Challenging maize harvest affects forage quality

20 Nov 2020

Regular analysis of forage and fine-tuning of diets will be essential to make the most of this year’s maize silage, according to Trouw Nutrition’s Liz Homer.

She says that there will be a wide variation in feed value, reflecting the growing season. “While many crops were taken early, maturing quickly in the good weather in September, harvesting of many crops was then delayed by the wet start to October. This resulted in some very mature crops being cut.”

Considerable range

The results from the first 900 samples analysed by the company are likely to, primarily, be from earlier harvested crops. “On average these crops have a similar dry matter to 2019, at 32.1%, but there is a considerable range,” says Dr Homer. “With varying crop maturity, both D value and ME are slightly lower than 2019.

“On average, starch is 1% down on 2019, at 30.1%, but there is a large proportion of samples within the 30% to 35% starch range. Starch degradability and bypass starch are similar to 2019, which should support milk production.

Late harvest

“Compared to 2019, NDF, ADF and lignin levels are all slightly increased, reflecting the digestibility of the crop. It is probable that late harvested crops will have lower digestibility that those taken in good time, which will present different feeding challenges.”

Dr Homer adds that, on average, the reduced digestibility means that both total and rapidly fermentable carbohydrates are reduced. This is reflected in a lower acid load, meaning that rumen health will be better. However, she emphasises that acid load can change with time in the clamp as starch digestibility increases.

Correctly balanced

“It will be crucial for producers to get their own clamps analysed throughout the season, so their nutritionist knows the quality of the forage available to start diets are correctly balanced. Earlier silage could feed well, but later crops will potentially be less digestible and, with reduced starch degradability, require different supplementation.

“Consideration will also need to be given to the balance of forages in the diet. If maize is fed with lower digestibility grass silages then cereals may be needed to promote good rumen function,” adds Dr Homer.

Additional protein

“Many grass silages have anaylsed with lower crude protein levels. If these are fed with low starch maize silage then supplementation with both cereals and additional protein will be needed.

“With regular analysis and careful balancing it should still be possible to achieve good levels of milk from forage to help control feed costs,” Dr Homer concludes.