Compensatory growth after under-nutrition in market turkeys: effect of low protein feeding and realimentation on body composition     

J N Auckland  T R Morris 《British poultry science》1971,12(1):137-150

Turkey poults were fed starter diets containing either 29 or 20 per cent crude protein. Live‐weight at 6 weeks was depressed by about 30 per cent in poults fed the low protein diet. From 6 to 10 weeks of age four protein levels were fed but carcass studies were restricted to the groups which received adequate amounts of protein at this stage. Sixty poults from each treatment were slaughtered for carcass studies at 6 weeks of age, and also at 7 weeks when the undernourished poults had reached the body weight attained by fully fed groups at 6 weeks. Further samples were taken for carcass analysis at 20 weeks of age.

Percentage body fat was increased and percentage protein in the fat‐free dry matter was decreased by feeding a low protein starter diet from o to 6 weeks. Poults fed the low protein starter diet retained nitrogen more efficiently during the period of undernutrition and in the first stages of recuperation. Following a return to full feeding at six weeks, body protein content was quickly restored, but a longer period was required before their body fat percentage was reduced to the level of fully fed controls.

The organs which were weighed were little affected, except in the case of the gizzard and liver which became proportionately heavier in retarded turkeys at 6 weeks of age. Only spleen weight appeared to have been reduced in relation to total body weight but it occupied a similar proportion in high and low groups when compared on a fat‐free basis. Some, but not all, of the organs weighed were restored to normal proportions by 20 weeks of age. However, dressing percentage and economic value of carcasses at market weight were not materially affected by early nutritional treatment.  相似文献   

The effect of low‐protein grower diets on the subsequent response of pullets to quantitative food restriction during lay     

D. Balnave 《British poultry science》1976,17(2):145-150

1. The laying responses of pullets fed from 8 weeks of age on a 12.5% protein grower diet and subsequently subjected to food restriction commencing at various times between 20 and 40 weeks of age were compared with those of pullets reared on diets containing 12.5 or 16% protein and given access to food throughout lay.

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   

Studies on the effect of lysine and methionine supplementation of a high‐protein maize‐soyabean diet and of a low‐protein barley‐white fish meal diet on the performance of caged layers     

N. Jackson  E. Squance  D. W. F. Shannon 《British poultry science》1967,8(1):43-53

Selected literature relating to the amino acid supplementation of layers’ diets is reviewed and the results of two experiments are presented.

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   

Compensatory growth in turkeys: effect of undernutrition on subsequent protein requirements   总被引：1，自引：1，他引：0  

J N Auckland  T R Morris 《British poultry science》1971,12(1):41-48

An adequate and a low protein starter diet (29 and 20 per cent crude protein respectively) were fed from o to 6 weeks of age. The poults receiving only 20 per cent protein were 17 per cent lighter at 6 weeks than the fully fed group. Turkeys from each treatment were then fed one of five levels of protein from 6 to 10 weeks of age. After 10 weeks all groups were fed adequate levels of protein to allow undernourished poults to exhibit compensatory growth.

The percentage protein required for maximum growth in the 6 to 10‐week stage was similar whether turkeys had been fully fed or undernourished from 0 to 6 weeks. But the “ effective “ percentage of protein required in the 6 to 10‐week stage, defined as the level which subsequently allowed maximum body weight at 20 weeks of age, was less for initially fully fed birds. This was because they had smaller growth deficits at 10 weeks and consequently made faster recovery in the limited time allowed.

Turkeys fed 29 and 17 per cent protein or 20 and 22 per cent protein in starter and grower diets respectively reached the same live‐weight at 20 weeks as fully fed turkeys which received 29 per cent protein from o to 6 weeks and 24 per cent protein from 6 to 10 weeks. The compensating turkeys ate about the same total weight of food as fully fed groups, but had a 10 per cent lower total protein intake.  相似文献   

Some effects of changing protein levels during the pullet laying year     

C. Fisher  T. R. Morris 《British poultry science》1967,8(2):153-161

Three diets containing 12, 14 and 16 per cent crude protein were fed to laying pullets from 23 to 63 weeks of age. The laying year was divided into three periods of 10, 15 and 15 weeks to examine the effect of feeding these diets at different stages of lay. Eighteen treatments were used, representing all possible combinations of three diets in the first period, three diets in the second period and two diets (16 and 12 per cent) in the third period. Two groups of 75 pullets were allocated to each treatment.

