The effect of extensive feeding, confinement and diet supplementation with a-tocopheryl acetate (100 mg/kg) on the fatty acid composition and tocopherol concentration of microsome extracts and their susceptibility to oxidation was studied in Iberian pigs. The diet of pigs raised extensively was mostly composed of acorn and grass. The a-tocopherol contents of acorn and grass were 20 and 171 mg/kg dry matter, respectively. Microsomal fatty acid composition showed no differences among groups. Pigs feeding extensively had a higher concentration of a-tocopherol in muscle and microsomes than pigs given mixed diet with the basal level of a-tocopheryl acetate (P < 0·05) but lower values than pigs given supplementary levels (100 mg/kg) (P < 0·05). Microsomal fractions from pigs given mixed diet with a basal level of a-tocopheryl acetate were significantly more susceptible to iron-induced lipid oxidation than extract from pigs given diets containing a supplementary level (P < 0·05). Microsomal extracts from pigs feeding extensively had the lowest oxidation rate (P < 0·05), suggesting that other dietary constituents may play a role in the stabilization of microsomal lipids.

Farm mink (Mustela vison) have been selected on the basis of their behaviour towards man since 1988 at the Danish Institute of Agricultural Sciences and in this study were offered the possibility to mate 1 week earlier than usual. The objective was to investigate if the behaviour-related selection has affected the reproduction of the farm mink, measured as mating willingness and reproductive success. The animals belonged to three breeding groups: A: selected for curious/confident reactions (17 males, 73 females), B: selected for timid reactions (17 males, 74 females), and C: selected without any demands on reactions towards humans (18 males, 73 females). The time when an average of 50% of the population were mated was 3-6 days for group A; thus the confident were mated 1·7 to 2·1 days earlier than the timid (B) and the control (C) animals. The length of gestation was shorter in group A (46·0 (s.d. 3·0) days) than in group C (47·6 (s.d. 3·6) days) but not different from group B (47·0 (s.d. 3·2) days). Group C had a lower kit mortality from birth to day 50 (11·3%) than groups A and B (20·4 to 21·2%). No significant differences were found between the groups regarding the frequency of successful matings, the ratio of remated females, number of interrupted matings, barren females or litter size. It is concluded that 8 years of selection has led to the development of reproductive differences primarily in the time of mating readiness, whereas the differences seen in kit loss may be related more to random effects.