246 N
. Quiniou et al. Livestock Production Science 63 2000 245 –253
available in the literature, the decrease of tempera- ture below the thermoneutral zone is associated with
an increase of VFI and body fatness at slaughter Le Dividich et al., 1985, whereas under warm con-
ditions, the VFI is decreased as well as body fatness Rinaldo and Le Dividich, 1991. However, most of
those results were obtained in conventional types of pigs and would not be applicable to lean types of
pigs as, for instance, no increase of body fatness under cold temperature was reported recently by
Massabie et al. 1996. Furthermore, little infor- mation is available to predict VFI and feeding
Fig. 1. Cyclic variation of temperature 8C over each stage of
behaviour in pigs exposed to different ambient
growth in experiments 1 and 2: - - -, adaptation; ———, measure-
temperatures Nienaber et al., 1990, 1996, especial-
ment.
ly in lean types of pigs. As the chemical composition of the body weight BW gain depends directly on
the intake of nutrients and their digestive and days at each of the following temperatures: 22, 19,
metabolic utilisation by the animals Whittemore and 16, 14 and 12
8C. Groups 3 and 4 were used to study Fawcett, 1976, it is of major interest to investigate
the effect of hot exposure and then exposed to the way that the ambient temperature affects nutrient
ambient temperatures varying from 19 to 29 8C and
utilisation and feeding behaviour in pigs. The aim of from 29 to 19
8C experiment 2 with three or four the present study was to characterise the effects of
consecutive days at each of the following tempera- exposure to cold or hot temperatures on VFI, feeding
tures: 19, 22, 25, 27 and 29 8C. The 19 and 228C
behaviour and energy expenditure of group-housed levels were considered as belonging to the ther-
growing pigs over the growing-finishing period. For moneutral zone of group-housed growing pigs.
this latter purpose, the pigs were studied in a In the second part of the study experiment 3, two
respiratory chamber with a subsequent limited group- additional groups were studied at an intermediary
size. The present paper will focus on VFI and stage of growth and exposed to the same thermic set
components of feeding behaviour. as in experiment 1 group 5 or in experiment 2
group 6; the initial BW of these pigs was 45 kg on average and the group size was four pigs.
2. Materials and methods
2.2. Animal management 2.1. Experimental design
At weaning about 28 days of age, five to six pigs In the first part of the study, voluntary feed intake
originating from different litters were selected ac- and individual feeding behaviour were measured on
cording to their BW and health status. Three weeks ´
four groups of crossbred Pietrain 3 Large White
later, at approximately 15 kg BW, they were gathered barrows studied over two consecutive stages of
in a pen. At 25 kg, four of them were moved to the growth. The initial BW was around 37 kg at stage 1
experimental unit. During the whole experiment, the and around 63 kg at stage 2. The corresponding
animals were group-housed in a pen 2.3 3 1.6 m on
group sizes were four and three pigs, respectively. metal slatted floor upon a small slurry pit. The pen
For each group, temperature varied in a cyclic way was equipped with a feed dispenser and a drinking
over 28 days a thermic set at each stage of growth station and placed into a respiratory chamber 12
3
Fig. 1. Groups 1 and 2 were used to study the m . Faeces, urine and water spillages were collected
effect of cold exposure and then exposed to ambient in a slurry pit located below the pen. The pigs were
temperatures varying from 22 to 12 8C and from 12 to
fed ad libitum a cereal based diet offered as pellets, 22
8C experiment 1 with three or four consecutive the composition of which is presented in Table 1.
N . Quiniou et al. Livestock Production Science 63 2000 245 –253
247 Table 1
electronic identification system antenna that was
Composition of experimental diet
activated by earresponders as the animal entered the
Composition g kg
station. The access to the feed was adapted to the
Wheat 220.0
size of animals with a traverse allowing only one
Barley 220.0
animal to enter. The hopper was filled up daily with
Corn 200.0
an amount of feed sufficient to meet the appetite of
Soybean meal 454 244.5
the group of pigs. The trough was continuously
Wheat bran 40.0
Oil 10.0
weighed and when the load cell detected it as
L-lysine HCl 0.5
unsteady, it corresponded to a visit. After each visit,
Dicalcium phosphate 20.0
time and amounts of feed at the beginning and at the
Calcium carbonate 10.0
end of the visit were recorded. Feed consumption per
Vitamin and trace mineral mixture 10.0
visit was calculated as the difference between the
Salt 5.0
Dry matter DM 876.0
amounts recorded just before and after the visit with an accuracy of 10 g. Ingestion time per visit corres-
Analysed chemical composition g kg of DM
ponded to the difference between the time at the end
Ash 68
and at the beginning of the visit. If the feeder was
Crude protein 208
detected as unsteady but no difference in feed
Crude fat 35
NDF 167
amount was noted after the visit, it was not recorded.
ADF 53
Water was supplied outside the feeder by a nipple
ADL 5
drinker to avoid disturbing the feed weight measure-
Starch 490
ments.
Crude fibre 42
Digestible energy MJ kg of DM 15.73
Metabolizable energy MJ kg of DM 15.07
2.4. Descriptive components of feeding behaviour
a
Net energy NE MJ kg of DM 11.24
a
Estimated from digestible energy content DE, MJ kg of DM
A single meal can occur in different successive
and chemical components g kg of DM according to the relation-
visits with short pauses within-meal intervals with-
ship proposed by Noblet et al. 1994: NE 5 0.703 3 DE 1
in which the computer can detect a steady weight. In
0.0066 3 crude fat 1 0.002 3 starch 2 0.041 3 crude protein 2
order to allow comparison with the results from other
0.0041 3 crude fibre RSD 5 0.18.
pigs or other studies carried out under various feeding conditions, successive visits were grouped
Animals had free access to water. The experiment into the same meal by using the so-called ‘meal
started after one week of adaptation to the respiration criterion’ defined as the maximum length of the
chamber environment and the diet. During this within-meal interval between visits. Then, if visits
period, the temperature was fixed at 22 8C experi-
were separated by intervals longer than the ‘meal ment 1 and group 5 in experiment 3 or 19
8C criterion’, they are considered as different meals. The
experiment 2 and group 6 in experiment 3. The ‘meal criterion’ was assessed from our data using a
relative humidity was 70. The pigs were weighed log survivorship function as described by Bigelow
at the beginning and the end of each thermic set and and Houpt 1988. A sample of 183 data obtained on
at the beginning of the 16 8C level experiment 1 and
individual pigs originating from both experiments group 5 in experiment 3 or the 25
8C level experi- and exposed to the different temperatures was ran-
ment 2 and group 6 in experiment 3. domly chosen to calculate the meal criterion. Ninety-
five percent of the individual estimated meal criteria 2.3. Equipment
were below 2 min; this value was retained for further calculations.
The pen was equipped with a single-space elec- For each pig at each level of temperature, at each
tronic feed dispenser, which consisted of a trough stage of growth and on each day of measurement, the
and a hopper connected through a load cell to a following behavioural criteria were calculated: the
computer. The feeding station was provided with an average number of visits per day; average number of
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
