There was no significant effect on egg production when the calorie‐protein ratio of the diet was raised from 69 (i.e. k cal M.E./lb. per 1 per cent protein) to 90 but an increase to 103 reduced production and egg weight. It was found that maximum efficiency of food conversion was realised at ratios of 76 to 78.
The efficiency of conversion of dietary energy was unaffected by energy concentration in the diet.
The lightweight hybrid (Thornber 606) produced eggs more efficiently than either the Thornber 404 or the crossbred type. 相似文献
Egg size was reduced by protein restriction in the heavy strain but not in the light strain. On isocaloric diets the light strain consumed more food only at the lowest protein level whereas the heavy strain tended to eat progressively more as the protein was reduced from 16.5 to 12.5 per cent. When offered the low energy diet both strains ate more food, but substantially fewer calories, than when given diets of 2765 k cal. M.E./kg. Protein restriction had a marked effect in reducing live‐weight gains. Energy level of the diet had a large effect on weight gain and also on fat deposition in the carcass.
The greatest differences in performance due to diet did not occur at the time of maximum egg output. The evidence indicates that a diet which is too low in protein to support peak egg production will also fail to support normal egg production at any later stage of the laying year. 相似文献
There were no significant differences in egg production between diets but in both experiments a significantly improved food conversion ratio was obtained on the high maize diets, which also gave the highest level of energy consumption.
Most breed differences were not significant but in Experiment 1 the crossbreds produced significantly fewer eggs than the hybrids and in Experiment 2 the light hybrids gave a significantly better food conversion ratio than the two heavier types. The crossbred pullets consumed the most energy in both experiments and in Experiment 1 had significantly the worst energetic efficiency of egg production.
There were no significant interactions between type of pullet and type of diet in either experiment. Thus there were no indications that, at the energy levels investigated, favourable effects may be expected from the feeding of higher energy diets to the lighter hybrid type pullet.
The practical significance of feeding a high barley diet is discussed. 相似文献
High energy diets of about 1350 k cal./lb. containing 13, 15 and 17 per cent protein and medium energy diets of 13 and 17 per cent protein were fed to colostomised pullets to determine their digestibility, biological value and net protein value. In a further experiment a maize‐fishmeal diet of 1370 k cal. ME/lb. and 17 per cent protein, a soyabean‐maize diet of 1330 k cal. ME/lb. and 14 per cent protein and the latter diet supplemented with methionine and/or lysine were also examined. The mean BV and NPV values of the diets considered in Experiment 1 were 60 and 52 respectively.
Addition of methionine to the maize‐soyabean diet increased the BV from 43.9 to 61.6, the addition of lysine to 43.0 and the addition of both to 67.1.
A factorial method of calculating the daily protein requirement of the pullet based on the data for MFN and EUN and the NPV of each diet is presented. The estimate of 13.3 g. protein per day for the hybrid pullet is compared with other estimates in the literature. 相似文献
2. Productive performance was best with the low‐fat control diet, less good with the crude low erucic acid Span oil or lard‐containing diets, intermediate with the diet containing refined Span oil and worst with the diet containing regular rapeseed oil.
3. The various dietary treatments did not affect total lipid content of egg yolk but did affect the fatty acid composition of egg yolk lipids.
4. No substantial amounts of erucic acid were found in the eggs indicating that the hen is able to control the lipid concentration in egg yolk though control of the fatty acid composition of lipids is poorer. 相似文献
2. A combination of 3 growing climates, 3 laying climates (temperate, hot dry, hot humid), and 2 dietary energy concentrations (10.03 and 11.70 MJ ME/kg with protein concentrations proportional to energy) were tested for 46 weeks using 432 point‐of‐lay pullets.
3. Both growing and laying climates significantly affected most traits measured during the laying period. The patterns of egg production showed good persistency in all environments and differences observed reduced with age.
4. The difference between the high and low energy intake reduced at high ambient temperatures. Feeding low energy diets did not affect mean age at first egg, rate of lay or the egg output in the hot dry environment, nor egg weight in either hot dry or hot humid climates. Rather, feeding low energy diets resulted in improved body weight change in all 3 laying environments.
