The effects of plane of nutrition and environmental temperature on the energy metabolism of the growing pig

Abstract

1. Measurements of energy and nitrogen balances were made on thirty-eight individually housed pigs (initial body-weights 21–38 kg) at environmental temperatures of 10, 15, 20, 25 and 30° with four levels of feeding at each temperature. Values for energy retention (ER), protein (P) and fat (F) deposition and body weight gain (δW) were calculated at each temperature at metabolizable energy (me) intakes equivalent to once (M; 440 kJ/kg0.75 per d), twice (2M), three (3M) and four (4M) times the thermoneutral maintenance energy requirement.2. ER at each plane of nutrition increased with temperature to maximal values between approximately 20 and 25° ER was negative at four of the five environmental temperatures at M.3. P increased significantly with increase in me intake but was dependent on environmental temperatures only at intakes of M and 2M. The increase in P per unit increment in me intake decreased from 0.16 at 10° to 0.12 at 30°. The net efficiency of protein utilization also decreased with increase in environmental temperature from 0.54 at 10° to 0.39 at 30°.4. F increased significantly with increase in me intake, but was more temperature-dependent than P, increasing to maximum values estimated to be between 20 and 25° at each level of intake; F at 30° was less than that at 25°. The increase in F per unit increment in me intake decreased from 0.63 at 10° to 0.51 at 30°.5. The optimum temperature for ΔW was dependent upon me intake, varying from above 30° at M to less than 20° at 4M. The reduction in ΔW per 1° at 15° was also dependent upon the level of intake decreasing from 1.63 g/kg0.75 per d at M to -0.09 at 4M.6. For a 35 kg pig the reduction in P, as a result of a 1° decrease in temperature at 15° at an intake corresponding to 2.5M, was equivalent to a 4 g/d reduction in food intake; the corresponding equivalent for F was 28 g/d.