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African Journal of Pig Farming ISSN 2375-0731 Vol. 4 (5), pp. 001-006, May, 2016. Available online at 
www.internationalscholarsjournals.org © International Scholars Journals 

 

Author(s) retain the copyright of this article. 

 

Full Length Research Paper 

  

Performance of growing pigs of different genetic 
groups fed varying dietary protein levels 

 
F.O.I. Anugwa1 and A.I. Okwori2* 

 
1
Department of Animal Nutrition, University of Agriculture, Makurdi, Nigeria. 

2
Department of Animal Production, University of Agriculture, Makurdi, Nigeria. 

 
Accepted 23 December, 2015 

 
Two feeding experiments were conducted, using a 2 x 2 factorial design, to determine the performance of two genetic 
groups of pigs fed two protein levels in each case. Each experiment was replicated three times. In the first experiment, 
24 pigs, 12 each of indigenous Nigerian pigs (LC) and Large White x Indigenous cross-breeds (LW x LC) with average 
initial weights of 7.3 and 10.2 kg, respectively, were fed isocaloric (3.1 Mcal of ME/Kg) diets containing 12 or 16% 
crude protein for seven weeks. In the second experiment, 12 Large White (LW) pigs and 12 LW x LC pigs with average 
initial weights of 12.5 and 11.8 Kg, respectively, were fed isocaloric (3.1 Mcal of ME/Kg) diets containing 14 or 18% 
crude protein for seven weeks. Overall, the LC pigs performed better than the LW x LC pigs on the lower (12%) protein 
diet while the LW x LC pigs performed better than the LC pigs on the 16% protein diet. In experiment 2, the LW x LC 
pigs performed better than the LW pigs on the lower (14%) protein diet while the LW pigs performed better than the 
LW x LC pigs on the 18% protein diet. 

 

Key words: Dietary protein, indigenous Nigerian pigs, Large-White x Indigenous cross-breeds, Large White,  
performance. 

 
INTRODUCTION 

 
The indigenous pigs of Nigeria (LC) are small sized, 
weighing about 0.5 Kg at birth and about 45.5 Kg at one 
year of age (Igboeli and Orji, 1980). Fetuga et al. (1976) 
showed that these LC pigs not only matured earlier than 
improved European and American breeds but also had lower 
percentages of lean and bone and greater propor-tions of fat 
and skin as several reports have indicated that when protein 
intake is liberal, improved European and American breeds of 
pigs such as the LW and Landrace (LD) have faster growth 
rate and better feed conversion efficiency than the 
unimproved LC pigs (Vohradsky, 1968; Ilori, 1974; Fetuga et 
al., 1976, 1977). On the other hand, limited information from 
Latin America shows that indigenous pigs of Latin America 
tend to perform better than their European and American 
counterparts under conditions of poor protein nutrition 
(Bressani, 1974).  

Fetuga et al. (1977) reported on the comparative 
responses of Large White x Landrace (LW x LD) and LC  
 
 
*Corresponding author. E-mail: abelokwori@yahoo.com. 

 
 
 
 

 
pigs to diets varying in protein level from 12 to 20% crude 
protein. Increments in dietary protein improved both rate 
and efficiency of gain of the LW x LD pigs, the best 
performance being on the 18 and 20% crude protein 
diets. For the LC pigs, the best growth rates were obtain-
ed on the lowest two protein levels of 12 and 14% crude 
protein, while crude protein levels above 16% caused a 
decline in growth rate of the LC pigs. It was the objectives 
of the present study to compare the performance of LC, 
LW x LC and LW pigs fed different dietary protein levels. 
 
MATERIALS AND METHODS 

 
Tow feeding experiments were conducted using a 2 x 2 factorial 
design involving two genetic groups of pigs and two protein levels in 
each case. 
 
