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Scholars
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African Journal of Pig Farming ISSN 2375-0731 Vol. 7 (8), pp. 001-006, August, 2019. Available online at 
www.internationalscholarsjournals.org © International Scholars Journals 

 

Author(s) retain the copyright of this article. 

 

 

Full Length Research Paper 

 

Effect of low protein diets and lysine supplementation 
on growth performance and carcass characteristics of 

growing pigs 

 
A. Kumar1*, R. Bhar1, A. B. Mandal2 and S. K. Mendiratta3

 
 

1
Centre of Advanced Faculty Training in Animal Nutrition, Indian Veterinary Research Institute, 

Izatnagar – 243 122, India. 
2
Avian Nutrition and Feed Technology, Central Avian Research Institute, Izatnagar – 243 122, India. 

3
Division of Livestock Product Technology, Indian Veterinary Research Institute, Izatnagar – 243 122, India. 

 
Accepted 08 May, 2019 

 
The present study was to assess the effect of feeding low protein diet with or without supplemental lysine to meet 
NRC (1998) requirement on growth performance, carcass trait, meat composition, and meat quality of pigs. An 
experiment of 126 days was conducted on 21 crossbred Landrace pigs (average weight 11.72 ± 0.57 kg, average age 
7.59 ± 0.14 weeks). Animals were randomly assigned to three dietary treatment groups T0, T1 and T2 each comprising 
7 animals. A basal diet (T0) was formulated as per NRC (1998). Basal diet (T1) reduced crude protein by 10% with 
supplemental lysine identical in T0; while without supplemental lysine in T2 (that is, reduced protein by 10% and 
lysine by 15%). All the diets were iso-caloric and offered in phases according to change in body weight (10 to 20, 20 
to 50, 50 to 80 and >80 kg). Growth performance, carcass parameters, meat composition and meat quality were 
evaluated at the end of the trial on four animals per group. The results show no significant difference on growth 
parameters and carcass and meat quality traits among the groups. Thus, it was concluded that the crude protein 
and lysine concentration can be reduced safely by 10 and 15%, respectively to that of NRC (1998) in diet of 
crossbred Landrace pigs without any compromise on performance during growing and fattening stage of 
production. 

 

Key words: Carcass trait, low protein, lysine, meat quality, pigs. 
 
 
INTRODUCTION 

 
Proteins and amino acids play a crucial role in the 
formulation of least cost ration, as they are essential for 
the normal growth of body tissues, synthesis of 
macromolecules involved in structural, metabolic and 
functional activities, reproduction and disease resistance 
of animals (Kaur et al., 2006). The dietary provision of 
amino acids in correct amounts and proportions 
determines the adequacy of a dietary protein concentrate. 
Feeding and growing pigs with diets containing higher 
crude protein level is a metabolic and  
 
 
 
*Corresponding author. E-mail: ajitraj2k@gmail.com. Tel:  
+919319424409. 

 
 
 
 

 
economically costly process. Lysine is the first limiting 
amino acid while methionine is the second limiting amino 
acid in corn-soybean meal diet for pigs. Lysine is the first 
limiting amino acid for pigs because of two main reasons.  
First, the concentration of lysine in muscles and other tissue  
is relatively high (about 7%) and second, many of the 
feedstuffs (Maize grain, Sorghum, Wheat bran and 
Barley) commonly fed to pigs are quite low in lysine 
(Cromwell, 1996). The different advantages of adding 
lysine in the diets of pigs are protein sparing effect in pig 
diets (reduction of dietary CP level by up to 55 g/kg in 
association with adequate amino acids supplementation 
does not affect the level of performance and body 
composition of piglets; Le Bellego and Noblet, 2002); 
environmental protection (decrease of nitrogen excretion 



 
 
 

