Effect of ammonium chloride on the bicarbonate buffer system in heat-stressed broilers

1. The effects of ammonium chloride (NH4Cl) on the bicarbonate buffer system and plasma lactate in heat-stressed broilers were investigated. 2. The infusion of a 10 g/l solution of NH4Cl into the crop during a 90 min thermoneutral period produced a metabolic acidosis resulting from a reduction in blood bicarbonate concentration. Blood bicarbonate continued to decrease in NH4Cl-treated birds and reached values which were 30% of controls by the end of a 90 min heat stress period. 3. By the end of heat stress, plasma lactate concentrations were lower in NH4Cl-infused birds than in controls.     

Effect of heat stress on oxidative stress, lipid peroxidation and some stress parameters in broilers

1. This study was conducted to determine the effects of heat stress on fearfulness, leucocyte components, oxidative stress and lipid peroxidation in two commercial broiler strains, Cobb (C) and Ross (R). 2. At 36 and 37 d of age birds were exposed to 38 +/- 1 degree C for 3 h. Rectal temperatures, duration of tonic immobility (TI), haematocrit values, proportions of leucocyte components (heterophil, lymphocyte, basophil, eosinophil, monocyte), malondialdehyde (MDA) concentrations and antioxidant enzyme activities (CAT, SOD, GPx) of all the birds were determined, before and after heat treatment. 3. Rectal temperatures increased and haematocrit values decreased in birds exposed to heat stress. Heat stress caused a significant increase in heterophil/lymphocyte and in basophil ratios. 4. Exposing birds to heat stress increased duration of TI, suggesting heat-stressed birds tended to be more fearful. 5. Heat stress resulted in a significant Genotype x Treatment interaction for MDA concentration. CAT, SOD and GPx activities; MDA concentrations in heat-stressed R strain birds were greater than in heat-stressed C strain birds.     

NH_4Cl和NaHCO_3对肉用仔鸡慢性热应激的影响

３２０ 羽１ 周龄健康肉用雏鸡被随机分成４ 组, 经１ 周的适应后进行试验。组Ⅰ、组Ⅱ、组Ⅲ和组Ⅳ的日粮处理分别为： 基础日粮（Ｂ, 对照组） , Ｂ＋ ０－５ ％ ＮａＨＣＯ３ , Ｂ＋ ０－５ ％ ＮａＨＣＯ３ ＋ １ ％ ＮＨ４Ｃｌ 和Ｂ＋ １ ％ ＮＨ４Ｃｌ。试验为期５ 周。研究日粮中添加ＮａＨＣＯ３ 和ＮＨ４Ｃｌ 对慢性热应激肉用仔鸡的血液ｐＨ、ＣＯ２ 分压（ＰＣＯ２） 及生产性能的影响。结果表明： 在慢性热应激（２３ ～３５ ℃） 条件下, 肉用仔鸡未发生呼吸性碱中毒, 组Ⅱ的血液ＰＣＯ２高于对照组（ Ｐ＜ ０－０１） , 增重比对照组多９－４９ ％ ; 组Ⅲ血液ｐＨ 低于组Ⅰ和组Ⅱ（ Ｐ ＜ ０－０１） , 血液的ＰＣＯ２ 高于组Ⅰ和组Ⅳ（ Ｐ ＜ ０－０１） , 增重比对照组多８－１９％ 。组Ⅳ的血液ｐＨ 值极显著低于对照组（ Ｐ ＜ ０－０１） , 比对照组少增重２－５ ％     

Behavioural and physiological responses of three chicken breeds to pre-slaughter shackling and acute heat stress

