Training Course Livestock and Climate Change 12 th -14 th January 2015, Dakar Heat stress in ruminant production : Effects of heat stress, how to alleviate Michel Doreau & Emmanuel Tillard INRA & CIRAD, France
DAIRY OR MEAT POTENTIAL genetics farmer climate management feeding farmer MILK OR MEAT PRODUCTION
Is the lower production inevitable in areas with climatic stress? Forage yield and quality Animal physiology Consequences on milk yield Choice of a breed, a way to alleviate
Fiber % in dry matter 50 Temperature and forage quality Tropical grass Temperate grass C4 metabolism C3 metabolism undigestible 25 undigestible digestible digestible 0 Day Night 18 25 32 10 17 24 18 25 32 10 17 24 Temperature, C (controlled)
Proper effect of forage quality on feed intake Forage fiber Rumen fill Proportion of requirements covered by forage Copncentrate supply Forage intake
Body temperature Homeothermia Hypothermia Hyperthermia Heat loss or production Comfort Basal metabolism Ambiant temperature Letal temperature Low critical temperature Thermal neutrality High critical temperature Letal temperature Thermogenesis includes heat supply from the environment
Effect of temperature on animal physiology Direct action on LH peak and frequency, on estrus expression, follicular growth, blood flow and thus uterine environment, fetal growth Indirect action from lower intake
Effect of an increase in on high critical temperature hygrometry Limitation of evaporative losses wind speed Heat losses sunshine Heat supply
Reproduction : major effect on heat stress Holstein bred in Florida Fertility is decreased when maximum temperature is higher than 30 C
Lower milk / muscle yield at high temperature 1 ) Mainly due to low intake 2 ) proper effect of temperature on metabolism Lower milk protein content at high temperature Due to the lower energy supply The effect of temperature is lower for concentrate-rich diets Lower heat production during mastication and digestion Better metabolic efficiency
Temperature ( C) 20 30 30 Hygrometry (%) 50 50 70 Feed intake (basis = 100) 100 76 60 Milk yield (basis = 100) 100 75 62 Low thermolysis Decrease in metabolism through decrease in feed intake
Development of a temperature-humidity index several formulas using different types of measures of humidity and air temperature THI 80 Severe Impact (heavy losses in production and livestock) Strong Impact (milk yield, fertility, health, mortality Moderate Impact (milk yield, fertility) 70 No Impact
Decrease in production (kg / day) 0 Milk production 14 kg / day 5 23 kg / day 70 Temperature humidity index 80
How to alleviate heat stress through animal resources As an adaptation of farming systems in hot areas, to maintain or increase production and farmer income under environmental constraints which are increasing Constraints for resources result in the implementation of solutions implemented by the farmer First step : characterisation of constraints. Second step : identification of adaptation techniques of farming systems, in particular of animals
Milk yield (kg) Low critical temperature High critical temperature Examples of critical temperatures : low, Holstein : 5 C high, Holstein : 21 C high, Brahman : 32 C This does not mean that high critical temperatures are always higher for tropical breeds
Variations between breeds the most adapted to heat stress are (in theory): Tropical breeds > crossbreds > temperate breeds Light breeds are better (skin surface) Breeds with short and light coat Independently of heat stress, some breeds are especially adapted to water deprivation, to resistance to diseases, to lipid storage, etc.
High diversity of animal resources Number of local breeds Number of breeds with international dissemination (FAO, 2007)
Example of cattle breeds in Mayotte Island Fertility rate (%) 0-1 yr mortality rate (%) 1-2 yr Liveweight gain (g/d) Milk yield (kg/yr) and DIM Zebu 39 10 167 258 (103) Crossbred 60 22 254 1265 (305) Montbeliarde 69 20 554 2454 (305) Remarks: This is an example, and differences between local and exotic breeds may be of lower extent Montbeliarde produces 3 times less milk than in France
Possibility of adaptation according to breeds Example of Guadeloupe (FWI) Creole cows: conception during rainy season Holstein cows : conception when temperature is low Holstein Creole % of annual conceptions THI Rainfall Month of conception
Thank you for your attention