Directory UMM :Data Elmu:jurnal:S:Small Ruminant Research:Vol39.Issue1.Jan2001:

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A comparison of surface and rectal temperatures between

sheared and non-sheared alpacas (

Lama pacos

)

A.M. Heath

*

, C.B. Navarre, A. Simpkins, R.C. Purohit, D.G. Pugh

Department of Large Animal Surgery and Medicine, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA

Accepted 7 May 2000

Abstract

The objective of this research was to determine if whole-body shearing would effect gross thermoregulation in alpacas. Eight mature, intact male alpacas were randomly assigned to one of two groups and maintained in outdoor pastures with adequate arti®cial shade from June through August (summer climate) in east central Alabama, USA. Group one animals

(N4) were sheared to remove all ®ber to within 2 cm of their skin. Group 2 animals (N4) were left non-sheared. Sheared

alpacas tended to have lower rectal temperatures during high ambient temperatures than did non-sheared alpacas (P0:06).

Thermographic studies of the scrotum revealed cooler surface temperatures in sheared versus non-sheared alpacas (P0:_05).

Temperatures in the right medial thigh of sheared animals were 0.98C cooler than the thigh region of non-sheared animals in

the morning (P<₀:_{03). Right medial thigh temperatures were 1.6}₈_{C cooler in sheared alpacas in the afternoon (P}<₀:_01). Signi®cant positive correlations were found in non-sheared animals between ambient temperature and rectal temperature in

the morning (r0:612,P0:014). In sheared animals during the morning signi®cant positive correlations were established

between the Heat Stress Index (HSI) and the right medial thigh surface temperatures (r0:_648,P0:_{003), the HSI and}

rectal temperature (r0:729,P0:0003), the ambient temperature and right medial thigh surface temperature (r0:485,

P0:_{04), and the ambient temperature and the rectal temperature (r}0:_823,P<₀:_{0001). In the afternoon a signi®cant} positive correlation was found in the sheared alpacas between the HSI and the right medial thigh surface temperature, rectal

temperature and surface scrotal temperature (r0:_538, P0:_02, r0:_543, P0:_{019 and} r0:_522, P0:_045),

respectively. These data indicate that whole-body shearing of alpacas could have a bene®cial effect on thermoregulation when used as a preventative measure against heat stress. Shearing may assist heat dissipation resulting in a cooler surface body temperature and rectal temperature in alpacas when challenged by the heat and humidity experienced in the summer months in

Keywords:Thermography; Scrotal temperature; Heat stress; Heat stress index; Ambient condition

1. Introduction

Although domesticated longer than practically any other animal in the world, South American camelids have remained relatively obscure animals in the

United States until recent years. Progenitors of came-lids are generally assumed to have originated in North America. However, present day camelids have adapted to the Andean Mountain habitat. High tem-perature and high humidity combinations found in the United States, and in particular the southeast, renders heat stress as one of the major causes of illness and death of South American camelids in North America (Johnson, 1993). Estimates of mortality from heat *_{Corresponding author. Tel.:}_{1-334-844-4490;}

fax:1-334-844-6715.

E-mail address: heatham@vetmed.auburn.edu (A.M. Heath).

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stress during the summer of 1995 alone were as high as 1000 animals. This is a major cause, not only of death, but also reduced productivity, infertility in the male, and fetal wastage (Fowler, 1994). The male llama does not have as pendulous a scrotum as most other species and may be more susceptible to the deleterious effects of elevated body temperatures on spermatogenesis than most other animals. Scrotal edema is also a common sequel to heat stress in South American camelids. Hyperthermia is also associated with aber-rations of the central nervous system, the respiratory system, the digestive system, the cardiovascular sys-tem, the hematopoietic syssys-tem, the urinary system and the reproductive system. It has been suggested that shearing will aid in the prevention of heat stress, but no research has been reported demonstrating the effec-tiveness of shearing and to what extent it would act as a preventative measure in decreasing the occurrence of this syndrome (Fowler, 1998). It has also been sug-gested that body ®ber insulates camelids against high temperatures. Therefore, the objective of this clinical trial was to determine if whole-body shearing would effect gross thermoregulation in alpacas.

2. Materials and methods

Eight mature, intact male alpacas were blocked according to weight and coat color. They were then assigned to one of two groups and maintained in outdoor pastures with adequate arti®cial shade from June through September (summer climates) in east central Alabama. Group one animals (N4) were sheared to remove all ®ber to within 2 cm of their skin. Group 2 animals (N4) were left non-sheared. At 14 day intervals for a total period of 90 days, all animals were retrieved from the grazing paddock, moved to an indoor holding facility and allowed to acclimate for 30 min to room temperature (228C) at approximately 8:00 a.m. (CST) and again at approximately 1:00 p.m. (CST). Following acclimation, the animal's rectal temperature was measured using a digital thermo-meter. Subsequently, surface body temperature of the right medial thigh and scrotum was measured using a Thermovision 8701real time imaging system

with AGEMA Infrared Systems computer software. Each thermographic image along with the associated temperature scale was photographed and stored as 20 0

