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Body Surface Evaporation Rates at Low and High Temperatures in Murrah Buffalo1
BodySurface Evaporation Ratesat Low and High Temperatures in Murrah Buffalo B. C. JOSHI, R. E. McDOWELL, and D. P. SADHU ~
Indian Veterinary Research Institute, Izatnagar, U.P., India and Cornell University, Ithaca, New York Abstract
Evaporation rates of water from the skin surfaces were measured by capsule technique on three body locations of five Murrah buffalo heifers. A f t e r being accustomed to hot, dry (summer), hot, humid (monsoon) and cool (winter) ambient conditions, the heifers were moved to a psyehrometrie control room maintained at either 18.5 C dry bulb temperature, 13.0 C wet bulb temperature or 40.5 C dry bulb temperature, 35.0 C wet bulb temperature. E v a p oration rates and skin and rectal temperatures were recorded between the fourth and sixth hour of exposure in the control room. The conditions of exposure prior to the tests had a significant (P ~ .01) influence on evaporation rates under both test regimes. A t 185 C, the rates were about the same as for Gir and t I a r i a n a cattle (4.6 rag/10 cm2/5 rain). Under the hot, humid tests (40.5 C) the evaporation rates were 50.8, 26.2 and 24.1 mg for the summer, monsoon and winter seasons, respectively. This was 26% less than for Gir and H a r i a n a cattle in summer and about 50% less in the other two seasons. The marked increase in evaporation rates under the high test conditions indicates contributions by sweat glands. Rates were not significantly correlated with either skin or rectal temperature at 18.5 C, but at 40.5 C both temperatures were negatively correlated ( P < .01) with evaporation rates ( a v g - - . 6 0 ) . The generally prevailing concept is that buffaloes belong to the category of animals with a poor capability for sweating. But in this species an awareness of the importance of evaporative cooling in body heat regulation Received for publication May 6, 1968.
is well known because of its instinctive behavioral preference for wallowing during hot weather (5, 8). Hafez et al. (1) reported E g y p t i a n buffaloes had sweat glands with a glandular surface per single sweat gland of 0.247 cm2 which was about twice the size found for a group of contemporary cattle (0.124 cm~). These authors showed a high correlation between sweat glands and the number of hair follicles in each species; therefore, glandular surface of sweat gland per em~ of skin surface was 1.07 in buffaloes and 3.08 in cattle. Hafez et al. (1) reported the skin thickness of buffaloes to be about twice that of the cattle they sampled and there were also significant differences between the two species in the distribution of blood vessels in the skin. I n buffaloes, the arteries branched more frequently giving rise to many arterioles and capillaries. I n addition, lymphatics were more frequent in buffalo than in the skin of the cattle. There is no evidence avaiIable on method of control of the sweat glands in buffaloes. Assuming the avenues of control are similar to those for cattle, skin characteristics and density of glands indicates the efficiency of sweating in buffaloes is less than for cattle. Nevertheless, Mulliek (5) reported insensible perspiration in buffaloes maintained a significant positive relationship with increases in air temperature. The current studies deal with the rate of surface evaporation in buffalo heifers under cool and hot, humid conditions. Experimental
Procedures
Five open Murrah heifers ranging in age from 12-24 months were periodically placed in a psychrometric control room at 18.5 C dry bulb temperature (DBT) and 13.0 C wet bulb temperature ( W B T ) or 40.5 C DBT and 35.0 C WBT. Except for these periods, the heifers were k e p t stanchioned in an open shed. They were fed at a rate slightly above maintenance levels, but feed and water were withdrawn during the test periods. Evaporation rates were measured by the capsule technique described by McDowell et al. (4). Collections were recorded as rag/10 cm2 for two 5-minute periods from areas on the
