Different Multi-Stressors Impacting Livestock and Production Systems
Dr.A.K.Wankar*, Dr.S.N.Rindhe1, Dr.P.M.Kekan2, Dr.B.L.Kumawat3
Assistant Professor, Veterinary Physiology, College of Veterinary & Animal Sciences [MAFSU], Parbhnai
Assistant Professor, Livestock Product Technology, College of Veterinary & Animal Sciences [MAFSU], Parbhnai
Professor, Veterinary Physiology, College of Veterinary & Animal Sciences [MAFSU], Parbhnai
Assistant Professor/Subject Matter Specialist, Gynaecology, College of Veterinary & Animal Sciences [MAFSU], Parbhnai
https://www.pashudhanpraharee.com/impacts-of-climate-change-on-dairy-cattle/
With the growing human population, the animal husbandry sector is facing tremendous challenge to supply. The animal origin products are used by humans form times immortal for their superior quality, nutrition and protein as compared to plant based products. With the recent technology, intensification and breed improvement we are able to upscale the production substantially. Although, the production has increased there are other factors like land, natural resources, feed and lastly the climate change which modulate the agri-animal husbandry both directly and indirectly. Animals reared under both intensive and extensive conditions are constantly subject to multitude of biotic or abiotic stressors. Stress can be defines as voluntarily or involuntarily non-specific change to maintain a constant internal environment or homeostasis (Selye, 1973).
Livestock are very well adapted to any single natural or artificial stressor. When acclimating to a single stressor, the animal response depends on body condition, duration and intensity of the stressor. It had been reported that, when exposed to a single stressor, there is not significant divergence of stored energy reserves and hence growth, reproduction and production are not severely compromised. On the contrary when exposed to multiple stressors animals body stores are not sufficient to cope up with it and metabolism alters and biological functions are disturbed (Gebregeziabhear & Ameha, 2015). If given enough time the animals attain gradual acclimatization to multiple stressors, but at the cost of growth, hampering production and reproduction. Even the native livestock species are not evolved to cope up with two or multiple stressors simultaneously. Persistent stressors also compromise the immune functions of animals, making them susceptible to pathogens, parasites and diseases.
Below are some common physical and psychological stressors adversely affecting the growth and productive functions in livestock,
- Thermal/Heat Stress
- Cold Stress
- Feed Deprivation/restriction
- Maternal Separation and Weaning
- Transportation Stress and Handling
- Social Isolation and Mixing
- Restraint Stress
- Effect of Novelty
Thermal Stress
Animals living in tropical and subtropical regions are subjected to high environmental summer temperatures for a predominant part of the year, which predisposed them to heat stress. High temperatures and humidity increase the Temperature Humidity Index (THI) and furthers predisposes the livestock to heat stress. Although the native animals are well adapted to these meteorological variables, like high temperatures, humidity, lack of adequate wind, combination of stressors challenges the thermoregulatory mechanism persistently. Gradually, the heat dissipation mechanisms are compromised and animals start gathering excess heat, culminating into heat stress. In recent years, due to global warming even America and Europe have been witnessing high ambient temperatures for prolonged periods, sudden heat waves and solar flares. Most of the livestock breeds here are adapted to optimum or cold environmental conditions and are very easily subjected to heat stress, affecting the production drastically.
Heat stressed animals divert body reserves and energy for thermoregulation or cooling off. There is reduction in feed intake, rumination and locomotion with concurrent increase in water consumption. Also the digestive functions alter and absorption and assimilation of nutrients is hampered during severe heat stress. Other metabolic adaptations include rewiring of energy and protein metabolism, enzymes, endocrine system and molecular chaperons like heat shock proteins (HSP’s). As less energy is available for other basal functions, both prenatal and postnatal growth is retarded, puberty is delayed. Adult animals have poor performance and reproduction and production decreases significantly. Gonadal functions are also depressed in heat stressed animals and males have poor quality and abnormal spermatozoa’s, while females display poor estrus expression, stunted foetal growth, and early embryonic mortality. Offspring’s born during summer stress have poor growth performance and attain puberty and maturity, considerably later than animals born under optimum environmental conditions. Although, the animals adapt to these extreme environmental conditions, their performance remains poor, resulting into economic losses and even mortality.
Cold Stress
Most of the domestic livestock are very well adapted to cold conditions, which is an evolutionary trait. Especially, the animals living in northern hemisphere are more comfortable to cold climate as compared to their southern counterparts. Hair, wool, hides and fat depots are the used by animals to counter cold stress. But in lack of cold acclimated animals, cold stress might result in some drastic thermoregulatory adaptations. Animals under moderate cold stress, increase their feed consumption, to meet the energy demands. During severe stress, shivering mechanism is activated and there might be voluntary and involuntary shivering for extended periods. Chronic cold stress, decreases the overall metabolism, gradually shutting down the enzymatic machinery and animal might die of exhaustion and lack of energy. Similarly, pregnant females might spontaneously abort or the foetal growth is not adequate.
