Effect of climate change on animal production of milk, meat and eggs
Rising temperatures and climate change have had significant negative effects on agriculture, which increasingly affects animal production. Climate change will have a major impact on animal husbandry and feed production.
Cattle have an optimum temperature zone that allows them to maintain their body temperature without affecting their normal physiological functions. As the temperature increases, it can exceed this thermal neutral zone and cows can In response to this increase, metabolism, respiratory rate, heart rate, gasping respiration and sweating are altered, and chemical and hormonal changes occur . These factors reduce their growth rate (weight and bulk) and fat and negatively affect reproductive function, and there are many ways to lose heat. The rate of evaporative heat loss is highest in normal cases, and it depends on the surrounding air temperature, relative humidity, evaporation area, speed of movement of the air and its ability to lose heat by conduction is very low. As for the heat loss by convection, it increases with the wind blowing on the animal, and if the heat loss increases by evaporation. of the climate on livestock water consumption has several aspects. Water is an essential food source for livestock and, on the other hand, it is a vector of heat loss and evaporative cooling. Thus, warming oceans increase livestock water consumption, but higher temperatures combined with higher humidity reduce the amount of water used and increase the number of times livestock need to drink.
Milk production generally decreases in summer due to continued exposure to heat, and a temperature increase of 1 degree Celsius above the prevailing average temperature has been found to negatively affect approximately 10% of milk production during the stress period and about 8 to 10% of meat production during this period. Milk production is not only related to feed intake and quality, but also to the high temperatures to which livestock are exposed. With high temperatures, the physiological processes associated with lactation are affected, in addition to a decrease in the level of thyroid hormone during the summer, and the components of milk change according to high temperatures. It has been found experimentally that high temperatures Heat leads to a decrease in the amounts of fat and non-fat in milk. Daily milk production is strongly affected by climate change. An increase in temperature and humidity leads to a significant increase in temperature and a decrease in milk production. found lower values of milk fat content when the THI value of the temperature and humidity index was greater than 75.
Heat stress does not affect milk lactose, which is the main component of milk after water. Studies have shown that milk lactose intake does not differ significantly between cows kept at a temperature-humidity index. 75. Cow’s milk is rich in casein and represents about 77% of the total. milk proteins. This is one of the important factors that bring him into the cheese industry. The protein content of milk decreases when the value of the temperature and humidity index is higher. From 75 (3.02 g/100 g) for a temperature and humidity index 75, respectively).
Heat stress in beef cattle can increase the risk of death. Heat stress has a significant adverse effect on the qualities and characteristics of meat. This can reduce the wholesomeness of the meat and can lead to the transfer of pathogens, as the microorganisms are active at temperatures specific to each organism. Increased stomach pH increases the potential for foodborne pathogens (e.g., Escherichia coli, Salmonella, and Campylobacter) to be able to pass through the stomach and colonize the distant and secreted gastrointestinal tract into the environment. injury For severe infections and inflammation, due to increased secretion of stress hormones and increased mucosal permeability, animals may carry more pathogens through the gastrointestinal tract and associated lymphoid tissues. An important factor affecting meat quality is pH, which is one of the most frequently used chemical indicators that affect meat quality. Muscle pH can drop rapidly due to accelerated anaerobic glycolysis in muscle during and/or after slaughter. Accelerated anaerobic glycolysis causes a series of chemical reactions to rapidly lower pH due to the conversion of glycogen to lactic acid in the muscles. Heat stress affects body weight, carcass height and weight, and animal fat thickness. Severe heat stress leads to increased pH and darkness. This results in an adrenergic stress response being activated. Peripheral vasodilation and muscle glycogenolysis are induced by adrenaline activity.
In response to various stressors, corticotropin-releasing factor (CRF) is released from the parvocellular neuron of the paraventricular nuclei (PVN) of the hypothalamus into the pituitary portal vein to stimulate corticotropin cells of the anterior pituitary which release adrenocorticotropic hormone (ACTH) in the systemic circulation. ACTH binds to the melanocortin type 2 receptor in the adrenal cortex, thereby releasing glucocorticoids primarily cortisol into the circulation. Mineralocorticoids: Chronic heat stress increases mineralocorticoid secretion via the hypothalamic-pituitary HPA axis. It causes the retention of water and mineral balance in the body and contributes to the maintenance of blood volume and blood pressure. Studies have shown that in heat-stressed animals, T3 concentration gradually decreases while T4 concentration decreases, increases via the hypothalamic-pituitary-thyroid (HPT) axis. TSH secretion is also inhibited by heat stress to reduce heat generation and basal metabolic rate.
Heat stress is a condition in which chickens are unable to balance body heat production and heat loss. Heat stress is caused by the interaction of various factors such as high temperature, humidity and heat. The normal body temperature for chickens is 41-42°C, and the moderate temperature to maximize growth is between 18-21°C. A temperature above 25°C causes heat stress in poultry. When the birds are exposed to a temperature higher than a temperature suitable for them, the birds try to dissipate the excess heat produced inside the body, which manifests itself in certain behavioral changes in the birds. Heat-stressed chickens spend less time walking upright, chickens consume less feed and more water, and they open their wings in an attempt to reduce this stress. Their gasping rates also increase. egg shape is less affected by high temperature in older hens than in younger ones. But the density of the spawn is more affected by the severe thermal stress (37 degrees Celsius) at the end of lay than at the start of lay. Periodic temperature changes reduce the effect of heat stress by providing recovery periods for birds during cold spells. As for the genotype, the most productive genotypes are more affected than the less productive, and the genotypes of brown eggs, heavier in weight and more feathery, are more affected by heat stress than white eggs. There is a negative effect of heat stress on feed consumption as a 10% decrease was observed at 24°C, and for important production traits such as egg mass, egg production rate eggs, egg weight and shell strength with a 5% loss at lower temperatures. (24-29°C) .Chicken diets that contain vitamins A and C improve live weight, egg weight, egg yolk weight, egg white weight, and egg weight. eggshells under heat stress conditions. Antioxidant supplements can also be used under heat stress conditions.
Recommendations to prevent heat stress:
It is important to raise awareness of all actors in animal production on climate-smart livestock projects. Climate information and knowledge of its effects should be collected, then technical advice to help farmers to optimally manage climate risks and reduce the negative impact of drought on profits, and local species should be improved by crosses with heat and disease resistant genotypes. to ensure better adaptation and resistance to races. The concentration level of vitamins and minerals must be increased to improve the health of cattle, and farmers must be trained in the use of additional hormones such as progesterone and the improvement of heat synchronization in females. through GnRH to improve fertility efficiency.
- Wissam Dayoub, Msc. Animal Husbandry of Faisalabad University of Agriculture
- Mahvish Rajput, PhD. Parasitology from Faisalabad University of Agriculture
- Dr Muhammad Sohail Sajid, Associate Professor (Full) Department of Parasitology at
Faisalabad University of Agriculture