1. The aim of this study was to compare the behavioural and physiological responses to hanging and acute heat stress in three different chicken breeds. Chicks were obtained from a slow-growing French 'Label Rouge' line (SGL), a fast-growing standard line (FGL) and a heavy line (HL). The SGL, FGL and HL birds were slaughtered at their respective market ages of 12, 6 and 6 weeks, in an attempt to achieve similar body weights. Before stunning, birds were either shackled by their legs on the moving line for 2 min (shackling stress: SH) or placed in a room at 35 degrees C and 60% of humidity for 3.5 h and then shackled for 2 min (acute heat stress plus shackling: H + SH) or subjected to minimal stress by shackling for 10 s before stunning (control group: C). 2. Bird physiological responses to the three pre-slaughter treatments were estimated by measuring blood corticosterone, glycaemia, creatine kinase activity, acid-base status and electrolyte concentration as well as lactate content and glycolytic potential in the breast (Pectoralis major) and thigh (Ilio tibialis) muscles. Behavioural responses to shackling stress were evaluated by measuring wing flapping duration, straightening up attempts and vocalisations. 3. Blood corticosterone was higher in SH and H+SH groups than in the C group, regardless of genotype. The struggling activity on the shackle line differed among chicken breeds. It was more intense and occurred more rapidly after hanging in the SGL birds than in both other breeds. Furthermore, SGL struggling activity was not affected by hanging duration while it increased with hanging duration in FGL and HL birds. 4. Wing flapping duration was negatively correlated with blood pH, bicarbonate concentration and positively correlated with breast muscle lactate content, indicating that struggling stimulated antemortem glycolysis activity in breast muscle. Acute heat stress affected blood Ca2+ and Na+ concentration and increased glycaemia and glycolytic potential of thigh muscle. 5. Both acute heat stress and shackling before slaughter were experienced as stressful events by all types of birds.     

Lack of peripheral sympathetic control of uterine blood flow during acute heat stress

Peripheral alpha- and beta-adrenergic control of uterine blood flow (UBF) during acute heat stress of the gravid ewe was investigated. An electromagnetic blood flow probe was surgically implanted around the left miduterine artery and catheters inserted in the left carotid artery and right jugular vein in ewes between d 120 and 130 of gestation. Four or more days postsurgery, ewes were fitted with instruments to measure rectal temperature (Tr), heart rate (HR), respiratory rate (RR), blood pressure (BP) and UBF. One-half hour after instrument calibration, a 15-min thermoneutral control period was initiated with carotid artery blood samples taken at 5-min intervals for pH and PCO2 determinations. Ewes were then subjected to a heat challenge that reached 40 C at 2 h. All physiological data were recorded every 5 min as 1-min mean values. In seven experiments on five ewes, an alpha-adrenergic blocking drug, phenoxybenzamine (PB) was infused at 1 mg/min for 15 min subsequent to maximum depression of UBF. A beta-adrenergic blocking drug, propranolol (PR) was infused at .35 mg/min for 15 min in eight experiments on five ewes. Analysis of variance comparisons were made between the control period and heat stress infusion periods within the PB and PR experiments. Further comparisons were made between the start and 5, 10 or 15 min of PB or PR infusion in order to test drug effects during an acute heat stress. Rectal temperature HR, RR and arterial pH were higher (P less than .05) at the start of PR and PB infusions than during the thermoneutral control period.(ABSTRACT TRUNCATED AT 250 WORDS)     

The Effect of Resuscitation Technique and Pre-Arrest State of Oxygenation on Blood–Gas Values during Cardiopulmonary Resuscitation in Dogs

Large mongrel dogs were anesthetized, instrumented, and subjected to electrically induced ventricular fibrillation after breathing either 100% oxygen (O2) or 10% O2 and 90% nitrogen for 10 minutes before arrest. Four minutes after arrest, open chest cardiopulmonary resuscitation (CPR) or intermittent abdominal compression closed chest CPR was initiated and continued for 20 minutes, at which time defibrillation was attempted. Central arterial and mixed venous blood samples were collected serially for the measurement of pH, carbon dioxide partial pressure (PCO2), and O2 partial pressure (PO2), and calculation of bicarbonate concentration and base excess. Mixed venous blood was collected serially for the measurement of lactate concentration. Hemodynamically variable resuscitation techniques and pre-arrest hypoxia or hyperoxia did not significantly influence blood-gas values during CPR. Mixed venous lactate concentrations after 20 minutes of CPR were significantly higher when hypoxia preceded the arrest and when intermittent abdominal compression closed chest CPR was used for resuscitation. Mixed venous PCO2 was significantly higher than arterial PCO2 in all dogs during CPR but was not significantly different before arrest.     

