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Mutations in the β-carotene oxygenase 2 (BCO2) gene can impair the function of the enzyme that breaks down carotenoids. As a result, gradual accumulation of unoxidized carotenoids in animal tissues gives them a yellow colour. The aim of the study was to determine the content of carotenoids, retinol and α-tocopherol in the liver, fat and milk of rabbit does with three different genotypes determined by AAT-deletion mutation at codon 248 of the BCO2 gene and to find out whether differences in the concentrations of the above compounds in the tissues and milk of the does affect reproduction parameters and the rearing rate of kittens. The experimental materials comprised 36 does, 12 of each genotype of the BCO2 gene, with their litters. Females with their litters were placed in individual cages, on deep litter. Between days 7 and 13 of lactation, samples of milk were collected from the does. The kittens stayed with their mothers until 35 days of age. After weaning, the does were sacrificed. Tissue samples of liver and perirenal fat were collected for chemical analyses. Additionally, based on samples taken from one female, RNA expression levels were determined from the mammary gland and liver, adipose tissue and skin. It was found that homozygous does with deletion at codon 248 of the BCO2 gene were characterized by considerably higher concentrations of xanthophylls and beta-carotene in the liver, adipose tissue and milk than does with the remaining genotypes. However, the differences in the content of the above compounds in milk had no influence on litter weight or the number and rearing rate of kittens. Additionally, RNA expression of the BCO2 gene was found in the mammary tissue of lactating doe and its level was similar to those noted in the liver and adipose tissue., (© 2019 Blackwell Verlag GmbH.)

The aim of this study was to determine whether farming leads to changes in gastrointestinal function and nitrogen metabolism in farmed mink (FA), as compared with their wild-living counterparts. Three digestibility and balance trials were carried out. Experiment I was performed in May, and experiments II and III were conducted in September 2011. Farmed mink with the standard coat colour were purchased from a production farm in south-eastern Poland. Feral mink were harvested using cages in the hunting grounds of the Polish Hunting Association, Branch in Olsztyn. The experimental materials comprised of the following: trial I - adult males (eight animals per group), trial II - young females (six animals per group), trial III-young animals (five males and five females per group). Food transit time was measured during digestibility trials, on 10 consecutive days. The coefficients of nutrient and energy digestibility and daily nitrogen balance values were compared between groups in each experiment. It was found that farming contributed to changes in gastrointestinal function and nitrogen metabolism in mink. Farmed animals were characterized by a longer bowel transit time, a tendency towards higher nutrient digestibility and higher nitrogen retention, which resulted from selection for higher productivity., (© 2012 Blackwell Verlag GmbH.)