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

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.     

Effects of dietary supplements on the nutritive value of jack beans (canavalia ensiformis) for the young chick

1. Two experiments were conducted with young chicks to examine the efficacy of dietary supplements of amino acids, creatine and potassium acetate in the alleviation of adverse effects of auto‐claved jack beans (AJB).

2. Creatine supplementation of AJB diets markedly enhanced the efficiencies of food and nitrogen utilisation of chicks, restoring these indices to control values. The improvement in nitrogen utilisation was enhanced further on providing creatine with a mixture of 2‐aminoiso‐butyric acid, arginine and lysine.

3. Potassium acetate induced striking improvements in the nitrogen retention efficiencies of chicks fed on AJB diets.

4. Liver weights, as a proportion of body weight, generally increased on feeding AJB diets, the effects being marked with the AJB diet supplemented with arginine and lysine.

5. Hepatic urea concentrations were elevated in all groups receiving AJB. Canavanine, a toxic amino acid component of AJB, could not be detected in acid hydrolysates of livers from chicks fed this legume.

6. Temperature and the volumes of water employed in the preparation of AJB are important determinants of its nutritional value.     

Food intake adjustments of chicks: Short term reactions to deficiencies in lysine,methionine and tryptophan

1. Two experiments were conducted to compare food intake responses of broiler chicks fed diets varying in lysine, methionine, and tryptophan. Diet D was formulated to create simultaneous deficiencies of lysine, methionine, and tryptophan. Diet A matched National Research Council (1984) recommendations for broilers, and diets B and C were, respectively, 2:1 and 1:2 mixes of diets A and D.

2. Short‐term food intake can provide information on the sequences of adaptation of chicks to a diet deficient in essential amino acids.

3. Chicks consumed 26% less of diet D than A during the first 24 h posthatch. When chicks fed diet A or D to 7 d of age were then fed one of 4 diets singly, within 24 h intake was lowest for chicks fed diet D. Within 48 h, food intake of diet C was more than that of diet D and less than that of diet A, while for diet B intake was more than of diet D but not different from diet A.

4. In the second experiment, chicks were fed diet A to 8 d and then diets A or D alone or given a choice of diets A and D from 8 to 20 d of age. Within 4 to 8 h, food intake of chicks fed diet D alone decreased markedly followed by partial recovery within 24 h. In a choice setting, consistent preference of Diet A over Diet D was observed within 7 h followed by stabilisation at about 65% diet A to 35% diet D.

5. Chicks fed diet D alone from 8 to 20 d of age, then placed in the same choice situation preferred diet A to D with a delay of less than one h and stabilisation at about 85%. Chicks provided a choice of diets A and D from 8 to 20 d, and then diet D alone reduced their food intake more quickly than those not given a choice initially.

6. Broiler chicks appear to react to amino acid deficiencies within a short period (hours) by adjusting their feed intake and/or selection. The response is influenced by age and prior experience.     

Response of broiler chicks to threonine‐supplemented diets to 4 weeks of age

1. Two experiments were carried out to determine the response of broiler chicks to threonine‐supplemented diets between 10 and 28 d and 7 and 21 d of age, respectively.

2. In the first experiment female broiler chicks were fed on 11 experimental diets. Two iso‐energetic basal diets (diets 1 and 2) were prepared with 200 and 160 g CP/kg and 7·6 and 6·0 g threonine/kg respectively. Both diets contained 11·5 g lysine and 8·7 g sulphur‐containing amino acids/kg. Diet 3 was composed of diet 2, supplemented with all essential and non‐essential amino acids (EAA and NEAA, respectively) except threonine, to the concentrations of the amino acids in diet 1. The NEAA were added as a combination of glutamic acid and glycine. Diets 4 to 11 had the same compositions as diet 3, but contained increasing amounts of threonine.

