2. Three‐ to four‐fold increases in blood flow were found in segments surrounding the egg during its passage along the oviduct, possibly due to an enhanced metabolic activity in the muscle layer of the oviduct.
3. Shell‐gland blood flow was minimal in the absence of an egg and increased gradually to a maximum (5‐fold) about 5 h after entrance of the egg into the shell gland. This parallels the rate of calcification of the egg shell.
4. Changes in blood flow in the ovarian follicles and other parts of the oviduct were small while the egg was in the shell gland. This might be typical for the reproductive system of the fowl, which undergoes little structural alteration during egg formation. 相似文献
2. Food consumption and egg production decreased as dietary calcium decreased. Shell weight was unaffected on diets 1 and 2; on diet 3 there was slight reduction of shell weight and on diets 4 to 8 the reduction was marked. The proportion of calcium in the shell was affected particularly on diets 7 and 8, though those from diet 5 also showed a decreased shell calcium.
3. The values for calcium intake and calcium loss in the egg showed that, generally, birds restricted calcium loss to less than intake. Only on the very low concentrations of calcium (diets 6, 7 and 8) did output appear to exceed input.
4. The main mechanism for controlling calcium loss involves the regulation of the number of eggs produced, i.e. the number of ovulations. Alterations in shell quality are of less importance with respect to calcium balance, although shell strength was impaired on the more restrictive diets (5 to 8). 相似文献
2. Plasma T4 concentrations were increased in a dose dependent manner by T4 administration, while triiodothyronine (T3) was decreased.
3. Egg production and percentage of hens in production were transiently decreased in a dose dependent manner by T4 administration, but returned to levels similar to controls within 4 weeks of T4 treatment termination. Moulting was stimulated in a dose‐dependent manner by T4 administration, but was similar to controls after T4 treatment termination. Only dosages of 2 mg/bird/d resulted in cessation of egg production and complete moulting.
4. Results indicate that although short term elevation of plasma T4 causes cessation of egg production and moulting these effects are transient and not indicative of photorefractoriness. 相似文献
2. — The first eggs laid are of low weight and shell porosity but generally by the fifth week of lay both characteristics have increased to the values found in the mature flock.
3. —For mature flocks porosity decreases in the summer and the consequences of this are considered in relation to the observed decrease in hatch‐ability at this time. 相似文献
2. The egg‐shells were colonised by yeasts also, but the growth of these organisms appeared to be dependent upon the pseudomonads for the release of nutrients from the cuticle.
3. The pseudomonads would not grow on cuticle in situ unless the relative humidity was about 100%. 相似文献
2. Lauryl sulphate at 2.5 g/kg or more in the diet significantly increased shell breaking strength, shell thickness and shell weight at 24 and 36 weeks. In 48‐week‐old hens only shell breaking strength was increased significantly. Egg production and egg weight were not affected significantly by lauryl sulphate.
3. Lauryl sulphate might increase these measures of quality by increasing shell deposition and/or shell elasticity. 相似文献
2. Based on a linear mixed model, egg quality was estimated for an average flock at 60 weeks of age and changes in quality traits were predicted until the end of the laying cycle.
3. Egg weight increased by 0.07 g every week from 60 weeks of age onwards and shape index decreased by 0.04 unit weekly (P < 0.001). Haugh unit values decreased weekly by 0.38 units whereas relative yolk weight was unaffected after 60 weeks of age. Relative albumen weight showed a weekly increase of 0.02% and relative shell decreased by 0.02% weekly until the end of lay.
4. Shell quality traits were also influenced by age: shell index decreased by 0.013 g weekly, shell thickness was calculated to be 0.23 µm thinner every week, deformation increased by 0.06 µm weekly from 60 weeks to the end of the laying cycle. Variability of the deformation of eggs indicated more heterogeneous shell quality at the end of the production cycle. Dynamic stiffness increased from 60 weeks of age on.
