Nutrition

The benefits of high temperature drying

Crops of grass and lucerne are grown and managed specially for high temperature drying. The main species of grass used are perennial ryegrass and tall fescue, but some high quality permanent swards are also used. They are cut at regular intervals throughout the year in order to produce a feed with a high and consistent nutritional value.

Lucerne is usually cropped for three years as part of an arable rotation. Unlike grass, it does not require nitrogenous fertilisers as it fixes its own nitrogen from the atmosphere.

After mowing, the swath is usually allowed to wilt for a few hours before being picked up with a forage harvester and hauled to the dryer.

The drying process

The harvested crop is dried in a rotary drum dryer (rather like an enormous tumble dryer). The fresh grass or lucerne is fed into one end of the dryer, through which is drawn hot air at around 800 degrees centigrade. As the material passes through the rotating drum, the majority of the water is rapidly evaporated from it so that when it emerges from the other end, the moisture content has been reduced to about 12 per cent. The process not only sterilises it, but also produces a feed that contains virtually all the nutritional value of the crop from which it was made.

The dried material is then usually milled and pelleted before being cooled to make it safe to store. Some producers leave it in its chopped form and then bale it to provide a source of long fibre – ideal for stimulating rumen function in high yielding dairy cows.

The nutritional value of British Dried Grass and Dried Lucerne

British Dried Grass and Dried Lucerne are high quality, natural feeds produced from crops grown and managed specially for high temperature drying. They are wholesome, healthy, safe, unadulterated and, above all, traceable feeds in which livestock farmers and nutritionists can have full confidence.

As well as being totally natural feeds for dairy cows and all other types of ruminant, Dried Grass and Dried Lucerne (referred to as ‘Dehy’ within the industry) offer a number of features that can make them invaluable in formulating a balanced diet.

Excellent supply of DUP

The high temperature drying process, with an air inlet temperature in the region of 800 degrees centigrade, protects some of the protein from breakdown in the rumen, so increasing the level of DUP. This can be important in helping to maintain milk yield and protein levels.

Good source of FME

Unlike the fermentation process during silage making which uses up most of the FME in the grass to feed the organisms that produce the acid needed to preserve the crop, the high temperature drying process preserves this naturally occurring FME, so important in helping to sustain the rumen micro-organisms.

Highly digestible fibre

Investigations have shown that Dehy produced from grass cut at frequent intervals contains highly digestible fibre, beneficial in helping to balance rumen VFA production. For this reason, most driers now aim to cut their grass at 35-day intervals as far as possible.

Valuable levels of NDF

Dried Grass and Dried Lucerne contain relatively high levels of NDF which can play an important role in buffering high starch and acidic feeds.

Excellent source of Beta-carotene

Dehy is an excellent source of Beta-carotene, which is particularly low in many other concentrates used for ruminants. The need for extra Beta-carotene is even greater when maize silage and other maize products are included in the diet.

Changes in ruminant production systems over the past few years – changes in milk markets, the effect of BSE, concerns about natural ingredients etc – have all made the attributes of high quality Dried Grass and Dried Lucerne more important than ever before. But, although for many years the advantages of using Dehy in ruminant diets has been acknowledged, a lack of information and a worry about variability has sometimes made it difficult for nutritionists to incorporate it in diets. In an effort to overcome these concerns, a comprehensive, independently operated monitoring programme has been undertaken by BAGCD to fully evaluate contemporary British Dehy.

As a result of this work – and earlier scientific analyses looking at the digestibility of the products – it is now possible to provide all the data needed for modern diet formulation. Click here for typical analysis.

British Dried Grass and Dried Lucerne for dairy cows, beef and sheep

Fresh grass and lucerne are natural feeds for dairy cows and all other ruminants. They are the crops these animals have evolved to eat; the forages their digestive systems utilise most effectively. It follows, therefore, that high temperature dried grass and lucerne are also natural feeds for ruminants, having simply had most of the water removed.

Natural supply of quality protein

The protein in any dairy cow diet must be balanced between the amount supplied to the rumen micro-organisms (Effective Rumen Degradable Protein, or ERDP) and the amount available directly for chemical digestion further down the digestive tract (Digestible Undegradable Protein, or DUP), As most forages supply ample ERDP, it is often the DUP or ‘by-pass’ protein that needs to be topped up via the concentrate. This is particularly true with higher levels of performance.

Although grass and lucerne entering the dryer are, like grazed forage, high in ERDP and relatively low in DUP, the product that leaves the dryer has changed. The short period of intense heat needed to reduce the water content protects some of the protein from breakdown in the rumen and so increases the level of DUP.

Protein values at 8% outflow rate

    Fresh
grass
75D
Grass
silage
70D
Dried
grass
Lucerne
silage
Dried
lucerne
Crude
protein
g/kgDM 190 174 199 194 199
ERDP
(r=0.08)
g/kgDM 124 116 103 135 114
DUP
(r=0.08)
g/kgDM 40 25 60 20 45
Change
in DUP level
-37.5% +50%  

Source: Energy & Protein Requirements of Ruminants, AFRC

It can be seen that whilst high temperature drying improves the protein profile, silage fermentation actually decreases the DUP available. This clearly makes Dried Grass and Dried Lucerne ideal balancers for use in silage based diets.