Experiment 1 
 
Two isocaloric diets (3.1 Mcal of ME/Kg) having 12 or 16% crude 
protein (Table 1) were fed far seven weeks to a total of 24 barrows, 
12 barrows each of the LC and the LW x LC genetic groups. There 



 
 
 

 
Table 1. Composition of experimental diets (Experiment 1) 

 

 % of Diet 

Ingredient 12% Crude protein level 16% Crude protein level 

Maize 78.73 74.36 

Groundnut cake 2.00 14.40 

Fish meal 2.50 2.50 

Wheat middling 12.00 4.00 

Oyster shell 3.00 3.00 

Vitamin-mineral premix
a
 1.00 1.00 

Sodium chloride 0.50 0 

dl methionine 0.27 0.24 

Total 100.00 100.00 

Analyzed composition   

Dry matter (%) 96.55 97.40 

Crude protein (%) 12.03 16.40 

Ether extract (%) 9.00 10.35 

Crude fibre (%) 3.55 3.45 

Ash (%) 6.15 6.50 

Nitrogen-free extract (%) 65.82 60.70 
 

a
Provided the following in units per kg of diet vitamin A, 5280 I.U.; vitamin D3, 704 I.U.; vitamin E, 70 

I.U.; vitamin K, 3.52 mg; vitamin B12, 26 Ug; riboflavin 5 mg; niacin, 28 mg; d-pantothanic acid, 21 
mg; chlorine chloride 1,100 mg; biotin, 88 Ug; thiamine, 2.2 mg; Cu; 10 mg; Fe, 160 mg; Mn, 20 mg; 
Zn, 100 mg; Co, 2.5 mg; I, 2.5 mg. 

 
 
were six pigs in each of the four treatment combinations. The pigs 
were housed two per pen according to genetic group, on concrete 
floor pens. Thus, there were three replicates per treatment. The LC 
and the LW x LC pigs had average initial weights of 7.3 and 10.2 
Kg, respectively. Feed and water were offered ad libitum. Animals 
were weighed at weekly intervals and feed consumption was 
measured by the weigh-back technique.  

Feed samples were assayed for dry matter, crude protein, crude 
fibre, ether extract and ash by the A.O.A.C. (1975) method of 
analysis. Data on feed intake, protein intake, growth rate, feed 
conversion ratio and protein efficiency ratio were obtained and sub-
jected to a 2 x 2 factorial analysis of variance (Snedecor and 
Cochran, 1974). Comparisons of treatment means were made by 
Duncan’s multiple range tests (Steel and Torrie 1960). 

 
Experiment 2 
 
A total of 24 barrows, 12 each of the LW and the LW x LC genetic 
groups, were used in this experiment. They were housed two per 
pen, according to genetic group, an average floor pens and fed two 
isocaloric (3.1 Mcal of ME/Kg) diets containing either 14 or 18% 
crude protein (Table 2). Thus, there were four treatment combina-
tions (Six pigs per treatment) and three replicates per treatment. 
The average initial weights of the LW pigs were 12.50 and 12.41 Kg 
for those fed the 14 and 18% protein diets, respectively. Average 
initial weights of the LW x LC pigs were 12.0 and 11.58 Kg for those 
fed the 14 and 18% crude protein diets, respectively. Feeding, 
weighing, analysis of feed and statistical analysis of data were as 
described for Experiment 1. 

 

RESULTS 
 
Experiment 1 
 
The main affects  of  genetic  group  and  dietary  protein 

 

 

level on performance of pigs in Experiment 1 are summa-
rized in Table 3. 

 

Effects of genetic group 

 
The LW x LC pigs consumed 86.7 g more feed (P<0.05) 
and 12.8 g more protein (P<0.025) daily, and grew 33.4 
g/day more rapidly (P<0.01) than the LC pigs. However, 
feed conversion ratios and protein efficiency ratios did not 
differ significantly (P>0.05) between the LC and the LW x 
LC genetic groups. 

