Effects of dietary cottonseed meal, with and without iron treatment, on laying hens

1. The effects of feeding a screw-press expelled cottonseed meal (CSM) to laying hens at dietary concentrations of up to 300 g/kg, were studied over a 10 week period. 2. The overall performance of hens fed on a 75g CSM/kg diet was not significantly different from controls but a 300g CSM/kg diet, containing 255 mg free gossypol/kg and 87 mg cyclopropenoid fatty acids (CPFA)/kg and giving daily intakes per hen of 26.2 mg free gossypol and 9.0 mg CPFA, significantly reduced food intake (P less than 0.01) and egg production (P less than 0.01). The 150g CSM/kg diet (daily intakes of 14.6 mg free gossypol and 4.8 mg CPFA per hen) did not produce adverse effects initially but egg production was slightly depressed towards the end of the experimental period. 3. Treatment of the CSM with a solution of ferrous sulphate hepta-hydrate for inclusion in a 300g CSM/kg diet (100 mg/kg supplemental dietary iron) further reduced food intake (P less than 0.05) and egg production (P less than 0.05). 4. Storage of eggs at warm temperatures for up to 1 month did not lead to discolourations of any kind in the CSM diet groups, but resulted in yolk mottling, a condition reduced by treatment of the CSM with iron. 5. Storage of eggs at cold temperatures for 3 months resulted in brown yolk discolouration and the initial stages of pink albumen discolouration in the 300g CSM/kg diet group; the brown yolk discolouration was reduced by treatment of the CSM with iron.     

Abnormal characteristics of eggs laid by hens fed with high levels of cottonseed meal

In China, consumers sometimes get special eggs, which are characterized by the pasty, firm, and elastic texture of yolk from hard-boiled eggs and are usually called “rubber eggs” by Chinese customers. Consumers do not like the texture of rubber eggs and often associate the odd texture of the yolk to food safety risks. The objective of this study was to assess the physical and chemical characteristics of these eggs. A total of 200 46-week-old Hy-Line Brown laying hens were divided into 2 groups and were fed for 2 weeks. One group was fed on a corn-soybean meal based diet (BD) and served as control whereas the second group’s diet contained 6% cottonseed meal (CSM), which was in replacement of the SBW. The yolks of hard-cooked eggs of the CSM group had harder and more elastic yolks than those of the control group (P < 0.05). Also, the levels of stearic and myristic acids in the yolk of the CSM group also were increased (P < 0.01), while the myristoleic, pentadecanoic, arachidic, cis-11-eicosenoic and cis-11, 14-eicosadienoic acids and crude protein, fat, phospholipids, chloride, calcium, and iron were decreased (P < 0.05). In conclusion, hens fed a diet that was incorporated with 6% cottonseed meal laid eggs that had unique physical and chemical characteristics and lower nutritional values. These results might help to guide limited incorporation of CSM in laying hen diet, and provide some evidences on the mechanism of the observed physical and chemical changes.     

Effect of feeding clinoptilolite (zeolite) to three strains of laying hens

1. One hundred and twenty 16-week-old, single combed pullets of three strains were fed on a diet containing 160 g protein/kg with or without 50 g clinoptilolite/kg in a trial with 20 hens per treatment. Sterile river sand replaced clinoptilolite in the control diet in order to keep the diets isonergetic. 2. The hens were individually caged in a naturally-ventilated laying house and fed on one of the two diets for ten 28-d periods. 3. No significant dietary effects between treatments were observed with respect to body weight, age at first egg, egg weight, Haugh scores or food intake/hen. 4. Significant dietary effects in favour of clinoptilolite feeding were noticed with the number of eggs laid per hen, shell thickness, efficiency of food utilisation, droppings moisture content and mortality. 5. Significant differences between strains were observed with respect to all measurements taken except food intake/hen d.     

