@misc{MorrisSaltRailaetal.2012,
  author    = {Morris, Penelope J. and Salt, Carina and Raila, Jens and Brenten, Thomas and Kohn, Barbara and Schweigert, Florian J. and Zentek, J{\"u}rgen},
  title     = {Safety evaluation of vitamin A in growing dogs},
  series = {Potsprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Potsprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {686},
  doi       = {10.25932/publishup-41492},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-414929},
  pages     = {10},
  year      = {2012},
  abstract  = {The safe upper limit for inclusion of vitamin A in complete diets for growing dogs is uncertain, with the result that current recommendations range from 5.24 to 104.80 mu mol retinol (5000 to 100 000 IU vitamin A)/4184 kJ (1000 kcal) metabolisable energy (ME). The aim of the present study was to determine the effect of feeding four concentrations of vitamin A to puppies from weaning until 1 year of age. A total of forty-nine puppies, of two breeds, Labrador Retriever and Miniature Schnauzer, were randomly assigned to one of four treatment groups. Following weaning at 8 weeks of age, puppies were fed a complete food supplemented with retinyl acetate diluted in vegetable oil and fed at 1ml oil/100 g diet to achieve an intake of 5.24, 13.10, 78.60 and 104.80 mu mol retinol (5000, 12 500, 75 000 and 100 000 IU vitamin A)/4184 kJ (1000 kcal) ME. Fasted blood and urine samples were collected at 8, 10, 12, 14, 16, 20, 26, 36 and 52 weeks of age and analysed for markers of vitamin A metabolism and markers of safety including haematological and biochemical variables, bone-specific alkaline phosphatase, cross-linked carboxyterminal telopeptides of type I collagen and dual-energy X-ray absorptiometry. Clinical examinations were conducted every 4 weeks. Data were analysed by means of a mixed model analysis with Bonferroni corrections for multiple endpoints. There was no effect of vitamin A concentration on any of the parameters, with the exception of total serum retinyl esters, and no effect of dose on the number, type and duration of adverse events. We therefore propose that 104.80 mu mol retinol (100 000 IU vitamin A)/4184 kJ (1000 kcal) is a suitable safe upper limit for use in the formulation of diets designed for puppy growth.},
  language  = {en}
}
@article{RuhlFritzscheVermotetal.2006,
  author    = {Ruhl, R. and Fritzsche, Britta and Vermot, J. and Niederreither, K. and Neumann, U. and Schmidt, A. and Schweigert, Florian J. and Dolle, P.},
  title     = {Regulation of expression of the retinoic acid-synthesising enzymes retinaldehyde dehydrogenases in the uteri of ovariectomised mice after treatment with oestrogen, gestagen and their combination},
  year      = {2006},
  abstract  = {The active metabolite of vitaminA, retinoic acid (RA), plays an important role in the female reproductive system. The synthesis of RA is tightly regulated by the activity of retinaldehyde dehydrogenases (Raldh). Among these, Raldh1 and Raldh2 exhibit specific temporal and spatial expression patterns in the mouse uterus, both during the oestrous cycle and early pregnancy. In the present study, we have assessed whether oestradiol and progesterone directly influence the uterine expression of Raldh1 and Raldh2 in ovariectomised mice. We investigated the effect of gestagen (promegestone 0.3 mg kg(-1) bodyweight), oestrogen (oestradiol 3 mu g kg(-1) bodyweight) and their combination on the uterine expression of Raldh2. Expression was analysed using in situ hybridisation and quantified using real-time detection reverse transcription-polymerase chain reaction. The results show that the expression of Raldh2 is rapidly (within 1-4 h) induced in stromal cells by oestrogen, but not by gestagen, treatment, whereas combined oestrogen + gestagen treatment leads to a more prolonged (48 h) response. In contrast, oestrogen, but not progesterone, treatment downregulates (within 4 - 24 h) Raldh1 expression in the uterine glandular epithelium. We conclude that the uterine RA concentrations are regulated by oestrogens via an effect on the expression of the Raldh synthesising enzymes. Such a regulation is consistent with the natural fluctuations of Raldh expression during the oestrous cycle, early pregnancy and blastocyst implantation},
