Influence of low-protein diet with different levels of amino acids on laying hen performance, quality and egg composition

MAHMOUD ALAGAWANY MOHAMED M. EL-HINDAWY MOHAMED E. ABD EL-HACK MUHAMMAD ARIF SABRY ABD EL-SAYED About the authors

Abstract

The present study aimed to investigate the consequences of dietary levels of crude protein (CP) and total sulfur amino acids (TSAA, Met+Cys) on productive performance, egg quality and egg components for Lohmann Brown laying hens through 18-34 weeks of age. A 2×3 factorial design experiment was conducted using two levels of CP (16 and 18 %) and three levels of Met+ Cys (0.67, 0.72 and 0.77 %). A total of 144 Lohmann Brown laying hens at 18 weeks of age were randomly divided into 6 treatment groups. The best values of final body weight and body weight change were recorded by the hens fed 18 % CP diet. Increasing dietary CP up to 18 % accompanied with the best (P> 0.01) feed conversion, egg weight and egg mass. The combination between low-CP diet (16 %) and 0.72 % Met+ Cys gave the best percentage of egg production. The majority of egg quality traits were not significantly altered by dietary treatments. The interaction between CP and Met+Cys levels had a statistical (P>0.01) impact on egg content of moisture and total solids only. It could be concluded that the best production criteria could be obtained by using 0.72% Met+Cys. Moreover, dietary level of 16 or 18 % CP with 0.72% Met+Cys is recommended for feeding Lohmann hens.

Key words
layers; low-protein diet; amino acids; production; egg quality; blood

INTRODUCTION

The first an important step to optimize performance and production in poultry is proper nutrition. Increasing egg yield profits is mainly depending on flock performance, feed and egg prices as well as farm management (AlagawanyALAGAWANY M, ABD EL-HACK ME, FARAG MR, TIWARI R, SACHAN S, KARTHIK K & DHAMA K. 2016. Positive and Negative Impacts of Dietary Protein Levels in Laying Hens. Asian J Anim Sci 10: 165-174. et al. 2014, Abou-KassemABOU-KASSEM DE, ASHOUR EA, ALAGAWANY M, MAHROSE KM, REHMAN & DING C. 2018. Effect of feed form and dietary protein level on growth performance and carcass characteristics of growing geese. Poult Sci: 761-770. et al. 2018). Several factors affect productive performance of laying hens. Nutrient levels in the diet should be optimized not to exceed the optimum level in order to optimize profits. Improving or maintaining laying hen performance, or both, could be achieved by maximizing the utilization of nutrients from current feedstuffs (AbdABD EL-HACK ME, ALAGAWANY M, FARAG MR & DHAMA K. 2015. Use of Maize Distiller’s Dried Grains with Solubles (DDGS) in Laying Hen Diets: Trends and Advances. Asian J Anim Vet Adv 10:690-707. El-Hack et al. 2015). Reduction in production costs is needed although laying efficiency and high egg production are characteristics of the modern laying hen. Soybean meal and corn are the main ingredients providing crude protein and energy in commercial poultry diets (Alagawany et al. 2016ALAGAWANY M, EL-HINDAWY M, ATTIA A, FARAG MF & ABD EL-HACK EM. 2015. Influence of dietary choline levels on growth performance and carcass characteristics of growing Japanese quail. Adv Anim Vet Sci 3: 109-115.). The amino acid methionine is now available at competitive prices. It is now possible to formulate poultry diets which provide a non-protein nitrogen and minimum excess of amino acids (Alagawany et al. 2015ALAGAWANY M, ABD EL-HACK ME, LAUDADIO V & TUFARELLI V. 2014. Effect of low-protein diets with crystalline amino acid supplementation on egg production, blood parameters and nitrogen balance in laying Japanese quails. Avian Biol Res 7: 235-243.). However, we are unable to formulate diets with very low levels of crude protein that contain optimum levels of essential amino acids (ZeweilZEWEIL HS, ABDALAH AA, AHMED MH & AHMED MRS. 2011. effect of different levels of protein and methionine on performance of Baheij laying hens and environmental pollution. Egypt Poult Sci 31: 621-639. et al. 2011). But it is possible to readily reduce crude protein supply by 15 – 20% using synthetic amino acids supplements if its cost could be economic and applicable (AarninkAARNINK AJA, HOEKSMA P & VAN OUWERKERK ENJ. 1993. Factors affecting ammonium concentrations in slurry from fattening pigs. Nitrogen Flow in Pig Production and Environmental Consequences, p. 413-420. et al. 1993). New feeding strategies in poultry production gave a new perception with the advent of environmental problems which always come from the oversupply of nutrients, particularly protein and amino acids (MeluzziMELUZZI A, SIRRI F, TALLARICO N & FRANCHINI A. 2001. Nitrogen retention and performance of brown laying hens on diets with different protein content and constant concentration of amino acids and energy. Br Poult Sci 42: 213-217 et al. 2001, TorkiTORKI M, NASIROLESLAMI M & GHASEMI HA. 2016. The effects of different protein levels in laying hens under hot summer conditions. Anim Prod Sci 57(5): http://dx.doi.org/10.1071/AN15463. et al. 2016). So the present investigation designed as an attempt to reduce nutrient oversupply through decreasing dietary crude protein level and trying to compensate amino acid deficiency by supplementing graded levels of total sulphur amino acids. The objective of this study was to investigate quantitatively describe the effect of dietary levels of crude protein and total sulfur amino acids on productive performance, egg quality and whole egg composition for Lohmann Brown laying hens.

