NUTRITION ▶▶▶
Mixing grass seeds for maximum forage intake
Dairy farmers know very well that fresh grass is the cheapest form of feed needed for their cows to produce quality milk at a profit. However, cows can be quite fussy eaters, and farmers need to ensure they make the right choices when picking grass seed varieties and mixes.
BY CHRIS MCCULLOUGH I
Seeding can be carried out in spring or autumn.
n order to maintain good quality grass in the fields, farm- ers generally need to reseed 10–15% of their land each year. It can cost around € 500 to € 900 to reseed one hec- tare of grassland so it is vital that the right choices are
made to suit the growing conditions and soil type. Establishing a new ley has the benefits of improving the grass yield, quality and disease resistance and also means it can last five to ten years over an existing sward. Naturally, over time these benefits gradually decline depend- ing on the soil health, nutrition, weed control and general grassland management practised on the farm each year. Seeding can be carried out in spring or autumn. While both these periods have their own advantages and disadvantages, the main decision on when to seed should be taken after analysing soil samples from the desired field.
The right grass variety Cows can be picky eaters indeed and often prefer some fields over others. This taste preference can be boiled down to the grass variety used to seed the field.
Cows often like to show their dissatisfaction with grass if they don’t like it by becoming unsettled and roaring most of the day. If they don’t eat the grass it is left and the field is poorly grazed, which is a waste of money. This poor graze-out increases the proportion of stem in the sward at the next grazing, which is less digestible than leaf and can cause a drop in milk production. Choosing the cor- rect grass variety is crucial to ensure reseeding costs are well spent and that the grazing efficiency is maximised. Most re- seeds are probably a mixture of diploid and tetraploid peren- nial ryegrasses. However, other types of ryegrass and species such as clover, cocksfoot and timothy may have a role to play in certain situations. Each type of grass has different growth and quality characteristics, so when reseeding it is important to select the most appropriate species for the situation.
Testing grass varieties During a trial at Teagasc Moorepark in the Republic of Ireland a number of grass varieties were tested to investigate their graze-out potential. In total, 30 perennial ryegrass varieties from the DAFM Rec- ommended List were sown in 36m2
plots and rotationally
grazed from February to November on 11 occasions. On aver- age the trial grew 15t of dry matter (DM) per hectare over the year. Before grazing, the yield and height were measured and samples collected for digestibility. The after-grazing heights were measured with a rising plate meter as the measure of graze-out, so swards with lower post-grazing heights had greater levels of utilisation. During the tests, varieties with larger pre-grazing heights were found to have poorer graze- out and from this a new characteristic of grazing quality called the Residual Grazed Height (RGH) was calculated. The results showed that tetraploid varieties were among those grazed-out the most, with diploids generally yielding well but not grazing-out tightly. The majority of tetraploids had better graze-out performance than diploids even when DM production was similar between both ploidies.
Mixing grass seed varieties Using a mix of grass seed varieties has a number of benefits for both the farmer and the sward. These include risk management because using a mix mini- mises the risk of a crop of seed failing. A mix also ensures
16 ▶ DAIRY GLOBAL | Volume 8, No. 1, 2021
PHOTO: CHRIS MCCULLOUGH
PHOTO: CHRIS MCCULLOUGH
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