Only the growing ration containing 1.83 per cent magnesium significantly reduced growth, percentage bone ash and food utilisation during the growing phase (9–20 weeks). In the laying phase (20–40 weeks) significantly greater gains in body weight and percentage bone ash were produced by the birds which had received the growing ration containing 1.83 per cent magnesium.
The magnesium content of the growing rations had no effect on rate of lay, egg weight or egg shell thickness.
Hens fed the laying ration containing 1.96 per cent magnesium gained less body weight, laid fewer and lighter eggs and utilised their food less efficiently than those fed other levels of magnesium.
Egg production and food required per dozen eggs were poorer with the ration containing 1.20 per cent magnesium, but were not statistically different from the rations containing 0.48 or 0.70 per cent magnesium.
Eggs with thinner shells were produced by hens fed the 1.96 per cent magnesium ration at 34 weeks of age than were produced by those fed the 0.48 or 0.70 per cent magnesium rations. 相似文献
In the first experiment a basal soyabean meal diet (14.3 per cent crude protein) was supplemented with L‐lysine and DL‐methionine, singly and together. Supplementation of the basal soyabean diet with the amino acids caused no significant effects on egg production, mean and total egg weight or food conversion efficiency. None of the soyabean diets proved as satisfactory for egg production or food conversion efficiency as a fish meal control diet (16.9 per cent crude protein).
In the second experiment the effect of adding 0.1 per cent each of L‐lysine and DL‐methionine or 0.2 per cent each of l‐lysine and DL‐methionine to a low fish meal diet (2.5 per cent fish meal) was examined. The addition of 0.2 per cent of each amino acid caused an increase in egg production.
Mean egg weight was improved by the addition of amino acids at both levels although this effect was not statistically significant. Comparison of the low fish meal diets with a fishmeal control diet (10 per cent fishmeal) showed that at the 0.2 per cent addition of amino acids, egg production, total egg weight and food conversion efficiency were better than on the 10 per cent fish meal control diet.
Two breeds, light and medium hybrids were used in both experiments.
The results are discussed with reference to their practical significance. 相似文献
2. Growth and food conversion efficiencies were optimised with supplements of 1.5 mg folic acid/kg added to basal mash starter diets. The dietary folic acid requirement of broilers was estimated to be in the range of 1.7 to 2.0 mg/kg.
3. Red blood cell phosphoribosylpyrophosphate concentrations and dihydrofolate reductase activites did not show consistent changes over the range of dietary folate concentrations studied but plasma folate concentrations responded markedly to dietary folate supplementation.
4. Adding choline to diets in amounts greater than the normal requirement did not spare the requirement for folic acid.
5. It is suggested that minimum folic acid supplements for pelleted practical diets should be in the order of 2.5 to 3 mg/kg. 相似文献
Apart from a possible beneficial effect during the first few weeks of production, little increase in egg weight occurs when birds are fed on conventional rearing diets and then fed on laying diets containing linoleic acid in excess of requirement.
After depletion of linoleate reserves, dietary supplementation with linoleic acid significantly increases egg weight at any age.
The necessity of supplementing diets for laying hens with linoleic acid is discussed. 相似文献
Excess lysine induced a marked depression in growth within 48 h. Towards the end of the experiment, the chicks lost weight and showed no signs of adaptation to the excess dose of lysine. The plasma concentration of arginine fell within 24 h of feeding excess lysine but the reduction in food intake did not occur until 6 d of the experiment had elapsed. Excess leucine similarly caused a rapid retardation of growth which was followed subsequently by a depression in food intake. Mixtures of amino acids lacking in leucine, isoleucine and valine also induced marked growth inhibitions the severity of which were enhanced by the inclusion of leucine and isoleucine in the mixtures. Growth tended to be adaptive in chicks fed on the incomplete amino acid mixtures but non‐adaptive in those fed on excess leucine.
Pair‐feeding studies indicated that appreciable differences in weight gain still occurred when food intake was equated between control groups and groups receiving excess lysine or leucine.