Egg discolouration effects of including screw‐press cottonseed meal in laying hen diets and their prevention

The egg discolouration effects of including a screw‐press cottonseed meal (CSM), containing 68.2 g residual lipid/kg, 290 mg cyclopropenoid fatty acids (CPFA)/kg and 1226 mg free gossypol/kg, in laying hen diets at 300 g/kg were examined.

2. Discolouration prevention methods included treating the meal with ferrous sulphate heptahydrate (FSH), in solution or as crystals, at a 4:1 weight ratio of iron to free gossypol (experiment 1), and reducing its residual lipid (CSL) content to 4.2 g/kg by hexane extraction (experiment 2).

3. In freshly laid eggs, no discolouration was observed when hens were fed a CSM‐based diet containing 250 mg free gossypol/kg and 87 mg CPFA/kg in experiment 1, but slightly brown yolks were produced in experiment 2.

4. Storage of the eggs at 22°C led to yolk mottling, an effect believed to be the initial stages of the brown yolk discolouration.

5. Storage of the eggs at 5°C resulted in enhancement of the brown yolk discolouration, apricot discolouration on surfaces of most yolks and pink albumen discolouration. These effects were prevented when the CSM was extracted with hexane. Apricot yolk and pink albumen discolourations were also produced when hens were fed a non‐CSM diet containing crude CSL at 20.5 g/kg.

6. Dietary CSL increased egg fat saturation, altering the ratios of stearic to oleic, palmitic to palmitoleic and heptadecanoic to hepta‐decenoic fatty acids.

7. Treatment of CSM with FSH reduced the slight brown yolk discolouration in fresh eggs (experiment 2) and the yolk mottling in warm‐stored eggs. Both in solution and as crystals, FSH prevented the enhancement of brown yolk discolouration in cold‐stored eggs, leaving most eggs with apricot yolk and pink albumen discolourations.

8. Treatment of CSM and CSL with FSH reduced the CPFA‐related effects on yolk fat saturation, and the colour and pH changes in cold‐stored eggs.

9. Exposure of yolks to ammonia vapour provided a useful test to predict the development of the gossypol‐related brown discolouration in stored eggs.     

Effects on dietary phosphorus of treating cottonseed meal with crystalline ferrous sulphate for the prevention of brown yolk discolouration

1. Two experiments were carried out to examine whether the adverse effects on laying hen performance of treating cottonseed meal (GSM) with crystalline ferrous sulphate heptahydrate (FSH) to prevent brown yolk discolouration, was a consequence of iron reducing the availability of dietary phosphorus. Two batches of CSM, with different free gossypol and cyclopropenoid fatty acid contents, were treated with FSH at a 4:1 weight ratio of iron to free gossypol, and incorporated into diets at 300 g/kg with or without supplementation with sodium dihydrogen phosphate (SHP), and fed to hens.

2. FSH treatment of CSM reduced food intake and egg production. Although performance was improved by supplementing the FSH‐treated CSM diets with SHP, it was still poorer than that achieved by hens fed a non‐CSM control diet.

3. Brown yolk discolouration was prevented by treatment of CSM with FSH. Additional phosphorus did not produce any significant effects on brown colour development in yolks, indicating that the bioavailable gossypol content of the diets had not been altered; however, chemical analyses showed an apparent increase in the free gossypol content of the diets with the inclusion of SHP, suggesting that the assay gives misleading results.     

Effect of feeding clinoptilolite (zeolite) on the performance of three strains of laying hens

1. One hundred and twenty 16‐week‐old single combed pullets of three strains were fed on a diet containing 135 g protein/kg with or without 50 g clinoptilolite/kg in a trial with 20 hens per treatment. Sterile river sand replaced clinoptilolite in the control diet in order to keep the diets isoenergetic. The hens were individually caged in a naturally ventilated laying house and fed one of the two diets for ten 28‐d periods.

2. Significant dietary effects of feeding clinoptilolite were observed with number of eggs laid per hen, shell thickness, efficiency of food utilisation and droppings moisture content. No significant dietary effects between treatments were observed with body weight, age at first egg, egg weight, Haugh units, food intake/hen and rate of amino acid absorption of radioactive lysine and methionine into the bloodstream. Significant differences between strains were observed with regard to all parameters except food intake/hen. There were no significant strain × clinoptilolite interactions.     

