Modelling The Effect Of Ambient Temperature On Protein And Energy Metabolism And Utilization In Growing-Finishing Pigs

The effects of ambient temperature on performance, nitrogen and energy metabolism, protein (PD) and lipid deposition (LD), heat production (HP) and energy utilization were studied in Duroc x (Landrace x Large White) growing-finishing pigs according to a factorial design including four body weight ranges (20-40, 40-60, 60-80 and 80-100 kg) and nine temperature (5, 10,15, 20, 23, 26, 29, 32 and 35 ℃). High temperature trials: the performance, nitrogen and energy metabolism, PD, LD, HP and energy utilization of 20-100 kg growing-finishing pigs were measured in constant hot temperature (23-35 ℃), respectively; low temperature trials: the performance of 20-40 kg (10~20℃) and 60-80 kg (5~20℃) growing pigs were measured in constant low temperature, respectively; One hundred and eight pigs were divided into 27 treats with four animals per treat (2 castrated males and 2 entire females). Digestive and metabolic trials were conducted for 6-14 days from 28 to 32, 38 to 42, 68 to 72 and 78-92 kg BW, respectively. Twenty-two pigs (one male and one female per treat) were slaughtered at end experiments in 23, 29 and 35 ℃. Animals were individually housed in wire cages and had ad libitum access to diets and water.The results showed as follow:1. The VFI, ADG and F/G of growing-finishing pigs were significantly affected by high temperature (P<0.01). The effect of temperature was related to body weigh and temperature. The performance of 20-40 kg growing pigs was the best at 26 ℃. The other pigs' performance was the best in 23 ℃. The VFI, ADG of 20-100 kg pigs reduced 65g/d/℃ (or -40%) and 30 g/d/℃ (or -51%) and F/G of them increased 0.05/d/℃ (or +21%) as environmental temperature increased from 23 to 35 ℃, respectively.2. VFI and F/G of growing-finishing pigs were significantly affected by low temperature (P<0.01), but the effect of low temperature on ADG of them was not significant (P>0.05).The VFI and F/G of 20-40 kg growing pigs increased 44g/d/°C (or +28%) and 0.08/°C (or +35%), and ADG of them decreased 4g/d/°C(or -6%)as temperature dropped from 20 to 10 °C respectively. In 60-80 kg pigs, VFI and F/G increased 34 g/d (or +22%) and 0.09 (or +41%) (P<0.01), respectively, and ADG decreased 6 g/d (or -13%) (P>0.05) for 1 °C drop in temperature between 20 and 5 °C.3. For 20-100 kg growing-finishing pigs, the relationship between VFI, ADG and F/G and temperature (23-35 °C) can be described in linear or quadric functions (p<0.01) and were affected by interactive effect of temperature and body weight. Equations for prediction of VFI, ADG and F/G according to T and BW are proposed. The negative effects of hot temperature on the growth and economic effectiveness in growing-finishing pigs were more severity than that of low temperature.4. Increasing ambient temperature from 23 to 35 °C resulted in the increase of the apparent digestibility coefficients of energy in diets (87.1-89.0%, P<0.05), but the ratios of ME/DE (0.981 to 0.984) were not affected by temperature. Similarly, high temperature resulted in the increase of the apparent digestibility coefficients of nitrogen in diets (83.7-87.9%. P<0.01), whereas BV (0.57-0.62) and NPU (0.50-0.54) of diet protein were not different among several temperature treats (P>0.05).5. Modelling effect of high and low temperature on ME intake (MEI) of 20-100 kg growing-finishing pigs was different and influenced by interaction between temperature and body weight. The MEI of pigs in hot reduced as high as 0.016 MJ/kg BW per degree. The energy cost of cold thermogenesis when the ambient temperature is low the animal's comfort temperature increased probably 0.029 MJ/kg BW per degree for 20-40 kg pigs and 0.0069 MJ/kg BW per degree for 60-80 kg pigs. The amount of increasing energy at cold was lower than that of decreasing energy at hot in same body weight pigs. The results propose that energy requirements of growing-finishing pigs in hot and clod environment were adjusted using different simulation equations, as follow:?Simulation equations of ME requirement in high and low temperature For pigs from 20 to 100kg BW in 23-35 "C:MEI(MJ/d)=-26.8112+1.5723T+1.2684BW-0.02748T2-0.005215BW2-0.01570TxBW(R2=0.96, RSD=1.29)For pigs from 20 to 100kg BW in 5-23 V:MEI(MJ/d)=23.086-0.539T+0.297BW (R2=0.927, RSD=1.92) ?Changing rate(R%): For pigs from 20 to 100kg BW in hot temperature (23-35 °C):R%=0.0186 (OT-Ta)-0.00115 (OT-Ta)2(R2 = 0.99, RSD=0.12) For pigs from 20 to 100kg BW in cold temperature(5~23°C):R%= 0.0196(OT-Ta) (R2 = 0.94, RSD=0.0462) Adjustment MEI(MJ/d)= MEIOt+MEIOtXR%6. Increasing ambient temperature decreased protein (PD) and lipid deposition (LD) in a quadratic manner. However, the response of LD was higher than that of PD. With pigs given food ad libitum during 20 to 100 kg phase, an increase in temperature from 23 to 35 °C reduced daily PD by 51% (58 vsll9 g/d), LD by 75% (52 vs 209 g/d). Hot stress makes pigs leaner.7. High temperature had a significant influence upon heat production per unit feed and decreased the efficiency of energy utilization. From linear regression equations relating HP (MJ/kg Feed) to T, individual estimates of extra thermoregulatory heat production (ETH) in hot temperature were determined. The values of ETH in 20-40, 40-60, 60-80 and 80-100 kg pigs were 0.18> 0.29> 0.30 %\ 0.34MJ/kg feed/°C, respectively. Pigs will reduce VFI (or MET) to remove ETH in hot environment which corresponded with the results of feeding and metabolic experiments.