The breeding season in temperate species of deer is characterized by the rut, a period of intense sexual activity when the male eats very little and competes for access to females. Males have been reported as losing proportionately up to 0·30 of live weight over a 6- to 8- week period. The majority of the live-weight loss is accounted for in loss of depot fat, with smaller losses in muscle reserves. The effects of body composition, hormone status and season on these changes in fat and muscle reserves were examined in mature fallow bucks (Dama dama).

The experiment was conducted in two stages, the ‘rut’ (February to May), and ‘spring’ (June to November). For the ‘rut’ period, bucks were randomly allocated to either ad libitum feeding, entire (HiEnt), matched group feeding, castrated (CAST), or entire bucks restricted to 7·6 kg dry matter per week (LoEnt) treatment groups (no. =4, 4 and 6, respectively). Three bucks from each of the HiEnt and LoEnt groups were selected for the ‘spring’ period. Bucks were given food ad libitum until mid October, whereupon they were restricted to 2·5 kg dry matter per week for 4 weeks (SPRING). Group food intake and individual live weights were measured weekly throughout both, periods. Body composition was measured by computed tomography on five and three occasions during the ‘rut’ and ‘spring’ stages, respectively.

Comparisons of the relative losses of total fat and muscle relative to empty body weight (EBW) using the allometric model (y = aXb) revealed significant treatment differences. HiEnt bucks had a high relative rate of fat and a low rate of muscle mobilization (b = 5·23 and 0·38, respectively). Only the CAST group had lower (P < 0·1) b coefficient for fat than the HiEnt group at 2·79. The LoEnt group was the only group in which the b coefficient for muscle (at 1·07) was not significantly lower than 1·0. Visceral organ weight was lost at the same rate as EBW across all treatments. There was no net loss or gain of bone for any treatment group as the b coefficients were not significantly different from zero. Fat depots were analysed relative to the total fat depot using the allometric model. The HiEnt group displayed a pattern of fat mobilization whereby the external depots were mobilized at the greatest relative rate and the internal fat depots at the lowest rate (b coefficients were 1·86, 1·23 and 0·68 for the subcutaneous, intermuscular and internal fat depots, respectively). CAST and SPRING groups were not significantly different from HiEnt bucks in the relative mobilization of fat depots. All fat depots in the LoEnt group were mobilized at the same relative rate as total fat, as the b coefficients were not significantly different from 1·0.

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.