Volume 11, Issue 1: 46-51; March 25, 2021  
COMPARATIVE EFFECTS OF SYNTHETIC LYSINE AND METHIONINE  
SUPPLEMENTS ON PERFORMANCE AND CARCASS CHARACTERISTICS  
OF FINISHER BROILERS FED CORN-SOYBEAN BASED DIETS  
Victoria Nnenna MEREMIKWU and Peter Noah GBOSHE  
Department of Animal Science, Faculty of Agriculture and Forestry, Obubra Campus, Cross River University of Technology, PMB 112, Cross River  
State Nigeria  
Email: victoriameremikwu@yahoo.com;  
Supporting Information  
ABSTRACT: The aim of this research was to investigate the effects of lysine and methionine supplements in  
corn-soybean meal diets for finisher broilers, by comparing their combined and sole effects on performance  
and carcass characteristics of the birds. Parameters measured were performance (body weight, weight gain,  
feed intake, feed conversion ratio and mortality), dressed weight, dressing percentage, carcass cuts and  
internal organs. The experimental diets were: T1 (control) = lysine + Methionine, T2 (sole lysine) and T3 (sole  
methionine) supplements. Final body weight, weight gain, carcass and carcass cuts were significantly higher  
in the control (lysine + methionine) than in the sole supplemented diets, while sole supplementation with  
methionine (T3) produced significant higher values than sole lysine (T2) in the above mentioned parameters  
The liver was significantly enlarged in the birds that received the sole supplemented diets. Due to the  
enlarged liver of the birds fed the sole supplemented diets, it was concluded that supplementation with both  
lysine and methionine is indispensable in corn- soybean meal based diets for finisher broilers.  
Keywords: Amino acid, Broiler, Lysine, Methionine, Supplement.  
INTRODUCTION  
Broilers are domestic chickens (Gallus domesticus) of either sex, specially bred for rapid growth and meat production,  
commercially. They reach an average live weight of 2.2 to 2.8kg at 5 to 8 weeks of age on consumption of 3.3 to 5.0kg of  
feed depending on the nutrient content of the diet (Smith, 2001). Broiler production involves two phases in a production  
cycle namely; a “starter phase” from day one to week four of age, on a starter diet of 22-24% crude protein (CP) and a  
at the starter phase. This resulted to high cost of feed/kg weight gain at the finisher phase (Meremikwu and Gboshe,  
2007; Tandoğan and Çiçek, 2016). Although feed intake is very high at the finisher phase growth rate is also very high.  
Smith (2001) reported that the peak growth rate for the broiler is achieved between five to eight weeks of age. This is  
about 64.0g/day against 31.0g/day at the starter phase (Meremikwu and Gboshe, 2007).  
Protein is a vital nutrient in poultry nutrition because of its biological role in enhancing growth, egg production,  
immunity and adaptation to environment (Esmnil, 2016). The biological function of protein is attributed to specific amino  
acids (Lee et al., 2020). Lysine and methionine have universally been recognized as the limiting amino acids in most of  
the practical diets for broilers especially in diets base on corn and soybean meals which are the basal ingredients in most  
poultry diets (Farkhoy et al., 2012; Lee et al., 2020). Dietary deficiencies of lysine and methionine have been shown to  
impair chicken growth. Wen et al. (2014) reported that broilers fed methionine deficient diet exhibited low concentration  
of insulin-like growth factor 1 (IGF-1) within two days of the feeding, which resulted to low performance and low breast  
muscle growth. Cacew et al. (2005) reported that Lysine deficient diet increased fat synthesis at the expense of body  
protein accretion and energetic efficiency in broilers.  
The supplementation of poultry feeds with Lysine and methionine in crystalline form is very common in the poultry  
industry. Fishmeal is also described as an excellent source of high quality protein in cereal based diet for poultry  
because of the natural balance of essential nutrients including high content of lysine and methionine. However, the use  
of fish meal in most developing countries is limited by cost. Fishmeal is also reported to be a source of food-borne  
pathogen especially salmonella specie (Novoslavskij et al., 2016). Research has shown that industrial amino acids are  
competitively available and can replace protein sources in poultry diets to match amino acid requirements (Farrell, 2005).  
