Energy intake and patterns of growth for male and female fallow deer of two genotypes, between 10 and 21 months of age

European (no. = 36) and hybrid (1/4 Mesopotamian, 3/4 European; no. = 36) f allow deer (Dama dama) were evaluated for weight gain and energy intake fro m 10 to 21 months of age. Twelve each of bucks, does and castrated males (h aviers) were tested for each genotype, in both concentrate-fed and pasture- based feeding systems. Based on weekly weighing hybrids (H) in each of the sex classes grew more rapidly (5 g/day across all groups) than the European (E) fallow deer (P < 0.05). Haviers given concentrates grew significantly faster than pasture-fed haviers (P < 0.01), whilst does grown on pasture gr ew significantly faster than those given concentrates (P < 0.01). There was no significant difference in pattern of growth between bucks on pasture an d those given concentrates (P > 0.05). Does grew significantly less (P < 0. 01) than bucks and haviers in spring, summer and winter but environmental d ifferences between years could not be accounted for in the analysis. Animals of all sexes and genotypes experienced rapid growth from 10 to 12 m onths of age (spring) and this was associated with energy intakes according to metabolic body weight(M-0.75) these ranging between 0.8 and 1.1 MJ meta bolizable energy (ME) per kg M-0.75 per day. There were significantly (P < 0.01) higher levels of energy consumed by H does and haviers in the summer compared with their E counterparts but this was not associated with greater growth rates. However, H does had significantly higher (P < 0.01) dressing proportions at slaughter than E does. The energy intake on a metabolic bod y weight basis for most groups declined to between 0.7 and 0.8 MJ ME per kg M-0.75 per day from 12 to 21 months of age, except for the does, which dec lined even further to between 0.5 and 0.6 MJ ME per kg M-0.75 per day from 17 months of age. There were no significant differences between E and H deer for energy intak es per M-0.75, and H deer were slightly more energy efficient than their E counterparts in terms of growth rate in relation to annual gross energy int ake. The food intake : weight gain ratio increased considerably for both ge notypes after 14 months of age, indicating the desirability for slaughterin g as soon as animals reach the target live weight. It was concluded that th e crossbreeding system described is production efficient and produced offsp ring that reached slaughter weight sooner than E fallow deer and thereby pr oduced carcasses with a greater wholesale value than their E counterparts o f the same age.