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The effect of temperature and relative humidity on the gastrointestinal motility of young broile
C‘omp. Buwhem. Ph,swl. Vol. 8OA. No. 4. pp. 481-486, 1985
(
Printed m Great Biitain
THE
EFFECT
OF TEMPERATURE
HUMIDITY
JOSEP of Animal
RELATIVE
ON THE GASTROINTESTINAL
MOTILITY Department
AND
0300-9629185 $3.00 + 0.00 1985 Pergamon Press Ltd
OF YOUNG A.
Physiology,
TUR
and RUBEN
BROILERS V.
RIAL
Faculty of Sciences, University Balearic Islands, Spain (Rewired
of Ciutat
de Mallorca.
22 June 1984)
Abstract-l. The effects of exposing &day-old broilers to different temperatures (22, 34. 4O’C) and relative humidities (25. 50. 75. 90”/:) on the GI motility has been measured by means of ‘YJ-polyethylene glycol-4000. 2. Chick digestive tract motility was unfavorably influenced by the lowest studied temperature (22”C), being increased at the oesophagus-crop, and being reduced at the remaining digestive tract. This effect was imputed to cold stress. 3. The highest studied temperature (4o’C) reduced the chick GI motility, along the whole digestive tract. 4. From all the studied temperatures, 34-C could be considered the optimum for the digestive motility in chickens. 5. The relative humidity (r.h.) could be considered as a factor of chick thermal comfort, after its observed effects on the GI motility. 6. The r.h. effect, measured at fixed temperature (34’C), resulted in maximal motility for oesophaguscrop at 75”, of r.h., whereas for muscular stomach this maximum was achieved at 50”; of r.h. 7. The highest r.h. (901/J produced the lowest values of chick GI motility.
INTRODUCTION
On the other hand, maximum growth of chicks and optimal efficiency of food utilization were obtained (Barrott and Pringle, 1947, 1949, 1950, 1951) when temperature was kept at 34°C at the start, and then decreasing uniformly at the rate of O.S”C/day, until 19°C for the 32 day-old chickens. Concerning the relative humidity, it has known a limitant effect on the heat loss mechanisms, sweating or panting. Consequently, in high hot-humid environments only behavioral thermoregulation is possible. However, a lower metabolism was found in Emberiza hortuluna (Wallgren, 1954) when these birds were placed in high relative humidity environment. These results were not confirmed in hens (Whittow, 1968). In this context, the aim of this paper is to study the effect of temperature and relative humidity (r.h.) on the gastrointestinal (GI) motility, in early stages of the chick life.
The digestive tract plays a fundamental role concerning the adjustment of the organism to a variety of environmental conditions. According to temperature, this function is specially important in homeotherms. However, the effects produced by thermal changes on the gastrointestinal function have been scarcely studied. In dogs, the influences of environmental temperature on gastric emptying has been found (Carlson, 1916; Sleeth and Van Liere, 1937). Generally speaking, low temperatures increased, and high temperatures slowed tone and motility in the starved stomach. On the other hand, a reduction in gastric motility and secretion was found in relation to fever (Meyer and Carlson, 1917; Bard, 1928; Blickenstaff and Grossman, 1950). In addition, a well established correlation is known between food intake and temperature (Whittow. 1968), decreasing the first and increasing the latter. These relations between thermal environment and nutritive function are particularly interesting in young animals, where the digestive tract has to assume its full activity with an abrupt onset, while the full homeothermic capacity is not attained until weeks after hatching. A high sensitivity to environmental temperature was found in baby chicks (Randall, 1943; Moreng and Shaffner, 1951), and later, when young chicks were maintained at 2435°C and the feed at an environmental temperature of 8°C (Huston, 1965), the animals would not leave the hover long enough to eat and drink sufficiently. This proved that temperature was more important to them than eating.
