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Adverse effects of tropical climate on voluntary feed intake and

performance of growing pigs

a ,

_*

b b

Dominique Rinaldo

, J. Le Dividich , J. Noblet

a

´

Institut National de la Recherche Agronomique, Unite de Recherches Zootechniques, 97170 Petit-Bourg, Guadeloupe, F.W.I

b

Institut National de la Recherche Agronomique, Station de Recherches Porcines, 35590, Saint Gilles, France Received 24 July 1998; received in revised form 16 December 1999; accepted 31 January 2000

Abstract

Four replicates were conducted to determine the effects of tropical climate and season on voluntary feed intake and performance of pigs and their carcass characteristics at 90 kg, as compared to a control environment (CE). CE was characterized by ambient temperature of 208C and relative humidity (RH) of 75%. Under tropical climate, ambient temperature averaged 24.68C and RH 84% during the cool season (CTC) and 27.38C and 82% during the warm season (WTC) respectively. Ninety-six Large White pigs were used between 15 and 35 kg live weight (P1) and, as 36 of them were slaughtered at 35 kg, the remaining pigs were used from 35 to 90 kg (P2). In the CTC, neither voluntary feed intake, nor average daily gain, feed:gain ratio or carcass characteristics significantly differed from CE in P1 and P2 pigs. In the WTC, the 13% decline in feed intake of P2 pigs (P,0.001) induced a 13% diminution in growth rate (P,0.05). In the WTC, fat percentage of the carcass was reduced by 3.2 units (P,0.001), whereas less fat was deposited in backfat (P,0.001) and more fat retained in leaf fat (P,0.001), as compared to the CTC. Also in the WTC, the reduction in the weight of internal organs led to a 1.8 unit improvement in killing-out percentage (P,0.001). Data indicated that in the tropics, growth performance varied with the season and that during the warm season feed intake was a major limiting factor to growth rate.

Keywords: Pig-feeding and nutrition; Environment; Tropics; Feed intake; Performance; Carcass characteristics

1. Introduction systems of swine production in the tropics, could be due to various factors including the tropical climate. Growth performance of pigs reared in tropical Both high air temperature and humidity are charac-areas is often regarded as low even when balanced teristics of tropical climate in the Carribean area. diets and improved breeds are used (Egbunike, Numerous studies have shown that ambient tempera-1986). This low level of performance, which is a ture has direct effects on voluntary feed intake and major limiting factor to the development of intensive therefore performance of pigs (Verstegen et al., 1978; Nichols et al., 1982; Close, 1989). Most of these studies deal with the assessment of additional

*Corresponding author. Tel:1590-25-59-33; fax:1

590-25-59-feed requirement in the cold. Conversely, less

in-36.

E-mail address: rinaldo@antilles.inra.fr (D. Rinaldo) formation is available on the influence of warm

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conditions on growth performance in pigs, except for using the comparative slaughter method. Data on investigations concerning very high constant ambient body composition of pigs slaughtered at 35 kg live temperatures in the range of 32–358C (Holmes, weight and on energy balance are to be presented in 1973; Straub et al., 1976; Campbell and Taverner, another paper. The present one shows data on 1988). Studies on the influence of relative humidity carcass composition of animals killed at 90 kg live on productive traits in pigs are scarce (Granier et al., weight.

1998). Therefore, this trial was designed to evaluate For each of the two climatic treatments, i.e. the effects of tropical humid climate and season of tropical climate and controlled environment at 208C the year on voluntary feed intake and growth per- and 75% RH, there were two replicates within each formance of Large White pigs reared in intensive of the two seasons. For each replicate, six litters conditions. were weaned simultaneously at 2862 days of age. Within each litter, four animals, one pair of castrates and one pair of females, were chosen and entered the