MATERIALS AND METHODS

The current experiment was consummated at Poultry Research Farm, poultry Department, Faculty of Agriculture, Zagazig University, Egypt. All the experimental procedures were conducted in accordance with the Local Experimental Animals Care Committee, and affirmed by the ethics of the institutional committee at Faculty of Agriculture, Zagazig University. Hens were breeding for utilizing rearing guidelines got from Zagazig University standard working methodology.

Experimental design, hens and diets

One Hundred and fourth four of Lohmann Brown laying hens, 18 wk of age, were procured from a local commercial layer farm. They were randomly allocated to six treatments groups, each of which included six repeats of four hens. Each replicate was housed in one layer cage. The current study was conducted in a 2×3 factorial design experiment including two (low and normal) levels of CP (16 and 18 %) and three levels of Met+ Cys (0.67, 0.72 and 0.77 %) through the experimental period from 18-34 weeks of age (Table I). The initial average live body weight of hens in all experimental treatment groups were nearly the same and had no statistically differences. All hens were housed in a windowed poultry house under the same managerial and hygienic conditions. The hens were exposed to photoperiod 17 h light: 7h darkness per day and were fed on ad-libitum basis and fresh water was supplied freely during the experimental period. Vaccination and medical program were done according to the different stages of age under supervision of a veterinarian.

Table I
Composition and chemical analysis of the experimental diets.

Laying productive performance and egg quality criteria

The layer hens were weighed at the beginning and the end day of experimental period, the live body weight change was then computed by the difference between the initial and final live body weights. On a hen-day basis, egg weight, egg production, and hen mortality were registered daily and feed intake was recorded weekly on a replicated basis. Egg mass was computed by multiplying by egg weight by hen-day egg number produced. Feed conversion ratio (FCR) was calculated as germ of feed intake/hen/day divided by gram of egg mass produced/hen/day. At the end of experimental period, 3 eggs from each replicate were chosen randomly to evaluate exterior and interior egg quality parameters such as (percentages of yolk, albumen, shell, and egg shape index (ESI), yolk index, shell thickness, Y:A ratio, Unit surface shell weight (USSW) and Haugh unit) which were measured according to RomanoffROMANOFF AL & ROMANOFF AJ. 1949. The Avian Egg. New York: John Wiley & Sons Inc. & Romanoff (1949).