 

Effects of protein level 
 
Feed intake was not significantly (P>0.05) affected by 
protein level but pigs fed the 16% crude protein diet 
consumed 39.5 g more protein and gained 30 g more 
weight daily (P<0.01) than those fed the 12% crude 
protein diet. Feed conversion ratio was not significantly 
(P>0.05) affected by protein level but pigs fed the 12% 
crude protein diet gained significantly (P<0.01) more 
weight per gram of protein consumed than pigs fed the 
16% crude protein diet. 

 

Interactions between genetic group and protein 
levels 
 
The effects of the genetic group x protein level treatment 
combinations in Experiment 1 are given in Table 4. There 



  
 
 

 
Table 2. Composition of experimental diets (Experiment 2). 

 

 % of diet 

Ingredient 14% Crude protein level 18% Crude protein level 

Maize 76.25 72.22 

Groundnut cake 8.50 20.00 

Fish meal 2.50 2.50 

Wheat middlings 8.00 1.00 

Vitamin-mineral premix
a
 1.00 1.00 

Oyster shell 3.00 3.00 

Sodium chloride 0.50 0.50 

dl methionine 0.25 0.28 

Total 100.00 100.00 

Analyzed composition   

Dry matter (%) 95.60 96.00 

Crude protein (%) 13.78 18.16 

Ether extract (%) 10.20 11.00 

Crude fibre (%) 3.50 3.60 

Ash (%) 6.40 6.46 

Nitrogen-free extract (%) 61.72 60.78 

Metabolizable energy (Kcal/kg, calculated) 3,070.0 3,108.0 
 

a
Provided the following in units per kg of diet: vitamin A, 5280I.U.: vitamin D3, 704 I.U.; vitamin E 70 I.U.; vitamin 

K, 3.52 mg; vitamin B12, 26Ug; riboflavin, 5 mg; niacin, 28 mg; d-panthothenic acid, 21 mg; choline chloride, 1,100 
mg; biotin, 88 Ug; thiamine, 2.2 mg; Cu, 10 mg; Fe, 160 mg: Mn, 20 mg; Zn, 100 mg; Co, 2.5 mg; I, 2.5 mg. 

 

 
Table 3. Main effects of genetic group and protein levels on performance of pigs (Experiment 1). 

 

  Genetic group  Crude protein level (%) 

Parameter LC  LW x LC  S.E. 12 16 S.E. 

Daily feed intake (g) 865.0
b
  951.7

a
  31.1 910.0 906.7 31.1 

Daily protein intake (g) 122.7
a
  135.5

b
  4.1 109.5

c
 148.7

d
 4.1 

Daily weight gain (g) 308.3
b
  341.7 

a
  6.3** 310.0 

d
 340.0

c
 6.3** 

Feed (kg/gain kg) 2.81  2.84  0.12* 2.95 2.70 0.12* 

Protein efficiency ratio 2.59  2.54  0.11** 2.84
c
 2.28

d
 0.11** 

 
a,b

Means of the main effects of genetic group having different superscripts are significantly 

different (P<0.05). 
c,d

Means of the main effects of protein level having different superscripts are 
significantly different (P<0.01). **Significant genetic group x protein interaction (P<0.01).  
*Significant genetic group x protein interaction (P<0.05).

e
Protein efficiency ratio = Weight gained 

(g) protein consumed (g). 
 

