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2. A tryptophan‐limiting protein mixture was used and by dilution seven dietary protein contents were produced, supplying from 0.84 to 1–92 g tryptophan/kg diet. The diet of lowest protein content was also sup‐lemented with free tryptophan. These diets were fed in experiments using 24 groups of 72 pullets at 63 to 73 weeks and 45 groups of 21 hens at 97 to 106 weeks.
3. The relationship between egg output and tryptophan intake was the same in moulted hens as in young pullets, but pullets of 63 to 73 weeks of age yielded a different response curve; more tryptophan being needed for a given egg output.
4. It is concluded that tryptophan required, per day, does not decrease during the first laying year, despite a decrease in rate of egg output. 相似文献
2. A requirement of approximately 775 to 800 mg sulphur amino acids /hen d, of which about 390 to 440 mg was methionine, was found for a maximum of 80 to 83 eggs/100 hen d. There were indications that the requirement for maximum egg production was less than that for maximum efficiency of food utilisation.
3. Diets containing 138 g protein/kg supplemented with methionine and lysine supported production and food utilisation as effectively as a diet containing 167 g protein/kg. 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. The stabilities of carcass fat and meat of 9‐week‐old broilers fed on diets containing ASS with 300 mg ethoxyquin (EQ)/kg or diets containing tallow with 20 mg ATA/kg from weeks 5 to 9 were comparable with those obtained by feeding these antioxidants and fats throughout the growth period.
3. ATA added to a diet containing ASS, and EQ, added to a diet containing tallow did not improve meat stability despite such an effect on adipose tissue when fed for 9 weeks. The results emphasise the importance of using the dietary antioxidant appropriate to the fat supplement to improve carcass stability. 相似文献
2. An hypothesis put forward to account for these effects states that Effective Photoperiod equals p + c – b, where p = actual photoperiod, c = cycle length and b = the period of the endogenous biological clock.
3. Two experiments designed to test this hypothesis have yielded results which are consistent with it.
4. A poultryman who uses an ahemeral cycle to alter egg weight or shell thickness and then wishes to transfer his flock back to a 24‐h cycle should calculate the difference between the two cycle lengths and then add this quantity to the prevailing photoperiod to find the appropriate amount of light to be used in the 24‐h cycle. 相似文献
2. Sulphanilamide appeared to act mainly by reducing the rate of shell deposition, time spent in the shell gland was unaffected.
3. The thickness of shell components was reduced in a roughly proportional manner in thin shells produced during sulphanilamide treatment.
4. It is proposed that other thin shells in which the component layers are all reduced to a similar extent are also the result of a decreased deposition rate. 相似文献
2. The following variance components were obtained: σ2(pen) = 255 g2, σ2(sire) = 1 260 g2, σ2(sire × hatch) = 1 997 g2,σ2(residual) = 19 708 g2.
3. It is concluded that the effectiveness of progeny testing for growth rate in broilers is severely restricted by sire x hatch interaction effects. 相似文献
2. The difference between the NPU values, 0.66 for yeast and 0.80 for the soyabean meal and fish meal mixture, could largely be attributed to the high nucleic acid content of the yeast.
3. Chicks given the diet containing yeast (190 g/kg) did not grow as rapidly as those given the soyabean meal and fish meal reference diet, and the reduced growth could only partly be explained by a marginal deficiency of methionine.
4. Food conversion efficiency with the yeast diet was improved by maize oil while responses to α‐tocopheryl acetate and sodium selenite were inconsistent.
5. Chicks grew well when yeast replaced fish meal in the mixture of soyabean meal and fish meal, and when fish meal (194 g/kg diet) was the sole protein supplement. 相似文献
2. The shells of such eggs were thinner than those of intact eggs in seven of the populations.
3. The number of defective eggs, the specific gravity of the eggs, and the percentage hen‐day egg production of normal eggs were significantly correlated within populations with the incidence of broken eggs.
4. No significant correlations were found within populations between the incidence of egg breakage and either egg weight, body weight, or shank length. 相似文献