@article{GhaffariBernhoeftEtheveetal.2019,
  author    = {Ghaffari, Morteza Hosseini and Bernhoeft, Katrin and Etheve, Stephane and Immig, Irmgard and Hoelker, Michael and Sauerwein, Helga and Schweigert, Florian J.},
  title     = {Technical note: Rapid field test for the quantification of vitamin E, beta-carotene, and vitamin A in whole blood and plasma of dairy cattle},
  series = {Journal of dairy science},
  volume    = {102},
  journal   = {Journal of dairy science},
  number    = {12},
  publisher = {Elsevier},
  address   = {New York},
  issn      = {0022-0302},
  doi       = {10.3168/jds.2019-16755},
  pages     = {11744 -- 11750},
  year      = {2019},
  abstract  = {Fast and easy tests for quantifying fat-soluble vitamins such as vitamin E and vitamin A, as well as beta-carotene, in whole blood without a need to preprocess blood samples could facilitate assessment of the vitamin status of dairy cattle. The objective of this study was to validate a field-portable fluorometer/spectrophotometer assay for the rapid quantification of these vitamins in whole blood and plasma of dairy cows and calves. We measured the concentrations of vitamin E and beta-carotene in whole blood and plasma from 28 dairy cows and 11 calves using the iCheck test (Bio-Analyt GmbH, Teltow, Germany) and compared the results with the current analytical standard (HPLC) in 2 independent laboratories, one at the University of Potsdam (Germany) and at one at DSM Nutritional Products Ltd. (Kaiseraugst, Switzerland). For vitamin A, the HPLC measurements were done only in the laboratory in Germany. The whole-blood concentrations of vitamin E as determined by iCheck (blood-hematocritcorrected) ranged from 1.82 to 4.99 mg/L in dairy cows and 0.34 to 3.40 mg/L in calves. These findings were moderately correlated (R-2 = 0.66) with the values assessed by HPLC in dairy cattle (cows + calves). When calves were excluded, the correlation was higher (R-2 = 0.961). The beta-carotene and vitamin A values obtained by the reference method HPLC were highly correlated with the iCheck methods in whole blood (R-2 = 0.99 and 0.88, respectively). In plasma, we observed strong correlations between the concentrations assessed by iCheck and those of HPLC for vitamin E (R-2 = 0.97), beta-carotene (R-2 = 0.98), and vitamin A (R-2 = 0.92) in dairy cattle (cows + calves). For vitamin E, beta-carotene, and vitamin A, we compared the relationship between the differences obtained by the iCheck assay and the HPLC measurements, as well as the magnitude of measurements, using Bland-Altman plots to test for systematic bias. For all 3 vitamins, the differences values were not outside the 95\% acceptability limits; we found no systematic error between the 2 methods for all 3 analytes.},
  language  = {en}
}
@article{IslamKhalilMaenneretal.2017,
  author    = {Islam, Khan M. S. and Khalil, Mahmoud Abd Elhamid and Maenner, Klaus and Raila, Jens and Rawel, Harshadrai Manilal and Zentek, J{\"u}rgen and Schweigert, Florian J.},
  title     = {Lutein Specific Relationships among Some Spectrophotometric and Colorimetric Parameters of Chicken Egg Yolk},
  series = {The journal of poultry science},
  volume    = {54},
  journal   = {The journal of poultry science},
  publisher = {Japan Poultry Science Association},
  address   = {Tsukuba},
  issn      = {1346-7395},
  doi       = {10.2141/jpsa.0160065},
  pages     = {271 -- 277},
  year      = {2017},
