Understanding Heat Load

Transcription

1 Understanding Heat Load Implications for Slaughter Plants Kev F Sullivan BVSc Bell Veterinary Services/PAC Australia. BELL QLD 4408 bellvet@bigpond.com mob:

2 Outline for today Basics of heat load What does heat load look like? Risk management Developing management plans Effects on Abattoir

3 Losses Due To Excessive Heat Load 1977 Southern California 1991 Southern Queensland 1995 Nebraska & Iowa 1999, 2007 East Nebraska 2000 Southern New South Wales 2015 Nebraska USA dairy cows feedlot cattle - > 4000 feedlot cattle - > 5000 feedlot cattle feedlot cattle - Estimate >10,000 head

4 Proper Heat load management Optimised production Better animal well being Reduce mortality risk

5 Losses from excessive heat load Death loss Decrease in feed intake Acidosis rebound Follow on BRD

6 Damaged gut Loss of performance Loss of meat quality

7 Damage to gut epithelial cells from heat stressed rats (Lambert et al, 2002)

8 Pro-active management improves productivity Natural response reduce feed $10 -$30 per head

9 Event Warnings Daily Monitoring Mitigation Actions Heat Management Plan Preparedness Review

10 Understanding the Basics

11 Back to Basics Core body temperature C

12 Major source: Metabolic heat Major sink: Evaporation through panting Heat in Heat out Heat stored If heat generated by the animal is not balanced by the environment's ability to cool it, then heat will be stored by the animal This is called a heat load!!

13 Heat Balance Environment s capacity to cool Heat generated by animal

14 Heat Energy Balance Ambient Temperature Convection via air movement (forced or natural) Sweating (Minor cooling) Direct Solar radiation Panting (Major evaporative cooling) Internal Metabolic Heat Feed and Water Intake Conduction off ground (higher if lying down) Reflected Solar radiation

15 What is the Heat Load Index (HLI)? Weather information needed: Black Globe Temperature (BGT = Temperature + Radiation) Wind speed Relative Humidity BGT Wind HLI RH

16 HLI INDEX Is an Index Minimum 50 Maximum 130 when Hot, Humid and Calm Mostly, on its own does not indicate the likelihood of heat stress Must calculate the ACCUMULATED HEAT LOAD UNIT (AHLU)

17 HLI Threshold is the point at which heat is accumulated. Heat is dissipated when the HLI decreases below the lower threshold Lower threshold = 77

18 Heat load index Heat Loss Neutral Heat gain 77 < >86

19 What is AHLU? Measure of heat stored Calculated every hour HLI units above the HLI threshold HLI threshold = 86 Current HLI = 87 Heat is accumulation at 1 AHLU/hr

20 Relationship between HLI and HLI threshold 130 is Maximum Heat starts accumulating 50 is minimum

21 New tool: HLI Threshold Calculator Available on CHLT Basis for RAP Easy to use Should be used daily HLI Threshold of 86 = AHLU86 HLI Threshold of 95 = AHLU95

22 Relationship between HLI and heat dissipation Heat is lost Heat is lost at half the rate it accumulates

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24 PREDISPOSING FACTORS 1. ENVIRONMENTAL 2. CATTLE 3. NUTRITIONAL

25 Environmental Conditions Recent rainfall event High and persistent minimum and maximum ambient temperature High and persistent relative humidity

26 No cloud cover with high solar radiation levels Low or no air movement for an extended period (4-5 days) Sudden change to adverse climatic conditions

27 LETHAL COMBINATION Rain event Several days of - High temperature - High humidity - Low air movement

28 Cattle Effect Black, hairy, heavy, fat Bos Taurus Un-acclimatized Sick or compromised Recently handled

29 Factors to assess heat load risk Animal Environment Cattle genotype Coat colour Health Acclimatisation Days on feed Shade Pen conditions Water trough Temperature HLI threshold Weather Black globe temperature Wind speed Humidity HLI

30 Environmental Changes to HLI Temperature Change 2 o C Humidity Change 10% Wind speed Change 2 kph = 3 HLI points = 4 HLI points = 4 HLI points Wet and muddy conditions = Reduces threshold 4-6 points

