about 38.99 - 39.27 0 C; skin temperature: 35.39 - 36.51 0 C and heart rate: 66.36 - 66.94 times/minute. This shows that sheep raised in environmental conditions in Thua Thien Hue, although different from the traditional environment (Ninh Thuan), the body temperature, heart rate and skin temperature of the sheep remain stable.
Meanwhile, the respiratory rate of sheep raised in Thua Thien Hue tended to be significantly higher than that in Ninh Thuan (P<0.05). This may be because in Thua Thien Hue, although the air temperature is high, the humidity is always high (annual average is 87.3% compared to 78% - Ninh Thuan), which limits the heat dissipation of sheep through the skin, so sheep have to increase their respiratory rate to release heat. Many research results have shown that increasing respiratory rate is an important heat dissipation pathway in sheep. In conditions of high temperature, accompanied by high humidity or saturation, heat dissipation by evaporation is hindered, so sheep have to release heat into the environment by increasing their respiratory rate to balance their body temperature (Alhidary et al., 2012; Fadare et al., 2012; McManus et al., 2008; Marai et al., 2008).
2009; Bhatta et al., 2005; Bhattacharya and Uwayjan, 1975). According to Srikandakumar et al. (2003), when the ambient temperature increases from 32 0 C or more, the humidity is about 65%, the body temperature of sheep begins to increase, leading to a significant increase in the respiratory frequency of sheep. According to Sarage et al. (2008), the respiratory frequency of sheep raised in hot rooms (30 - 40 0 C) is higher than that of cool rooms (20 0 C) (206 vs. 149 times/minute). Al-Haidary (2004) also reported that the respiratory frequency of sheep under heat stress conditions (33 - 38.5 0 C) is 80 times/minute, while at 23.6 0 C it is 61 times/minute.
On the other hand, sheep are livestock with less developed sweat glands compared to some other homeothermic animals such as buffalo and cows. At the same time, sheep have thick fur so they lose heat through the skin very poorly. Therefore, in high temperature conditions, sheep must increase their respiratory rate to release heat (Marai et al., 2007; Bhatta et al., 2005). According to Marai et al. (2007), about 20% of sheep's body heat is released through respiration.
in an environment with a temperature of 12 0 C, but up to 60% at high ambient temperatures (35 0 C). Aleksiev (2008) reported that the respiratory frequency of Tsigai sheep in the morning was 36.6 times/minute and in the afternoon was 55.9 times/minute; after shearing, the respiratory frequency of sheep decreased significantly, to 16.6 and 20.6 times/minute, respectively. According to Singh et al. (1980), at a temperature of 20 0 C, the respiratory frequency of Chokla sheep was lower than that of Sirohi goats (22 vs. 26 times/minute), but at a temperature of 42.4 0 C after 30 minutes, the respiratory frequency of Chokla sheep was much higher than that of Sirohi goats. According to Adam and McKinley (2009), the respiratory rate of normal sheep is about 15 - 40 times/minute, in changing environmental conditions the respiratory rate can reach a maximum of 350 times/minute. Therefore, although the results of evaluating the respiratory rate of sheep raised in Thua Thien Hue conditions are higher than those raised in Ninh Thuan, the respiratory rate of sheep in this study is still within the normal physiological range of sheep.
Thus, the temperature and humidity conditions in Thua Thien Hue did not affect the heart rate, body temperature and skin temperature of sheep. Initial results showed that Phan Rang sheep have the ability to adapt to the environment in Thua Thien Hue.
3.2.2. Relationship between temperature, humidity and THI with body temperature
3.2.2.1. Relationship between temperature and body temperature
The results of the study on the relationship between barn temperature and sheep body temperature are presented in graph 3.3.
In the range from 17.5 to 33.5 0 C, the relationship between barn temperature (x 1 , 0 C) and sheep body temperature (Y 1 , 0 C) is expressed through the following quadratic correlation equation:
Y 1 = 0.0014x 1 2 - 0.0305x 1 + 38.76 R 2 = 0.77; P = 0.001
y = 0.0014x 2- 0.0305x + 38.76 R 2 = 0.7722
39.6
Body temperature (0 C)
39.4
39.2
39.0
38.8
38.6
38.4
15 17 19 21 23 25 27 29 31 33 35
Temperature (0C)
Graph 3.3. Quadratic relationship between temperature and body temperature of sheep
Calculating the increase in body temperature of sheep at different barn temperature ranges: ≤22.5; >22.5-26.3; >26.3-29.5 and >29.5 0 C showed that the body temperature had a statistically significant difference (P<0.05) (Table 3.6).