 

by 15 to 20% with protein reduction of 2% on lysine 
supplementation; Shriver et al., 2003); reducing energy 
expenditure as less energy is diverted for protein 
metabolism and elimination of excess nitrogen in the form 
of urea; reduction of feed cost, increased immune-
responsiveness, improved growth and feed efficiency and  
improved carcass trait and meat quality. Therefore,  
quantifying its requirement followed by its 
supplementation in diet through commercial synthetic 
source (L-lysine hydrochloride - 98.5%, pure L-lysine 
hydrochloride equivalent to 78.8% actual lysine) provides 
scope for reducing dietary protein supply. One of the 
major advantages of using low protein amino acid 
supplemented diet with lysine is the positive impact on 
environment. Reducing CP by 4% unit with the addition of  
amino acid markedly decreased total N excretion by 40%  
without influencing growth performance and carcass traits 
(Shriver et al., 2003). In addition, ammonia and other 
odorous nitrogenous emissions from manure are 
substantially reduced (Carter et al., 1996). The use of 
lysine supplementation is also economically viable and 
cost effective, giving higher income over feed costs (Main 
et al., 2008). Many experimental trials done in the past, 
showed positive influence of lysine supplement on growth 
performance. Average daily gain and gain: feed (G: F) 
ratio improves with increase in lysine to digestible energy 
(DE) ratio (Friesen et al., 1994; Szabo et al., 2001; Apple 
et al., 2004; Main et al., 2008). There are also some 
reports of improvement in immunity with feeding high 
lysine diets. The carcass trait and lean percentage of 
meat also improves with increase of lysine content in diet 
(Loughmiller et al., 1998; Witte et al., 2000; Szabo et al., 
2001; Main et al., 2008). Therefore, the present research 
work was conducted to study the effect of feeding low 
protein diet with or without supplemental lysine to meet 
NRC (1998) requirement on carcass trait, meat 
composition, and meat quality of growing pigs. 

 

MATERIALS AND METHODS 
 
Experimental animal and diets 
 
An experiment of 126 days was conducted on 21 (9 males and 12 
females) cross-bred Landrace pigs (average weight 11.72 ± 0.57 
kg, average age 7.59 ± 0.14 weeks) and were randomly assigned to 
three dietary groups (T0, T1 and T2). A basal diet (T0) was 
formulated (Table 1) incorporating conventional feedstuffs (maize 
grain, soyabean meal, and fish meal and wheat bran), salt, mineral 
and vitamin supplements as per NRC (1998) specifications. The 
crude protein (CP) content of the T0 was reduced by 10% with 
supplemental lysine (as L-lysine hydrochloride) to meet the 
requirement in T1; while without supplemental lysine in T2 (that is, 
reduced protein by 10% and lysine by 15%). All the diets were iso-
caloric (3400 kcal/kg DE) and offered in phases according to the 
change in body weight (10 to 20, 20 to 50, 50 to 80 and >80 kg) as 
per NRC (1998). 

 

Carcass analysis 
 
At the end of the experimental trial, 4 pigs (2 males and  2  females) 

  
  

 
 

 
per group were sacrificed to study the carcass traits and meat 
quality following standard procedure. All the animals were kept in 
liarage after arrival at the slaughter house and deprived of feed 
overnight but with free access to water. They were weighed 
immediately prior to slaughter and recorded as pre-slaughter live 
weight of pigs. The pigs were slaughtered after proper stunning at 
70 V, 250 mA by electricity. Then, bleeding by heart puncturing with 
knife and wet scalding by hot water at 65°C for 5 to 6 min were 
performed followed by scrapping and removal of hairs. Singeing 
was done by blow lamp followed by evisceration and removal of 
gastrointestinal tract (GIT), the weight was recorded as carcass 
weight. The weight of hot carcass was expressed as percent of pre-
slaughter live weight to arrive at dressing percentage. Carcass 
length was measured from the front of aitch bone to the middle of 
the front of first rib using a metal scale. Back fat thickness was 
measured at first rib, last rib and last lumbar using plastic 
measuring scale and average back fat thickness was determined by 
taking the mean of all the three values. 

