The average GB grass growth has continued to decline this week to 38 kg DM/ha/day, a reduction of 9 kg DM/ha/day. There is a wide variation in growth rates between the North and South, with Scotland maintaining an average growth rate of 61 kg DM/ha/day whilst the South West average has declined to 29 kg DM/ha/day. The variation in growth rates is also reflected in the average milk yield from grazing figures with Scotland achieving a potential milk yield from grazing of M+ 20.4 litres, whilst the average for Wales and the West has declined to M+ 9.9 litres. The potential milk yield from grazing for Devon, Cornwall and Somerset is even lower with an average of M+ 3.8 litres. Careful interpretation of the overall GB average milk yield from grazing figure of M+ 14.5 litres is therefore required and the situation on individual farms assessed.
Buffer feeding is now essential in many parts country to maintain dry matter and fibre intakes. Careful attention to the composition of the buffer feed is required to ensure highly digestible fibre is also available. Decreasing fibre levels and increasing the amount of starch in the diet to try and increase energy density will further increase the risk of acidosis for animals already suffering the effects of heat stress. Heat stress increases respiration and reduces the amount of bicarbonate in the saliva reducing the overall buffering capacity. Heat stress also increases saliva loss through drooling further reducing the natural rumen buffering capacity of the animal. With the risk of acidosis in mind, coupled with the need to keep winter forage stocks use to a minimum, increasing the concentrate proportion of buffer feeds with a high energy, high NDF concentrate will be an important consideration.
With the very high temperatures set to continue into the middle of next week it will be important that actions are taken wherever possible to reduce the effects of heat stress. These include:
- Ensure water is easily and freely available
- Allowing access to shade such as housing, gives cows an option to escape the direct sun
- Minimize moving cows during the heat of the day
- Minimize the time when cows are gathering together in the collecting yard
- Fans get air moving to help cool the surrounding area and dissipate heat – especially in areas where cows are gathered such as collecting yards
- Sprinklers or hoses can be used in collecting yards to cool cows waiting to be milked. One downside is that wetting cows may increase the moisture in lying areas and increase the risk for environmental mastitis.
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