248 N
. Quiniou et al. Livestock Production Science 63 2000 245 –253
meals per day; average feed intake per day g; The proportion of diurnal feed intake was calculated
average total ingestion time per day min, defined as for each group at each thermic level as the ratio
the total duration of all the visits performed during between the mean diurnal and mean total feed intake.
the day; average total time of feed consumption The response of VFI to temperature and BW and
min, defined as the sum of ingestion time plus their interaction was studied from the combination of
within meal intervals; average rate of feed intake all individual data obtained at each temperature level
g min, defined as the feed intake per day divided and at each stage of growth in experiment 1 N
5 by the total ingestion time; average feed intake per
120, experiment 2 N 5 120 and experiment 3 N 5
meal g and the average total ingestion time per 56. A covariance analysis was performed with the
meal min, defined as the total duration of the visits group within stage of growth as a fixed effect and
belonging to the same meal. Behavioural criteria temperature, BW and their interaction as covariates.
were also estimated over the day and the night separately. In fact, over the three or four consecutive
days at each temperature level, only the individual
3. Results
feeding behaviour calculated over the two or three last ones were used for further analysis of data.
The average daily gain was 980 and 950 g d in Indeed, during the first day at each temperature, the
experiments 1 groups 1 and 2 and 2 groups 3 and ambient temperature decreased or increased by 2 or
4, respectively. A problem occurred during fulfilling 3
8C over 4 h and this day was dedicated to adapta- the trough at one of the 19
8C levels studied over the tion to the new temperature.
first stage of growth, both in experiments 1 and 2. Consequently, number of observations reported in
2.5. Statistical analysis Tables 2 and 3 was lower at this temperature. When
exposed to 19 and 22 8C, the VFI of pigs was higher
Data from experiments 1 and 2 were used to in experiment 2 than in experiment 1 2.40 vs. 2.31
characterise the effects of temperature and BW on kg d on average, respectively; the mean BW was
the components of feeding behaviour. Results of also slightly higher in experiment 2. Then, separated
experiment 3 only one intermediary stage of growth variance analyses were performed on data originating
was considered were introduced in the data set in from each experiment.
order to establish an equation for prediction of VFI The mean BW over the two stages of growth
from temperature and BW: 120, 120 and 56 in- studied was 47 and 74 kg in experiment 1 and 49 and
dividual data were obtained in experiments 1, 2 and 76 kg in experiment 2. The increase of BW between
3, respectively. stages of growth was associated with a decreased
Taking into account social facilitation occurring daily number of meals
23.6 and 2 2.1 in experi- among group-housed pigs Hsia and Wood-Gush,
ments 1 and 2, respectively, the sizes of which 1983, components of feeding behaviour were calcu-
increased similarly in both experiments Tables 2 lated for each group at each temperature level over
and 3. As a consequence, the VFI increased with each stage of growth, as the average of the four
increased BW but to a lesser extent in experiment 1 stage 1 or three stage 2 individual values obtained
1 0.49 kg d than in experiment 2 1 0.63 kg d. at this temperature ascending or descending. When
At thermoneutrality, i.e. at 19 and 22 8C, the data of
the information was not available for one pig at one both experiments were used to assess the relationship
of the two thermic levels, then its data were not between VFI VFI
, g d and BW kg. The
19 – 22
taken into account at this temperature. From the data covariance analysis indicates that the effect of BW
obtained in experiments 1 and 2, 34 mean values on VFI was not linear:
were calculated in each experiment and used to test the effects of temperature, stage of growth and their
2
VFI 5 55.36 BW 2 0.251 BW RSD 5 353
19 – 22
interaction through an analysis of variance GLM, SAS, 1990. The effect of the group was also
introduced in the model within each stage of growth. On average, the rate of feed intake was 10 g min
N . Quiniou et al. Livestock Production Science 63 2000 245 –253
249 Table 2
a
Effect of cold temperatures and stage of growth on components of feeding behaviour
b c
Temperature 8C
Stage of growth RSD
Statistical analysis 12
14 16
19 22
1 2
Number of observations 4
8 8
6 8
16 18
– –
Mean body weight kg 61
61 61
61 61
47 74
10 S
Mean components of daily feeding behaviour per pig Number of visits
78 68
73 72
70 83
61 15
S, G Number of meals
10.7 10.6
11.5 11.3
11.5 12.9
9.3 1.9
S Feed intake kg
2.53 2.46
2.45 2.39
2.22 2.17
2.66 0.3
S Total ingestion time min
75 78
69 69
60 73
67 7
T , S, G Total consumption time min
100 93
85 84
76 90
85 10
T , G Rate of feed intake g min
35 33
37 37
38 31
42 5
S Characteristics of the meal
Feed intake g 272
262 236
228 225
183 306
50 S
Consumption time min 10.7
9.6 8.1
8 7.4
7.7 9.9
1.4 T , S, G
Diurnal feeding behaviour of total
Number of meals 65
66 65
66 68
66 66
5 G
Feed intake per day 63
60 59
62 63
61 62
6 G
Ingestion time 66
64 61
62 65
65 63
8
a
Experiment 1, adjusted means.