 

Meat composition and quality analysis 
 
Samples of longissimus muscle were taken from the carcass after 
dissection, sealed in polythene bags and stored at -20°C for further 
analysis. Collected samples were analyzed for proximate principles 
after thawing. Moisture, fat, protein and ash contents of dissected 
longissmus muscles were determined as per the procedures of 
AOAC (1995). The pH of raw meat was determined as per the 
method described by Trout et al. (1992). Ten grams of sample were 
homogenized with 50 ml of distilled water for about a minute in Ultra 
Turrex T-18 tissue homogenizer (Janke and Kenkel, IKA Labor 
Technik, USA). The pH was recorded by immersing the combined 
glass electrode of digital pH meter (Elico, India, Model: L1 114) 
directly into the meat suspension. The water holding capacity 
(WHC) of raw meat was determined as per the method described 
by Wardlaw et al. (1973) with little modifications. Ten grams of 
finely minced meat sample was homogenized with 15 ml of 0.6 M 
NaCl in a polycarbonate centrifuge bottle for about one minute in 
Ultra Turrex T-18 tissue homogenizer. After holding for 15 min at 
4°C in order to allow the 0.6 M NaCl to reach equilibrium, the meat 
slurry was again homogenized for 1 min and immediately 
centrifuged (REMI centrifuge, T23, Sl No. GGNC 338) at 5500 rpm 
for 10 min. The supernatant volume was measured and WHC was 
expressed as ml of 0.6 M NaCl retained by 100 g of meat. Cooked 

pork chunks (from meat curry) were cut into 1.25 cm
3
 cubes. The 

cut piece was then sheared in a Warner-Bratzler Shear Press 
(Model: No. 81031307, G. R. Elect. Mfg. Co., USA). The shear 

force was recorded (in kg/cm
2
) as per the method of Berry et al. 

(1980). Ten observations were recorded for each sample to get the 
average value of shear force. 
 
 
Statistical analysis 
 
Results obtained from the study were subjected to one way analysis 
of variance (ANOVA) as described by Snedecor and Cochran 
(1989) using statistical package for the social sciences, version 
17(SPSS 17) software. The data were expressed as mean ± S.E., 
considering P<0.05 as significant. 
 
 
RESULTS AND DISCUSSION 

 

The body weight gain during the entire experimental 
period and average daily gain (ADG) are given in Table  
2. There was no statistical difference in total body weight 
and average daily gain among the dietary treatments, 



 
 
 

 
Table 1. Ingredients (% on as fed basis) and nutrient composition (as fed basis – 90.2%DM) of experimental diet as per NRC (1998) for growing pigs.  
 

Ingredients% 
 10-20 kg   20-50 kg   50-80 kg   80-120 kg  

 

T0 T1 T2 T0 T1 T2 T0 T1 T2 T0 T1 T2 
 

 
 

Maize 51.19 58.51 57.70 59.10 65.50 64.60 66.79 72.10 71.40 72.90 77.40 76.90 
 

Soyabean meal (DOC) 29.00 23.00 23.30 21.98 16.62 17.20 15.20 10.86 11.10 9.80 5.97 6.14 
 

Wheat bran 13.90 12.40 13.10 14.00 12.80 13.30 13.10 12.00 12.60 13.38 12.60 13.03 
 

Fish meal 4.00 4.00 4.00 3.00 3.00 3.00 3.00 3.00 3.00 2.00 2.00 2.00 
 

Limestone 1.20 1.20 1.20 1.20 1.20 1.20 1.20 1.20 1.20 1.20 1.20 1.20 
 

Salt 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 
 

Lysine 0.01 0.19 0.00 0.02 0.18 0.00 0.01 0.14 0.00 0.02 0.13 0.03 
 

Trace MM and Vit premix
a
 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 

 

Total 100 100 100 100 100 100 100 100 100 100 100 100 
 

Calculated nutrient composition            
 

DE (kcal/kg) 3399 3400 3399 3400 3399 3401 3400 3401 3400 3401 3400 3399 
 

CP (%) 20.94 18.78 18.77 18.07 16.16 16.24 15.50 13.94 13.95 13.25 11.88 11.88 
 

Lysine (%) 1.15 1.14 1.00 0.95 0.94 0.81 0.77 0.76 0.66 0.61 0.60 0.53 
 

True ileal dig. Lys
b
 (%) 1.01 1.01 0.87 0.83 0.83 0.70 0.66 0.66 0.56 0.52 0.52 0.44 

 

True ileal dig. Met
b
 (%) 0.31 0.29 0.29 0.27 0.25 0.25 0.25 0.23 0.23 0.21 0.20 0.20 

 