5. The growing climate and diet interacted significandy on body weight change, while highly significant interactions between laying climate and diet occurred on rate of lay, food and energy intake and egg weight during the laying period. 相似文献
In each period the diet had a significant effect on the rate of lay, egg output (g./day) showed a linear regression on protein intake. There was no indication that the amount of protein needed to maximise egg output was any less in one period than another, although the level of maximum output varied substantially as the year progressed.
Where the feeding of an inadequate level of protein in one period was followed by a higher level in the next, liveweight showed a marked recovery but there was little evidence of compensatory egg production. When the protein of the diet was reduced from 16 to 12 per cent, rate of lay fell sharply to a level below that of birds which had received the 12 per cent protein diet throughout. 相似文献
2. A series of diets of increasing protein content was offered. Protein quality was identical in all diets and tryptophan was demonstrated to be the most limiting amino acid in the protein mixture used.
3. The daily tryptophan requirement of the individual pullet was estimated, by indirect methods, to be 2.25 mg/g egg output plus 10.25 mg/kg body weight. Response curves for flocks of pullets are illustrated. Calculated optimum intakes of tryptophan for various ratios of costs of input to value of output are tabulated.
4. It is estimated that for a flock of mean body weight 1.5 kg, producing 55 g egg mass/hen d and consuming 110 g food/hen d, the optimum dietary tryptophan concentration is 1.7 g/kg when the marginal cost of supplying 1 kg tryptophan is 20 times the marginal value of 1 kg egg output. 相似文献
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
During the laying stage, diets in commercial use at this centre gave significantly higher egg yields, better average egg prices due to superior grading results and a higher margin over food cost than the same diets modified to conform with the nutrient recommendations of the National Research Council of America (1960).
Where the supplementary protein in both types of layers' diet was of vegetable origin, egg yield, food cost and margin of income over food cost were all significantly inferior to groups fed comparable diets containing supplementary protein of both vegetable and animal origin.
Soyabean meal and sunflower seed meal gave significantly poorer results when used in combination as the sole protein supplement compared with soyabean meal plus methionine. 相似文献
2. Pullets receiving these two diets displayed a slower, but more uniform growth rate than did birds offered a single conventional diet. Up to 11 weeks of age, control birds consumed significantly more protein while the converse was true from 11 to 20 weeks. These differences are discussed in relation to the stage of sexual maturity.
3. Broilers offered the split‐diets grew more slowly and had an inferior food conversion ratio compared with control birds fed on a two‐stage rearing programme.
4. Among the broilers offered split‐diets, the usual sex differences were not observed for weight gain or carcass fat content. 相似文献
2. Manipulating the metabolisable energy (ME) and/or nutrient density (ND) of complete layer diets failed to improve egg output at hot temperatures to that obtained at cold temperatures.
3. At both temperatures self‐selection increased protein, but not ME, intake. This increased egg output and body weight gain at the hot, but not cold, temperatures. At the hot temperatures pullets fed by self‐selection were the only ones to gain weight between sexual maturity and 28 weeks of age.
4. Nutrient intake patterns, related to each pullet's physiological age of sexual maturity, identified distinctive changes in protein intake and the selected protein: ME intake ratio of pullets fed by self‐selection. Pullets attempted to maintain a preferred protein:ME intake ratio, irrespective of the markedly different intakes of ME and protein at the two temperatures.
5. Pullets trained to self‐select nutrients from separate energy‐ and protein‐rich foods are better able to sustain egg output and body weight at sexual maturity when food intake is limited by high ambient temperatures. 相似文献
2. Restricted feeding during lay of pullets reared on the low‐protein diet substantially improved laying performance, the best results being obtained from pullets fed the low‐protein grower diet and restricted from 20 weeks. The laying responses of pullets restricted after peak‐lay at 40 weeks of age were not significantly different from those of birds restricted prior to peak‐lay.
3. Maximal egg production of 81 % over the 48weeks of the experiment was attained on an average daily ME intake of 270 kcal (1130 kJ) and a FCR of 2.06 : 1.
4. It is suggested that food restriction of laying pullets previously reared on low‐protein diets may be successfully utilised prior to peak‐lay provided such restriction is not so severe as to retard the rate of attainment of mature weight and a continued slight gain in weight thereafter. 相似文献
2. High ND diets increased body weights, eviscerated carcase weights, relative carcase yields and carcase skin yield, but not breast or total meat yields.