MATERIALS
AND METHODS
Broilers of both sexes. Arbor Acres strain (hybrid of 3 Cornish x 0 White Rock), 81.3 to 83.1 g, and 8 days old were used. From hatching they were maintained under controlled conditions of temperature, relative humidity, and photoperiod (12/12 hr dark-light schedule), in a climatic chamber Heraeus Viitsch VTPH 5/1000, and receiving water and food (standard commercial diet) ad libifum. Temperature
and r&tire
humidi!,
To study the motor function in the digestive tract as to be influenced by temperature and relative humidity, seven groups of 40 animals were studied under the environmental characteristics showed in Table 1. 481
482
JOSEP A. TUR and RUBEN V. RIAL procedure to study the etTect of temperature and relative humidity on the chick GI tract motility
Table I. Experimental
Experiment
Effect
Relative
Temperature
Humidity
22oc
75%
34°C
75%
40°C
75%
of
Temperature
Effect
34oc
25%
34oc
50%
of
Relative 34oc
75%
34°C
90%
Humidity
The experimental temperatures of 22 and 4O’C were chosen to be slightly under the lethal limits, and the third so as to be very close to the optimal temperature (Randall, 1943; Barrott & Pringle, 1947, 1949, 1950, 1951; Moreng and Shaffner, 1951). For the relative humidity experiments, a 75% of r.h. was considered as the optimum. according to Dobson et al. (1970). Measure
qf the gastrointestinal
motility
To study the effects of different temperatures and relative humidities on the GI motility, the movement of a nonabsorbable indicator, ‘+‘C-polyethylene glycol-4000 (‘4C-PEG-4000). along Ihe chick digestive tract (Tur et al., 1982) was studied. This isotope (specific activity = 21.7 mCi/g, Radiochemical Centre, Amersham, Great Britain) was mixed with polyethylene glycol-4000 (Sigma Chemical Co., St Louis, MO, USA) and dissolved in phosphate buffer (PO,H,Naj PO,HNa,. pH 7.26) at a concentration of 0.77mg/ml, resulting in a final activity of 0.08 pCi/ml. The radioactive solution was mixed additionally with 2% of methylcellulose, which provided a controlled viscosity of 0.458 cN s. mm>. For each temperature or relative humidity experiment 40 animals were used, divided into four subgroups of 10 animals according to the time of their sacrifice. Each animal received, through oral cannula, 1 ml of the mentioned radioactive solution. After 0.5, 1, 2 and 4 hr the animals were killed by chloroform inhalation. The digestive tract was then dissected, and eight sections were made according to the procedure described by Goiialons et al. (1982, 1983). The contents of each segment were extracted by maceration in IOml of distilled water. After maceration, the extract was centrifuged at 3500 rpm 20 min (1200g approx.) and I ml of the supernatant was submitted to 80°C for dryness into a scintillation vial. This dry extract was diluted in 15 ml of liquid scintillation cocktail, and its activity was measured by liquid scintillation spectrometry (Intertechnique Liquid Scintillation Spectrometer, Model SL 30). A counting time of 1 min was used for each vial, and quenching corrections were made by means of the channel ratio method. Analysis
of the results
The radioactivity present in each digestive segment was expressed as a percentage of total radioactivity recovered from the entire GI tract. Emptying Percentage (EP) and Transit Ratio (TR) were determined for each segment, according to Reynell and Spray (1956) definition, and Emptying half time (T,,), which
was calculated by interpolation after plotting the averaged values of EP against time, and drawing the regression line. Statistics Parametric statistics (analysis of variance) were used for signification of results in the studies of ‘%Y-PEG-4000 recovery, EP, and TR. In addition. SEM was used in the graphic expression of the results. RESULTS
The percentages of recovered “C-PEG-4000 as influenced by temperature at 0.5. I, 2 and 4 hr after marker administration, and expressed for each of the eight considered segments are presented in Fig. 1. The statistical differences between the different temperatures show that this environmental parameter modified the percentages recuperated from the eight gastrointestinal segments, in a variable form. The lowest progression rate of intraluminal contents was found at environmental temperature of 40°C. At 22”C, the results are similar except in the first segment (oesophagus and crop), which has the lowest recuperation. Besides these results, the segments 2 (proventriculus) and 4 (duodenal loop) showed always and for every experimental temperature, very low recuperation indexes. The percentages of recovered ‘%PEG-4000 as influenced by relative humidity (r.h.), at 0.5, 1, 2 and 4 hr after marker administration, and expresed for each of the eight considered digestive segments are presented in Fig. 2. These results show that the r.h. partially modified the recuperated radioactivity percentages. In fact, 90% of r.h. produced the highest recuperation, whereas at 75”/, of r.h. segment 1 (oesophaguscrop) produced constantly the lowest recuperation. In the same way, for segment 3 (muscular stomach) the lowest recuperation was obtained at 50% of r.h. Similarly to the temperature experiments, segments 2 and 4 produced very low recuperations at every r.h. value. The effects of temperature and relative humidity on the Emptying half time (T,,,) are presented in Fig. 3. T,, has been calculated for all digestive segments, except for those in which their T,, was shorter than the minimum measured time (0.5 hr), being also the
Temperature
: 3
2h: 6 7 8
and relative
humidity
L h
483
effect on chick GI motility
. . .. ..