The results of the present study indicate that the depression in food intake cannot account completely for the ill‐effects of excess lysine and leucine. They also suggest that the adverse effects of lysine and leucine are distinct from those caused by incomplete mixtures of amino acids. 相似文献
2. The inclusion of AA improved egg production, food intake and efficiency of utilisation, and decreased the cost of food per kg egg. The addition of 400 mg AA/kg diet gave the most efficient performance.
3. Palm oil inclusion reduced the effect of heat stress and increased egg production, egg weight, food intake and efficiency of utilisation.
4. When 200 mg AA and 50 g palm oil/kg were used, additive responses were obtained with further improvements in egg production, food cost and efficiency.
5. Ascorbic acid and palm oil when fed alone or in combination reduced the incidence of cracked eggs.
6. Thus, 400 mg ascorbic acid/kg of diet, 50 g palm oil or 200 mg AA plus 50 g palm oil/kg diet ameliorated the effects of heat stress in laying hens. 相似文献
2. An Individual Poultry Weighing System (IPWS) was developed to record time, duration, location and body weight of visits of individual hens to 4 weighing scales.
3. The number of hens that visited the weighing scales per 3 h period varied from less than 10 during the dark‐period to more than 60 during the light‐period.
4. The average number of visits per individual hen was 1–4 and the average number of successful weighings per hen was 0–6 during the light‐period.
5. Body weight showed a diurnal rhythm: the difference between the maximum body weight at night and the minimum body weight in the morning was 63 g.
6. The location of the scales influenced number of visits, number of weighings, mean body weight, flock‐uniformity and duration of visits.
7. Body weight per 3 h period did not differ between hens which were individually recognised and those which were not.
8. Flock‐uniformity was 2–6% higher during the light‐period if it was based on weighings of identified hen visits.
9. The average duration of the visits to the scales in the middle of the feeding tier during the light‐period was 63 s.
10. Of all the hens that visited the scales during a 24 h period, 54% visited them only once.
11. Automatic weighing systems without individual hen recognition can deliver reliable management information on mean body weight and flock‐uniformity in aviary systems if the weighing scales are located on the feeding tier in the middle of the house and if they are used during the light‐period. 相似文献
2. Groundnut meal, groundnut meal adjusted with indispensable amino acids or sesame meal supplied the dietary CP at 180 g/kg diet. Increments of lysine (1.5 g/kg diet) were added to each of these diets.
3. The gain, food intake and food efficiency responses of broiler chicks were analysed using a quadratic equation and a two‐slope method. An estimate of lysine requirements was also obtained from a survey of college students.
4. The different methods produced widely different estimates of lysine requirement.
5. The average lysine requirement was estimated at 50.1 g lysine/kg CP for groundnut meal, 61.7 for adjusted groundnut meal and 54.9 for sesame meal.
6. Reasons for the effect of statistical analysis and protein source on lysine requirement are discussed. 相似文献
2. More eggs were produced per hen housed from 30 to 70 weeks in the shallow cages; the difference approached significance.
3. The pattern of feeding activity over the day was significantly more U‐shaped in the shallow cages; this pattern accords more closely with physiological requirements.
4. Feather damage caused by pecking was slightly but significantly more severe in the deep cages at 70 weeks.
5. The proportion of cracked eggs (collected from 60 to 70 weeks) was significantly lower in the shallow cages.
6. The arrangement of the hens was such that within the shallow cages a higher proportion of birds was present in the front half.
7. It is suggested that some of the advantages conferred by the shallow cage may be related to the greater accessibility of the food trough. 相似文献
Mean digestibility coefficients of the yeast were 72 per cent for dry matter, 74 per cent for organic matter and 80 per cent for protein. The mean metabolisable energy value was 2550 kcal/kg.
In one of the feeding experiments it was found that 7.5 per cent of the fish meal in the control ration could be replaced by the yeast with no adverse effect on performance. When all of the fish meal in the control ration, i.e. 10 per cent, was replaced by the yeast, the effect on live‐weight gain of the chicks was negligible. However, when all of the fish meal and part of the soyabean meal in the control ration was replaced by 15 per cent yeast, some depression in chick growth occurred.