20 0

slides. The highest temperature readings from the thigh and scrotal regions were recorded. Changes in isotherm patterns were visually evaluated. Average ambient temperature, relative humidity and a livestock heat stress index was recorded for each measurement period. These values were collected from data recorded by the Agricultural Weather Information Service, Inc.2The livestock heat stress index is cal-culated from the dry bulb temperature and the relative humidity. All descriptive data was analyzed using the repeated measures analysis of variance (ANOVA). All signi®cant (P<0:05) correlations (Fischer's rto z) were determined by examining a matrix table contain-ing all the recorded variables. Statistical calculations were made using a proprietary software program.3

3. Results

The average values for ambient temperature, heat stress index, and relative humidity are listed in Table 1. Descriptive statistics for the animal temperatures are reported in Table 2. Sheared alpacas tended to have lower core body temperature (39.0₈C versus 39.6₈C) during the warmer afternoon testing periods than did non-sheared alpacas (P0:06). This difference was not apparent during the morning testing periods (P0:74). Thermographic studies of the scrotum revealed a tendency towards cooler surface tempera-tures in sheared versus non-sheared alpacas (P0:05 for the PM test period andP0:06 for the AM test period). Temperatures in the right medial thigh of sheared animals were 18C cooler than non-sheared animals in the morning (P<₀:_{03) and right medial} thigh temperatures were 1.68C cooler in sheared alpa-cas in the afternoon (P<₀:_{01). Clinical heat stress} was not evident in any animals during the study.

Calculated correlations between environmental variables and body temperatures are shown in Table 3. When data was looked at combining both

1_{AGEMA Infrared Systems, Danderyd, Sweden.}

2_{Agricultural Weather Information Service Inc., Auburn} Alaba-ma.

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treatment groups there was a signi®cant correlation between rectal temperatures and medial thigh tem-peratures (P0:05). The calculatedpvalues for the correlations between scrotal temperatures and both rectal and thigh temperatures were all greater that 0.05.

4. Discussion

Thermography utilizes the measurement of infrared radiation to measure surface body temperatures. It can also be used as an indicator of the temperature of tissues deep to the skin as well as actual skin Table 1

Average environmental variable and standard deviations

Temperature8C Heat stress index Relative humidity

Mean SD Mean SD Mean SD

AM 22.50 2.36 71.40 5.03 79.60 10.30

PM 31.50 3.32 76.60 3.80 60.20 8.72

Table 2

Thermographically recorded surface and rectal temperatures and standard deviations in8C

Right medial thigh temp. Scrotal temp. Rectal temp.

Mean SD Mean SD Mean SD

AM (Sheared) 38.10 0.71 34.97 1.13 38.52 0.46

AM (Non-Sheared) 39.06 0.72 36.28 1.13 38.80 0.65

PM (Sheared) 38.02 0.52 35.38 1.10 38.99 0.51

PM (Non-Sheared) 39.64 0.77 37.23 0.99 39.55 0.58

Table 3

Ther-values andp-values for correlations between environmental variables and surface and rectal temperatures

Right medial thigh Scrotum Rectal

In non-sheared alpacas during the morning collection periods

Heat stress index 0.064 (0.824) 0.281 (0.318) 0.447 (0.096)

Relative humidity ÿ0.344 (0.214) 0.484 (0.067) ÿ0.037 (0.897)

Ambient temperature 0.340 (0.220) 0.285 (0.311) 0.612 (0.014)

In sheared alpacas during the morning collection periods

Ambient temperature 0.485 (0.040) 0.311 (0.213) 0.823 (<0.0001)

In non-sheared alpacas during the afternoon collection periods

Heat tress index 0.272 (0.334) 0.522 (0.045) 0.373 (0.174)

Ambient temperature 0.333 (0.231) 0.583 (0.021) 0.434 (0.108)

In sheared llamas during the afternoon collection periods

Relative humidity ÿ0.222 (0.382) ÿ0.024 (0.925) ÿ0.295 (0.239)

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temperature (Coulter et al., 1988). Speci®cally, testi-cular thermography has been used clinically to deter-mine the severity and chronicity of testicular lesions (Purohit and Hudson, 1985). Increased scrotal surface temperature and abnormal scrotal surface temperature patterns had been associated with decreased fertility in bulls (Coulter and Lunstra, 1992). Thermography provides an excellent tool for measuring the skin temperature at different points on the body without altering the temperature in any manner. For this study it provided an ideal temperature-monitoring tool.