Fig. 1. The effect of temperature on the recovered radioactivity (%) f SEM, at 0.5, 1, 2 and 4 hr, along the chick GI tract: (1) Oesophaguwxop; (2) prorwntriculus; (3) muscular stomach; (4) duodenal loop; (5) small intestine part I Cjejunum); (6) small intestine part II (ileum); (7) terminal ileum-caeca-rectum; (8) cloaca and feces. (*P < 0.05; **P < 0.01).
Zh
Fig. 2. The effect of relative humidity on the recovered radioactivity (7;) f SEM, at 0.5, I, 2 and 4 hr, along the chick GI tract. Digestive segments are represented by means of the same symbols of Fig. 1. (*P < 0.05: **p < 0.01).
484
JOSEP A. TUR and
T,,
(h)
RUBEN V. RIAL
Tso (h)
9
L
22'C
0
34'C
n
4O'C
a
9
h 5
aAll 12
3
4
5
6
7
digestive
tract
segment!
Fig. 3. The effect of temperature and relative humidity on the Emptying half time (T,,) + SEM the different chick GI segments. Digestive segments are represented by means of the same symbols Fig. 1. (*P < 0.05; **P < 0.01).
EP obtained at these short times clearly non linear, which would produce nonsignificant results when interpolations would be attempted. These results are a confirmation of those presented in Figs 1 and 2. So, in temperature experiments, both 22 and 40°C produced the longest T,, for all segments, except oesophagus and crop at 22°C. In relative humidity experiments, the longest TSo were obtained at 90% of r.h. The influence of temperature on the transit ratio (TR) at the considered time intervals, and expressed for each digestive segment is presented in Fig. 4.
0.5 h
of of
The segments 2 and 4 had high and sustained transits during all the experimental time, independently of the thermal conditions. On the other hand, during the first 2 hr, the temperatures of 22 and 40’ C presented the minimum TR, except for segment I at 22°C. Four hours after the marker administration, all the thermal conditions produced high transits in all digestive segments, with amounts near saturation. Finally, the effects of relative humidity on the different digestive segments, considered at the studied time intervals, are shown in Fig. 5. Similarly in the temperature experiments, seg-
.. . . .. .
:
_I?
5 6
..
1-
1 h
..
B
2h
4h
I
r
i
.. .
. . .. . . ..
Fig. 4. The effect of temperature on the transit ratio (TR) _t SEM of the different chick digestive segments, obtained at 0.5, 1, 2 and 4 hr. GI segments are represented by means of the same symbols of Fig. 1. (*P < 0.05; **p < 0.01).
Temperature
and relative
humidity
485
effect on chick GI motility
25%
0.5
h
1 h
.. .. .. .
4h
Fig. 5. The effect of relative humidity on the transit ratio (TR) k SEM of the different chick digestive segments, obtained at 0.5, 1, 2 and 4 hr. GI segments are represented by means of the same symbols of Fig. 1. (*P < 0.05; **P < 0.01).
