Heat Stress, What Impacts on the Broiler's Hormonal System?
- Claudyne Li
- Jun 16, 2020
- 3 min read
article by Claudyne Li
Heat stress
Heat stress is a condition in livestock that causes an increase in temperature or other stressors originating from outside or from inside the body so that biological conditions such as these cause poultry in hot conditions to have difficulty discharging their body heat into the environment. High ambient temperature is the main cause of stress in broiler chickens, in addition to other factors such as humidity, radiation, and air velocity. According to Charles (2002) in Kusnadi and Rahim (2009), the comfortable temperature for growing broiler chickens is 18-22°C, while the daily daytime temperatures in the tropics (lowlands in Indonesia) can reach more than 34°C. Therefore, the development of broiler chickens that are more concentrated in the lowlands is very likely to experience heat stress.
Effect of Heat Stress on the Hormonal System
The decline in production at hot ambient temperatures is partly due to low levels of thyroid hormone, which will reduce general metabolism and protein synthesis, while corticosterone actually increases. The activity of the thyroid gland is closely related to the temperature of the surrounding air. The higher the ambient temperature, the lower the activity of the thyroid gland. This is due to the high temperature of the environment suppressing the expenditure of the hormone thyroxine. In addition to growth is greatly influenced by the consumption of rations and environmental temperature, it is also greatly influenced by the hormonal system, and one of them is the triiodothyronine hormone (T3). Research by Sugito et al. (2007) in Kusnadi and Rahim (2009) proves that the content of the triiodothyronine hormone (T3) in broiler chickens plasma on the 5th day of heat stress treatment has decreased from 1.53 to 1.04 pg/ml. In addition, heat stress turned out to reduce the utilization of the T3 hormone. This is evident from the increased T3 content in the stool, from 2.56 pg/ml in control chickens to 3.11 pg/ml in heat-stressed chickens. This situation is likely to accelerate the decline in production because the T3 hormone plays an important role in growth through increased oxygen consumption and the metabolic system.
Stress conditions will reduce or inhibit the production of thyroid-stimulating hormone (TSH) from the anterior hypophysis so that the production of T3/T4 by the thyroid gland is low. The decrease in production followed by low plasma T3 hormone content in broiler chickens is also evidenced by Ichsan (1990) in Kusnadi and Rahim (2009). The decrease in production under these heat stress conditions, in addition to the low plasma T3 hormone content, is also strengthened by the reduction in nitrogen retention, so that it can reduce the digestibility of proteins and some amino acids but increase plasma corticosterone levels.
The high temperature of the surrounding environment is a factor as a cause of heat stress (Yunianto et al., 1997) so that it causes serious problems for the development and growth of chickens, feed consumption, and accelerated growth due to metabolic disorders in the body. Research by Harlova et al. (2002) showed that heat stress in broiler chickens (daytime temperatures 35-40°C and nighttime 28-30°C), markedly reduced the number of erythrocytes, leukocytes, hemoglobin concentrations, and blood hematocrit values of broiler chickens aged 1 week.
The presence of heat stress also secretes increased glucocorticoid hormones and responds to glucose formation from non-carbohydrate sources. Glucocorticoids hydrolyze tissue proteins and convert them to amino acids that will be carried to the liver. In the liver, these amino acids are further converted into glucose which is then flowed into the blood so that it affects blood sugar levels. The release of glucocorticoids continuously will cause atrophy in lymphoid organs such as the fabricated bursa, thymus, and spleen, while the liver is the center of the detoxification organ and will secrete compounds to neutralize, so it will experience hypertrophy. (CL)
References
Harlova, H., J. Blaha, M. Koubkova, J. Draslarova and A. Fucikova. 2002. Influence of heat stress on the metabolic response in broiler chickens. Scientia Agriculturae Bohemica 33: 145 – 149.
Kusnadi, E. and F. Rahim, 2009. Performa dan Kandungan Hormon Triiodotironin Plasma Ayam Broiler Akibat Pengaruh Cekaman Panas di Daerah Tropis. Media Peternakan, 32: 155-161.
Yunianto, V. D., N. Tigichi, A. Ohtsuka, & K. Hayashi. 1997. Effect of environmental temparature on heat production and muscle protein turnover in layer chickens. J Poult Sci 36: 219 – 228.
Hi Razzaqy! Yes it leads to fatal condition, I think heat stroke is the worst probable case caused by heat stress. But I'm not sure if it could causing seizure. As temperatures increase, the rate of panting increases. If heat production becomes greater over long periods (it will be a chronic heat stress), birds may die eventually.
Good article Claudyne, and if I may, I wanna ask, does heat stress lead to fatal condition such as heat stroke and seizure if left untreated?
No, because exhaust fan is a "must" equipment if someone choose to build a closed-house broiler farm rather than open-house type.
Thankyou for your responses.. Do install exhaust fan would consume more cost?
Thanks Alvin for reading this post👋💜 It's common in broiler closed-house farm using exhaust fan (or it called blower) to balance the temperature both inside and outside their bodies. However, determining the actual ventilation rate in a poultry facility is a difficult and complex task due to the effects of weather, so the airflow of exhaust fans installed in broiler house, as a technique in a ventilation system.