High Temperatures on Dairy Cattle Production and Potentially on Milk Composition and Quality - Term Paper Example

High Temperatures on Dairy cattle production and potentially on milk composition and quality Student Name: Institution: Date: Table of Contents Table of Contents 2 1.1 Hot environments and their effects on the performance of dairy cows 3 1.2 Nutrient requirements of dairy cows in a hot environment 4 2.0 Temperature Stress and its effects on the production performance of dairy cows 5 2.1 Thermal equilibrium and Production Performance in Dairy Cows 6 2.2 What happens when a lactating Holstein cow is shifted from a low to high air temperature, for instance, 18 to 30 Celsius? 6 3.0 The Economic Impact of Climate Change on Dairy cow’s production 7 3.1 The Effects of Heat Stress on Milk yield in dairy cows 7 3.2 The impacts of increased ambient temperature on dry matter intake and milk production 8 3.3 How a decrease in food intake causes the daily drop in milk production 9 3.4 Why a decrease in the efficient utilization of energy affects the productivity of dairy cows 9 3.5 Dry matter (DM) intake and milk production 10 Conclusion 11 References 12 1.0 Introduction The increase in ambient temperature, forces the animal’s body to regulate its core body temperature by varying both physiological and metabolic function. However, a number of the behavioral, health and performance difficulties are associated with such alterations. Dairy cattle are considered more susceptible to high ambient temperature compared to other ruminant animals due to their increased metabolic rate as well as inadequate water retention mechanisms within their kidneys and gastrointestinal tract. On the other hand, lactating cattle are largely affected by thermal stress (Bernabucci et.al. 2010). Therefore, intensification of the thermal stress and its frequent occurrence can be considered the most common climatic change issue of global concern in dairy cattle associated with high atmospheric temperature. In the tropical regions, ambient temperature has been pointed out as one of the key climatic constraints affecting dairy productivity. Research indicates that because of the genetic trade-offs required to maintain or control excessive heat in order to boost the potentiality of quality milk production, it is a hard task to control the ambient temperature and humidity being the most common climatic and environmental constraints particularly in the tropical regions (Mellado, 1998). 1.1 Hot environments and their effects on the performance of dairy cows Hot environments affect the productivity or performance of dairy cows in many ways. In order to achieve high performance of such domestic animals, it is crucial for the farmer to modify the diet and environmental conditions particularly the thermal factors such as air temperature, humidity as well as their radiation rate. For example, 4-24oC is required temperature range for the lactating Holstein cows. This clearly indicates that above that temperature, the negative effects of heat stress are experienced which in turn causes a reduction in milk yield in dairy cows above 27oC. Therefore, it can be conclude that a decrease in growth rate, fertility and milk yield in hot environments is mostly associated with an increase within the body temperature of dairy cows (Toda & Ieki, 1999). It is important to note that body temperature of animals can be achieved only if there is a balance between heat production and loss. However, the heat loss of an animal under the extreme temperatures is affected by humidity, and thus leading to a low performance of dairy cows in hot or humid summers. On the other hand, heat production is closely related to the level of feed intake, hence affecting the production level of cows (Jordan, 2003). In general, high production in cows can be achieved in high heat conditions, notwithstanding the pronounced effects of such hot environments. The excessive body temperature of dairy cows in hot environments can be controlled by taking three major steps; sprinkling the cows with water, improvising sheds in the cows’ shed to increase heat loss from the animals. In addition, the environmental temperature can be reduced by changing the structure of the cow shed and ensuring efficient intake of feed energy by controlling the increment of the cows from feeding (Shibata, 1996). 1.2 Nutrient requirements of dairy cows in a hot environment From the feed nutrient utilization point of view, it can be noted that increased loss of sodium and potassium result from heat stress which in turn causes other losses related to increased respiration rate. As a result, the acid-base balance of dairy cows can be altered, creating a metabolic alkalosis. However, cases of decreased efficiency utilization of nutrients can also be experienced in hot environments. Excessive heat and cold stress lowers dairy efficiency because more nutrients are consumed to meet the cow’s maintenance requirements (National Research Council, 2001). In regard to the nutrient requirements of dairy cows reared in hot environments, prediction of the dry matter intake plays an integral role in estimating adequate diet that must be given to the cattle. However, reliable equations on dry matter intake in relation to thermo-neutral zone must be considered (Shioya et.al. 1997). 