Effects of heat stress on the redox status in the oviduct and early embryonic development in mice

This study examined the association between redox status in the oviduct and early embryonic death in heat-stressed mice. In Experiment 1, non-pregnant mice were heat-stressed at 35 C with 60% relative humidity for 12, 24, or 36 h, and the maternal redox status was verified by measuring the levels of reactive oxygen species (ROS) and free radical scavenging activity (FRSA) in the oviduct, and thiobarbituric acid reactive substances (TBARS) and glutathione peroxidase (GSH-Px) activity in the liver. In Experiment 2, zygotes were collected from mice heat-stressed for 12 h on the day of pregnancy, and their developmental abilities were assessed in vitro, along with the intensity of DNA damage at the 2-cell stage. The TBARS value and GSH-Px activity in the liver, and ROS level in the oviduct were significantly higher in heat-stressed mice, and this increase appeared to depend on the duration of the heat stress. Maternal heat stress significantly reduced the percentage of zygotes that developed to the morula and blastocyst and the total cell number in the blastocyst. In addition, DNA damage at the 2-cell stage was significantly higher in maternally heat-stressed embryos. These results suggest that heat stress induces systemic changes in redox status in the maternal body, and the resultant increase in oxidative stress in the oviduct is possibly involved in heat stress-induced early embryonic death .     

Epigallocatechin-3-gallate supplementation can improve antioxidant status in stressed quail

1. Heat stress causes oxidative stress, which decreases plasma antioxidants in poultry. Epigallocatechin gallate (EGCG), the most abundant polyphenol in green tea, is a powerful antioxidant against lipid peroxidation. This experiment was conducted to evaluate the effects of dietary EGCG supplementation on performance, carcase characteristics, concentrations of malondialdehyde, lipid peroxidation indicator, vitamins C, E, A, cholesterol, triglyceride, and glucose in Japanese quail (Coturnix coturnix japonica) exposed to a high ambient temperature of 34 degrees C. 2. One hundred and eighty Japanese quails (10 d old) were assigned at random to 6 treatment groups consisting of 10 replicates of three birds. Birds were kept in cages in a temperature-controlled room at either 22 degrees C (thermo-neutral) or 34 degrees C (heat stress) for 8 h/d. Birds were fed either a basal diet or the diet supplemented with 200 or 400 mg of EGCG/kg of diet. 3. EGCG supplementation linearly increased feed intake, live weight gain, feed efficiency, cold carcase weight and yield under heat stress conditions but did not show the same effect at thermoneutral conditions. Serum vitamin C, E, and A concentrations increased in birds reared at high temperature while non-significant changes occurred in thermo-neutral groups. Malondialdehyde concentrations in serum and liver decreased in all birds of both thermo-neutral and heat stressed groups as dietary EGCG supplementation increased. Heat stress-induced increase in serum cholesterol, triglycerides and glucose concentrations were linearly reversed by EGCG supplementation. 4. The results indicate that EGCG supplementation improved the live performance and antioxidant status of heat-stressed Japanese quail.     

Hepatic concentration of heat shock protein 70 kD (Hsp70) in broilers subjected to different thermal treatments.

1. The relationship between repeated thermal treatments and hepatic synthesis of Hsp 70 was studied in broiler chickens. 2. Sixty broilers were submitted to 5 different treatments (12 birds each) from day 1 to day 42. Four groups were kept in a thermoneutral environment and subjected to 0, 1, 2 and 3 heat stress episodes at 35 degrees C for 4 h per week (TN-0, TN-1, TN-2 and TN-3, respectively). The last group (HT-35) was reared at a room temperature of 35 degrees C. 3. From 39 to 42 old, the birds experienced acute heat stress at 41 degrees C. Resistance to heat stress was evaluated by the time taken for rectal temperature to increase by 3 degrees C above the pre-treatment value. Livers were collected (before and after heat stress) and Hsp70 was determined using Western Blot analysis with monoclonal anti-Hsp70 antibody. 4. Resistance to heat stress and concentration of Hsp70 were higher in those birds subjected to more heat stress episodes during the experimental period (TN-3) and HT-35. A positive correlation was observed between Hsp70 concentration and the time taken for a 3 degrees C increase in rectal temperature (r = 0.42; P<0.01). 5. Exposing birds to episodes of heat stress (35 degrees C) during rearing may improve their resistance to acute heat stress, but the previous thermal history did not seem to influence the hepatocyte Hsp70 content after exposure to more severe heat stress (41 degrees C).     

