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This is a critical week for managing grass – get it wrong, and it will adversely affect milk performance for the rest of the year, get it right and milk yield and protein will be up. These are the steps involved in making sure you come out on top in the battle to control grass quality.
You can’t manage without measuring.
Even if you don’t put a figure on how much grass is on every paddock, the act of walking each field and assessing the grass available will help to inform decisions. Of course, the best farmers at managing grass do a proper grass cover every five or six days at this time of year. There are two vital bits of information from measuring grass – average farm cover (which is the average cover in every paddock available for grazing, divided by hectares or cows) and the growth rate. You won’t know these unless you actually measure the grass.
That said, many farmers will walk their farm regularly without actually measuring and still make good decisions but they are banking on their knowledge and experience when making these decisions. Having accurate measurements will help to make more informed decisions.
Armed with growth rate and what the average farm cover is, the next job is to act on the results. Many farmers will measure grass but don’t have the ability or confidence to make decisions afterwards. Some say the difference between a good farmer and an average farmer is the space of a week, whereby the good farmer will make decisions a week earlier than the average farmer. At this stage in the year, I would look at average farm cover per cow more than average farm cover per hectare. On a per-cow basis, I would like to see it between 150kg DM and 180kg DM. If grass is growing fast, then I would be happy to go below 150kg per cow for a short period. I would be happier doing this than going above 180kg per cow when grass is growing quickly, as covers will get too high too quickly.
The growth rate is determined by the average increase in grass on each paddock divided by the number of days between measurements. There comes a time in April when growth rate will more or less double overnight. When this happens depends on the weather. For some farmers, this big burst in growth has already come, while it is still on the way for others. The trick is to be prepared for it when it does come.
The big risk when growth rate increases dramatically is that pre-grazing yields get too high and grass goes to stem.
Demand should be set close to the actual growth rate or predicted growth rate. Demand is influenced by stocking rate and supplement fed. Increase demand by either taking out paddocks for silage or reseeding and/or reducing or removing supplement. Be careful not to set demand too high.
While growth rates might hit 100kg/day for a week or two, you need to look at it over a longer term. Average growth rates in late April and May are usually between 70kg and 80kg/day. Setting demand higher than this by closing up all the surplus for first cut is a poor decision as it risks a grass shortage when growth slows in late May and the silage is yet to be cut.
Setting a demand much lower than the average growth rate means that the farm will constantly be in a grass surplus. A demand of 70kg is setting a stocking rate of 4.12 cows/ha presuming a grass allowance of 17kg/cow/day.
Stocking rate multiplied by grass allowance per cow multiplied by rotation length in days gives the target pre-grazing yield. If stocking rate or demand is very high, then you need to be grazing higher covers to get to a 20- or a 21-day round length.
An ideal target pre-grazing yield at this time of year is 1,400kg, which is sufficient to maintain cows stocked at four per hectare on a 21-day round length. But farms stocked at 4.6 cows/ha need to be grazing covers of 1,650kg, which is too strong as there is a lower leaf to stem ratio at higher covers.
The best policy is to set long-term demand close to the average growth rate until the silage ground is back in the rotation. This will vary from 60kg to 80kg/day depending on farm aspect, weather, soil type and grass varieties. When surpluses emerge, they should be removed as short-term silage. So while the demand will temporarily increase when these surplus paddocks are out, it will drop again when they are cut.
Many farmers put these surpluses into high-quality bales and will feed them out again to milking cows in autumn and spring.
The higher the demand the greater the urgency to get these surpluses cut and back growing. The grass wedge on grass management computer programmes will help to easily identify grass surpluses.
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