  abstract  = {Lutein is an essential dietary carotenoid with health benefits and is inter alia responsible for the colouration of egg yolk. The relationship between lutein accumulation and egg yolk colouration was therefore studied in more detail. After feeding a low-luteine diet for 21 days, 14 birds (Lohmann brown hens aged 20 weeks) were fed a diet containing marigold (80 mg lutein/kg feed) and 14 other birds were fed a diet containing oleoresin (45 mg lutein/kg feed) for 21 days; for both groups of birds, this feeding period was followed by withdrawal for 21 days. The Roche Yolk Colour Fan (RYCF) score (0 to 15, where higher values denote greater colour intensity; R-2=0.87; P<0.01) and redness (R-2=0.89; P<0.01) increased with increasing lutein content of egg yolk. Total carotenoid content had a poor relationship with lightness (R-2=0.13; P>0.05) and yellowness (R-2=0.12; P>0.05) of the yolk. It may be concluded that increased lutein is potentially responsible for an increased RYCF score and redness (a*), but decreased yellowness (b*) and lightness (L*), of egg yolk.},
  language  = {en}
}
@article{IslamKhalilMaenneretal.2016,
  author    = {Islam, Khan Shaiful and Khalil, Mahmoud and M{\"a}nner, K. and Raila, Jens and Rawel, Harshadrai Manilal and Zentek, J. and Schweigert, Florian J.},
  title     = {Effect of dietary alpha-tocopherol on the bioavailability of lutein in laying hen},
  series = {Journal of animal physiology and animal nutrition},
  volume    = {100},
  journal   = {Journal of animal physiology and animal nutrition},
  publisher = {Wiley-Blackwell},
  address   = {Hoboken},
  issn      = {0931-2439},
  doi       = {10.1111/jpn.12464},
  pages     = {868 -- 875},
  year      = {2016},
  abstract  = {Lutein and its isomer zeaxanthin have gained considerable interest as possible nutritional ingredient in the prevention of age-related macular degeneration (AMD) in humans. Egg yolk is a rich source of these carotenoids. As an oxidative sensitive component, antioxidants such as -tocopherol (T) might contribute to an improved accumulation in egg yolk. To test this, chickens were fed lutein esters (LE) with and without -tocopherol as an antioxidant. After depletion on a wheat-soya bean-based lutein-poor diet for 21days, laying hens (n=42) were equally divided into three groups and fed the following diets for 21days: control (basal diet), a LE group (40mg LE/kg feed) and LE+T group (40mg LE plus 100mg T/kg feed). Eggs and blood were collected periodically. Carotenoids and -tocopherol in yolk and blood plasma were determined by HPLC. Egg yolk was also analysed for total carotenoids using a one-step spectrophotometric method (iCheck(())). Lutein, zeaxanthin, -tocopherol and total carotenoids in egg yolk were highest after 14days of feeding and decreased slightly afterwards. At the end of the trial, eggs of LE+T group contained higher amount of lutein (13.72), zeaxanthin (0.65), -tocopherol (297.40) and total carotenoids (21.6) compared to the LE group (10.96, 0.55, 205.20 and 18.0mg/kg, respectively, p<0.05). Blood plasma values of LE+T group contain higher lutein (1.3), zeaxanthin (0.06) and tocopherol (20.1) compared to LE group (1.02, 0.04 and 14.90mg/l, respectively, p<0.05). In conclusion, dietary -tocopherol enhances bioavailability of lutein reflecting higher content in egg yolk and blood plasma. Improved bioavailability might be due to increased absorption of lutein in the presence of tocopherol and/or a greater stability of lutein/zeaxanthin due to the presence of -tocopherol as an antioxidant.},
  language  = {en}
}
@article{IslamSchweigert2015,
  author    = {Islam, Khan Md. Shaiful and Schweigert, Florian J.},
  title     = {Comparison of three spectrophotometric methods for analysis of egg yolk carotenoids},
  series = {Food chemistry},
  volume    = {172},
  journal   = {Food chemistry},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0308-8146},
  doi       = {10.1016/j.foodchem.2014.09.045},
  pages     = {233 -- 237},
  year      = {2015},
