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Alleviating the stress of winter housing

By Alice Coppin-Harris, Veterinary Surgeon BVMSci MRCVS

As we start to think about bringing cattle in for the winter, it is important to remember housing can be a very stressful time for cows.

Increased stress can raise blood cortisol levels which can lead to a suppression of the immune system. If combined with pressures like high stocking densities, poor ventilation or unhygienic housing conditions, disease can spread rapidly through a group of animals.

Taking time to inspect your buildings prior to housing can help to increase productivity and prevent injury and disease throughout the winter.

A well-designed ventilation system will use the ‘stack effect’ - where hot air rises and is replaced by cooler air - to provide a uniform distribution of fresh air on a still day, without relying on a breeze. This ensures excess heat and moisture are removed from the building, as well as harmful gases and airborne pathogens.

As cattle expel warm, moist air with every breath, lose heat through the evaporation of sweat and produce litres of effluent daily, moisture in any building is unavoidable.

However, inadequate ventilation allows excess moisture to raise the humidity of the shed, enabling respiratory and other pathogens to survive for much longer and reducing the effectiveness of heat loss through evaporation.

Humidity not only increases the risk of pneumonia, but also of digital dermatitis and environmental mastitis from damp beddingand flooring.

You can prevent additional moisture by positioning water troughs in well draining areas and scraping passageways and beds frequently, but this will not eliminate the need for suitable ventilation.

Optimising photoperiod length, light intensity - measured in lux - and light uniformity can also have a significant impact on the health and production of your dairy herd. It can advance the onset of puberty in heifers, increase milk yield and improve liveweight gain.

In the UK, the number of hours of light cows are exposed to daily varies between farms. Some dairies follow a natural daylight pattern, others only have a few hours of darkness and some are artificially lit for the full 24 hours.

Evidence shows switching to a Long-Day Photoperiod (LDPP), where cows are exposed to 16-18 hours of light - above 170 lux - followed by six to eight hours of near total darkness - less than 5 lux - can increase yield by up to 3kg a day.

The increased light exposure inhibits the production of melatonin in the pineal gland, which in turn influences the production of hormones such as IGF-1 and prolactin which directly impact milk production.

In contrast, dry cows should be housed separately and exposed to a Short-Day Photoperiod (SDPP) with eight hours of light and 16 hours of darkness.

The additional hours of darkness in the dry period help boost the immune system and increase the expression of prolactin receptors in the udder, leading to an increased yield in the subsequent lactation.

To ensure cows are exposed to the required photoperiod, lights should be positioned to create a uniform light intensity throughout the building. Dark corners should be avoided and light intensity must be measured at cow eye-level.

To help with cattle observations in the dark, low intensity red lights can be used without influencing melatonin production.

The type of light source used in housing does not influence cattle performance. Lights can be selected based on price, start-up and running costs, as well as longevity and replacement rate.

Opting for more efficient LED lights can have both environmental and financial benefits in a time of ever-increasing energy bills. They use less energy to run, have lower replacement costs and have even been shown to attract fewer flies.

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