The response of growing pigs to amino acids as influenced by environmentaltemperature - 2. Lysine

Two experiments were conducted to measure the effects of a range of dietary lysine concentrations and environmental temperatures on the performance of pigs grown from 13 to 25 kg live weight. In both experiments 48 Large Whit e X Landrace entire male pigs were assigned at 13 kg to one of six dietary lysine treatments (13.8 (L1), 11.8 (L2), 9.6 (L3), 7.6 (L4), 5.6 (L5) g/kg and L5 + supplemented lysine (L6)) and one of four temperature treatments ( 18, 22, 26 and 30 degrees C). Animals were given ad libitum access to food until 25 kg live weight. There were significant differences in the rates of growth between dietary and temperature treatments with the highest gains o n L2 (0.597 (s.e. 0.020) kg/day) and at 18 degrees C (0.549 (s.e. 0.018) kg /day). Food intake (FI) increased significantly (P < 0.001) with decreasing lysine content, reached a maximum (L4) and then declined (L5). An increase in the supply of lysine in the diet resulted in significant increases (P < 0.001) in the gain per unit of food (FCE). There was an indication (P < 0. 10) that the response in FCE to dietary lysine was dependent on the tempera ture, with maximum FCE being obtained at 22 degrees C on L1 (647 (s.e. 18.5 ) g gain per kg food). Dietary treatment had a significant effect (P < 0.00 1) on both the rate of protein (PX) and lipid deposition (LX) irrespective of the temperature. There was a 0.60 reduction in PR and a 1.36 increase in LX in pigs given L5 compared with those given LI. Similar trends occurred in the empty body protein and lipid contents at 25 kg live weight. Both tem perature and dietary lysine levels had a significant (P < 0.05) effect on f etal heaf loss (THL). The response in THL was similar to that observed in F I. The efficiency of lysine utilization at 22 degrees C was significantly ( P < 0.05) higher than at the remaining temperatures. The mean efficiency fo r pigs between 13 kg and 25 kg live weight was 0.64 (s.e. 0.05). In general , growth and food intake responses to dietary lysine level were independent of environmental temperature.