Beef and sheep notes May 2009

The month of May is normally the most vigorous period of the year for grass growth. Management decisions made at this time will have an impact on both the quantity, and, more importantly, the quality of grass grown for the remainder of the grazing season. This in turn will have a major influence on the performance of grazing stock.

High quality leafy grass has a feeding value of about 85 – 90 percent that of concentrate ration and therefore has the potential to produce cattle liveweight gains of around 1.2kgs/day at a fraction of the cost of meal feeding.

On rotational grazing systems, aim to have stock entering each paddock/field at a grass height of 10-15 cm (4-6 inches) and graze down to 4 to 5 cm (2 inches or less) where possible. Six to eight divisions within the rotational system and 18 to 21 day grazing intervals, means that stock can be encouraged to graze fairly tightly without comprising performance to any great extent. With fresh, green sward residuals, re-growth takes place almost as soon as the stock leave the field.   

If the production of seed heads and un-eaten tufts of grass become a problem, then top down to a maximum height of 5 cm (2 inches) and preferably down to 3.5 cm (1.5 inches) if possible.  Early (and low) topping i.e. late-May to mid-June encourages tillering within the sward and sets it up to produce plenty of leaf for the remainder of the season.

Weekly assessment of the grass supply/demand balance is the key to the successful operation of the grazing management system outlined above.

A relatively simple way of assessing grass supply is to use the “Grazing Days Ahead” method.  This can be used to quantify the amount of grass on the farm at any one point in time in terms of estimating how many days grazing is available for each batch of stock.

Simply walk across all the fields/paddocks available for grazing with a pen and notebook and estimate how many days grazing are in each division while not taking into account any future growth.

There will be no days in the field just grazed, perhaps 1 day in a field/paddock grazed a week ago, 3 days in the next shift and so on.  The sum of the grazing days in each paddock gives you the Grazing Days Ahead. For the months of May and June plan on having 12 to 15 grazing days ahead of stock.  

Grass silage is still the main conserved forage for beef cattle but there must be serious focus on conserving quality material. Last winters meal costs reinforced the point. The feeding value of grass silage is determined by its digestibility and intake potential. The simple message for beef farmers is: ‘if you want high levels of performance from silage you must cut early and forget about bulk.’

Research work at AFBI Hillsborough has continually shown the importance of harvest date in making high quality silage. This is the most important factor affecting digestibility. For each week harvesting is delayed the digestibility falls by 2 - 3 units of D-value. Improving silage quality in terms of ‘D-value’ by 5 units increases carcase gain by 0.14kg/day. Over a 150 day winter feeding period this means an extra 21kgs of carcase or £57 (at £2.70/kg), which could mean the difference between profit or loss.

Well managed swards can produce liveweight gains of 1.2kg/day

Sward height is a good indicator of the supply and suitability of grass for grazing. During May, if set – stocking a height of about 6 – 7cms is the target when the grass is leafy, while paddocks should be grazed down to about 4 to 5cms. If grass is too high in May (8-9cms) it becomes stemmy in June and results in reduced lamb growth rate.

Allowing the lambs to creep graze ahead of the ewes giving them access to the best quality grass is well worthwhile if you have a suitable layout. It can increase weaning weight by about 2 kg.

Watch out for the first wave of infection from nematodirus, delayed this year due to the cold spring. This infection causes severe scouring, affects only lambs and is passed from one year’s lambs’ crop to the next if they are grazing the same fields as the previous spring. White or clear drenches should be used.

Graze paddocks down to 4 - 5 cm