2. The rate of increase in deep‐body (rectal) temperature during exposure to 32°C was used as the index of thermoregulatory ability. Comb and foot surface temperatures were measured as indicators of peripheral vasomotor tone.
3. Because body temperature control depends on the balance between heat production and heat loss, heat production was measured to determine whether fat line hens had a higher heat production, which they would then have to dissipate.
4. During the first hour of heat exposure, rectal temperature in the ad libitum‐fed birds increased twice as rapidly as in the corresponding lean line sample and 6 times more rapidly than in the control‐fed fat‐line group.
5. Surface temperatures of comb and foot increased from 27°C to 37°C within the first hour at 32°C, with no effect of either genotype or feeding regimen on rate of increase.
6. Heat production was unrelated to genotype but was reduced by 23% by controlled feeding, largely because of the reduction in body weight.
7. The results demonstrated that ad libitum‐fed fat‐line birds are susceptible to heat stress and that this is related not to increased heat production, but to a decreased ability to lose heat. Elevation of blood viscosity by plasma triglycerides is suggested as a causal factor. 相似文献
2. Carcase nitrogen was higher in males than in females, and in birds reared at LT than in those reared at HT.
3. Birds at LT and on HE diet, regardless of sex, retained more energy as fat in their carcases than those at HT and on LE diet respectively.
4. Maintenance energy requirement averaged 6.70, 7.67, 7.43 and 9.01 kJ per g metabolic body size (kJ/gW 0.66) for broilers at HT and LT up to 34 d and at HT and LT up to 54 d, respectively.
5. There was a similar increase with age in the energy requirement for growth but with requirements of broilers at LT consistently lower than for those at HT. 相似文献
2. Birds in all treatments gained similar amounts of weight from 12–14 weeks of age. Thereafter, birds in C maintained gains, the body weight gains of birds in EC and EH declined moderately and birds in H lost weight.
3. Birds in C produced more metabolic heat. Those in H showed increased heat production as they became older.
4. Protein retention was greater in turkeys in C, EC and EH. It was lower in H, becoming negative between 18–20 weeks of age. Birds in H suffered body fat losses which increased with age.
5. Birds in EH and EC gained similar amounts of body weight. Birds in EH exhibited lower heat production and greater energy retention than those in EC.
6. Body temperatures were higher in H than in the other environments. 相似文献
2. At 22°C, weight gain of LL broilers was the same as in FL chickens, but at the high temperature LL birds grew to a greater weight than FL ones.
3. Food conversion efficiency was not affected by ambient temperature in LL chickens but was depressed in FL ones at 32°C.
4. Increasing dietary protein content did not alleviate heat‐induced growth depression irrespective of the genotype.
5. Gross protein efficiency was higher in LL chickens and was less depressed at 32°C than in FL birds.
6. Fat deposition decreased with increasing protein concentration at normal temperature in both genotypes; at high temperature, high protein content enhanced fatness, particularly in LL chickens.
7. Thus, genetically lean broilers demonstrated a greater resistance to hot conditions: this was indicated by enhanced weight gain and improved food and protein conversion efficiencies. 相似文献
2. Oiling slowed the decline in albumen height (Haugh units) to that which occurred in unoiled eggs stored at 12 °C.
3. Oiling slowed the increase in albumen pH equally at 28 and 12 °C.
4. Oiling markedly decreased the weight loss of eggs stored at either temperature.
5. Oiling and temperature of storage were without effect on the whipping volumes of either albumen or unseparated albumen and yolk. 相似文献
2. Mean temperature in the immediate environment of the chicks was 2.0°C lower than the setpoint of 1 d of age. During the first week this initial temperature difference gradually rose to 1.7°C above setpoint. At 18 d of age a further rise to a mean difference of 4.0°C above setpoint was measured. The difference then remained constant from 32 d of age until the end of the fattening period.
3. It was concluded that the chickens were actually brooded at 30°C. During the rearing period the ambient temperature in the close vicinity of the broilers gradually declined to 26°C.
4. During the finishing period, ambient temperature around the broilers was far above the value recommended for optimal food intake and growth.
5. These results are discussed in relation to heat generation and heat fluxes in the broiler houses. 相似文献
2. There were negligible differences in preference between the experimental and reference grilled breast meats.
3. Odour preference differences for thawed, uncooked birds were significant after 1 month of storage at ‐ 12 °C and after 9 months at ‐ 18 °G.
4. In comparison with the reference birds the redness of frozen and thawed birds decreased more regularly during storage at ‐ 12°C than at ‐18 °C.
