Are your dry cows getting the right nutrition?
Published 1 October 08
Are your dry cows getting the right
During dairy cows' dry periods it's essential farmers calculate and monitor feed requirements to avoid health problems after calving.
Producers often pay great attention to milking rations but forget to plan dry cow rations just as carefully. It is just as important to balance requirements for dry cow rationing as for milking rations.
As a rough guide daily dry matter intake in the dry cow should be 2% of bodyweight, with energy content at 15% of bodyweight, plus 10 MJ. So, a 600kg cow potentially needs a dry matter intake of 12kg/day and an energy requirement of 100 MJ/day. She would therefore need a ration average of less than nine MJ/kg DM - and it is very important to balance the ration as many feeds easily exceed this level.
The danger of overfeeding is that insulin levels rise and the cow stores the excess energy as fat. If this continues every day, insulin levels rise over time and the body responds less and less, as in humans. This insulin resistance affects energy metabolism well into the lactation - reducing the cow's energy intake after calving, which results in sharp weight loss, and has knock-on impacts on milk yields and fertility.
Fat cows are also likely to suffer from Ketosis because of their reduced feed intake after calving. Ketosis occurs when normal cycles in the body become overloaded and ketones accumulate in the blood to toxic levels. This is due to a severe negative energy balance caused when the cow is using more energy to produce milk than it is consuming. Correct energy inputs during the dry period to maximise dry matter intakes after calving will help to mitigate this problem.
Dry matter intake is also important to prevent against displaced abomasums (DAs). Rumen fill is the main influence on DAs, and an energy balanced feed will allow high dry matter intakes, ensuring the abomasums are kept in place by a full rumen. If DAs are a problem ensure that they aren't secondary - many are caused by something else affecting the cow which stops her from eating - this is a key time for careful cow management.
It is also essential not to underfeed the dry cow. Underfeeding can happen when using poorer quality forages with low intake potential. This will lead to excessive fat mobilisation, which can go unnoticed. Primarily it is the internal fat deposits that get used up first, so it is important to handle the cows and monitor their condition throughout the dry period.
Weight loss during pregnancy can also cause retained foetal membranes after birth. There is a fine line to getting dry cow nutrition right, and cows will need careful management throughout the dry period. It's worth discussing your dry cow ration with a nutritionist and your vet - a balanced ration will pay off in maintaining low levels of metabolic disease at a key time in early lactation.
Use of grazing can be challenging as it is easy to overfeed both energy and protein with good quality grass averaging over 11 MJ/kg DM. Limiting intakes through correct grazing allocation is therefore very important.
Feeding straw is a popular option due to its low energy level of between six and seven MJ/kg DM, compared with mature silage at between nine and 10 MJ/kg DM, and concentrates at around 12 MJ/kg DM. Use of these feeds must therefore be balanced accordingly.
Balancing minerals is also important, so producers should be careful not to feed silage from fields with high potash indices, as this increases the risk of milk fever. And although forages alone will meet the energy requirements of the dry cow, the rumen flora will need time to adapt to different feeds. Feeding a small amount of concentrate in the last few weeks leading up to calving will help the re-introduction of the milking ration.
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