1 These investigations were financed in part by a grant made by the United States Department of Agriculture, A.R.S., under Public Law 480. 2 Present address: Department of Animal Physiology, Bengal Veterinary College, Calcutta, India. 1689
1690
JOSHI, McDOWELL, AND SADHU
TABLE 1. Seasonal temperatures and vapor pressure at Izatnagar, India, during experimental periods. Temperature Average
Vapor
Period
Season
Daily
Maximum
Minimum
3/15-6/14
Summer (hot, dry) Monsoon (hot, wet) Winter (cool)
31.9 30.3 16.7
(C) 39.9 35.3 26.3
24.5 25.9 7.6
6/15-9/14 11/15-2/14
pressure (ram I t g ) 11.6 24.9 10.6
The surface e v a p o r a t i o n r a t e s in the cool test conditions differed significantly ( P < .05) a m o n g the three seasons with t h e lowest r a t e s i n winter. The m o i s t u r e collected a t 18.5 C was m a i n l y t h r o u g h the passive p h e n o m e n a of diff u s i o n a n d its r a t e would likely change w i t h modifications in skin characteristics. I n the winter, the t e m p e r a t u r e s were low enough ( T a b l e 1) to b r i n g a b o u t some increase in skin thickness (1) which would create to some e x t e n t a b a r r i e r f o r the free p a s s a g e of moisture to the surface. There would also be some constriction in the superficial blood vessels t h a t would limit the a v a i l a b i l i t y of water. The p r e vailing a m b i e n t t e m p e r a t u r e s d u r i n g the summ e r a n d m o n s o o n seasons f a v o r e d decreased skin thickness a n d v a s o d i l a t i o n of t h e cutaneous blood vessels. A c c o r d i n g to the findings of t t a y m a n a n d N a y (2) w i t h cattle, the volume of the sweat g l a n d s was 6 0 % less in w i n t e r t h a n summer. Therefore, the v a r i a t i o n in responses a m o n g seasons was likely a reflection of the skin s u r f a c e a n d superficial tissue condition b r o u g h t a b o u t b y the e n v i r o n m e n t s which the s h o r t exposure of 6 h o u r s was n o t sufficient to reverse. S i m i l a r p a t t e r n s of r e s p o n s e were observed i n G i r cattle (3).
shoulder, flank a n d r u m p of each a n i m a l between the f o u r t h a n d sixth h o u r of e x p o s u r e to the controlled t e m p e r a t u r e conditions. The s h o u l d e r a r e a was on the u p p e r p a r t of the s c a p u l a ; the flank was over the 11-12tb rib 40-50 cm f r o m the b a c k ; a n d the r u m p location was h a l f - w a y f r o m the h i p s to pins, a b o u t 15 cm f r o m the dorsal line. The same locations were used f o r all the tests. Two a n i m a l s were tested p e r d a y w i t h the e n t r y to the test conditions s t a g g e r e d to equalize e x p o s u r e time. The test periods were in mid-summer, -monsoon a n d -winter. The p r e v a i l i n g a m b i e n t conditions f o r these periods are in Table 1. I n the statistical analysis, the a v e r a g e s o f the duplicate observations p e r b o d y a r e a were used. S i m u l t a n e o u s l y with the m e a s u r e m e n t of e v a p o r a t i o n rates, skin t e m p e r a t u r e s of s i m i l a r locations on the opposite side of the b o d y were recorded b y means of a t h e r m o c o u p l e p r o b e a p p l i e d to the skin. Rectal t e m p e r a t u r e s were t a k e n h a l f - w a y t h r o u g h the collection periods. Results and Discussion
The m e a n s a n d s t a n d a r d e r r o r s f o r e v a p o r a tion r a t e s u n d e r two test conditions b y season a n d body location are in Table 2.