ments 2 and 4 had high and sustained TR during all the experimental times, independently of the r.h. conditions. During the first 2 hr, 25, 50, and 75% of r.h. produced no differences between their TR, except those found in segment 1 at 75% of r.h., and segment 3 at 50% of r.h., which were slightly higher than in the other studied r.h. conditions. On the other hand, the highest r.h. (90%) produced the lowest rate of transit. DISCUSSION
Efects
of temperafure
The high motor activity found at 22°C in the upper segments could be imputed to a high activation of alimentary behaviour, produced by cold as a thermogenie mechanism (Kendeigh, 1969). Probably, the conscious perception of cold, through somatic nerves, incremented the deglution reflexes. On the other side, the lower segments, autonomically regulated, were depressed at 22”C, which could be a result of increased catecholamines secretion, produced by cold stress (Furness and Burnstock, 1975). These results seem to be contradictory with those found in dogs (Carlson, 1916; Sleeth and Van Liere, 1937) where low temperatures increased the gastric transit and emptying. However, considering also the high sensitivity of young chickens to low temperature (Randall, 1943; Barrott and Pringle, 1947, 1949, 1950, 1951; Moreng and Shaffner, 1951; Huston, 1965), it can be concluded that the temperature of 22 C is low enough to interfere with the homeostatic mechanisms, which should increase the motor activity as found in dogs. In any case, the discrepancy is
partial, because the oesophagus and crop responded to cold as it was expected. In addition, a decrease in GI motility was found at 40°C. A concordance with previous results also has been found at 34”C, which could be considered as an optimal temperature for the &day-old chickens. only
EfSects of‘ relatiae humidity
It is difficult to understand the obtained results, considering the absolute lack of previous work in this field, which would serve as a departure point. According to this, the only justifiable assumption on the relative humidity effects is to consider this environmental parameter as another component of the chicken’s thermal comfort. This has been assumed in man in domestic heating and conditioning (Ellis, 1953; Bedford, 1964). Under these circumstances, the r.h. experiments could be considered as an extension of the temperature ones. In this way, the temperature of 34,‘C only could be considered as optimal for the oesophagus and crop if a relative humidity of 75% is granted, whereas that for segment 3 (muscular stomach), is conditioned for 50% of r.h. In the same way, the low motility found at 90% of r.h. agrees with the assumption of a moderate heat stress, according to the results of Carlson (1916) and Sleeth and Van Liere (1937), which found depressed motility when increased temperature.
Acknou~ledgemenrs-The
authors are grateful to Antoni Rigo and Martin Felani (PIEMA, S.A.) for supplying the Arbor Acres broilers. This work has been par!ially presented at XX Conqeso National de la S.E.C.F. (Murcia, 1984).
JOSEPA. TUR an d RUBEN V. RIAL
486 REFERENCES
Bard P. A. (1928) A diencephalic mechanism for the expression of rage with special reference to the sympathetic nervous system. Am. J. Phvsiol. 84, 490-515. Barrott H. G. and Pringle E. M. (1947) Effect of environment on growth and feed and water consumption of chickens. I. The effect of temperature of environment during the first nine days after hatch. J. Nutr. 34, 53358. Barrott H. G. and Pringle E. M. (1949) Effect of environment on growth and feed and water consumption of chickens. II. The effect of temperature and humidity of environment during the first eighteen days after hatch. J. Nutr. 37, 153-161. Barrott H. G. and Pringle E. M. (1950) Effect of environment on growth and feed and water consumption of chickens. III. The effect of temperature of environment during the period from I8 to 32 days of age. J. Nutr. 41, 25-30. Barrott H. G. and Pringle E. M. (1951) Effect of environment on growth and feed and water consumption of chickens. J. Nutr. 45, 2655274. Bedford T. (1964) Basic Principles qf Veniilalion and Heuting. 2nd edn. H. K. Lewis, London. Blickenstaff D. D. and Grossman M. I. (1950) Quantitative study of reduction of gastric acid secretion associated with-pyrexia. Am. J. Piysiol. 160, 567-571. Carlson A. J. (1916) The Control of Hunger in Health and Disease, p. il9, University of Chicago Press, Chicago, Illinois. Dobson C., Charles D. R.. Emmans G. C. and Rhys I. W. (1970) Poultry Housing and Encironmenl, p. 106, Ministry of Agriculture, Fisheries and Food Bulletin 56. 6th edn HMSO. London. Ellis F. P. (1953) Hunterian lecture. Ann. R. Coil. Surg. 13, 369-39 I. Furness J. B. and Burnstock G. (1975) Role of circulating catecholamines in the gastrointestinal tract. Handbook qf
