With the rapid development of intensive broiler breeding, a variety of stress factors are increasing, especially the stress caused by high temperatures in summer. Summer heat exceeds the body's ability to regulate the body, causing a series of systemic reactions known as heat stress.
Because broilers grow fast, are large in size, thick in skin, and have more subcutaneous and abdominal fat, they have poor resistance to heat stress. During the summer, their growth is easily affected by heat stress, and even causes a large number of deaths. Summer temperatures are high, high-density feeding causes widespread heat stress in broilers, lower production performance, reduced immune function, increased mortality from morbidity, and brings significant economic losses to broiler husbandry, which should attract attention and attention.
Heat stress reduces the chicken's feed intake, production performance, feed efficiency, and product quality by changing various physiological and biochemical reactions of the chicken. It is generally believed that the suitable growth temperature for medium and large broilers is 18-24°C. When the temperature reaches 26°C, the chicken can also contact the outside air with the respiratory mucosa to dissipate heat; at 28°C or above, the chicken heat stress begins to show obvious; At 32°C, chickens are unable to exhaust excessive calories simply by breathing through their mouths. In particular, under high humidity conditions, heat stress is more severe.
Heat stress affects physiological and biochemical changes in broilers
When the temperature of the external environment increases, the temperature of the chicken body will increase with the increase of the ambient temperature. At this time, the heart rate will increase, the blood pressure will decrease, the breath will increase, the patient will suffer wheezing, respiratory alkalosis will occur severely, the PH value of the blood will rise, and the blood sodium will rise. High, decreased potassium, sodium and potassium imbalance. Blood glucose, total protein, globulin and albumin concentrations decreased. In addition, heat stress can also lead to endocrine disorders, corticosterone concentration increased significantly in the early heat stress, but the prolonged stress time gradually decreased, decreased thyroid hormone secretion, decreased activity, leading to reduced metabolic rate.
Heat stress affects broiler growth rate and feed intake
Generally, broilers are kept at an ambient temperature of 18-24°C to achieve better growth rates and better feed conversion rates. When the ambient temperature exceeds 26°C, the feed intake of broilers decreases, and the growth rate begins to slow down. Experiments have shown that, when the ambient temperature is 21-30°C, the feed intake decreases by 1.5% for every 1°C increase, and within the range of 32-38°C, the intake decreases by 4.6% for every 1°C increase in ambient temperature.
Heat stress affects broiler disease resistance
High temperature and high humidity are good conditions for many species of parasites, pathogens, etc. to multiply. During heat stress, the immunity of broilers is inhibited, and chickens are prone to respiratory diseases, ulcerative colitis, etc., and are vulnerable to Staphylococcus, Escherichia coli, and Pseudomonas aeruginosa. Newcastle disease, infectious laryngotracheitis, etc. Susceptibility increased.