Effects of tryptophan supplementation to a maize‐based diet on lipid metabolism in laying hens

1. Experiments were conducted with laying hens to determine the effects of supplementing 0, 1.0, 2.0 and 3.0 or 4.0 g trp/kg diet to a maize and soyabean meal‐based laying ration (basal tryptophan = 1.66 g/kg) on tissue lipid concentrations.

2. Plasma cholesterol, triglycerides and nonesterified fatty acids were increased by supplementing the diet with 1.0 g trp/kg diet and decreased with 3.0 or 4.0 g trp/kg diet. A significant quadratic effect of supplemental tryptophan was observed on plasma lipids in most cases. The observed effects diminished with time. No consistent changes were observed in plasma glucose concentrations.

3. Total liver lipids were reduced by supplemental tryptophan at all concentrations.     

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.     

High,low, or familiar? Nest site preferences of experienced laying hens

1. The aim of this study was to investigate which nest heights are preferred by laying hens in the absence of familiar nest locations and whether preferred nest heights are more attractive than a familiar location. In two experiments, a total of 108 hens of four different layer breeds, which were at least 50 weeks of age, were studied.

2. In the first experiment, hens were given individual free choice between nests for 1-week at four different heights (0 cm, 39 cm, 78 cm, and 117 cm above ground). Hens of the four breeds differed in their nest height preferences (P = 0.0013). However, hens of three breeds preferred ground level nests (P < 0.007) and the fourth line showed an equal preference for the ground level and level three, the latter level corresponding to the height of the nests in their home compartments.

4. In the second experiment, hens from the four breeds were given a choice between ground level nests and nests at a familiar location, i.e. at the same location as in their home compartment. Hens of all strains preferred the familiar nest location (P = 0.002) and preferences did not differ between strains (P = 0.77).

5. Laying hens seem to prefer nests at ground level in the absence of a familiar nest. However, if possible, experienced 50 week old hens continue to use a familiar nest location instead of a ground nest location. The results are discussed with respect to a potential primary preference that may be modifiable by experience and with respect to possible relevance in commercial housing.     

Effects of restricting the amounts of medium or low‐energy diets fed to laying hens in different colony sizes

1. Light hybrid hens between 32 and 68 weeks of age kept 4, 5 or 8 birds to the cage received one of three energy intakes, from a medium‐ or low‐energy diet.

2. Ad libitum fed birds laid more and heavier eggs than any of those restricted. A decrease in daily egg output of about 5 g was associated with each 100 kJ decrease in daily intake of metabolisable energy.

3. For the same energy intake, egg output of birds fed on the low‐energy diet was markedly greater than that associated with the medium‐energy diet.

4. The mortality of birds receiving restricted quantities of the medium‐energy diet was two to three times greater than that associated with similar rationing of the low‐energy diet.     

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.     

Effects of dietary protein content,addition of nonessential amino acids and dietary methionine to cysteine balance on responses to dietary sulphur‐containing amino acids in broilers

1. Two experiments were conducted with male broiler chicks from 2 to 5 weeks of age to determine the effect of dietary protein content and amino acid balance on the response to dietary sulphur‐containing amino acids (SAA) in terms of performance and carcase quality.

2. In experiment 1, 5 graded amounts of a DL‐methionine and L‐cysteine (1:1 by weight) mixture were added to basal diets containing 197 or 233 g crude protein/kg. The diets containing 197 g protein/kg were fed with or without the further addition of 36 g crude protein/kg from nonessential amino acids. The amino acid balance of all diets was kept constant for all essential amino acids except the SAA. In experiment 2, 5 graded amounts of SAA from either a crystalline source (DL‐methionine or a mixture of DL‐methionine and L‐cysteine) or from intact proteins were added to a diet containing 208 g protein/kg.

3. At each protein concentration there were significant responses to the SAA addition in weight gain, food conversion efficiency, and carcase quality. Non‐linear exponential regression analyses were used to describe bird responses to SAA concentration. The broiler chick's requirement for SAA increased with increasing dietary protein concentrations ranging from 197 to 259 g protein/kg.

