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African Journal of Pig Farming ISSN 2375-0731 Vol. 4 (7), pp. 001-005, July, 2016. Available online at 
www.internationalscholarsjournals.org © International Scholars Journals 

 

Author(s) retain the copyright of this article. 

 

 

Full Length Research Paper 

 

The growth performance of growing pigs during 

feed restriction and re-alimentation in a humid 

tropical environment 

 
S. O. C. Ugwu and A. E. Onyimonyi* 

 
Department of Animal Science, University of Nigeria Nsukka, Nigeria. 

 
Accepted 28 November, 2015 

 
Thirty two crossbred (large white x landrace) pigs were used in a 56 days restriction and 56 days re-alimentation 
study to evaluate the effect of restricting growing pigs at 90, 80 and 70% of the ad libitum feed intake of the control. 
The pigs averaged 35.23 ± 0.560 kg at the start of the study. There were four treatments (control, 90, 80 and 70%). 
Each treatment had eight pigs allotted to 2 replications of four pigs each. The pigs received a 16% crude protein 
and 12.08 MJME/kg diet. Results indicated that average daily gains (ADG) of the control pigs were significantly 
superior to the others during the restriction period. However, at the end of the 56 days re-alimentation, pigs on the 
80% and 70% feeding regime had superior ADG than the pigs on the control and 90 percent feeding regime. Data 
on the body length (BL) and height at shoulders (HS) followed the same trend as observed for ADG. Feed intakes of 
pigs were significantly affected during the restriction and re-alimentation period. There was a significant (p < 0.05) 
decrease in feed intake as level of restriction increased. Also, during re-alimentation pigs on the 70% level had the 
highest feed intake. Pigs on the 80% level of restriction had the best feed cost/kg gain values at restriction and re-
alimentation. It is concluded that restricting growing pigs at 80% of the ad libitum intake of the control yields best 
performance and economic benefit. 
 

Key words: Growth, restriction, re-alimentation. 

 
INTRODUCTION 

 
One of the major problems of food insecurity is the 
severe competition between man and farm animals for 
available food stuffs (Steinbach, 1985). The type of 
animals mostly affected are the simple stomached 
species, pig and poultry, which depend on the same food 
needed by man to survive and produce. Several reasons 
have been adduced for the short fall in food supply mostly 
experienced in developing countries and the most 
prominent appears to be the adoption of inadequate 
agronomic strategies including unsatisfactory storage 
programmes. This result in considerable loses in the field 
and after harvest such that supply of cereals and 
leguminous grains which are also the backbone of 
successful monogastric animal production is largely 
seasonal. To compound this situation is the uncontrolled  
 
 
 
*Corresponding author. E-mail: onyimonyi@yahoo.com 

 
 
 
 
 

 
rise in human population in these countries resulting in 
continual reduction in food margins for animal feedings. 
The ultimate effect is the continual increase in feed costs 
to levels beyond 70% of total cost of animal production 
(Onyimonyi and Okeke, 2004). Attempts to elevate feed 
supplies to animals in such countries mostly entailed the 
utilization of agro- industrial wastes which measure has 
largely proved not to be very effective due to availability 
and quality concerns.  

The concept of compensatory growth whereby an 
animal whose growth has been slowed by nutritional 
deprivation may exhibit enhanced growth after depriva-
tion is stopped (Wilson and Osbourn, 1960; Doyl and 
Lesson, 2005) may be a reliable option in meeting 
challenges faced by pig farmers in food deficient coun-
tries. Compensatory growth had been reported in pigs 
(Prince et al., 1983; Mersmann et al., 1987 and 
Kyriazakis et al., 1991). Prince et al. (1983) restricted pigs 
to 70 or 80% of ad libitum intake for either 2 or 4 weeks. 



 
 
 

 
Table 1. Daily feed intake feed/gain and feed cost/kg gain of growing pigs during feed restriction and 

post restriction. 
 

Parameter Control 90% 80% 70% SEM 

(i) Daily feed intake (kg/d)      

Restriction period 2.36
a
 2.18

b
 1.84

b
 1.57

c
 0.17 

Post restriction period 2.34 2.42 2.57 2.65 0.58 

Whole period 2.54 2.44 2.36 2.43 0.41 

(ii) Feed/Gain      

Restriction period 3.74 3.65 3.57 3.68 0.25 

Post restriction period 3.92 3.87 3.76 3.83 0.40 

Whole period 3.89 3.68 3.67 3.74 0.37 

(iii) Feed cost/kg gain N      

Restriction period 129.40 126.29 123.52 127.33 1.06 

Post restriction period 135.63 133.90 130.10 132.51 1.01 

Whole period 133.90 127.32 124.91 129.40 1.65 
 

abc: Row means with different superscripts are significantly different (p < 0.05). 
SEM = Standard error of a mean. 