Effect of expanded cottonseed meal on laying performance,egg quality,concentrations of free gossypol in tissue,serum and egg of laying hens

Three hundred and sixty Hy‐Line Brown hens, 40 week of age, were allocated to five treatments, each of which included four replicates of 18 hens. After an expanded process of cottonseed meal (CSM), free gossypol content in CSM was decreased from 1.24 to 0.40 g/kg. The dietary treatments were corn‐soybean meal based diets including 6% CSM and 6%, 8% and 10% expanded cottonseed meal (ECSM). Hens fed 8% ECSM had higher (P < 0.05) laying rate and average egg weight than those fed 6% CSM. The albumen height and Haugh unit in the control group, 6% and 8% ECSM groups were superior (P < 0.05) to other treatments. Hens fed 6% CSM resulted in severe (P < 0.05) egg yolk discoloration. Free gossypol (FG) concentrations in yolk and albumen and tissues of the 6% CSM group were greater (P < 0.05) than those in any ECSM treatments. Hens fed 6% CSM and 10% ECSM had the highest (P < 0.05) FG concentrations in the liver compared with those in the kidney and muscle, and higher (P < 0.05) FG residues in yolk than those in albumen. In conclusion, FG in CSM can be reduced by 68% through an expanded process and ECSM can be available in laying hens at up to 10% of the total diet and an appropriate replacement of soybean meal with ECSM may improve performance in laying hens.     

Dietary levels of chia: influence on hen weight,egg production and sensory quality,for two strains of hens

1. Laying hens, 225 white and 225 brown, were fed for 90 d to compare a control diet with diets containing 70, 140, 210 and 280 g/kg chia (Salvia hispanica L.) seed. 2. Hen weight was not significantly affected by diet; however, manure production was less for the hens fed on chia. 3. Egg weight and production, yolk weight, and yolk percentage were determined at d 0, 30, 43, 58, 72 and 90. 4. A sensory evaluation was conducted on eggs produced during the last week of the trial. 5. No significant differences in egg production were found among treatments for the brown hens. 6. With the 280 g/kg chia diet, the white hens produced fewer and lighter eggs than did the hens fed on the control diet. 7. No significant differences were detected in yolk weight until d 90. 8. On this date the yolks produced by the white hens fed on the 70 g/kg chia diet were significantly lighter in weight, whereas the brown hens produced significantly heavier yolks, compared with the hens fed on the control diet. 9. Yolk weight as a percentage of egg weight was lower for white hens throughout the trial except on d 58 with the 140 g/kg chia diet. Significant differences, however, were detected only with the 70 g/ kg chia diet on d 90 and with the 210 g/kg chia diet on d 58, 72 and 90. 10. No significant differences in taste preference or flavour were found among any of the chia treatments and the control.     

Impacts of dried whole eggs on productive performance, quality of fresh and stored eggs, reproductive organs and lipid metabolism of laying hens

1. Rejected eggs were processed by freezing, freezing and boiling, or autoclaving, dried at 55°C, and the chemical and amino-acid analysis and microbiological properties of the dried whole eggs (DWE) determined. The processed DWE was included in a laying-hen mash diet at 50 or 100 g/kg, mainly to replace soybean meal and maize, in a factorial design of 3×2 and fed to hens between 25 and 41 weeks of age. In addition, a control diet without DWE was used to create a total of 7 treatments; each having 5 replicates of 5 hens. 2. Hens fed the diet containing 50-g/kg frozen and boiled DWE and 100-g/kg frozen DWE laid the largest egg size, while hens fed the 50-g/kg frozen and boiled or autoclaved DWE diets yielded the highest egg mass and best feed conversion efficiency. 3. Hens fed the 50-g/kg frozen DWE laid eggs with a higher yolk indices, Haugh unit scores, and eggshell thickness and maintained higher Haugh unit scores during egg storage. 4. Yolk cholesterol significantly decreased in eggs from groups fed either the 50-g/kg frozen or autoclaved DWE diet, with freezing having the stronger effect. 6. In conclusion, 50-g/kg autoclaved DWE diets fed to laying hens between 25 and 41 weeks of age had no adverse effects on production, egg quality or reproductive organs, but decreased yolk cholesterol, and thus could be beneficially included in laying-hen diets.     