Similar rations containing a commercial sample of torula yeast gave significantly poorer performance than the corresponding controls at both the 10 and 15 per cent levels of inclusion of the torula yeast. 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. 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. Replacing groundnut oil cake (GNC) by Niger oil cake (NC) on an isonitrogenous basis, did not affect egg production, egg weight or the amount of food required per dozen eggs.
3. The percentage retention of nitrogen from diets containing 30% GNC or 30% NC was similar.
4. The ME value of NC used was 3025 kcal/kg.
5. It is concluded that NC can replace GNC in layers’ diets. 相似文献
2. Leaving the excreta for 1 week resulted in a decrease in nitrogen content from 59.5 g/kg to 54.1 g/kg (P< 0.05) and in the moisture content from 108.5 g/kg to 83.3 g/kg (P<0.05).
3. The mean values of available methionine, tryptophan and leucine were little affected by storage and were 0.340, 0.555 and 1.041 g/16 g N, respectively.
4. Salmonellae were not detected in any sample, coliform bacteria were detected in nine (26%) and anaerobic spore formers in 26 samples (76%). 相似文献
2. Protein and energy metabolism were studied in males from these selected lines fed on a diet of intermediate protein content.
3. All selected birds retained more nitrogen than those studied 10 years previously.
4. There was no difference in nitrogen retention between groups, although relative growth rate of group B birds was higher.
5. Heat productions relative to gross energy intake were 0.38 (group B) and 045 (group A). Energy retentions relative to gross energy intake were 0.39 (group B) and 0.35 (group A); the difference being primarily due to higher fat retention in group B.
6. Using a common maintenance requirement for metabolisable energy, group B utilised metabolisable energy for growth (0.78) better than did group A (0.71).
7. At 53 d of age plasma glucose (10%) and insulin (50%) were higher in group B than in group A. 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. During the last 7 years a random breeding sample of the production flock served as a genetic control.
3. Regressions of deviations of the production flock from the control flock on years, were highly significant for age at sexual maturity (‐2.18 d), egg production up to 275 d old (3.04 eggs), egg production to 500 d old (5.04 eggs) and egg weight at 14 months old (October) ( — 0.79 g).
4. The heritability of egg production up to 275 d old declined significantly from 0.35 to 0.19.
5. The realised heritability of egg production up to 275 d old was estimated to be 0.14.
6. The genetic correlation between egg production up to 275 d old and production in the residual part of the year was 0.48.
7. The rate of inbreeding in the production flock was 0.515% per generation and the expected rate of inbreeding in the control flock 0.21% per generation. 相似文献
2. Egg weight was poor with the low fat basal diet but increased in relation to the amounts of maize oil (4 and 30 g/kg) included in the diet.
3. With a diet containing 30 g olive oil/kg, egg weight was similar to that obtained with the diet containing the same amount of maize oil.
4. Rearing the birds on diets containing low or moderate amounts of linoleic acid did not affect the response to fatty acid content of the layer's diet.
5. It is concluded that the requirement of the laying hen for linoleic add is not higher than 9 g/kg but that egg weight does respond to higher dietary amounts of readily absorbable fatty acids. 相似文献
The drug increased weight linearly in this dose range throughout the medication period and at the lower dose level improved the food conversion.
The absence of histomoniasis in treated birds and controls shows that this was not due to suppression, by dimetridazole, of infection with Histomonas meleagridis.
Subsequent generations responded to dimetridazole but there was no cumulative effect from one generation to another. 相似文献
2. Increased mortality, perosis and other pathological changes involving a number of tissues were observed in birds fed on a low‐choline diet.
3. Methionine replaced part of the dietary requirement for choline at low dietary choline concentrations.
4. High dietary concentrations of choline (> 1 750 mg/kg) increased the requirement for dietary TSAA.
5. Increasing the dietary choline while maintaining the TSAA at an inadequate level may decrease performance. 相似文献