冷热应激对蛋鸡生理生化指标的影响

１８周龄的伊莎蛋鸡在１３～１８℃、６０％～７０％ＲＨ的环境条件下，饲养至２３周龄（产蛋率为７０％）时，随机分为８组，（每组８只），用于模拟蛋鸡在南京地区自然急性冷热应激条件下的部分生理生化指标变化。试鸡分别在３０℃－７０％ＲＨ、３５℃－７０％ＲＨ、３５℃－９０％ＲＨ和２℃－５５％～７２％ＲＨ条件下进行试验，每种处理均设有一组适宜温度组为对照，试验期均为７天。结果表明，急性热应激时，蛋鸡血液的ＰＣＶ、ＰＣＯ２、ＬＤＨ的活性、血糖、血清钙、Ｔ４、Ｔ３和Ｅ－１７β的含量均与对照组有显著（Ｐ＜００５）或极显著（Ｐ＜００１）降低；直肠温度较对照组有极显著升高（Ｐ＜００１）。急性冷应激时，蛋鸡直肠温度较为恒定，血液ｐＨ、ＰＣＯ２、Ｈｂ、ＰＣＶ、血糖、Ｃｏｒ含量和ＬＤＨ活性略有升高，但除血糖外差异均不显著（Ｐ＞００５），血清钙、Ｔ４、Ｔ３和Ｅ－１７β的含量降低，且Ｔ４和Ｅ－１７β的含量与对照组差异极显著（Ｐ＜００１）。     

复方丁氨丙磷溶液的抗热应激作用及其机理研究

为探讨复方丁氨丙磷溶液的抗热应激作用及作用机理,以黄羽肉鸡为对象,检测各处理组肉鸡生产性能,体温及血清T3、T4、胰岛素和皮质醇等内分泌激素,血清肌酸磷酸激酶、碱性磷酸酶、乳酸脱氢酶和血糖等生化指标.将45只1日龄肉鸡仔鸡随机分成3组,每组15只,分别给予生理盐水和不同剂量的复方丁氨丙磷溶液.于14日龄开始热暴露,在高温条件下继续饲养2周,并观察和检测各项指标.试验结果表明,复方丁氨丙磷溶液能明显降低热应激肉仔鸡直肠温度,显著提高T3/T4值和胰岛素含量,能极显著降低血清肌酸磷酸激酶、碱性磷酸酶和乳酸脱氢酶活性,同时提高血糖含量,而对血清皮质醇含量无显著影响.因此,复方丁氨丙磷溶液可通过调整肉仔鸡血清部分激素含量和改变血清部分生化指标来发挥其抗应激作用.     

Absorption of protein, fatty acids and minerals in young turkeys under heat and cold stress

1. Absorption of protein, fatty acids, calcium, phosphate and potassium by young turkeys maintained at thermoneutral (24 degrees C), hot (35 degrees C) and cold (8 degrees C) conditions was examined. 2. Non-acclimatised, heat-stressed birds absorbed less potassium and phosphate, whereas absorption of nitrogen, fatty acids and calcium was not altered, as compared with birds at 24 degrees C. Non-acclimatised, cold-stressed birds absorbed less calcium than control birds and more nitrogen than non-acclimatised, heat-stressed birds. 3. Heat acclimatization might reduce the adverse effect of heat stress on potassium and phosphate absorption.     