 

 

The group restricted to 85% for 4 weeks performed the 
best. Those restricted to 70% of ad libitum intake for 4 
weeks were unable to freely compensate suggesting that 
the restriction was either too severe and/or too prolonged. 
Mersemann et al. (1987) remarked that the magnitude of 
increase in growth rate following feed restriction may well 
be affected by the change in physiological status imposed 
by the weight loss during restriction. 
 

Kyriazakis et al. (1991) observed that there were no 
significant difference in growth rate between either male 
or female pigs upon re-alimentation after feeding a low 
protein diet. The present study intends to investigate the 
extent of growth reduction in growing pigs subjected to 
feed restriction, the rate of recovery on re-alimentation 
and the benefits accruable to the farmer that may adopt 
this concept in the humid tropics where prevailing thermal 
condition may exert negative influence on growth 
performance of pigs. 

 
EXPERIMENTAL PROCEDURES 
 
This study was conducted at the pig research and teaching unit of 
the department of Animal Science, University of Nigeria, Nsukka. 
The study lasted for 16 weeks. The location has a typical humid 
tropical climate with average day temperature ranging from 28°C in 
January (Harmattan Period), July and August to 34°C in February, 
March and April (Hottest months of the year). Humidity values 
ranged from 78% (November – February) to an average of 80% 
(March – October).  

Thirty two crossbred (large white x landrace) pigs selected from 
litters of four landrace dams that farrowed within one week were 
allotted to four treatments made up of the control and three levels of 
feed restriction (90, 80 and 70% of ad libitum). The average live 
weight of the pigs was 35.23 kg at start of the restriction and they 
consisted of 16 castrates and 16 females. Each treatment 
contained eight pigs (4 castrates and 4 females) separated into two 
replicates of four pigs each housed in a pen measuring 3.2 x 2.5 m 

 
 

 
equipped with concrete feeders separated into four feeding points 
with strong wooden planks to ensure that each pig had 
uninterrupted access to its ration. The pigs were fed a 16% CP and 
12.08 MJME/kg diet made up of 20% cassava chips, 5.5% maize, 
12% spent grain, 27.5% rice husk, 20.5% palm kernel cake, 10% 
groundnut cake, 1.5% palm oil, 2% bone meal, 0.5 common salt, 
0.15 methionine 0.10 lysine and 0.25 vitamin premix.  

All pigs were weighed at the inception of the restriction and latter 
on weekly intervals. Feed intake/unit of body weight was calculated 
for pigs on the control treatment (fed ad libitum) based on which the 
restricted levels of intake (90, 80 and 70% of ad libitum) were 
determined at the same average weight. Before the commence-
ment of the restriction phase (RST), pigs were allowed one week 
adjustment period in their new pens. Thereafter, the restriction 
phase commenced and lasted for 56d. This was immediately 
followed by the re-alimentation phase (Post – RST) which lasted for 
a maximum of 56d. All pigs were fed once per day at 7 h during 
both stages. Pigs were weighed weekly in post – RST. Other 
growth measurements taken in both stages at weekly interval were 
body length (BL); as t he length of pigs body from base of tail to 
base of skull (Mersmann et al., 1987) and height at shoulder (HS) 
taken as the vertical distance from the floor of restraining cage to 
the highest point on the shoulder (Lefaucheur et al., 1991). Daily 
feed intake (Table 1) was determined as the difference between the 
amount of feed fed and the amount left over in 24 h while feed/gain 
was calculated as the ratio of feed intake over weight gain. During 
Post–RST all experimental measurements were discontinued within 
treatment when the average body weight of composite pigs reached 
100 kg. 

All data on performance of animals at RST and Post – RST were 
processed and analysed statistically according to the procedures of 
Steel and Torrie (1980) using a stats graphic computer package. 
Statistically different means were separated by Duncan’s new multi-
ple range test (Duncan, 1955) in the same package. 
 

 

RESULTS AND DISCUSSION 

 

The results of the growth performance of pigs in the two 

phases of the experiment (RST and Post – RST) are 

presented in Table 2. There were significant (P < 0.05) 



  
 
 

 
Table 2. Performance of growing pigs during restriction (RST) and post restriction (Post – RST) periods. 