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   

The effects on rearing and subsequent laying performance of rearer diets containing two levels of protein and dried poultry manure or urea     

D. J. W. Lee  R. Blair  P. W. Teague 《British poultry science》1976,17(3):261-268

1. Six hundred and seventy‐two light‐hybrid pullets aged 6 weeks were allocated to eight experimental treatments and cage‐reared to 18 weeks of age when they were transferred to single‐bird battery cages and fed on a common layer diet.

2. In the 6‐ to 12‐week period four dietary treatments were applied: a diet containing about 160 g crude protein (CP)/kg with or without 50 g dried poultry manure (DPM)/kg (diets 2 and 1 respectively) and a diet containing about 140 g CP/kg with or without 50 g DPM/kg (diets 4 and 3). In the 12‐ to 18‐week period two additional diets were fed: diets 1 and 3 supplemented with 10 g urea/kg (diets 5 and 6 respectively). Diets containing DPM were formulated to utilise the CP, energy, calcium and 50% of the phosphorus content of DPM.

3. Pullets fed on diets 1, 2 and 5 (high‐protein) were significantly heavier at 18 weeks than those fed on diets 3, 4 and 6 (low‐protein). In the laying period total estimated egg weight, food intake and conversion were significantly greater, and the age at first egg was significantly less (2.4 d).

4. Dietary DPM had no significant effect on the 18‐week body weight but food consumption was significantly less and conversion was significantly improved. There were no significant effects on subsequent laying performance. Dietary urea caused no significant effects on rearing or laying performance.  相似文献   

Dietary selection of protein and energy by pullets and broilers     

J. D. Summers  S. Leeson 《British poultry science》1978,19(4):425-430

1. White Leghorn pullets and sexed broilers were allowed a free choice of two “ split‐diets “ which were concentrated sources of either crude protein (463 g/kg diet) or energy (13.32 to 14.00 MJ/kg diet).

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   

Volatile components in the breast muscles of chickens of different ages     

T. C. Grey  D. H. Shrimpton 《British poultry science》1967,8(1):35-41

Thirty‐eight volatile components have been found, of which 27 have been tentatively identified in the breast muscles of Arbor Acre broiler hybrids between the ages of 3 and 18 weeks. The study has been qualitative but, because standardised conditions of sampling and analysis have been used throughout, comparison between samples from different age groups is practicable.

For convenience in comparing the profiles of different age groups, but without implying any special organoleptic significance, the volatile components have been divided into 3 classes on the basis of their contribution to the total area of the chromatogram. Six large peaks together accounted for 82.5 per cent of this area in samples from 3‐week‐old birds, a second group of 6 smaller peaks accounted for 11.8 per cent, and 14 trace components made up the remainder. This pattern was typical of all but 2 of the age groups: at 9 weeks there were only 5 trace components instead of 13 or 14, and at 18 weeks the 14 components accounted for 17 per cent of the total chromatogram area instead of 2.6 to 7.0 per cent.

The possible organoleptic significance of the results has been briefly discussed.  相似文献   

Arginine--lysine interrelationships in the nutrition of broiler breeder pullets during the developmental period     

J R Couch  W W Abbott 《British poultry science》1974,15(5):467-479

Pullets were fed on diets containing various concentrations of lysine and arginine from 7 to 18 or 20 weeks. Thereafter a conventional layers' diet was fed and egg productivity measured—in the first two experiments for ten, and the third for six 28‐d periods. Pullets were also fed on a standard growers' type diet on a “skip‐a‐day” or on a 20% restriction basis in the third study.

Growth and age at sexual maturation were directly related to the lysine content of the diet and to a lesser extent to the arginine content. Pullets fed on diets with the lower concentrations of lysine and arginine required less food during the growing period and matured later than those fed on a complete diet ad libitum. They also laid more eggs and required less food to produce a dozen eggs. Higher egg production was obtained in the third experiment with low concentrations of lysine and arginine than with the “skip‐a‐day” or the restricted feeding programmes. Pullets fed on the normal grower diet ad libitum produced the smallest eggs in the first and third experiments with no difference in egg size in the second experiment. Pullets maintained on the “skip‐a‐day” or the restricted feeding programme also had a larger egg size than the control group fed on the same diet on an ad libitum basis.

An ingredient effect was observed in the third experiment. Of two diets containing identical calculated values of lysine and arginine, the one containing distillers' dried grains with solubles was superior to the one with soybean meal as regards weight at 20 weeks of age, amount of food consumed during the period 6 to 18 weeks of age and percentage egg production. It is possible that the soybean meal contained a better balance of amino acids than did distillers' dried grains with solubles which resulted in a significant increase in body weight at 20 weeks of age and a subsequent lower level of egg production. These data indicate that it would be best to use ingredients with an imbalance of amino acids in the protein as sources of lysine and arginine in pullet grower diets.