Plasma concentrations of arginine vasotocin and mesotocin following pentobarbital anaesthesia and carotid cannulation in domestic fowl

1. Plasma concentrations of arginine vasotocin (AVT) and mesotocin (MT), arterial pH and pCO2, body temperature, respiratory rate, heart rate, mean arterial blood pressure, packed cell volume and plasma osmolality were monitored in birds for 28 h following anaesthesia and carotid cannulation. 2. Plasma MT concentration decreased after 6 h of surgical recovery but there were no differences between 6 and 28 h of recovery. 3. In contrast, plasma AVT concentration was raised only after 27 h, but no differences were observed between 3 and 28 h of recovery. 4. Anaesthesia and/or carotid cannulation apparently suppressed AVT and enhanced MT release, but no significant change in either hormone was observed after 6 h of surgical recovery under the conditions specified in this study.     

Calculation of the total plasma concentration of nonvolatile weak acids and the effective dissociation constant of nonvolatile buffers in plasma for use in the strong ion approach to acid-base balance in cats

OBJECTIVE: To determine values for the total concentration of nonvolatile weak acids (Atot) and effective dissociation constant of nonvolatile weak acids (Ka) in plasma of cats. SAMPLE POPULATION: Convenience plasma samples of 5 male and 5 female healthy adult cats. PROCEDURE: Cats were sedated, and 20 mL of blood was obtained from the jugular vein. Plasma was tonometered at 37 degrees C to systematically vary PCO2 from 8 to 156 mm Hg, thereby altering plasma pH from 6.90 to 7.97. Plasma pH, PCO2, and concentrations of quantitatively important strong cations (Na+, K+, and Ca2+), strong anions (Cl-, lactate), and buffer ions (total protein, albumin, and phosphate) were determined. Strong ion difference was estimated from the measured strong ion concentrations and nonlinear regression used to calculate Atot and Ka from the measured pH and PCO2 and estimated strong ion difference. RESULTS: Mean (+/- SD) values were as follows: Atot = 24.3 +/- 4.6 mmol/L (equivalent to 0.35 mmol/g of protein or 0.76 mmol/g of albumin); Ka = 0.67 +/- 0.40 x 10(-7); and the negative logarithm (base 10) of Ka (pKa) = 7.17. At 37 degrees C, pH of 7.35, and a partial pressure of CO2 (PCO2) of 30 mm Hg, the calculated venous strong ion difference was 30 mEq/L. CONCLUSIONS AND CLINICAL RELEVANCE: These results indicate that at a plasma pH of 7.35, a 1 mEq/L decrease in strong ion difference will decrease pH by 0.020, a 1 mm Hg decrease in PCO2 will increase plasma pH by 0.011, and a 1 g/dL decrease in albumin concentration will increase plasma pH by 0.093.     

Optimal dietary concentration of vitamin E for alleviating the effect of heat stress on egg production in laying hens.

1. The effects of different dietary concentrations of vitamin E (alpha-tocopherol acetate) were investigated on laying hens exposed to chronic heat stress at 32 degrees C from 26 to 30 weeks of age. 2. Diets containing 5 dietary concentrations of vitamin E (a control diet containing 10 mg alpha-tocopherol/kg or this diet supplemented to contain 125, 250, 375 and 500 mg alpha-tocopherol/kg) were fed to 335 birds. Half of the birds received the supplemented diets for only 4 weeks before the heat stress period (short supplementation duration, SSD) and were fed on the control diet for a further 12 weeks. The remaining birds were fed on the supplemented diets throughout the experiment, 4 weeks before, 4 weeks during and 8 weeks after the heat stress period (long supplementation duration, LSD). 3. Egg production was significantly higher during (80-6 vs 68.9%, P<0.02) and after (75.3 vs 62.7%, P<0.02) the period of stress in the LSD group fed on the diet containing 250 mg vitamin E/kg compared with the group fed on the control diet. LSD birds given 375 and 500 mg vitamin E/kg also had higher egg production than control birds during heat stress but the differences failed to reach significance (74.6 vs 68.9% and 77.1 vs 68.9% respectively). In the SSD groups, mean egg production of the birds given the diets supplemented with 125 mg vitamin E/kg or more was significantly different from the control group after heat stress (70.3 vs 62.7%, P<0.05). Egg weight and food intake were similar in all the groups. 4. Plasma and liver vitamin E concentrations were proportional to the vitamin E intake before the stress period, dropped during heat stress in the SSD groups but were maintained at concentrations closer to those observed before heat stress in the LSD groups. 5. It is concluded that a dietary supplement of 250 mg vitamin E/kg provided before, during and after heat stress is optimum for alleviating, at least in part, the adverse effects of chronic heat stress in laying hens.     