4. The utilisation of SAA differed also with differences in origin (crystalline or peptide‐bound), and methionine:cysteine balances. Compared to DL‐methionine, a 1:1 mixture of DL‐methionine and L‐cysteine was only 81% or 86% as effective in supporting growth or food conversion, respectively. SAA from added protein was even less effectively utilised.

5. The addition of nonessential amino acids tended to decrease food intake without affecting SAA utilisation.

6. Slaughter yield and breast meat yield were clearly increased while fat deposition was clearly decreased, by SAA addition. The response in breast meat yield suggested an important economic benefit for further meat processing. Nitrogen retention was significantly enhanced by SAA supplementation from crystalline sources, and this led to reductions of up to 30% in the amount of nitrogen excreted per kg weight gain.     

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.     

Feeding value of rice distiller’s dried grains with solubles as protein supplement in diet of laying hens

A feeding trial of 10 weeks duration was undertaken on laying hens (n = 240) to evaluate feeding value of rice distiller’s dried grains with soluble (rDDGS) with or without enzyme supplementation (α-amylase, β-glucanase, xylanase, carboxymethylcellulase, pectinase, proteinase, α-galactosidase, β-galactosidase, lipase, and phytase), following 4 × 2 factorial design, on egg production, nutrient utilization, and cost economics of egg production. The birds were randomly assigned to eight dietary treatments with 30 birds/treatment. The birds were housed individually in layer cages and each bird was taken as an experimental unit. Eight experimental diets were prepared by incorporating four levels (0, 50, 75, and 100 g/kg) of rDDGS with and without enzyme supplementation. The results revealed a significant (P < 0.01) increase of egg mass, feed intake, egg production, and body weight gain in dietary treatments with up to 75 g rDDGS though the values were statistically similar to the hens fed 100 g rDDGS. Enzyme supplementation resulted in significant (P < 0.01) improvement of egg mass, egg production, feed conversion ratio (FCR) per dozen eggs, FCR per kilogramme egg mass, and net FCR. The significantly (P < 0.01) higher yolk index was observed at 100 g rDDGS level, while shell thickness improved significantly (P < 0.01) up to 75 g rDDGS level. No significant effect of rDDGS inclusion was observed on shape index, albumin index, and Haugh unit. Enzyme supplementation significantly improved the shell thickness and yolk colour of eggs. Nitrogen, calcium, and phosphorus retention and dry matter metabolizability did not show any significant treatment effects. There was significant (P < 0.01) reduction in feed-cost per kilogramme egg mass or per dozen eggs with the increased DDGS levels and dietary enzyme supplementation. It was concluded that rDDGS can be used up to 100 g/kg diet of laying hens along with enzyme supplementation for better productivity of layer hens.

     

The effect of delaying the onset of laying in pullets with a low‐calcium diet on subsequent egg production

1. A low‐calcium diet (0.5 g calcium/kg) was used to prevent the onset of laying in young pullets.

2. It was fed at 16 weeks of age to five separate groups (groups 2 to 6) each of 50 to 60 birds.

3. Group 2 was fed on a normal layers’ diet at 23 weeks of age, group 3 at 27 weeks, group 4 at 31 weeks, group 5 at 35 weeks and group 6 at 55 weeks while the control group (group 1) of similar size to groups 2 to 6 was subjected to a normal commercial treatment for laying stock.

4. In all the experimental groups the onset of sexual maturity occurred normally, but only one or two eggs were laid before laying ceased under the influence of the treatment.

5. Laying re‐started when the hens were fed on a normal diet and production rapidly rose to a high level.

6. Groups 1, 2 and 3 differed little in the total number of eggs produced up to 72 weeks of age.

7. In all experimental groups there were fewer very small, small and medium eggs than in the control group.

8. It is suggested that the use of a low‐calcium diet before the onset of lay may have advantages which could be exploited on a commercial scale.     

Urea and aspartic acid supplementation of low‐protein broiler diets1

1. L‐Aspartic acid does not seem useful as a protein surrogate in conventionally formulated low‐protein diets for broiler chicks.