 

Parameter Control 90% 80% 70% SEM 

(i) Body weight kg      

Av. Initial Body wt. (RST) 42.27 41.90 42.32 41.21  

Av. Final Body wt (RST) 76.19
a
 74.64

a
 67.15

b
 60.37

c
 0.97 

Av. Daily gain (RST) 0.62
a
 0.57

a
 0.41

b
 60.32

c
 0.03 

Av. Daily gain (Post-RST) 0.60
a
 0.62

a
 0.79

b
 0.76

b
 0.06 

Av. Age at 100kg (d) 223 225 229 240 3.25 

(ii) Body length (cm)      

Av. Initial Body length (RST) 56.13 55.92 56.21 56.87  

Av. Final Body length (RST) 77.25
a
 75.20

a
 73.31

a
 70.19

b
 2.30 

Av. Daily gain in body length (RST) 0.38
a
 0.34

a
 0.30

a
 0.23

b
 0.02 

Av. Body length at 100kg (Post-RST) 89.65 88.24 88.27 87.46 2.31 

Av. Daily gain in body length (Post-RST) 0.30 0.32 0.35 0.33 0.04 

(iii) Height at shoulder (cm)      

Av. Initial height at shoulder (RST) 41.81 42.03 42.17 41.72  

Av. Final height at shoulder (RST) 56.04
a
 55.02

a
 53.37

a
 51.80

b
 1.36 

Av. Daily gain in height at shoulder (RST) 0.25
a
 0.21

a
 0.20

a
 0.18

b
 0.02 

Av. Height at shoulder 100kg (Post-RST) 64.26 63.63 63.65 63.76 1.78 

Av. Daily gain in height at shoulder (Post-RST) 0.19 0.20 0.25 0.23 0.04 
 

abc: Mean with different superscripts in a sow significantly (p < 0.05) different. 
SEM = Standard error of mean. 

 

 

decreases in body weight (BW), body length (BL) and 
height at shoulder (BS) at RST. The average gains in BW 
(ADG), BL (ADGL) and HS (ADGH) also decreased 
significantly (P < 0.05). The control pigs were superior to 
the restricted groups in these parameters with pigs fed 
70% of ad libitum growing at the lowest rates. Growth 
reduction in pigs subjected to various levels of feed or 
nutrient deprivation has been widely reported in 
temperate climates (Owen et al., 1971; Wahlshom and 
Libal, 1983; Donker et al., 1986; Mersmann et al., 1987; 
Chiba, 1995). The extent of decrease in various 
components of body growth studied reflected the amount 
of feed made available to the restricted pigs which 
decreased significantly (P < 0.05) from control to 70% of 
ad libitum. The ADG of 80 and 70% restricted pigs (0.41 
and 0.32 kg/d respectively) were lower than 0.59 and 
0.48 kg/d reported by Prince et al. (1983) in growing pigs 
restricted to 85 and 70% of ad libitum consumption. 

The efficiency of feed conversion was generally low 
with values recorded for the restricted pigs being slightly 
lower than that of the control. Steinbach (1985) observed 
that the exogenous and endogenous heat load affecting 
pigs in the humid tropics act through the neuro endocrine 
system to alter digestibility and absorption of nutrients, 
enzyme activity and metabolism of various nutrients, 
thereby reducing efficiency of feed conversion and growth 
rate. It is therefore likely that the lower gains obtained for 
80 and 70% restricted pigs may not be as a result of the 
levels of restriction above but also involved the influence 
of prevailing environment. The pigs fed 90% of ad libitum  

 
 

 

were minimally affected by restriction with ADG values 
(0.57 kg/d) differing only slightly from that of control (0.62 
kg/d). Cleveland et al. (1983) and Mersmann et al. (1987) 
described this level as modest restriction since it caused 
reduction in fat deposition only with no change in gain of 
lean. When compared with the control, pigs fed 70 and 
80% of ad libitum respectively lost 15.82 and 9.05 kg of 
BW respectively during the 56d restriction period while 
90% restricted group lost 1.55 kg.  

A similar trend was observed in linear body measure-
ments where for BL, pigs fed 70 and 80% of ad libitum 
lost 7.06 and 3.94 cm while the 90% group lost 2.05 cm. 
For HS, 4.01, 2.44 and 1.62 cm were the losses recorded 
by 70, 80 and 90% restricted groups respectively. 
Minimal loss in BL was reported by Mersmann et al. 
(1987) for growing pigs restricted for three weeks. 
Significant reduction in BL was not recorded by these 
authors probably because of the short duration of 
restriction. It seems apparent that the pigs placed on 70% 
of ad libitum con-sumption received more severe 
treatment which resulted in significant retardation in 
growth of bone and lean tis-sue.  

Doornenbal (1975) reported that after 12 weeks of age, 
pigs exhibit rapid lengthening of the backbone which 
accounts for the increase in body length. It is therefore 
felt that severe nutritional deprivation as was the case 
with pigs given 70% of ad libitum for 56d in the tropics 

where growth rate is generally low, could delay develop-
ment of body length. Similarly, the observed drop in HS 
measurement of the 70% restricted group may also have 



 
 
 

 

been the result of the prolonged nutritional assault on the 
pigs which are in the stage (30 – 159 kg) when propor-
tionnal increases in muscle and length/diameter of the 
limb bones occur.  

