One of the skills of spring grazing management is to feed the cows as much as they can eat to achieve their peak potential milk production, while at the same time preventing the development of stalky, rank herbage in the pasture for the next grazing.
If pastures are allowed to become stalky, feed quality will decrease so that in late spring and early summer, the herd's milk production will fall, even though there appears to be plenty of pasture. A rapid fall from peak production is usually a good indication that there has been poor pasture control. Many trials have demonstrated that production is affected right through into the summer period if target post-grazing residuals are not achieved through the period of spring surplus.
Crucial to this aspect of pasture management is the early recognition of a developing pasture surplus and a plan to deal with it. Failure to react quickly leads to deterioration in the pasture sward as well as a reduced ability to convert the surplus into quality pasture silage.
The "3-leaf principle" can be used as the basis for this assessment by establishing the ideal rotation speed - that is, the area to be grazed each day. Once this area is being grazed, supplement feeding levels can be adjusted or removed entirely from the ration, to ensure that the target 1500kg DM/ha post-grazing residual is achieved. Graphing the shape of the pasture wedge and/or the use of various feed budgeting programmes can assist this process.
For quality silage to be made, aim for a maximum period of closure of 5-6 weeks from the last grazing as the protein and energy levels will fall steadily from this point. The Golden Rule is that if it is not suitable to feed to a milking cow before conservation, then it will certainly not be suitable after conservation!