Pre (3400KgDM) and Post (1400KgDM) Grazing heights in paddock 4
Grazing conditions have been excellent for the last 4 days. Cold winds have dried the farm, allowing cows to graze paddocks very well. Judging by the post grazing height, almost too well.
The two most important grazing rounds are the first and the last. In the first we try and graze out all the old winter growth, and the earlier we do this the better. Over winter grass enters a dormant phase where growth slows to a minimum, grass drymatter will increase, but overall herbage mass is static. Defoliation wakes the plant from this state and kick starts growth. Low residuals in the first round are particularly important, as any dead-matter in the sward is removed, maximising future growth and quality for subsequent rounds. If ever there was a time to treat cows a little meaner and graze harder, now is that time.
The exception to this rule is the above scenario, where residuals are under 1500KgDM. Here supplementing your grass with concentrates (or whatever you have locally) will have a high milk response and higher profitability than the decision to feed at other times. This is because:
1.) Cows grazing below 1500KgDM are telling you they are close to being underfed, they are close to their physical limit of grass utilisation. It stands to reason then, that feeding them more of a high quality feed will suddenly provide them with a higher net energy(ME) intake, and increase milk production.
2.) Lifting residuals to above 1500KgDM will result in faster regrowth as the grass is left with a higher reserve of sugars, from which to grow.
So this weeks grazing decision is obviously to supplement the grazing. Cows are being fed 4Kg of a 13ME, 14% Protein concentrate, along with roughly 1KgDM of average quality silage (10.5ME).
In a future post I'll discus energy intakes for grazing cattle, and how to think of grass purely as an energy source!