Ca (%) 0.70 0.68 0.69 0.64 0.62 0.63 0.62 0.61 0.61 0.56 0.55 0.55 
 

Total P (%) 0.63 0.59 0.60 0.58 0.54 0.55 0.54 0.51 0.52 0.49 0.47 0.47 
  

a
Trace min mix premix (0.1 kg) consisted of 10.8 g ZnO, 40 g FeSO4, 1.2 g MnSO4, 2 g CuSO4, 0.03g KI mixed as per quintal of feed and Vit premix (0.1 kg) consisted of Vitablend AD3 ( A = 50,000 IU/g, D3 

= 5000 IU/g ) and B complex vitamins. 
b
True ileal dig. Lysine and methionine of different feed ingredient calculated by multiplying analyzed lysine and methionine to corresponding digestibility values of 

ingredient NRC (1998). 
 
 
 

though, treatment T2 showed the highest 

insignificant final body weight (89.38 kg) and body 
weight gain (77.65 kg). Similar results were 
obtained by Stahly et al. (1981) and Asche et al. 
(1985), who found that the growth rate of pigs fed 
to appetite, were not significantly affected by 
dietary protein or non-essential nitrogen content 
when the levels of essential amino acids were 
adequately maintained to meet the requirements. 
Moreno et al. (2008) also observed that the 
dietary lysine to NE ratio had no effect on the 

 
 
 

 

growth performance for late-finishing pigs. On the 
contrary, a positive linear effect of lysine: DE on 
ADG was observed by Friesen et al. (1994). More 
recently, Schneider et al. (2005) and Lenehan et 
al. (2004) reported a linear increase in ADG when 
diets were provided with 0.9 to 1.3% true ileal 
digestible lysine in exotic breed with higher growth 
rate. De la Llata et al. (2007) and Main et al. 
(2008) also found that the growth performance 
improved significantly with increase of dietary 
lysine to energy ratio. Average daily gain in 

 
 
 

 

respective groups were not in accordance with the 
present study as pigs used in the study were 
crossbred Landrace pigs with low growth potential 
and thus, had lower lysine requirement. The data 
obtained during the course of the carcass and 
meat study are presented in Table 2. The pre-
slaughter live weight (kg) of pigs did not differ 
significantly among treatment groups. The hot 
carcass weights (kg) and length (cm) taken were 
comparable with highest insignificant values 
(64.07 kg and 79.25 cm) respectively for T1, 



  
 
 

 
Table 2. Growth performance, carcass traits, meat composition and meat quality of growing pigs in different dietary 
treatments (T0- Standard protein and lysine as per NRC, 1998, T1- Reduced protein by 10% and standard lysine, T2-
Reduced protein by 10% and lysine by 15%).  

 
 

Parameter 
 Treatment  

 

 

T0 T1 T2 
 

  
 

 Initial body weight (kg) 11.74 ± 1.21 11.73 ± 1.15 11.69 ± 0.71 
 

 Final body weight (kg) 85.55 ± 3.79 89.38 ± 3.72 81.87 ± 2.11 
 

 Total body weight gain (kg) 73.81 ± 3.43 77.65 ± 3.06 70.17 ± 2.05 
 

 Average Daily gain (kg) 0.59 ± 0.03 0.62 ± 0.02 0.56 ± 0.02 
 

 Average Daily feed intake (kg) 1.93 ± 0.11 1.99 ± 0.09 1.85 ± 0.05 
 

 Daily DMI (kg) 1.72 ± 0.10 1.76 ±0.08 1.64 ± 0.03 
 

 Feed : Gain 3.30 ± 0.11 3.23 ± 0.09 3.33 ±0.11 
 

 DMI : Gain 2.93 ± 0.09 2.85 ± 0.08 2.97±0.10 
 

 CPI : Gain* 0.55 ± 0.02
a
 0.48 ± 0.01

b
 0.49 ± 0.02

b
 

 