Carbonic anhydrase and its isozymes in heat stressed white Leghorn hens

Experiments were conducted to study the effect of heat stress on uterine tissue carbonic anhydrase levels and their isozyme patterns in relation to production of no- and thin-shelled eggs. Birds exposed to naturally occurring heat stress had lower enzyme levels in their uteri than birds kept in an air-conditioned pen. 4 isozyme bands of carbonic anhydrase were visible in uterine tissue homogenate from both groups of birds. Isozymes were suppressed in heat-stressed birds, as was evident from staining intensities of the bands. This provided evidence to the effect that heat stress not only decreased the total quantity of carbonic anhydrase in the uteri of the hens but also suppressed its isozyme fractions, leading to greater production of no-shell and thin-shelled eggs.     

Partial pressures of oxygen and carbon dioxide, pH, and concentrations of bicarbonate, lactate, and glucose in pleural fluid from horses

Samples of pleural fluid from 20 horses with effusive pleural diseases of various causes were evaluated; samples from 19 horses were used for the study. There were differences for pH (P = 0.001) and partial pressure of oxygen (PO2) between arterial blood and nonseptic pleural fluid (P = 0.0491), but there were no differences for pH, PO2, partial pressure of carbon dioxide (PCO2), and concentrations of bicarbonate (HCO3-), lactate, and glucose between venous blood and nonseptic pleural fluid. Paired comparisons of venous blood and nonseptic pleural fluid from the same horse indicated no differences. There were differences (P = 0.0001, each) for pH, PO2, PCO2, and concentrations of HCO3- between arterial blood and septic pleural fluid. Differences also existed for pH (P = 0.0001), PCO2 (P = 0.0003), and concentrations of HCO3- (P = 0.0001), lactate (P = 0.0051), and glucose (P = 0.0001) between venous blood and septic pleural fluid. Difference was not found for values of PO2 between venous blood and septic pleural fluid, although 4 samples of septic pleural fluid contained virtually no oxygen. Paired comparisons of venous blood and septic pleural fluid from the same horse revealed differences (P less than 0.05) for all values, except those for PO2. These alterations suggested functional and physical compartmentalization that separated septic and healthy tissue. Compartmentalization and microenvironmental factors at the site of infection should be considered when developing therapeutic strategies for horses with septic pleural disease.     

Ascorbic acid and melatonin reduce heat-induced performance inhibition and oxidative stress in Japanese quails

1. The effects of ascorbic acid (L-ascorbic acid) and melatonin supplementation on performance, carcase characteristics, malondialdehyde (MDA) as lipid peroxidation indicator, ascorbic acid, retinol, tocopherol and mineral status in the Japanese quail (Coturnix coturnix japonica) exposed to high ambient temperature were evaluated. 2. Two hundred and forty Japanese quails (10 d old) were randomly assigned to 8 treatment groups consisting of 10 replicates of three birds each. The birds were kept in a temperature-controlled room at 22 degrees C (Thermoneutral, TN groups) or 34 degrees C (for 8 h/d; 09:00 to 17:00 h; Heat stress, HS groups). Birds in both TN and HS were fed either a basal (control) diet or the basal diet supplemented with 250 mg of L-ascorbic acid/kg of diet (Ascorbic acid group), 40 mg of melatonin/kg of diet (Melatonin group) or both (Ascorbic acid + Melatonin group). 3. Supplementing heat-stressed quails with ascorbic acid and melatonin improved performance compared with the control group. Effects generally were greatest in quails supplemented with both ascorbic acid and melatonin. 4. Although supplementation did not consistently restore the concentrations of serum ascorbic acid, retinol and tocopherol to those of TN groups, these concentrations increased significantly with supplementation. Furthermore, serum and liver MDA and serum cholesterol and glucose concentrations were lower in the supplemented groups than in the heat-stressed controls. 5. Within each environment, excretion of Ca, P, Mg, Zn, Fe and Cr were lowest in the combination group and, in all cases, highest in the HS group. Interactions between diet and temperature were detected for live weight gain, cold carcase weight, MDA, ascorbic acid, tocopherol concentrations and excretion of zinc. 6. The results of the study indicate that ascorbic acid and melatonin supplementation attenuate the decline in performance and antioxidant and mineral status caused by heat stress and such supplementation may offer protection against heat-stress-related depression in performance of Japanese quails.     