2. Materials and methods experimental building. One pig of each pair was placed in tropical climate in a semi-open room and The experiment was carried out to determine the the other one in a climatic room where both air effects of tropical climate and season on voluntary temperature and humidity were controlled. Litter feed intake (FI), growth performance, organ weights mates were thus assigned to one of the two climatic and carcass characteristics of Large White growing treatments to get a balanced block design at the pigs, as compared to a control environment. There- beginning of the trial, according to litter origin, sex fore, two climatic treatments were used: tropical and live weight. Air humidity was set at 75% when climate vs. constant air temperature of 208C and air the animals got into the climatic room and then humidity of 75%. The temperature of 208C is within remained unchanged until the end of the trial. On the the thermoneutral zone of both 20 and 60 kg pigs day the piglets entered the climatic room, the am-(Verstegen and Close, 1994). The influence of the bient temperature was fixed at 288C. It was pro-season was assessed by comparing the cool part of gressively lowered to 208C over 8 days and then the year, from November to February, to the warm remained constant over the experiment. The first 2 period, from April to October, as described in Table weeks were a pre-experimental period during which 1. This experiment was conducted in Guadeloupe the pigs adapted to both diet and climatic conditions. (F.W.I., 168 Lat. N., 618 Long. W.) in a tropical The trial began after the 2 weeks adaptation period humid area. when pigs averaged 6 weeks of age and a body weight of 14.962.5 kg. Individual weights and 2.1. Experimental procedure voluntary FI of the animals were determined weekly

during the whole experimental period.

A total of 96 pigs fed ad libitum were involved in Thirty-six pigs, half of which from each climatic this trial from 15 to 35 kg live weight. Thirty-six treatment, were slaughtered when they attained 35 kg pigs were slaughtered at around 35 kg live weight live weight. In replicates 1 and 2, 12 animals were and the remaining 60 animals were killed at 90 kg, to slaughtered. They corresponded to a pair of pigs evaluate the energy balance between 35 and 90 kg chosen at random within each of the six litters. In

Table 1

Description of the experimental design

Replicate Season Dates Litters Number of pigs

slaughtered at 35 kg

1 Cool November 1994 to February 1995 6 12

2 Warm April 1995 to October 1995 6 12

3 Cool November 1996 to February 1997 6 6

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replicates 3 and 4, six animals consisting to a pair of was assessed from the weights of fat cuts and muscle pigs from each of the three litters chosen at random, percentage from the weights of lean cuts and half-were killed. The sacrificed animals half-were selected in carcass, using predicting equations (Desmoulin et al., order that the average body weight of the remaining 1988).

pigs was similar in the two climatic treatments. The

remaining pigs were slaughtered at an average body 2.2. Feeding and housing weight of 91.962.9 kg. At slaughter, the animals

were weighed after a 12 h fast, stunned, exsangui- The animals were fed ad libitum and had free nated and eviscerated. The weights of liver, heart, access to water using a nipple water drinker. Two spleen, kidneys and lungs were recorded. The full commercial diets, based on cereals and soybean and empty digestive tract was weighed. The weight meal, were provided to the experimental pigs. From of the hot carcass was determined. After a 24 h 14.962.5 to 34.763.6 kg live weight, the diet chilling at 48C, the carcass of the animals was contained 9.74 MJ Net Energy (NE) / kg and 18.3% weighed and split. The left half-carcass was divided crude protein (Table 2). From 34.763.6 to 91.962.9 into fat cuts, such as backfat, leaf fat and belly, and kg live weight, the diet supplied 9.47 MJ NE / kg and lean cuts, such as loin and ham, according to the 17.0% crude protein (Table 2).

procedure defined by Ollivier (1970). Fat percentage The pigs were individually housed in wire cages

Table 2

Composition of the diets

Ingredients (%) 15–35 kg live weight 35–90 kg live weight

Corn 32.0 48.7

Chemical composition (%) Mean s.d. Mean s.d.