3. For birds fed on diet 2, gain was significantly lower and food/gain ratio was significantly higher than for birds fed on diet 1. Supplementation with EAA, NEAA and threonine to the same concentrations in diet 1 resulted in a performance similar to that found on diet 1.

4. In experiment 2, male and female broiler chicks both received 10 experimental diets. Diet 1 contained 220 g CP/kg and 8.5 g threonine/kg, diet 2 contained 160 g CP/kg from natural raw materials and 6 g threonine/kg. Both diets contained 12·4 g lysine and 9·3 g sulphur‐containing amino acids/kg. Basal diet 2 was supplemented with all EAA and NEAA to the concentrations of basal diet 1, except for threonine. Diets 3 to 10 had the same compositions as the supplemented diet 2, but contained increasing amounts of threonine.

5. For male and female chicks on diet 2, gain was significantly lower and food/gain ratio significantly higher than those on diet 1. Diet 10 (160 g CP/kg plus all EAA, including threonine, and NEAA supplemented to the concentrations of diet 1) resulted in the same performance as diet 1.

6. The results indicate that, when low protein maize‐soyabean meal diets supplemented with EAA and NEAA with 13·31 MJ ME/kg were fed to male and female broiler chicks until 21 d of age, improvements in gain and food/gain ratio were obtained when the dietary threonine content was increased to 7·25 g/kg. When female chicks were fed threonine‐supplemented diets to 28 d of age, improvement in gain and food/gain ratio was obtained when the threonine concentrations were increased to 6·32 g/kg diet.

7. Curves have been fitted to the data, from which a cost‐benefit analyses can be made and an optimum threonine dose calculated, using local prices.     

Effect of dietary protein,essential and non‐essential amino acids on the performance and carcase composition of male broiler chickens

1. The present study was conducted to determine the possibility of using low‐protein broiler diets supplemented with synthetic amino acids. The effects on performance, carcase composition and nitrogen retention were evaluated.)

2. A starter diet was given, ad libitum, from 7 to 21 and a finisher diet from 21 to 42 d of age. Body weight, weight gain, food intake and food conversion (FC) were determined at 3 and 6 weeks of age. Abdominal fat deposition (AFD), carcase yield, carcase fat and protein and nitrogen retention were determined at 6 weeks of age. During the starter period chicks were given a 231 g/kg crude protein (CP) diet and a low protein diet supplemented with synthetic amino acid, a: to National Research Council recommendations, b: to the concentration of the control diet, and c: in agreement with the pattern of body composition. Glutamic acid and glycine were added to some diets as sources of non‐essential amino acids (NEAA). All diets contained 12.62 MJ metabolisable energy (AME_n)/kg. The diets administered between 3 and 6 weeks were comparable to the starter diets, except that they contained more AME_n (12.85 MJ/kg) and less protein.

3. Performance equal to that of high protein controls was obtained with birds fed a low protein diet supplemented with synthetic essential and NEAA to the amounts in the control diet or based on the amino acid profile of body protein. This was not achieved with low protein diets supplemented with synthetic amino acids to the amounts recommended by NRC.

4. Without altering performances, the efficiency of protein utilisation of birds fed on low protein diets was superior to that of birds fed on the commercial control diet and their nitrogen excretion was reduced by 26%. The percentage carcase yield and protein was unaffected by the dietary regimen but carcase fat content and AFD increased as the protein content of the diet decreased.

5. These results show that it is possible to obtain the same performances with low protein diets supplemented with synthetic amino acids, using an ideal amino acid balance. However, low protein diets result in a higher carcase fat content.     

Uptake of certain amino acids in vitro in chickens previously subjected to three methods of dietary restriction

1. From 8 weeks of age cockerels and pullets were restricted for 8 or 12 weeks either by rationing, by feeding a low lysine diet or by feeding a diet low in protein but balanced in respect of all amino acids.