Quality energy

The newly adopted Metabolisable Protein system takes the concept of a two-stage digestive system further by accepting that energy also needs to be supplied in two forms. Metabolisable Energy (ME) has therefore been split to show the amount available for use in the rumen – the Fermentable Metabolisable Energy (FME).

As grass and lucerne are natural feeds for ruminants it is not surprising that they are good sources of FME and so help to ensure maximum production from the rumen micro-organisms.

Whilst the fermentation process during silage making uses most of the FME available to feed the organisms that produce the acid needed to preserve the crop, the high temperature drying process preserves this naturally occurring FME in Dried Grass and Dried Lucerne.

Energy values in dry matter

Fresh
grass
Grass
silage
Dried
grass
Dried
lucerne
ME MJ/kgDM 12.0 11.0 11.0 9.0
FME MJ/kgDM 11.3 7.8 9.5 7.5
FME
as % of ME
92.7 70.9 86.3 83.3

Source: Energy & Protein Requirements of Ruminants, AFRC

The Metabolisable Protein rationing system demonstrates the value of high temperature Dried Grass and Dried Lucerne as balancers for farm forages rather than replacement feeds.

Vital role of fibre

The need to ensure maximum milk protein percentage within a limited quota has lead to many dairy farmers feeding high levels of starch. This can lead to an imbalance of Volatile Fatty Acids (VFAs) in the rumen which all too often results in acidosis and an increase in foot problems. One accepted way around this problem is to increase the amount of fibre included in the diet to act as a buffer.

Dried Grass and Dried Lucerne have a relatively high fibre level which, unlike straw, is highly digestible and has a beneficial effect in helping to balance rumen VFA production and to buffer high starch feeds.

The value of Dried Grass and Dried Lucerne as suppliers of fibre

Silage Barley MSBP Straw Dried
Grass
Dried
Lucerne
ME MJ/kgDM 11.0 13.3 12.5 7.0 11.0 9.0
Crude
Fibre
% 27.0 4.6 12.9 43.0 18.4 26.0
NCD % 70.0 88.7 86.0 42.0 71.0 65.0
NDF % 49.0 21.1 32.2 81.0 53.6 46.5

Along with the need for digestible fibre (NCD) to feed the rumen micro-organisms, high starch diets need a minimum level of ‘structural fibre’ or cell walls. The best measure of this is the level of NDF in the ration and a target of around 35% for dairy cows in early lactation is often suggested.

Dried Grass and Dried Lucerne, with their relatively high levels of NDF, can play an important role in achieving this balance by allowing the use of high starch diets with less risk of acidosis.

Beta-carotene and fertility

Beta-carotene is not only a vital precursor of Vitamin A, but is also required in its own right as a valuable anti-oxidant. It seems to be particularly important in fertility, where a deficiency can lead to silent oestrus, reduced progesterone secretion, delayed ovulation, poor conception rate, increased follicular and luteal cysts and reduced calf vitality.

Effect of Beta-carotene

Control Beta-carotene
Conception
rate to 1st service
40.0 68.4
Conception
rate to 1st service
55.0 69.5
Number
of inseminations
2.0 1.4
%
Luteal cysts
30.0 0.0
%
Follecular cysts
10.0 5.0

Source: Proceedings SFT, 1990

Dried Grass and Dried Lucerne are excellent sources of Beta-carotene which is particularly low in many other concentrates used for ruminants. The need for extra Beta-carotene is even greater when maize silage and other maize products are included in the diet.

Example diets

35
litre, early lactation dairy cow (kg/day)
Ration
A
Ration
B
Ration
C
Ration
D
Grass
silage
40.00 40.00 45.00 45.00
Maize
silage
10.00 10.00
Dried
Grass
2.00 2.00
Dried
Lucerne
2.00 2.00
Dairy
cake 20% protein
8.00 8.25 7.25 7.50
ME MJ/kgDM 241.00 241.00 242.00 242.00
FME MJ/kgDM 188.00 186.00 189.00 188.00
Crude
Protein
% 17.25 17.50 17.50 17.70
NDF % 41.00 40.00 38.00 37.00
Concentrate kg/l 0.29 0.30 0.35 0.36
400kg
beef animal at 1.0kg/day liveweight gain (kg/day)
Ration
A
Ration
B
Ration
C
Silage 25.00
Hay 5.50
Straw 4.00
Dried
Grass/Dried Lucerne
1.00 2.00 3.00
Barley 1.50 2.00 3.00
ME MJ/kgDM 52.00 52.00 50.00
Crude
Protein
% 16.50 14.00 11.50
Ewe
ration, two weeks pre-lambing (kg/day)
Ration
A
Ration
B
Hay 1.00 1.00
Dried
Grass
0.65
Dried
Lucerne
0.8
ME MJ/kgDM 14.00 14.00
Crude
Protein
% 13.50 14.50

British Dried Grass and Dried Lucerne are natural, high value, proven feeds suitable for all classes of ruminant. Their ability to balance modern diets and contribute significantly to rumen function and health of high performance animals can make them the final, vital piece of the jigsaw when designing a balanced diet.

Contact us today to learn more about the British Association of Green Crop Driers.

The British Association of Green Crop Driers Ltd is a company registered in England and Wales
Company Number: 751353 . VAT Registration Number GB: 210167220
Registered Office: 3 Main Street, Bishop Wilton, York, YO42 1RX