IMPACT OF REDUCED PROTEIN DIETS BASED ON IDEAL AMINO ACID PROFILE ON PERFORMANCE AND EGG QUALITY TRAITS OF LAYING HENS

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1 IMPACT OF REDUCED PROTEIN DIETS BASED ON IDEAL AMINO ACID PROFILE ON PERFORMANCE AND EGG QUALITY TRAITS OF LAYING HENS Shaimaa R. Anwar 1, Maha M. Hady 2, R. A. Elbanna 3, T. M. Melegy 4 1,2,3,4 Department of Nutrition and Clinical Nutrition, Faculty of Veterinary Medicine, Cairo University, GIZA, EGYPT ABSTRACT The aim of the current experimental trial is to investigate the effects of reduced crude protein amino acid balanced diets (16% and 14%) feeding with constant lysine - limiting amino acids ratio on performance (weight gain, egg production % and egg mass), some selected egg quality parameters as well economic efficiency of both diets in Bovans - Brown laying hens compared with commercially used diet (18% CP). A total of 480 commercial laying hens (20 week age) were divided into 3 groups (CG18, G16, and G14) each of 160 birds.reduced CP diets were supplemented by crystalline amino acids where the ratio of limiting amino acids to lysine was kept constant in the 3 dietary treatments. Performance parameters, egg quality parameters were recorded and economic efficiency was calculated. It was noticed that performance parameters in G16 and G14 were lower than the commercially used diet. On the contrary, almost of egg quality parameters in G16 and G 14 were not affected. From the cost efficacy point of view, both diets (G16 and G14) were more cost-effective than the commercial used diet. In conclusion, reduced crude protein amino acid balanced diets might be used as a reliable tool in egg production industry. Key Words: Amino Acid, Egg Quality, Laying Hens, Performance Parameters, Reduced CP I. INTRODUCTION Egg production is of out-most source of good quality protein for human being. Nutrition of layers is sparingly critical as higher or suboptimal concentration of nutrients shall adversely have an influence on both production and immune status [1]. As the prices of feed ingredients has been going up during last decades several concepts have been adopted to minimize feed cost, maintain hens performance as well as reducing environmental pollution [2]. Recent technological advances in amino acids manufacture as well as the high demand to decrease environmental pollution has emphasized the concept of fractional replacement of integral dietary CP with crystalline amino acids in layers nutrition [3]. Synthetic amino acids may be added to low crude protein diets to overcome the decreased level of limiting amino acids [4]. Multifactor hinders the utilization of amino acids determined under experimental conditions as a reference to express requirements of laying hens under field conditions. Therefore, ideal amino acid profile shall be used a reliable tool to express amino acid requirements in poultry nutrition. The ideal amino acid profile is defined as the ideal pattern of amino acids (expressed as % to lysine) that is required for maximum growth, production as well as nitrogen retention [5]. 220 P a g e

2 Several studies have examined the effects of using reduced CP amino acid balanced diet in laying hen nutrition. In a study, where 2 levels of dietary CP were used (13.5% vs 17%) layer performance was kept well on low protein diet when essential amino acids were adequately supplemented [6]. Similarly, it was found that during short term feeding (5- weeks ), egg production as well as FCR were not changed in laying hens fed as low as 14% CP diet compared with 17% CP- control group [7,8]. On the other hand, [8] concluded that short term feeding of low CP diet supplemented with amino acids to laying hens was able to maintain normal performance. On the contrary, the same authors suggested that feeding of low CP diet for long time possibly will influence performance as a result of continuous decrease in the level of stored body protein in laying hens. Additionally, dietary protein reduction from 18.9 to 17 g/hen per day (20 to 43 week of age) shall minimize N excretion while; maintaining egg production [9]. Therefore, the main objective of the current study is to test the hypothesis that the practice of reduced CP (16% and 14%) - amino acid balanced corn- soybean based diet with constant ratio among lysine and other limiting amino acids, shall maintain efficient Bovans - Brown laying hens performance as well as egg quality traits as to offer valuable data to set a reference for egg production industry. II. MATERIALS AND METHODS 2.1 Experimental Birds and Management The experimental trial was carried out at Neuvo-chick farm at Cairo-Ismailia road from the period of weeks of age. A total of 480 commercial laying hens (Bovans - Brown, 20 week age) were kept in battery cages of standard size. A photo- regimen was changed in accordance to age of birds up to 16 h light. Bird s vaccination and management during rearing period were carried out according to routine recommended program for the breed. Bird s management and care were done in agreement with the standards of the animal care ethical committee of Faculty of Veterinary Medicine, Cairo University. Feed was offered to laying hens as mash and each bird received 120 g feed / day. Water was offered on ad-libitum bases using automatic drinkers. 2.2 Experimental Diets and Design Birds were allocated into 3 groups each group of 8 replicates / treatment (20 hens / replicate). Birds were fed commercially formulated isocaloric- hetero-nitrogenous corn- soybean based diets to meet their requirements. Ingredients% and calculated analysis, dietary amino acid levels and % in different experimental treatments in to NRC requirement are shown in Table (1) and (2), respectively. The 3 dietary treatments were: 1- control diet (CG18): containing 18% CP, 2- reduced CP diet containing 16% CP (G16) and 3- reduced CP diet containing 14% CP (G14).Amino acids profile of control and experimental groups were adjusted based on standard ileal digestible amino acids (SID) where the ratios of lysine to other limiting amino acids were kept almost constant in the 3 dietary treatments. Ideal amino acid profile of experimental dietary treatments to lysine is demonstrated in Table (3). 2.3 Performance Parameters All experimental birds were weighted at the commencement of the experimental trial and at biweekly interval up to the end of 5 months experimental period. Hen-day egg production for each treatment was recorded daily and egg production percent was calculated by dividing number of laid eggs over total number of birds. Average 221 P a g e