2. There was a significant decrease in growth rate of the birds as a result of the restrictive treatments.

3. The dietary treatments affected the rate of uptake of the four amino acids tested—arginine, lysine, histidine and glycine—although the effect was not significant in all cases, neither was it consistent throughout.     

Amino acid interactions in chick nutrition. 4. Growth, food intake and plasma amino acid patterns

A series of experiments has been conducted with chicks to study the effects of excess lysine, leucine and incomplete mixtures of amino acids on growth, food intake and plasma amino acid patterns.

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.     

Comparative responses of genetically lean and fat chickens to lysine,arginine and non‐essential amino acid supply. I. growth and body composition

1. Three experiments were performed to study the effects of amino acid imbalance on the growth of genetically lean (LL) or fat (FL) male chickens from 28 to 42 d of age. In experiment 1, five concentrations of digestible lysine were compared (4.75, 6.75, 7.75, 8.75 and 9.75 g/kg). In experiment 2, four concentrations of digestible arginine were compared (6.53, 7.69, 8.84 and 10.0 g/kg). In experiment 3, three diets were compared: a high‐protein diet (189 g CP/kg), a low‐protein diet containing added essential amino acids (EAA) (144 g CP/kg) and this low‐protein diet supplemented with 40 g/kg of non‐essential amino acids (NEAA) (glutamic acid + aspartic acid).

2. LL birds exhibited a lower growth rate than the FL when the diet was deficient in either lysine or arginine. Plotting weight gain against lysine or arginine intake suggested that most of this effect was caused by variations in food intake.

3. When protein gains (body or total proteins) were plotted against lysine or arginine intake, LL chickens appeared more efficient than FL chickens.

4. Similar growth rates, although slightly lower in FL, were obtained with low‐ and high‐protein diets. However, NEAA supplementation of the low‐protein diet reduced adiposity of LL and did not modify that of FL. Increasing crude protein content (all amino acids) was more effective than NEAA supplementation in decreasing the adiposity of both lines.     

Nutritive content of house fly pupae and manure residue 1

The metabolisable energy value of pupae of Musca domestica L. and digested poultry manure was determined to be 10.6 and 2.4 MJ/g (2528 and 580 kcal/g), respectively. Chemical analyses showed that pupae contained 61.4% protein and 9.3% fat: their amino acid composition was comparable with that of meat‐and‐bone meal or fish meal and was better than soybean oil meal.

A feeding trial was conducted to evaluate house fly pupae and catabolised poultry residue as alternative protein sources to soybean meal for growing chickens.

No significant difference (P>0.05) in weight gain was observed between the control and chicks fed pupae in their diet from 1 d to 4 weeks of age. Food conversion of the chicks fed digested poultry manure was significantly (P<0.05) inferior to that of the controls.     

The effect of dietary lysine level, restriction of food intake and sampling time on the levels of amino acids in the blood plasma of chicks

A suitable procedure for obtaining blood samples was established from an investigation of (a) diurnal variations in plasma amino acid concentrations and (b) the effect of controlling food intake on plasma amino acid levels.

Restriction of feeding to a 40‐min period, 105 min before sampling, significantly increased total plasma amino acid levels (P< 0.05) and individual concentrations of serine and proline (P<0.05) and glycine (P<0.01). The cause of these changes is not clear. Amino acid concentrations in samples taken at different times during the day were fairly constant. In the sampling procedure adopted routinely, birds were allowed free access to their diets for two weeks and sampled at 14.00 h on day 14.

The effect of dietary lysine level, at two protein concentrations, on plasma amino acid levels was evaluated. With inadequate and excessive dietary lysine concentrations total plasma amino acid levels were generally elevated. Plasma levels were least with diets containing 0.9 to 1.15% lysine.

The lysine requirements for optimum performance measured by growth rate, food conversion efficiency and nitrogen retention were identified as 1.2% with a 21% protein diet and approximately o‐8% with a 16% protein diet. The data indicate that efficient utilisation of dietary protein and relatively low levels of amino acids in the plasma are fairly closely related.     