There were no differences in the mortality of the birds during the laying period which could be related to dietary treatment during the pullet growing period.  相似文献   

The nutrient intake of laying hens given a choice of diets,in relation to their production requirements     

G. C. Emmans 《British poultry science》1977,18(3):227-236

1. Sixty individually‐caged birds, each of two stocks, were offered either a complete diet (11.2 MJ ME, 173 g crude protein and 32 g Ca per kilogram) or a choice between the same diet and ground barley. All diets were offered ad libitum from 41 to 56 weeks of age.

2. Weight gain, rate of lay, mean egg weight, egg output, shell thickness and total food intake were unaffected by the treatments in either stock.

3. The mean intake of the complete diet was 825 and 845 g/kg of total intake with standard deviations between individuals of 73 and 61 g/kg respectively in the two stocks.

4. In birds given a choice of diet the one selected was related to output (P < 0.01).  相似文献   

The recovery of laying birds from a period of low protein feeding     

R C Jennings  T R Morris 《British poultry science》1965,6(4):321-326

Laying pullets which had been fed diets containing 7, 8½, 10, 11½, 13 and 14½ per cent crude protein for 10 weeks were returned to a normal diet containing 14½ per cent crude protein. For birds which had received the lowest protein diet, rate of lay improved from about 30 per cent to over 80 per cent in 4 weeks. Egg weight, body weight and food consumption also increased rapidly. In the period from 3 to 20 weeks after restoring a normal diet the pullets which had previously been fed 7 per cent and 8½ per cent crude protein showed a rate of lay and an average egg weight substantially better than that of control birds which had always received the 14½ per cent crude protein diet.

It is concluded that a period of low protein feeding does not impair the subsequent ability of the laying bird to reach normal levels of output. On the contrary, birds which are denied a normal protein intake for a time tend to compensate when returned to normal feeding by laying more eggs and bigger eggs. However, in this experiment, the compensation was not enough to offset the loss in yield incurred during low protein feeding.  相似文献   

Protein synthesis in the liver and breast muscle of chicks fed on a high protein diet     

K. Kita  J. Okumura 《British poultry science》1993,34(3):553-558

1. The influence of feeding a high protein diet containing 400 g crude protein (CP)/kg on liver and breast muscle protein synthesis in chicks was investigated using a large dose injection of l‐[4 ‐³H]phenylalanine.

2. Liver weight of chicks fed on the high protein diet was significantly heavier than that of chicks fed on a control diet with 200 g CP/kg, and breast muscle weight was not affected by the treatment.

3. Fractional and absolute protein synthesis rates, RNA and protein contents, and RNA:protein ratio of breast muscle were not influenced by feeding the high protein diet.

4. Feeding the high protein diet decreased fractional synthesis rate of liver protein, an observation explained by reduced RNA:protein ratio. Liver protein content was elevated by feeding the high protein diet and this resulted in no change in the absolute synthesis rate of liver protein.  相似文献   

Relationships between the degree of food restriction and welfare indices in broiler breeder females     

P. M. Hocking  M. H. Maxwell  M. A. Mitchell 《British poultry science》1996,37(2):263-278

1. Broiler breeder females were fed ad libitum, or according to a commercial food restriction programme or to gain 0.85, 0.70, 0.55, 0.40 or 0.25 of the body weight of ad libitum‐fed birds. Several indices of the welfare of the birds were assessed at 3‐weekly intervals to 18 weeks of age and related to body weight by regression analysis. Results for 6, 12 and 18 weeks of age are presented in detail.

2. Water intake was consistently higher in the 0.25, 0.40 and commercial restriction treatments.

3. There was a negative curvilinear relationship at each age between body weight and the heterophil‐lymphocyte ratio and plasma corticosterone concentration.

4. There was a positive relationship between the plasma concentration of creatine kinase and body weight at 12 and 18 weeks of age. The relationships between body weight and the plasma activity of alkaline phosphatase and aspartate transaminase changed with age and there were no differences between treatments for lactate dehydrogenase.

5. The time spent resting increased with body weight at each age. The relationship between time spent preening and body weight changed with age whereas that for oral activities was similar among restricted birds at 6, and among all treatments at 12 weeks of age. At 18 weeks there was an increase in oral activities with decreasing body weight.

