The effects of environmental temperature on the growth and metabolism of pigs given different amounts of food

I .Eighteen pigs were studied at environmental temperatures of 5", 13" and 23", with three levels of' feeding at each.2. Energy losses in the faeces and urine were measured throughout as the pigs grew from 20 to 90 kg; respiratory exchange was measured intermittently, for an average of ten 24 h periods for each pig.3. From regressions of heat production, energy retention and water-vapour production on body-weight, estimates of these quantities were made at weights of 25, 3 j , 4 j , 55, 65, 75 and 85 kg. 4. Digestibility of energy was unaffected by daily food intake, hut increased by 0.12 percentage units per degree rise of temperature.The mean urine energy loss was 30.5 kJ/MJ digestible energy.I t was not significantly affected by temperature.Methane production was not affected by temperature but fell by 0.086 F 0.027 kJ/MJ apparent metabolizable energy (ME) with each g/kg0'73 increase in daily food intake.5. Heat production increased with body-weight and daily food intake and with falling temperature.',There was a significant interaction between the last two factors.These effects were summarized in a general equation.2-2 MJ (3.24 i: 0-52 Mcal) per g,/kgo"s increasc in daily food intake.This corresponded to a reduction of 1.4 d in the time taken to grow from 20 to 90 kg.7. Total energy retention throughout the experiment, estimated from energy balance results, was in close agreement with that estimated by comparative slaughter.8. The net availability of ME was 72% at 23': at lower temperatures it increased with bodyweight to values in excess of 80 ?".9. Estimates of the energy maintenance requirement at 23' were in good agreement with others in the literature.In terms of body-weight, W , measured in kg, the tnean values (kJ/d) were 1761 W0'5' at so, 1473 lZi0'57 atr3" and 891 W0"' at 23'; inunits of lrcalld the corresponding coefficients of W0.57 were 421, 352 and 213.6. Total heat production during the experiment fell by 13-6