Tissue content of α‐tocopherol and oxidative stability of broilers receiving dietary α‐tocopheryl acetate supplement for various periods pre‐slaughter

1. The effects of dietary α‐tocopheryl acetate on the α‐tocopherol status of chicken plasma and tissues were investigated. The rate of iron‐ascorbate‐induced lipid peroxidation was also studied.

2. One hundred and forty four chicks were divided into 6 groups: one control group was fed a basal diet of 30 mg α‐tocopheryl acetate/kg food for the duration of the trial. A supplemental diet of 200 mg α‐tocopheryl acetate was fed to each of the odier 5 groups for 1,2,3,4 or 5 weeks prior to slaughter.

3. Supplementation resulted in an increase in α‐tocopherol in plasma and all tissues examined. Saturation levels of α‐tocopherol were observed in plasma after 1 week of feeding and in tissues within 3 to 4 weeks of feeding.

4. Supplementation with α‐tocopheryl acetate for up to 4 weeks pre‐slaughter resulted in significant reductions in susceptibility to induced lipid peroxidation.

5. Overall, the results show that feeding 200 mg α‐tocopheryl acetate/kg food to chicks for at least 4 weeks prior to slaughter is necessary to optimise muscle content and stability against lipid peroxidation.     

A comparison of three methods of food restriction of laying‐type pullets on growth and laying performance

1. Three methods of restricting the growth rate of pullets from 8 to 20 weeks of age were compared. They were: quantitative food restriction, a diet low in lysine and arginine and a low protein diet.

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.     

Chick bioassay of lysine. I. Development of assay procedure

A series of experiments have been conducted with young chicks to develop a valid bioassay for the available lysine content of protein concentrates. The greatest problem to overcome was that of the secondary effects of adding test protein to a well‐defined basal diet. The solution to such a “ protein effect” was based upon the development of a reference standard diet with specifications (except for lysine) to be maintained in all test diets irrespective of supplementary levels of test proteins and amino acids.

A reference standard diet was established in which a mixture of maize meal, sesame meal and dried whey provided 20 per cent crude protein. This diet was shown to be deficient in no dietary factors other than lysine and, when adequately supplemented with lysine, it supported excellent chick growth. The adaptation of the diet for assay purposes is described; it involves the replacement of part of the dietary protein by an amino acid mixture simulating the composition of the basal protein. The potential assay range lies between 0.05 and o‐8 per cent of L‐lysine hydrochloride supplementation.     

Restricted feeding of broiler breeder pullets during the rearing period and its effect on productivity and breeding

A total of 2000 broiler breeder pullets was used for an experiment comparing two levels of restricted feeding from 6 to 20 weeks with three levels of low‐lysine feeding from o to 12 weeks of age. The object of the experiment was to obtain matching body weights at 20 weeks of age between the two levels of quantitative restriction and the highest and lowest levels of lysine feeding and to compare subsequent biological performance during lay. A control treatment was included in which birds were fed ad libitum at all stages.

Both methods of nutrient restriction reduced intake to 20 weeks of age. From 1 d to 60 weeks of age total food intake was reduced in proportion to the degree of restriction applied during the growing stage.

Sexual maturity was delayed by both methods of restriction, though low‐lysine diets produced a greater delay than quantitative restriction. Production of total eggs and of settable eggs was increased by both quantitative food restrictions and by the least severe of the lysine‐deficient diets. Following quantitative restriction egg size and fertility were both improved, but these advantages were not obtained by lysine restriction.

Mortality and culling were mainly influenced by a high incidence of “rupture of the gastrocnemius tendon “ which occurred exclusively in pullets fed lysine‐deficient diets during rearing.

It is concluded that quantitative restriction is to be preferred because of its advantageous effects on egg weight, rate of lay and fertility, and because it avoids the high mortality rate found with severe lysine restriction.     