According to Farrell (2005), little or no-dietary protein sources can be used in poultry diets because protein sources are  
both scarce and expensive and nitrogen excretion is high.  
This research was designed to investigate the basic traits (essentialities) of lysine and methionine supplements in  
corn soybean meal based diets for finisher broilers by comparing their combined and sole effects on performance and  
carcass characteristics of finisher broilers. Parameters measured were performance (body weight, body weight gains, feed  
intake, feed conversion ratio and mortality), dressed weight, dressing percentage, carcass cuts and internal organs.  
46  
Citation: Meremikwu VN and Gboshe PN (2021). Comparative effects of synthetic lysine and methionine supplements on performance and carcass characteristics of  
finisher broilers fed corn-soybean based diets. Online J. Anim. Feed Res., 11(2): 46-51. DOI: https://dx.doi.org/10.51227/ojafr.2021.8  
MATERIALS AND METHODS  
Experimental site  
The study was carried out at the Teaching and Research Farm of the Department of Animal Science, Faculty of  
Agriculture and Forestry, Obubra Campus, Cross River University of Technology (CRUTEH), Cross River State Nigeria. The  
location of the study lies along Latitude 6” 4.6032’ N and Longitude 8” 19.9446East (Date and Time Information, 2020).  
Experimental treatments and design  
The experiment comprised three treatments each of which was replicated four times in a Complete Randomized  
Design (CRD). The treatments are as follows: T1 (control): Methionine and Lysine; T2: Lysine only; T3: Methionine only.  
Experimental diets  
The feed ingredients used for the diets were based on availability and cost. The cheapest and most available  
ingredients were used in formulation of the diets. They include; maize, Soybean meal, wheat offal, bone meal,  
mineral/vitamin premix, synthetic lysine and methionine and common salt. The diets were formulated according to NRC  
1994 specification. The experimental diets and their calculated chemical composition are presented in table 1. The  
chemical composition of the rations was obtained by calculation. The calculation was carried out using the spreadsheet  
method as described by Smith (2001).  
Table 1 - Experimental diets and their calculated nutrient composition  
T1 (control)  
Methionine + Lysine  
T2  
Lysine  
T3  
Ingredients (%)  
Methionine  
Maize  
48.94  
36.56  
10.00  
3.25  
0.25  
0.50  
49.26  
36.49  
10.00  
3.25  
0.25  
0.50  
0
49.26  
36.49  
10.00  
3.25  
0.25  
0.50  
0.25  
0
Soybean meal  
Wheat offal  
Bone meal  
Common salt  
Vitamin premix*  
DL-methionine  
Lysine Hcl  
0.25  
0.25  
0.25  
Total  
100.00  
100.00  
100.00  
Calculated composition of experimental diets.  
Crude protein (%)  
20.00  
3073.10  
3.99  
20.00  
3081.77  
4.00  
20.00  
3081.77  
4.00  
ME (Kcal/kg)  
Crude fibre (%)  
Methionine (%)  
0.98  
0.32  
0.57  
Lysine (%)  
1.58  
1.33  
1.08  
* Each 2.5 kg of premix contained: Vitamin A, 8,000,000 IU; Vitamin D1,,600,000 IU; Vitamin E, 20,000 IU; Vitamin K, 2,000mg; Vitamin B1,  
1,5000mg; Vitamin B2, 4,000mg; Vitamin B6, 2,000mg; Vit. B12, 10mg; Niacin, 15,000mg; Panthotenic Acid, 5,000mg; Folic Acid, 500mg;  
Biotin, 20mg; Choline Chloride, 200,000mg; Manganese, 80,000mg; Zinc, 50,000mg; Iron, 20,000mg; Copper, 5,000mg; Iodine, 1,000mg;  
Selenium, 200mg; Cobalt, 500mg; Antioxidant, 120,000mg.  
Management of experimental animals  
One hundred and twenty finisher broilers were used for the feeding trial which lasted for twenty-eight days. The birds  
were selected after brooding and randomly allotted to the twelve experimental units (10 birds per unit). They were housed  
in deep litter house partitioned into experimental units of 8ft × 12ft (width × length). Feed and water were given ad  
libitum. The birds were managed using standard husbandry practices for rearing broilers.  
