Effect of diet energy density and season on voluntary dry-matter and energy intake in male red deer

Food intake and growth of red deer is lower in winter than in spring and th is reduces the efficiency of venison production. Rumen capacity is also low er during winter and this may contribute to the reduced food intake and the refore growth. In the present study, we investigated the ability of deer to regulate food intake during winter and spring by feeding diets of differin g energy densities. Six groups of eight male red deer calves were housed indoors in separate pe ns. Each group teas given, ad libitum, a pelleted diet of a different energ y density (8.5, 9.0, 9.5, 10.0, 10.5 and 11.0 MJ metabolizable energy (ME) per kg dry matter (DM)for groups 1 to 6 respectively) but the same amount o f protein (156 g/kg DM). Food intake of each group was recorded every 2nd d ay and animals were weighed every 6 days from 17 May to 9 December. For sea sonal comparisons, winter was defined as 24 May to 31 August and spring as 1 September to 9 December. There was no difference (P > 0.05) between the mean live weights of the gro ups at any time during the Study. Liveweight gain (LWG) reached a minimum o n 4 July and was lower in winter than spring (161 v. 308 g/day, s.e.d. = 10 .0, P < 0 001). LWG was positively related (P < 0.001) to diet ME during wi nter DM intake (g/kg M-0.75 per day) and ME intake (MJ ME per kg M-0.75 per day) decreased until 16 July and increased thereafter Mean DM intake was l ower in winter than spring (83.5 v. 97.2 g/kg M-0.75 per day, s.e.d. = 2.05 , P < 0001). DM intake increased as diet energy decreased (P < 0.001) in wi nter and spring with a steeper slope (P < 0.05) in spring than winter ME in take was not related to diet ME (P > 0005) and was lower in winter than spr ing (0.82 v. 0.95 MJ/kg M-0.75 per day, s.e.d. = 0.25, P < 0001). Maintenan ce energy requirement (MEm) across groups and seasons was calculated to be 0.45 (s.e. 0.22) MJ ME per kg M-0.75 and the energy requirement for LWG (ME f) was 53 (s.e. 8.5) MJ/kg LWG. MEf was related (P < 001) negatively to die t ME during winter. In summary, deer consuming diets with a wide range of energy densities, alt ered their DM intake, resulting in similar energy intakes and growth rates on all diets. Animals seemed less able to achieve this compensation in wint er compared with spring when food intake increased to support the natural r ise in growth rate at that time. These results indicate that deer have targ et growth rates and/or energy intakes that change with season, and are defe nded by adjusting food intake.