Fat-tailed Awassi and German Mutton Merino sheep under semi-arid conditions: 3. Body temperatures and panting rate

Abstract

Rectal, external auditory meatus and skin temperatures and panting rates were measured in native fat-tailed Awassi and imported German Mutton Merino (GMM) sheep. The Awassi evolved under desert conditions, have a localized fat deposit, coarse carpet wool, long pendulous ears and long, spiral horns (males). In contrast, the GMM evolved under temperate conditions, have well-distributed fat, medium fine wool, short, straight ears and are polled. The study was carried out during the summer in the northern part of the Negev desert.The mean daily rectal temperature fluctuation was higher (P < 0-01) in the GMM than in the Awassi (1-78 °C v. 1-08 °C). The external auditory meatus temperature was lower than the rectal temperature by 1-5 °C in the GMM and by 1-7 °C in the Awassi, indicating a cooler brain temperature. The maximum skin temperature was similar to the maximum rectal temperature in both breeds, thus sweating was of little importance. The panting rate of the GMM increased fivefold (40-6-199-4 pants/min) whilst the rate of the Awassi increased fourfold (35-3-135-0 pants/min).There was no between-breed difference in either the rectal temperature or panting rate until 25-30 °C ambient temperature and it is thought that the higher rectal temperature of the GMM at this ambient temperature might have triggered off the higher panting rate. It seems that the GMM use panting to a greater extent than the Awassi whereas the Awassi dissipate heat through the skin more efficiently than the GMM. It is concluded that both breeds are thermostable, much of the between-breed difference in rectal temperature can be attributed to their anatomical differences.

Water Stress in Small Ruminants

“…Pregnant and lactating animals have 40-50% higher water turnover rates than dry animals [17]. However, Degen (1977) [35] recorded a small difference in water turnover between control and pregnant Awassi and Merinos sheep.…”

“…Aspirin did not have any effect on rectal temperature; perhaps these results highlight the capacity of Awassi to remain thermostable even under dehydration [10,35]. No changes were detected in PCV and hemoglobin levels [62] confirming that salicyclates do not usually alter these two parameters [188].…”

“…Therefore, thermostability could be maintained without directly resorting to evaporative cooling (panting) which leads to high water loss [34]. Location of body fat also affects heat dissipation rates: arid-adapted sheep exhibit highly localized fat storage [35], such as in the fat-tail, as opposed to high subcutaneous fat in non-adapted breeds; this again facilitates heat conductance to the periphery for dissipation [34]. Moreover, fat-tails are important energy reserves that help in buffering long-term dietary shortfalls to maintain survival and productivity [36,37].…”

Fluid Balance in Ruminants: Adaptation to External and Internal Challenges

“…Some, like the Bedouin goats that can produce milk up to about 10% of their body weight, keep a large extracellular volume when fully hydrated. 7 The Moroccan black goat 8 and Awassi sheep, 9 on the other hand, produce small amounts of milk and have a low water turnover. Pastoralists often use intermittent watering in the desert.…”

Effect of Pre-Mating Water Deprivation on Ovarian Activity and on Reproductive Traits of Mature Barbarine Ewes during Summer Season

“…Hyperthemia is one of mechanisms that allow animals to avoid excessive water expenditure during the hot part of the dayespecially as our study was conducted during the warmer months of the year. On the other side, authors reported that sheep are thermostable even during dehydration [14].…”