Stress nutrition (thermal)


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Stress nutrition (thermal)

  2. 2. What is stress? • Any deviation from the optimum state could be referred as stress. • There are several factors which lead to varieties of stress, affecting the welfare of the animals
  3. 3. Thermal Stress • One of the major environmental stresses. • Livestock face stress both during summer and winter when environmental temperature deviates the thermo neutral zone. • However, being endotherms, regulates the body temperature close set point by controlling either heat production or heat loss. • But the extreme hot or cold weather gets the animal into stress – when the temperature exceeds the upper or lower critical temperature of the animal.
  4. 4. In order to reduce the thermal stress • Animal changes behavior and metabolic reactions – quite natural on the part of animal • But the livestock owner must follow primary managemental strategies – for making the micro climatic animal friendly environment • Nutritional strategies – However, plays secondary role to primary managemental strategies
  5. 5. • When the environmental temperature goes beyond the critical temperature, – Physical regulation plays in role to maintain the body temperature of animals within in its normal range. • When physical regulation proves insufficient, the chemical regulation comes into play, which is important means for combating the effects of low environmental temperature.
  6. 6. Temperature- Humidity Index • A tool to measure level of heat stress • It is a single value representing the combined effects of air temperature and humidity associated with the level of thermal stress. THI = 0.72 (W+D) +40.6 Where W = Wet bulb temperature oC and D= Dry bulb temperature oC
  7. 7. • 70 or less -- are considered comfortable • 75-78 -- stressful • >78 -- extreme distress (unable to maintain thermo regulatory mechanisms or normal body temperatures) • The bovine thermal comfort zone is -13ºC - +25ºC. • Within this temperature range, the animal comfort is optimal, with a body temperature between 38.4ºC and 39.1ºC. THI values
  8. 8. Biological effects of thermal stress 1. Reduces feed intake accompanied by – reduced rumination and – nutrient absorption and – increased maintenance requirements which results into decrease in nutrient availability for production purposes • Reason : Peripheral vasodilatation, concomitantly reduced blood flow to organ systems such as reproductive tract and GIT
  9. 9. 2. Alters endocrine status of animal – increase in blood concentrations of • prolactin, ADH, aldosterone in non-ruminants, and • catecholamines and glucocorticoids in cattle. – Among all of them, glucocorticoids content in blood considered to be a good index for reactions of animals to any environmental challenges
  10. 10. 3. Amino acid turn over gets lowered while bone resorption /alkalosis occurs which is indicated by higher alkaline phosphatase activity (Bahga et al., 2009). 4. Reduction in growth rate in growing calves which may be due to lower energy generation and impaired metabolism (Bahga et al., 2009)
  11. 11. 5. Ruminal Acidosis Heat stress (To dissipate excess heat) Increased respiration rate Panting Enhanced CO2 exhalation Hyperventilation (reduced blood HCO3 - ) Normal HCO3 - : CO2 is 20:1 Increases drooling of saliva Reduces the quantity of saliva that would have normally been deposited in the rumen Reductions in saliva entering into rumen and its HCO3 - Rumen acidosis
  12. 12. 6. Nutrient requirement Energy: • When the temperature of peripheral tissues increases more than the rectal temperature (during thermal stress), • The maintenance energy requirement becomes higher. • It may increases by 7% per every oC increase in mean body temperature (Grahm et al., 1959).
  13. 13. Minerals • Because of reduction of voluntary feed intake during thermal stress – It is logical that mineral intake may also be reduced than the optimum requirement. • It was noted that a 5 fold increase in K loss from skin was measured during peak thermal stress. • Further, the marked losses of Na, Mg, Ca and Cl, but not P are also correlated with sweating rate.
  14. 14. Vitamins: • Thermal stress also affects the store of Vit A in the liver and • Increase the requirement of Vit C – due to their increase in rate of excretion through the urine and sweat.
  15. 15. Nutritional strategies to ameliorate thermal stress 1. Provision of balanced feed 2. Feeding Regimen 3. Provision of clean ad libitum drinking water 4. Increasing nutrient density 5. Management of DMI 6. Protein 7. Fats 8. Minerals 9. Feed additives 1.Buffer 2. Niacin 3. Anti oxidants 4. Fungal culture:
  16. 16. Provision of balanced feed • To compensate the reduced DMI – there is an urgent need to increase in nutrient density – side by side one must have to go for recalculation of mineral and water requirements – due to increased loss of potassium through sweat during hot and humid environment (Collier et al., 2005). • Cold stress proved to be less severe compared to summer because of the consumption of large amounts of feed to generate sufficient body heat with the utilization of feed • Hence adoptability to cold weather well developed in moist domestic animals, – provided adequate feed, and minerals and vitamin supplements are made available
  17. 17. Feeding Regimen • Feeding behavior of most of the animals changes during summers • They tend to consume more feed during cooler periods of the day i.e. evening hours (West, 1999). • Thus, feeding animals at more frequent intervals and during the cooler periods of day – Not only encourage them to maintain their normal feed intake but will also keep feed more fresh and thus, stimulate DMI.
  18. 18. • In very hot weathers, more frequent feeding – Decrease the diurnal fluctuations in metabolites and increase the feed utilization efficiency in the rumen (Robinson 1989). • At least 70% of the daily feed should be given fresh at night. • Further, feeding of animals in the later part of the day could prevent the co-occurrence of peak metabolic and environmental heat load
  19. 19. Provision of clean ad libitum drinking water • The very first step to reduce heat stress is to provision of cool water – (Especially for all lactating and dry cows plus heifers as water is the primary nutrient needed for milk production, accounting for over 85 percent of the milk content) • Water requirement increases significantly as the environmental temperature rises. – Cows may drink up to 50% more water when the THI is >80%. • It indicates the importance of water and its cleanliness during the summer months. – Thus, keeping water tanks clear of feed debris and algae is a simple and cheap strategy to help cows remain cool.