Feed Deprivation/restriction
Lack of adequate nutrients (macro/micro nutrients) is another important and common stress faced by livestock. This nutritional stress is predominantly seen in developing nations, where mostly the extensive animal husbandry is prevalent. Environmental conditions like intense heat, droughts, floods etc. not only directly affect the fodder production but also affect their nutritional quality. Also these variables affect animal welfare, voluntary feed intake, digestibility and assimilation of nutrients. Both acute and chronic nutritional stress is deter-mental for animal growth, performance and production. Young growing animals, pregnant females and lactating females, which have high energy or metabolic turnover rates are more susceptible to nutritional stress. Longer the duration of stress or food deprivation, more severe is the impact.
Slow growth rates and late puberty are very common in livestock, suffering from chronic energy and protein malnutrition. In pregnant animals nutritional stress affects the foetal growth adversely and also leads to different complications during the dry period, post pregnancy. Both males and females have sub-optimal reproductive performance, when subjected to nutritional stress. Beef cattle and poultry show stunted growth and also the meat quality is affected. In lactating animals the milk production decrease significantly, with alteration in normal milk components, especially fat and protein content.
Food deprivation also leads to drastic changes in gut micro-biota, in ruminants. Alteration of fermentation pathways, causes different metabolic disturbances and there is production of unwanted metabolic end products, gradually subjecting the animals into negative energy balance (NEBAL). NEBAL, negatively affects animal’s normal metabolic functions, the immune system, the productive functions and predisposes them to an array of diseases, pathogens and other stressors like heat stress or transportation stress or weaning stress etc. The poor production performance and the economic losses in the tropics and sub-tropical regions, where the livestock are mainly free ranged or extensively reared can be mainly attributed to nutritional stress, management and environmental conditions.
Maternal Separation and Weaning (young animals)
Modern day animal husbandry practices, demand early weaning of the offspring’s. This is essential to obtain early reproductive activity of the females. Therefore the offspring’s are quickly separated from their mother, which can lead to physiological and psychological stress. The stress can be of short or long duration, and abrupt weaning is always more stressful for young animals. Weaning not only disrupts the maternal-offspring bond, but also alters the feeding habits and leads to sudden dietary changes, which is stressful for both non ruminant and species, alike.
Young one respond by change in behaviour and also their metabolism, leading to increased secretion of cortisol, to alleviate the weaning stress. Other symptoms include temporary anorexia, social isolation and increased vocalization. All these symptoms, gradually disappear after 1-2 week, but sometimes might persist for longer duration (depending on species) and this chronic stress might change animal behaviour, permanently. Separation from mother and rough handling by humans during the weaning phase is also a major reason for stress and once the human involvement is removed the young animals, gradually get acclimated, both physiologically, nutritionally and emotionally to the new conditions.
Transportation Stress and Handling
As an essential farming operation is, animals need to be transported to market. In recent years, the national and international trade, has subjected the live animal’s (small as well as large ruminants and poultry) to significant transportation stress. Transportation duration and environmental conditions determine the severity of the stress. Stocking density, short journeys (> 1-2 hrs) with breaks, in ambient environmental conditions put minimum stress on the animals. But overcrowding the animals for long distance journeys, without breaks in adverse climatic conditions subjects the animals to severe acute and chronic stress. Animals respond to stress by making several physiological, biochemical and endocrinal changes. These changes lead to depletion of body energy stores, and also affects the welfare and meat quality of the beef animals. Dairy cattle might take 2-3 weeks to recover from transportation stress to attain original production potential. Transportation also, increases the susceptibility of animals to different zoonotic diseases, which is nowadays a major concern for humans.
Long stressful journeys leads to severe stress response and lowers animal’s immune system, predisposing them to different pathogens. Also, drastic behavioural responses are established in livestock during and after transportation. In-human or in appropriate animal -human interaction before, during and after transportation is one of the leading cause of stress, evoking series of physiological, behavioural and metabolic responses in animals. It is essential to carefully plan the journey, duration, handling the animals gently and minimally and keeping track of animals nutritional and water requirements, to reduce the transportation stress (immediately before, during and after transport).
Animals are usually good at adapting to a single stressor at a time (acclimation), but when subjected to multiple stressors simultaneously the process of acclimatization is slow and difficult (Sejian et al., 2016). It’s like fighting a battle on multiple fronts, making it difficult to win. The problem is more pronounced in tropical and subtropical regions, where already the climate is extreme, subjecting the animals to heat stress. It becomes pertinent to facilitate good managemental regimes, environmentally sound shelter and provide proper nutrition to our animals, so that they have the necessary energy to maintain production at desired levels, making animal husbandry sustainable and profitable in global warming and climate change scenario.
References
Selye, H. (1973). The evolution of the stress concept. Animal Science, 61, 692–699.
Gebregeziabhear, E. & Ameha, N. (2015).The Effect of Stress on Productivity of Animals: A Review. Journal of Biology, Agriculture and Healthcare. 5(3): 2224-3208.
Sejian, V, Gaughan J.B., Bhatta, R., Naqvi, S.M.K. (2016). Impact of climate change on livestock productivity. Feedipedia. 2016. http://www.feedipedia.org/sites/default/files/public/BH_026climate_change_livestock.pdf
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6951910/