5. Packaging the birds in Cryovac instead of in polythene resulted, in the raw birds, in a greater difference in surface redness. This redness decreased more rapidly during storage than that of birds packaged in polythene. 相似文献
2. Heat exposure of laying fowl resulted in a 1.1°C rise in body temperature, a 10‐fold increase in respiration frequency and mild hypocapnia and hypoxaemia.
3. Plasma and follicular tissue TG concentrations were not significandy affected by heat exposure, but plasma TG specific radioactivity decreased significantly and was negatively correlated with body temperature.
4. The transfer rate of TG to the preovulatory follicles was not affected significantly by hyperthermia.
5. We conclude that nutrient supply to the developing follicles is not compromised in acutely heat‐exposed laying fowl. 相似文献
2. In the first experiment, colostomy had no significant effect on mineral balance. However, broilers exposed to high cycling ambient temperature reduced their retention of phosphorus, potassium, sodium, magnesium, sulphur, manganese, copper and zinc compared with birds housed at 24°C.
3. Despite the minimal effect of high ambient temperature on urine production, minerals excreted disproportionately excreted in urine included potassium, magnesium, phosphorus and sulphur while copper and magnesium were lost primarily via the faeces.
4. In the second experiment, exposure to 35°C increased urine output from 50.7 ml/12 h per kg of body weight at 24°C to 101.3 ml/12 h per kg of body weight and was associated with an increased urine:water ratio and reduced urine osmolal‐ity.
5. Reduced urinary chloride and higher potassium, phosphorus, sulphur, sodium, magnesium, calcium and manganese excretion was observed for broilers housed in under high ambient temperatures compared to 24°C.
6. These studies suggest that high ambient temperatures adversely influence mineral metabolism and, furthermore, that the route of excretion varies with the specific mineral and the environmental temperature exposure. 相似文献
2. Storage of uneviscerated Wrolstad turkeys at 4 °C for 10 days caused no statistically significant changes in meat flavour or texture.
3. During further storage at —2 °C, however, there was a slight but significant change in flavour, which became more marked with time in birds which had been eviscerated after the initial period at 4 °C.
4. Both eviscerated and uneviscerated birds became slightly tougher during storage.
5. Initial holding at 4 °C increased the numbers of psychrotrophic bacteria on the skin by about 103 but subsequent changes at — 2 °C were slight for uneviscerated birds.
6. Eviscerated carcases had higher counts than uneviscerated birds after storage at — 2 °C and, although ‘off’ odours were not detected, spoilage appeared to be imminent at the end of the 20‐d period. 相似文献
2. Higher rates of fertility and hatchability of Japanese quail eggs were observed from parents of 10 to 19 weeks of age, with peak fertility and hatchability at 14 and 12 weeks of age, respectively.
3. Sex ratios of 1:2 to 1:5 gave comparable fertility and hatchability results.
4. The hatching performance of quail eggs from cage and deep litter reared breeders was comparable.
5. Fertility and hatchability were directly proportional to the egg weight.
6. Quail egg shell colour, tints and blotches were found to influence hatching performance.
7. Storing quail eggs at 16 ± 2°C and 75 ± 5% relative humidity for more than 4 d reduced hatchability.
8. Hatchability of eggs stored at room temperature was improved if they were sealed in polyethylene bags.
9. Provision of light during the first 14 d of incubation resulted in a photo‐acceleration of about 3.2 h. 相似文献
2. Selection for increased growth was practised for two generations using ten females and five males as parents in each line.
3. A significant interaction between time and temperature was observed in the third generation progeny; when exposed to heat stress, the stress‐adapted lines showing a superior growth rate.
4. A sex × temperature interaction was also observed and was due largely to the control females being more sensitive to stress than the males.
5. A cumulative realised heritability estimate of 0.47 ± 0.15 for 5‐week body weight was obtained. 相似文献
2. The quail were kept in open‐circuit respiration calorimeters, so that diet selection could be related to energy requirement.
3. Increasing ambient temperature had no significant effect on food intake by weight, but the proportion of the high energy choice decreased and, conversely, the proportion of the lower‐energy but higher‐protein choice increased.
4. Energy intake was therefore negatively correlated with ambient temperature, but protein intake per unit of energy intake increased, allowing the birds to gain weight at about the same rate at all temperatures.
5. Heat production decreased as ambient temperature increased. Respiratory quotient decreased with increasing temperature, which indicates a reduced utilisation of carbohydrate as an energy source.
6. Water intake increased with temperature but there were no overt signs of heat stress and there was no significant change in body temperature.