2. Urea as a protein substitute does not enhance the value of conventional broiler diets.

3. Urea does not improve broiler diets that have been supplemented with fish meal or crystalline amino acids to satisfy requirements for all indispensable amino acids.

4. Urea is absorbed into the bloodstream, but is not assimilated into body proteins.     

L‐aspartic acid and urea supplementation of low‐protein layer diets1

1. Urea supplementation of low‐protein (125 g/kg) conventional‐type diets for layers, whether containing fish meal or not, did not appear advantageous.

2. Supplementation of the low‐protein diet with aspartic acid did not affect egg production rate or efficiency.

3. Soyabean meal supplementation of the low‐protein diet increased egg weight significantly whereas aspartic acid did not.     

The effect of sodium sulphate and methionine on the utilisation of non‐protein nitrogen by laying hens

1. The response of layers to adding diammonium citrate (DAC), sodium sulphate or methionine to a basal diet containing 136–3 g protein/kg was determined.

2. Supplementing the diet with DAC equivalent to 25 g protein/kg did not improve egg production, the efficiency of food utilisation, egg weight, nitrogen retention or the apparent absorption of lysine and methionine; increases in food intake and in the concentration of methionine in the serum and liver were observed.

3. Adding sodium sulphate, alone or with DAC, did not affect the variables noted above.

4. Supplementation of the basal diet with methionine increased egg production, egg weight, food intake and the concentrations of lysine in the serum and liver.

5. It is concluded that the supplemental NPN was used only in serum protein synthesis.     

The nitrogen‐sparing effect of methionine in chicks receiving a protein‐free diet supplemented with arginine: Effect of various methionine substituents

1. The nitrogen‐sparing effect of methionine in chicks fed on a protein‐free diet containing arginine was examined in three 10‐d trials. Chicks received either a protein‐free diet, this diet supplemented with arginine and methionine or diets containing arginine in which the methionine was replaced by various methionine‐related compounds.

2. Body‐weight changes, nitrogen retentions and uric acid‐nitrogen excretion indicated that the methyl moiety was unlikely to contribute to nitrogen sparing activity and that cysteine, or possibly glutathione, played an important role. The possible mechanism of the nitrogen‐sparing effect is discussed.     

The effect of feeding low‐protein diets to pullets from hatch to point‐of‐lay and the quantitative restriction of food during the subsequent laying period

Pullets from two commercial breeds were fed on diets of similar energy content but with 19% or 16% crude protein to 8 weeks of age and from 8 to 20 weeks of age on one of three isoenergetic diets containing either 12, 14 or 16% crude protein. At 20 weeks the birds were offered a conventional layers’ diet containing 16% crude protein either ad libitum or on a daily food intake of 100 g for a further 32 weeks.

The results indicate that with certain breeds the dietary protein levels can be lowered to approximately 16% during the o to 8‐week period and to approximately 12% during the 8 to 20‐week period without adversely affecting egg production. However, variations in the laying performance of the different breeds appear to be dependent on the amount of protein fed in the first eight weeks of life. Significant breed effects were observed throughout the experiment and although restricted feeding during the laying period substantially reduced the food intake it also had a detrimental effect on the rate of egg production and on the total weight of eggs produced.     

Metabolisable energy content of rapeseed meal,soyabean meal and white‐flowered peas determined with laying hens and adult cockerels

1. The apparent metabolisable energy (AME) contents of 5 protein‐rich ingredients were determined with laying hens and the true metabolisable energy (TME) with adult cockerels. The test materials consisted of one batch each of winter‐grown high glucosinolate rapeseed meal (HG‐RSM), summer‐grown HG‐RSM, low glucosinolate rapeseed meal (LG‐RSM), soyabean oil meal (SBM) and white‐flowered peas (WFP).

2. In a separate study the endogenous energy losses (EEL) of adult Rhode Island Red (RIR) and adult broiler roosters were measured when given a supply of energy.

