Weather Impact on 1st cut Feed Value
As we know in warm wet conditions plants generally grow quickly. These fast growing crops lay down more structural fibre to support the plant in its rapid growth. This structural fibre is the woody part of the plant which is poorly digested – reducing forage digestibility to the animal. In addition the cloud cover of wet weather reduces direct sunlight which is needed for photosynthesis to produce sugar and other fermentable nutrients. So wet weather can produce lots of silage, but potentially this forage will be of lower feed value.
In the spring of 2019 we had the opposite – cool, bright and dry conditions resulting in good photosynthesis and sugar production yet slower growth. The result is likely to be high fermentability (that sugar feeding rumen bugs) and digestibility (more of the plant available to the animal). First cut’s analysed so far show confirm this with a pattern of very high NDFd (fibre digestibility). This makes them not only physically easy for the cow to eat and quick to break down allowing her to eat more, but they also very effectively promote cudding. This is due to the fact they ferment quickly so float in the rumen mat which is where the cudding stimulation comes from.
So what difference does this make to diets? This forage will drive more milk and growth from forage. With good stocks of this type of 1st cut it may be possible to reduce concentrate fibre feeding and increase forage intake – why feed soya hulls if you have good digestible fibre on farm? The opportunity to reduce feed rates and maximise margins is there with excellent digestibility silage, which cows will naturally milk well off. This is a much better time to take concentrate feed out than with lower quality forage when the loss of yield would be counterproductive.
On the downside one issue we seem to come across more in years such as this is slipping 1st cut pits. It would appear this low lignin forage is more susceptible to these slips as the low plant structure struggles to remain in the stack, especially when it is deep. But this is only an observational theory we have not seen a definite diagnosis of the cause! Perhaps you have the answer let us know @FeedCo7.
Conditions impacting fermentation
But 2019 can’t be just about excellent 1st cuts. As well as ideal weather there have been challenging silage making conditions where moisture has got in the way! The essentials of silage fermentation are well known – get good sugar levels which in anaerobic conditions create the environment for a fast pH drop which preserves nutrients most effectively. Good sugar levels relate to two things – the sugar content and water content, because it is the concentration of sugar which determines the fermentation outcome. Low concentrations of sugar (from low sugar or wet forage) limit the sugar available to feed the preferred anaerobic bacteria which quickly drop pH to stable.
If this pH drop is not quick enough or far enough spoilage bacteria get the chance to proliferate. Significant spoilage bacteria such as clostridia break down the silage nutrients (as in compost processes). They break down protein to unpleasant smelling things like ammonia, amines and amides which are present in butyric silage. These reduce intakes and available nutrients to the animal. In good fermentations ammonia should be less than 12% of the crude protein and butyric less than 0.5% dry matter.The chances of getting high ammonia increase in wetter silage i.e. wetter silage is more at risk of poorer fermentations. This does not mean high moisture results in bad silage fermentation every time – higher moisture just makes poor fermentation a higher risk.
Summer 2019 has had lots of good weather, but also wet spells where the risk of wet crops increases. Also with crops ready early in the year there was not a lot of heat to dry the lush spring grass. In these conditions reduce the risk of poor fermentation by taking every care in silage making technique to effectively consolidate, close and seal the clamp. In addition use a proven inoculant which provides good bacteria to quickly lower the pH and so kill spoilage bacteria. Bonsilage Forte is an additive designed specifically for these conditions and will be money well spent in reducing clostridial risk and getting your nutrients well preserved – something to consider in future.
When it comes to rationing wetter forages there are potentially a few issues to balance. First is the lack of sugar and fast fermenting nutrients available to the animal and rumen bugs so lowering fermentable energy. Next is the risk of protein degradation and so a decrease in protein supply to the animal. Lastly the lactic acid level may be high, usually OK for adult stock but can make these silages unsuitable for youngstock. These are all important to address in good ration balancing to get the most from your forage if you get caught out by the weather.
Whatever your silage in 2019 we at FeedCo specialise in analysing and rationing in order to make the best use of forage – the key to ruminant nutrition.