Effect of enzyme addition to wheat-, barley- and rye-based diets on nutrient digestibility and performance of laying hens

1. Laying hen performance, egg quality, intestinal viscosity and nutrient apparent digestibility were evaluated with respect to the main cereal used in the diet and dosage rate of a fungal beta-glucanase/xylanase enzyme complex. 2. Twelve diets were arranged factorially, with three soluble fibre cereals (SFC); 500 g/kg of wheat or barley or 350 g/kg of rye, and 4 enzyme concentrations (0, 250, 1250 and 2500 mg/kg). An additional control diet based on maize was also included. 3. The use of SFC in the diet instead of maize did not affect egg production or food efficiency, but hens fed on SFC diets exhibited a higher incidence of dirty eggs than hens fed on the maize diet (8-6 vs 4.6%; P<0.01). 4. Laying hens fed on enzyme-supplemented diets produced more eggs (2.1%; P<0.05) and had better food efficiency per dozen eggs (2.5%; P<005) than hens fed on non-supplemented diets. An excess of enzymes in the diet (10 times the recommended dose) did not produce any deleterious effect on laying hen productivity. 5. Enzyme supplementation (ES) reduced intestinal viscosity (P<0.001) and the incidence of dirty eggs (P<0.01). The reduction in viscosity was more pronounced in barley than in wheat or rye diets (P<0.05). 6. Apparent nutrient digestibility in SFC diets was higher with ES, including dry matter (3.1%; P=0.08), fat (4.4%; P<0.001), non-starch polysaccharides (83.3%; P<0.01) and AMEn (2.5%, P<0.01). 7. It is concluded that substitution of maize by SFC is facilitated by ES, especially with respect to egg production, food conversion efficiency and egg shell cleanliness. An excess of enzymes did not produce any deleterious effect on nutrient digestibility or performance of laying hens.     

Effects on egg production of including high residual lipid copra meal in laying hen diets

1. The effects on egg production of including copra meals of 220.9 (Copra‐1) and 205.0 (Copra‐2) g residual lipids/kg, in laying hen diets at up to 400 g/kg, were examined in two feeding trials. In a separate experiment, the dry matter retention and ME of a 400 g Copra‐2/kg diet were determined between 6 to 9, 9 to 12 and 12 to 15 d of feeding.

2. Food intakes, egg output and efficiencies of food utilisation (g eggs/g food) of hens fed on Copra‐1 at 100 and 200 g/kg diet were not significantly different from controls; while food intakes at 400 g Copra‐1/kg diet were similar to controls, egg output (6.0% lower), efficiency of food utilisation and body weights of hens were significantly reduced. Hens fed Copra‐2 at 400 g/kg diet had 5.0 and 6.9% lower food intakes and egg output, respectively, and lost body weight compared to controls; however, egg output increased to that of the control group by the 11th week of feeding.

3. Initially, dry matter retention of the 400 g Copra‐2/kg diet was similar to, and ME slightly higher than the control diet; however, both were reduced significantly in the second and third collection periods. The water content of excreta from hens fed on 400 g Copra‐2/kg diet was significantly higher than that from controls.

4. Complete replacement of dietary maize, mainly with copra (experiment 1) led to an increase in pale yolks, with the 400 g Copra‐1/kg diet producing cream‐coloured yolks. Inclusion of maize at 180.6 g/kg of the 400 g Copra‐2/kg diet (experiment 2) resulted in eggs with slightly golden‐yellow yolks.     

