Silage variability prompts energy protein balance concerns

Concerns over the balancing of dairy cow rations are growing as many first cut silage analysis results contain higher energy than protein.

Challenges with low silage protein levels were first flagged in early first cut silage analysis results. However, as later first cuts join the mix, the picture is becoming more extreme. This translates into an even lower average crude protein levels and potentially a negative protein/energy balance in the rumen.
Analysis of 163 silages by Mole Valley Feed Solutions - including some later cuts taken in late May-early June, show average crude proteins are now 13%. This is down from around 14.5% for early first cuts. The range is also marked; running from 8.2% to 21.6% crude protein.

The fermentable energy and protein balance (NFEPB) is of particular concern. Normally, you’d expect crude protein levels to be higher than metabolisable energy at about 14-16% CP and 11 MJ kg DM. However, this season, it’s been reversed and some silages are analysing at 10% CP and 11 MJ kg DM. The picture becomes more extreme as more first cut silage analysis results come in. Left unaddressed, this could negatively impact milk output.

The average NFEPB ratio is now negative, when you’d expect it to be positive. Such a pattern is virtually unheard of and could be linked to the very cold, dry spring. It suggests applied fertiliser wasn’t taken up, so the plant didn’t produce as much protein.
Farmers that cut very early appear to have been impacted less. However, those that planned to cut in the second or third week of May and then had to delay due to the weather and cut in late May-early June seem to be most affected.

The issue is not just with crude protein, but how that protein is made up. Rumen fermentable protein (RFP) and total fermentable protein (TFP) levels are particularly low, which raises a red flag over rumen function. RFP and TFP are needed to promote rumen function, maximise nitrogen efficiencies and optimise production of microbial protein.

Feeding rumen fermentable protein sources, such as rapeseed, could help address the protein and energy imbalance and protect milk production. Carefully rationed feed grade urea could also be a cost effective option.

Cutting date has also impacted silage dry matters, with early cuts tending to be lower in fibre, wetter and more acidic, whilst later first cuts are testing higher in fibre, drier and more alkaline. This will create different ration balance requirements depending on what’s being fed and could mean one farm could need two completely different diets, depending on which silages they’re feeding.

For example, wetter, more acidic silages will need to be balanced with by-pass starch to prevent acidosis. Providing digestible fibre by including sugar beet in the cake could also help. Cows will also need to eat more of these wetter forages to deliver target dry matter intakes. In comparison, drier silages may need balancing with fermentable energy, such as rolled wheat.

Ultimately, farmers will only know where they stand by analysing forages. Don’t work off averages; the devil is in the detail, so analysing silages is an absolute must this season to protect rumen function and milk production.

For more information on ration balance and boosting MOPF, please call the
Feed and Nutritionists Line on 01278 444829 or email [email protected]

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