2.0 Temperature Stress and its effects on the production performance of dairy cows Heat stress in dairy cows is caused when environmental temperature increase beyond the normal thermo-neutral zone. In such conditions, therefore, dairy cows are required to increase their energy intake to enable them maintain their body temperatures and increase their milk production capacities. Research across the world reveals that one of the major consequences of heat stress as far as dairy cows performance is concerned is a decrease in milk production Kadzere et.al. 2002). Heat stress decreases the reproductive performance of dairy cows. Studies indicate that the effects of heat stress on the reproduction in dairy cows can be prolonged and cause great impacts on the animal for a period of months even after being exposed to heat stress. The negative effects of heat stress on the reproductive performance of dairy cows include, decreased fertility rate, growth and development size of the ovarian follicles, reduced fetal growth and the calf size, a decrease in the length and amount of estrus period. Additionally, a high risk of early embryonic deaths is reported. Heat stress causes great impacts on the production and profitability of dairy cows by lowering their reproductive capabilities, milk production and feed intake (Silanikove & Berman, 1997). It is crucial for the farmers to ensure that management and housing alterations are practiced to minimize the impacts caused by heat stress. For example, modern facilities like housing components are being considered to reduce the effects of heat stress. Research on the negative effects of heat stress on the secretary-functioning of the udder shows that heat stress causes low production in dairy grazed in hostile regions. Similarly, a reduction in milk production and fats is caused by high environmental temperatures (Silanikove & Berman, 1997). 2.1 Thermal equilibrium and Production Performance in Dairy Cows Dairy cows being a warm-blooded animal, function and produce efficiently in such environments that they can easily maintain the needed body temperature of 38o C. An increase in the cow’s body temperature causes detectable and harmful effects on tissue maintenance and metabolic functions of the animal. For instance, breakdowns in protein as well as depression in the cow’s production performance deleterious effects recorded (Hahn, 1999). Therefore, it can be concluded that maintain a constant body temperature as thermal equilibrium is key requirement for all productive dairy cows. It is important to note thermal balance and maintenance of its temperature involves balancing heat load and heat dissipation. Thus, effective management of a more productive dairy cow in tropical environments requires the knowledge on how alter heat load and dissipation (McGovern & Bruce, 2000). 2.2 What happens when a lactating Holstein cow is shifted from a low to high air temperature, for instance, 18 to 30 Celsius? The milk yield and composition are the key performance indicators of dairy cows which are affected by heat stress. Therefore, it is crucial for the producers in hot environments to understand the factors that affect the thermal balance as well as the production performance of the lactating Holstein cows. For instance, thermal environments are associated with different aspects such as air temperature, radiation rate and humidity. This implies that effective temperature should be considered a useful indicator for measuring the performance and production of lactating Holstein cows. In this case, shade, fan systems and mist are the methods that can be used to modify the environments in which the dairy cows are reared. Since in hot environments the heat stress causes a low intake of dry matter and the cow’s energy requirements increases, it would be crucial for the person in charge of the animal to increase the amount energy contents of diets taken by the cow. In so doing, the performance of lactating Holstein dairy cows would be maintained in hot environments (Linn, 2004). 3.0 The Economic Impact of Climate Change on Dairy cow’s production The impacts of climate change on dairy cows’ production are more associated with increased ambient temperature. Research shows that an increase in the ambient temperature, forces the body of the dairy cows to regulate its core body temperature by changing the physiological and metabolic functions. Dairy cows are highly affected by increased ambient temperature compared to other ruminants because they posses high metabolic rate and weak mechanisms to retain water within their kidneys and gastrointestinal tract. For example, neonatal and lactating cattle are susceptible to thermal stress (Bohmanova, 2007). 3.1 The Effects of Heat Stress on Milk yield in dairy cows Reduction in milk yield is considered as a major economic impacts caused by climatic stress in dairy cows. Heat stress causes a high decrease in milk yield more in Holstein cows than in Jersey cattle. Due to low synthesis of hepatic glucose as well as Non-Esterified Fatty Acid (NEFA) level within the blood during the period when the cow is experiencing heat stress condition leads to a reduction in glucose supply to the cow’s mammary glands. As a result, low lactose synthesis is recorded which in turn causes low milk yield. Furthermore, a reduction in milk production increases with a decrease in feed intake by the cows to cover for the high environmental temperature (Shearer, 1999). 3.2 The impacts of increased ambient temperature on dry matter intake and milk production West, Mullinix and Bernard carried out an investigation on the effects of hot and humid weather conditions on dry matter intake and milk yield of the lactating dairy cows. The lactating cows were subjected to temperate-hot and humid weather condition so as monitor the effect of high ambient temperature and temperature-humidity index (THI) on dry matter intake and milk yield and temperature. A minimum temperature of approximately 17.9-29 degrees Celsius for the cool period and maximum temperature of 22.5-34.4 degrees Celsius was considered for the hot period. The average THI was 76.6 for the cool period and 83.6 for the hot period. The results of the study indicated that environmental conditions caused less effects on both dry matter intake and milk yield throughout the cool period. However, in the hot period, the THI and mean air temperature caused the greatest impact on dry matter intake and milk yield. Additionally, it was discovered that lactating breeds could maintain their milk temperature in the normal ranges particularly in the cool period, while the milk temperature for Holstein and Jersey breeds decreased throughout the hot period (West, Mullinix & Bernard, 2003). 