Table 3.6. Temperature levels affecting body temperature
Temperature ( 0 C)
Body temperature ( 0 C) | ||
Oscillate | M ± SEM | |
≤22.5 | 38.69 - 38.80 | 38.72a * ± 0.02 |
>22.5 - 26.3 | 38.80 - 38.90 | 38.85b ± 0.01 |
>26.3 - 29.5 | 38.99 - 39.04 | 39.02c ± 0.02 |
> 29.5 | 39.10 - 39.32 | 39.20d ± 0.02 |
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*Data in the same column with different superscripts are statistically different (P<0.05)
Data in Table 3.6 show that in the temperature range from 17.5 to 22.5 0 C, the body temperature of sheep is relatively stable, averaging 38.7 0 C. When the temperature increases in the range from >22.5 - 26.5; >26.5 - 29.5 and >29.5 0 C, the body temperature of sheep increases by 0.13; 0.17 and 0.18 0 C, respectively. As is known, sheep are homeothermic animals, body temperature is one of the fairly stable physiological indicators. This stability is due to the regulation of many factors in the body. However, when the environmental temperature is too high (equal to or higher than body temperature), it affects the heat dissipation process, the ability to release heat from the body to the environment is limited, the body accumulates heat, leading to an increase in the sheep's body temperature.
Although the increase in ambient temperature increased the body temperature of sheep (38.69
- 39.32 0 C) but the body temperature is still within the normal physiological range. The results in this study are also consistent with previous studies (Alhidary and CS., 2012; McManus and CS., 2008; Bhatta and CS., 2005). Srikandakumar and CS. (2003) said that the body temperature of sheep increased significantly when the environmental temperature was >32 0 C. The environmental temperature increased by 14.2 0 C (23.2 - 37.4 0 C), the body temperature of Merino sheep (Australia) increased by 0.7 0 C (39.03 - 39.10 0 C) (Alhidary and CS., 2012). According to McManus and CS. (2008), morning temperature 17.28 - 23.6 0 C body temperature of Santa Ines sheep (Brazil) is 38.25 0 C, afternoon temperature 19.46 - 27.32 0 C body temperature of sheep is 39.44 0 C.
3.2.2.2. Relationship between humidity and body temperature
The relationship between barn humidity and sheep body temperature is presented.
in graph 3.4.
In the air humidity range from 56 - 93%; the correlation between humidity
(x 2 , %) with sheep body temperature (Y 2 , 0 C) as follows: Y 2 = 0.0055x 2 2 - 0.043x 2 + 40.58
R 2 = 0.64; P = 0.001
y = 0.0055x 2- 0.0243x + 40.58 R 2 = 0.6405
39.6
39.4
Body temperature (0 C)
39.2
39.0
38.8
38.6
38.4
50 55 60 65 70 75 80 85 90 95 100
Humidity (%)
Graph 3.4. Quadratic relationship between humidity and body temperature of sheep
Through calculating the value of sheep's body temperature decreasing corresponding to a 2.5% increase in humidity, it shows that; when humidity is 59 - 75%, the average sheep's body temperature is 39.21 0 C; when humidity increases from >75 - 90%, the sheep's body temperature decreases by 0.36 0 C; when humidity >90%, the sheep's body temperature decreases by 0.48 0 C, this difference is statistically significant (P<0.05) (Table 3.7).
Table 3.7. Humidity levels affecting body temperature
Humidity (%)
Body temperature ( 0 C) | ||
Oscillate | M ± SEM | |
59 - 75 | 39.1 - 39.3 | 39.21a * ± 0.02 |
>75 - 80 | 39.0 - 39.1 | 39.03b ± 0.03 |
>80 - 90 | 38.8 - 38.9 | 38.85c ± 0.03 |
>90 | 38.7 - 38.8 | 38.73d ± 0.03 |
*Data in the same column with different superscripts are statistically different (P<0.05)
Air humidity affects the thermal balance of animals. However, the impact of humidity depends on the combination with environmental temperature. When high environmental humidity combined with low environmental temperature increases heat dissipation in sheep, leading to a decrease in body temperature. According to Alhidary and CS. (2012), humidity of 49.8% and temperature of 37.4 0 C, the body temperature of Merino sheep (Australia) is 39.10 0 C, when humidity increases to 51.9% and temperature of 23.2 0 C, the body temperature of sheep decreases to 39.03 0 C. Santa Ines sheep (Brazil) in the morning humidity is 89.7%, body temperature is 38.25 0 C; in the afternoon humidity is 70.3%, the body temperature of sheep is 39.44 0 C (McManus and CS., 2008). Research by authors Fadare and CS. (2012), Marai et al. (2009), Bhatta et al. (2005), Srikandakumar et al. (2003) also gave similar results.
