Climate change and livestock : Impacts and mitigation
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P Mayengbam and TC Tolenkhomba
Contd from previous issue
Livestock in higher latitudes will be more affected by the increase of temperatures than livestock located in lower latitudes, because livestock in lower latitudes are usually better adapted to high temperatures and droughts (Thornton et al., 2009). Confined livestock production systems that have more control over climate exposure will be less affected by climate change (Rotter and van de Geijn, 1999).
Ambient temperature higher than 250C with relative humidity greater than 50% has a negative impact on animal productivity. Different livestock species and breeds have different tolerance levels for temperature and humidity. Temperature Humidity Index (THI) has been used to relate animal stress. Animals are comfortable at THI between 65 and 72, under stress from 72 to 78 and under severe stress above 80. THI levels during different parts of the year in India indicate predominance of indigenous or non-descript animals in high THI zones due to their better adaptive capacity and ability to cop up with feed scarcity/harsh environmental conditions.
Heat stress decreases forage intake, milk production, the efficiency of feed conversion, and performance (Haun, 1997; McDowell, 1968; Wyman et a., 1962). Warm and humid conditions cause heat stress, which affects behaviour and metabolic variations on livestock or even mortality.
Heat stress impacts on livestock can be categorized into physiological functions, feed nutrient utilization, feed nutrient utilization and feed intake, milk production, reproduction, livestock health, and efficiency of production system. The following presents these in more detail.
Physiological Functions
The Indian breeds of livestock have capacity to withstand thermal stress, feed and water scarcity, diseases and parasite load. The livestock of tropics are more resilient to environmental and climatic stress due to their genotype and capacity to interact with environment.
Physiological functions of cattle and buffaloes and their change with temperature rise have been evaluated under ambient conditions and in climatic chamber. Physiological responses, surface temperature and sweating rate have been observed to increase due to temperature rise. Body heat storage of crossbreds and buffaloes increased beyond their capacity to tolerate heat particularly on days when THI exceeded 80 during summer and hot humid conditions. Studies further revealed that Zebu breeds of cattle under dry/hot humid conditions have better heat tolerance than crossbreds or buffaloes. The sensitivity of buffaloes to temperature rise above 350C was observed to be higher than either Zebu or crossbreds (Upadhyay et al., 2013)
Livestock species react to environmental challenges by increased synthesis of stress proteins/heat shock proteins. Studies in Sahiwal and crossbred cattle indicated presence of higher HSP70 in Sahiwal than crossbred when the animals were in natural climatic conditions (Prava et al., 2015). When the same animals were subjected to acute heat stress crossbred cattle were found to have higher HSP70 expression (Mayengbam and Upadhayay, 2014) indicating better thermotolerance of Zebu due to presence of higher basal HSP70 and induction of more HSP70 in crossbred to combat acute thermal stress. On the other hand expression of HSP70 of cold adapted goat were found to be stimulated by heat stress while that of heat adapted goats were found to be stimulated by cold stress (Banerjee et al., 2014). Seasonal variation of HSP72, Mn-SOD and Cu,Zn-SOD expression of Sahiwal and crossbred were found to be influenced by heat stress and cold stress (Mayengbam et al., 2015; Mayengbam et al., 2016).
Prolonged high temperature may affect metabolic rate (Webster, 1991), endocrine status (Johnson, 1980), oxidative status (Bernabucci et al., 2002; Mayengbam et al., 2015) glucose, protein and lipid metabolism, liver functionality (reduced cholesterol and albumin) (Bernabucci et al., 2006; Ronchi at al., 1999), non-esterified fatty acids (NEFA) (Ronchi et al., 1999), saliva production, and salivary HCO3- content. In addition, greater energy deficits affect cow fitness and longevity (King et al., 2006).
Feed Nutrient Utilization and Feed Intake
Livestock have several nutrient requirements including energy, protein, minerals, and vitamins, which are dependent on the region and type of animal (Thornton et al., 2009). Impact of temperature changes on feed intake of cattle and buffaloes has been assessed. The analysis of feed intake in relation to changes in Tmax and Tmin indicated that crossbred and buffaloes are sensitive to temperature rise observed during summer and rainy seasons.
Dry matter intake declines with increase in Tmax/Tmin during summer (hot)/rainy (hot humid) season (Mader and Davis, 2004; Thornton et al., 2009; Upadhyay et al., 2013) and dry matter intake increase with decline in Tmin during winter (Upadhyay et al., 2013).
Sodium and potassium deficiencies under heat stress may induce metabolic alkalosis in dairy cattle, increasing respiration rates (chase, 2012; Rojas-Downing et al. 2017).
