Why should you consider using J Grennan calf jackets?

There have been a number of studies completed across Irish and UK farms in recent years which suggest that calf jackets can contribute to better health and performance, particularly with young calves.

  • Approximately 1/3 of farms have draughty conditions, which can result in excessive heat loss
  • Increased ADG can be observed in young calves in particular (3-4 weeks)
  • Reduce impact of ‘cold stress’ when temperatures drop below lower critical limit
  • Reduced disease incidence in young calves, particularly scour
  • Lower stress levels in calves that are put in jackets (bought in calves at transportation/mixing with other sources)


When a calf is born their Lower Critical Temperature is approx. 13⁰C and reduces to approx. 6⁰C by the time they are 30 days old. Therefore, if housed in unsuitable draughty conditions, damp bedding or in particularly cold periods young calves will be using their energy to maintain body temperature instead of contributing to ADG, immune function and organ development.

In the first four weeks of life, the calf is most vulnerable to disease so ensuring energy intake is devoted to thrive and reducing sources of stress to the calf will ensure a more effective immune system to tackle disease challenges that arise.

For every 5⁰C drop in temperature a calf’s requirement for milk replacer increases by 50g or approx. 0.5 litre milk, calf jackets will ensure the calf’s body temperature will be maintained during these periods as increased nutrition to counteract the cold in young calves can often be overlooked during such a period on farm!

So don’t forget to:

  • Ensure the calf is dry before putting on the jacket
  • Ideally leave on until 4 weeks of age
  • Prioritize the most vulnerable animals (Less than 10 days or ill)
  • Machine wash at 60⁰C and dry thoroughly between calves
  • Do your utmost to reduce draughty conditions and maintain dry, clean beds!