Lower energy and protein from early first cut silages

19th June 2023 | Animal Feed, Forage

Analysis of early first cut gras silage samples indicate lower energy and protein contents than at the same stage of 2022, advises Trouw Nutrition GB.

The company has aggregated results from the first 500 samples of 2023 crop analysed at its Ashbourne laboratory, the UK’s largest forage testing facility. Trouw’s ruminant technical development manager Dr Liz Homer reports that the silages are generally well fermented with an average 30.9% dry matter (DM). The warmer winter meant that many swards never fully stopped growing, resulting in a higher proportion of more mature grass.

“This will have an impact on digestibility and energy levels,” notes Dr Homer. “Overall metabolisable energy (ME) is slightly lower than last year at 11.1 MJ/kgDM. While the non-digestible fibre (NDF) score is similar to 2022’s early silages at 44.5 %DM, the lignin content is higher which will be contributing to lower energy contents.”

Lower average protein levels may indicate reduced nitrogen fertiliser applications this year due to the wet spring, she continues. Also, growers in some parts of the country cut earlier to take advantage of a spell of better weather. Average crude protein so far this season is 14.3% (15.2% in 2022), which has contributed to a reduced fermentable protein supply.

Early 2023 grass silage analysis

Dry Matter%16.030.960.7
D Value%57.069.476.1
MEMJ/kg DM9.111.112.2
Ligning/kg DM13.040.176.8
Lactic Acidg/kg DM2.079.1158.3
VFAg/kg DM0.544.4128.3
Rapidly fermentable Proteing/kg DM44.592.5162.7
Total Fermentable Proteing/kg DM50.1104.1196.3
Rapidly Fermentable Carbohydrateg/kg DM108.0192.8238.6
Total Fermentable Carbohydrateg/kg DM330.3417.2569.5
Acid Load26.748.559.0
Fibre Index133.1178.2269.9

Source: TNGB

Dr Homer stresses that the data so far comes from early cut crops, but says the figures are a good predictor of how the majority of crops will look and prospects for the 2023/24 winter forage. While farmers in the south of the country managed to get an early first cut, northwest farmers struggled to get fertiliser on, which will have delayed cutting.

“By sampling clamps regularly during the season, it will be possible to maintain a current picture of the forages being fed,” Dr Homer. “Then growers should work with their nutritionist to balance the diet for rumen function, energy and protein to optimise the contribution from forage, increase feed efficiency and reduce the environmental footprint of feeding cows.”

In particular, high energy silages will need to be balanced correctly, she warns. They tend to be lower dry matter crops which will ferment more quickly, potentially with higher lactic acid contents and higher acid load which will compromise rumen health.

In addition, the lower fermentable protein levels, combined with lower fermentable carbohydrates, mean that the supply of digestible intestinal protein will be severely impacted.

“To overcome this, it will be important to supplement carefully with energy and protein sources,” advises Dr Homer. “It will not just be a case of increasing the crude protein in the diet, but instead balancing the supply of energy and protein in the rumen to optimise the production of microbial protein, while supplying the appropriate levels of bypass protein,” she concludes.