7. Japanese quail selected a dietary mixture which maintained similar growth rates over a wide range of ambient temperature, by sustaining protein intake but altering energy intake in line with thermoregulatory energy demands. 相似文献
2. At an energy retention of 179 kJ/kg W 0·75 d, only protein was retained. At higher energy intakes, each increment in retention had a rather constant composition: about 85% energy in fat and 15% in protein. At lower energy intakes body fat was mobilised whereas protein was deposited.
3. The efficiencies of energy retention in protein and fat were estimated to be 0·66 and 0·86 respectively.
4. The rather constant composition of additional retained energy after additional energy supply provides an explanation for a linear relationship between energy intake and energy retention. 相似文献
2. In only one experiment was weight gain significantly improved when the barley was heated.
3. Autoclaving barley at 120 °C for 30 min reduced dietary dry matter digestibility and treating the barley with dilute acid before heating had no effect on its nutritive value.
4. Supplementing diets containing commercial barley with a‐amylase produced slightly conflicting results in that there was an improved weight gain, food conversion efficiency and digestibility value in two of three experiments.
5. The digestibility and metabolisable energy values of a North American six‐row spring barley (Glacier) were significantly improved by enzyme supplementation.
6. The effect of the enzyme on diets containing a high amylose barley (Glacier Pentlandfield) was positive but not significant. 相似文献
2. Legs cut from the whole birds after removal from store, unpacking and thawing, and legs from the portions were compared in odour preference at four times of examination.
3. After only 1 d the odour of the legs stored as parts at —12 °C was less preferred than that of the reference group; this was also true for legs cut from whole birds after 3 months at the same temperature.
4. After 3 months at — 12 °C the odour of the legs stored as parts was less preferred than the odour of legs obtained from whole birds.
5. Storage of legs as parts at —18 °C resulted in a comparatively less preferred odour after 3 months, while the same was true after 9 months for legs cut from the carcasses. 相似文献
2. The birds, which had been subjected to exposure to 38°C for 24 h at 5‐d‐old, served as prior exposure group (group A). Both group A and control group B were exposed to 33°C for 3 h when near marketable weight.
3. On exposure to 33°G, ahhough there were no significant differences in the increases in heat production (HP) between the two groups, abdominal temperature (Ta), temperature of external ear tract (Tee), shank skin temperature (Tss), standing‐lying frequency and lying time were lower in group A than in group B. Heart rate (HR) and comb surface temperature (Tcs) did not differ but increased in both groups during exposure to 33°C. Respiration rate (RR) was greater in group A.
4. Blood viscosity decreased markedly in both groups after exposure to 33°C; the decrease was greater in group A.
5. These results suggest that early exposure may promote broilers' ability to cope with the subsequent heat load by altering diermoregulatory physiological responses and behavioural patterns, resulting in an alleviation of heat stress. 相似文献
2. Heat stressed fowl showed a significant hyperthermia (+ 1.3°C), rapid shallow breathing (229 breaths/min) and significant hypocapnia ( ? 8 Torr).
3. Significant increases in absolute blood flow (ml/g per min) were measured in the kidneys, spleen, liver and duodenum during hyperthermia, but there was no change in the absolute blood flow to the reproductive tract or the relative perfusion of the reproductive tract compared with the other tissues sampled.
4. We conclude that in these acute conditions of heat exposure, blood flow to the reproductive tract of the laying fowl is not compromised by any simultaneous thermoregulatory needs. 相似文献
2. Eggs incubated at 36.5°C hatched later than eggs incubated at 37.5°C but did not differ in age of mortality or incidence of malpositions and abnormalities.
3. Eggs incubated at 38.5°C hatched significantly less well than eggs incubated at 37.5°C and showed significant differences in time of embryo mortality. Overheated embryos had a mortality peak between 15 and 20 d of incubation and an increased mortality after 24 d of incubation.
4. Overheated eggs were characterised by a high incidence of embryos with head in small end, with excess albumen, ruptured yolk sacs, oedematous heads, eye cataracts and swollen down‐plumules. 相似文献
2. Myofibrils were prepared from 0.1 M and 0.2 M lactic acid marinated muscle and control (non‐marinated samples) sampled at 0, 1, 3, 7 and 14 d post mortem.
3. Changes in myofibril fragmentation index (MFI), myofibrillar proteins and Z‐line structure were examined.
4. Marination of duck breast muscle in lactic acid at 5°C enhanced fragmentation of myofibrils and degradation of myofibrillar proteins and Z‐line structure as compared to control samples.
5. In summary, lactic acid marination at 5°C can accelerate the post mortem degradation of myofibrils in Tsaiya duck breast muscle. 相似文献