 Carcass traits    
 

 Pre slaughter live weight (kg) 93.63 ±1.34 92.88 ±2.11 89.00 ± 0.58 
 

 Hot Carcass weight (kg) 61.94 ±1.07 64.07±1.96 61.43 ±1.85 
 

 Hot Carcass length (cm) 74.00 ± 3.74 79.25 ± 1.70 74.5 ± 2.10 
 

 Average back fat thickness (cm) 2.48 ± 0.42 2.83 ± 0.34 2.82 ± 0.07 
 

 Leaf fat (kg) 1.25 ± 0.22 1.08 ± 0.17 1.49 ± 0.25 
 

 Dressing percentage 66.18±1.29 68.97±0.95 68.99±1.64 
 

 Meat composition %    
 

 Moisture 74.00 ±1.10 72.00 ± 0.83 71.90 ± 0.24 
 

 CP (N x 6.25) 22.21 ±1.23 23.72 ± 0.31 23.94 ± 0.49 
 

 EE 2.70 ±1.09 3.22 ± 0.99 3.08 ± 0.47 
 

 Ash 1.08 ± 0.06 1.06 ± 0.22 1.08 ± 0.04 
 

 Meat quality    
 

 pH 6.03 ± 0.17 6.3 ± 0.04 6.15 ± 0.03 
 

 Water holding capacity (ml/100 g) 32.5 ± 6.24 32.5 ± 4.79 27.5 ± 2.50 
 

 Shear force (kg/cm
2
) 5.53 ± 0.05 5.5 ± 0.07 5.5 ± 0.04 

  
ab

 Values in a row bearing different superscripts differed significantly (P<0.05).* P<0.05. 
 
 

 

irrespective of dietary treatments. The average back fat 
thickness (cm), leaf fat yield (kg) and dressing 
percentage also did not differ (P>0.05) due to the dietary 
treatments. These findings were in line with the 
observations of Knowles et al. (1998) and Shriver et al. 
(1999), who found similarity in carcass traits of pigs 
consuming low protein amino acid supplemented diet with 
those consuming the standard diet.  

The chemical composition (as percent on fresh basis) 
of longissimus muscle sampled from each carcass is 
given in Table 2. The mean percent moisture, protein, EE 
and total ash content of longissimus muscle showed no 
significant difference (P>0.05) among the dietary 
treatments. Castell et al. (1994) and Cameron et al. 
(1999) also did not observe any changes in longissimus 
muscle moisture content with the increase of lysine: 

 
 
 

 

energy content in swine diets. However, Goerl et al. 
(1995) reported that the moisture content in the 
longissimus muscle actually increased in response to 
increasing lysine or CP content in the diet. The CP 
content of longissimus muscle did not differ due to 
different treatments. These findings were in contrast to 
the findings of Castell et al. (1994) and Grandhi and 
Cliplef (1997) who found that protein content in 
longissimus muscle increased with increasing dietary 
lysine level or CP (Cromwell et al., 1978; Goerl et al., 
1995). Dietary energy and protein content play an 
important role in the fat and lean tissue deposition (NRC, 
1998). The numerical difference in EE is quite evident 
between the different groups giving trend of increase in 
fat deposition with decrease in protein in the diet. This 
finding is in accordance to those observed by Castell et 



 
 
 

 
Table 3. Absolute and relative weight (% BW) of trimmed lean cut & organs of pigs under different treatments (T0-
Standard protein and lysine as per NRC, 1998, T1- Reduced protein by 10% and standard lysine, T2- Reduced protein by 
10% and lysine by 15%).  

 
 

Parameter 
 Treatment  

 

 

T0 T1 T2 
 

  
 

 Pre-slaughter live weight (kg) 93.63±1.34 92.88±2.11 89.00±0.58 
 

 Carcass weight (%) 66.18±1.29 68.97±0.95 68.99±1.64 
 

 Trimmed lean cuts    
 

 Head, kg 5.67±0.36 4.94±0.36 5.31±0.36 
 

 % BW 
b
 6.06±0.38 5.32±0.13 5.97±0.15 

 

