Climate change and livestock : Impacts and mitigation
- Part 2 -

P Mayengbam / TC Tolenkhomba *

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).

Thermal livestock stress decreases efficiency of feed conversion (McDowell, 1968), especially for livestock that are fed large amounts of high-quality feeds (Huan, 1997). In the case of cattle, feed intake reduction leads to a negative energy balance and reduced weight gain (Lacetera et al., 1996, 2003). Reduction of water intake may also decrease sweating and feed intake (Henry et al., 2012).

Milk Production

The potential direct effects of possible climate change and global warming on milk production of indigenous, crossbred cattle and buffaloes have been evaluated using widely known global circulation model United Kingdom Meteorological Office (UKMO) to represent possible scenarios of future climate (Ruosteenoja et al., 2003). The studies indicate tat production of livestock is greatly impacted by temperature variations and rise in temperature.

Studies with UKMO indicate a temperature rise of 1.0 or 1.20C with minor change in precipitation during March-August for India (Region 23-HADCM3 A2/B2 scenario) will marginally affect ilk production and during other months productivity will remain relatively unaffected.

A small rise in temperature due to climate change is not likely to impact physiological functions of animals due to their adaptive capacity. But physiological functions like milk production and reproductive will be adversely impacted by projected temperature rise of more than 40C over existing temperatures for time slice 20170-2099 (Upadhyay et al., 2013).

The negative impact of temperature rise on total milk production for India has been estimated about 1.6 million tons in 2020 and more than 15 million tons in 2050. Northern India is likely to experience more negative impact of climate change on milk production of both cattle and buffaloes due to rise in temperature during 2040-2069 and 2070-2099 (Upadhyay et al., 2007, 2008a).

A sudden change in temperature, either a rise in Tmax during summer i.e. heat wave or fall in Tmin during winter i.e. cold wave; cause a decline in milk yield. Both increase in Tmax (>40C above normal) during summer and decline in Tmin (>30C than normal) during winter negatively impact milk production of crossbred cattle and buffaloes (Upadhayay et al., 2013). The decline in yield varies from 10-30% in first lactation and 5-20% in second and third lactation.

The extent of decline in milk yield occurs less at mid gestation stage than either late or early stage. The negative impact of cold wave or heat wave on milk yield of buffaloes are not only observed on next day of extreme event but also on the subsequent day(s), thereby indicating that heat and cold waves cause short to long term cumulative effect on milk yield takes 2-5 days normally, however a variable response may also be observed in individual depending on stage of lactation (Upadhayay et al., 2013).

A rise in temperature due to global warming will impact high producing animals and they need to be cooled artificially either by sprinklers or by increasing wind velocity or air movement to sustain milk production. High producing crossbred cows vulnerable to thermal stress and unable to maintain thermal through skin and pulmonary evaporation requires protection from direct solar radiation during summer water use for animals’ intake and maintenance.

Animal Reproduction

Reproduction efficiency of both livestock sexes may be affected by heat stress. The livestock species more vulnerable to climate changes are cattle and buffaloes than sheep and goats. In most agro-climatic zones of India the average temperature throughout the year is in the range of mild to moderate stress of IHI range. THI levels during the year indicate that animals are under constant stress from March to October at about 200 locations spread all over India except high altitudes (Upadhyay et al., 2013).

Animals maintained under open housing conditions in rural sector exhibit seasonality in breeding and reproductive rhythm and in some cases the marked seasonal variations are observed. The incidence of calving is predominant in a precise period from October to March. The climate change scenario leading to a rise in temperature with higher intensity of radiant heat load is likely to impact reproductive rhythm through pineal-hypothalamo-hypophyseal-gonadal axis.

The effects may be more pronounced in animal species like buffaloes, which due to higher thermal loads and limited capacity to dissipate heat may be severely stressed. Scarcity of water resources may further compound effects on production. Therefore, mitigation measures and strategies need to be adopted not only to reduce stress on animals but also to curtail fertility losses and other health consequences thereof.

In cows and pigs, it affects oocyte growth and quality (Barati et al., 2008; Ronchi et al., 2001), impairment of embryo development, and pregnancy rate (Hansen, 2007; Nardone et al., 2010; Wolfenson et al., 2000).

Cow fertility may be compromised by increased energy deficits and heat stress (De Rensis and Scaramuzzi, 2003; King et al., 2006). Heat stress has also been associated with lower sperm concentration and quality in bulls, pigs, and poultry (Karaca et al., 2002; Kunavongkrita et al., 2005; Mathevon et al., 1998).


To be continued....