Many grass silage crops have analysed at less than 11 MJ ME/kg DM, which is significant once you consider that the difference between 10.5 ME silage and 11.5 ME silage, (assuming a feed rate of 11 kg DM of silage/ day) will be equivalent to 2.2 litres milk/cow/day. What’s more, many grass silages this year are stemmy, with high fibre levels impacting digestibility.
Not only will forage quality be a challenge for many dairy herds but preserved forages are also highly variable, something that is almost impossible to avoid but can have a big impact on rumen function and performance.
Forage variability is inevitable
With different fields having different grass mixes and grass maturity, it’s inevitable that there will be some variability even within a single cut in the clamp. Some fields may even have been subjected to different weather through the harvest process. Some farmers then store more than one cut within the same clamp, adding to range within each grab-full at feeding time. Add to this the spectrum of different forages fed (e.g. maize and whole crop), and the variability within those forages, and the reality is that the nutritional variation within the forage part of a dairy ration is potentially massive every day.
To add to the challenge, many farms also feed by-products from the brewing, bakery and confectionery industries and these can add further variability due to differences in raw materials. What is clear, then, is that it is actually quite hard to feed the same ration every day and yet we know that consistency is king for optimal digestion and rumen fermentation – helping to maintain high feed intakes, minimise digestive upsets and improve milk yields.
Why does variability matter?
Inconsistency in forage has a significant impact on the nutritional composition of the ration presented to cows each day. It is important to remember that when we feed a ruminant we are really feeding the bugs within the rumen, which in turn feed the cows. Whilst only around 20 per cent of the bacterial population of the rumen has been classified to date, what trials have shown is that different categories of bugs flourish depending on the diet composition being fed and that these bacterial populations take time to adapt to a new diet – typically up to three weeks.
If the forage being presented to the cows is highly variable, then the rumen population has to change frequently to make the most of the forage being fed - and with this taking up to 3 weeks, how can we expect to see optimal performance on a daily basis.
What can you do to maximise performance from forage this winter?
There are some simple practical things that can be done to help maximise performance this winter:
Sample forages regularly One thing that can make a real difference is regular forage sampling. Gaining a better understanding of the quality and makeup of forage stores can help you deliver as consistent a feed ration as possible. While a silage core sample will usually be taken by a nutritionist at the start of the winter, it is important to analyse clamp faces at least once a month and ensure that samples taken are representative of forage across the whole clamp face.
This will enable you to identify any variation in forage quality and make necessary adjustments to feed rations to maintain consistency.
Already this year we have seen analyses of silage within the same clamp varying hugely in samples taken just a few weeks apart (see table below).
Manage feed delivery
Ensure that you are presenting mixed rations in the most consistent way. Do not overload feeder wagons and ensure that the wagon is loaded in the correct order (smallest first) and mixed for the same amount of time each day to ensure mix consistency.
Structural fibre, such as straw, must be adequately chopped (to the width of a cow’s muzzle) to reduce sorting and feed must be distributed evenly against the feed barrier to encourage intakes.
Feed Actisaf live yeast
Feeding Actisaf live yeast can deliver real benefits when you are facing highly variable forage in the winter, particularly if that silage has high fibre levels.
Trials have shown that Actisaf reduces the bacterial diversity in the rumen and promotes the growth of beneficial bacteria, as well as stabilising rumen bacterial populations during diet changes. What this means is that it allows for faster adjustment to new diet composition or diet ingredients and minimises any losses in production that would otherwise occur.
Specifically, we see an increase in lactate-utilising bacteria, which reduces lactic acid and helps stabilise pH in the rumen, as well as an increase in fibrolytic bacteria, which helps fibre digestion. Indeed, Marden et al., 2008 demonstrated that neutral detergent fibre (NDF, which is the most common measure of fibre and represents most cell structure in forage including lignin, cellulose and hemicellulose) digestibility was greater when diets were supplemented with 5g/day of Actisaf live yeast (41.6% NDF digested) compared to a control diet (29.6%) or a diet where sodium bicarbonate was fed as a rumen buffer (34.3%). Similarly, acid detergent fibre (ADF, which represents the least digestible fibre portion) digestibility was greatest in a diet supplemented with Actisaf (32.3% digestibility), intermediate in a diet buffered by sodium bicarbonate alone (24.4%) and lowest in a control diet (18.1%).
Through its mode of action, Actisaf offers many advantages through the winter feeding period, particularly when forages are likely to be stemmier and more fibrous as they are this year for many farmers, as it stabilises rumen function, which helps the cow cope with variation in forages, and facilitates better fibre digestion, helping drive milk from forage despite higher fibre levels.
Table 1: Grass silage analysis - 2016 first cut - all taken from single clamp on the same farm. Some dates include two samples to demonstrate variation on the same day in different parts of the clamp.
|
Date |
DM % |
ME MJ/kg |
D Value % |
CP % |
NDF % |
pH |
Sugars % |
Ash % |
VFAs g/kg |
Lactic acid g/kg |
|
07/06/16 |
24 |
10.2 |
63.8 |
11.4 |
50.8 |
3.7 |
1.2 |
7.6 |
0.3 |
66.6 |
|
21/06/16 |
24.2 |
10.4 |
64.9 |
11.6 |
49.2 |
3.7 |
0.7 |
7.7 |
0.3 |
91.3 |
|
08/07/16 |
23.6 |
11.2 |
69.7 |
14.3 |
48.5 |
3.5 |
0.2 |
7.7 |
13 |
104.5 |
|
08/07/16 |
24.7 |
10.5 |
65.9 |
11.5 |
47.7 |
3.7 |
0.4 |
8 |
7.3 |
99 |
|
02/08/16 |
25.7 |
10.8 |
67.6 |
12.6 |
48.9 |
3.7 |
0.6 |
7.4 |
34.4 |
100.8 |
|
02/08/16 |
26.5 |
9.9 |
61.7 |
12.1 |
46.7 |
3.7 |
0.9 |
7.9 |
18.8 |
98.5 |
|
02/09/16 |
23.7 |
11.8 |
74 |
16.9 |
43.8 |
3.7 |
0.5 |
7.9 |
24.2 |
127.9 |
|
05/10/16 |
38.9 |
12.1 |
75.8 |
17.1 |
40.7 |
4.2 |
4.2 |
9 |
15.8 |
59.2 |
Summary
This year, winter feeding presents a challenge in terms of forage variability and quality, with many farmers having grass silage with high fibre levels and low ME. You can reduce the impact of these issues by:
- Regularly sampling forage through the winter, so that diet formulation can be adapted to ensure consistency
- Focusing on feed presentation and mixing
- Adding Actisaf live yeast to your ration to improve fibre digestion and rumen stability, increasing milk from forage and overall performance.