3 egg weight (g) for each treatment was biweekly recorded, and egg mass (g/hens) was calculated by multiplying egg weight by egg production %. 2.4 Egg Quality Parameters Eggs were biweekly collected from each treatment (15 egg/ treatment) and weights were recorded. Examination of egg quality traits were carried out according to [10]. Egg volume was measured by water displacement in a cylinder. Egg specific gravity was calculated by dividing egg weight over egg volume. Each egg was then broken into a petri dish where yolk height and albumin height was measured using tripod micrometer. Yolk and albumin diameter were measured using sliding steel caliper. Yolk index was calculated by dividing yolk height over yolk diameter while; albumin index was calculated by dividing albumin height over albumin diameter. Yolk was separated from albumin using plastic egg separator and rubber spatula and paper towel was used to get rid of excess albumin and then yolk weight was measured using sensitive balance. Egg shell was washed left to dry and then egg shell weight was measured using sensitive balance. Albumin weight was calculated by subtracting yolk weight and egg shell weight from egg weight. Egg shell thicknesses was measured using micrometer at three different locations (middle, broad and narrow ends) and mean value was recorded to the nearest 0.01mm. Haugh unit score was calculated using the formula: Haugh unit = 100 log (H W 0.37 ) where H is the albumen height in millimeters and W is egg weight in grams. 2.5 Economic Efficiency Study Economic efficiency study was done by calculating 1- Total income: = Egg number/hen price of one egg. 2- Net revenue = total income feed cost. 3- Economic efficiency (%) = net revenue (total income feed cost) / feed cost. 4- Relative economic efficiency (%) = (EE treatment / EE control (18%CP)) Statistical Analysis Statistical analysis of data was carried out using Minitab 17.0 (Minitab, Inc, USA) statistical program. All data were analyzed using analysis of variance (ANOVA) and the difference among the means was tested using Duncan s multiple range test [11]. Significance was considered at P 0.05 levels. III. RESULTS Results of overall Performance Parameters (weight gain, egg production % and egg mass) of laying hens during experimental trial are shown in table (4).It was observed that average weight gain (g) was higher in CG18 than G16% and G14, respectively (510 vs 500, 479). Doing the same way, both egg production % as well as egg mass (g/hens) were higher in CG18 fed group compared with G16 and G14, respectively (76.68 vs 75.62, 74.19) and (47.1 vs 45.76, 44.2). Results concerning over all egg quality Parameters of laying hens during experimental trial are presented in table (5).Results revealed that there were no significant differences among the three different dietary treatments in egg weight (g), albumin height (mm), yolk diameter (mm), albumin weight (g), shell thickness (mm) and haugh unit score. However, a significant increase (P 0.05) in yolk height (mm) was observed in G14 compared with CG18 and G16 respectively (17.69 vs 16.86, 16.72). 222 P a g e