Data collection  
The birds were weighed at the beginning of the experiment to get their initial body weight. They were weighed  
thereafter on weekly basis. Weight gain and feed conversion ratio were deduced from the weekly body weights. Feed  
offered daily was weighed and the left over weighed the following morning. Feed intakes were obtained by subtracting the  
leftover from the quantity supplied the previous day. At the end of the experiment at eight weeks of age, four birds were  
randomly selected from each treatment for carcass analysis. The birds were starved of feed but not water for twelve hours  
before slaughtering. The slaughtering and dressing of the birds were carried out using standard practices for processing  
broilers.  
Statistical analysis  
Data collected were subjected to analysis of variance (ANOVA) using Minitab Statistical Package. Significant means  
were separated using the Fisher Least Significant Difference (FLSD) that is containing in the statistical software.  
47  
Citation: Meremikwu VN and Gboshe PN (2021). Comparative effects of synthetic lysine and methionine supplements on performance and carcass characteristics of  
finisher broilers fed corn-soybean based diets. Online J. Anim. Feed Res., 11(2): 46-51. DOI: https://dx.doi.org/10.51227/ojafr.2021.8  
Ethical approval  
Birds were handled and managed in accordance with rules and recommendations in the “Guide for the Care and use  
of Animals”, presented in the Faculty of Agriculture and Forestry Obubra Campus, Cross River University of Technology,  
Cross River State, Nigeria (ethical committee).  
RESULTS AND DISCUSSION  
The calculated chemical composition of the experimental diets are presented in table 1, while the results of the  
performance and carcass characteristics of the experimental birds are presented in tables 2 and 3, respectively.  
Experimental diets  
The limitations of Lysine and methionine in corn-soybean meal diets for this experiment are revealed in the  
calculated chemical composition of the diet in table 1. The calculated lysine levels of all the diets including sole  
methionine diet (T3) were up to minimum requirement for finisher broilers, while the methionine levels in the sloe lysine  
diet (T2) was below minimum requirement (NRC, 1994). This result has revealed that methionine is the first limiting  
amino acid in corn-soybean meal based diets for broilers. This is supported by the report of Byrne (2018) that methionine  
is the first limiting essential amino acid in corn-soybean meal based diets for broilers.  
Performance  
The final body weights and body weight gains of the experimental birds differed significantly (P<0.05) between the  
treatments and were highest (P<0.05) in the control (T1, Lys + Meth) and lowest (P<0.05) in the sole lysine (T2). The sole  
methionine group (T3) were in-between the control and the sole lysine groups in the said parameters i.e. lower (P<0.05)  
than the control and higher (P<0.05) than the sole lysine. Feed intake did not differ (P<0.05) between the treatments.  
Feed conversion ratio followed the same trend with body weight and body weight gain, being highest (P<0.05) in the  
control and lowest (P<0.05) in the sole lysine group. Mortality was zero percent for all the treatments. The significant  
(P<0.05) higher performance of the control birds (T1, Lysine + methionine) over the sole lysine (T2) and sole methionine  
(T3) could be due to complementary effect of the amino acids to each other. This is supported by the report of Si et al.  
(2001 and 2014) that there were no interaction between Lysine and Methionine when they were fed equal to or in excess  
of NRC recommendations in broiler diets. Rather, each of the amino acids supplied a complimentary effect to meet  
specific deficiencies. The significant (P<0.05) low performance of the sole lysine birds (T2) in comparison to the sole  
methionine birds (T3) could be due to absence of complimentary effect of methionine and it is an indication that  
methionine is the first limiting essential amino acid in corn-soybean meal diet for broilers. This is also supported by the  
report of Neutkens (2005) that DL-methionine or Methionine hydroxyl is the first-limiting amino acid for birds, while Lysine  
is the first-limiting amino acid in corn-soybean meal based diet for pigs. According to Neutkens (2005), to use crystalline  
amino acids in low- protein diets effectively, and to minimize nitrogen excretion, you must first understand their limitation  
i.e. the order in which they are limiting in various feedstuffs, and second the magnitude of difference between them. The  
absence of supplemental Methionine in the sole Lysine diet (T2) reduced the methionine content of the diet below  
minimum requirement as revealed in the calculated chemical composition of the diets in table 1, resulting to poor  
performance of the birds.  