TABLE 2. Evaporation rates from the shoulder, flank and rump areas of Murrah buffaloes in three seasons during exposure to cool and hot, humid test conditions. Summer' S~
Mean 3 SE Avg by seasons Mean SE Avg by seasons
F
Monsoon R
S
F
Winter R
(mg/10 cm2/5 rain) Cool (18.5 C DBT, 13.0 C W B T ) 7.28 8.76 7.34 2.88 4.12 4.42 1.22 1.38 1.65 0.42 0.64 0.77 7.79 ~ ± 0.794 3.82 b -+- 0.38 45.18 3.02
S
2.00 0.35
Hot, humid (40.5 C DBT, 35.0 C W B T ) 57.16 50.16 24.20 24.25 27.44 24.18 5.70 2.62 5.49 1.54 3.98 1.52 50.83 ~ ± 2.52 26.29 b ± 2.17
F
R
1.92 2.28 0.38 0.25 2.07 ¢ ± 0.18 24.70 23.32 2.82 2.06 24.07 b ± 1.19
z Designations of average environmental conditions the animals were exposed to prior to testing. ~Areas of the body; S, shoulder, F, flank; R, rump. Each value represents an average of duplicate observations on 5 animals. Standard error. a, b, c values in the same row with a common superscript are not significantly different ( P ~ .05), but do differ from those not having the same superscript. J. D ~ R Y SCIENCE ~OL. 51, NO. 10
CATTLE E V A P O R A T I O N R A T E S
The markedly higher evaporation rates under the hot, humid tests (avg 33.73 rag) suggest contributions by the sweat glands. I t is also evident that the environmental conditions prior to the tests (season) had a marked influence on the amount of water vapor collected from the surfaces (Table 2). The average rates of the buffaloes during the summer tests were about 74% of those for Hariana and Gir cattle (3) subjected to similar conditions. The species variation in rates for this season was probably due to differences in the number of sweat glands per unit of surface area, 135 to 394/cm2 in buffaloes (1, 6, 9) versus 1,509 to 2,633/cm2 for cattle (1, 7). I n the monsoon season, the average for the buffaloes (Table 2) was little more than half that for Gir cattle (47.38 rag) but o n l y about one-third the average for Harianas (75.23 mg). When shifted from the winter environment to the 40.5 temperature the average evaporation rate for the buffaloes was 58% less than for the two cattle breeds. The species differences in winter were no doubt partially influenced by the skin characteristics and sweat gland density. The reason for the greater variation between buffaloes and the two breeds of cattle in the monsoon season than in the summer is more difficult to understand. Some reports claim that the Murrah buffalo is instinctively semi-aquatic (5, 8). This could mean that when the buffaloes were accustomed to warm humid weather they were less stimulated by the hot, humid test conditions than by the change in enviromnents during the dry heat of summer. Assuming the sweat gland surface per unit of skin area in cattle is at least three times that of buffaloes (1), it seems that under thermal stress conditions the sweat glands of buffaloes are nearly as functional as those of cattle after being exposed to hot, dry conditions such as occur at Izatnagar in the summer. These results also suggest that buffaloes have about the same threshold level for stimulus by thermal stress as Indian cattle. The site of collection on the body and animal differences were not important in evaporation rates under either of the test atmospheres. The mean skin temperatures for body locations opposite the collection sites and rectal temperatures are in Table 3. For the cool tests, across all seasons, the correlations between evaporation rates and skin and rectal temperature were near zero (--.04), but for the hot, humid tests the correlations were significant (P < .01). The correlation between rate and skin temperature was --0.67 and that for rate and rectal
1691
TABLE 3. Mean skin and rectal temperatures of buffalo heifers during test room conditions of cool or hot, humid in various seasons. Temperature
Seasons Summer
Monsoon
Winter
Skins Rectal
(C) Cool (18.5 C DBT, 13.0 C WBT) 27.56 ± .27b 28.17 ___.21 28.71 ~ .34 38.31 ± .08 38.29± .04 38.38 ± .07
Skin Rectal
Hot, humid (40.5 C DBT, 35.0 C WBT) 37.53 ± .19 39.24± .17 39.61 ± .22 40.10 ± .11 40.55± .13 40.73 + .17
