Effect of dietary supplementation of L-threonine on performance of commercial broiler chicken

Introduction

The poultry sector in India has emerged as one of the most dynamic components of the agroanimal industry, exhibiting remarkable growth in recent decades. Annual growth rates of 16% in poultry population, 8.5% in egg production, and 7.8% in broiler output surpass the agricultural sector's overall growth rate of 2.5%. India currently ranks as the third-largest producer of eggs and the fourth-largest producer of chicken meat globally (BAHFS, 2019) [2] . However, the per capita availability of eggs (79/year) and chicken meat (3.11 kg/year) remains below the Indian Council of Medical Research (ICMR) recommendations of 180 eggs and 11 kg meat annually, indicating substantial scope for improvement in production efficiency. Feed constitutes more than 70% of the total cost of poultry production, with protein being the most expensive component. Excessive dietary crude protein (CP) not only increases costs but also contributes to environmental pollution through elevated nitrogen excretion. Recent advancements highlight that crystalline amino acid supplementation-particularly essential amino acids (EAAs)-enables formulation of low-CP diets without compromising growth, feed efficiency, or nutrient balance (Chamba et al., 2014) [3] . L-Threonine is the third limiting amino acid in broiler diets after methionine and lysine. It plays a vital role in protein synthesis, immune competence, feathering, and gastrointestinal mucin production (Lemme, 2003) [5] . As an indispensable amino acid, threonine must be supplied in adequate dietary amounts. Deficiency results in reduced growth, poor feed efficiency, and impaired carcass traits, whereas optimal supplementation improves performance and nitrogen utilization (Azzam et al., 2015) [1] . In this context, the present study was conducted to evaluate the effect of dietary L-threonine supplementation in reduced-CP diets on growth performance, feed utilization, carcass characteristics, and economic efficiency of commercial broilers.

Materials and Methods

Experimental Design A total of 224 straight-run commercial day-old broiler chicks of Vencobb strain were randomly distributed to seven dietary treatments (T 1 to T 7 ) of varying levels of CP and L-Threonine.

Each treatment consisted of four replicates containing eight chicks per replicate. The seven treatments were: T 1 diet kept as basal diet with 23, 22 and 20% CP and 0.86, 0.80 and 0.77% of L-Threonine in pre-starter, starter and finisher mash, respectively. T 2 diet with 22.5, 21.5, 19.5% CP and 0.946, 0.880 and 0.847% of L-Threonine in pre-starter, starter and finisher mash, respectively.T 3 diet with 22, 21, 19% CP and 0.946, 0.880 and 0.847% of L-Threonine in pre-starter, starter and finisher mash, respectively.T 4 diet with 21.5, 20.5, 18.5% CP and 0.946, 0.880 and 0.847% L-Threonine in pre-starter, starter and finisher mash, respectively. T 5 diet with 22.5, 21.5 and 19.5% CP and 0.989, 0.920 and 0.885% L-Threonine in pre-starter, starter and finisher mash, respectively. T 6 diet with 22, 21, 19% CP and 0.989, 0.920 and 0.885% L-Threonine in pre-starter, starter and finisher mash, respectively. T 7 diet with 21.5, 20.5 and 18.5% CP and 0.989, 0.920 and 0.885% L-Threonine in pre-starter, starter and finisher mash, respectively. Birds were reared in deep litter system using standard management and health care practices.

Parameters Studied

 Body weight (BW): recorded weekly (day-old to 6 weeks).  Body weight gain (BWG): calculated for pre-starter (0-2 weeks), starter (3-4 weeks), finisher (5-6 weeks), and overall periods (0-6 weeks).  Feed consumption (FC): recorded for each phase and overall.  Feed conversion ratio (FCR): calculated weekly and cumulatively.  Carcass characteristics: recorded at the end of the trial.  Economics: return over feed cost (ROFC) based on feed cost and income from live weight sale.

Statistical Analysis

The data were analysed using completely randomized design as per Snedecor and Cochran (1994) [12] . Means of replicates under each treatment was considered for analysis.

Results and Discussion

Body Weight and Body Weight Gain

The data on mean body weight (BW) of broilers at day-old age and then at weekly interval is presented in Table 1. At the end of 6th week, dietary treatment T 4 showed significantly (p<0.05) higher in body weight as compared to control and other dietary treatments. The results of the present study showed that the body weight of broilers from treatment T 4 supplemented with addition of 10% L-Threonine than basal level and with reduction of 1.5% CP% improved body weight by 203.30 and 225.27 g at the end of 5th and 6th week of age, respectively as compared to control. The present findings were in accordance with the results of Neto et al., (2012) [8] and Azzam et al., (2015) [1] who found that broiler chicken fed diets supplemented with L-Threonine had significantly (p<0.05) higher body weight at 42 days of age as compared to birds fed with basal diet.

The BWG during pre-starter, starter, finisher phases and overall experimental period is given in Table 2. Results of the study indicated that mean body weight gain of birds fed with T 2 to T 4 diet with 10% additional L-Threonine with 0.5-1.5% reduced CP% was significantly (p<0.05) higher than the birds fed with T 6 , T 5 and T 1 , diet. Perusal of the data recorded in the study indicated significantly higher weight gain was noticed in broilers offered diet containing 10% additional L-Threonine with 1.5% reduced CP%. The present findings were in accordance with the findings of Roy (2013) [10] , Shirzadegan et al., (2015) [11] .