31 AHLU Risk Matrix AHLU Cattle indicators Heat load indicator 0 No load Negligible 1-20 No load Panting score 1 Low risk Panting score 1-2 Medium risk Panting Score 2-4 High risk Over 100 Panting score 4 Extreme risk

32 Which is worse for heat load? Condition A 44 C Temp 25% RH 18kph Wind Sunny Condition B 29 C Temp 75% RH 0.72kph Wind Cloudy HLI = 100 HLI = 103

33 Types of heat events 1. INTENSITY EVENT Rapid onset (4-7 hours) HLI >100 AHLU not excessive (25-50 units) 2. ACCUMULATED EVENT cattle carry over heat AHLU ramps up over several days 3. REPEATED EVENT cattle exposed to many consecutive days AHLU >25 even when receive night time relief

34 Intensity event Cyclone Oswald (Jan 2013)

35 What happened? January 22, 23 and 24 Very hot and humid Heat load accumulated with little relief

36 January 25 and 26 Cyclone Very heavy rain Temperature decrease to 70 F for 2 days All heat dissipated Pens washed of all manure

37 January 27 Clear skies Very Hot- 104F o No wind High solar radiation High HLI 96 HLImax 91 AHLU 60

38 Should be OK? WRONG Losses commenced Jan 28 WHY???

39 Watch the cattle

40 What does heat load look like?

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42 Recognising heat load Look at the cattle Respiration rate and panting Cattle behaviour Feed intake Check high risk cattle Check at dawn, and every 2 hours

43 Respiratory rate and Panting score

44 Panting Score 0 Respiratory Rate <40 No panting, normal Hard to see chest movement

45 Panting score 1 Respiratory rate Slight pant, mouth closed, no drool or foam. See chest movement

46 Panting score 2 Respiratory rate Fast panting, drool and foam present No open mouth breathing

47 Panting score 2.5 Respiratory rate Like score 2, Occasional open mouth tongue not extended.

48 Panting score 3 Respiratory rate Open mouth and drooling. Neck extended and head usually up.

49 Panting score 3.5 Respiratory rate Like 3. Tongue out a bit and sometimes out. Excessive drooling

50 Panting score 4 Respiratory rate >160 Open mouth, tongue out for extended periods, excessive drooling Neck extended Head up

51 Panting score 4.5 Respiratory rate variable and may decrease Like 4, but head down, flank breathing, drooling may cease

52 Cattle Behaviour in EHL 1. Body alignment with solar radiation 2. Shade seeking 3. Increased time spent standing

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55 Cattle Behaviour in EHL 4. Reduced DMI 5. Crowding over water trough 6. Body splashing 7. Agitation and restlessness 8. Reduced or stopped rumination 9. Bunching to seek shade from other cattle

56 Cattle Behaviour in EHL cont 9. Open mouth and laboured breathing 10.Excess salivation 11. Ataxia/inability to move 12. Collapse, convulsions, coma 13. Physiological failure and death failing to cope

57 Different groups of cattle have different risk levels

58 HIGH RISK CATTLE Fat cattle New arrival cattle Hospital cattle Fescue cattle Ergot

59 HIGH RISK AREAS Reduced air flow areas Wet pens High stocked pens <118 ft 2 area, <16 ft 2 shade

60 HIGH RISK AREAS Dirty pens. No more than 2 inches of dry manure 2 inches of manure stores 5.5 inches of water and becomes 6 inches of wet manure. Restricted water supply less than 3 inches per head and slow refill

61 LOW RISK PENS Shade Adequate, reliable water Clean pens Sprinklers

62 High risk pens Reduced airflow Wet and dirty pens High stocking rates Restricted water supply Low risk pens Shade Adequate, reliable water Clean pens sprinklers

63 Weather stations minimum requirements Black Globe Temperature (BGT) or Solar radiation and free air/dry bulb temperature Wind speed Relative humidity or wet bulb temperature Logging interval no longer than 1 hour. ** Davis weather station** ~ $400

64 Reduced feed intake Reducing feed intake decreases metabolic heat production Reduction of 50% are not uncommon Rebound acidosis Irreparable damage to consumption

65 Dietary management 1. Reduce heat increments of production 2. Maintain dry matter intake 3. Maintain gastrointestinal motility 4. Manage cellular dehydration 5. Prevent/minimise tissue hypoxia and metabolic acidosis 6. Protect against antioxidant demand

