Thermorespiratory responses of shorn and unshorn sheep to mild heat stress

Hofman, W. F.; Riegle, Gail D.

doi:10.1016/0034-5687(77)90039-1

Cited by 26 publications

(15 citation statements)

References 18 publications

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“…Results in Table 1 can usefully be compared with values derived from Hofman and Riegle (1977) on three Dorset ewes (62 kg) before and after they were shorn of 66 mm of wool ( Table 2). Values of rectal temperature and respiratory frequency in Table 2 were recorded directly.…”

Section: Resultsmentioning

confidence: 99%

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Temperature and Humidity of Expired Air of Sheep

Johnson¹,

Callahan²,

Strack³

1988

Aust. Jnl. Of Bio. Sci.

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School of Veterinary Studies, Murdoch University, Murdoch, W.A. 6150. AbstractThe temperature and humidity of expired air from three adult Merino sheep were measured at air temperatures of 20, 30 and 40°C before and after the animals were shorn. Expired air was apparently always saturated with water vapour. At the higher air temperatures the temperature of expired air was close to deep body temperature; at lower air temperatures, expired air had been significantly cooled, e.g. to 32· 3°C in shorn sheep at 20°C air temperature. Expired air was cooler from shorn than from unshorn animals at 20 and 30°C air temperature, possibly due to thermally induced vasomotor changes in the upper respiratory tract. Cooling of expired air would be expected to lead to recovery of some of the water evaporated during inspiration; at 20°C air temperature, this fraction was estimated to be 25% in unshorn sheep and 36% in shorn sheep.

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Section: Resultsmentioning

confidence: 99%

“…Direct measurements of the expired air temperature of sheep have been made (Langman et al 1979), but only at one air temperature and wool length. Some reports allow calculation of expired air temperatures under a range of conditions, but these depend on various untested assumptions (Hofman and Riegle 1977;Hammarlund et al 1986). …”

Section: Introductionmentioning

confidence: 99%

Temperature and Humidity of Expired Air of Sheep

Johnson¹,

Callahan²,

Strack³

1988

Aust. Jnl. Of Bio. Sci.

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“…These nighttime effects hold even, as we have shown, under relatively mild summer conditions. Like our goats, sheep have difficulty with heat conservation after shearing, as evident in the decrease in rectal temperature when shorn sheep are exposed to cold environments (Slee, 1966;Webster and Lynch, 1966;Phillips and Raghavan, 1970;Panaretto and Vickery, 1971;Bennett, 1972;Hofman and Riegle, 1977).…”

Section: Discussionmentioning

confidence: 99%

“…The routes for water influx available were only pre-formed water in forage or metabolic water, since we prevented access to drinking water. Shearing increases the food intake (Wheeler et al, 1962;Webster and Lynch, 1966;Hutchinson and McRae, 1969;Avondo et al, 2000) and metabolic rates (Hutchinson and Bennett, 1962;Panaretto and Vickery, 1971;Bennett, 1972;Hofman and Riegle, 1977;Symonds et al, 1986) of sheep, and goats (Holmes and Moore, 1981;Holmes and Clark, 1989), particularly when exposed to cool environmental conditions. Similarly, cold exposure increases the metabolic rate of Angora goats (Wentzel et al, 1979;Fourie, 1984), as indicated by an increased heart rate and blood glucose concentration.…”

Section: Discussionmentioning

confidence: 99%

Shearing at the end of summer affects body temperature of free-living Angora goats (Capra aegagrus) more than does shearing at the end of winter

Hetem

Witt

Fick

et al. 2009

Animal

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Angora goats are known to be vulnerable to cold stress, especially after shearing, but their thermoregulatory responses to shearing have not been measured. We recorded activity, and abdominal and subcutaneous temperatures, for 10 days pre-shearing and post-shearing, in 10 Angora goats inhabiting the succulent thicket of the Eastern Cape, South Africa, in both March (late summer) and September (late winter). Within each season, environmental conditions were similar pre-shearing and post-shearing, but September was an average 58C colder than March. Shearing resulted in a decreased mean ( P , 0.0001), minimum ( P , 0.0001) and maximum daily abdominal temperature ( P , 0.0001). Paradoxically, the decrease in daily mean ( P 5 0.03) and maximum ( P 5 0.01) abdominal temperatures, from pre-shearing to post-shearing, was greater in March than in September. Daily amplitude of body temperature rhythm ( P , 0.0001) and the maximum rate of abdominal temperature rise ( P , 0.0001) increased from preshearing to post-shearing, resulting in an earlier diurnal peak in abdominal temperature ( P 5 0.001) post-shearing. These changes in amplitude, rate of abdominal temperature rise and time of diurnal peak in abdominal temperature suggest that the goats' thermoregulatory system was more labile after shearing. Mean daily subcutaneous temperatures also decreased post-shearing ( P , 0.0001), despite our index goat selecting more stable microclimates after shearing in March ( P 5 0.03). Following shearing, there was an increased difference between abdominal and subcutaneous temperatures ( P , 0.0001) at night, suggesting that the goats used peripheral vasoconstriction to limit heat loss. In addition to these temperature changes, mean daily activity increased nearly two-fold after March shearing, but not September shearing. This increased activity after March shearing was likely the result of an increased foraging time, food intake and metabolic rate, as suggested by the increased water influx ( P 5 0.0008). Thus, Angora goats entered a heat conservation mode after shearing in both March and September. That the transition from the fleeced to the shorn state had greater thermoregulatory consequences in March than in September may provide a mechanistic explanation for Angora goats' vulnerability to cold in summer.