Table 2 - Performance of finisher broilers fed supplemented diets (lysine and methionine).  
Treatments  
T1 (control)  
Meth + Lys  
0.62  
T2  
(Lys)  
0.62  
T3  
Meth  
0.62  
SEM  
Parameters (g)  
Initial body weigh t (kg)  
Final body weight (kg)  
Weight gain (g/day)  
Feed-intake (g/day)  
FCR (g of feed/g of gain)  
Mortality (%)  
-
2.80a  
77.86a  
127.00  
1.63c  
0.00  
2.15c  
54.64c  
130.75  
2.40a  
0.00  
2.50b  
67.14b  
128.50  
1.92b  
0.00  
0.13  
4.59  
5.424ns  
0.12  
Mean with different superscript are significantly (p<0.05) different. FCR= Feed conversion ration; SEM=Standard Error of Mean; Ns=Not  
significant.  
Carcass and carcass cuts  
The results of carcass and carcass cuts followed the same trend with that of performance parameters. The control  
birds (T1, Lys + Meth) had significant (P<0.05) higher values for carcass parameters (including dressed weight, dressing  
percentage, breast and thigh) than the birds in treatments T2 and T3 (sole lysine and sole methionine, respectively) table  
3. The sole lysine birds (T2) had the lowest (P<0.05) values in carcass parameters mentioned above, while the sole  
methionine birds (T3) were in-between the control (Lys + meth) and the sole Lysine birds (T2) in the said parameters. The  
significant (P<0.05) higher carcass values of the control birds (Lys + Meth) over the sole lysine and sole methionine birds  
confirm the complimentary effect of the two amino acids to each other to meet specific deficiencies and enhance the  
48  
Citation: Meremikwu VN and Gboshe PN (2021). Comparative effects of synthetic lysine and methionine supplements on performance and carcass characteristics of  
finisher broilers fed corn-soybean based diets. Online J. Anim. Feed Res., 11(2): 46-51. DOI: https://dx.doi.org/10.51227/ojafr.2021.8  
productivity of birds as reported by Zhai et al. (2016). The significant (P<0.05) higher performance of the sole methionine  
(T3) over the sole lysine groups (T2) in body weight and body weight gains reflected in significant (P<0.05) higher breast  
and thigh values. This is supported by the report of Wen et al. (2014) that methionine increased the concentration of  
insulin-like growth factor in broilers with subsequent improvement in performance and breast muscle growth. The  
significant (P<0.05) lower carcass values of the sole Lysine birds (T2) in comparison to the sole Methionine birds (T3)  
could be due to the low dietary content of methionine in the sole lysine diet as revealed in the calculated chemical  
composition of the diets in table 1.  
Table 3 - Carcass and Internal organ weights of finisher broilers fed supplemental lysine and methionine  
Treatments  
T1 (control)  
Meth + Lys  
T2  
(Lys)  
T3  
Meth  
SEM  
Parameters (g)  
Pre-slaughter weight (kg)  
Dressed weight (kg)  
2.80a  
2.00a  
71.43a  
2.15c  
1.30c  
60.47c  
2.50b  
1.55b  
62.00b  
0.102  
0.104  
1.86  
Dressing percentage (%)  
Carcass cuts (% of pre-slaughter weight)  
Drumstick  
10.73  
37.67a  
12.24a  
10.89a  
9.26  
9.96  
1.96ns  
1.43  
Breast/wing  
29.13c  
11.04c  
10.04c  
34.91b  
11.96b  
10.99a  
Thigh  
0.192  
0.27  
Back  
Internal organ (% of pre-slaughter weight)  
Gizzard  
2.50  
1.09  
1.96b  
1.27b  
2.53  
1.10  
2.21a  
1.28a  
2.51  
1.10  
2.20a  
1.27b  
0.07ns  
0.026ns  
0.053  
Heart  
Liver  
Abdominal fat  
0.168ns  
Ns=Not significant; SEM=Standard error of mean.  
Table 4 - Economics of supplementation with lysine and methionine in broiler nutrition.  
