By Dr Andrew Tucker – Charles Street Veterinary Consultancy
A drop in the conception rate over the hotter months of the year can be caused by summer infertility. It is often thought of as a sow problem, while in fact boars can be equally responsible. During this period sows can remain cycling, but not show any signs of coming on heat. Sows may also show different to “normal” signs of heat, for example she may not stand as strongly as normal or for as long a period, or she may even stand a little later than normal. Boars are affected during this period as the higher temperatures can have a negative impact on semen quality. High temperatures can also result in boars having lower libido.
What causes summer infertility?
Summer infertility is caused by two main factors, daylight length and high temperature. This is nature’s way of stopping sows from farrowing in the colder winter months when food is scarce and temperatures are too low. This is a residual effect remaining from the ancestral European Wild Boar which, like many of our local game species, will only have offspring once a year in spring or early summer.
How do you avoid having summer infertility?
A few different methods have been found to avoid summer infertility.
• Reducing temperatures, particularly in the mating and boar accommodation, is very important.
• Working with the sows (heat detection and AI) during the cooler times of the day.
• Manipulating daylight length. This can be done in indoor sows by using adequate light intensity for a set amount of time.
• Adequate boar stimulation has been shown to reduce summer infertility.
• Some effects have been seen on nutritional trials where satiety has shown positive results, this could be due to a lowering of stress levels?
• Accurate heat detection and insemination only when the sow is on full heat goes a long way in minimising summer infertility. Rigid AI programmes that do not allow for changes in how long the sow comes on heat or how she shows heat, result in inaccurate service and poor conception.
Pig Diseases – D.J. Taylor; Diseases of Swine – Straw, Zimmerman, D’Allaire, Taylor