Effects on health and blood plasma parameters of laying hens by pure nivalenol in the diet

The effects of trichothecene nivalenol (NIV) on the health and production of laying hens were determined in a feeding study. White Leghorn hens, 55 weeks old, were fed diets containing 0, 1, 3 and 5 mg NIV/kg during 50 days. Feed intake was reduced by NIV, but there were no effects on body weight, egg production and egg quality. Traces of unaltered NIV were found in liver and bile. Alkaline phosphatase in the blood plasma increased in the hens fed 0, 1 and 3 mg NIV/kg diet but decreased in the birds fed 5 mg NIV/kg feed. Total protein and glucose were slightly reduced in hens fed 5 mg NIV/kg diet. Pathological examination revealed that 40-75% of hens fed NIV (3 and 5 mg/kg) supplemented diet showed gizzard lesions, haemorrhages in the duodenum and swollen cloaca and oviducts with immature eggs while certain birds in the 1 mg NIV group showed light and fragile livers. NIV and the metabolite de-epoxy-NIV in faeces were found to constitute up to 10% of ingested NIV.     

Re-evaluation of calcium and phosphorus requirements in aged laying hens

1. A series of 5 trials was conducted with 401- to 650-d-old Lohmann, Yafa (local breed with brown eggshells) and Yarkon (local breed with white eggshells) hens fed for 56 to 84 d with diets containing 25 to 50 g/kg calcium (Ca) and 4.5 to 7.6 g/kg phosphorus (P). 2. Increasing dietary Ca from 24-25 to 36-40 g/kg improved egg production, shell weight (SW) and shell thickness (ST), and decreased mortality. 3. Increasing dietary Ca to 48 to 50 g/kg did not affect egg production but increased SW and/or ST. In one out of the 4 trials, this effect was not significant, most likely because of the high shell quality of the eggs from the Yafa hens used for this trial. 4. Dietary P content of 4.5 g/kg (1.0 g/kg added inorganic P) appears to be sufficient for maintaining egg production and shell quality in aged laying hen given 36 to 40 g/kg Ca. 5. Increasing dietary Ca above 40 g/kg may require a higher dietary P content.     

Self-selection of dietary protein and energy by turkey breeder hens

1. An experiment was conducted to determine the effects of self-selection of dietary protein and energy by turkey hens on reproductive performance in a warm environment. 2. Dietary self-selection had no significant effect on egg production, egg weight, or body weight of turkey hens. 3. Fertility and hatchability of eggs produced by self-selecting hens were significantly reduced compared to eggs from control hens fed on a complete diet. 4. Protein intake was significantly reduced among self-selecting hens when compared to control hens fed on a complete diet (P less than or equal to 0.001). 5. Food and energy intake decreased as the ambient temperature increased. Nevertheless, protein intake of self-selecting hens increased over the course of egg production despite decreasing food intake. Therefore, self-selecting hens preferred a diet with a greater protein content (g protein/kg diet) in the last 10 weeks of egg production than during the first 10 weeks of egg production.     

Effects of dietary borate and aluminate on riboflavin metabolism in the breeding hen

Breeding hens were used to investigate the effects of aluminate and borate ingestion on riboflavin metabolism. Groups of six hens were fed on either a control diet, or the control diet plus 15 g kg-1 of either sodium metaborate or sodium meta-aluminate. All diets contained 6 mg kg-1 riboflavin. Daily egg production per hen in the borate group had mean values of 0.71, 0.21 and 0.02 for the three weeks of the study. The values were 0.91, 0.91, 0.86 and 0.86, 0.74, 0.89 for the control and aluminate groups, respectively. Fertility (fertile eggs per 100 set) and hatchability (live chicks per 100 fertile eggs) were both nil in the borate-treated hens, compared with 57 and 95 and 59 and 100 for the control and aluminate-treated hens, respectively. Fluorimetric analysis of blood plasma, egg yolk and albumen showed that the riboflavin contents of all tissues were greatly reduced in the borate-treated hens. Borate ingestion can therefore induce a severe riboflavin deficiency in the hen, but aluminium, a more universal contaminant of food or water, did not impair riboflavin metabolism when fed as aluminate.     

