Mating & Heat Stress

Increased heat loads during periods of continuously hot humid weather can be severe on conception rates and in-calf rates particularly in higher-producing cows.

Mating management

When considering the timing of your calving pattern, it is worth factoring in that mating during hot summer months will have an adverse effect on fertility outcomes.

When considering calving strategies, allow for the following impacts in hot season mating periods:

  • Oocyte quality will be reduced resulting in lower conception rates.
  • This will be less of an issue in heifers than in older cows.
  • Cows are less likely to express oestrus behaviour in hot weather. Heat detection techniques will need to be intensified.
  • Bulls will be less inclined to be active. Increasing the number of bulls might be necessary.

During hot conditions, reduced fertility can be avoided by:

  • Minimising the time cows are standing around in hot yards waiting to be inseminated.
  • Providing a shaded area for these cows.
  • Increasing the use of heat detection aids.

Heat detection

Cows are more likely to have silent heats or shortened heats in the hot season. Accurate heat detection is critical to achieving high submission rates. Expect cows calved in summer to take longer to start cycling than cows calved in winter.

The key is to increase your heat detection efforts over the summer months and manage cows not detected on heat.

See chapter 10 of the InCalf for more information.


Artificial insemination practices for heat stressed cows

Increased heat loads during periods of continuously hot, humid weather can be severe on conception rates particularly in higher producing cows. It would be prudent to lower fertility expectations for mating carried out during hot periods.

Make sure you are not blaming the hot weather for problems caused by poor procedures. Ensure that all AI practices are up to scratch including general preparation and cow handling, semen storage and handling, insemination techniques and timing.

Assess your herd using the InCalf AI practices tool and see chapter 11 of the InCalf Book for more information.


Calving pattern decisions

Altering calving patterns to avoid extreme heat will only partially address the effects of heat stress on mating performance, conception or calving rates.

The extra cost of cooling infrastructure may deliver better outcomes in herd fertility performance than delaying or changing calving patterns. Extreme heat events should be a just one of the many factors considered when deciding the best management approach.

Access the InCalf herd assessment tools and the InCalf Book for more information.

View the InCalf Book