4 On the other hand, albumin diameter (mm) was significantly higher (P 0.05) in G16 compared with CG18 and G14 (30.74 vs 28.5, 27.7). Regarding yolk weight (g), no statistical difference was found between CG18 and G16 but there was a significant increase (P 0.05) in yolk weight in CG18% compared with G14 (16.1 vs 15.11). On the contrary, egg shell weight (g) was significantly higher in G16 and G14 fed groups compared with 18% - fed group (7.01, 7.05, vs 6.7). Yolk index was significantly higher (P 0.05) in birds fed G14 compared with G16 (0.41 vs 0.39). Meanwhile, no significant difference was noticed between CG18 and G16, G14 respectively (0.4 vs 0.39, 0.41). Meanwhile, there was a significant increase in albumin weight (g) in G14 compared with CG18 and G16 (0.37 vs 0.36, 0.34). Results concerning feed efficiency study are shown in Table (6). It can be noticed that the highest feed cost/hen (L.E) is in CG18 diet followed by G14 and then G16 (43.42, 42.56, and 41.69) total income was in CG18 followed by G16 and then G14. On the other hand, the highest net revenue economic efficiency as well as relative economic efficiency are found G16, followed by G14 and then CG18 respectively, (26.13, 25.08, 24.54), (0.63, 0.59, 0.57) and (110.53, , 100). IV. DISCUSSION This aim of this work was to explain the effects of current practice of reduced crude protein diets prepared using ideal amino acid profile on laying hens' performance parameters, egg quality traits as well as economic efficiency. Results of performance parameters revealed that a reduction in performance parameters (weight gain, egg production % as well as egg mass) was noticed in birds fed reduced CP diets (16% and 14%) compared with those fed 18% CP. These findings coincides with the findings of [12] and [3] who also noticed a decrease in performance parameters in birds fed reduced CP diets, but with the usage of lower protein levels (13%, 14%) while the amount of consumed amino acids was adequate. Results also show that 2% increase in the level of dietary protein results in an increase in egg production % to approximately 1.4%. Similarly, it was reported that egg production % increased (2.56%) by increasing dietary CP intake by 2% [13]. On the contrary, [14] concluded that egg mass was not changed in birds fed reduced CP amino acid supplemented diet (13% CP) compared with birds fed diet containing 17% CP. Additionally, [15] concluded that the reason of decreased performance of laying hens fed reduced CP amino acid supplemented diet is not understood and can t be attributed to the reduction of protein intake as amino acid requirements are met. Egg mass is influenced by 2 factors as described by (8) who mentioned that egg mass is depends on egg production % as well as egg weight but as in our present study, there were no changes in egg weight in the three dietary treatments so the reason of egg mass reduction is attributable to the decrease in egg production % in reduced CP fed groups (16% and 14%). Meanwhile, [16]suggested that reduction of laying hens performance when fed reduced CP- amino acid supplemented diets may be as a result of inadequate supply of certain essential amino acids such as valine, isoleucine and tryptophan. Results of egg quality traits (Table 5) show that in the three dietary treatments, as laying hens advance in age, a simultaneous increase in egg weight as well as yolk weight is observed. In addition to that there were no significant differences in egg weight, albumin height, yolk diameter, albumin weight, shell thickness and haugh unit score. Results of egg weight are in agreement with the findings of [8] and [17] who reported that egg weight was not affected in birds fed reduced CP diets. Moreover, [8] suggested that similar egg weight among different dietary treatments is a consequence of proper dietary supplementation 223 P a g e

5 of reduced CP diets with essential amino acids which could meet laying hen s requirements. In addition to that, [9] suggested that a positive relationship between albumin weight and egg weight is found and as in our current study there were no significant differences among egg weights in different dietary treatments so albumin weight was similar. In the present study shell thickness was not affected in reduced CP fed groups (16% and 14%) compared with 18% CP fed group. These outcomes are similar to the findings obtained by [9] who observed that reduction of dietary CP% didn t influence egg shell quality. This could indicate that reduced CP diets used in the experimental trial contained enough sulfur containing amino that is essential for increasing calcium binding ability at egg shell protein matrix and consequently improving egg shell thickness and quality as described by [18]. In addition to that, haugh unit score was not decreased in reduced CP fed group. These results coincides with the findings of [9] who concluded that haugh unit score was not influenced by feeding laying hens (20-43 weeks of age) reduced CP diets supplemented with amino acids with TSAA: lysine ratios 0.97, 0.85, and 0.82 respectively. On the contrary, [15] reported that the highest haugh unit score were obtained at a level of 17% dietary CP. Results of economic efficiency study show that reduced CP amino acid supplemented diets ( 16% and 14%) were more economically feasible than 18% dietary CP. These results are in agreement with the findings of [2] who suggested that reduced CP- amino acid supplemented diets were more economic effective than normal CP levels. They also added that, synthetic amino acid are widely spread and with reasonable prices that permits their usage in reduced CP diets without adding extra costs. V. TABLES Table 1: Ingredients % and Calculated Analysis of Different Experimental Dietary Treatments Ingredient (%) CG18 G16 G14 Yellow corn Soybean meal 47% Vegetable oil Sodium bicarbonate NaCl Monocalcium phosphate Limestone Premix * Calculated analysis Metabolizable energy (Kcal/Kg) Crude Protein (%) Crude Fat (%) Crude Fibre (%) Linoleic acid (%) Cl (%) K (%) Calcium (%) P a g e