5. Laying hens were depopulated on average at 80 weeks of age (varying from 74–92 weeks). Although ageing had a significant effect on most of the egg quality traits, egg quality was still acceptable at the end of lay, indicating the potential to extend the laying cycle. 相似文献
2. It was fed at 16 weeks of age to five separate groups (groups 2 to 6) each of 50 to 60 birds.
3. Group 2 was fed on a normal layers’ diet at 23 weeks of age, group 3 at 27 weeks, group 4 at 31 weeks, group 5 at 35 weeks and group 6 at 55 weeks while the control group (group 1) of similar size to groups 2 to 6 was subjected to a normal commercial treatment for laying stock.
4. In all the experimental groups the onset of sexual maturity occurred normally, but only one or two eggs were laid before laying ceased under the influence of the treatment.
5. Laying re‐started when the hens were fed on a normal diet and production rapidly rose to a high level.
6. Groups 1, 2 and 3 differed little in the total number of eggs produced up to 72 weeks of age.
7. In all experimental groups there were fewer very small, small and medium eggs than in the control group.
8. It is suggested that the use of a low‐calcium diet before the onset of lay may have advantages which could be exploited on a commercial scale. 相似文献
2. Egg weight and shell quality characteristics were recorded for the eggs and the cuticle was then removed from one egg of each pair.
3. Egg weight and shell quality were re‐assessed for the eggs from which the cuticle had been removed.
4. The cuticle made a significant (P<0.01) contribution to shell thickness and removal of it appeared to reduce shell strength when measured directly, but the method of measurement was too variable to establish this with statistical significance. 相似文献
2. Four different rearing treatments with a subsequent constant 16‐h photoperiod during laying were used.
3. A 15‐h rearing photoperiod resulted in delayed sexual maturity, increased mature body weight and decreases in both total egg numbers and the proportion of smaller eggs, compared with a 6‐h photoperiod.
4. Continuous light to 56 d, although associated with a high incidence of subsequent blindness, resulted in satisfactory egg production.
5. Abrupt reduction in the photoperiod from 15 to 6 h for the 112 to 167 d period resulted in unsatisfactory subsequent performance, especially when the day‐length was only slowly increased to 16 h during laying.
6. In the two laying treatments, in which the photoperiod was increased gradually from 6 to 16 h during the 168 to 238‐d period, a decrease in the number of smaller eggs occurred, compared with the treatments in which a single abrupt increase in photoperiod was used. 相似文献
2. The dietary treatments had no significant effect upon food intake, egg output, shell thickness, shell deformation or specific gravity of the eggs.
3. The 28‐h cycle reduced mean rate of lay by 4.5%, increased egg weight by 5.8% and increased shell thickness by 9.4%. The proportion of eggs with shell faults revealed on candling was reduced from 4.1 % to 2.8%.
4. It is concluded from this and other sources that decreasing dietary phosphorus or modifying vitamin D supplements may sometimes lead to increases in shell thickness of the order of 1 to 2%, but that these changes are unlikely to result in a measurable reduction in the proportion of cracked eggs late in the laying year.
5. A 28‐h light‐dark cycle results in a longer and more uniform interval between consecutive ovipositions and thus gives reliable increases in shell thickness which are large enough to reduce the proportion of cracked eggs in many practical situations. Whether it is profitable to use an ahemeral cycle will depend upon the relative prices paid for eggs of different sizes. 相似文献
2. Treatment with acetazolamide decreased the rate of shell formation by 44%; reduced the concentrations of water and Na+ in the albumen at the beginning of the plumping stage but increased the accumulation of water during plumping; increased the concentration of Cl‐ in the albumen after the 6‐h stage without any appreciable change in K+ and Ca2+ concentrations.
3. The computed relationships between the concentrations of different ions also showed that the transfer of water and Na+ were linked during egg formation, that a water‐independent, acetazolamide‐sensitive reabsorption of Na+ occurred after the 10‐h stage and that Na+ and Cl‐moved simultaneously up to 14 h but with the ratio of Cl‐ to Na+ three times higher in the treated group.