Feed Consumption

The data on feed intake (g/bird) recorded at a weekly interval as well as pre-starter, starter, finisher phase and overall experimental period is shown in Table 3. The mean feed consumption of birds fed with T 4 diet was significantly (p<0.05) higher than the birds fed with T 5 and T 6 diets but did not differ significantly from T 1 , T 2 , T 3 and T 7 , diets. The lowest feed consumption was observed in T 5 Minimum and significantly (P<0.05) lower feed intake was observed in broilers assigned all except T 2 and T 5 (0.5% CP reduction than basal diet with addition of 15% L-Threonine) diet among the other groups. Maximum and significantly (P<0.05) higher feed intake was observed in broilers assigned T 2 and T 4 (0.5-1.5% CP reduction than basal diet with addition of 10% L-Threonine) diet, among the other L-Threonine supplemented groups. Present results were similar to the results reported by Estalkhzir et al., (2013) [4] who observed that the birds fed with additional L-Threonine showed significantly higher feed intake as compared to other groups.

Feed Conversion Ratio

The data on average weekly FCR is depicted in Table 4. Supplementation of L-Threonine in the diet of broilers improved FCR. Minimum FCR was noted in broilers assigned T 5 diet with 0.5% CP reduction than basal diet with addition of 15% L-Threonine during 5th week and 6 th week. While, maximum FCR was observed in those assigned T 2 diets (0.5% CP reduction than basal diet with addition of 10% L-Threonine). Thus, supplementation of diet with 0.5% CP reduction than basal diet with addition of 15% L-Threonine to broilers caused significant (P<0.05) improvement in FCR. Present results were in accordance with the results of Ashok et al., (2017) [6] who found that lowest feed conversion ratio was observed in the groups fed diet with reduced excess L-Threonine level compared to basal diet. Treatment means of the data clearly indicated that the net return over feed cost/bird was influenced due to reduction of CP% and supplementation of L-Threonine in the diet. It was lowest in broilers assigned control diet containing L-Threonine as per NRC requirement. reduction of CP% from 0.5 to 1.5% with addition of 10 to 15% L-Threonine than NRC level in the broiler diet caused a increase in the net return over feed cost as compared to control group. However, diet group supplemented with 15% additional L-Threonine level with 0.5% reduced CP% recorded better ROFC than rest of the L-Threonine supplemented diets.

References

1. Azzam MMM, El-Gogary MR. Effects of dietary threonine levels and stocking density on the performance, metabolic status and immunity of broiler chickens. Asian J Anim Vet Adv. 2015;10(5):215-225.
2. Basic Animal Husbandry and Fishery Statistics (BAHFS). Annual Report 2018-19. New Delhi: Department of Animal Husbandry, Dairying and Fisheries, Ministry of Agriculture and Farmers Welfare, Government of India; 2019. p. 5.
3. Chamba F, Puyalto M, Ortiz A, Torrealba H, Mallo JJ, Riboty R. Effect of partially protected sodium butyrate on performance, digestive organs, intestinal villi and Escherichia coli development in broiler chickens. Int J Poult Sci. 2014;13(7):390-396.
4. Estalkhzir FM, Khojasteh S, Jafari M. Effect of different levels of threonine on performance and carcass characteristics of broiler chickens. J Nov Appl Sci. 2013;2(9):382-386.
5. Lemme A. Reassessing amino acid levels for Pekin ducks: Today's meat-type ducks have higher essential amino acid requirements than previously assumed. Poultry Int. 2003;42(4):18-25.
6. Madapurada A, Neraj P, Sushma R, Krishnamurthy TN, Ananda MG. Effect of L-threonine supplementation to diets with reduced crude protein on body weight and survivability in commercial broilers. J Pharmacogn Phytochem. 2017;6(6):1539-1542.
7. Taghinejad-Roudbaneh M, Babaee MJ, Afrooziyeh M, Alizadeh B. Estimation of dietary threonine requirement for growth and immune responses of broilers. J Appl Anim Res. 2013;41(4):474-483.
8. Neto RCL, Costa FGP, Furlan RL, Givisiez PEN, Goulart CC, Oliveira CFS, et al. Levels of digestible threonine for male broilers from 1 to 7 days of age. J Appl Poult Res. 2012;21(4):757-763.
9. Rao SR, Raju MVLN, Panda AK, Poonam NS, Moorthy OK, Srilatha T, Sunder GS. Performance, carcass variables and immune responses in commercial broiler chicks fed graded concentrations of threonine in diets containing sub-optimal protein levels. Anim Feed Sci Technol. 2011;169(3-4):218-223.
10. Roy RR. Effects of low-protein threonine-supplemented diet on productivity and cost effectiveness of commercial broilers [doctoral dissertation]. India; 2013.
11. Shirzadegan K, Nickkhah I, Jafari MA. Impacts of dietary L-threonine supplementation on performance and intestinal morphology of broiler chickens during summer time. Iran J Appl Anim Sci. 2015;5(2):353360.
12. Snedecor GW, Cochran WG. Statistical methods. 8th ed. New Delhi: Affiliated East-West Press Pvt Ltd; 1994. p. 503-507.
13. Al-Hayani WKA. Effect of threonine supplementation on broiler chicken productivity traits. Int J Poult Sci. 2017;16(4):160-168.