  abstract  = {Carotenoids accumulated in the egg yolk are of importance for two reasons. Firstly they are important pigments influencing customer acceptance and secondly they are essential components with positive health effects either as antioxidants or as precursor of vitamin A. Different analytical methods are available to quantitatively identify carotenoids from egg yolk such as spectrophotometric methods described by AOAC (Association of Official Analytical Chemists) and HPLC (High Performance Liquid Chromatography). Both methods have in common that they are time consuming, need a laboratory environment and well trained technical operators. Recently, a rapid lab-independent spectrophotometric method (iCheck, BioAnalyt GmbH, Germany) has been introduced that claims to be less time consuming and easy to operate. The aim of the current study was therefore to compare the novel method with the two standard methods. Yolks of 80 eggs were analysed as aliquots by the three methods in parallel. While both spectrometric methods are only able measure total carotenoids as total beta-carotene, HPLC enables the determination of individual carotenoids such lutein, zeaxanthin, canthaxanthin, beta-carotene and beta-apocarotenoic ester. In general, total carotenoids levels as obtained by AOAC were in average 27\% higher than those obtained by HPLC. Carotenoid values obtained by the reference methods AOAC and HPLC are highly correlated with the iCheck method with r(2) of 0.99 and 0.94 for iCheck vs. AOAC and iCheck vs. HPLC, respectively (both p < 0.001). Bland Altman analysis showed that the novel iCheck method is comparable to the reference methods. In conclusion, the novel rapid and portable iCheck method is a valid and effective tool to determine total carotenoid of egg yolk under laboratory-independent conditions with little trained personal. (C) 2014 Elsevier Ltd. All rights reserved.},
  language  = {en}
}
@article{RailaEnjalbertMothesetal.2012,
  author    = {Raila, Jens and Enjalbert, Francis and Mothes, Ralf and Hurtienne, Andrea and Schweigert, Florian J.},
  title     = {Validation of a new point-of-care assay for determination of ss-carotene concentration in bovine whole blood and plasma},
  series = {Veterinary clinical pathology},
  volume    = {41},
  journal   = {Veterinary clinical pathology},
  number    = {1},
  publisher = {Wiley-Blackwell},
  address   = {Malden},
  issn      = {0275-6382},
  doi       = {10.1111/j.1939-165X.2012.00400.x},
  pages     = {119 -- 122},
  year      = {2012},
  abstract  = {Background: beta-Carotene is an important precursor of vitamin A, and is associated with bovine fertility. beta-Carotene concentrations in plasma are used to optimize beta-carotene supplementation in cattle, but measurement requires specialized equipment to separate plasma and extract and measure beta-carotene, either using spectrophotometry or high performance liquid chromatography (HPLC). Objective: The objective of this study was to validate a new 2-step point-of-care (POC) assay for measuring beta-carotene in whole blood and plasma. Methods: beta-carotene concentrations in plasma from 166 cows were measured using HPLC and compared with results obtained using a POC assay, the iCheck-iEx-Carotene test kit. Whole blood samples from 23 of these cattle were also evaluated using the POC assay and compared with HPLC-plasma results from the same 23 animals. The POC assay includes an extraction vial (iEx Carotene) and hand-held photometer (iCheck Carotene). Results: Concentrations of beta-carotene in plasma measured using the POC assay ranged from 0.40 to 15.84 mg/L (n = 166). No differences were observed between methods for assay of plasma (mean +/- SD; n = 166): HPLC-plasma 4.23 +/- 2.35 mg/L; POC-plasma 4.49 +/- 2.36 mg/L. Similar good agreement was found when plasma analyzed using HPLC was compared with whole blood analyzed using the POC system (n = 23): HPLC-plasma 3.46 +/- 2.12 mg/L; POC-whole blood 3.67 +/- 2.29 mg/L. Conclusions: Concentrations of beta-carotene can be measured in blood and plasma from cattle easily and rapidly using a POC assay, and results are comparable to those obtained by the highly sophisticated HPLC method. Immediate feedback regarding beta-carotene deficiency facilitates rapid and appropriate optimization of beta-carotene supplementation in feed.},
  language  = {en}
}