 Leg, kg 2.20±0.28 2.12±0.14 2.18±0.23 
 

 % BW 2.35±0.28 2.28±0.11 2.45±0.25 
 

 Jowl, kg 0.59±0.10 0.71±0.06 0.59±0.06 
 

 % BW 0.63±0.11 0.77±0.06 0.66±0.06 
 

 Butt, kg 4.05±0.70 4.02±0.41 4.03±0.76 
 

 % BW 4.31±0.69 4.36±0.54 4.55±0.88 
 

 Picnic, kg 4.37±0.34 4.39±0.19 4.05±0.44 
 

 % BW 4.68±0.40 4.73±0.13 4.55±0.47 
 

 Belly, kg 4.14±0.13 3.96±0.28 3.83±0.26 
 

 % BW 4.43±0.14 4.25±0.23 4.30±0.27 
 

 Ham, kg 7.21±0.34 6.95±0.09 7.00±0.37 
 

 % BW 7.69±0.31 7.50±0.25 7.87±0.41 
 

 Loin, kg 10.39±0.88 11.70±0.93 9.93±0.97 
 

 % BW 11.06±0.78 12.60±0.99 11.16±1.09 
 

 Organs    
 

 Liver, kg 1.54±0.08 1.36±0.08 1.57±0.12 
 

 % BW 1.65±0.07 1.46±0.08 1.77±0.12 
 

 Heart, kg 0.32±0.03 0.30±0.02 0.33±0.01 
 

 % BW 0.34±0.03 0.33±0.02 0.37±0.01 
 

 Kidney, kg 0.34±0.03 0.39±0.07 0.37±0.02 
 

 % BW 0.37±0.02 0.42±0.07 0.42±0.02 
 

 Spleen, kg 0.23±0.03 0.20±0.01 0.21±0.02 
 

 % BW 0.25±0.03 0.22±0.02 0.24±0.02 
 

 Lung, kg 0.80±0.13 1.01±0.16 0.82±0.14 
 

 % BW 0.86±0.15 1.09±0.18 0.92±0.16 
 

 GIT full (%) 7.69±0.59 7.41±0.94 7.51±0.39 
 

 % BW 8.25±0.71 7.93±0.86 8.43±0.40 
  

b
 Percent of pre-slaughter live body weight, (P>0.05).

 

 

 

al. (1994) and Blanchard et al. (1999). On the contrary, it 
has been reported that lean yield increased due to 
increase in lysine: energy ratio (Grandhi and Cliplef, 
1997; Szabo et al., 2001), lysine level (Dourmad et al., 
1996; Witte et al., 2000) and CP content (Cromwell et al., 
1978) in pig. The findings related to ash contents were 
similar to the findings of Goerl et al. (1995), who stated 
that increasing dietary lysine or CP had no effect on the 
proportion of ash in the longissimus muscle.  

The physico-chemical properties studied with 
longissimus muscle sampled from each carcass are given 
in Table 2. The pH, WHC (ml/100 g) and shear 

 
 

 

force (kg/cm
2
) of the muscle samples ranged from 5.6 to 

6.4, 20 to 50 and 5.3 to 5.6, respectively with no 
significant (P>0.05) difference recorded among dietary 
treatments. This finding is in accordance to earlier 
findings indicating no influence on ultimate muscle pH 
(Goerl et al., 1995; Witte et al., 2000; Szabo et al., 2001), 
water-holding capacity (Goerl et al., 1995) and firmness 
scores (Friesen et al., 1994; Grandhi and Cliplef, 1997) in 
pigs fed with diets formulating based on CP, lysine, or 
lysine: energy ratio. Absolute and relative weight (% BW) 
of trimmed lean cut and organs of pigs under different 
treatments are given in Table 3. Trimmed lean cut among 



 
 
 

 

different group did not differ significantly. The relative 
weights of visceral organs were also comparable. The 
body weight, carcass traits and yield of visceral organs 
were not affected by 10% reduced crude protein and 15% 
lysine comparable to NRC (1998). Therefore, the results 
indicate scope for reduction of protein and lysine in diets 
of crossbred Landrace pigs. 
 

 

Conclusion 

 

From the ongoing findings, it is concluded that the crude 
protein and lysine concentration can be reduced safely by 
10 and 15% respectively to that of NRC (1998) without 
any compromise on performance of the crossbred 
Landrace pigs during growing and fattening stage of 
production. 
 

 
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http://www.uky.edu/Ag/AnimalSciences/pubs/aminoacidsupplementsforpigs.pdf
http://www.uky.edu/Ag/AnimalSciences/pubs/aminoacidsupplementsforpigs.pdf

