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Climatic sensitivity of dairy cattle to heat-waves or extreme weather

Climatic sensitivity of dairy cattle to heat-waves or extreme weather. Peter Løvendahl Ahmed Ismael Sayed Ismael Dept. Molecular Biology and Genetics. AARHUS UNIVERSITY. Nice cow-weather ?. Better cow-weather ?. Cow-holiday weather ?. Wrong weather or Wrong cow ?.

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Climatic sensitivity of dairy cattle to heat-waves or extreme weather

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  1. Climatic sensitivity of dairy cattle to heat-waves or extreme weather Peter Løvendahl Ahmed Ismael Sayed Ismael Dept. Molecular Biology and Genetics AARHUS UNIVERSITY

  2. Nice cow-weather ?

  3. Better cow-weather?

  4. Cow-holiday weather ?

  5. Wrong weather orWrong cow ?

  6. How are cows coping with climatic conditions ? • Thermoregulation in animals  cows • Thermal Comfort and heat stress • Traits affected by heat stress • Interactions between heat stress and genetics • Modelling environmental effects • NordGen project on environment and genetics • Do we need climate tolerant cows ?

  7. Thermal comfort zones

  8. Environment Radiation Conduction Convection Environment Radiation Conduction Convection Evaporation Heat gain Animal Heat loss Metabolism Maintenance Exercise Growth Lactation Gestation Feeding Metabolism Milk removal Fecal Elimination Urinary elimination Thermoregulation

  9. Components of thermoregulation • Conduction: qcd = Ahcd(ts – ta) • Convection: qcv = hAcvVn(ts– ta) • Radiation: qr = δA1FAFE(t14 – t24) • Evaporation:qe = keAeVn(ps – pa)

  10. Joint effects of temperature and humidity – thermal heat index -THI “how the temperature feels – with increasing humidity” • THIC = 1.98tC + 1.089(0.01RH% -1)(tC – 14.44) – 14.152

  11. THI-charts with heat stress warnings • Developed in southern US states

  12. Chill factor – the mirror imageWind velocity adjusted temperature TWCC = 13.13 + 0.6215tC – 13.95Vms0.16 + 0.4863tCVms0.16

  13. Physical climate modifiers • Ventilation • Insulation • Heating • Cool spray: evaporation

  14. Lines selected for high (H, n=24) or low(L, n=24) cold resistance (from Slee et al., 1987). Cold-stress in lambs Lambs from two selection lines were gently cooled in a water-bath. The aim was to find lambs able at coping with harsh winter conditions in Scotland (Slee et al. 1987)

  15. Heat stress effects with GxE Responses to heat stress in Friesian, F1 and Brahman heifers, compared with performance at lower ambient temperature (from Colditz & Kellaway, 1972). NOTE: Little or no change in body temperature in Brahman Largest increase in Holsteins: Respiration rate, Water intake, Evaporative water loss

  16. Heat stress affects milk yield in Egypt • Seasonal effects align with hot climate.. Gafaar et al 2011

  17. Heat stress affects fertility • Non-return rate in cattle • Reaction norm model Variance due to heat stress

  18. Sensitivity of fertility (NR90) to heat stress may increase with milk production • Heritability for NR90 was lowest between 18 and 24°C, and increased with higher temp. • Heritability of heat stress “as a trait” became as high as that of the trait itself with higher temperature • The genetic relationship between heat tolerance for milk yield and heat tolerance for NR90 is weak • Differences in estimates for NR90 between univariateand bivariate analyses indicate bias caused by strong selection for milk yield Ravagnolo and Mistzal, 2002, JDS 85:3092

  19. So – is this interesting to Nordic climatic conditions ? • Forecast: warmer summers • Forecast: colder winters • Also, cows may become more sensitive to climate!

  20. NordGen GxE project • Subproject – PhD study - in AnGR- NordicNET • Joint AU-SLU project • Aim: To assess genotype-by-environment (GxE) interactions on fertility, longevity and milk production using reaction norm methods over gradients of geographical location, intensity of feeding and management and breed of cow (‘adaptation potential on the phenotypic level).

  21. Nordic dairy cattle breeding No dedicated strains for production systems or regions. Compromise approach for all available breeds. Traits: production, health and fertility. Unclear if the compromise satisfies extreme ends of the environmental gradients from climate. Clarification involves estimation GxE effects on production traits and fertility.

  22. Fertility trait recording • Conventional recording of almost all cows using AI data • Low heritability of conventional female fertility traits, h2 = 0.03 • Large variation bias from management decisions • Automated recording of fertility traits becoming popular – along with automated milking • Moderate heritability for automated fertility traits, h2 = 0.18 • Collection of automated data – becoming a routine ....

  23. Activity monitoring • Electronic “tags” on neck or leg • Recording at 1 or 2 hour intervals • Useful for cows and heifers • Data from AMS herds in SE and DK

  24. Methods • Cohort studies – many cows • Environmental – climate – data from weather stations using “grid-values” • Genetic ancestry – traditional database • Genetic ancestry – genomic relationship • Modelling reaction norms as GxE effect • Holstein, Jersey and Red cattle .... This has just started ....

  25. Summing up • More extreme weather is expected, including warm humid summers • Fertility of dairy cows is probably affected from heat stress even in Nordic climates • Selection for higher yield may increase sensitivity to heat stress • Clarification of climatic impact on dairy cow fertility in recently started project

  26. Fit for a changing climate ?

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