  language  = {en}
}
@article{SchweigertKriegerSchnurrbuschetal.2003,
  author    = {Schweigert, Florian J. and Krieger, K. and Schnurrbusch, D. and Schams, D. and Gropp, J.},
  title     = {Effect of dietary ß-carotene on the early embryonic development and uterine fluid composition of gilts},
  year      = {2003},
  language  = {en}
}
@misc{SchweigertReimann2011,
  author    = {Schweigert, Florian J. and Reimann, J.},
  title     = {Micronutrients and their Relevance for the Eye - Function of Lutein, Zeaxanthin and Omega-3 Fatty Acids},
  series = {Klinische Monatsbl{\"a}tter f{\"u}r Augenheilkunde},
  volume    = {228},
  journal   = {Klinische Monatsbl{\"a}tter f{\"u}r Augenheilkunde},
  number    = {6},
  publisher = {Thieme},
  address   = {Stuttgart},
  issn      = {0023-2165},
  doi       = {10.1055/s-0029-1245527},
  pages     = {537 -- 543},
  year      = {2011},
  abstract  = {Micronutrients play an important role in function and health maintenance for the eye. Especially lutein, zeaxanthin and omega-3 fatty acids perform remarkable functions: lutein together with zeaxanthin forms the macular pigment, these carotenoids filter out the damaging blue light component from the sunlight as well as the ultraviolet light which leads to improved contrast sensitivity and less problems with screen glare. Furthermore, the macular pigment has antioxidant and anti-inflammatory effects. The omega-3 fatty acids also possess anti-inflammatory effects and, when converted into neuroprotectin, they protect against oxidative induced apoptosis in the retina. They are also responsible for the fluidity and supply to the photoreceptor membrane. These properties are important for the prevention and treatment of degenerative eye diseases like age-related macular degeneration. However, older people are often not sufficiently supplied of micronutrients in their diet. Because the supply of nutrients can hardly be achieved by dietary change, the additional intake in the form of food supplements is useful in this age group. Scientific studies have shown the positive effects of supplementation with micronutrients such as lutein/zeaxanthin, vitamin C, vitamin E, zinc and omega-3 fatty acids, docosahexaenoic acid and eicosapentaenoic acid (DHA and EPA). Currently available nutritional products are based in part on the ingredients of the ARED study (Age Related Eye Disease Study). According to more recent studies formulations containing lutein and omega-3 fatty acids in physiologically meaningful doses without additional beta-carotene should be preferred. 10 to 20 mg of lutein and zeaxanthin represent a safe daily dose Regarding to the context above, beta-carotene in high doses plays a minor role to the eye and is especially critical for the health of smokers. This paper summarises the functions of the presented micronutrients in the eye and can assist ophthalmologists in advising their patients.},
  language  = {de}
}
@article{BrentenMorrisSaltetal.2014,
  author    = {Brenten, Thomas and Morris, Penelope J. and Salt, Carina and Raila, Jens and Kohn, Barbara and Brunnberg, Leo and Schweigert, Florian J. and Zentek, Juergen},
  title     = {Energy intake, growth rate and body composition of young Labrador Retrievers and Miniature Schnauzers fed different dietary levels of vitamin A},
  series = {The British journal of nutrition : an international journal devoted to the science of human and animal nutrition},
  volume    = {111},
  journal   = {The British journal of nutrition : an international journal devoted to the science of human and animal nutrition},
  number    = {12},
  publisher = {Cambridge Univ. Press},
  address   = {Cambridge},
  issn      = {0007-1145},
  doi       = {10.1017/S0007114514000543},
  pages     = {2104 -- 2111},
  year      = {2014},
