Fine-tune diets to make most of improving maize quality

Maize degradability improvements in the clamp may offer farmers the opportunity to reduce cereals in dairy cow rations. Dairy Update reporters find out more.

Improvements in maize silage starch degradability may allow farmers to reduce concentrates and lower feed costs while reducing the risk of acidosis.

Starch availability from maize silage depends on both actual starch content and starch degradability. The degradability determines the proportion of total starch that will be available in the rumen.

See also Advice on how to improve the yield of your maize crop this year

Initial analysis of maize silages by Trouw Nutrition GB (formerly Frank Wright) showed an average starch content of 34.5% and an average degradability of 65.1%. However, starch degradability was as low as 17% and as high as 80%, indicating huge variations in rumen starch availability.

A high percentage of starch does not always ensure a high level of starch in the rumen, explains ruminant manager Adam Clay.

“When formulating diets, you need to pay attention to both starch content and degradability as together they affect how the forage will perform. It is possible for cows to be oversupplied with rumen energy at quite modest maize starch contents if degradability is high. Oversupply of rumen energy can increase the acidosis risk,” he adds.

“Equally, cows can be tight on rumen energy where starch contents are high but degradability is low. A shortage of rumen energy will reduce performance.

“The longer the crop stays in the clamp the more degradable the starch becomes and, irrespective of actual starch content, the proportion of rumen starch increases.”

As most maize crops have been in the clamp for five months now, Mr Clay says degradability will have increased significantly since the crop was first analysed. He says farmers and their nutritionists should modify diets accordingly.

“Get maize silage analysed again to see how the degradability has changed. If the supply of rumen starch from maize has increased, it might be possible to reduce cereals in the ration and lower feed costs. This will also reduce the acidosis risk that will have increased if rumen starch levels have risen,” Mr Clay advises.