a Each value represents an average of three ]ocations on each of 5 animals. b Standard error. temperature, --0.52. Similar significant negative relationships were observed in Gir cattle (3). The high negative correlation of skin temperature and evaporation rate further suggests the involvement of an active process in moisture availability. Had the process been entirely passive, i.e., as an outcome of the gradient developing between the unaltered vapor pressure of the environment adjacent to the animal's body and the saturation vapor pressure of the circulating blood, a positive correlation should have resulted, since the latter is largely under the influence of skin temperature. The negative rectal temperature-evaporation rate correlation resulted from the higher rectal temperatures in relation to rate in the monsoon and winter season. This gives further indications that the skin of the buffalo must be adequately pre-eonditioned by the previous environment for the sweat glands to respond to stimulation in the matter of a few hours. Therefore, the presence of a more efficient mechanism for functioning of the sweat glands with increases in rectal temperature, within certain limits, may be the reason for the positive rectal temperature-evaporation rate in cattle. References
(1) Hafez, E. S. E., A. L. Baderldin, and 1~. M. Shafel. 1955. Skin structure of Egyptian buffaloes and cattle with particular reference to sweat glands. J. Agr. Sci., 46: 19. (2) Hayman, R. H., and T. Nay. 1958. Sweat glands in Zebu (Bes Indicus L.) and European (B. Taurus L.) cattle. II. Effects of season and exercise on sweat gland volume. Australian J. Agr. Res., 9: 385. (3) Joshi, B. C., R. E. McDowell, and D. P. Sadhu. 1968. Body surface evaporation rates at low and high temperatures for J, DAII~Y SCIENCE VOL. 51, NO. 10
1692
JOSHI, McDOWELL, AND SADHU
Gir and t t a r i a n a cattle. J. Dairy Sci., 51: 1693. (4) McDowell, R. E., D. H. K. Lee, and M. H. F o h r m a n . 1954. The measurement of water evaporation from limited areas of a normal body surface. J. Anim. Sei., 13:405. (5) Mulliek, D. lq. 1964. Review of the investigations on t h e physiology of I n d i a n Buffaloes. Indian J. Dairy Sci., 1 7 : 4 5 . (6) Nalr, P. G., and B. R. Benjamin. 1963. Studies on sweat glands in the Indian water buffalo. I. Standardization of techniques and preliminary observations. I n d i a n J. Vet. Sci. & Anita. Hush., 33:102.
J. DAIRY SOTENO~ ~'OL. 51, NO. 10
(7) Nay, T., and R. H. Hayman. 1956. Sweat glands in Zebu (Bos Indicus L.) and European (B. Taurus L.) cattle. Australian J. Agr. Res., 7: 482. (8) Rife, D. C. 1959. The W a t e r Buffalo of I n d i a and Pakistan. U.S. Intern. Coop. Admin. Memo, June, 37 pp. (9) Yamane, J., and Y. Ono. 1936. Mere. Fae. Sci. Agr. Taihoku, 8, B 6. (c.f. Nair and Benjamin. 1963. Studies on sweat glands in the Indian water buffalo. I. Standardization of techniques and preliminary observations. I n d i a n J. Vet. Sci. & Anita. Husb., 33: 102.)
Indian Veterinary Research Institute, Izatnagar, U.P., India and Cornell University, Ithaca, New York Abstract
Evaporation rates of water from the skin surfaces were measured by capsule technique on three body locations of five Murrah buffalo heifers. A f t e r being accustomed to hot, dry (summer), hot, humid (monsoon) and cool (winter) ambient conditions, the heifers were moved to a psyehrometrie control room maintained at either 18.5 C dry bulb temperature, 13.0 C wet bulb temperature or 40.5 C dry bulb temperature, 35.0 C wet bulb temperature. E v a p oration rates and skin and rectal temperatures were recorded between the fourth and sixth hour of exposure in the control room. The conditions of exposure prior to the tests had a significant (P ~ .01) influence on evaporation rates under both test regimes. A t 185 C, the rates were about the same as for Gir and t I a r i a n a cattle (4.6 rag/10 cm2/5 rain). Under the hot, humid tests (40.5 C) the evaporation rates were 50.8, 26.2 and 24.1 mg for the summer, monsoon and winter seasons, respectively. This was 26% less than for Gir and H a r i a n a cattle in summer and about 50% less in the other two seasons. The marked increase in evaporation rates under the high test conditions indicates contributions by sweat glands. Rates were not significantly correlated with either skin or rectal temperature at 18.5 C, but at 40.5 C both temperatures were negatively correlated ( P < .01) with evaporation rates ( a v g - - . 6 0 ) . The generally prevailing concept is that buffaloes belong to the category of animals with a poor capability for sweating. But in this species an awareness of the importance of evaporative cooling in body heat regulation Received for publication May 6, 1968.