Measured by chemical analysis:

Dry matter (%) 88.4 0.5 88.4 0.4

Crude protein (%) 18.3 2.0 17.0 0.5

NDF (%) 9.5 0.5 11.2 1.1

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(0.8531.50 m) with metal slatted floors and housing method. The protein content was calculated as N3 equipment was the same whatever the climatic 6.25. Neutral Detergent Fiber (NDF) and Acid treatment. Each cage was equipped with a feed Detergent Fiber (ADF) content of feed were mea-dispenser and a nipple water drinker. In the semi- sured by the Van Soest et al. (1991) method. open room placed in tropical climate, air temperature Empty body weight (EBW) was calculated as and relative humidity were measured every 60 s at follows:

two different locations using probes set at the

EBW5Live weight

animals’ level. In the climatic room, both air

tem-2(weight of full digestive tract

perature and relative humidity were regulated within

60.58C and 3%, respectively. Light and dark cycle 2weight of empty digestive tract)

in the climatic room mimicked that of the tropical

place by using an automate. Air speed was not _{Treatment effects were assessed by analysis of}

21

controlled but was lower than 0.15 m s and _{covariance using the following model and the}

gener-3 21

ventilation rate was set at 50 m h . The volume of _{al linear model (G.L.M.) procedure of S.A.S. (1994):}

3

the climatic room was 200 m .

Yijklmn5m 1Ci1Sj1R (S )k j 1Sel1L (Rm k3S )j

2.3. Analyses, calculations and statistics ₁_CS ₁_b_(X ₂_x)₁_e

ij ijklmn ijklmn

Feed samples were taken weekly. These samples where m is the adjusted mean; C, S, R, Se and L were analysed for fat content using the Soxhlet correspond to climatic treatment, season, replicate, method and for nitrogen content using the Kjeldhal sex and litter effects. In this model, CS represents the

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interaction between climatic treatment and season, x pared using the Newman and Keuls test. Feed intake is the covariable and eijklmn is the residual error. was related to body weight by regression analysis, Covariance analysis was used to adjust performance using all the data collected (n5720).

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 thei During the warm season, the probes set in the 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-Yijklmn5m 1Ei1R (S )k j 1Sel1L (Rm k3S )j _{peratures and relative humidities are shown in Figs.}

1 and 2 in relation to the period of the year. 1b(Xijklmn2x)1eijklmn

According to present data, diurnal variations in both ambient temperature and relative humidity (RH) where m, E, R, S, Se, L, x and eijklmn are as

were more marked than seasonal changes. The previously defined. The adjusted means were

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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

Feed:gain ratio 1.72 1.64 1.56 0.12 *** ** ns

35–90 kg period

Feed:gain ratio 2.51 2.43 2.50 0.16 ns ns ns

15–90 kg period

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

c

ns: Not significant; * P,0.05; ** P,0.01; *** P,0.001

d

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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).

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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

e e e

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

b

c

d

Number of days between the start of the experiment and slaughter.

e

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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: FI5793.8123.4 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: FI5856.71 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: FI5260.31 centage was found (P,0.001) whereas the relative

2 2

42.7 BW20.228 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

d d d

208C, Cool Warm

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

b

c

d

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4. Discussion widely varies with the period of the year in warm countries, in good agreement with results obtained in 4.1. Characteristics of tropical climate and Taiwan (Hsia and Lu, 1987; Lee et al., 1995). The

assessment of the level of performance in the significant 8% decline found in FI during the warm

tropics season is smaller than the 20 to 40% decrease

reported by these authors. The difference is attribut-In the tropics, the concept of season is usually able to the fact that in these experiments the differ-based on rainfalls (Berbigier, 1988). We have chosen ence in average ambient temperature between the to compare seasons on the basis of environmental two seasons was higher than in Guadeloupe, i.e. temperature, as it is well documented that ambient 10–158C vs. 2–38C in our area.