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“…The respiratory rates observed were 134 breaths/minute in shorn and 178 breaths/minute in unshorn rams. In hot, dry heat without solar radiation, Hofman and Riegle (1977) conclude that there was no difference between shorn and unshorn sheep in terms of respiratory frequency or blood gas values. However, Stockman (2006) states that unshorn sheep experienced a downshift in the set point of thermoregulation that resulted in lower threshold for panting.…”

Section: Introductionmentioning

confidence: 95%

Effect of extreme severe heat stress on respiratory rate in unshorn and shorn Australian Merino rams from Northern Patagonia

Armengol

Freund

Giménez

2017

Braz. J. Vet. Res. Anim. Sci.

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The aim of this study was to determine the effects of severe extreme thermal stress on the respiratory rate (panting) of unsheared and sheared rams in standing and lying position, and to analyse two temperature-humidity indices (THIs). Six mature Australian Merino rams from Northern Patagonia, three unshorn and three shorn, were subjected to 40 hours (8 hours each day for five days) of gradual increase in temperature from 25°C to 40°C, guaranteeing 4h daily at 40°C in a heat chamber. Respiratory rate (RR) was registered continuously by counting flank movements, and the ambient air temperature and relative humidity were recorded every five minutes inside the heat chamber. From 1413 RR measurements, descriptive and modelling analyses were performed. Panting as a response variable was distributed into five categories, and fixed effects such as THI, wool (unshorn/shorn), and position (standing/lying) were considered. No significant differences were observed between the panting score in the unshorn (standing or lying) and standing (unshorn or shorn) sheep, but significant differences were observed in shorn and lying rams. The explanations could be that heat production from muscle activity was lower and the transfer and heat lost by conduction to the floor was easier in the rams with shorter fleece (at least 0.7 inches long). However, in the unshorn rams, their wool acted as an insulator, both with air as well as the floor. Australian Merino rams from Northern Patagonia are heat tolerant to an environment between 31.5°C and 42°C, and 32% to 48% humidity for 40 hours over five days. The rams were in the first phase of panting, and the normal rectal temperatures registered daily when leaving the heat chamber confirmed that regulation of body temperature was possible. The LPHSI's THI was adjusted to improve the analysis of the RR more than the National Research Council's THI. Keywords: Australian Merino rams. Heat stress. Respiratory rate. Unshorn / shorn. Standing / lying down. ResumoO objetivo deste estudo foi determinar o efeito do estresse térmico extremamente severo sobre a frequência respiratória (ofego) em carneiros com lã e tosquiados, em pé ou deitados, e analisar dois índices de temperatura e umidade (ITU). Seis carneiros Merino Australiano da Patagônia Norte, três com lã e três tosquiados, foram expostos durante 40 horas a aumento gradual de temperatura de 25 a 40°C (oito horas durante cinco dias), garantindo quatro horas diárias a 40°C em uma câmara de calor. A frequência respiratória foi registrada continuamente mediante a contagem dos movimentos do flanco. A temperatura e a umidade relativa ambiente foram registradas a cada cinco minutos dentro da câmara. A partir de 1.413 frequências respiratórias registradas, uma análise descritiva foi realizada e um modelo calculado. A variável de resposta do ofego foi dividida em cinco categorias e os efeitos fixos considerados foram: ITU, lã (com lã ou tosquiado) e posição (em pé ou deitado). Não se observaram diferenças significativas nas frequências de ofego ...

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Thermorespiratory responses of shorn and unshorn sheep to mild heat stress

Cited by 26 publications

References 18 publications

Temperature and Humidity of Expired Air of Sheep

Temperature and Humidity of Expired Air of Sheep

Shearing at the end of summer affects body temperature of free-living Angora goats (Capra aegagrus) more than does shearing at the end of winter

Effect of extreme severe heat stress on respiratory rate in unshorn and shorn Australian Merino rams from Northern Patagonia

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