b
Residual standard deviation.
c
From analysis of variance with temperature T , stage of growth S , T 3S interaction and group within stage of growth G as main
effects. Each observation corresponds to the mean of four or three individual values obtained within each group at each stage of growth at each of the two thermic levels one at 12
8C within the experimental scheme designed. Statistical signification: P
,0.001, P,0.01, P,0.05.
2
higher at stage 2 than at stage 1 P ,0.001. Taking
VFI 5 2 1264 1 73.6BW 2 0.26BW 1 117T
2
into account the difference in VFI between stages, it 2 2.40T 2 0.95T 3 BW RSD 5 329
resulted in a comparable total ingestion time at both stages of growth Tables 2 and 3. The change of
ambient temperature was associated with a variation The ambient temperature did not influence the
in VFI. In experiment 1 Table 2, despite a non- number of meals per day whichever the experiment
significant difference among treatments, when the concerned Tables 2 and 3. In experiment 1, meal
temperature decreased, VFI increased significantly size was not significantly affected by temperature but
from 2.20 kg d at 22 8C to 2.53 kg d at 128C. No
the highest 272 g and the lowest 225 g values significant interaction was found between tempera-
were observed at 12 and 22 8C, respectively. When
ture and BW on this criterion. In experiment 2 Table temperature increased from 19 to 29
8C experiment 3, the increase of temperature from 19 to 29
8C 2, no significant effect of temperature was found on
induced a significant decrease in VFI 2.40 vs. 1.82 meal size 242 g meal on average, the lowest value
at 19 and 29 8C, respectively. Covariance analysis on
being observed at 29 8C 205 g meal. In both
the data from experiments 1, 2 and 3 indicates that experiments, the meal duration increased with a
the effects of temperature T, 8C and BW kg on
decrease in temperature P ,0.01 in experiment 1
VFI g d were both quadratic with a significant and P
50.06 in experiment 2. On average, the rate interaction between both factors. Between 12 and
of feed intake was 36 and 39 g min in experiments 1 29
8C, the equation was: and 2, respectively. No effect of temperature was
250 N
. Quiniou et al. Livestock Production Science 63 2000 245 –253 Table 3
a
Effect of hot temperatures and stage of growth on components of feeding behaviour
b b
Temperature 8C
Stage of growth RSD
Statistical analysis 19
22 25
27 29
1 2
Number of observations 6
8 8
8 4
16 18
– –
Mean body weight kg 63
63 62
62 62
49 76
9 S
Mean components of daily feeding behaviour per pig Number of visits
63 66
66 58
50 59
62 7
T , G Number of meals
11.2 11.3
9.8 9.9
10.1 11.5
9.4 1.6
S, G Feed intake kg
2.40 2.39
2.30 2.10
1.82 1.89
2.52 0.27
T , S, G Total ingestion time min
64 63
59 55
46 57
58 6
T Total consumption time min
81 81
76 68
56 70
75 7
T Rate of feed intake g min
39 38
40 39
40 34
44 4
S, G Characteristics of the meal
Feed intake g 248
247 271
241 205
179 306
47 S
Consumption time min 8.5
8.2 8.8
7.6 6.2
6.7 9.0
1.4 S, G
Diurnal feeding behaviour of total Number of meals
69 68
61 55
55 60
63 5
T , T 3S
Feed intake per day 65
65 64
60 62
60 66
5 S, G
Ingestion time 66
67 65
61 62
61 67
5 S
a
Experiment 2, adjusted means.
b
See Table 2. Each observation corresponds to the mean of three or four individual values obtained within each group at each stage of growth at each of the two thermic levels one at 29
8C within the experimental scheme designed.
found on the rate of feed intake under hot exposure important during stage 1 from 68 to 49 than
or under cold exposure. The ingestion time increased during stage 2 from 70 to 62.
with decreased temperatures in experiment 1 60 and 75 min d at 22 and 12
8C, respectively, P,0.05 and it decreased with increased temperatures in experi-
4. Discussion