(To be contd)
Contd from previous issue
Livestock in higher latitudes will be more affected by the increase of temperatures than livestock located in lower latitudes, because livestock in lower latitudes are usually better adapted to high temperatures and droughts (Thornton et al., 2009). Confined livestock production systems that have more control over climate exposure will be less affected by climate change (Rotter and van de Geijn, 1999).
Ambient temperature higher than 250C with relative humidity greater than 50% has a negative impact on animal productivity. Different livestock species and breeds have different tolerance levels for temperature and humidity. Temperature Humidity Index (THI) has been used to relate animal stress. Animals are comfortable at THI between 65 and 72, under stress from 72 to 78 and under severe stress above 80. THI levels during different parts of the year in India indicate predominance of indigenous or non-descript animals in high THI zones due to their better adaptive capacity and ability to cop up with feed scarcity/harsh environmental conditions.
Heat stress decreases forage intake, milk production, the efficiency of feed conversion, and performance (Haun, 1997; McDowell, 1968; Wyman et a., 1962). Warm and humid conditions cause heat stress, which affects behaviour and metabolic variations on livestock or even mortality.
Heat stress impacts on livestock can be categorized into physiological functions, feed nutrient utilization, feed nutrient utilization and feed intake, milk production, reproduction, livestock health, and efficiency of production system. The following presents these in more detail.
Physiological Functions
The Indian breeds of livestock have capacity to withstand thermal stress, feed and water scarcity, diseases and parasite load. The livestock of tropics are more resilient to environmental and climatic stress due to their genotype and capacity to interact with environment.
Physiological functions of cattle and buffaloes and their change with temperature rise have been evaluated under ambient conditions and in climatic chamber. Physiological responses, surface temperature and sweating rate have been observed to increase due to temperature rise. Body heat storage of crossbreds and buffaloes increased beyond their capacity to tolerate heat particularly on days when THI exceeded 80 during summer and hot humid conditions. Studies further revealed that Zebu breeds of cattle under dry/hot humid conditions have better heat tolerance than crossbreds or buffaloes. The sensitivity of buffaloes to temperature rise above 350C was observed to be higher than either Zebu or crossbreds (Upadhyay et al., 2013)
Livestock species react to environmental challenges by increased synthesis of stress proteins/heat shock proteins. Studies in Sahiwal and crossbred cattle indicated presence of higher HSP70 in Sahiwal than crossbred when the animals were in natural climatic conditions (Prava et al., 2015). When the same animals were subjected to acute heat stress crossbred cattle were found to have higher HSP70 expression (Mayengbam and Upadhayay, 2014) indicating better thermotolerance of Zebu due to presence of higher basal HSP70 and induction of more HSP70 in crossbred to combat acute thermal stress. On the other hand expression of HSP70 of cold adapted goat were found to be stimulated by heat stress while that of heat adapted goats were found to be stimulated by cold stress (Banerjee et al., 2014). Seasonal variation of HSP72, Mn-SOD and Cu,Zn-SOD expression of Sahiwal and crossbred were found to be influenced by heat stress and cold stress (Mayengbam et al., 2015; Mayengbam et al., 2016).
Prolonged high temperature may affect metabolic rate (Webster, 1991), endocrine status (Johnson, 1980), oxidative status (Bernabucci et al., 2002; Mayengbam et al., 2015) glucose, protein and lipid metabolism, liver functionality (reduced cholesterol and albumin) (Bernabucci et al., 2006; Ronchi at al., 1999), non-esterified fatty acids (NEFA) (Ronchi et al., 1999), saliva production, and salivary HCO3- content. In addition, greater energy deficits affect cow fitness and longevity (King et al., 2006).
Feed Nutrient Utilization and Feed Intake
Livestock have several nutrient requirements including energy, protein, minerals, and vitamins, which are dependent on the region and type of animal (Thornton et al., 2009). Impact of temperature changes on feed intake of cattle and buffaloes has been assessed. The analysis of feed intake in relation to changes in Tmax and Tmin indicated that crossbred and buffaloes are sensitive to temperature rise observed during summer and rainy seasons.
Dry matter intake declines with increase in Tmax/Tmin during summer (hot)/rainy (hot humid) season (Mader and Davis, 2004; Thornton et al., 2009; Upadhyay et al., 2013) and dry matter intake increase with decline in Tmin during winter (Upadhyay et al., 2013).
Sodium and potassium deficiencies under heat stress may induce metabolic alkalosis in dairy cattle, increasing respiration rates (chase, 2012; Rojas-Downing et al. 2017).
(To be contd)