Quantity/100kg of feed  
Unit cost  
Amount (N /100kg of feed)  
Ingredients  
(N)*  
T1 (Control)  
T2 (Lys)  
0.25  
0.00  
T3 (Met)  
0.00  
0.25  
T1  
T2  
375  
0
T3  
0
Lysine  
1,500  
1,500  
0.25  
375  
375  
750  
Methionine  
Total cost (N)  
0.25  
375  
375  
375  
Cost of supplementation /kg of feed (Total  
cost divide by 100) (N)  
7.50  
3.75  
3.76  
Cost/kg of feed (N)  
159.5  
1.63  
155.75 155.75  
Feed conversion ratio (FCR)  
Cost of supplementation/kg weight gain (N)  
2.40  
9.00  
1.92  
9.00  
12.25  
Cost of feed/kg weight gain(N)  
260.0  
27;87  
373.8  
40.07  
299.04  
32.05  
Relative cost of feed/kg weight gain (%)  
*(N) = Nigerian Naira (official money of Nigeria)  
Internal organs  
There was no significant difference (P<0.05) between the treatments in the sizes of the internal organs, apart from  
the liver that was significantly (P<0.05) larger in the sole lysine and the sole methionine birds in comparison with the  
control (lys + met). The significant (P<0.05) larger sizes of liver in the sole lysine (T2) and sole methionine (T3) birds could  
be due to increased metabolic activities to cope with imbalance of the amino acids. This is supported by the report of Park  
(2006) that one of the biochemical responses of animals fed amino acid imbalance diets is an increase in the activities of  
49  
Citation: Meremikwu VN and Gboshe PN (2021). Comparative effects of synthetic lysine and methionine supplements on performance and carcass characteristics of  
finisher broilers fed corn-soybean based diets. Online J. Anim. Feed Res., 11(2): 46-51. DOI: https://dx.doi.org/10.51227/ojafr.2021.8  
the enzymes involved in the catabolism of the limiting amino acid leading to increase in liver size. This is supported by the  
reports of Zaefarian et al. (2019) that increased liver size in avian is considered a positive indicator associated with higher  
metabolic activity and higher energy expenditure.  
Economics of supplementation with lysine and methionine  
The result of economics of supplementation with lysine and methionine is presented in Table 4. The birds fed the  
sole supplemented diets had about 4.18 12.2% higher cost of feed/kg weight gain than the control even though the  
cost of supplementation was higher in the control than the sole supplemented. The higher cost of feed/kg weight gain  
exhibited by birds in the sole supplemented diets (T1 and T2) could be due to poor utilization of feed by these birds. This is  
supported by the fact that the enlarged liver of the birds in the sole supplemented diets is associated with increased  
metabolic activities and higher energy expenditure (Zaefarian et al., 2019).  
CONCLUSION  
From the results of this study, it was observed that supplementation with both lysine and methionine produced significant  
enhanced effect than sole supplementation. Sole lysine supplementation produced significant (P<0.05) lower values in all  
parameters measured including performance, carcass and carcass cuts compared to sole methionine supplementation.  
Sole supplementations with either lysine or methionine caused increase in liver size. Although sole methionine  
supplementation gave significant (P<0.05) enhanced effects than sole lysine, it was concluded from this research that  
supplementation with both lysine and methionine is essential in corn-soybean meal based diet for finisher broilers to  
avoid increased catabolic activities that result to enlarged liver in the birds.  
DECLARATION  
Corresponding author  
Victoria N. Meremikwu, Ph.D., Department of Animal Science, Faculty of Agriculture and Forestry, Obubra Campus,  
Cross River University of Technology, Cross River State, Nigeria. Email: victoriameremikwu@yahoo.com.  
Availability of data  
Data can be availed to the journal upon request.  
Consent to publish  
Not applicable.  
Conflict of interest  
The authors declare that they have no competing interest.  
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Citation: Meremikwu VN and Gboshe PN (2021). Comparative effects of synthetic lysine and methionine supplements on performance and carcass characteristics of  
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Citation: Meremikwu VN and Gboshe PN (2021). Comparative effects of synthetic lysine and methionine supplements on performance and carcass characteristics of  
finisher broilers fed corn-soybean based diets. Online J. Anim. Feed Res., 11(2): 46-51. DOI: https://dx.doi.org/10.51227/ojafr.2021.8