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A framework for log-linear models with context specific independence structures, i.e. conditional independencies holding only for specific values of the conditioning variables is introduced. This framework is constituted by the class of split models. Also a software package named YGGDRASIL which is designed for statistical inference in split models is presented. Split models are an extension of graphical models for contingency tables. The treatment of split models includes estimation, representation and a Markov property for reading off independencies holding in a specific context. Two examples, including an illustration of the use of YGGDRASIL are presented. [Copyright &y& Elsevier]

We investigated the effects of dietary copper and vitamin E in diets containing 6% rapeseed oil on the performance and the antioxidative and oxidative status of growing pigs. The 10 dietary treatments consisted of a basal diet (9 mg of vitamin E/kg feed, 15 mg of Cu/kg feed), the basal diet ² 6% rapeseed oil (Diet 1; 18 mg of vitamin E/kg feed, 15 mg of Cu/kg feed), and Diet 1 plus supplements of vitamin E (0, 100, and 200 mg of dl-α-tocopheryl acetate/kg feed) and copper (0, 35, and 175 mg of Cu/ kg feed) in a 3 × 3 factorial arrangement of treatments. Eight or nine pigs were given ad libitum access to each diet from 25 to 100 kg of live weight. The inclusion of rapeseed oil tended (P< .10) to improve ADG and feed utilization. Compared with the addition of 35 mg of Cu/kg, the addition of 175 mg/kg improved growth rate and increased feed intake early in the experiment, but, over the total experiment, neither 35 nor 175 mg of Cu/kg affected performance. Compared with the addition of 100 mg of vitamin E/kg or no addition, the addition of 200 mg/kg reduced ADG over the total experiment (P= .05). The antioxidative and oxidative status of the pigs was evaluated in terms of blood and liver concentrations of antioxidants (α-tocopherol, ascorbic acid, vitamin A, superoxide dismutase, glutathione peroxidase), prooxidants (Cu), concentrations of lipids (triglycerides and cholesterol), fatty acid composition, thiobarbituric acid-reactive substances (TBARS), and clinical chemical (creatine kinase and glutamate-oxaloacetate-transaminase) and hematological variables that indicate the level of oxidative stress. There were no vitamin E deficiency signs or increased oxidative stress in pigs fed low dietary vitamin E levels, and no prooxidative effect of Cu was found. Increasing dietary levels of vitamin E increased the concentration of α-tocopherol in plasma and liver. Supplementation with Cu increased liver concentrations of Cu and αtocopherol. The progression in liver TBARS was reduced by the addition of vitamin E and Cu. The addition of rapeseed oil changed the fatty acid composition of liver, increased α-tocopherol concentration in plasma and Cu concentration in liver, and reduced the rate of lipid oxidation in liver. In conclusion, even though the effects were minor, vitamin E, Cu, and rapeseed oil improved the antioxidative status of the live pigs.