 

were no significant (P>0.05) genetic group x protein 
interactions and no significant treatment effects on feed 
intake. Although protein intake different significantly 
(P<0.025) among treatments, these differences were not 
of interest because there were no significant (P> 0.05) 
genetic group x protein interactions on protein intake. 
Average daily weight gains showed significant (P<0.01) 
genetic group x protein interactions. The LC pigs fed the 
12% crude protein diet gained more weight per day 
(P<0.01) than the LC pigs fed the 16% protein diet 
whereas the LW x LC pigs fed the 16% protein diet gain-
ed more weight per day (P<0.01) than the LW x LC pigs 

 
 

 

fed the 12% protein diet.  
Average (P<0.05) genetic group x protein interactions 

were also observed in feed conversion ratios and protein 
efficiency ratios (P<0.01). The LC pigs fed the 12% 
protein diet had better (P<0.05) feed conversion ratios 
than the LC pigs fed 16% protein diet but the LW x LC 
pigs which consumed the 16% protein diet had better 
(P<0.05) feed conversion ratios than the LW x LC pigs 
which consumed the 12% protein diet. Weight gained by 
the LC pigs per gram of protein consumed was signifi-
cantly (P<0.01) higher with the 12% protein diet than with 
the 16% protein diet. But weight gained by the LW x LC 



 
 
 

 
Table 4. Treatment effects of genetic group and protein levels on performance of pigs (Experiment 1). 

 

  LC LW x LC   

 12 Crude  16 Crude 12 Crude 16 Crude   
Parameter protein level  protein level protein level protein level S.E. P 

Initial Weight (kg) 7.30  7.30 10.20 10.20   

Final weight (kg) 23.14  21.67 24.74 29.15   

Daily feed Intake (g) 876.7  853.3 943.3 960.0 44.0 (P>0.05) 

Daily protein intake (g) 105.5
c
  139.9

b
 113.5 

c
 157.5

a
 5.8 (P<0.025) 

Daily weight gain (g) 323.3
b
  293.3

c
 296.7 

c
 386.7

a
 8.9 (P<0.01) 

Feed (kg/gain kg) 2.72
b
  2.91

a
 3.19

a
 2.49

b
 0.17 (P<0.025) 

Protein efficiency ratio 3.07
a
  2.10

c
 2.61

b
 2.47

bc
 0.15 (P<0.05) 

 

 
Table 5. Main effects of genetic group and protein levels on performance of pigs (Experiment 2). 

 

  Genetic group  Crude protein level (%) 

Parameter LW  LW x LC  S.E. 14 18 S.E. 

Daily feed Intake (g) 1011.7
a
  970.0

b
  5.8** 1016.7

c
 965.0

d
 5.8** 

Daily protein intake (g) 160.6
a
  153.8

b
  1.52** 140.1

c
 175.2 

d
 1.52** 

Daily weight gain (g) 383. 3
a
  361.7

b
  5.2** 346.7

c
 398.3 

d
 5.2** 

Feed (kg/gain kg) 2.73  2.69  0.05** 2.96
c
 2.46 

d
 0.05** 

Protein efficiency ratio 2.36  2.38  0.04** 2.47
c
 2.26 

d
 0.04** 

 
a,b

Means of the main effects of genetic group having different superscripts differ significantly 

(P<0.01) 
c,d

Means of the main effects of protein level having different superscripts differ significantly 
(P<0.01). **Significant genetic group x protein interaction (P<0.01)  
Protein efficiency ratio = Weight gained (g)/protein consumed (g). 

 

 

pigs per gram of protein consumed did not differ  
significantly (P>0.05) between the 12 and the 16% protein 
diets. 

 

Experiment 2 

 
The main effects of genetic group and dietary protein 
level on performance of pigs in Experiment 2 are 
summarized in Table 5. 

 

Effects of genetic group 
 
The LW pigs consumed significantly (P<0.01) more feed 
and more protein and also gained (P<0.01) more weight 
than the LW x LC pigs. However, feed conversion ratios 
and protein efficiency ratios were not significantly 
(P>0.05) influenced by genetic group. 

 

Effects of protein level 
 
The pigs consumed more (P<0.01) of the 14% protein 
diet than they did the 18% protein diet. But pigs fed the 
18% protein diet consumed more (P<0.01) protein than 
those fed the 14% protein diet. The pigs fed the 18% 
protein diet also gained more weight and had better feed 

 
 

 

conversion ratios (P<0.01) than those fed the 14% protein 
diet. But weight gained per gram of protein con-sumed 
was more (P<0.01) with the 14% than with the 18% 
protein diet. 
 