Egg analysis

At 34 weeks of age (end of experimental period), 5 eggs from each treatment group were selected randomly for determination whole solids and chemical composition of the whole eggs. After breaking eggs, the yolk and albumen were mixed with shell and homogenate into an aluminum dish where a known weighted homogenies egg sample dried in hot air oven for 24 hours at 60˚c to eliminate primary moisture, then samples dried again for 3 hours at 105˚ c to eliminate secondary moisture, then weighed. The chemical proximate analysis of dried whole eggs and feed samples were carried out according to AOACAOAC. 2003. Association of Official Analytical Chemists Official Methods of Analysis 15th ed., Published the A.O.A.C. Washington D.C. (2003) for determination of DM (ID 930.15), OM (ID 942.05), CP (ID 954.01), EE (ID 945.16) and CF (ID 978.10).

Statistical analysis

Data were statistically analyzed on a 2×3 factorial design basis according to SnedecorSNEDECOR GW & COCHRAN WG. 1982. Statistical Methods. Iowa State University Press, Ames, USA. & Cochran (1982) using the following model:

Y i j k = µ + A i + S j + A S i j + e i j k

Where: Yijk = an observation, µ = the overall mean, Ai = effect of protein level (i=1 and 2), Sj = effect of Met+ Cys level (j =1 to 3), ASij=the interaction between the two variables and eijk= Experimental random error. Tukey’s test was used for comparison among significant means.

RESULTS

Hen productive performance

Results in Table II indicated that daily feed intake and egg production percentage were not statistically different between low or normal-CP diets, although they were insignificantly improved with increasing CP level. Increasing dietary CP up to 18 % accompanied with the best (P> 0.01) feed conversion, egg weight and egg mass comparing with the low CP level. Dietary supplementation of Met+ Cys had statistical impacts on feed conversion ratio (P=0.020), egg production % (P=0.031) and egg mass (P=0.041). The intermediate level of Met+ Cys (0.72 %) achieved the best results of the aforementioned parameters in comparison to other levels. Only egg production percentage and egg weight were significantly (P> 0.01) influences as a response to the interaction among CP and Met+ Cys levels. The combination between low-CP diet (16 %) and 0.72 % Met+ Cys gave the best percentage of egg production. However, the best egg weight was found in the group fed normal-CP diet (18 %) supplemented with 0.77 % Met+ Cys comparing with other treatment groups.

Table II
Effect of low-protein diet with different levels of Met+Cys on productive performance of laying hens during the experimental period.

Results in Table II also illustrate the impact of low-CP diet, Met+ Cys supplementation and their combinations on body weight change during the experimental period. It is obvious that body weight change was significantly (P> 0.05 or 0.01) altered due to low-CP diet. The best values of final body weight (1790 g) and body weight change (139 g) were recorded by the hens fed normal-CP diet (18 % CP) comparing with those fed the low-CP diet. The different levels of Met+ Cys supplementation did not exert any significant effect on the values of body weight change. The combination between low-CP diet and Met+ Cys levels had a statistical (P> 0.05) impact on body weight change. It is noticeable that the interaction between 18% CP diet and 0.77 % Met+ Cys gave the heaviest body weight compared with other combinations. Meanwhile, the worst values were found by the combination between 16 % CP with 0.72 % Met+ Cys as compared with other treatment groups.

Egg quality criteria

Effects of low-CP diet, Met+ Cys supplementation and their interactions on external and internal egg quality traits are shown in Table III. Results revealed that increasing dietary CP level depressed (P= 0.042) egg weight value and increased (P= 0.024) the values of USSW and yolk index. All other egg quality parameters were not affected by dietary CP levels. Excluding yolk index, all external and internal egg quality traits were not significantly altered by Met+ Cys levels or the interaction among CP and Met+ Cys levels.

