Dairy notes September 2008

I hope the recent improvement in grazing conditions is not a short-term feature and conditions will allow you to take advantage of the good grass growth. On good quality September grazing, a cow is capable of producing 15 litres of milk without being fed concentrates. Ideally swards should be grazed off at a cover of 3,300-3,500 KGs DM/ha (a sward height of 16-18 cm).  Silage aftermaths, which are cleaner at the base, can be successfully grazed at a slightly heavier cover of 3,800-4,000 KGs DM/ha.  

Unfortunately with the poor ground conditions in mid to late August restricting grazing, covers on many farms have built up to higher levels. Grass quality is deteriorating, so it is essential that the build up of stemmy and rejected grass is cleaned out of paddocks as soon as possible to ensure a supply of good quality grass for the rest of the season. If covers are reaching 4,300-4,500 KGs DM/ha, graze the sward lightly with the milking herd and use dry cows or young-stock as a follower group to clean off the rest. If fodder supplies for this winter are still an issue, some of the grazing area carrying heavier covers (5,000+ KGs DM/ha) could be closed off for big bale silage.

A considerable area of grassland was reseeded in late July/early August. The warm, damp conditions allowed the grass to germinate and establish rapidly.  If ground conditions allow, the young sward should be grazed when the seedlings are 10cm high – approximately six weeks after sowing. Early grazing will encourage the new grass to tiller and crowd out weed seedlings.  Calves, light cattle or sheep should be used for the grazing as they are less likely to poach the relatively soft soil surface.  Keep grazing the reseeds on a rotational basis to ensure high covers are not carried into the winter as these swards would be more prone to frost damage. This damage would create bare patches which allow weeds to establish rapidly in spring.

The warm moist conditions also encouraged the germination of a lot of weed seeds. These weeds need to be controlled at an early stage or they will reduce tillering of the new grass. Annual tall growing weeds such as redshank, charlock and hemp-nettle can be controlled by the early grazing or topping. Chickweed and docks may need to be sprayed. Chemicals for weed control should be applied as soon as the grass and clover seedlings have reached the herbicide tolerant stage as weeds become more difficult to control as they mature. Only a very limited number of clover safe chemicals are available for use in reseeds – for chickweed, Alistell can be used but where docks are a problem use Squire.

Are you monitoring the condition of heifers calving over the next three months? Target condition score at calving is 3. A heifer calving down in a fit condition has greater appetite and looses less condition than a fat heifer (condition score 4-5), which has a significant benefit for future fertility.

It is more important to control body condition than to put on extra body-weight.  

Over the last two months before calving, heifer growth rate should be no more than 0.5 KGs/day. For grazing heifers this means limiting grass intake by grazing bare pasture. They could be used to clean off swards behind the dairy herd.

Heifers should be fed dry cow minerals for at least six weeks before calving.  To reduce the stress of early lactation, introduce heifers to the milking system two to three weeks before calving. At Greenmount Campus, the springing heifers are brought into the parlour and fed a small amount of the early lactation ration.