Video: Top tips to make the best use of spring grass

Making the most of grazed grass is critical for any profitable dairy enterprise. When weather conditions allow, farmers will be focusing on turnout and trying to get cows out grazing by day. Herds will be out full time as soon as weather, ground conditions, and grass supply allow.

James Ambrose, technical manager UK & Ireland for Phileo Lesaffre Animal Care provides some top tips to make the best use of spring grazing.

Gradual turnout

Turning cows out to grass creates a big change in diet, as well as imposing a stress event on the cow. It takes around three weeks for the bugs in the rumen to adapt to this. So, it is important to manage the transition to grazing gradually to avoid digestive upsets and loss of performance.

Even a few hours of on-off grazing by day, when weather conditions allow, will mean that the rumen bugs can adapt to fresh grass. Cows should be able to consume 5kg of dry matter (DM) in approximately three hours in suitable sward and weather conditions.

Dry matter intakes

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

It is important that the DM intake of a cow is not overestimated at grazing, as 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 250g/kg DM – particularly after fertiliser application – and this is mainly rumen degradable protein (RDP).

Rumen microbes are unable to utilise this much protein from high grass intakes – particularly if there is a shortage of fermentable energy available to them. Excess RDP is broken down into ammonia in the rumen, absorbed into the blood stream and converted to urea in the liver.

Elevated blood urea nitrogen levels (BUN) – from excessive crude protein in the diet – can increase body condition score loss, reduce fertility and impact on hoof health.

Buffer feeding

It is important to supplement cows with forages with a high energy content and digestibility to maximise DM intake during the transition to grazing, when grass is gradually being built up in the diet.

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 DM intake, which is critical in early lactation.

James Ambrose, Technical Manager UK & Ireland for Phileo Lesaffre Animal Care has some top tips for turnout to grass in the video below.

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, which further compromises 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 sugar levels are great for rumen fermentation, promoting good milk proteins and strong yield. But, when supplied in excess and in combination with low-structural fibre, they can challenge rumen function and lead to acute or sub-acute rumen acidosis (SARA).

Consequently, butterfat and milk protein percentages can be affected, as a result of the change in rumen fermentation. Prolonged challenges can impact on fertility.

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

Compound feeding

It is important that compound feed, fed through the parlour, tops up the DM that grass and forages do not supply. This ensures that energy requirements are matched for a given yield.

It is also important that the nutrient content of the compound feed balances that of the grass to optimise rumen fermentation and maximise performance.

Farmers should 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 – magnesium, for example.

Monitor what the cows are telling you

Assess rumen fill two to three hours after milking to determine whether adequate grass has been allocated; monitor cudding rate – you are looking for more than 65% of the herd to be lying down chewing the cud two to three 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 condition: Cows losing excessive body condition can point to insufficient feed intake, a possible metabolic disorder, health issue 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 this falls within the optimum range of circa 1.2:1.

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 per cow per day in early lactation. Click here for more information on Actisaf