Table III
Effect of low-protein diet with different levels of Met+Cys on exterior and interior egg quality of laying hens during the experiment.

Chemical composition of whole egg

Data presented in Table IV show the impact of dietary treatments on Chemical composition of whole egg. Neither dietary CP nor Met+ Cys levels had significant impact on any of egg nutrients studied. The interaction between CP and Met+ Cys levels had a statistical (P>0.01) impact on egg content of moisture and total solids only. The combination between 18 % CP and 0.72 % Met+ Cys recorded the highest value of egg moisture and the minimum value of egg total solids compared with other combinations.

Table IV
Effect of low-protein diet with different levels of Met+Cys on chemical composition of whole egg of laying hens during the experimental period.

DISCUSSION

Hen productive performance

Insignificant improvements in daily feed intake and egg production percentage were noticed with increasing dietary CP level (Table II). In partially agreement, NovakNOVAK C, YAKOUT H & SCHEIDELER S. 2006. The combined effects of dietary lysine and total sulfur amino acid level on egg production parameters and egg components in Dekalb Delta laying hens. Poult Sci 83: 977-984. et al. (2006) who indicated that feed consumption was affected by protein intake, where feed consumption linearly decreased as protein intake decreased for Hy-line W-98 hens from 20 to 43 wk of age. On the contrary, Zeweil et al. (2011) mentioned that daily feed intake was insignificantly affected by different protein levels (12, 14 and 16% CP) in laying hens diet during the experimental period (28 – 48 wk of age). The present study showed an improvement in feed conversion, egg weight and egg mass with increasing CP level. Similarly, MoustafaMOUSTAFA M, KOUT EL-KLOULB E, HUSSEIN AA & GAD EL-HAK MK. 2005. A study on the energy and protein requirement of Mamoura local strain chickens during laying period. Egypt Poult Sci 25: 637-651. et al. (2005) and Novak et al. (2006) concluded that feed conversion ratio improved when protein level of layer diet increased. Novak’s results also supported ours regarding egg weight. Authors found that the highest egg weight value was for 19 g of protein/hen / day compared to 17 or 14.4 g of protein /hen/day. Also, BouyehBOUYEH M & GEVORGIAN O. 2011. Influence of different levels of lysine, methionine and protein on the performance of laying hens after peak. Int Anim Vet Adv 10: 532-537. & Gevorgian (2011) who mentioned that egg mass had significantly increased by dietary protein level. Whereas, GunawardanaGUNAWARDANA P, ROLAND DA & BRYANT MM. 2009. Effect of energy and protein performance, egg components, egg solids, egg quality, and profits in molted Hy-line W-36 hens. J Appl Poult Res 17: 432-439. et al. (2009) stated that the different levels of protein in the diet of commercial leghorn laying hens didn’t significantly affect egg weight.

Results of the present study confirmed that adding 0.72 % Met+Cys to the diet exerted the best feed conversion, egg production and egg mass (Table III). The enhancement of feed efficiency may be due to the increase of egg mass and may be attributed to more balanced amino acids. The obtained results coincided with those found by KoreleskiKoreleski J & Świątkiewicz S. 2011. Effect of methionine and energy level in high protein organic diets fed to laying hens. Ann Anim Sci 10: 83-91. & Świątkiewicz (2011) and Zeweil et al. (2011) who reported that methionine supplementation significantly improved feed conversion per kg eggs.

