Making the most of grazed grass is critical for any profitable dairy enterprise. With the generous spring weather so far this year, farmers will already have cows out grazing by day and will get them out full time as soon as grass supply and conditions allow.

However, there are a few things farmers can do to ensure that their herd’s health and performance are maintained during this time.

James Ambrose, Technical Manager UK & Ireland for Phileo Lesaffre Animal Care, provides some advice below for managing the transition period.

Gradual turnout

It takes around three weeks for the bugs in the rumen to adapt to diet change, so it is important to manage the transition to grazing gradually in order to avoid digestive upsets and loss of performance.

A few hours of on/off grazing by day will mean that the rumen bugs can adapt to fresh grass. Cows should be able to consume 5kg dry matter (DM) in approximately three hours in suitable swards and weather conditions.

Dry matter intakes

The moisture content of grass can vary significantly in spring, and this can have a major impact on dry matter intakes. At 15% DM, a cow estimated to consume 15kg of grass dry matter needs to eat 100kg of fresh grass.

Do not overestimate the dry matter intake a cow can get from grazing, or their body condition score, performance and fertility will be compromised.

Excess crude protein

Lush, leafy spring grass can often have a crude protein content in excess of 250kg DM, particularly after fertiliser application, and this is mainly rumen degradable protein (RDP).

Excessive CP in the diet will result in elevated blood urea nitrogen levels (BUN), potentially causing loss of body condition, reduced fertility, and declines in hoof health.

Buffer feeding

It is important to supplement cows with forages with a high energy content and digestibility to maximise dry matter intake during the transition to grass.

Starch-based forages, such as maize silage, are a great combination with grass, as the use of nitrogen in the rumen is enhanced and microbial protein synthesis is increased due to the fermentable energy being supplied by the maize starch.

High DMD grass silage (>28% DM) is also highly effective. This will help to maintain milk constituents and protein, in particular, as well as ensuring sufficient dry matter intake, which is critical in early lactation.

Highly digestible grass swards can challenge rumen function

Lush spring grass tends to have a high proportion of leaf-to-stem, resulting in low structural fibre levels in the overall diet. This lack of ‘scratch factor’ can impact on cudding rates and saliva production, further compromising rumen function.

While the nutrient analysis of grass can vary wildly, this lack of structural fibre can be accompanied by high sugar levels – often more than 18% during sunny, dry weather. High proportions of sugar and low structural fibre can challenge rumen function, leading to sub-acute rumen acidosis (SARA).

Consequently, butterfat % and milk protein % can be compromised as a result of the change in rumen fermentation, whilst prolonged challenges can impact on fertility.

High levels of unsaturated fatty acids in spring grass can also cause butterfat % to be reduced, so lower butterfat doesn’t always mean SARA is a problem, however.

Compound feeding

Ensure that compound feed, fed through the parlour, complements the nutrient content dry matter in your grass.

Aim for a feed that has around 14-16% crude protein, a highly digestible fibre content (such as sugar beet pulp and soya hulls), a balanced source of cereals including maize and barley and a source of bypass protein. It should also contain minerals that grass is deficient in like magnesium, for example.

Look at your cow signals

Assess rumen fill 2-3 hours after milking to determine whether adequate grass has been allocated to monitor cudding rate – look for more than 65% of the herd to be lying down, chewing the cud 2-3 hours after milking.

Check dung consistency – loose, bubbly dung with undigested fibre in it is indicative of poor rumen function (as is the presence of cud balls in collecting yards or cubicles).

Monitor body condition – cows losing excessive body condition can point to insufficient feed intake, a possible metabolic disorder, health issues or sub-optimal rumen function.

Milk quality

Monitor bulk tank milk collections for average yields and constituents. A fall in butterfat or protein of 0.3% or greater in one week is a warning sign for poor rumen function and the occurrence of SARA.

It is also useful to keep an eye on the butterfat-to-protein ratio to ensure that it is around the optimum ratio of 1.2:1.0.

Feed Actisaf live yeast

Adding Actisaf live yeast to your cows’ ration will reduce setbacks in performance at turnout by helping the rumen bugs adjust to grazed grass faster and more effectively, thereby improving rumen function.

Actisaf also reduces the risk of SARA, both at turnout and throughout the grazing period. Actisaf helps to stabilise rumen function and promotes milk solids and milk yield.

It should be included at a recommended rate of 1kg/t of grazing compound, assuming a feed rate of 6-8kg compound/cow/day in early lactation, and depending on circumstances can provide a return of up to nine times initial investment.

Further information

Taking a proactive approach to grazing transition management can mean substantial differences in revenue for your business.

For additional advice on how to manage this important period, visit our website at:

Or simply click here