Impact of heat stress on germinal vesicle breakdown and lipolytic changes during in vitro maturation of bovine oocytes

Two studies were conducted with the overarching goal of determining the extent to which lipolytic changes relate to germinal vesicle breakdown (GVBD) in bovine oocytes matured under thermoneutral or hyperthermic conditions. To this end, cumulus-oocyte complexes underwent in vitro maturation for 0, 2, 4, 6 or 24 h at 38.5 (first study) or 38.5 and 41.0 C (second study; heat stress applied up through first 12 h only, then shifted to 38.5 C). Independent of maturation temperature, triglyceride and phospholipid content decreased markedly by 2 h of in vitro maturation (hIVM; P < 0.0005). Content was lowest at 24 hIVM with no detectable impact of heat stress when exposure occurred during first 12 hIVM. Germinal vesicle breakdown occurred earlier in oocytes experiencing heat stress with effects observed as soon as 4 hIVM (P < 0.0001). Germinal vesicle breakdown was associated with lipolytic changes (R² = 0.2123 and P = 0.0030 for triglyceride content; R² = 0.2243 and P = 0.0026 for phospholipid content). ATP content at 24 hIVM was higher in oocytes experiencing heat stress (P = 0.0082). In summary, GVBD occurs sooner in heat-stressed oocytes. Although marked decreases in triglyceride and phospholipid content were noted as early as 2 hIVM and preceded GVBD, lipolytic changes such as these are not likely serving as an initial driver of GVBD in heat-stressed oocytes because changes occurred similarly in oocytes matured at thermoneutral conditions.     

Post mortem muscle metabolism and meat quality in three genetic types of turkey

1. A standard (FG, fast-growing), a black local or 'label', type (SG, slow-growing) turkey line, and the crossbreed between these two lines were compared for muscle post-mortem metabolism and related meat quality traits. 2. Ninety male turkeys (30 of each genetic type) were raised under the same experimental conditions until slaughter at 16 weeks of age. 3. Live weights at 16 weeks of age differed significantly (7.8, 6.0 and 4.2 kg, for the FG, crossbred and SG lines, respectively). Collagen content of Pectoralis superficialis (PS) muscle was higher in SG birds than in the other two types. 4. The rate of post-mortem glycogen depletion and lactate accumulation in PS and Ilio tibialis (IT) muscles were similar in the 3 lines, as were the rate and extent of post-mortem pH fall in PS muscle. In IT muscle, however, SG birds showed a slight but significantly faster pH decline. 5. Colour measurements indicated a paler breast muscle and a higher degree of myoglobin oxidation in SG birds at 24 h post mortem, than in both other lines. But these differences had disappeared after 4 and 7 d post mortem 6. SG birds showed higher drip loss and instrumentally-assessed toughness in breast muscle, compared with crossbred and FG birds. FG birds, however, had the lowest yield of breast meat after curing-cooking. 7. No marked differences in post-mortem metabolism were found between the three lines. However, differences in water-holding capacity of fresh and cured-cooked meat suggest that factors other than the rate and extent of post-mortem pH fall may contribute to the respective characteristics of these lines.