Feed conversion ratio, egg production, egg weight and egg mass were significantly affected by an increase in digestible sulphur amino acids intake (KakhkiKAKHKI AMR, GOLIAN A & ZARGHI H. 2016. Effect of digestible methionine + cystine concentration on performance, egg quality and blood metabolites in laying hens. Br Poult Sci 57: 403-414. et al. 2016). Contradicting results obtained by HassanHASSAN GM, FARGHALY M, SOLIMAN FNK & HUSSAIN HA. 2000. The influence of strain and dietary protein level on egg production traits for different local chicken strain. Egypt Poult Sci 20: 49-63. et al. (2000) who pointed out that feed efficiency was not significantly improved with increased TSAA intake during the first phase of feeding (20 to 40 wk of age). For egg production, our results are in line with those reported by LiuLIU ZG, WU MM, BRYANT DA & ROLAND SR. 2005. Influence of added synthetic lysine in low-protein diets with the methionine plus cysteine to lysine ratio maintained at 0.75. J Appl Poult Res 14: 174-182. et al. (2005) who reported that increasing dietary levels of total sulphur amino acids (TSAA) from improved (p<0.05) egg number for laying hens. Also, Abd El-Maksoud et al. (2011) ABD EL-MAKSOUD A, EL-SHEIKH SM, SALAMA AA & KHIDR RE. 2011. Performance of local laying hens as affected by low protein diets and amino acids supplementation. Egypt Poult Sci 31: 249-258.stated that egg production of laying hens fed methionine supplemented diet was significantly increased versus hens fed diet without methionine supplementation. Our findings concerning the positive effect of Met+ Cys supplement on egg mass are consistent with HarmsHARMS RH & RUSSELL GB. 1996. A re-evaluation of the methionine requirement of the commercial layer. J Appl Anim Res 9: 141-151. & Russell (1996) and Zeweil et al. (2011) who found that egg mass increased as methionine level increased from 0.23 to 0.31% in the first productive cycle for laying hens. On the other hand, SolarteSOLARTE WN, ROSTAGNO HS, SOARES PR, SILVA MA & URIBE VLF. 2005. Nutritional requirements in methionine + cysteine for white-egg laying hens during the first cycle of production. Int J Poult Sci 4: 965-968. et al. (2005) reported that increasing total sulphur amino acids level from 0.684 to 0.734% had no further improvement on egg mass.

In the current study, positive responses were detected on the percentage of produced egg and values of egg weight due to the interaction between dietary CP levels and Met+Cys levels. With the same trend, PavanPAVAN AC, MÓRI C, GARCIA EA, SCHERER MR & PIZZOLANTE C. 2005. Levels of protein and sulfur amino acids on performance, egg quality and nitrogen excretion of Brown egg laying hens. Rev Bras Zootec 34: 568-574. et al. (2005) found significant differences for egg weight with the combination of 15.5 and 0.71; 17 and 0.71; 15.5 and 0.64; 14 and 0.71; 17 and 0.64 of CP and TSSA, respectively, showing the highest values. Also, the interaction between protein and methionine revealed that the best average egg weight was produced by hens fed 16% CP supplemented by 2.74 methionine % of CP (Zeweil et al. 2011). On the contrary to our results, Zeweil et al. (2011) indicated that the interaction effect between protein and methionine showed insignificant differences in egg production at the end of experimental period.

An improvement in body weight was noticed due to normal-CP diet in the present study (Table II). This improvement may be due to the bioavailability and balanced amino acids which provided by the tested diet. However, lower body weight due to feeding the lowest dietary treatment (16% CP) was cleared by ColeCOLE ADJ. 1996. An ideal protein for each species. 12th Annual Symposium of Biotechnology in the Feed Industry. Alltech, 1996, Kentucky, USA. Feed Compounder 16(9): 14-19. (1996) who confirmed that amino acids may be absorbed in unavailable form because of fructose-lysine complex production. This would inhibit the release of trypsin and lysine utilization remains only 10% which leads to slower absorption of amino acids and consequently poor laying performance. Moreover, the reservation of body protein gradually depletes in birds fed on reduced CP diet. Our results disagree with those data reported by Abd El-Maksoud et al. (2011) and Zeweil et al. (2011) who reported insignificant difference in the body weight for laying hens fed different levels of protein. According to our findings, the combination among the highest levels of both dietary CP and supplemental Met+Cys produced the heaviest hen weight (Table II). This result agree with those found by Novak et al. (2006) who postulated that body weight gain elevated side by side with increasing dietary CP levels and with methionine supplementation. In contrast, Abd El-Maksoud et al. (2011) and Zeweil et al. (2011) showed that the interaction impact between protein and methionine revealed insignificant differences in live body weight at the end of experiment.