3.3 How a decrease in food intake causes the daily drop in milk production Low feed intake and diversion of more energy so as to keep the normal functioning of the cow’s body results into negative energy balance that deteriorates the body and health condition of the animal. This means that energy requirements of dairy cows both for maintenance and production purposes must be increased in hot environments as the gross energy efficiency is expected to decrease. Fatty feeds and calcium salts that contain fatty acids have been recommended for use as the ideal approach to improving the management and supply for the dairy cows in summer (Terada, 1996). The decrease in dry matter intake will depend on the duration the heat stress will take in dairy cows. Similarly, dairy cows subjected to heat stress conditions show a decrease in milk production and the decrease. Depending on the severity of the heat stress, the decrease in dry matter intake can occur as transitory or longer term ranging from 10 to 25%. During the summer of 2005, a number of New York dairy cows showed a decrease in milk production. This clearly indicates that when milk production in the early lactation dairy cattle is reduced as a result of heat stress, there would be a reduction in milk production particularly for the lactation. However, dairy cows can in their later stages of production recover progressively from the conditions of heat stress (Casper & Schauff, 2004). 3.4 Why a decrease in the efficient utilization of energy affects the productivity of dairy cows Improved maintenance of energy requirement is crucial for productive performance in dairy cows. It is important to note that dairy cows will often develop mechanisms to dissipate unwanted heat so as to maintain their body temperatures. This can be achieved through increased respiration rate. However, there could be cases of increased maintenance energy requirement by either 20 or 30% within the animals subjected to heat stress. Such conditions decreases energy intake required for productive functions, for instance, milk production. Similarly, blood flow through the animal skin will also go higher in the process of dissipating heat, while blood floe through entire body parts will decrease (Casper & Schauff, 2004). Dairy-drought cows take higher nutrients than oxygen so as to perform their drought work particularly in their early stages of lactation. This is important when nutrient supply is required to meet the needs for lactation, reproductive activities and other works. Dairy cows can adequately meet their needs for work only if they can increase energy intake. It is important to note that supplementary feeding would be required to meet their maintenance needs and productive functions (Gemeda et.al. 1995). 3.5 Dry matter (DM) intake and milk production A reduction in milk production caused by thermal stress is partly associated with a decrease in the cows feed intake. On the other hand, the amount of milk protein and solid-free fat are reduced during the thermal stress in the dairy cows. The decrease in milk yield during higher temperatures is common in dairy cows that provide more milk. However, there is a significant relationship between the amount of milk yielded and the decrease in milk production in respect to an increase in the daily average efficient temperature (Bajagai, 2011). In the same study carried out to analyze the effects of hot and humid weather conditions on dry matter intake and milk yield of the lactating dairy cows, West, Mullinix and Bernard (2003) observed that dry matter intake and milk yield decreased linearly and in accordance with increases in the air temperature in hot period. However, the increase in air temperature caused the milk temperature to increase linearly. This clearly shows that dry matter intake and milk yield had close relationship with the milk temperature. Therefore, producers of dairy cows should focus their environmental changes on the effects of excessive temperatures on dairy cows’ body temperature. In such cases, producers should ensure that they modify the environment at significant times particularly during the day because cows appear to be stressed. The environmental modifications should also take place in the morning hours because it is the time when ambient temperatures are considered to be cooler and cows seem not to be stressed (West, Mullinix & Bernard, 2003). Conclusion Based on the above discussions, it can be concluded that heat stress causes negative effects on the production performance and profitability in dairy cows by decreasing feed intake, milk production and animal reproduction. However, various management as well as housing alterations can be utilized to minimize the huge impacts of heat stress. Effective temperature is an important indicator for measuring the performance and production of lactating Holstein cow. The impacts of climate change on dairy cows’ production are more associated with increased ambient temperature. References Bajagai, Y.S., (2011). The impacts of global climate change on dairy cattle. Nepalese Veterinary Journal, vol. 30, pp. 2-16. Bernabucci, U., Lacetera, N., Rhoads, R. and Nardone, A. 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