temperature is the predominent component of the During the cool season, characterized by an aver-climatic conditions in pigs (Le Dividich and Herpin, age ambient temperature of 24.68C, whatever the live 1994; Verstegen and Close, 1994). Minimal and weight of the animals, tropical climate had no effect maximal ambient temperatures recorded during the on FI and therefore growth rate of pigs, as compared test in the semi-open room were close to those to the control environment. This is in good agree-observed over 20 successive years by a weather ment with the data of Ferguson and Gous (1997) and station located 100 m away from the experimental Massabie et al. (1996) who found maximum average building, showing that climatic conditions in the daily gain to be within the temperature range of present trial were representative of tropical humid 22–268C for 13 to 30 kg pigs and 20–248C for 25 to climate in our area (Table 3). It is noteworthy that 105 kg pigs, respectively. Average daily gain and maximal and minimal temperatures recorded inside feed conversion of growing–finishing pigs were the experimental building in the semi-open room better in tropical climate during the cool season, were 1 to 28C higher than those found using a confirming that 248C should be recommended as the weather station. optimal temperature for growing–finishing pigs In the tropics, average daily gain has been as- (Massabie et al., 1996). It is noteworthy that there sessed by various authors (Canope and Raynaud, was no modification in muscle and fat percentage of 1981; Sikka et al., 1987; Ochetim, 1993) but few 90 kg pigs due to exposure to tropical climate during reliable data are available on feed intake and body the cool season. This is consistent with the fact that composition. The present trial provides figures on when pigs achieve equal rate of weight gain, carcass these criteria and thus contributes to a better knowl- fatness does not vary with the increase in environ-edge on exotic breeds genetically improved for high mental temperature in the range of 12 to 288C (Le growth rate when they are raised in a tropical humid Dividich et al., 1987; Lefaucheur et al., 1989). area. The assessment of voluntary FI was of major During the warm season, a reduction in average importance, as low productivity in warm countries is daily gain was found which may be attributable to mainly attributed to the low level of feed intake. the decline in feed consumption. This might indicate

0.75

Voluntary FI was assessed at 123 g /(kg d) during that during the warm season, FI is a major limiting

0.75

factor of growth rate in tropical areas. The decline in the cool season and 105 g /(kg d) during the

FI, calculated on an average ambient temperature warm one for 15 to 35 kg pigs. The corresponding

21

basis, was assessed at 25 g d per 18C increase in figures found for growing–finishing animals were 98

0.75

temperature between 20 and 27.38C for 15 to 35 kg and 93 g /(kg d), respectively. Present data on

growing pigs. This value was close to the range of feed consumption are close to those obtained in India

21 21

27 to 29 g d 8C previously found between 22 in young Yorkshire pigs from 10 to 35 kg live weight

and 31.58C in weaned pigs (Rinaldo and Le Di-(Sharda and Sagar, 1986) and in Guadeloupe in

vidich, 1991; Ferguson and Gous, 1997). The de-heavier Large White pigs (Christon, 1988).

crease in feed consumption recorded in growing–

21 21

finishing pigs was 39 g d 8C between 20 and 4.2. Influence of the season on growth

21

27.38C (WCT). This is lower than the 65 to 74 g d

performance in tropical climate

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Hahn, 1983; Quiniou et al., 1998) but close to the 44 constant (Straub et al., 1976; Nienaber et al., 1987)

21 21

g d 8C found by Massabie et al. (1996) in 25 to or fluctuating ambient temperature (Giles et al., 105 kg animals. The difference between authors can 1988; Lopez et al., 1991, 1994). The reduction in FI be due to various factors such as breed, body weight, and therefore the decline in energy available for body fatness and diet (Verstegen and Close, 1994; Le tissue deposition accounts for the decrease in body Dividich et al., 1997). Actually, it is known that the fatness in warm conditions (Rinaldo and Le Di-decrease in voluntary FI when ambient temperature vidich, 1991).