is well known because of its instinctive behavioral preference for wallowing during hot weather (5, 8). Hafez et al. (1) reported E g y p t i a n buffaloes had sweat glands with a glandular surface per single sweat gland of 0.247 cm2 which was about twice the size found for a group of contemporary cattle (0.124 cm~). These authors showed a high correlation between sweat glands and the number of hair follicles in each species; therefore, glandular surface of sweat gland per em~ of skin surface was 1.07 in buffaloes and 3.08 in cattle. Hafez et al. (1) reported the skin thickness of buffaloes to be about twice that of the cattle they sampled and there were also significant differences between the two species in the distribution of blood vessels in the skin. I n buffaloes, the arteries branched more frequently giving rise to many arterioles and capillaries. I n addition, lymphatics were more frequent in buffalo than in the skin of the cattle. There is no evidence avaiIable on method of control of the sweat glands in buffaloes. Assuming the avenues of control are similar to those for cattle, skin characteristics and density of glands indicates the efficiency of sweating in buffaloes is less than for cattle. Nevertheless, Mulliek (5) reported insensible perspiration in buffaloes maintained a significant positive relationship with increases in air temperature. The current studies deal with the rate of surface evaporation in buffalo heifers under cool and hot, humid conditions. Experimental
Procedures
Five open Murrah heifers ranging in age from 12-24 months were periodically placed in a psychrometric control room at 18.5 C dry bulb temperature (DBT) and 13.0 C wet bulb temperature ( W B T ) or 40.5 C DBT and 35.0 C WBT. Except for these periods, the heifers were k e p t stanchioned in an open shed. They were fed at a rate slightly above maintenance levels, but feed and water were withdrawn during the test periods. Evaporation rates were measured by the capsule technique described by McDowell et al. (4). Collections were recorded as rag/10 cm2 for two 5-minute periods from areas on the
1 These investigations were financed in part by a grant made by the United States Department of Agriculture, A.R.S., under Public Law 480. 2 Present address: Department of Animal Physiology, Bengal Veterinary College, Calcutta, India. 1689
1690
JOSHI, McDOWELL, AND SADHU
TABLE 1. Seasonal temperatures and vapor pressure at Izatnagar, India, during experimental periods. Temperature Average
Vapor
Period
Season
Daily
Maximum
Minimum
3/15-6/14
Summer (hot, dry) Monsoon (hot, wet) Winter (cool)
31.9 30.3 16.7
(C) 39.9 35.3 26.3
24.5 25.9 7.6
6/15-9/14 11/15-2/14
pressure (ram I t g ) 11.6 24.9 10.6
The surface e v a p o r a t i o n r a t e s in the cool test conditions differed significantly ( P < .05) a m o n g the three seasons with t h e lowest r a t e s i n winter. The m o i s t u r e collected a t 18.5 C was m a i n l y t h r o u g h the passive p h e n o m e n a of diff u s i o n a n d its r a t e would likely change w i t h modifications in skin characteristics. I n the winter, the t e m p e r a t u r e s were low enough ( T a b l e 1) to b r i n g a b o u t some increase in skin thickness (1) which would create to some e x t e n t a b a r r i e r f o r the free p a s s a g e of moisture to the surface. There would also be some constriction in the superficial blood vessels t h a t would limit the a v a i l a b i l i t y of water. The p r e vailing a m b i e n t t e m p e r a t u r e s d u r i n g the summ e r a n d m o n s o o n seasons f a v o r e d decreased skin thickness a n d v a s o d i l a t i o n of t h e cutaneous blood vessels. A c c o r d i n g to the findings of t t a y m a n a n d N a y (2) w i t h cattle, the volume of the sweat g l a n d s was 6 0 % less in w i n t e r t h a n summer. Therefore, the v a r i a t i o n in responses a m o n g seasons was likely a reflection of the skin s u r f a c e a n d superficial tissue condition b r o u g h t a b o u t b y the e n v i r o n m e n t s which the s h o r t exposure of 6 h o u r s was n o t sufficient to reverse. S i m i l a r p a t t e r n s of r e s p o n s e were observed i n G i r cattle (3).