3. AME value for RSM tended to be lower for cockerels than for hens, whereas the opposite was noted for SBM and WFP.

4. This study showed that AME of ingredients could be influenced by choice of technique. These differences are accentuated for some ingredients, such as SBM and RSM, although there was no difference in ranking ingredients tested within the AME and TME systems.

5. Assuming that birds are receiving an energy source, the EEL0 per kg metabolic body weight (W0.75) did not differ between adult broiler cockerels and adult Rhode Island Red cockerels.

6. The AME0 values with laying hens for winter HG‐RSM, summer HG‐RSM, LG‐RSM, SBM and WFP were 7.0, 7.6, 8.7, 11.5 and 11.3 kJ/g dry matter. TME0 values with cockerels for the respective ingredients were 8.4, 8.5, 9.5, 12.6 and 13.4 kJ/g dry matter.     

Effects of plastic anti‐pecking devices on food intake and behaviour of laying hens fed on pellets or mash

1. This study investigated effects of plastic anti‐pecking devices on food intake and behaviour to assess their applicability in commercial layer flocks.

2. In experiment 1, 72 individually caged ISA Brown pullets were fitted at 16 weeks of age (point of lay) with either ‘ring’ or ‘bumper’ beak devices or no device (control), half being fed on pellets and half on mash. The devices were held in place by lugs inserted in the nares.

3. There was evidence of discomfort immediately after fitting the devices, but not thereafter. In the first week, the devices reduced food intake, and were removed from 7 (15%) birds that lost weight consistently. Between 16 and 21 weeks, however, there were no significant effects of beak treatment or food form on either total food intake or egg production with the 65 remaining birds.

4. Beak treatment did not affect feeding efficiency (food intake per minute of feeding). The only behaviour affected was pecking at birds in adjacent cages, which was reduced with the ring device.

5. At 21 weeks, the birds were placed together in groups of 4 to 6 in 12 pens, each group consisting of birds from one of the 6 original treatments, and their behaviour was observed in experiment 2 between 21 and 23 weeks.

6. The only effects of beak treatment on behaviour were that pecking at pen walls was increased with the ring device, while pulling and eating feathers from group mates was seen mainly with control birds fed on pellets. Two birds were cannibalised in a control group on pellets.

7. Devices came off 3 (7%) birds in experiment 1 and were replaced, and rings slipped over lower mandibles of 2 (5%) birds in experiment 2 and were corrected.

8. At 23 weeks, beak lengths were increased with ring and bumper treatments, and pecking damage scores were low with all treatments.

9. It is concluded that these devices are not applicable commercially, but further trials would be justified with new improved designs.     

Is it possible to increase the n-3 fatty acid content of eggs without affecting their technological and/or sensorial quality and the laying performance of hens?

1. The aim of this study was to increase the n-3 fatty acid (n-3 FA) content of eggs without affecting their sensorial and/or technological properties or the laying performance of hens. Laying hens from line 477 were divided into 5 groups corresponding to 5 different diets over the laying period: control diet (C) and diets containing extruded linseed with a high level of fibre (ELHF), extruded linseed with a low level of fibre (ELLF), microalgae, or a combination of 75% ELLF and 25% MA (ELLF+MA).

2. Dietary enrichment with n-3 FA had no effect on the laying performance, hen body weight or egg white viscosity. The egg yolks produced by hens fed the diet containing microalgae were redder than egg yolks from the other groups, suggesting the presence of red pigments in the microalgae preparation. However, the colour difference was low and not perceptible to the human eye. Moreover, colour measurement of egg yolks by sensorial analysis panellists using the Roche colour fan did not reveal a diet effect on this parameter.

3. Egg yolk lipid content was not affected by diet. The egg yolk of hens fed on diets containing linseed and/or microalgae had greater n-3 FA content (×2.5 to 2.9 compared to group C). Linseed mainly increased the linolenic acid content (×3.0 to 3.4 compared to group C) and the microalgae increased the LC n-3 FA content (×4.1 compared to group C). Dietary enrichment with n-3 FA had no effect on the sensorial quality of shell cooked eggs except for the “unusual flavour” criterion for which the score was higher for the MA group compared to the other groups and corresponded to a fishy flavour.

     

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.