6. Fearfulness was positively related to body weight. The response of the comb to phytohaemagglutinin injection was similar in all treatments and the antibody titre to injections of sheep red blood cells was curvilinear.

7. A principal components analysis of all measured traits at 6, 12 and 18 weeks of age was conducted. Most of the variables were redundant but at least one from each of the different classes of welfare indices was retained at 6 and 12 weeks of age.

8. It was concluded that a body weight during rearing in the range of 0.5 to 0.85 of ad libitum might provide for optimum welfare of broiler breeder females.  相似文献   

The effects of early and late maturity on the protein requirements of pullets     

D J Bray  R C Jennings  T R Morris 《British poultry science》1965,6(4):311-319

Growing pullets were exposed to two light patterns which caused a difference in sexual maturity of 5 weeks. From 28 to 38 weeks of age they were fed diets containing crude protein levels of 7.0, 8.5, 10.0, 11.5, 13.0 and 14.5 per cent. Yellow maize provided 45 per cent and soyabean meal 55 per cent of the protein in all six diets.

Rate of lay, egg weight and body weight were greater in the late maturing flock than in the early flock at the start of the assay and throughout the assay period. The late maturing pullets required more protein to reach and maintain their maximum potential than the early birds, presumably because their potential output was greater. The late birds showed a diminishing but continued response to protein up to the highest level fed (14.5 per cent corresponding to 23 g. protein per bird day). The early maturing pullets showed no response to dietary protein levels beyond 11.5 per cent and their estimated protein requirement was about 16 g. per bird day.

When limiting amounts of protein were fed (7.0–10.0 per cent of the diet) the two flocks achieved similar levels of egg output. In both flocks and throughout the assay, body weight and egg weight fell at the two lowest levels and increased at the three highest levels of protein.

It is concluded that the protein requirements of early maturing and late maturing flocks of pullets may differ, but only in a way which corresponds directly with their different potential outputs. In the late flock, which had the higher protein requirement, excellent production was obtained with a diet containing 14½ per cent crude protein all of which came from vegetable sources.  相似文献   

Performance of broiler breeder pullets as influenced by composition of grower and layer diets 1     

R. H. Harms  B. L. Damron  H. R. Wilson 《British poultry science》1968,9(4):359-366

An experiment was conducted to determine the influence of three grower systems upon the subsequent performance of broiler type breeder pullets. The grower systems were full feeding a 10 per cent protein diet, full feeding a 16 per cent protein diet, and a skip‐a‐day feeding of the 16 per cent diet. One‐third of the pullets fed according to each of the feeding programmes were fed on each of three different layer diets. The use of the low protein and the skip‐a‐day feeding resulted in delaying age at sexual maturity. Total rate of egg production was not affected by the grower diet; however, the number of “ settable “ eggs was increased when maturity was delayed.

Performance of the laying hens was not influenced by the composition of the layer diet. Fertility or hatchability was not influenced by composition of either the grower or layer diet. These data would indicate that the low protein diet or the skip‐a‐day feeding system can be effectively used with feeding replacement broiler type birds.  相似文献   

Responses in growth,food intake and food conversion efficiency to different dietary protein concentrations in meat‐type lines of Japanese quail     

L. Hyánková  L. D#akedková  H. Knížetová  D. Klecker 《British poultry science》1997,38(5):564-570

1. A total of 360 Japanese quail of 4 commercial meat‐type lines and two diet treatments (260 and 216 g/kg or 238 and 195 g/kg of crude protein (CP) in the starter and grower diet, respectively) were used.

2. The positive effect of a high CP diet on body weight was significant only for the first 4 weeks after hatching.

3. The mean age at inflection point of the growth curve (t ⁺) across lines and sexes was 1.4 d (0.6 to 2.8 d within line/sex groups) earlier for quail fed on a high CP diet than in quail receiving a low CP diet. The inflection (y ⁺) and asymptotic (A) weights were similar under both dietary protein concentrations. Nevertheless, the shape of the growth curve, characterised by the ratio y⁺1A and parameter of the maturing rate k, was significantly influenced by diet.

4. A higher food intake and less efficient food conversion were found for quail fed on a high CP diet in the period from 15 to 28 d of age.

5. The fattening traits such as body weight, cumulative food intake and food conversion, were not affected by dietary CP content at the age of 5 weeks.