shoulder, flank a n d r u m p of each a n i m a l between the f o u r t h a n d sixth h o u r of e x p o s u r e to the controlled t e m p e r a t u r e conditions. The s h o u l d e r a r e a was on the u p p e r p a r t of the s c a p u l a ; the flank was over the 11-12tb rib 40-50 cm f r o m the b a c k ; a n d the r u m p location was h a l f - w a y f r o m the h i p s to pins, a b o u t 15 cm f r o m the dorsal line. The same locations were used f o r all the tests. Two a n i m a l s were tested p e r d a y w i t h the e n t r y to the test conditions s t a g g e r e d to equalize e x p o s u r e time. The test periods were in mid-summer, -monsoon a n d -winter. The p r e v a i l i n g a m b i e n t conditions f o r these periods are in Table 1. I n the statistical analysis, the a v e r a g e s o f the duplicate observations p e r b o d y a r e a were used. S i m u l t a n e o u s l y with the m e a s u r e m e n t of e v a p o r a t i o n rates, skin t e m p e r a t u r e s of s i m i l a r locations on the opposite side of the b o d y were recorded b y means of a t h e r m o c o u p l e p r o b e a p p l i e d to the skin. Rectal t e m p e r a t u r e s were t a k e n h a l f - w a y t h r o u g h the collection periods. Results and Discussion
The m e a n s a n d s t a n d a r d e r r o r s f o r e v a p o r a tion r a t e s u n d e r two test conditions b y season a n d body location are in Table 2.
TABLE 2. Evaporation rates from the shoulder, flank and rump areas of Murrah buffaloes in three seasons during exposure to cool and hot, humid test conditions. Summer' S~
Mean 3 SE Avg by seasons Mean SE Avg by seasons
F
Monsoon R
S
F
Winter R
(mg/10 cm2/5 rain) Cool (18.5 C DBT, 13.0 C W B T ) 7.28 8.76 7.34 2.88 4.12 4.42 1.22 1.38 1.65 0.42 0.64 0.77 7.79 ~ ± 0.794 3.82 b -+- 0.38 45.18 3.02
S
2.00 0.35
Hot, humid (40.5 C DBT, 35.0 C W B T ) 57.16 50.16 24.20 24.25 27.44 24.18 5.70 2.62 5.49 1.54 3.98 1.52 50.83 ~ ± 2.52 26.29 b ± 2.17
F
R
1.92 2.28 0.38 0.25 2.07 ¢ ± 0.18 24.70 23.32 2.82 2.06 24.07 b ± 1.19
z Designations of average environmental conditions the animals were exposed to prior to testing. ~Areas of the body; S, shoulder, F, flank; R, rump. Each value represents an average of duplicate observations on 5 animals. Standard error. a, b, c values in the same row with a common superscript are not significantly different ( P ~ .05), but do differ from those not having the same superscript. J. D ~ R Y SCIENCE ~OL. 51, NO. 10
CATTLE E V A P O R A T I O N R A T E S
The markedly higher evaporation rates under the hot, humid tests (avg 33.73 rag) suggest contributions by the sweat glands. I t is also evident that the environmental conditions prior to the tests (season) had a marked influence on the amount of water vapor collected from the surfaces (Table 2). The average rates of the buffaloes during the summer tests were about 74% of those for Hariana and Gir cattle (3) subjected to similar conditions. The species variation in rates for this season was probably due to differences in the number of sweat glands per unit of surface area, 135 to 394/cm2 in buffaloes (1, 6, 9) versus 1,509 to 2,633/cm2 for cattle (1, 7). I n the monsoon season, the average for the buffaloes (Table 2) was little more than half that for Gir cattle (47.38 rag) but o n l y about one-third the average for Harianas (75.23 mg). When shifted from the winter environment to the 40.5 temperature the average evaporation rate for the buffaloes was 58% less than for the two cattle breeds. The species differences in winter were no doubt partially influenced by the skin characteristics and sweat gland density. The reason for the greater variation between buffaloes and the two breeds of cattle in the monsoon season than in the summer is more difficult to understand. Some reports claim that the Murrah buffalo is instinctively semi-aquatic (5, 8). This could mean that when the buffaloes were accustomed to warm humid weather they were less stimulated by the hot, humid test conditions than by the change in enviromnents during the dry heat of summer. Assuming the sweat gland surface per unit of skin area in cattle is at least three times that of buffaloes (1), it seems that under thermal stress conditions