Biotin requirements of broiler breeders fed diets of different protein content and effect of insufficient biotin on the viability of progeny

Production of eggs or normal chicks was depressed when practical diets containing 168 g or 137 g of crude protein (CP)/kg were not supplemented with synthetic biotin. Overall egg production and hatchability of fertile eggs was significantly (P less than 0.05) higher with the diets containing 137 g CP/kg. Biotin requirement was higher with the diet containing 168 g CP/kg and was estimated to be about 100 micrograms of available biotin/kg, equivalent to a daily intake of 16 micrograms for food-restricted hens. Biotin concentrations in egg yolk and chick plasma were related to maternal intake and increased with maternal age. The minimum yolk biotin concentration indicative of adequate maternal status was about 550 micrograms/g. Chicks from young hens fed insufficient biotin had the poorest biotin status at hatching and their growth potential and viability were reduced.     

Strain Response of Laying Hens to Varying Dietary Energy Levels With and Without Avizyme Supplementation

The response of 4 strains of laying hens fed diets varying in ME with and without Avizyme 1500 (AVI) supplementation was evaluated in a factorial arrangement study. The strains of laying hens (Hy-Line W-36, Hy-Line Brown, Babcock B300, and Shaver White) were fed 3 diets: moderate ME (2,900 kcal/kg), low ME (2,810 kcal/kg), and low ME with AVI for 28 wk commencing at 22 wk of age. No significant effects of diet, strain, or their interaction on feed intake and BW change were observed. Lack of an effect on feed intake was surprising given the different levels of ME. It is hypothesized that the reduced dietary ME was not low enough to elicit a response. Of course, dietary level of ME did change caloric intake among hens, with hens fed moderate ME consuming more calories than those fed low ME with or without AVI. There was an interesting dietary ME × strain interaction effect on egg production (EP). Babcock B300 hens fed moderate ME and low ME with AVI had greater EP compared with the B300 hens fed low ME, whereas the Shaver White hens had a greater EP when fed a low-ME diet compared with feeding a moderate-ME diet or low-ME diet with AVI. Egg weight and egg mass were significantly affected by strain but not by diet ME. Hy-Line Brown and Babcock B300 hens laid eggs with greater weight and mass in contrast to Hy-Line W-36 or Shaver White. Hy-Line Brown eggs were the largest, whereas Shaver White had greatest egg-specific gravity. Strain significantly affected proportions of albumen vs. yolk in the egg. Across all strains, Hy-Line Brown had more albumen percentage, whereas Hy-Line W-36 had higher wet yolk and yolk solids percentages. The low-ME level fed to laying hens may have been too high to evoke an enzyme response to improve energy utilization by birds. This is important, because to obtain an economic benefit, producers would need to know the proper ME level to feed with the supplemental enzymes.     

The laying performance of two strains of hens offered diets containing dried poultry manure during the laying stage

1. Light‐weight (Babcock B300) and medium‐weight (Warren‐SSL) hens were offered diets, containing 0, 100 or 200 g dried poultry manure (DPM) and 11.49, 11.12 or 10.83 MJ metabolisable energy/kg respectively, between 18 and 70 weeks of age. The true protein, metabolisable energy, calcium and phosphorus contents of the DPM, from caged layer hens, were used in the diet formulation.

2. The hen‐housed laying performance of hens offered the DPM‐containing diets was significantly better for number of eggs laid and total egg mass produced but the performance of the control groups was lower than would normally be expected of those stocks. The reason for the lower rate of lay and higher mortality of hens fed on the control diet was not identified. The amount of food consumed increased as the energy content of the diet decreased and the efficiency of food conversion (EFC) of the lightweight strain was reduced; there was no significant effect on the EFC of the medium‐weight hens.