  abstract  = {Research in rodents has shown that dietary vitamin A reduces body fat by enhancing fat mobilisation and energy utilisation; however, their effects in growing dogs remain unclear. In the present study, we evaluated the development of body weight and body composition and compared observed energy intake with predicted energy intake in forty-nine puppies from two breeds (twenty-four Labrador Retriever (LAB) and twenty-five Miniature Schnauzer (MS)). A total of four different diets with increasing vitamin A content between 5.24 and 104.80 mu mol retinol (5000-100 000 IU vitamin A)/4184 kJ (1000 kcal) metabolisable energy were fed from the age of 8 weeks up to 52 (MS) and 78 weeks (LAB). The daily energy intake was recorded throughout the experimental period. The body condition score was evaluated weekly using a seven-category system, and food allowances were adjusted to maintain optimal body condition. Body composition was assessed at the age of 26 and 52 weeks for both breeds and at the age of 78 weeks for the LAB breed only using dual-energy X-ray absorptiometry. The growth curves of the dogs followed a breed-specific pattern. However, data on energy intake showed considerable variability between the two breeds as well as when compared with predicted energy intake. In conclusion, the data show that energy intakes of puppies particularly during early growth are highly variable; however, the growth pattern and body composition of the LAB and MS breeds are not affected by the intake of vitamin A at levels up to 104.80 mu mol retinol (100 000 IU vitamin A)/4184 kJ (1000 kcal).},
  language  = {en}
}
@article{MorrisSaltRailaetal.2012,
  author    = {Morris, Penelope J. and Salt, Carina and Raila, Jens and Brenten, Thomas and Kohn, Barbara and Schweigert, Florian J. and Zentek, Juergen},
  title     = {Safety evaluation of vitamin A in growing dogs},
  series = {BRITISH JOURNAL OF NUTRITION},
  volume    = {108},
  journal   = {BRITISH JOURNAL OF NUTRITION},
  number    = {10},
  publisher = {CAMBRIDGE UNIV PRESS},
  address   = {CAMBRIDGE},
  issn      = {0007-1145},
  doi       = {10.1017/S0007114512000128},
  pages     = {1800 -- 1809},
  year      = {2012},
  abstract  = {The safe upper limit for inclusion of vitamin A in complete diets for growing dogs is uncertain, with the result that current recommendations range from 5.24 to 104.80 mu mol retinol (5000 to 100 000 IU vitamin A)/4184 kJ (1000 kcal) metabolisable energy (ME). The aim of the present study was to determine the effect of feeding four concentrations of vitamin A to puppies from weaning until 1 year of age. A total of forty-nine puppies, of two breeds, Labrador Retriever and Miniature Schnauzer, were randomly assigned to one of four treatment groups. Following weaning at 8 weeks of age, puppies were fed a complete food supplemented with retinyl acetate diluted in vegetable oil and fed at 1ml oil/100 g diet to achieve an intake of 5.24, 13.10, 78.60 and 104.80 mu mol retinol (5000, 12 500, 75 000 and 100 000 IU vitamin A)/4184 kJ (1000 kcal) ME. Fasted blood and urine samples were collected at 8, 10, 12, 14, 16, 20, 26, 36 and 52 weeks of age and analysed for markers of vitamin A metabolism and markers of safety including haematological and biochemical variables, bone-specific alkaline phosphatase, cross-linked carboxyterminal telopeptides of type I collagen and dual-energy X-ray absorptiometry. Clinical examinations were conducted every 4 weeks. Data were analysed by means of a mixed model analysis with Bonferroni corrections for multiple endpoints. There was no effect of vitamin A concentration on any of the parameters, with the exception of total serum retinyl esters, and no effect of dose on the number, type and duration of adverse events. We therefore propose that 104.80 mu mol retinol (100 000 IU vitamin A)/4184 kJ (1000 kcal) is a suitable safe upper limit for use in the formulation of diets designed for puppy growth.},
  language  = {en}
}
@article{BechirSchellingKraemeretal.2012,
  author    = {Bechir, Mahamat and Schelling, E. and Kr{\"a}mer, K. and Schweigert, Florian J. and Bonfoh, Bassirou and Crump, L. and Tanner, M. and Zinsstag, J.},
  title     = {Retinol assessment among women and children in sahelian mobile pastoralists},
  series = {EcoHealth : conservation medicine, human health, ecosystem sustainability},
  volume    = {9},
  journal   = {EcoHealth : conservation medicine, human health, ecosystem sustainability},
  number    = {2},
  publisher = {Springer},
