Fatty acid profile, carcass traits and growth rate of red deer fed diets varying in the ratio of concentrate:dried and pelleted roughage, and raised for venison production

An experiment was conducted with 180 weaned red deer stags to determine the effects of diets varying in the ratio of concentrate:dried pelleted roughage (concentrate:roughage ratio) on growth performance and carcass traits in venison production. The animals were raised outdoors in nine denuded deer parks. Sixty animals (20 per park) were assigned, according to a completely randomized design, to one of three experimental diets with the following roughage:concentrate ratios: 75:25, 50:50 and 25:75. Results of a 140-day performance study revealed that live weight gain (LWG) was positively and linearly (P < 0.01) related to the proportion of concentrate in the diet. Voluntary food intake decreased linearly (P < 0.01) as the proportion of concentrate increased. Results of rib dissection on animals slaughtered at a fixed body weight (125 kg) revealed a linear (P < 0.01) increase in carcass fatness as the proportion of concentrate increased; there were no effects on yield of lean meat or bone. Increasing the proportion of concentrate in the diet altered the fatty acid composition of carcass fat. This was characterized by a linear increase (P < 0.01) in C18:1 (monounsaturated fatty acid, MUFA) and a linear decrease (P < 0.01) in C18:3, with no effect (P > 0.05) on the content of C18:2 or the ratio of C18:2 to 18:3. When compared to the 75:25 ratio, the 50:50 roughage:concentrate diet resulted in a decrease in the content of conjugated linoleic (CLA) in carcass fat. A further increase in the proportion of concentrate caused an increase in carcass CLA, resulting in a significant (P < 0.01) quadratic response. This research indicates that a high level of grain feeding is an effective nutritional strategy to enhance growth performance of red deer. The negative impact of grain feeding on carcass fat was offset by desirable changes in the content of MUFA and CLA.