a crucial influence on the distribution of leukocyte populations and several milk constituents. The surprisingly high content of lymphocytes and concomitantly low mRNA expression of inflammatory factors in quarters with SCC <12 x 10(3)/mL indicates a different and possibly reduced readiness of the immune system to respond to invading pathogens.

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Bovine serum, EDTA-plasma and EDTA-plasma fortified with acetylsalicylic acid (ASA) as antioxidant were compared with regard to their suitability for metabolomic studies. Metabolic fingerprints were generated from GC-TOF-MS data using the Leco ChromaTOF software in combination with the in-house retention time correction and data alignment tool INCA. A total of 6, 9 and 21 significant features with a false discovery rate of <0.05 were identified by INCA upon comparing EDTA- versus EDTA-ASA-plasma, EDTA-plasma versus serum and EDTA-ASA-plasma versus serum, respectively. To confirm that the observed signal intensities in the GC-TOF-MS fingerprints reflected true metabolite abundances, 19 amino acids, glucose and 6 organic acids were quantified by means of GC-MS using stable-isotope-labeled internal standards. As observed with the fingerprints, only the concentrations of lactate and citrate were found to be significantly lower in EDTA-plasma and serum, respectively, whereas the concentrations of the other metabolites were similar among the three sample types investigated.

Impaired function of polymorphonuclear neutrophilic leukocyte (PMNL) during the peripartal period is a major reason for increased susceptibility of dairy cows to infections in this critical interval. Factors dysregulating PMNL function are widely unknown. Insulin-like growth factor (IGF-I) enhanced PMNL functions in vitro. The objective of this study was to investigate the influence of IGF-I and, additionally, β-hydroxybutyrate and nonesterified fatty acid concentrations on phagocytic activity (PA, percentage of viable PMNL) and phagocytic capacity (PC, mean fluorescence intensity of phagocytic PMNL) assessed by flow cytometry. Antepartum (i.e., wk -3, -2, -1; before calving), plasma concentrations of IGF-I were high (80-110 ng/mL) without significant differences between primiparous and pluriparous cows (n=18 and n=41, respectively). Concentrations of IGF-I declined toward the week of calving (wk 1). Postpartum (i.e., wk 2, 3, and 4; after calving), IGF-I remained lower than before parturition, with concentrations higher in primiparous compared with those of pluriparous cows. The PA was constant in primiparous cows throughout the study period. Conversely, PMNL of pluriparous cows had a significantly increased and higher PA in wk 2 and 3 postpartum compared with that of primiparous cows. The PC decreased significantly only in primiparous cows the week of calving, whereas the number of PMNL in primiparous cows exceeded that of pluriparous cows significantly. The phagocytic power (PP, a product of PA by PC), but not the phagocytic overall performance (POP, a product of PA, PC, and PMNL number), differed between primiparous and pluriparous cows in wk 3 postpartum. No significant differences in POP were found, except in wk 4 after calving between the primi- and pluriparous cows. In both groups, POP increased in the week of calving (wk 1). In contrast to β-hydroxybutyrate, which was weakly positive correlated with PA and PP in pluriparous cows in the transition period (wk -3 antepartum to wk 4 postpartum), pluriparous animals had weak negative correlations of PMNL number, PA, PP, POP, and IGF-I concentration in this period. In primiparous animals, only PP and PC were weakly negatively correlated with IGF-I in the transition period. Increased plasma IGF-I concentrations were not associated with enhanced phagocytosis function of bovine blood PMNL ex vivo and, thus, can not be regarded as a suitable predictor for this function.

BackgroundConjugated linoleic acid (CLA) is a collective term for isomers of octadecadienoic acid with conjugated double-bond system. Thus, it was the objective to investigate whether milk composition and metabolic key parameters are affected by adding CLA to the diet of dairy cows in the first four weeks of lactation.MethodsA study was carried out with five primiparous cows fed a CLA supplemented diet compared to five primiparous cows without CLA supplementation. CLA supplemented cows received 7.5 g CLA/day (i.e. 50% cis(c)9,trans(t)11- and 50% t10,c12-CLA) starting two weeks before expected calving and 20 g CLA/day (i.e. 50% c9,t11- and 50% t10,c12-CLA) throughout day 1 to 28 of lactation.ResultsThe CLA supplement was insufficiently accepted by the animals: only 61.5% of the intended amount was ingested. Fed CLA were detectable in milk fat, whereas contents of c9,t11-CLA and t10,c12-CLA in milk fat were higher for CLA supplemented cows compared to the control group. On average over the entire treatment period, there was a decrease of saturated fatty acids (FA) in milk fat of CLA supplemented cows, combined with a higher content of monounsaturated and trans FA.Our study revealed no significant effects of c9,t11- and t10,c12-CLA supplementation either on milk yield and composition or on metabolic key parameters in blood. Furthermore the experiment did not indicate significant effects of c9,t11- and t10,c12-CLA-supplementation on gene expression of peroxisome proliferator-activated receptor-alpha (PPARα), PPARγ, sterol regulatory element-binding protein-1 and tumor necrosis factor-alpha in liver tissue.ConclusionsFeeding c9,t11- and t10,c12-CLA during the first weeks after calving did not affect metabolic key parameters of blood serum or milk composition of fresh cows. Milk fatty acid composition was changed by feeding c9,t11- and t10,c12-CLA resulting in higher contents of these isomers in milk fat. High contents of long chain FA in milk fat indicate that CLA supplementation during the first four weeks of lactation did not affect massive peripheral lipomobilization.

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