the sweat glands of buffaloes are nearly as functional as those of cattle after being exposed to hot, dry conditions such as occur at Izatnagar in the summer. These results also suggest that buffaloes have about the same threshold level for stimulus by thermal stress as Indian cattle. The site of collection on the body and animal differences were not important in evaporation rates under either of the test atmospheres. The mean skin temperatures for body locations opposite the collection sites and rectal temperatures are in Table 3. For the cool tests, across all seasons, the correlations between evaporation rates and skin and rectal temperature were near zero (--.04), but for the hot, humid tests the correlations were significant (P < .01). The correlation between rate and skin temperature was --0.67 and that for rate and rectal
1691
TABLE 3. Mean skin and rectal temperatures of buffalo heifers during test room conditions of cool or hot, humid in various seasons. Temperature
Seasons Summer
Monsoon
Winter
Skins Rectal
(C) Cool (18.5 C DBT, 13.0 C WBT) 27.56 ± .27b 28.17 ___.21 28.71 ~ .34 38.31 ± .08 38.29± .04 38.38 ± .07
Skin Rectal
Hot, humid (40.5 C DBT, 35.0 C WBT) 37.53 ± .19 39.24± .17 39.61 ± .22 40.10 ± .11 40.55± .13 40.73 + .17
a Each value represents an average of three ]ocations on each of 5 animals. b Standard error. temperature, --0.52. Similar significant negative relationships were observed in Gir cattle (3). The high negative correlation of skin temperature and evaporation rate further suggests the involvement of an active process in moisture availability. Had the process been entirely passive, i.e., as an outcome of the gradient developing between the unaltered vapor pressure of the environment adjacent to the animal's body and the saturation vapor pressure of the circulating blood, a positive correlation should have resulted, since the latter is largely under the influence of skin temperature. The negative rectal temperature-evaporation rate correlation resulted from the higher rectal temperatures in relation to rate in the monsoon and winter season. This gives further indications that the skin of the buffalo must be adequately pre-eonditioned by the previous environment for the sweat glands to respond to stimulation in the matter of a few hours. Therefore, the presence of a more efficient mechanism for functioning of the sweat glands with increases in rectal temperature, within certain limits, may be the reason for the positive rectal temperature-evaporation rate in cattle. References
(1) Hafez, E. S. E., A. L. Baderldin, and 1~. M. Shafel. 1955. Skin structure of Egyptian buffaloes and cattle with particular reference to sweat glands. J. Agr. Sci., 46: 19. (2) Hayman, R. H., and T. Nay. 1958. Sweat glands in Zebu (Bes Indicus L.) and European (B. Taurus L.) cattle. II. Effects of season and exercise on sweat gland volume. Australian J. Agr. Res., 9: 385. (3) Joshi, B. C., R. E. McDowell, and D. P. Sadhu. 1968. Body surface evaporation rates at low and high temperatures for J, DAII~Y SCIENCE VOL. 51, NO. 10
1692
JOSHI, McDOWELL, AND SADHU
Gir and t t a r i a n a cattle. J. Dairy Sci., 51: 1693. (4) McDowell, R. E., D. H. K. Lee, and M. H. F o h r m a n . 1954. The measurement of water evaporation from limited areas of a normal body surface. J. Anim. Sei., 13:405. (5) Mulliek, D. lq. 1964. Review of the investigations on t h e physiology of I n d i a n Buffaloes. Indian J. Dairy Sci., 1 7 : 4 5 . (6) Nalr, P. G., and B. R. Benjamin. 1963. Studies on sweat glands in the Indian water buffalo. I. Standardization of techniques and preliminary observations. I n d i a n J. Vet. Sci. & Anita. Hush., 33:102.
J. DAIRY SOTENO~ ~'OL. 51, NO. 10
(7) Nay, T., and R. H. Hayman. 1956. Sweat glands in Zebu (Bos Indicus L.) and European (B. Taurus L.) cattle. Australian J. Agr. Res., 7: 482. (8) Rife, D. C. 1959. The W a t e r Buffalo of I n d i a and Pakistan. U.S. Intern. Coop. Admin. Memo, June, 37 pp. (9) Yamane, J., and Y. Ono. 1936. Mere. Fae. Sci. Agr. Taihoku, 8, B 6. (c.f. Nair and Benjamin. 1963. Studies on sweat glands in the Indian water buffalo. I. Standardization of techniques and preliminary observations. I n d i a n J. Vet. Sci. & Anita. Husb., 33: 102.)