Effects of ascorbic acid and 1, 25‐dihydroxycholecalciferol on alkaline phosphatase and tibial dyschondroplasia in broiler chickens

1. The effects of graded amounts of dietary ascorbic acid with or without 10 μg/kg dietary 1,25‐dihydroxycholecalciferol on performance, blood and bone variables were measured in broiler chicks.

2. 1,25‐Dihydroxycholecalciferol prevented the tibial dyschondroplasia and rickets caused by feeding a low calcium diet. Gain:food was decreased, but body weight was not affected by feeding 10 μg/kg 1,25‐dihydroxycholecalciferol. Phytate phosphorus retention was increased by dietary 1,25‐dihydroxycholecalciferol.

3. Dietary ascorbic acid did not influence the incidence of tibial dyschondroplasia, but did reduce the incidence of rickets at a dietary concentration of 250 mg/kg. Gakv.food was increased when 250 or 500 mg ascorbic acid/kg diet were added along with 10 μg/kg 1,25‐dihydroxycholecalciferol in one of two experiments.

4. Alkaline phosphatase activity and plasma 1,25‐dihydroxycholecalciferol were not affected by the dietary treatments. Plasma 25‐hydroxycholecalcif‐erol concentration was decreased by dietary 1,25‐dihydroxycholecalciferol.

5. Ascorbic acid had no synergistic effects with 1,25‐dihydroxycholecalciferol on the blood and bone variables investigated in broiler chickens at the dietary concentrations of 1,25‐dihydroxycholecalciferol used in this work.     

Effects of dietary protein,methionine and lysine on urinary amino acid excretion in turkeys1

1. Two experiments were conducted to determine the influence of dietary protein and amino acids on urinary excretion of amino acids and nitrogen in colostomised turkey hens.

2. Normal and colostomised turkeys 8 weeks of age were fed on control and high protein diets. Body weight gains of both types of birds were similar. Diet did not affect the amino acids in the urine significantly, but urinary nitrogen was higher with the high protein diet.

3. Normal and colostomised turkeys 10 weeks of age were fed a diet with either supplemental DL‐methionine or L‐lysine hydrochloride (each 20 g/kg diet). DL‐methionine depressed gain and resulted in considerable excretion of methionine in urine. Lysine had little effect on weight gain or urinary lysine.     

Maximum nutritional response to poor‐quality protein and amino acid utilisation

1. Although the theory of responses to amino acids suggests that, providing sufficient of the limiting amino acid is fed, it should be possible to elicit maximum growth response, maximum response is not usually elicited by poor‐quality proteins.

2. It has been suggested that this failure to elicit maximum response is a reflection of poorer limiting amino acid utilisation from poor‐quality proteins. This interpretation conflicts with the theory of general amino acid imbalance which proposes that amino acid excesses do not impair the utilisation of the limiting amino acid.

3. Three protein mixtures of different quality were made by mixing maize gluten meal and soyabean protein concentrate in constant proportions, supplementing with tryptophan, threonine and arginine to adequacy and varying amino acid score (0'62, 0^‐71 or = 1–0) by varying additions of free lysine. The 3 mixtures were diluted with protein‐free ingredients to produce 3 diet series, each providing 3–7, 6–5, 9–2, 120, 14–8 and 17–5 g lysine per kg. Each diet was fed to 4 cages of 2 chickens each from 4 to 14 d of age in a randomised block experiment. Food intake, body‐weight and body‐nitrogen gain were measured.

4. Differences in protein quality were confirmed by regression analyses of body‐weight response to protein intake (Net Protein Ratio) and body‐nitrogen response to nitrogen intake (Net Protein Utilisation) in the linear range. Regression analyses in the linear range of body‐weight or body‐nitrogen response to lysine intake showed no adverse effect of protein quality on lysine utilisation. Curvilnear analysis (Reading flock response model) confirmed this finding.