66 When to change to heat load ration? hours before Hold until 48 hours after

67 Ration construction Increase inert roughage Increase fat and oil Reduce grain Increase vitamin, mineral and antioxidant Increase ionophore

68 Increase dietary potassium Increase potassium chloride diet KCl in water (risk of toxicity) Increase molasses

69 Manage feed allocation Reduce total feed availability Feed 85-90% of allocation prior to, during and hours after. Re-introduce at steady rate Facilitate rumen adaptation Prevent rebound acidosis

70 Cellular integrity Use of Betaine Start 7 days before to load up cells Feed over summer period Cost? 6-10 cents/hd/day

71 Water intake Water intake/ kg DMI V Temperature Water intake (litres) Temperature (C) Water Expon. (Water)

72 Water Intake/100kg LW/day SHADED UNSHADED FEEDLOT A FEEDLOT B * S.E. QLD (Unpublished data:rinehart)

73 Water At least two water troughs INCREASE to 3 cm/hd Portable water troughs 10 litres/ 50 kg live weight

74 Cool water C o Clean twice per week Underground pipes Troughs: Concrete Long and shallow

75 Shade 2.5 to 3 m 2 / hd at 3.00 pm 2.25 sqm/head Water trough not under shade Pen maintenance

76 Daily Monitoring 76

77 Things to monitor % finisher cattle panting score >2.5 at 6:00 am Feed intake change Pen floor moisture and manure levels Overnight hours AHLU at zero (Hours below 20 o C) Forecast AHLU for today Forecast AHLU for tomorrow Forecast AHLU for rest of week

78 Other things to consider Forecast today and for the next 3 days Hours of overnight cooling Hours Less than 20 C (> 6 hours) Wind speed (min of 10 kph)

79 Example intervention levels Monitoring Point Potential intervention level 1 Percent Panting score > 2.5 at 6:00 am >10% 2 Average feed intake change >10% decrease (yesterday actual to today call) 3 Mud depth >10 cm 4 Overnight hours AHLU at zero < 6 hours 5 Forecast Maximum AHLU today >50 6 Forecast Maximum AHLU tomorrow >50 7 Forecast Maximum AHLU rest of week >50

80 Status Example triggers Normal Normal behaviour Cattle shed all heat recent nights Forecast good Possible Forecast poor for 3-7 days time Likely Heat load behaviour ( shade seeking, water trough crowding) Feed decrease (>10%) Pant score >2.5 in >10% cattle Carry over heat. AHLU not zero for more than 6 hours Forecast hitting alert tomorrow (AHLUmax > alert Occurring Cattle behaviour consistent with heat load Feed decrease (>10%) Pant score >2.5 in >10% of cattle Carry over heat. Not shed heat for 48 hours (confirms heat load event) Enact high level mitigation or crisis action Forecast hitting alert levels today and tomorrow

81 Mitigation Possible Likely Occurring Work hours Work hours Cease all stock movements Daily monitoring Increase monitoring Troughs out (4 litres/hr) Dispatch times Dispatch schedule KCl in feed/water Shed work (8:00 am) Cease cattle movements Heat load ration Pen checking (9:am) Check priority pens only Bedding/pen wetting Water trough Water tubs in position Dead removal Ration Bedding, wetting pens Release cattle Heat ration/ KCl

82 SPRINKLERS Large droplets 150 micron 2 or 3 per pen Avoid water trough, shade, bunk m 2 /head own water supply 5-10 min on, off watch cattle and environment. Night better than day Humidity less than 20%

83 RECOVERY Cattle are fatigued Fix hydration Repair damaged gut Repair skeletal muscle

84 RECOVERY Muscle repair up to 7 days Gut repair about 48hrs Stay on heat load ration for this time Manage return intake to avoid rebound acidosis Serious gut inflammation severe and permanent

85 Effects on the Slaughter Plant No cattle delivery Big decision Animal welfare issue Death at feedlot Death in transit Death in Lairage

86 Effects at Slaughter Hoof separation Meat quality Dark cutters Reduced yield

87 On going effects. Reduced carcass quality for some time Effects of rebound acidosis Effects of knock on respiratory disease

88 Conclusion Heat load major issue Understanding heat load Development of management plans Management of events Effects on abattoir and meat quality