The Effects Of High Ambient Temperature On Mitochondrial Function And Breast Meat Quality Of Broilers

In modern time, the poultry industry has been faced with the increasing problem of pale, soft, and exudative meat (PSE). Heat exposure induced poultry to exhibited PSE meat characteristics, but the mechanism of poultry PSE meat induced by high temperature is unclear. Six experiments were conducted to research the reason that detrimental effects of high temperature on broilers breast meat quality.1 Effect of high temperature and oxidative stress on mitochondrial function of broiler muscle incubated in vitroThe M. fibularis longus muscles of sixteen broilers (14days, male) were isolated immediately after anaesthesia. The muscles of eight birds were incubated in different temperature (41.5℃VS 44.5℃) and the muscles of eight birds were incubated in pyrogallol (0 VS 0.3mM) in vitro. After incubated 2h, the mitochondrial was isolated from the muscle to investigate the mitochondrial function. Higher incubated temperature significantly elevated muscle mitochondrial H2_O2 production (24.6%) and inhibited Ca²⁺ -ATPase activity (19.6%). Heat exposure was effective in elevating the lipid peroxidation (P<0.0001) and lactate content (P=0.0368) in incubated muscle. The loss of creatine kinase (CK) and lactate dehydrogenase (LDH) from muscle were significantly elevated by heat exposure (P=0.0009, P=0.0114). Oxidative stress (0.3mM Pyrogallol) has similar effects on mitochondrial H₂O₂ production, Ca²⁺ -ATPase activity, lipid peroxidation, lactate content and the loss of CK and LDH as heat exposure. The results indicated that high temperature inhibited Ca²⁺-ATPase activity by ROS.2 Effect of Cyclic high temperature on mitochondrial function and breast meat quality of broilersOne hundred and eighty 4-week-old broilers were allocated to three treatments according to following design: 25V, ad lib. feeding (Control);25℃, pair-feeding with the high cyclic group (PF);and 28/34℃ daily cyclic high temperature, ad lib. feeding (Cyclic). Broilers were kept in three environment control chambers for three weeks. Heat exposure significantly elevated rectal temperature and hepatic mitochondrial H₂O₂ production(P<0.05), significantly inhibited muscular and hepatic mitochondrial Ca²⁺ -ATPase activity(P<0.05). Increased lactate content in breast muscle was found under cyclic high temperature (P=0.0703). At 49 day, Heat exposure significantly decreased the pHi of breast muscle (P<0.05), increased drip loss, L*and shear force (P<0.05). At 25℃, pair-feeding had no significant effects on mitochondrial H₂O₂ production, Ca²⁺ -ATPase activity, muscle pH, L*, and drip loss(P>0.05), which indicated that the effects of cyclic high temperature on mitochondrial function and breast meat quality of broilers were not associated with the reduction of feed intake induced by ambient high temperature.3 Effect of acute high temperature on mitochondrial function and breast meat quality of broilersA total of one hundred and sixty male broilers of 49d were randomly divided into four groups with eight replicate pens per group. They were raised in four different ambient temperatures: 25 °C, 32 °C, 35 "C and 38 °C for 2h, then, the mitochondrial function and breast meat quality of broilers were determinated.At 35 °C and 38 X? for 2 hours, there were significant increase in the rectal temperature, mitochondrial H2O2 production, hepatic mitochondrial MDA and protein carbonyl content of broilers (P<0.05). Inhibited mitochondrial Ca2+-ATPase activity and increased lactate content in breast muscle were found under 35*C and 38T2(/*<0.05). Acute high temperature (35°C and 38"C) significantly decreased pH;and sarcoplasmic protein extractability (PO.05), significantly elevated L*, drip loss and cooking loss (P<0.05). At 32°C for 2h, the mitochondrial H2O2 production, Ca2+-ATPase activity and lactate content were not significantly effected (P>0.05). There were not significant effects on meat color, drip loss and cooking loss (P>0.05) under 32°C.4% Effect of acute high temperature and recovering time on mitochondrial function and breast meat quality of broilersOne hundred and twelve male broilers (55d of age) were randomly divided into eight groups and kept at 35 "C for 2 hours, then, the ambient temperature was decreased to 25 *C. Two birds from each group was killed, the breast meat and liver were separated quickly at 6 time point: before high temperature, 35"C for 2h, 25*C for lh, 25"C for 2h, 25*C for 4h, 25*C for 8h.After recover at 25 V for 1 hour, the rectal temperature, hepatic mitochondrial H2O2 production and muscular lactate content were still higher(P<0.05), and the mitochondrial Ca2+-ATPase activity was still lower than that in pre-heat-stress (PO.05). At this moment, the pHi and sarcoplasmic protein extractability were lower and L*, drip loss, cooking loss of breast muscle were higher than that in pre-stress (P<0.05). After recover at 25 V for 2 hour, the lactate content was decreased to normal level (P>0.05), but the mitochondrial H2O2 production and Ca2+-ATPase activity were not restored to normal level (i*<0.05). At this moment, the meat quality indexes besides L* and sarcoplasmic protein extractability recovered to normal level (P>0.05). After recover at 25 *C for 8 hours, the mitochondrial function and breast meat quality of broilers were restored to normal level.5 â– > Effect of oxidative stress on the mitochondrial function and breast meat quality of broilersOne hundred and eight male broilers (53d of age) were divided into three groups. They were separately intraperitoneal injected of 0.9% NaCl (control group), 30mg CHPO/Kg BW and 60mg CHPO/Kg BW for three days. Then the breast meat and liver were separated immediately after death to measure the mitochondrial function and breast meat quality.Oxidative stress was induced by intraperitoneal injection of cumene hyaroperoxlde (CHPO). Oxidative stress significantly elevated hepatic and muscular mitochondrial H2O2 production (PMX0196, â– P=0.0395), significantly inhibited hepatic and muscular mitochondrial Ca2+-ATPase activity (/*=0.0I5;P=O.O388). Lactate content was also increased by CHPO (PO.0001). CHPO decreased muscle pHj CP=O.OO18) and sarcoplasmic protein extractability (P=0.0284), increased L* (i>=0.0002), drip loss (P=O.OO58), cooking loss (/M).OO25) and shear force (iM).OO29). Effects of high ambient temperature on mitochondrial function and meat quality were similar as that of oxidative stress, which indicated that inhibited mitochondrial Ca2+-ATPase activity was associated with oxidative stress.6, Effect of VE on mitochondrial function and breast meat quality of broilers under high temperatureTwo hundred and eighty eight male broilers were randomly divided into three groups. From 21 to 28d of age, the birds of one group were fed the diets adding VE. From 29 to 49d of age, the broilers were exposed different temperature, thus three groups were as follow: high temperature (HT), high temperature + VE (HT+ VE), and the control group (normal temperature, NT).Addition of VE (lOOmg/Kg) significantly alleviated detrimental effects of high cyclic temperature on mitochondrial H2O2 production, Ca2+-ATPase activity and lactate content in breast muscle of broilers (P<0.05), and the meat quality of broilers was also increased by VE, which indicated that oxidative stress may inhibited the mitochondrial Ca2+-ATPase activity.The results from high temperature experiments indicated that high ambient temperature increased lactate content by inhibited mitochondrial Ca2+-ATPase activity, and then induced protein denaturation, result in paler meat and lower water-holding capacity.The results from oxidative stress experiments indicated that high ambient temperature inhibited mitochondrial Ca2+-ATPase activity by oxidative stress, increased lactate content and then induced protein denaturation, result in paler meat and lower water-holding capacity.