The pigs exhibited different rates of recovery at Post – 
RST with 80 and 70% restricted groups recording higher 
(P < 0.05) ADG (0.79 and 0.76 kg/d) than the control and 
90% restricted groups (0.60 and 0.62 kg/d). The Post – 
RST ADG of 80 and 70% groups were twice the RST 
gains and when compared with the control, the gains 
were higher by 0.19 and 0.16 kg/d respectively. However, 
the re-alimentation growth rates reported by Mersmann et 
al. (1987) for control and restricted pigs (0.864 vs 1.005 
kg/d) were much higher than the rates obtained in the 
present study. The gains reported by Prince et al. (1983) 
for pigs fed 85 and 70% of ad lib for four weeks (0.83 vs 
0.78 kg/d) were also higher than the Post RST gains 
recorded in the present study. The 80 and 70% restricted 
groups also made up for lose in BL and HS at RST. The 
Post – RST rates of increase in BL of 80 and 70% 
restricted groups (0.35 and 0.33 cm/d) were lower than 
0.496 cm/d recorded by Mersmann et al. (1987) for re-fed 
pigs in the temperate environment. The Post – RST feed 
consumption of pigs were significantly (P < 0.05) affected 
during restriction. The highest intake was observed in the 
70% restricted group (2.65 kg/d) while the lowest was in 
the control (2.34 kg/d). Feed consumption in 80 and 70% 
groups were only a little higher than their intake at RST 
within the first week of re-alimentation but appreciated 
gradually from the second week reaching stable values 
from the third week till the end of that phase. This trend 
was not noticed in the 90% restricted group where the 
intake increased at the beginning of re-alimentation and 
following a period of feed restriction took several weeks 
to develop fully and persisted for some time. It is likely 
that the initial delay in attaining full consumption 
immediately on re- alimentation may be due to the 
inherent mechanism in pigs to adjust voluntary intake in 
response to previous restriction as earlier suggested by 
Wilson and Osbourn (1960) . It was also observed that 
feed consumption of control and restricted groups were 
low at Post – RST and through the whole period. Post – 
RST consumption ranged form 2.34 kg/d in the control to 
2.65 kg/d in 70% restricted pigs while whole period 
consumption ranged from 2.6kg/d in 80% restricted to 
2.54 kg/d in the control pigs. These rates were much 
lower than 3.26 kg/d reported by Owen et al. (1971) for 
restricted re-alimentated pigs and 3.66 kg/d reported by 
Mersmann et al. (1987) for restricted re-fed pigs in the 
temperate environment. It does appear that the generally 
low feed intake may be a defense mechanism developed 
by the pigs to cope with the high exogenous heat in the 
tropics and the resultant endogenous heat load which 
tend to increase to unmanageable levels following 
increased feed intake by pigs in this climate. Feed intake 
of exotic pigs reared in the tropics was reported to de- 

 
 
 
 

 

cline when ambient temperatures exceed 30°C 
(Steinbach, 1976). The present study was conducted in 
the late dry season when average ambient temperatures 

averaged 34
o
C condition is also felt to be partly 

responsible for the high Post – RST feed/gain which 
ranged from 3.76 in 80% restricted to 3.92 in control 
groups. These values were higher than 2.44, 2.47 and 
2.44 reported by Donker et al. (1986) for pigs of similar 
body weight fed ad libitum or re-alimented after restriction 
at 85 and 70% of ad libitum respectively in the temperate 
environment. It therefore follows that both restricted and 
ad libitum fed pigs in this environment ate more feed per 
unit gain in weight. Thus, the observed high feed/gain 
and the accompanying reduction in growth rate at both 
RST and Post – RST culminated in the observed delay in 
age at 100 kg. Contrary to 183.5d and 191.0d reported as 
extrapolated age at 100 kg for pigs fed ad libitum, 85 and 
70% of ad libitum respectively (Prince et al., 1983), the 
real age at 100 kg for control and restricted groups (90, 
80 and 70% of ad libitum) were 233d, 235d 228d and 
240d respectively. A striking finding of the present study 
is the feed cost/kg gain. Pigs on the 80% level had 
significantly better values during restriction and re-
alimentation. It follows that this level of restriction will 
guarantee better economic returns to a farmer.  

It is concluded that restricting pigs at 80% of the ad 

libitum intake of the control will ensure better perfor-

mance and superior economic returns to a farmer. 
 

 
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