3. The inclusion of DPM in the diets had no effect on albumen quality or on the incidence of hair‐cracked, cracked or broken eggs. However, with both strains of hens, shell weight and shell thickness were poorer when 100 or 200 g DPM/kg diets were fed.     

Effects of an experimental phytase on performance, egg quality, tibia ash content and phosphorus bioavailability in laying hens fed on maize- or barley-based diets

A 24-week performance trial was conducted to evaluate the efficacy of an experimental phytase on performance, egg quality, tibia ash content and phosphorus excretion in laying hens fed on either a maize- or a barley-based diet. At the end of the trial, an ileal absorption assay was conducted in order to determine the influence of phytase supplementation on the apparent absorption of calcium and total phosphorus (P). Each experimental diet was formulated either as a positive control containing 3.2 g/kg non-phytate phosphorus (NPP), with the addition of dicalcium phosphate (DCP), or as a low P one, without DCP addition. Both low P diets (containing 1.3 or 1.1 g/kg NPP) were supplemented with microbial phytase at 0, 150, 300 and 450 U/kg. The birds were housed in cages, allocating two hens per cage as the experimental unit. Each of 10 dietary treatments was assigned to 16 replicates. Low dietary NPP (below 1.3 g/kg) was not able to support optimum performance of hens during the laying cycle (from 22 to 46 weeks of age), either in maize or barley diets. Rate of lay, daily egg mass output, feed consumption, tibia ash percentage and weight gain were reduced in hens fed low NPP diets. The adverse effects of a low P diet were more severe in hens on a maize diet than in those on a barley diet. Low dietary NPP reduced egg production, weight gain, feed consumption and tibia ash content and microbial phytase supplementation improved these parameters. Hens given low NPP diets supplemented with phytase performed as well as the hens on positive control diets containing 3.2 g/kg of NPP. A 49% reduction of excreta P content was achieved by feeding hens on low NPP diets supplemented with phytase, without compromising performance. Phytase addition to low NPP diets increased total phosphorus absorption at the ileal level, from 0.25 to 0.51 in the maize diet and from 0.34 to 0.58 in the barley diet. Phosphorus absorption increased linearly with increasing levels of dietary phytase. Mean phosphorus absorption was higher in barley diets than in maize diets (0.49 vs 0.39).     

The effect of supplementing layer diets with shark cartilage or chitosan on egg components and yolk lipids

1. An experiment was designed to evaluate the effects of the addition of shark cartilage (SC) or chitosan (CH) to layer diets on egg component weights, yolk lipids and hen plasma lipids. 2. Hy-Line laying hens (80) were used during a 56 d feeding trial. Treatments were: basal diet (BD), BD + 20 g/kg SC, BD + 30 g/kg SC, BD + 20 g/kg CH and BD + 30 g/kg CH. Eggs were analysed on d 14, 28, 42 and 56. 3. Egg weight and egg component weights were not affected by these treatments throughout the experimental period. 4. After 14d of experimental feeding, cholesterol levels were higher in eggs from birds given BD + 20 g/kg CH and BD + 30 g/kg CH than in those from birds given BD. 5. Furthermore, eggs from hens given BD + 20 g/kg SC or BD + 20 g/kg CH were higher in palmitic and stearic acids and lower in oleic acid than those from birds fed on BD. After 56 d feeding, however, palmitic and stearic acid contents in eggs from hens given any of the supplemented diets were lower than in those from hens given BD, and oleic acid in eggs from hens given BD + 20 g/kg SC, BD + 30 g/kg SC and BD + 30 g/kg CH was higher than in those from birds fed on BD. 6. Plasma cholesterol and triacylglycerol levels were not significantly affected by dietary treatment. 7. Shark cartilage or chitosan at up to 30 g/kg in layer diets did not affect egg component weights (yolk, white and shell) and total lipid contents. During the period from 42 to 56d of experimental feeding, diets containing up to 30 g/kg chitosan reduced egg yolk contents of cholesterol, palmitic and stearic acids and increased the content of oleic acid.