  20. 20. Increasing nutrient density • Energy cost of – eating, – rumination, – heat of fermentation, – work of digestion and there after the – work of nutrient metabolism Are the fractions which contributes to the heat increment of feeding (Webster, 1978). • Thus, if animals suffering from heat stress is maintained on poor quality roughages, there will be added stress of heat increment of feeding. • Therefore, nutritionally balanced and easily digestible feeds supplemented with protected fat and limiting amino acids may reduce such additional stress of increased heat increment of feeding.
  21. 21. Management of DMI • High fibrous diet will lead to higher proportion of acetate, which is having more heat of nutrient metabolism as compared to propionate (Linn, 1997). • Thus, it appears logical that feeding low roughage and high concentrate diet to the ruminants during summer periods to reduces the heat production inside body. • Pennington et al., 2004 -- Ruminant diets with grain and low in fiber cause less heat stress for lactating cows because of their lower heat of digestion. • However, a minimum quantity of good quality roughage should be fed to prevent acidosis condition
  22. 22. Protein • Protein content with highly degradable materials apparently stresses the cows further, causing an additional heat load, – because the excess of nitrogen supplied by protein must be detoxified to urea in liver for excretion through a metabolic pathway, which is very high in energy demands (1g urea = 7.3 Kcal). • The higher level of protein and degradability in the diet of ruminants may lead to reduction in feed intake, which results into reduced milk production (Higginbotham et al., 1989). • Feeding Low level of less degradable protein is advisable for encouraging the animal for DMI.
  23. 23. Contd., • Hence, both the quantity and form of protein in the diet are needed to be considered when feeding heat stressed cows (Linn, 1997). • Keeping all point in view, it can be recommended that – The level of CP in the diet should not exceed 18% – while the level of RDP should not exceed 61% of CP (Huber et al. 1994).
  24. 24. Fats • As compared to other feeds, fats have a low heat increment – Hence, high-fat diets have high energy conversion efficiency, could be beneficial during hot weather • However, research on the effects of dietary fat during hot weather gives inconsistent results. • Knapp and Grummer, 1991 -- Supplemental fat at 5% of diet DM enhances lactation performance under thermo-neutral and heat stress conditions.
  25. 25. Contd., • Chan et al. 1997 -- In a study, 3% prilled fatty acids (inert) supplementation was compared with shade plus evaporative cooling to relieve heat stress in dairy cows. – Results revealed that milk yield improved only by the cooling not the fat treatment, supplementation. • Although the results seem contradictory, but biological principles argue in favour of fat supplementation under conditions of heat stress. • Nutritionists still suggest fat supplements to give a final fat content of 6 - 7 % of diet DM, especially for high-producing cows.
  26. 26. Minerals • HS associated with changes in mineral metabolism, especially electrolytes (Na & K) • Since these electrolytes associated with maintenance of water balance, ion balance and the acid-base status of heat- stressed cows • Need to be supplemented more than recommended levels • Sanchez et al. 1994 – – Na conc in the diet from the NRC recommended level of 0.18% to 0.45% or more improved milk yield by 7 - 18% & – dietary conc of K to 1.2% or more results in a 3 - 9% increase in milk yield
  27. 27. Contd., • For heat-stressed cows, alkaline diets are more preferable – Thus, NaHCO3 and MgO have proven very effective in alleviating to some extent the drop in milk fat associated with heat stress conditions (West et al. 1992). • NaHCO3 will also increases ruminal pH, thereby establishing a more favorable environment for fiber digestion (Santra et al., 2003). • Escobosa et al., 1984 -- A diet with high chloride content depress the DMI and was associated with low blood pH and reduced blood buffering. – Researchers recommend that the level of dietary chloride should not exceed 0.35% of DM (Sanchez et al., 1994).
  28. 28. • Supplementation of some trace minerals viz., • Chromium in its organic form i.e – chromium yeast and chromium picolinate in poultry and – chromyl pyridine carboxylate in dairy cows
  29. 29. Feed additives Buffer • Na-bicarbonate Niacin • Well-known subcutaneous vasodilator in many sp. and could be effective for reducing body temperature. • Unprotected niacin may be degraded in the rumen. • Niacin helps to alleviate heat stress both by increasing evaporative heat loss from the body and also by reducing the effects of heat at the cell level (Lundquist, 2008).
  30. 30. Anti oxidants • HS generates disequilibrium of the oxidative balance, with important consequences over the vital function, life and death of the affected cells • Supplementation of antioxidants (Se, Vit E, Zn or Cu etc) during thermal stress enhance the action of both enzymatic and non-enzymatic antioxidants, thus nullify the undesired side effects of free radicals
  31. 31. • Shivakumar et al., 2010 - Supplementation of vitamin C and vitamin E have a negative effect on cortisol levels during heat stress, which relieve the severity of heat stress in goats • However, reduction in cortisol levels by vitamin E and C is not yet fully understood
  32. 32. Fungal culture • Improving rumen pH: reduces acidosis risk • Improved fiber digestion and nitrogen utilization: increased feed efficacy • Rumen microflora stabilization
  33. 33. Reference 1. Choubey M and Kumar A. (2012). A nutritional interventions to combat heat stress in dairy animal. Vetscan. 7(1): 19-26. 2. Short course on “Nutritional and dietetics under clinic therapeutic conditions of pet and farm animals”. IVRI, 2001. 3. Sunil Kumar B.V Kumar A and Meena K. (2011). Effect of heat stress in tropical livestock and different strategies for its amelioration. Journal of stress physiology & biochemistry. 7(1): 45-54.