  address   = {New York},
  issn      = {1612-9202},
  doi       = {10.1007/s10393-012-0781-7},
  pages     = {113 -- 121},
  year      = {2012},
  abstract  = {Micronutrient deficiencies are widespread in developing countries, particularly in remote communities such as mobile pastoralists. The nutritional and vitamin A status of this population is not well-documented in Chad. This study assessed serum retinol levels among women and children under five-year-old in nomadic and semi-nomadic pastoralist and rural-settled communities, who are similarly exposed to risk factors such as gastrointestinal parasitic infection, anaemia and emaciation. The novel method of portable fluorometry was used for the first time to measure beta-carotene and retinol levels in a pastoral nomadic area. Moderate level blood retinol deficiency (< 0.7 mu mol/L) was observed in 5\% (CI 1-11) of nomadic, 29\% (CI 13-45) of semi-nomadic and 22\% (CI 8-35) of sedentary women. In children, 1\% (CI 0.1-4), 17\% (CI 9-25) and 28\% (CI 18-39), respectively, had moderate level blood retinol deficiency. In nomadic communities, women and children had blood retinol levels close to normal. Deficiency of retinol was strongly linked with lifestyle (nomadic, semi-nomadic and settled) among women and lifestyle and age among children. The results support an ecological linkage between human retinol levels and livestock milk retinol. This study shows the feasibility of portable retinol and beta-carotene measurement in human blood as well as human and animal milk under remote field conditions, but the approach requires further validation.},
  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{SchweigertBuchholzSchumacheretal.2001,
  author    = {Schweigert, Florian J. and Buchholz, Ingeborg and Schumacher, A. and Gropp, J.},
  title     = {Effect of dietary ß-carotene on the accumulation of ß-carotene and vitamin A in plasma and tissues of gilts},
  year      = {2001},
  language  = {en}
}
@misc{BrentenMorrisSaltetal.2014,
  author    = {Brenten, Thomas and Morris, Penelope J. and Salt, Carina and Raila, Jens and Kohn, Barbara and Brunnberg, Leo and Schweigert, Florian J. and Zentek, J{\"u}rgen},
  title     = {Energy intake, growth rate and body composition of young Labrador Retrievers and Miniature Schnauzers fed different dietary levels of vitamin A},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {603},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-41568},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-415681},
  pages     = {8},
  year      = {2014},
  abstract  = {Research in rodents has shown that dietary vitamin A reduces body fat by enhancing fat mobilisation and energy utilisation; however, their effects in growing dogs remain unclear. In the present study, we evaluated the development of body weight and body composition and compared observed energy intake with predicted energy intake in forty-nine puppies from two breeds (twenty-four Labrador Retriever (LAB) and twenty-five Miniature Schnauzer (MS)). A total of four different diets with increasing vitamin A content between 5.24 and 104.80 mu mol retinol (5000-100 000 IU vitamin A)/4184 kJ (1000 kcal) metabolisable energy were fed from the age of 8 weeks up to 52 (MS) and 78 weeks (LAB). The daily energy intake was recorded throughout the experimental period. The body condition score was evaluated weekly using a seven-category system, and food allowances were adjusted to maintain optimal body condition. Body composition was assessed at the age of 26 and 52 weeks for both breeds and at the age of 78 weeks for the LAB breed only using dual-energy X-ray absorptiometry. The growth curves of the dogs followed a breed-specific pattern. However, data on energy intake showed considerable variability between the two breeds as well as when compared with predicted energy intake. In conclusion, the data show that energy intakes of puppies particularly during early growth are highly variable; however, the growth pattern and body composition of the LAB and MS breeds are not affected by the intake of vitamin A at levels up to 104.80 mu mol retinol (100 000 IU vitamin A)/4184 kJ (1000 kcal).},
  language  = {en}
}