increases is quadratic and Quiniou et al. (1998) have

shown that the threshold above which the drop is 4.3. Influence of tropical climate and season on more marked is about 258C for 50 kg pigs. Accord- body fat distribution and organs weight

ing to our data, the decrease in feed consumption in

21 21

growing–finishing pigs was 22 g d 8C between Exposure to tropical climate during the warm

21 21

20 and 24.68C (CTC) and 68 g d 8C between season has a major influence on body fat distribution 24.6 and 27.38C (WTC). Moreover, in the present and weight of internal organs, which is somewhat study, the ambient temperature was not constantly similar to the effect of constant high ambient tem-high in the semi-open room, but diurnally fluctuated perature. The reduction in the part of fat retained in between 23.9 and 29.88C. It has been shown that external sites such as backfat and the increase in the when nocturnal air temperature is lowered in a warm part of fat deposited in internal sites such as leaf fat, environment, growing pigs partially compensate for has been previously reported in 30-kg pigs (Rinaldo the negative influence of the exposure to high and Le Dividich, 1991) or in 100 kg animals (Le temperature during day time on voluntary FI (Lopez Dividich et al., 1987) kept at constant high ambient et al., 1991; Xin and DeShazer, 1992). The lower temperature in the range of 28 to 31.58C. It has been rate in the reduction of feed consumption with the postulated that the modification in body fat dis-increase in air temperature found in the present trial, tribution reflects an adaptation to warm conditions as could thus be related to the favourable influence of heat loss is promoted through reduced thermal reduced heat stress during night time. Present results insulation (Katsumata et al., 1996). It is well docu-suggest that average ambient temperature only partly mented that increasing the air temperature over the represents tropical climate. Other climatic compo- range of 20–22 to 30–31.58C causes a decline in the nents such as reduced nocturnal temperature and weight of internal organs in growing pigs (Nienaber high air humidity may interfere. et al., 1987). According to Dauncey et al. (1983), During the warm season, the lower average daily heart weight is more likely directly influenced by gain leads to a 10 days longer period to achieve changes in environmental temperature than in FI. slaughter weight than during the cool one. This is in Conversely, the weights of other internal organs, i.e. accordance with the results of Hsia and Lu (1987) digestive tract, liver and kidney are positively corre-who showed in Taiwan that in summer, growing pigs lated to level of FI and heat production (Koong et need up to 30–40 more days to attain a slaughter al., 1982). During the warm season, the lower weight of 110 kg than in winter. We found no weights of these organs would be linked with the depressive effects of tropical climate on feed conver- reduced FI and may contribute to lower heat pro-sion, opposed to data of Christon (1988). This duction. It is however noteworthy that there is no discrepancy may be due to the fact that the pigs in information available on heat production in pigs the present experiment are leaner and therefore less grown in tropical humid climate. In the present insulated and less sensitive to high ambient tempera- study, the lower weight of internal organs during the

ture. warm season induces a significant improvement in

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Desmoulin, B., Ecolan, P., Bonneau, M., 1988. Estimation de la

well as modified body fat distribution may reflect

composition tissulaire des carcasses de porcs. INRA Prod.

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adapt-Anim. 1, 59–64.

ability of Large White pigs to tropical climate as _{Egbunike, G.N., 1986. Response of European pigs to improved} previoulsy suggested by Dede (1983) in Nigeria. It management under the humid tropical climatic conditions in

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duction on voluntary feed intake in growing pigs given

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intake is a limiting factor to pig production under

retention of growing pigs. Anim. Prod. 47, 467–474.

tropical humid climate, as assumed by Egbunike

Granier, R., Massabie, P., Bouby, A., 1998. Incidence du taux

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Holmes, C.W., 1973. The energy and protein metabolism of pigs

is limiting during the warm season, we have

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Katsumata, M., Kaji, Y., Saitoh, M., 1996. Growth and carcass

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Koong, L.J., Nienaber, J.A., Pekas, J.C., Yen, J.T., 1982. Effetcs

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A. Cleonis, P. Marival, J. Belfort, A. Bructer, A.

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