Heat Stress in Cows

As of April in our country, sunny days begin in many regions. This period in which temperature and proportional humidity also increase; It is the process in which serious stresses begin for Dairy Animals and yield losses are experienced in enterprises. Some precautions should be taken during this period in order to minimize the welfare and productivity losses of animals. Animals have serious reactions during this period, which we call Heat Stress.

What is Heat Stress?

Shaped by rising humidity and air temperatures in the summer months; It is a seasonally related problem that manifests itself with the decrease in Meat, Milk and Offspring Yields, the decrease in feed consumption and various Metabolic disorders that occur with them.

When Does Heat Stress Start?

  • The ideal temperature range for cattle is 0C in the shade: ( -5 ) and ( +25 )
  • The environmental temperature at which a cow gives the highest yield is 13 – 18 0C and a maximum of 50% relative humidity.
  • In addition to the environmental heat, humidity plays a significant role in the formation of heat stress, and temperature stress will occur at lower temperatures in regions where humidity is high.
  • Stress begins in cases where the temperature is 23-24 0C and the humidity is 75% and above.

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  • In cases where the temperature is 30 0 C and the humidity is 45 – 50%, yield losses occur.
  • In cases where the temperature is 38 0 C and above and the humidity is 50% and above, Metabolic Problems and Yield Losses are formed.

Problems Caused by Heat Stress:

  • Feed Consumption decreases
  • Milk yield decreases
  • Reproductive problems
  • Romanian Acidosis
  • Nail Problems
  • Fragrant Diarrhea
  • Reduction in milk fat

Physiological and Behavioral Effects of Heat Stress

  • In cases where the temperature rises above 25 – 26 0 C, a decrease in feed consumption begins in cows.
  • In cases where the temperature rises above 32 0 C, there is a serious decrease in milk yield in high-yielding animals.
  • With a decrease in feed consumption, the number of ruminants decreases. When rumination decreases, the pH of the rumen decreases (increases in the direction of acidity) The digestive system is adversely affected
  • The frequency of feed consumption decreases, animals are more often; consumes the essential feeds that it finds delicious, loves its aroma, coarse feed consumption decreases, concentrated feed consumption increases,
  • The number of respirations increases,
  • Since sweating is not enough, it cannot balance the body temperature, as it is like water vapor,

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  • Saliva production and bicarbonate density of saliva decreases,
  • Subclinical and Clinical Acidosis is formed.
  • As a result of acidosis, Digestive System Problems occur, then nail problems and lameness are formed,
  • absorption of nutrients decreases,
  • Life share nutrient needs increase,
  • Milk yield decreases, the amount of fat in milk decreases,
  • Mobility slows down,
  • The search for cool and shadowy places increases.

Impact on Overall Yield

  • Milk yield can be reduced by amounts exceeding 25%
  • Only 40-50% of the yield loss experienced during heat stress is due to reduced feed consumption.
  • Despite the falling consumption of feed, body fat reserves cannot be sufficiently mobilized.
  • Fertility is greatly affected by heat stress. Up to 4-fold reductions in reproductive performance were detected in herds under heat stress. There are serious problems with anger and fertilization.
  • Imbalances in the hormonal structure are observed.
  • In mothers under temperature stress, the blood flow towards the uterus decreases and the uterus temperature increases. This adversely affects embryonic development and increases the rate of early embryonic death.
  • The number of inseminations for a pregnancy increases and also reduces the number of successful inseminations.