4. It is concluded that acetazolamide impairs the transfer of Na+ and Cl‐ between the albumen and the extracellular fluid and that secretion of Ca2+ into the uterine lumen seems to depend on Na+ and Cl‐ reabsorption. 相似文献
2. Contraction of warm eggs in ice‐cold colloidal iron caused flooding of pore canals and contamination of the underlying shell membranes with this element.
3. Appreciable contamination of the inner shell membrane with iron persisted for 25 d in infertile eggs stored at 37.5 °C. 相似文献
2. Eighty‐four point six, 69.5 and 31.4% respectively of the food consumed by the birds which received the high‐protein concentrate, protein concentrate or grower diet with wheat consisted of the whole cereal. The corresponding figures for the birds which received barley were 73.9, 41.3 and 10.9% respectively.
3. There were no significant differences in rate of food intake or growth between choice‐fed birds receiving whole wheat and the complete diet‐fed birds with no choice. 相似文献
2. Food consumption up to 20 weeks of age was significantly reduced by all three treatments; mortality was increased and sexual maturity was delayed.
3. Greatest uniformity was observed amongst pullets fed on the low protein and the low lysine diets
4. By 70 weeks there were no significant differences in food conversion based on food consumed between 20 and 70 weeks of age, but based on consumption between 8 and 70 weeks the quantitatively restricted birds converted food most efficiently.
5. The most favourable method of restriction appeared to be the feeding of a low lysine or low protein diet, since rearing costs were low, and the performance of the pullets on these treatments was high. 相似文献
2. In hens receiving a normal diet containing a calcium supplement in a powdery form Pi increased from 25 to 42 mg/1 during an entire shell formation cycle (from 10 to 22 h after oviposition of the previous egg), while in cockerels Pi decreased slightly during the night.
3. This increase in Pi in hens, was not related to cessation of feeding at the onset of darkness but was specifically connected with the beginning of shell secretion.
4. When hens received calcium as crushed sea‐shells separately from the diet, the nocturnal peak in Pi virtually disappeared and only a temporary increase of 4 mg/1 between 10 and 14 h after oviposition remained.
5. These results indicate that the beginning of shell secretion is always accompanied by an increase in Pi and that a separate presentation of dietary calcium reduces the bone mobilisation at night. 相似文献
The results indicate that with certain breeds the dietary protein levels can be lowered to approximately 16% during the o to 8‐week period and to approximately 12% during the 8 to 20‐week period without adversely affecting egg production. However, variations in the laying performance of the different breeds appear to be dependent on the amount of protein fed in the first eight weeks of life. Significant breed effects were observed throughout the experiment and although restricted feeding during the laying period substantially reduced the food intake it also had a detrimental effect on the rate of egg production and on the total weight of eggs produced. 相似文献
2. Dietary Pt had no significant effect on production measures in any experiment. Increases in dietary Pt adversely influenced egg shell quality although uterine calcium (Ca), ATPase and carbonic anhydrase activities were unaffected.
3. A 3‐d‐feeding trial in experiment 1 gave maximum Pt retentions of 228 mg/d at 18°C and 204 mg/d at 30°C. These were obtained with diets containing, respectively, 4.6 and 6.0 g Pt/kg.
4. Plasma inorganic P (Pi) increased consistently with increases in dietary Pt at all temperatures but plasma total Ca, and tibia Ca and P, were unaffected.
5. The inclusion of the phytase supplement in diets containing 3.2 and 4.6 g Pt/kg had an adverse effect on egg production at both temperatures in experiment 2.
6. A dietary Pt concentration of 3.2 g/kg, providing a calculated 1.2 g available P (Pav) /kg, with a dietary phytase activity of less than 200 units/kg, satisfied the P requirements of the hens used in these studies. However, the data from experiment 3 suggest that the Pt requirement of some flocks fed on wheat‐based diets may be lower than 3.2 g/kg. 相似文献
2. In contrast with normal eggs, the surface of the cuticle‐less shell was irregularly contoured and, in many instances, deeply fissured. 相似文献