7. person of about 75 kg generates about as much heat as a 100-watt light bulb … A 550 kg CB / Buffalo is equivalent to about seven 100-watt light bulbs
8. For milking cows, add one 100-watt light bulb for every 5 litre of milk produced a day…
9. … The 550 kg CB / Buffalo producing 15litres per day is producing heat equivalent to ten 100-watt light bulbs!
12. Decrease in let down of milk production Reduced body condition due to less feed intake Significant drop in pregnancy rate High incidence of abortions Added all up … costly! How Heat Stress affects… Rumen acidosis and drop in milk production
16. Effect of Heat Stress on Ruminal pH of Holstein Crossbred Cows ( Mishra et al., JAS 30:1023) High Forage Diet High Concentrate Diet C O O L C O O L H O T H O T Ruminal pH
17. Significant drop in Reproductive performance Oestrogen level LH level Delayed response of Hormones
18. De Rensis and Scaramuzzi, 2003 Impact of Heat Stress on Infertility
19. And to top it all….. Summer stress increases Plasma Cortisol Level in Blood Hypothalamus HRF Ant Pituitary ACTH Adrenal Gland Increased Cortisol
20.
21. How to take care of Heat Sress? Ration Management Animal Rearing Management Control of Cortisol level through Anti stress, Adaptogenic
25. mimics SOD Maintains Plasma Cortisol Mode of Action Free Radicals S.O.D. Under stress free condition A.T.Ps. Energy Scavenged NATURAL REMEDIES Under stressful condition More energy More A.T.Ps. Extra Free Radicals (> normal) Plasma Cortisol ve feed back
26. EFFECT OF ON STRESS INDUCED ULCER Means, superscripted with different letters differ significantly R&D, NRPL, Bangalore - 0.3 ± 0.153 a Control + Stress + 400 1.5 ± 0.373 b Control + Stress - 0.3 ± 0.153 a Control % increase over control Mean Ulcer score Groups NATURAL REMEDIES
27. EFFECT OF ON PLASMA CORTICOSTERONE Means, superscripted with different letters differ significantly R&D, NRPL, Bangalore 6.172 46.62 ± 2.25 a Control + Stress + 41.198 62.00 ± 5.38 b Control + Stress - 43.91 ± 2.78 a Control % increase over control Mean Plasma corticosterone (mcg/dl) Groups NATURAL REMEDIES
THI=0.72 (W+D) +40.6 Where W – wet bulb temperature ºC D – dry bulb temperature ºC The principle of THI is that as the relative humidity at any temperature increases, it becomes progressively more difficult for the animal to cool itself. (RCI Technical Information. The influence of temperature humidity index on cow performance). THI values of 70 or less are considered comfortable, 75 – 78 stressful, values greater than 78 cause extreme stress. A Dairy Heat Stress Chart provided by Diamond V. This company manufactures yeast culture for inclusion in animal feeds. This lists 5 different zones of heat stress based on information from the University of Arizona. A key thing to point out is that the effect of heat stress at a specific temperature varies with relative humidity. As an example, there is no heat stress at a temperature of 83 F and 20% relative humidity. However, the animal is distressed at a temperature of 83 F and 90% relative humidity.
This chart breaks down the total cost of heat stress by animal type. These proportiins are: Dairy cattle = 52% of the total loss Beef cattle = 21% of the total loss Swine = 17% of the total loss Poultry = 10% of the total loss
One way cows dissipate heat is via panting and this increased respiration rate results in enhanced CO2 (carbon dioxide) being exhaled. In order to be an effective blood pH buffering system, the body needs to maintain a 20:1 HCO3 - (bicarbonate) to CO2 ratio. Due to the hyperventilation induced decrease in blood CO2, the kidney secretes HCO3 - to maintain this ratio. This reduces the amount of HCO3 - that can be used (via saliva) to buffer and maintain a healthy rumen pH. In addition, panting cows drool and drooling reduces the quantity of saliva that would have normally been deposited in the rumen. Furthermore, due to reduced feed intake, heat-stressed cows ruminate less and therefore generate less saliva. The reductions in the amount of saliva produced and salivary HCO3 - content and the decreased amount of saliva entering the rumen make the heat stressed cow much more susceptible to sub-clinical and acute rumen acidosis
pH measured 12 times in 8 hours after feeding. Cows fed the high forage diet had higher pHs than those on the high concentrate diet, as expected. When cows were exposed to increased temp and humidity, ruminal pH became more acidic, 0.4 ° for cows fed the high forage diet and 0.6 ° for cows fed the high concentrate diet. The drop was greater for cows fed the high concentrate diet. Why is that?
There are a number of things that can be done to alter the ration being fed. The goal is to increase energy intake while maintaining cow health. Selecting higher quality forages and feeds help because they release less heat within the animal while being digested. Added fat can help since it is a highly concentrated energy source. It has a high efficiency of use and doesn’t increase heat load within the animal very much during digestion
Adding these types of by-product feeds provides energy that can be used by the rumen microorganisms as a source of energy. However, they have low starch levels and do not contribute to a low (acidic) pH rumen environment. If protein is provide in excess of requirements, it is excreted from the body. To do this requires the use of energy. Using energy to excrete protein decreases he energy available for milk production. Buffers can assist in maintaining a normal rumen environment. Yeast can help improve the efficiency of feed digestion in the rumen. Added minerals (sodium, potassium) that are lost by increased respiration rates
There are a number of changes that can be made in feeding management (the way the ration is fed). These include: Fresh, palatable feed encourages more feed intake by the animal Uniformity and consistency of the ration daily assists in improving the efficiency of feed use Sorting gives the animal an opportunity to alter the ration and decrease the efficiency of nutrient use Providing fresh feed at the cooler times of the day can stimulate feed intake. The feed will also stay fresher when fed at this time.
There are a number of facility adjustments that can be made: Minimize overcrowding - Overcrowding decreases the ability of animals to dissipate heat. The holding area (the area where cow wait before entering the milking parlor) on many farms is poorly ventilated. It is often also small and overcrowded. Can air flow be increased with fans? A goal is an air flow of 4-5 miles/hour. Sprinklers or misters can be place above the cows to wet the skin (but not soak the cow). If air movement is adequate, then the water is evaporated and removes heat from the cow.
Radiant energy from the sun can be a major contributing factor to heat stress. Darker coated animals tend to absorb more radiant heat and will be more affected by heat stress.