Acta Veterinaria Hungarica 53 (3), pp. 309–318 (2005) 0236-6290/$ 5.00 © 2005 Akadémiai Kiadó, Budapest RELATIONSHIP OF RETINOID AND CAROTENOID METABOLISM WITH CAECOTROPHY IN RABBITS Annamária KERTI 1,2∗ , L. BÁRDOS 1 , J. DELI 3 and P. OLÁH 3 1 Faculty of Agricultural and Environmental Sciences, Szent István University, H-2103 Gödöllő, Páter K. u. 1, Hungary; 2 Research Institute for Animal Breeding and Nutrition, Herceghalom, Hungary; 3 Faculty of Medical Science, University of Pécs, Pécs, Hungary (Received November 3, 2004; accepted April 18, 2005) The relationship of retinoid and carotenoid metabolism with caecotrophy was studied in adult female New Zealand White rabbits kept in individual meta- bolic cages. Caecotrophy was prevented by the use of plastic collars. The dry mat- ter, crude protein, fibre, fat and ash contents of hard and soft faecal samples were determined. The retinoid (retinol and retinyl palmitate) and carotenoid (canthax- anthin, β-carotene, β-cryptoxanthin, lutein and zeaxanthin) levels of the blood, liver, kidney, caecal content and faeces were also measured by high-performance liquid chromatography (HPLC). The prevention of caecotrophy resulted in a sig- nificant decrease of blood retinol (P < 0.001) and retinyl palmitate (P < 0.01) con- centration but it did not cause any significant change in the retinol and retinyl palmitate contents of the liver and kidney. The caecal content (25.78 ± 6.87 µg/g) and the soft faeces (34.52 ± 10.48 µg/g) contained the retinoids in similar amounts. Various carotenoids were found in considerable amounts in different types of faeces, while in the tissues (blood, liver and kidney) these pigments did not occur in substantial amounts. Total carotenoid concentration was similar in the caecal content (11.23 µg/g) and in the caecotroph (13.85 µg/g). On the basis of the results it can be assumed that the retinoid content of rabbit feed could be low- ered in the presence of adequate caecal function and caecotrophy. Key words: Retinoid, carotenoid, metabolism, caecotrophy, rabbit In the present day, retinoids (vitamin A) and provitamin A carotenoids are a major focus of research around the world owing to their cytoprotective, immu- nostimulating and antitumour effects. Retinoids are known to be involved in fetal development and in regulating the proliferation and differentiation of many cells and tissues throughout life. They are also essential for the maintenance of normal reproductive processes and immune response (Blomhoff et al., 1990). In the past decade the effects of high or low dietary vitamin A levels on growth and reproductive performance were investigated in rabbits. High dietary ∗ Corresponding author; E-mail: Kerti.Annamaria@mkk.szie.hu; Fax: +36 (28) 410 804