3. Feeding a low ND diet to 6 weeks followed by diets with progressively increasing ND yielded performance and carcases with qualities comparable to feeding diets of constant medium or high ND; consequently cost savings could be made.
4. Increasing E:Ps reduced body weights, eviscerated carcase weights and carcase yields. Breast and total meat yields from male but not female carcases, and skin yield of female but not male carcases decreased with higher E:Ps.
5. The fat contents of breast and thigh meat samples increased with ND. The fat content of breast but not thigh meat decreased with higher E:P. Dry matter contents of meat samples did not vary consistently with changes in fat content. 相似文献
2. Chick diets had no significant effects on rearing or subsequent laying performance.
3. Food‐regulated pullets were 7% lighter than pullets given the DPM diet ad libitum at 18 weeks but consumed 12.5% less food; growing treatments had no significant effect on subsequent egg production.
4. Hens housed in shallow cages laid 10.3 eggs/bird‐housed more than those in deep cages, produced 3.8% greater egg mass, consumed 2.7% less food and produced fewer damaged (cracked, broken and hair‐cracked) eggs (P< 0.001).
5. DPM‐containing layer diets had no adverse effects on egg production, or mortality; with 100 g DPM/kg efficiency of food conversion (EFC) was better than with 0 or 200 g/kg (P< 0.001).
6. Reduction of the energy intake of L110R and L220R hens with diets containing 110 and 220 g DPM/kg by 8.2 and 9.0% respectively, reduced the number of eggs laid/hen‐housed by 6 and 10.7 but improved the EFG (P< 0.001); there was no significant interaction between cage shape and energy regulation. 相似文献
2. Liver fat, carcass fat, liver weight and body weight increased markedly at the onset of sexual maturity.
3. Within the liver, the protein to DNA ratio did not alter significantly during development; glycogen was not consistently depleted by egg production.
4. Liver fat content was significantly correlated with carcass fat, liver weight and DNA concentration, and plasma total lipid and cholesterol, independent of stage of development; with body weight, liver protein, moisture, and protein to DNA ratio, excluding the period prior to commencement of sexual maturation; and with plasma phospholipid during lay.
5. Obesity was a feature of faster growing fowls which matured earlier, consumed more, utilised food less efficiently for egg production and produced fewer saleable eggs. 相似文献
2. Whole maize was found to be unsuitable.
3. Whole wheat or whole barley diets should not be introduced before the age of 10 weeks to avoid unacceptably high mortality due to cannibalism. Thereafter the principal results are reduced body weight at caging and retarded sexual maturity.
4. The addition of a vitamin‐trace element supplement had some effect in reducing mortality when whole grain diets were introduced before 10 weeks of age. 相似文献
2. The water content was highest in White Leghorn eggs, which were the heaviest.
3. Cholesterol content was similar in all eggs except for Dwarf Sussex in which it was less.
4. English Gamecock eggs contained a higher proportion of protein than those of the other breeds.
5. From the data presented, egg size, under similar conditions of feeding, does not determine the contents of components of the egg, but there are underlying genetic factors. 相似文献
2. Activities were higher in birds in cages than in those on the floor, reflecting perhaps the stress of caging. Activities increased with age.
3. Activities were higher in pullets selected for higher production.
4. The type of housing had no effect on egg production, but age at first egg, egg weight and 40‐week body weight were found to be affected significantly. 相似文献
2. Measurements of heat production and energy balance were made after peak lay with ovariectomised and sham‐operated laying pullets of both strains. Measurements on the ovariectomised pullets were made before and after implantation with oestrogen pellets.
3. Within each strain the ME requirements for maintenance (per kg W0.75), determined by linear regression analysis, were similar whether or not the starvation heat production data were included.
4. The ME requirements for maintenance decreased substantially after ovariectomy but subsequent implantation with oestrogen pellets did not increase these requirements.
5. Studies of hepatic enzyme activities indicated that the major influence of the mature ovary was on hepatic lipid metabolism. This was exerted through a specific stimulation of lipogenesis rather than a general increase in metabolism. 相似文献