6 Phosphorus (total) (%) P. Available (%) Sodium (%) *LayMix-Rannim each 1 kg contains: Vit. A: 25 MIU, Vit. B 1 : 2 g, Vit. B 2 : 10 g, Calcium D Pantothenate: 16 g,vit. B 6 : 3 gvit. B 12 : g, Vit. D: 35 MIU, Vit. E: 16 g, Vit. K: 2 g, Niacin 24 g, Folic acid: 2 g, Organic BaseQ.S. Table 2: Dietary Amino Acid Levels and % in Different Experimental Treatments in Relation to NRC Requirement Group CP% Supplemented acid 1 Amino Level of EAA in the diet % to NRC 2 requirement EAA % EAA % Met Met Cys CG18 18 Met 0.16 Lys Thr Trp Val Met 0.21 Met G16 16 G14 14 Lys 0.06 Met + Cys Lys Thr 0.04 Thr Trp Trp Val Met 0.26 Met Met + Cys Lys 0.21 Lys Thr 0.10 Thr Trp 0.07 Trp Val 0.09 Val Amino acids supplied by Evonik Industries AG. 2 levels of supplemented amino acids as a percentage of the NRC (1994) requirement of laying hens fed on 120 g per day. 225 P a g e

7 Table 3: Ideal Amino acid Profile of Experimental Dietary Treatments Relative to Lysine Amino acid profile relative to lysine % 2 CG18 G16 G14 lysine Methionine + Cysine Tryptophan Threonine Valine Isoleucine Met+Cys requirements set as 100%. Digestible amino acid bases. Lysine requirements set as 100%. Table 4: Overall Production Performance of Laying Hens During Experimental Trial Parameter CG18 G16 G14 Weight gain (g) Egg production % Egg mass (g /hens) Table 5: Overall Egg Quality Parameters of Laying Hens During Experimental Period CP% Parameter CG18 G16 G14 Egg weight (g) a ± a ± a ± 0.41 Egg volume ab ± a ± b ± 0.07 Egg specific gravity (cm 3 ) 1.18 a ± ab ± b ± Yolk height (mm) b ± b ± a ± 0.14 Albumin Height (mm) a ± a ± a ± 0.04 Yolk diameter (mm) 42.9 a ± a ± a ± 0.2 Albumin diameter 28.5 b ± a ± c ± 0.23 Yolk weight (g) 16.1 a ± ab ± b ± 0.2 Albumin weight (g) a ± a ± a ± P a g e

8 Egg shell weight (g) 6.7 b ± a ± a ± 0.05 Yolk index 0.4 ab ± b ± a ± Albumin index 0.36 b ± c ± a ± Shell thickness (mm) 0.33 a ± a ± a ± Haugh unit a ± a ± a ± Values are means ± SE 2. a,b,c Values with different superscripts at the same row are significantly different at P Table 6: Economic efficiency study of different dietary treatments of the experimental trial Input Output Dietary treatments Feedintake/hen (Kg) Price/Kg feed (L.E) Feed cost/hen (L.E) Egg number/hen Total income (L.E) 1 Net revenue (L.E) EE 2 (%) REE 3 (%) CG G G Total income= Egg number/hen price of one egg (0.56 L.E) 2 Economic efficiency= net revenue (total income feed cost) / feed cost 3 Relative economic efficiency = (EE treatment / EE control (18%CP)) 100 VI. CONCLUSION On the basis of our current study, it is to be concluded that reduced CP- amino acid supplemented diets may be used successfully in layers nutrition while; maintaining laying hens performance without adding extra costs to egg producers. In addition to that, this strategy may be used to decrease fecal nitrogen excretion and thus minimizing environmental pollution. 227 P a g e

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