Published studies in pregnant sheep suggest that shorn ewes gain weight better and produce heavier litter sizes than non-shorn sheep. The non-shorn sheep were also reported to have an increased respiratory rate and a greater variation in respiratory rates (Hof-man and Riegle, 1977). Rectal temperature, skin temperature, and respiratory rate was shown to increase with increasing wool length in Barki ewes under shaded conditions in Egypt. This same author also suggested that the presence of available shade may also play a role in the animal's ability to thermo-regulate and that in full sunlight, ¯eece may provide insulation from radiant heat (Khalil, 1990). Work by Acharya et al. (1995) showed hair length in goats under full sun conditions in the summer had a pro-tective mechanism against heat stress. Hair color in this report had an interaction with coat length. Clipped Hereford cattle were shown to have a lower core body temperature and lower respiratory rates than non-clipped cattle in a study performed under tropical conditions while forcing the animals to continuously walk. During the hottest part of the day the non-clipped animals were removed from the trial due to clinical signs of heat stress (Yeates, 1977).

Shearing of alpacas under the conditions present in the summer of 1997 in the southeastern United States was shown in this study to lower core body tempera-ture. This difference was found only in the afternoon testing periods corresponding to the hottest part of the day. These temperatures were taken after the alpacas had been in a room temperature environment for approximately 0.5 h. Surface body temperatures mea-sured at the scrotum and at the medial thigh followed a similar pattern. There was consistently a greater dis-crepancy in the surface body temperatures between sheared and non-sheared alpacas during the afternoon hours than during the morning hours. This suggests

that the bene®cial effects of shearing are greater during more extreme temperatures. It was surprising to the authors that no signi®cant correlations were found between the relative humidity and the surface body temperatures. Although the correlations did not prove to be signi®cant, it was interesting to note that the correlations between humidity and animal tem-peratures were for the most part in a negative direc-tion. This may be explained by the methodology of the experiment. The half-hour acclimation period in room temperature may be a confounding factor when explaining surface temperatures relative to humidity. Rectal temperatures tended to follow ambient tem-peratures more consistently in the sheared than in the non-sheared animals in both the morning and the afternoon testing periods. The correlations found between the HSI and ambient temperature compared to the surface temperatures and rectal temperatures indicate that sheared animals respond in a more pre-dictable fashion to changes in the environmental variables studied in this trial. The lack of correlation between scrotal temperatures and environmental vari-ables in the sheared alpacas combined with the sig-ni®cant correlation in the non-sheared alpacas and the decreased scrotal surface temperatures in the sheared alpacas suggest that shearing may have a protective mechanism for scrotal temperature.

Fowler (1998) has described thermoregulation in the llama. The ventral regions of the body, including the inner thigh and the perineal region of the llama are covered by a thinner hair coat than found on the dorsal surfaces of the body. This provides a thermal window for heat dissipation via evaporative cooling through sweating. Shearing of the areas of the llama that have a denser ®ber may allow for better air¯ow in and around this thermal window. Heat dissipation via convection and evaporative cooling mechanisms may also be inhibited in the areas with a denser hair coat if the hair becomes matted, dirty or wet.

5. Conclusions

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investigated in this clinical trial. Repeating a similar study in a more controlled environment, i.e. an envir-onmental chamber, could help to answer some of the mechanistic questions. The data reported in this study did however indicate that whole-body shearing of alpacas could have a bene®cial effect on thermoregu-lation when used as a preventative measure against heat stress. Shearing may assist heat dissipation result-ing in a cooler surface body temperature and rectal temperature in alpacas when challenged by the heat and humidity experienced in the summer months in the Southeastern United States.

References

Acharya, R.M., Gupta, U.D., Sehgal, J.P., Singh, M., 1995. Coat characteristics of goats in relation to heat tolerance in the hot tropics. Small Rumin. Res. 18, 245±248.

Coulter, G.H., Lunstra, D.D., 1992. Infrared thermography of the scrotal surface as a tool for predicting semen quality and fertility in the beef bull, Anim. Sci. 70 (Suppl. 1) 252.

Coulter, G.H., Senger, P.L., Bailey, D.R.C., 1988. Relationship of scrotal surface temperature measured by infrared thermography to subcutaneous and deep testicular temperature in the ram. J. Reprod. Fert. 84, 417±423.

Fowler, M.E., 1994. Hyperthermia in llamas and alpacas, Veterinary clinics of north America. Food Anim. Practice 10, 309±318.

Fowler, M.E., 1998. Medicine and Surgery of South American Camelids. 2nd edition Iowa State University Press, Ames, pp. 235±318.

Hofman, W.F., Riegle, G.D., 1977. Thermorespiratory responses of shorn and unshorn sheep to mild heat stress. Resp. Physiol. 30, 327±338.

Johnson, L.W., 1993. Major llama medical challenges and approaches to their successful treatment. in: Proc. 11th Am. Coll. Vet. Internal Med., pp. 814±816.

Khalil, M.H., 1990. Effects of wool coat length and water deprivation on seasonal changes in some physiologic and hematologic parameters. Egypt J. Anim. Prod. 27, 227±240. Purohit, R., Hudson, R., 1985. Thermography of the bovine

scrotum. AJVR 46, 2388±2392.