Physiology. Endocrinology, Sect. 7, Vol. VI (Edited by Blaschko H., Sayers G. and Smith A. D.), pp. 515-536. Am. Physiol. Sot., Washington, D.C. Gotialons E., Rial R. and Tur J. A. (1982) Phenol red as indicator of the digestive tract motility in chickens. Poulr. Sci., 61, 581-583. Goiialons E.. Rial R. and Tur J. A. (1983) Estudio de la motilidad gastrointestinal de1 polio mediante rojo fenol. Rec. Esp. Fisiol. 39, 13-18. Huston T. M. (1965) The influence of different environmental temperature on immature fowl. Poulr. Sci. 44, 1032-1036. Kendeigh S. C. (1969) Energy responses of birds to their thermal environment. Wilson Bull. 81, 441-449. Meyer J. and Carlson A. J. (1917) Hunger and appetite in fever. Am. J. Physiol. 44, 222-233. Moreng R. E. and Shaffner C. S. (1951) Lethal internal temperatures for the chicken, from fertile egg to mature fowl. Poulr. Sci. 30, 255-261. Randall W. C. (1943) Factors influencing the temperature regulation of birds. Am. J. Physiol. 139, 5663. Reynell P. C. and Spray G. H. (1956) The simultaneous measurement of absorption and transit in the gastrointestinal tract of the rat. J. Physiol., Lond. 211, 341-358. Sleeth C. K. and Van Liere E. J. (1937) The effect of environmental temperature on the emptying time of the stomach. Am. J. Phvsiol.. 118, 272-275. Tur J. A., Rial R., Mestre J. M. and Pomar A. M. (1982) lJC-PEG-4000 coma indicador de la motilidad gastrointestinal. Resimenes de1 XIX Congreso de la S.E.C.F. (Mdkuga). Comm. no. 144. Wallgren H. (1954) Energy metabolism of two species of the genus Ember& as correlated with distribution and migration. Acra 2001. Fennica 84, l-1 10. Whittow G. C. (1968) Regulation de la temperatura organica. In Fisiologiu Aoiar (Edited by Sturkie P. D.), pp. 158-178. Acribia. Zaragoza.
(
Printed m Great Biitain
THE
EFFECT
OF TEMPERATURE
HUMIDITY
JOSEP of Animal
RELATIVE
ON THE GASTROINTESTINAL
MOTILITY Department
AND
0300-9629185 $3.00 + 0.00 1985 Pergamon Press Ltd
OF YOUNG A.
Physiology,
TUR
and RUBEN
BROILERS V.
RIAL
Faculty of Sciences, University Balearic Islands, Spain (Rewired
of Ciutat
de Mallorca.
22 June 1984)
Abstract-l. The effects of exposing &day-old broilers to different temperatures (22, 34. 4O’C) and relative humidities (25. 50. 75. 90”/:) on the GI motility has been measured by means of ‘YJ-polyethylene glycol-4000. 2. Chick digestive tract motility was unfavorably influenced by the lowest studied temperature (22”C), being increased at the oesophagus-crop, and being reduced at the remaining digestive tract. This effect was imputed to cold stress. 3. The highest studied temperature (4o’C) reduced the chick GI motility, along the whole digestive tract. 4. From all the studied temperatures, 34-C could be considered the optimum for the digestive motility in chickens. 5. The relative humidity (r.h.) could be considered as a factor of chick thermal comfort, after its observed effects on the GI motility. 6. The r.h. effect, measured at fixed temperature (34’C), resulted in maximal motility for oesophaguscrop at 75”, of r.h., whereas for muscular stomach this maximum was achieved at 50”; of r.h. 7. The highest r.h. (901/J produced the lowest values of chick GI motility.
INTRODUCTION
On the other hand, maximum growth of chicks and optimal efficiency of food utilization were obtained (Barrott and Pringle, 1947, 1949, 1950, 1951) when temperature was kept at 34°C at the start, and then decreasing uniformly at the rate of O.S”C/day, until 19°C for the 32 day-old chickens. Concerning the relative humidity, it has known a limitant effect on the heat loss mechanisms, sweating or panting. Consequently, in high hot-humid environments only behavioral thermoregulation is possible. However, a lower metabolism was found in Emberiza hortuluna (Wallgren, 1954) when these birds were placed in high relative humidity environment. These results were not confirmed in hens (Whittow, 1968). In this context, the aim of this paper is to study the effect of temperature and relative humidity (r.h.) on the gastrointestinal (GI) motility, in early stages of the chick life.
