Precision feeding key to maximising forage potential

18 Sep 2020

This year’s grass and wholecrop silages have the potential to support good intakes and levels of production, but will require regular analysis and careful supplementation if the full benefits are to be realised.

So says Trouw Nutrition GB’s Liz Homer, after sharing the results from the UK’s largest dataset of silage analyses.

“Care will be needed when formulating diets this winter if the most value is to be realised from silages,” she says, urging producers to make sure the analysis being used reflects the silage currently being fed and also advising regular analysis.

Monthly analysis

“Silage quality can change significantly as you move through a clamp. Because the crop can be affected by factors including the type of sward cut, the weather on the day it was harvested and how well it was consolidated, we advise carrying out an analysis at least monthly,” says Dr Homer. 

“With results typically available on the same day that the sample is received at the lab, diets can be quickly checked and fine tuned as required.

Accurate parameters

“It is then vital to make sure that diets are calculated on the most accurate parameters,” she adds. “Most analyses don’t go much further than metabolisable energy and crude protein. They fail to indicate how a feed will perform in the rumen and the type of supplementary feeds that will be required to best balance the diet.”

Dr Homer explains that cows do not produce milk from silage, but from the products of digestion when feeds are fermented in the rumen, or pass through to the gastro-intestinal tract. New parameters are now available that describe how feeds will perform when eaten, what the rumen bugs require, and how much bypass energy and protein is needed to balance the overall diet.

Cost-effective performance

“Unless the rumen is balanced in both nutrient terms and the rate of fermentation, cows will not perform as expected,” she continues. “Basing diets on a regular silage analysis, which includes the details to understand exactly how silages will perform in the diet, will make it possible to formulate rations for more cost-effective performance.”

This year’s silage analysis results show that producers who managed to get on early and had little disruption from the weather had excellent first cuts. “Later first cuts have slightly higher NDF and lignin, but lower crude protein and are, typically, drier crops. Although the averages don’t look too different, quality is much more variable in later first cuts,” says Dr Homer.

Crude protein

On average, 2020’s first-cut silages are well fermented with a dry matter close to the optimum at 36.5%. Headline numbers for feed value are good at 11.3MJ/kgDM, with low NDF. But silages are typically low in crude protein, averaging 14.3% (see Table 1).

She adds that second cuts also have the potential to feed well, although both NDF and lignin are higher. To date, a relatively small number of third cuts have been analysed, presumably from producers who were able to take an early first cut, but again the headline analysis is encouraging.

For wholecrop, she says that dry matter is similar to previous years. While ME levels are typical for wholecrop silages, the starch content in these early crops is slightly lower and this will affect how they will feed.

 

Table 1: Nutrient analysis for grass silages 2020 (Source: TNGB)

 

Early 1st cut

1st cut

2nd cut

3rd cut

Samples

660

3733

1724

378

Dry matter (%)

35.5

36.5

35.0

34.8

Crude protein (%)

14.6

14.3

14.4

14.9

D value (%)

71.5

70.3

67.3

67.0

ME (MJ/kgDM)

11.4

11.3

10.8

10.7

NDF (%DM)

44.1

44.8

47.5

46.4

Lignin (g/kgDM)

33.9

35.2

37.5

37.7

pH

4.2

4.3

4.3

4.3

Rapidly Fermentable CHO (g/kgDM)

202.6

200.1

184.7

185.6

Total Fermentable CHO (g/kgDM)

457.5

455.5

446.6

441.8

Rapidly Fermentable Protein (g/kgDM)

90.5

87.7

86.7

90.3

Total Fermentable Protein (g/kgDM)

110.3

106.6

104.3

107.9

Acid load

49.5

48.5

45.8

46.6

Fibre Index

176.9

180.1

191.1

186.2

Dynamic Energy (MJ/kgDM)

6.30

6.21

6.08

6.10

NDIP (g/kgDM)

64.2

63.5

61.6

61.7

NFEPB (g/kgDM)

11.4

8.6

8.9

12.8