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2. We carried out post‐mortem examinations on 111 embryos that died within this period to assess the causes of this mortality.
3. Malpositioning and severe oedema were the predominant symptoms of dead‐in‐shell embryos with 55% being malpositioned and 41% showing severe oedema. Of these, 22 embryos (24%) showed both symptoms. Malpositioning generally results from incorrect setting of the eggs or inadequate turning and oedema was significantly correlated with the amount of water lost from the eggs which in turn was correlated with egg size.
4. Myopathy, gross lesions of internal organs, haemorrhage, bacterial infections and congenital deformities were found in less than 10% of chicks examined for these symptoms. 相似文献
2. Twenty‐one 2‐week‐old chicks were used to determine fat digestibilities and AMEn values of diets, using the total collection method. Fats were included in a wheat‐soyabean meal diet at 100 g/kg. Multiple linear regression analysis was used to express the ME values of fats as functions of the parameters measured (moisture, gross energy, impurities, unsaponifiables, non eluted material, free fatty acid content, unsaturated: saturated ratio, peroxide value, TBA test).
3. The ME of the fat products lay in the range 12.62 to 24.35 MJ/kg, and 29.26 MJ/kg for refined sunflower oil. Free fatty acid content of the fats was shown to be a poor predictor of their ME values, whereas non eluted material (NEM) of the fat products showed a good correlation with their ME. A regression equation could be derived (R2 = 0.6548; SEE = 2–0064) with the unsaturated: saturated ratio (U:S) and NEM. An ME prediction equation based on the U:S, NEM and unsaponifiable content is also proposed (R2 = 0–7168; SEE= 1.9058). 相似文献
Avian Hematology and Cytology. Terry W. Campbell. 1995. 104 pp. Illustrated. £48.00. Ames, Iowa State University Press. ISBN 0 8138 2970 4. 相似文献
2. We investigated the relationships between a hen's prelaying behaviour and its tendency to lay on the floor by recording the behaviour of 20 hens housed individually in wire cages with single littered nest boxes.
3. Most floor eggs (80%) were laid by the same 6 hens. These 6 “floor‐layers” performed more nest seeking behaviour, less nest‐building behaviour and less sitting prior to oviposition than the 14 hens that consistently laid in nest boxes.
4. The incidence of floor eggs declined with age. Both nest and floor laying hens performed less nest seeking behaviour with age. Floor layers, however, increased their performance of nesting behaviour, whilst nest layers performed less nesting behaviour with age.
5. Floor laying hens behaved as if they found the nest box less attractive than nest‐laying hens; perhaps because they had lower nesting motivation, or perhaps because their nesting motivation was as high, but they less readily perceived the nest box as an appropriate nest site. 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. Birds kept at the cool temperatures throughout life ate most food and gave the best production during lay. Minimum food intake and poorest performance were obtained with birds kept at the hot temperatures throughout life.
3. Performance in the hot environment during lay was improved by rearing birds in the cool environment, the response being related to an increased food intake. Food intake in the cool environment during lay was reduced, with only minor effects on performance, in birds which had been reared in the hot environment.
4. The results of the present study show that production responses during lay are affected by the temperatures experienced by hens during both growth and lay. 相似文献
2. Agricultural research is defined as work intended to benefit agriculture and directed towards those problems which seem capable of solution. Science research is something else. Too much of the money allocated for agricultural and biotechnology research is being spent on science research. The system of rewarding agricultural scientists needs to be adjusted away from counting papers published.
3. Some examples are given of problems in poultry science which seem likely to be soluble by gene manipulation. These include “essential” amino acid synthesis within the chicken, improvement of shell strength, the prevention of many diseases, but probably not the improvement of quantitative traits or of behavioural adaptation to intensive husbandry.
4. Examples are also given of problems likely to require empirical solutions, such as the benefits of acclimatisation or the long‐term response to a lighting programme. Here the need is to develop better theories to guide modelling activities.
5. The author concludes that there is much research that can and should be done in poultry science in the next 20 years but calls for a recognition that some problems cannot be solved by a “fundamental” approach but will need experiments with whole animals coupled with model‐building activities. 相似文献