Managing Heat Stress in Dairy Animals Prof. Dr. Muhammad Abdullah

1. Managing Heat Stress in Dairy Animals Prof. Dr. Muhammad Abdullah Department of Livestock Production University of Veterinary and Animal Sciences Lahore Cell # +92-300-6648200 E-mail: mabdullah@uvas.edu.pk

2. Farm Income Animal Productivity

3. Animal Productivity Genetics X Environment

4. Environment • Optimum Productivity is Function of COW COMFORT

5. COW COMFORT • Physical • Nutritional • Social • Thermal

6. Thermal Discomfort • Not a problem of the animal BUT • A problem of the farmer

8. Buffaloes Sitting in sunlight free choice during hot sunny day

10. Bos taurus vs. Bos Indicus

11. Genetic Control of Heat Stress • “SLICK” is the major thermoregulatory gene found so far in Bostaurus to combat heat • The mechanism of increased heat tolerance is due to convective and conductive heat loss due to slick gene • There is a need to test for Slick gene in Bosindicus

12. Bos indicus • Short reflecting Hair coat • Body mass vs. Skin surface • No. of sweat glands • Functional sweat glands • Low metabolic rate • Low production • Less feed intake and slow passage rate

13. Bos bubalus bubalis

14. Homeothermy • Cattle and Buffaloes are homeotherms • Maintain their deep body temperature essentially constant • Make compensating physiological and behavioral adjustments

15. Animal Environment • Few places in the world where natural climate continuously remains optimum for animals. • Components of the surroundings impose serious limitations on the animal’s productivity.

16. Major Climatic Components • Air temperature, • Humidity, • Solar radiation, • Wind velocity and • Precipitation produce a combined effect on the ‘thermal comfort’ of the animals and their performance.

17. Air Temperature • Most important climatic element in thermal comfort • Immediate surroundings influence the heat exchanged • Four modes of heat transfer, viz., conduction, convection, radiation and evaporation.

18. Humidity • The water vapor content affects the capacity for heat loss. • The rate of cooling by evaporation from the respiratory tract and the skin depends on the water vapor content of the air (humidity).

19. when the atmospheric temperature equals or exceeds the animal’s body temperature, evaporation is the only available means of heat loss. • From 21C for Bostaurus cattle and 27C for Zebu cattle, humidity exceeding 60 % becomes a problem affecting their production

20. In A well Ventilated Shed Shed temperature Animal Body Temperature

21. Thermoneutral Zone Heat Gain = Heat Loss • Temperatures conducive to normal function • The upper critical temperature is the point where the effects of heat stress start to appear

23. Sources of Heat • Environmental Temperature • Metabolic Heat • Heat of radiation (direct/Indirect)

24. The Cow’s Furnace

25. Mechanisms of heat exchange • Conduction: Heat moves from warmer to cooler surface through direct contact. • Convection: The layer of air next to the skin is replaced with cooler air. • Radiation: Heat can radiate from a warmer environment to a cooler environment. • Evaporation: Moisture evaporates from the skin (sweating) and lungs (panting).

26. CONDUCTION

27. How do cows exchange heat with the environment?

28. Temperature Humidity Index (THI) • Includes both temperature and humidity in determining the point at which heat stress may occur • A THI > 72 is considered to indicate heat stress in dairy cattle • THI = 15 + 0.4 (Td + Tw)

29. Example of the Interaction of Temperature and Humidity in Determining Heat Stress Potential in Dairy Cattle

30. All of These = THI of 72

31. Heat Stress • The point at which a dairy cow (or other animals) cannot dissipate an adequate quantity of heat to maintain body thermal balance or normal body temperature (Heat Gain ≠ Heat Loss)

32. Signs of Heat Stress • body temperatures rises > 102.6 ◦F • Panting>80 breaths per minutes • Reduced activity • Increased water intake • Seek shade • Reduced feed intake (>10-15%) • Reduced milk yield (10 to 20% or more) (Larry E. Chase NY )

33. Effect on Dry Matter Intake KG/Day THI 50-55 THI 65-70 THI 75-80

34. Effect on DMI • Feed intake of lactating Jersey. Brown-Swiss and Holstein depressed at 27C while that of Zebu (Brahman) cows did not decline until 38C. • May be short or long-term

35. Changes in the metabolism • Energy requirements for maintenance increase - Increased respiration rate -More blood flow to the skin - Less blood flow to body core - May increase by 20-30%

36. Effect on Milk Production • Decreases due to: • More energy for maintenance • Lower dry matter intake - Can drop 10 to > 25% • Among Bos Taurus breeds, milk yield starts declining at 21C in Holstein Friesians and in Jersey and Brown Swiss at 24 to 27C. • Milk yield of zebu declines above 32-34C.

37. Effect on Reproduction • Estrus intensity and length decreased • Conception (fertility) rate decreases almost up to 15% • Decreased growth, size and development of ovarian follicle • Increase early embryonic death • May affect fetal growth and calf size

38. Factors Which Determine Severity Of Heat Stress • Actual temperature and humidity • Length of the heat stress period • Degree of cooling that occurs at night • Ventilation and air flow • Cow factors (size, milk production) • Housing type , ventilation • Breed • Water availability • Hair coat colour and depth

39. Heat Stress in Buffalo • Buffaloes exhibit signs of great distress when exposed to direct solar radiation during hot weather • Buffalo bodies absorb a great deal of solar radiation because of their dark skin and sparse coat or hair • In addition buffalo possess a less efficient evaporative cooling system due to their poor sweating ability

40. Approaches to Minimize the Effects of Heat Stress • Two basic approaches - a. Housing and facility management b. Feeding management

41. Sprinklers Wallowing Pond

42. Housing and Facility Adjustments • Minimize overcrowding • Restrict movement • Minimize time in the holding area • Provide shade to the animals 1. Natural 2. Artificial a. Portable b. Permanent

45. SHED 15F

46. Ventilation Maintain air flow rate 8-10 km/h with fans. Forced Ventilation

47. Evaporative cooling • Sprinklers to wet the cow’s skin? • Wallowing ponds for buffaloes

50. Wallowing Pond