MGA conference key points

Post-emergence slurry application and obese cows were the main topics at last week’s Maize Growers Association Conference, Cirencester.

Strategic application of slurry on emerging maize at the one- to two-leaf stage can create a new window of opportunity to reduce slurry stores and give a good yield response, according to Maize Growers Association trial data.

“MGA trials have shown that applying 60kg/ha nitrogen equivalent of slurry, post-emergence, will give a maximum return on yields of more than 14.25t/ha of dry matter,” said Simon Draper, MGA agronomist.

“There appears to be a good yield benefit from applying slurry post- rather than pre-emergence,” said Mr Draper, “But there is no benefit from applying more than 60kg/ha.”

“Applying slurry at this stage also gives a good opportunity to get rid of slurry,” Mr Draper continued, “something that is even more important in light of the new NVZ regulations.”

Precise placement of slurry can also increase phosphate uptake, said Leif Knudsen from the Danish Agricultural Advisory Service. “Maximum uptake of phosphate can be achieved by placing slurry 5cm away from the row. Anymore than 11cm from the row and the system doesn’t work.” Although the merits of precise application were suggested, there was no evidence that placed slurry could act as a substitute for placed mineral NP fertiliser.

MGA trial data also gave interesting results as to alternative chemical weed control on maize following the ban on atrazine, said Mr Draper.

“Six weeks of weed competition in young maize plants can reduce yields by 5-6t/ha compared to a weed-free crop,” said Mr Draper. This stresses the importance of early weed control.

In controlling redshank pre-emergence, using Cadou Star in combination with pendimethalin (Stomp) produced the best results, However, fat hen was controlled best with just Cadou Star.

Most significantly, there was poor long-term control of weeds with pre-emergence herbicides. Inspection of the crop in early August showed that weeds had remerged. “This suggests pre-emergence sprays lose their strength,” said Mr Draper. “Results show that using a combination of pre- and post-emergence herbicides will give the best results. In fact using both applications gives 100% control of redshank.”

“Using a pre-emergence herbicide will give the best yield response but, if you want a clean crop throughout, you will need to use a pre and post-emergence spray,” said Mr Draper “At the very least, I would strongly advise all maize growers to use a pre-emergence herbicide or a very early post-emergence treatment.”

 Slurry-spreading
Applying slurry to maize post-emergence will give good yield benefits

Obese cows are prone to developing “bovine type two diabetes”, according to Dai Grove-White from Liverpool University.

The key to any dry cow feeding programme is minimising weight loss post-calving by maximising dry matter intakes. This will prevent the onset of post-natal conditions such as fatty liver or ketosis.

“Obesity is a real issue in dairy cows,” said Mr Grove-White, “Fat cows will have decreased dry matter intakes in the dry period and early lactation and increased weight loss in early lactation, making them more prone to fatty liver syndrome.

In the long term they will also have reduced milk yields.”

“Research suggests a lot of the processes involved in fatty liver are similar to type two diabetes in humans. We are getting to a stage where ‘bovine type two diabetes’ is a real problem.”

“I would say any cow over body condition score three is obese. These are the ones that become hat-racks after calving.”

The issue lies in how fat is distributed in the cow, according to Mr Grove-White. “Subcutaneous fat is the fat layer we can see by eye, and is what we use when body-condition scoring. However, there is still a large proportion of fat that is ‘hidden’ as visceral fat inside the cow.”

“Body condition scoring is a fantastic tool but it only acts as a measure of fat on the outside. With Holsteins this is a real issue. A Holstein may be thin on the BCS scale, but she may be piling fat reserves on inside.”

A body-condition score of more than three suggests high visceral fat reserves. “In humans, high levels of visceral fat in the abdomen is a real sign of diabetes,” said Mr Grove-White.

“Reduce the energy intake of any cow with a condition score over three, 100 days before drying off,” said Mr Grove-White. “Any cow with a condition score of four or above at this stage should be culled.”

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