6. The effects of line on body weight, food intake and food conversion are discussed.  相似文献   

A study of the effect of variation in the calorie‐protein ratio of a medium energy diet and a high energy diet containing sucrose on the efficiency of egg production in caged layers     

W. O. Brown  J. J. Waring  E. Squance 《British poultry science》1965,6(1):59-66

Literature pertaining to the variation in the protein content of layers’ diets is discussed and the lack of information on the effect of calorie‐protein ratio on food conversion is mentioned. The experiment described in the present paper was designed to test the effect of variations in calorie‐protein ratio on food conversion on a diet of high energy content (1340 k cal/lb.) based on sucrose supplementation and on a medium energy diet (1160 k cal/lb.). At the same time three types of pullet, Thornber 606, Thornber 404 and Light Sussex x Brown Leghorn pullets were compared on the two types of diet, each being fed at three nominal protein levels of 13, 15 and 17 per cent giving a total of eighteen treatments. The pullets were individually recorded for egg production, egg weight and food consumption. Meta‐bolisable energy crude protein determinations were carried out on each of the six diets employed and the actual calorie‐protein ratios calculated.

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   

Phosphorus requirements of poultry. VI. The phosphorus requirements of growing pullets between 8 and 18 weeks of age     

H Temperton  F J Dudley  G J Pickering 《British poultry science》1965,6(2):143-151

With pullet chicks during the first 8 weeks of life there were no significant advantages in mortality, growth, feed consumption or in the efficiency of the conversion of food to live‐weight through supplementing a basal diet composed of feeding stuffs of plant origin with inorganic phosphorus.

During the period 8–18 weeks the results showed a similar pattern. The birds in all groups grew satisfactorily and appeared normal. No consistent or significant differences occurred between the rearing groups in mortality, growth, food consumption of feed efficiency.

The results of the present experiments provide further confirmation that pullet chicks can be reared satisfactorily to 18 weeks of age on diets containing neither animal protein nor phosphorus supplements.  相似文献   

The effect of feeding a sub-optimum level of lysine to female chicks on the amino acid content of selected tissues and organs     

J R Couch  J H Trammell  J Cooper  F M Farr  W W Abbott 《British poultry science》1972,13(5):425-434

The amino acid content of the liver, brain, serum and leg muscle of broiler breeder female chicks was not influenced appreciably at 4 and 8 weeks of age by feeding a diet containing sub‐optimum levels of lysine. The feeding of the low‐lysine diet produced a slight effect on the amino acid content of the breast muscle and a decided effect on the amino acid content of the skin and bone marrow at 4 and 8 weeks of age. The amino acid content of the heart tissue from chicks which received the 0.53% lysine diet was higher at 4 weeks of age. No explanation for this observation can be offered. The more decided changes were produced in the bone marrow of the chicks fed the low‐lysine diet at 4 and 8 weeks of age.

There is a possibility that feeding the low‐lysine diet had an effect on protein synthesis in the bone marrow. Chicks fed the low‐lysine diet had apparently overcome the lysine deficiency in the synthesis of protein of the bone marrow at the end of the 12th week.  相似文献   

A quantitative analysis of the literature concerning the restricted feeding of growing pullets   总被引：2，自引：2，他引：0  

P. J. W. Lee  A. L. Gulliver  T. R. Morris 《British poultry science》1971,12(4):413-437

The sexual maturity of growing pullets can be retarded either by restricting calorie intake or by feeding a diet deficient in one or more essential amino acids, Several methods have been proposed for achieving either of these objectives. In this review the methods have been classified as (a) limiting the birds’ time of access to food, (b) quantitative food restriction, (c) the use of low energy diets and (d) dietary protein restriction.

Food restriction by limiting the time of access to food has given inconsistent results and is an unsatisfactory technique. Birds quickly learn to eat normal quantities of food in a very short space of time.

Quantitative food restriction has been widely used in experiments and is usually applied from about 6 to about 20 weeks of age. The available evidence enables relationships to be established between the degree of food restriction and subsequent body weight and sexual maturity. The effect of rearing treatment on mortality and rate of lay is also examined.

The ad libitum feeding of a low‐energy growing diet has always resulted in greater rearing food costs. This is because moderate reductions in energy content of the diet are offset by higher food intake. Diets sufficiently low in energy to cause a reduction in calorie intake will involve the purchase and handling of very large proportions of non‐nutritive material.

The use of protein‐deficient diets during the growing period, or from one day of age, offers a suitable means of delaying sexual maturity. The effects of such a treatment are apparently very similar to those of restricted feeding, but there is a lack of suitable comparisons of the alternative methods.  相似文献