Egg quality criteria

As explained in Table III, no significant impacts were detected on the majority of egg quality criteria due to dietary treatments. Likewise, Novak et al. (2006) reported no significant (p<0.05 or 0.01) difference in albumen, yolk, shell percent and Haugh unit when increasing or decreasing CP in layer diet during 20- 43 wk of age. Moreover, Zeweil et al. (2011) revealed that the most of egg quality traits had not been affected by protein levels. Koreleski & Świątkiewicz (2011) indicated that egg shell characteristics were unchanged when methionine content in the diet was increased. Similar to our results, Pavan et al. (2005) found no significant differences in internal egg quality with the interaction between protein and TSAA in layer diets. Also, Novak et al. (2006) reported no significant (p<0.05 or 0.01) difference in albumen, yolk, shell percent and Haugh unit due to interaction effect between CP and TSAA in layer diet during 20- 43 wk of age. On the other hand, Haugh unit score was significantly lower in layers fed a 13% CP diet in comparison with control, but yolk colour index was higher (P < 0.05) for the layers fed the 14% and 13% CP diets than those fed the normal diet (Torki et al. 2016).

Chemical composition of whole egg

No significant impacts were recorded due to CP or Met + Cys levels on the chemical composition of the egg as shown in Table IIII. Similar results were obtained by Gabriel & Babatunde (1976)GABRIEL MB & BABATUNDE LF. 1975. Effects of protein levels in the diets of layers on the egg production rate and the chemical composition of poultry eggs in the tropics. J Sci Food Agri 21: 54-462. who reported that both the total moisture and crude protein percentages were significantly increased as the dietary protein levels increased (20%) but the differences in total ash, shell and total lipid percentages were not significantly differed and were remarkably constant in white leghorn egg. GarciaGARCIA EA, MENDES AA, PIZZOLANTE CC, SALDANHA EB, MOREIRA J, MORI C & PAVAN AC. 2005. Protein, methionine+cystine and lysine levels for japanese quails during the production phase. Braz J Poult Sci 7: 11-18. et al. (2005) suggested that Met + Cys levels had no effect on egg contents.

CONCLUSIONS

In view of the aforementioned results and discussion, conclusion could be drawn that the best production criteria could be obtained by using 0.72% Met+Cys. Moreover, dietary level of 16 or 18 % CP with 0.72% Met+Cys is recommended for feeding Lohmann hens.

ACKNOWLEGMENTS

The authors declare that they have no competing interests.