5. Maximum response could not be obtained with the poorest protein quality. It is illogical to invoke impaired utilisation of the limiting amino acid to explain this. A small decrease in net energy yield of the diet may be sufficient to explain the effect, but it is more likely that the depletion of the limiting amino acid from tissue (muscle) protein which results from feeding poor‐quality protein explains the effect.     

Comparative responses of genetically lean and fat chickens to lysine,arginine and non‐essential amino acid supply. II. plasma amino acid responses

1. Three experiments performed to study the effects of amino acid imbalances on the growth of genetically lean (LL) and fat (FL) male chickens from 28 to 42 d of age were described by Leclercq et al. (1994). The plasma amino acid concentrations of birds on selected treatments from that paper are reported here. In experiment 1, three dietary concentrations of digestible lysine were compared (4.75, 6.75 and 7.75 g/kg). In experiment 2, two dietary concentrations of digestible arginine were compared (6.53 and 10.00 g/kg). In experiment 3, three diets were compared: a high‐protein diet (189 g CP/kg), a low‐protein diet containing added essential amino acids (144 g CP/kg), and this low‐protein diet supplemented with 40 g/kg of non‐essential amino acids (NEAA; glutamic and aspartic acids).

2. The present results are compared with two earlier reports on the same genotypes. The LL consistently had lower plasma concentrations of me‐thionine, cystine, phenlyalanine, isoleucine and valine, and higher concentrations of histidine, than the FL chickens. In 4 of 5 experiments, LL leucine concentrations were lower, and glutamic acid, tyrosine, glutamine and alanine were higher, than in the FL. The other amino acids measured; arginine, lysine, aspartic acid, glycine and serine, exhibited variable responses among the experiments.

3. When the limiting essential amino acids, lysine and arginine, were added to a deficient diet, the plasma concentration of the supplemented amino acid increased while the others remained constant or decreased.

4. When glutamic and aspartic acids were added to the low protein diet, plasma amino acid responses were similar to those of adding a limiting amino acid to a deficient diet, except that alanine exhibited a dramatic increase.

5. Although there were genotype by diet interactions for several amino acids, the interactions were caused by differences in the degree of the responses, not in their direction.

6. These results suggest that the FL and LL genotypes do not utilise various amino acids with the same efficiency and, as a consequence, the ideal profile of dietary amino acids should not be the same for both lines. The results support the hypothesis that selection for fatness and leanness changed the amino acid requirements independently of the: effects of food intake.     

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

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.     

The nutritional value of low lathyrogenic Lathyrus (Lathyrus sativus) for growing chicks

1. The feeding value of new low β‐N‐oxalyl‐amino‐L‐alanine (BOAA) lines of Lathyrus sativus (lathyrus) and the benefits of dehulling the seed or of pre‐adapting chicks to lathyrus‐based diets were examined in several experiments.

2. Chicks fed on diets containing 400 g/kg of the low (1.3 g BOAA/kg seed) and medium (2.2 g BOAA/kg seed) BOAA lines did not differ (P>0.05) in weight gain (WG) or in apparent fat and protein digestibilities compared to birds fed on a wheat‐based diet.

3. Consumption of 600 g low BOAA lathyrus/kg diet caused a slight, but significant (P< 0.05), decrease in WG. Food efficiency decreased as the amount of dietary lathyrus was increased, suggesting that lathyrus may contain an antinutritive factor(s) other than BOAA.

4. Removal of the hull (70 g hull/kg seed) from the seed did not affect chick performance (P> 0.05).

5. Pre‐adapting chicks for 7 d to diets containing up to 600 g medium line lathyrus/kg diet did not reduce the detrimental effects of the lathyrus.

6. Although dehulling and pre‐adaptation of chicks to lathyrus were not beneficial, the low and medium lines of lathyrus tested show potential for use in chick diets up to at least 400 g lathyrus/kg diet.