D . Rinaldo et al. Livestock Production Science 66 2000 223 –234
227
interaction between climatic treatment and season, x pared using the Newman and Keuls test. Feed intake
is the covariable and e is the residual error.
was related to body weight by regression analysis,
ijklmn
Covariance analysis was used to adjust performance using all the data collected n 5720.
data to constant live weight at the beginning of the period and weights of organs and carcass characteris-
tics were adjusted to constant empty body weight.
3. Results
After making sure that whatever the season, data obtained for the control treatment were not sig-
3.1. Climatic parameters nificantly different, those data were pooled. There
were therefore three environments E , either the During the warm season, the probes set in the
i
control treatment, or the cool season in tropical semi-open room indicated that average ambient
climate or the warm season. temperature at the animals’ level was 27.38C and
The adjusted means presented here in the tables mean relative humidity was 82. The corresponding
were calculated as follows: figures during the cool season were 24.68C and 84,
respectively. Minimal and maximal ambient tem- Y
5 m 1 E 1 R S 1 Se 1 L R 3 S
ijklmn i
k j
l m
k j
peratures and relative humidities are shown in Figs. 1 and 2 in relation to the period of the year.
1 b X
2 x 1 e
ijklmn ijklmn
According to present data, diurnal variations in both ambient temperature and relative humidity RH
where m, E, R, S, Se, L, x and e
are as
ijklmn
were more marked than seasonal changes. The previously defined. The adjusted means were com-
Fig. 2. Maximal and minimal relative humidity RH, recorded at the level of the animals under tropical climate. Each point represents the mean of the data recorded over 3 successive days and is an average of the two replicates in each season.
228 D
. Rinaldo et al. Livestock Production Science 66 2000 223 –234 Table 3
Maximal and minimal temperatures 8C found during the test in the semi-open room as compared to those recorded using a weather station during 20 successive years
Warm season Cool season
Minimal temperature Maximal temperature
Minimal temperature Maximal temperature
Present trial 23.9
29.8 21.9
28.1 Weather station
21.9 28.5
19.7 27.0
difference between minimal nocturnal temperature 3.2. Growth performance of pigs between 15 and
and maximal diurnal temperature was about 68C 35 kg live weight
Table 3 and did not notably vary over the year. Maximal RH was on average 92 during night time
Data performance of young growing pigs between and mean minimal RH was 71 around midday.
15 and 35 kg live weight are shown in Table 4.
Table 4 Effect of tropical climate and season on performance of growing pigs in relation to the live weight. Data adjusted to a constant live weight at
the beginning of each period
c
Environmental conditions R.S.D.
Significance
d d
d
Control Tropical climate
C S
C3S 208C,
Cool Warm
75 RH season
season 15–35 kg period
Number of pigs 48
24 24
Feed intake
a a
b
g d 1289
1322 1108
106 ns
0.75 a
a b
g kg d
119 123
105 8
ns
ab a
b
Average daily gain g 751
805 710
60 ns
ns
a b
c
Feed:gain ratio 1.72
1.64 1.56
0.12 ns
35–90 kg period Number of pigs
30 15
15 Feed intake
a a
b
g d 2253
2154 1971
117
0.75 a
ab b
g kg d
102 98
93 6
a a
b
Average daily gain g 901
886 785
80 Feed:gain ratio
2.51 2.43
2.50 0.16
ns ns
ns 15–90 kg period
Feed intake
a a
b
g d 1983
1970 1742
152 ns
ns
0.75 a
a b
g kg d
102 102
84 10
ns ns
a a
b
Average daily gain g 853
865 789
67 ns
ns Feed:gain ratio
2.31 2.28
2.20 0.16
ns ns
ns
a
Means that do not have a common superscript letter significantly differ P ,0.05.
b
Means that do not have a common superscript letter significantly differ P ,0.05.
c
ns: Not significant; P ,0.05; P ,0.01; P ,0.001
d
C: effect of tropical climate vs. control environment; S: season effect in tropical environment; C3S: interaction between climatic treatment and season.
D . Rinaldo et al. Livestock Production Science 66 2000 223 –234
229
Tropical climate had on average a significant nega- pared to the control environment. This depressive
tive influence on voluntary FI in young pigs, which influence on feed consumption led to a 13 diminu-
was particularly marked during the warm season. As tion in average daily weight gain P ,0.05 whereas
compared to the control environment, feed consump- feed-to-gain ratio remained unaffected. Conversely,
tion was not statistically different during the cool during the cool season, neither FI nor growth rate of
season, whereas it was decreased by 14 during the pigs reared in the semi-open room significantly
warm season P ,0.001. This decline in FI did not differed from those of control animals. Present
lead to a significant change in the average daily results clearly showed that the influence of tropical
weight gain of the pigs and feed-to-gain ratio was climate on performance data was highly dependent
improved by 0.16 unit P ,0.001. Under tropical on the season of the year interaction between
climate itself, productive traits varied widely in climatic treatment and season: P ,0.01. Moreover,
relation to the season of the year. During the warm under tropical climate itself, there was a huge
season, the 16 reduction in voluntary FI P , variation in performance of growing pigs over the
0.001 resulted in a 12 decrease in growth rate year. Voluntary FI and average daily gain during the
P ,0.001, as compared to the cool season. Feed-to- warm season were lowered by 8 P ,0.01 and 11
gain ratio was the lowest during the warm season P ,0.01, respectively, as compared to the cool
P ,0.01. season.