 

Interactions between genetic group and protein level 

 

The effects of the genetic group x protein level treatment 
combinations in Experiment 2 are given in Table 6. There 
were significant (P<0.01) genetic group x protein interac-
tions in all the parameters measured in Experiment 2. 
There were no significant differences (P>0.05) in feed 
intake between the LW pigs fed 14 or 18% protein diet 
but the LW x LC pigs fed 14% protein diet consumed 
106.6 g more feed (P<0.01) per day than the LW x LC 
pigs fed the 18% protein diet. There were also significant 
(P<0.01) differences among treatments in protein intake. 
Protein consumed per pay (184 g) by the LW pigs fed the 
18% protein diet was more (P<0.01) than that (166.5 g) 
consumed by the LW x LC pigs also fed the 18% protein 
diet. Protein consumption by the LW pigs fed the 14% 
protein (139.2 g/day) did not differ (P>0.05) from that of 
LW x LC pigs also fed the 14% protein diet (141 gm/day). 
The LW pigs fed the 18% protein diet had faster rates 
(P<0.01) of weight gain and better feed conversion ratios 



  
 
 

 
Table 6. Treatment effects of genetic group and protein levels on performance of pigs (Experiment 2). 

 

 LW  LW x LC   

 14 Crude  18 Crude 14 Crude 18 Crude   

Parameter protein level  protein level protein level protein level S.E. P 

Initial Weight (kg) 12.50  12.41 12.0 11.58   

Final weight (kg) 27.85  34.62 30.62 28.40   

Daily feed Intake (g) 1010.0
a
  1013.3

a
 1023.3

a
 916.7

b
 14.1 (P<0.01) 

Daily protein intake (g) 139.2
c
  184.0

a
 141.0

c
 166.5

b
 2.2 (P<0.01) 

Daily weight gain (g) 313.3
d
  453.3

a
 380.0 

d
 343.3

c
 7.3 (P<0.01) 

Feed (kg/gain kg) 3.23
a
  2.24

c
 2.70

b
 2.67

b
 0.07 (P<0.01) 

Protein efficiency ratio 2.25
a
  2.46

b
 2.69

c
 2.06

d
 0.06 (P<0.05) 

 
a,b,c,d

Means having different superscripts differ significantly at the levels of 
probability indicated.  
Protein efficiency ratio = Weight gained (g)/protein consumed (g) 

 

 

(P<0.025) than those fed the 14% protein diet, whereas 
the LW x LC pigs fed the 14% protein diet gained weight 
faster (P<0.01) than those fed the 18% protein diet. There 
were no significant (P>0.05) differences in feed 
conversion ratios between the LW x LC pigs fed 14% 
protein and those fed 18% protein. The genetic group x 
protein interaction in protein efficiency ratio was such that 
the LW pigs gained more weight (P<0.01) per gram of 
protein consumed when they ere fed the 18% protein diet 
than when they were fed the 14% protein diet. The LW x 
LC pigs, on the other hand, gained more weight (P<0.01) 
per gram of protein consumed on the 14% protein diet 
than on the 18% protein diet. 
 

 

DISCUSSION 

 

There were significant (P<0.01) genetic group x protein 
interactions with respect to feed intake and protein intake 
in Experiments 2 but not in Experiment 1 in which feed 
intake was significantly (P<0.05) affected by genetic 
group but not by protein level and protein intake was 
significantly (P<0.05) affected by both factors. The signifi-
cant genetic group x protein interactions with respect to 
average daily weight gains, feed conversion ratios and 
protein efficiency ratios in both experiments is worthy of 
note. In Experiment 1, the LC pigs gained more weight 
and had better feed conversion ratios and protein 
efficiency ratios on the lower (12%) protein diet than on 
the 16% protein diet whereas the LW x LC pigs gained 
more weights and had better feed conversion ratios on 
the 16% protein diet than on the 12% protein diet. In 
Experiment 2, the LW pigs gained more weight and had 
better feed conversion ratios and protein efficiency ratios 
on the higher (18%) protein diet than on the 14% protein 
diet whereas the LW x LC pigs gained more weight and 
had better protein efficiency ratios on the 14% protein 
diet, although they also had better feed conversion ratios 
on the 18% protein diet. Fetuga et al. (1977) reported 