REFERENCES

  • AARNINK AJA, HOEKSMA P & VAN OUWERKERK ENJ. 1993. Factors affecting ammonium concentrations in slurry from fattening pigs. Nitrogen Flow in Pig Production and Environmental Consequences, p. 413-420.
  • ABD EL-HACK ME, ALAGAWANY M, FARAG MR & DHAMA K. 2015. Use of Maize Distiller’s Dried Grains with Solubles (DDGS) in Laying Hen Diets: Trends and Advances. Asian J Anim Vet Adv 10:690-707.
  • ABD EL-MAKSOUD A, EL-SHEIKH SM, SALAMA AA & KHIDR RE. 2011. Performance of local laying hens as affected by low protein diets and amino acids supplementation. Egypt Poult Sci 31: 249-258.
  • ABOU-KASSEM DE, ASHOUR EA, ALAGAWANY M, MAHROSE KM, REHMAN & DING C. 2018. Effect of feed form and dietary protein level on growth performance and carcass characteristics of growing geese. Poult Sci: 761-770.
  • ALAGAWANY M, ABD EL-HACK ME, FARAG MR, TIWARI R, SACHAN S, KARTHIK K & DHAMA K. 2016. Positive and Negative Impacts of Dietary Protein Levels in Laying Hens. Asian J Anim Sci 10: 165-174.
  • ALAGAWANY M, ABD EL-HACK ME, LAUDADIO V & TUFARELLI V. 2014. Effect of low-protein diets with crystalline amino acid supplementation on egg production, blood parameters and nitrogen balance in laying Japanese quails. Avian Biol Res 7: 235-243.
  • ALAGAWANY M, EL-HINDAWY M, ATTIA A, FARAG MF & ABD EL-HACK EM. 2015. Influence of dietary choline levels on growth performance and carcass characteristics of growing Japanese quail. Adv Anim Vet Sci 3: 109-115.
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  • GARCIA EA, MENDES AA, PIZZOLANTE CC, SALDANHA EB, MOREIRA J, MORI C & PAVAN AC. 2005. Protein, methionine+cystine and lysine levels for japanese quails during the production phase. Braz J Poult Sci 7: 11-18.
  • GUNAWARDANA P, ROLAND DA & BRYANT MM. 2009. Effect of energy and protein performance, egg components, egg solids, egg quality, and profits in molted Hy-line W-36 hens. J Appl Poult Res 17: 432-439.
  • HARMS RH & RUSSELL GB. 1996. A re-evaluation of the methionine requirement of the commercial layer. J Appl Anim Res 9: 141-151.
  • HASSAN GM, FARGHALY M, SOLIMAN FNK & HUSSAIN HA. 2000. The influence of strain and dietary protein level on egg production traits for different local chicken strain. Egypt Poult Sci 20: 49-63.
  • KAKHKI AMR, GOLIAN A & ZARGHI H. 2016. Effect of digestible methionine + cystine concentration on performance, egg quality and blood metabolites in laying hens. Br Poult Sci 57: 403-414.
  • Koreleski J & Świątkiewicz S. 2011. Effect of methionine and energy level in high protein organic diets fed to laying hens. Ann Anim Sci 10: 83-91.
  • LIU ZG, WU MM, BRYANT DA & ROLAND SR. 2005. Influence of added synthetic lysine in low-protein diets with the methionine plus cysteine to lysine ratio maintained at 0.75. J Appl Poult Res 14: 174-182.
  • MELUZZI A, SIRRI F, TALLARICO N & FRANCHINI A. 2001. Nitrogen retention and performance of brown laying hens on diets with different protein content and constant concentration of amino acids and energy. Br Poult Sci 42: 213-217
  • MOUSTAFA M, KOUT EL-KLOULB E, HUSSEIN AA & GAD EL-HAK MK. 2005. A study on the energy and protein requirement of Mamoura local strain chickens during laying period. Egypt Poult Sci 25: 637-651.
  • NOVAK C, YAKOUT H & SCHEIDELER S. 2006. The combined effects of dietary lysine and total sulfur amino acid level on egg production parameters and egg components in Dekalb Delta laying hens. Poult Sci 83: 977-984.
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  • SOLARTE WN, ROSTAGNO HS, SOARES PR, SILVA MA & URIBE VLF. 2005. Nutritional requirements in methionine + cysteine for white-egg laying hens during the first cycle of production. Int J Poult Sci 4: 965-968.
  • TORKI M, NASIROLESLAMI M & GHASEMI HA. 2016. The effects of different protein levels in laying hens under hot summer conditions. Anim Prod Sci 57(5): http://dx.doi.org/10.1071/AN15463.
  • ZEWEIL HS, ABDALAH AA, AHMED MH & AHMED MRS. 2011. effect of different levels of protein and methionine on performance of Baheij laying hens and environmental pollution. Egypt Poult Sci 31: 621-639.

Publication Dates

  • Publication in this collection
    03 Apr 2020
  • Date of issue
    2020

History

  • Received
    13 Mar 2018
  • Accepted
    13 Mar 2019
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