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2. The responses of birds pretreated as described above to a single injection of corticotrophin (30 IU/kg) were determined.
3. A similar degree of hyperglycaemia had developed in both groups after 2 h but thereafter the responses differed: the concentration of plasma glucose did not increase further in those pretreated with corticotrophin and had begun to decrease at 6 h, whereas that of the birds pretreated with saline increased progressively.
4. The concentrations of plasma corticosterone had increased similarly in the two groups to a peak at 2 h but there was a significantly more rapid decrease in the birds pretreated with corticotrophin.
5. Both groups showed a transient hypercholesteraemia but the increase was significant only in the group that had previously received saline.
6. There were decreases in the concentrations of adrenal cholesterol in both groups. The decrease, in absolute terms, was 2–4 times greater in the group receiving corticotrophin for the first time: percentage changes were similar, however. 相似文献
2. Hyperphagia, amounting to twice the intake of control birds early in the experiment, occurred on the repletion day.
3. Final body weight attained 80% of that of the controls.
4. Body fat concentration decreased at first but returned to that of controls after 3 weeks.
5. A consistent hyperlipaemia was observed after food deprivation or restoration.
6. There was a marked increase in the digestive enzymes found in the small intestine, but not in the pancreas during the repletion day.
7. These responses may be considered as mechanisms to reduce the physiological manifestations of starvation. 相似文献
2. Realised heritability estimates calculated after five generations of selection were : 0–37 + 0.04 for weight gain (WG); 0.44 + 0.05 for food consumption (FC); 0.21 + 0.04 for food conversion ratio (FCR).
3. Realised genetic correlation estimates were: WG and FC, +0.71 ±006; WG and FCR, ‐0.40±0.09; FC and FCR, +0.27 + 0.09.
4. Zero‐generation heritability and genetic correlation estimates were greater than the realised estimates, and sex linkage appeared to be important in the expression of all three traits.
5. The genetic correlation between FC and FCR was asymmetrical with considerable positive response in FCR in line F (rg = +0.79) but negligible response in FC in line E (rg = —0.01).
6. There was an apparent plateau in response in FCR in line E from the third to the fifth selected generations. 相似文献
2. Experiments designed to discriminate between these mechanisms are described: the results indicate the second mechanism.
3. This mechanism offers explanations for various other shell phenomena, including delayed fracture under a static, cyclical or recurrent load.
4. The main implication for the poultry industry is that any external insult to a shell is likely to weaken it by doing damage that is local, internal, irreparable and cumulative, even though it may be invisible from the outside. 相似文献