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
ment 2 64 and 46 min d at 19 and 29 8C, respective-
ly, P ,0.001.
The effect of increased ambient temperature on the About 2 3 of feed consumption occurred during
VFI in growing-finishing pigs has been widely the day Tables 2 and 3. This proportion was neither
studied, and in a recent literature review, Le Dividich affected by temperature or by stage of growth in
et al. 1998 reported that the associated decrease of experiment 1. Under warm exposure, the diurnal feed
VFI ranged from a minimum value of 40 g 8C d to a
intake was proportionally more important at stage 2 maximum of 80 g
8C d, which depends on many 66 vs. 60 at stage 1, but no significant effect of
factors including breed, BW range, diet and, to the temperature was observed. As presented in Table 3,
highest extent, the temperature range. Even if Close the partition of meals between day and night was
1989 proposed a linear relationship between VFI significantly influenced by temperature: 69 of daily
and temperature, there is some evidence that VFI meals were performed during the day at 19
8C but varies
quadraticaly with
ambient temperature
only 55 at 29 8C. Such a difference was not
Nienaber and Hahn, 1983; the present study, the observed under cold temperatures. In addition, the
change in VFI with temperature being as important interaction between temperature and stage of growth
as the temperature is high. was significant on the diurnal partition of number of
On average between 12 and 29 8C, the estimated
meals Table 3. The decrease of the proportion of decrease of VFI with each increase of 1
8C in diurnal meals between 19 and 29
8C was more temperature would be 38, 51 and 49 g
8C d on
N . Quiniou et al. Livestock Production Science 63 2000 245 –253
251
average in 60 kg pigs according to the equation suggested by Holmes and Close 1977. From the
obtained in the present study or by Nienaber and proposed equation, it can be calculated that the
Hahn 1983 and Close 1989, respectively. Apart decreases in VFI between 19 and 29
8C were 48 and from an eventual effect of genotype on appetite,
77 g d 8C in 45 and 75 kg pigs, respectively, while
Nienaber and Hahn 1983 and Close 1989 used between 22 and 12
8C, the increases in VFI were 7 data obtained either on individually- or pair-housed
and 36 g d 8C in 45 and 75 kg pigs, respectively. In
animals, whereas group-size was four or three pigs in fact, these values indicate the highly detrimental
our study. According to Nienaber et al. 1991, four effect of high temperatures on heavier pigs and the
pigs per group would be the minimal number of inability of light pigs to increase their VFI at low
animals needed to facilitate huddling under cold temperatures, probably because of their limited gut
exposure. Then, the effect of low temperatures on capacity.
VFI would be markedly increased in smaller group- According to our results, the daily number of
size. This hypothesis could explain the differences in meals remained constant under the temperature range
slopes between our study and those of Nienaber and studied, whereas meal size seemed to decrease with
Hahn 1983 and Close 1989. However, these increased temperature. These results are in agree-
slopes are not very far from the decrease in VFI with ment with data obtained in group-housed pigs under
increased temperature 17–28 8C observed in more
hot conditions by Nienaber et al. 1993. However, practical conditions, i.e. 50–40 g
8C d according to in individually kept pigs, Nienaber et al. 1990
Massabie et al. 1996 in 25–105 kg group-housed showed that increased VFI under cold temperature
barrows and gilts, respectively. resulted from an increase of daily number of meals,
Through the covariance analysis, our study indi- whereas their size and duration were kept constant.
cates a significant interaction between BW and Yet, in individually kept pigs, no huddling behaviour
temperature on VFI, which was also reported by can occur to reduce cutaneous heat losses. In such
Close 1989. In practical terms, the interaction case, a higher meal frequency is associated with
found between temperature and BW means that the higher physical activity that induces a specific heat
heavier the pigs are the more they are sensitive to hot production.
ambient temperatures Fig. 2. Such a result would According to our results, under hot exposure,
be consistent with a decrease of the upper critical ingestion time per day was reduced as well as the
temperature of pigs with increasing BW as already occupation time of the feeding station. But when
ingestion time and consumption time obtained in our study are compared, it appears that the non-eating
activity in front of the trough averaged 17 min d when ambient temperature was below 27
8C, whereas at 27 and 29
8C, this activity was reduced to 13 and 10 min, respectively. As physical activity is associ-
ated with a high heat production in the pigs Noblet et al., 1993, the lower duration of non-eating
activity under hot exposure could be interpreted as an adaptation to high temperatures.
The increase of BW influenced components of feeding behaviour in experiments 1 and 2 as well. As
already reported by Auffray and Marcilloux 1980, Bigelow and Houpt 1988, Nienaber et al. 1990
Fig. 2. Variation of voluntary feed intake VFI, g d with
and Labroue et al. 1995 on group-housed or single-
temperature T, 8C and body weight BW, kg calculated using
housed pigs, the increase of BW was associated with
the equation:
a decreased number of meals per day, whereas
2 2
ingestion time remained about constant. Concomi-
VFI 5 21264173.6BW20.26BW 1117T22.40T
20.95T 3BW.
tantly, in all studies, the duration of each meal and
252 N
. Quiniou et al. Livestock Production Science 63 2000 245 –253
the rate of feed intake increased, which resulted in a moregulation. Under hot temperatures, decreased
higher meal size and an increased total feed intake. VFI is inexorably associated with decreased per-
The rate of feed intake was slightly higher in formance. The decrease or increase in feed intake
experiment 2 than in experiment 1, which would be under hot or cold exposure, respectively, occurs
in agreement with Nienaber et al. 1991 who mainly through changes in meal size rather than in
observed a lower rate of feed intake when tempera- daily number of meals. Then, the question arises on
ture was 12 8C below than 48C above the lower
the mechanisms implied in determination of meal critical temperature. Such a difference could be
size. It could be limited by short-term thermic effect explained by a decrease in the rate of feed intake
of feed under hot exposure as internal heat expendi- during the last visits belonging to the same meal
ture is reduced in such conditions. Under cold when its size increased markedly and almost reached
exposure, meal size would rather be determined by the maximum gut capacity of the pig.
stomach capacity than by heat dissipation. However, The feeding behaviour of confined pigs studied in
metabolic control of voluntary feed intake is com- the present experiment was mainly diurnal as more
plex and more knowledge is required to characterise than 62 of feed intake occurred during the day.
the effect of ambient temperature on the metabolic This partition is close to the value obtained by
pathways involved in feeding behaviour. Auffray and Marcilloux 1980 and by Bigelow and
Houpt 1988 in individually kept pigs 64. In group-housed pigs, Labroue et al. 1995 reported a
Acknowledgements
higher proportion of VFI during the day 75. Opposing those studies but in agreement with
The authors gratefully acknowledge A. Roger, F. ¨
Nienaber et al. 1990, our results show that the Le Gouevec and S. Daniel for their technical assis-
average proportion of diurnal feed intake did not tance.
increase markedly with BW. However, the low number of pigs per group may contribute to the
constancy of the diurnal partition of VFI. Indeed, it
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5. Conclusion