 
 

 

breed x diet interactions in daily live weight gains and 
efficiency of feed utilization for LC and LW x LD pigs fed 
protein levels varying from 12 to 20%. In that study, LC 
pigs had their fastest growth rate and best feed 
conversion ratios on the 12 and 14% protein levels 
whereas the LW x LD pigs had their best growth rates 
and efficiency of feed utilization on the 18 and 20% 
protein diets. The results of the present study are in 
consonance with these reports. Significant breed x diet 
interactions have also been reported even among 
different breeds and strains of the improved European or 
American pigs in weight gain (Bowland and Berg, 1959; 
Bayley and Summers, 1968) and efficiency of feed 
utilization (Hale and Southwell, 1967).  

Overall, the LC pigs performed better than the LW x LC 
pigs on the lower (12%) protein diet while the LW x LC 
pigs performed better than the LC pigs on the 16% 
protein diet. In Experiment 2, the LW x LC pigs performed 
better than the LW pigs on the lower (14%) protein diet 
while the LW pigs performed better than the LW x LC 
pigs on the 18% protein diet. Consequently, on all perfor-
mance parameters, the LC pigs were inferior to the LW x 
LC pigs which were, in turn, inferior to the LW pigs. 
These observations are in line with the reports of 
Cameron and Ashton (1969), Vohradsky (1968), Ilori 
(1974) and Fetuga et al. (1976, 1977). The difference in 
performance of the different genetic groups in response 
to differences in dietary protein may be related to the 
inherent differences in their ability to synthesize lean 
tissues. Fetuga et al. (1976) had shown that muscle 
development proceeded at a slower rate in the LC pigs 
compared to the LW x LD pigs, while the proportion of fat 
to lean increased rapidly with increasing live weight in the 
LC pigs. It would appear that because of the lower 
potential for growth in the LC pigs, their dietary protein 
requirement would be lower than that of the LW x LC and 
LW pigs. The tendency of the growth rate of the LC pigs 
to decrease at high dietary protein levels may, therefore, 
be related to the fact that protein levels in excess of die- 



 
 
 

 

tary requirements for optimum growth and feed efficiency 
depress growth. This has been shown to be the case in 
LW x LD pigs (Cooke et al., 1972).  

The weight gained per gram of protein consumed by 
the LC pigs and the LW x LC pigs in Experiment 1 and by 
the LW x LC pigs in Experiment 2 decreased as the 
dietary protein increased, while for the LW pigs in 
Experiment 2, the weight gained per gram of protein 
consumed increased as the level of dietary protein 
increased. These results would suggest that the 16% 
protein level probably exceeded the protein requirement 
of the LC and the LW x LC pigs while the 18% protein 
diet did not satisfy the protein requirement of the LW pigs. 
This view is supported by the evidence presented by 
Cunha (1980) which shows that feeding the finishing pig 
2 more percentage units of protein than required results 
in a decrease of 10 to 15% in the efficiency of converting 
dietary protein to tissue protein.  

Work is continuing to establish the exact protein 
requirements of the LC, LW x LC and LW pigs in order to 
achieve optimum protein nutrition and optimum 
performance of these pigs in the tropics. 
 

 

ACKNOWLEDGEMENTS 

 

The authors are grateful to Messrs H. O. Onu and E. E. 
Ndukwe for technical assistance. 

 
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