3.2.2.3. Relationship between THI and body temperature
The results of the study on the relationship between THI and body temperature of sheep are presented in graph 3.5.
y = 0.0025x 2 - 0.0775x + 39.247
39.6 R 2 = 0.773
39.4
Body temperature (0C)
39.2
39.0
38.8
38.6
38.4
15 17 19 21 23 25 27 29 31 33
EXAM
Graph 3.5. Quadratic relationship between THI and body temperature of sheep
In the range of THI from 17.2 to 31.5, the relationship between THI (Y 3 ) and body temperature (x 3 , 0 C) is shown by the following quadratic correlation equation:
2
Y 3 = 0.0025x 3 - 0.0775x 3 + 39.247 R 2 = 0.64; P = 0.001
The change in body temperature according to THI value and the rating scale of Marai et al. (2000) is as follows (Table 3.8).
Table 3.8. THI milestones affecting body temperature
EXAM
Body temperature ( 0 C) | ||
Oscillate | M ± SE | |
≤22.2 | 38.69 - 38.78 | 38.72a * ± 0.02 |
>22.2 - 23.3 | 38.80 - 38.85 | 38.82b ± 0.03 |
>23.3 - 25.6 | 38.85 - 38.94 | 38.90b ± 0.02 |
>25.6 - 28.5 | 38.91 - 39.01 | 39.01c ± 0.02 |
>28.5 | 39.09 - 39.30 | 39.20d ± 0.02 |
*Data in the same column with different superscripts are statistically different (P<0.05)
The results of Table 3.8 show that the body temperature of sheep has statistical differences when THI is at levels ≤22.2; >22.2 - 25.6; >25.6 - 28.5 and >28.5 (P<0.05). However
However, in the range of THI >22.2 - 26.5, the body temperature of sheep did not have any statistical difference (P>0.05). This result shows that the effect of THI on body temperature should be divided into 4 levels ( ≤ 22.2; >22.2 - 25.6; >25.6 - 28.5 and >28.5) instead of 5 levels.
Calculation of body temperature increase at THI levels shows that, THI ≤ 22.2, the average body temperature of sheep is 38.72 0 C. When THI increases in the range
>22.2 – 25.6; >25.6 – 28.5 and >28.5, the sheep's body temperature increased by 0.18, 0.29 and 0.48 0 C respectively. Body temperature fluctuated due to changes in THI, when THI increased, it increased the sheep's body temperature. Normally, the sheep's body temperature is stable thanks to the body's heat generation and heat dissipation process. However, when THI is high, it exceeds the body's ability to regulate body temperature, the balance between heat generation and heat dissipation is lost, causing body temperature to change.
The results of this study are consistent with previous studies (Alhidary et al., 2012; Bhatta et al., 2005; Marai et al., 2009). The authors reported that high body temperature values of sheep often correspond to high THI values. According to Marai et al. (2009), the body temperature of Suffolk sheep when THI = 14.5 was 38.7 0 C and THI = 25.6 was 39.8 0 C. McManus et al. (2008) also reported that the body temperature of Santa Ines sheep (Brazil) when THI = 19.05 was 38.25 0 C; when THI = 24.04 the body temperature of sheep was 39.44 0 C.
3.2.3. Relationship between temperature, humidity and THI with respiratory frequency
Respiratory rate is an important heat dissipation pathway and a predictor of heat stress in sheep. The results of the calculations of the relationship between temperature, humidity and THI with respiratory rate of sheep are shown as follows.
3.2.3.1. Relationship between temperature and respiratory rate
The results of the evaluation of the relationship between barn temperature and respiratory rate of sheep in Thua Thien Hue are presented in graph 3.6.
y = 0.1888x 2- 6.3093x + 68.205
R 2 = 0.8147
90
Respiratory rate (times/minute)
80
70
60
50
40
30
20
10
0
15 17 19 21 23 25 27 29 31 33 35
Temperature (0C)
Graph 3.6 . Quadratic relationship between temperature and respiratory rate of sheep