The overall FI P ,0.001 and average daily gain 3.3. Growth performance of pigs between 35 and
P ,0.05 of pigs between 15 and 90 kg live weight 90 kg live weight and over the total period
were significantly lower during the warm season as compared to both controls and the cool tropical
Pigs fed ad libitum from 35 to 90 kg live weight season. The delayed growth rate during the warm
were susceptible to both tropical humid climate and season led to a 10 days longer period to attain similar
season Table 4. During the warm season, exposure slaughter weight than in the two other climatic
to local climate induced a 13 decline in voluntary treatments Table 5.
21
FI of growing–finishing pigs P ,0.001, as com- Within each environment, daily FI g d
of pigs
Table 5 Effect of tropical climate and season on carcass characteristics of growing pigs slaughtered at 90 kg live weight
c
Environmental conditions R.S.D.
Significance
e e
e
Control Tropical climate
C S
C3S 208C,
Cool Warm
75 RH season
season Slaughter weight kg
91.3 92.2
93.5 3.0
ns ns
ns
d a
a b
Days to slaughter 91.8
91.5 101.6
6.1 of carcass:
Muscle 55.0
54.1 53.5
1.9 ns
ns ns
ab a
b
Fat 22.2
23.8 20.6
2.6 ns
ns Including:
ab a
b
Backfat 11.1
11.5 10.0
1.4 ns
ns
a a
b
Leaf fat 1.06
1.02 1.36
0.29 ns
a
Means that do not have a common superscript letter significantly differ P ,0.05.
b
Means that do not have a common superscript letter significantly differ P ,0.05.
c
ns: Not significant; P ,0.05; P ,0.01; P ,0.001
d
Number of days between the start of the experiment and slaughter.
e
C: effect of tropical climate vs. control environment; S: season effect in tropical environment; C3S: interaction between climatic treatment and season.
230 D
. Rinaldo et al. Livestock Production Science 66 2000 223 –234
from 15 to 90 kg live weight was related to body at about 90 kg live weight Table 6. At the opposite,
weight BW, kg according to the following equa- in tropical climate, the season had direct effects on
tions: both fat content and fat location in the animals.
When pigs were reared during the warmer part of the
2
control treatment: FI 5 793.8 1 23.4 BW R 5 year, a significant reduction of 3.2 percentage unit in
0.81 fat percentage was observed P ,0.001 whereas
tropical climate, cool season: FI 5 856.7 1 muscle percentage was not significantly affected.
2
21.0 BW R 50.76; During the warm season, a decline in backfat per-
tropical climate, warm season: FI 5 260.3 1 centage was found P ,0.001 whereas the relative
2 2
42.7 BW 2 0.228 BW R 50.83 weight of leaf fat was enhanced P ,0.001.
For pigs on both the control treatment and the tropical climate during the cool season, there was a
3.5. Weight of internal organs similar linear raise in voluntary FI per kg increase in
body weight. In pigs reared during the warm season Exposure to tropical climate resulted in a decrease
in tropical climate, the relation between FI and BW in the weight of heart P ,0.001, liver P ,0.05
was curvilinear, suggesting that the susceptibility of and empty digestive tract P ,0.05, as compared to
growing–finishing pigs to warm conditions was the control environment Table 6. For the pigs
accentuated when the animals got heavier. raised in the semi-open part of the building, the
weights of liver, spleen and empty digestive tract were significantly reduced during the warm season,
3.4. Carcass characteristics as compared to the cool season. This reduction led to
an improvement of 1.8 percentage unit in killing-out Tropical climate had on average no striking in-
percentage P ,0.001 which was 84.2 during the fluence on carcass characteristics of pigs slaughtered
warmer period of the year.
Table 6 Effect of tropical climate and season on weights of internal organs and killing-out percentage of growing pigs slaughtered at 90 kg live
weight
c
Environmental conditions R.S.D.
Significance
d d
d
Control Tropical climate
C S
C3S 208C,
Cool Warm
75 RH season
season Organ weight EBW
a a
b
Heart 0.36
0.34 0.31
0.03 ns
a ab
b
Liver 1.63
1.57 1.52
0.13 ns
Kidneys 0.29
0.29 0.27
0.03 ns
ns ns
ab a
b
Spleen 0.15
0.16 0.13
0.02 ns
ns Lungs
0.58 0.57
0.57 0.10
ns ns
ns
a a
b
Empty digestive tract 5.01
5.15 4.30
0.48 ns
Killing-out percentage
ab a
b
Hot carcass liveweight 83.3
82.4 84.2
1.1 ns
ns
a
Means that do not have a common superscript letter significantly differ P ,0.05.
b
Means that do not have a common superscript letter significantly differ P ,0.05.
c
ns: Not significant; P ,0.05; P ,0.01; P ,0.001
d
C: effect of tropical climate vs. control environment; S: season effect in tropical environment; C3S: interaction between climatic treatment and season.
D . Rinaldo et al. Livestock Production Science 66 2000 223 –234
231
4. Discussion widely varies with the period of the year in warm