The digestive tract plays a fundamental role concerning the adjustment of the organism to a variety of environmental conditions. According to temperature, this function is specially important in homeotherms. However, the effects produced by thermal changes on the gastrointestinal function have been scarcely studied. In dogs, the influences of environmental temperature on gastric emptying has been found (Carlson, 1916; Sleeth and Van Liere, 1937). Generally speaking, low temperatures increased, and high temperatures slowed tone and motility in the starved stomach. On the other hand, a reduction in gastric motility and secretion was found in relation to fever (Meyer and Carlson, 1917; Bard, 1928; Blickenstaff and Grossman, 1950). In addition, a well established correlation is known between food intake and temperature (Whittow. 1968), decreasing the first and increasing the latter. These relations between thermal environment and nutritive function are particularly interesting in young animals, where the digestive tract has to assume its full activity with an abrupt onset, while the full homeothermic capacity is not attained until weeks after hatching. A high sensitivity to environmental temperature was found in baby chicks (Randall, 1943; Moreng and Shaffner, 1951), and later, when young chicks were maintained at 2435°C and the feed at an environmental temperature of 8°C (Huston, 1965), the animals would not leave the hover long enough to eat and drink sufficiently. This proved that temperature was more important to them than eating.
MATERIALS
AND METHODS
Broilers of both sexes. Arbor Acres strain (hybrid of 3 Cornish x 0 White Rock), 81.3 to 83.1 g, and 8 days old were used. From hatching they were maintained under controlled conditions of temperature, relative humidity, and photoperiod (12/12 hr dark-light schedule), in a climatic chamber Heraeus Viitsch VTPH 5/1000, and receiving water and food (standard commercial diet) ad libifum. Temperature
and r&tire
humidi!,
To study the motor function in the digestive tract as to be influenced by temperature and relative humidity, seven groups of 40 animals were studied under the environmental characteristics showed in Table 1. 481
482
JOSEP A. TUR and RUBEN V. RIAL procedure to study the etTect of temperature and relative humidity on the chick GI tract motility
Table I. Experimental
Experiment
Effect
Relative
Temperature
Humidity
22oc
75%
34°C
75%
40°C
75%
of
Temperature
Effect
34oc
25%
34oc
50%
of
Relative 34oc
75%
34°C
90%
Humidity
The experimental temperatures of 22 and 4O’C were chosen to be slightly under the lethal limits, and the third so as to be very close to the optimal temperature (Randall, 1943; Barrott & Pringle, 1947, 1949, 1950, 1951; Moreng and Shaffner, 1951). For the relative humidity experiments, a 75% of r.h. was considered as the optimum. according to Dobson et al. (1970). Measure
qf the gastrointestinal
motility
To study the effects of different temperatures and relative humidities on the GI motility, the movement of a nonabsorbable indicator, ‘+‘C-polyethylene glycol-4000 (‘4C-PEG-4000). along Ihe chick digestive tract (Tur et al., 1982) was studied. This isotope (specific activity = 21.7 mCi/g, Radiochemical Centre, Amersham, Great Britain) was mixed with polyethylene glycol-4000 (Sigma Chemical Co., St Louis, MO, USA) and dissolved in phosphate buffer (PO,H,Naj PO,HNa,. pH 7.26) at a concentration of 0.77mg/ml, resulting in a final activity of 0.08 pCi/ml. The radioactive solution was mixed additionally with 2% of methylcellulose, which provided a controlled viscosity of 0.458 cN s. mm>. For each temperature or relative humidity experiment 40 animals were used, divided into four subgroups of 10 animals according to the time of their sacrifice. Each animal received, through oral cannula, 1 ml of the mentioned radioactive solution. After 0.5, 1, 2 and 4 hr the animals were killed by chloroform inhalation. The digestive tract was then dissected, and eight sections were made according to the procedure described by Goiialons et al. (1982, 1983). The contents of each segment were extracted by maceration in IOml of distilled water. After maceration, the extract was centrifuged at 3500 rpm 20 min (1200g approx.) and I ml of the supernatant was submitted to 80°C for dryness into a scintillation vial. This dry extract was diluted in 15 ml of liquid scintillation cocktail, and its activity was measured by liquid scintillation spectrometry (Intertechnique Liquid Scintillation Spectrometer, Model SL 30). A counting time of 1 min was used for each vial, and quenching corrections were made by means of the channel ratio method. Analysis
of the results
The radioactivity present in each digestive segment was expressed as a percentage of total radioactivity recovered from the entire GI tract. Emptying Percentage (EP) and Transit Ratio (TR) were determined for each segment, according to Reynell and Spray (1956) definition, and Emptying half time (T,,), which
was calculated by interpolation after plotting the averaged values of EP against time, and drawing the regression line. Statistics Parametric statistics (analysis of variance) were used for signification of results in the studies of ‘%Y-PEG-4000 recovery, EP, and TR. In addition. SEM was used in the graphic expression of the results. RESULTS
The percentages of recovered “C-PEG-4000 as influenced by temperature at 0.5. I, 2 and 4 hr after marker administration, and expressed for each of the eight considered segments are presented in Fig. 1. The statistical differences between the different temperatures show that this environmental parameter modified the percentages recuperated from the eight gastrointestinal segments, in a variable form. The lowest progression rate of intraluminal contents was found at environmental temperature of 40°C. At 22”C, the results are similar except in the first segment (oesophagus and crop), which has the lowest recuperation. Besides these results, the segments 2 (proventriculus) and 4 (duodenal loop) showed always and for every experimental temperature, very low recuperation indexes. The percentages of recovered ‘%PEG-4000 as influenced by relative humidity (r.h.), at 0.5, 1, 2 and 4 hr after marker administration, and expresed for each of the eight considered digestive segments are presented in Fig. 2. These results show that the r.h. partially modified the recuperated radioactivity percentages. In fact, 90% of r.h. produced the highest recuperation, whereas at 75”/, of r.h. segment 1 (oesophaguscrop) produced constantly the lowest recuperation. In the same way, for segment 3 (muscular stomach) the lowest recuperation was obtained at 50% of r.h. Similarly to the temperature experiments, segments 2 and 4 produced very low recuperations at every r.h. value. The effects of temperature and relative humidity on the Emptying half time (T,,,) are presented in Fig. 3. T,, has been calculated for all digestive segments, except for those in which their T,, was shorter than the minimum measured time (0.5 hr), being also the
Temperature
: 3
2h: 6 7 8
and relative
humidity
L h
483
effect on chick GI motility
. . .. ..
Fig. 1. The effect of temperature on the recovered radioactivity (%) f SEM, at 0.5, 1, 2 and 4 hr, along the chick GI tract: (1) Oesophaguwxop; (2) prorwntriculus; (3) muscular stomach; (4) duodenal loop; (5) small intestine part I Cjejunum); (6) small intestine part II (ileum); (7) terminal ileum-caeca-rectum; (8) cloaca and feces. (*P < 0.05; **P < 0.01).
Zh
Fig. 2. The effect of relative humidity on the recovered radioactivity (7;) f SEM, at 0.5, I, 2 and 4 hr, along the chick GI tract. Digestive segments are represented by means of the same symbols of Fig. 1. (*P < 0.05: **p < 0.01).
484
JOSEP A. TUR and
T,,
(h)
RUBEN V. RIAL
Tso (h)
9
L
22'C
0
34'C
n
4O'C
a
9
h 5
aAll 12
3
4
5
6
7
digestive
tract
segment!
Fig. 3. The effect of temperature and relative humidity on the Emptying half time (T,,) + SEM the different chick GI segments. Digestive segments are represented by means of the same symbols Fig. 1. (*P < 0.05; **P < 0.01).
EP obtained at these short times clearly non linear, which would produce nonsignificant results when interpolations would be attempted. These results are a confirmation of those presented in Figs 1 and 2. So, in temperature experiments, both 22 and 40°C produced the longest T,, for all segments, except oesophagus and crop at 22°C. In relative humidity experiments, the longest TSo were obtained at 90% of r.h. The influence of temperature on the transit ratio (TR) at the considered time intervals, and expressed for each digestive segment is presented in Fig. 4.
0.5 h
of of
The segments 2 and 4 had high and sustained transits during all the experimental time, independently of the thermal conditions. On the other hand, during the first 2 hr, the temperatures of 22 and 40’ C presented the minimum TR, except for segment I at 22°C. Four hours after the marker administration, all the thermal conditions produced high transits in all digestive segments, with amounts near saturation. Finally, the effects of relative humidity on the different digestive segments, considered at the studied time intervals, are shown in Fig. 5. Similarly in the temperature experiments, seg-
.. . . .. .
:
_I?
5 6
..
1-
1 h
..
B
2h
4h
I
r
i
.. .
. . .. . . ..
Fig. 4. The effect of temperature on the transit ratio (TR) _t SEM of the different chick digestive segments, obtained at 0.5, 1, 2 and 4 hr. GI segments are represented by means of the same symbols of Fig. 1. (*P < 0.05; **p < 0.01).
Temperature
and relative
humidity
485
effect on chick GI motility
25%
0.5
h
1 h
.. .. .. .
4h
Fig. 5. The effect of relative humidity on the transit ratio (TR) k SEM of the different chick digestive segments, obtained at 0.5, 1, 2 and 4 hr. GI segments are represented by means of the same symbols of Fig. 1. (*P < 0.05; **P < 0.01).
ments 2 and 4 had high and sustained TR during all the experimental times, independently of the r.h. conditions. During the first 2 hr, 25, 50, and 75% of r.h. produced no differences between their TR, except those found in segment 1 at 75% of r.h., and segment 3 at 50% of r.h., which were slightly higher than in the other studied r.h. conditions. On the other hand, the highest r.h. (90%) produced the lowest rate of transit. DISCUSSION
Efects
of temperafure
The high motor activity found at 22°C in the upper segments could be imputed to a high activation of alimentary behaviour, produced by cold as a thermogenie mechanism (Kendeigh, 1969). Probably, the conscious perception of cold, through somatic nerves, incremented the deglution reflexes. On the other side, the lower segments, autonomically regulated, were depressed at 22”C, which could be a result of increased catecholamines secretion, produced by cold stress (Furness and Burnstock, 1975). These results seem to be contradictory with those found in dogs (Carlson, 1916; Sleeth and Van Liere, 1937) where low temperatures increased the gastric transit and emptying. However, considering also the high sensitivity of young chickens to low temperature (Randall, 1943; Barrott and Pringle, 1947, 1949, 1950, 1951; Moreng and Shaffner, 1951; Huston, 1965), it can be concluded that the temperature of 22 C is low enough to interfere with the homeostatic mechanisms, which should increase the motor activity as found in dogs. In any case, the discrepancy is
partial, because the oesophagus and crop responded to cold as it was expected. In addition, a decrease in GI motility was found at 40°C. A concordance with previous results also has been found at 34”C, which could be considered as an optimal temperature for the &day-old chickens. only
EfSects of‘ relatiae humidity
It is difficult to understand the obtained results, considering the absolute lack of previous work in this field, which would serve as a departure point. According to this, the only justifiable assumption on the relative humidity effects is to consider this environmental parameter as another component of the chicken’s thermal comfort. This has been assumed in man in domestic heating and conditioning (Ellis, 1953; Bedford, 1964). Under these circumstances, the r.h. experiments could be considered as an extension of the temperature ones. In this way, the temperature of 34,‘C only could be considered as optimal for the oesophagus and crop if a relative humidity of 75% is granted, whereas that for segment 3 (muscular stomach), is conditioned for 50% of r.h. In the same way, the low motility found at 90% of r.h. agrees with the assumption of a moderate heat stress, according to the results of Carlson (1916) and Sleeth and Van Liere (1937), which found depressed motility when increased temperature.
Acknou~ledgemenrs-The
authors are grateful to Antoni Rigo and Martin Felani (PIEMA, S.A.) for supplying the Arbor Acres broilers. This work has been par!ially presented at XX Conqeso National de la S.E.C.F. (Murcia, 1984).
JOSEPA. TUR an d RUBEN V. RIAL
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