Farm Ireland

Monday 20 November 2017

Autumn plans key to hitting targets

Dr Mary Kinston

GRASS growth is good, grazing out is tough and production is noticeably falling for many farmers over recent weeks. Where no supplements are being fed, cows have become docile, with an unwillingness to move either out of, or to, a new paddock in some situations.

While facing all these challenges, August is a critical month on the grassland management calendar as it's the time when your planning and preparation for spring should begin. Essentially, you should now resist trying to cling onto an ever-falling milk production and avoid making decisions focusing solely on the tank.

Getting the management right can be tricky as surpluses can still be emerging. In essence, there are three core aims of autumn management:

  • Provide sufficient quantity of good-quality pasture for cows in spring;
  • Promote pastures which are in good condition for rapid growth in spring;
  • Have cows which are in adequate body condition score at calving.

While these seem like distant targets, getting these essential elements right requires timely decisions during the autumn.

Do not underestimate the importance of body condition score. The sustainability of seasonal calving is reliant on a condition score of 3.25 at calving for 90pc of the herd, and is essentially determined by your drying off decisions. An adequate condition score requires good feeding and -- most importantly -- time.

The initial starting point for autumn management is to plan your feed budget around the target pasture covers required back from the magic date in spring. Factors to consider are your present pasture cover, expected growth rates, desired level of supplementary feeding, drying-off decisions (heifers, early calvers, late calvers, etc) and calving rate. The most essential aim here is to determine the pasture cover target that you must not go below when closing the grazing ground this autumn and what you need open with for spring.

After this we have to consider its implementation, as the grass plant will adapt to its particular circumstance.

During autumn, the use of slow rotations rather than fast ones (30-50 days versus 15-20) will ensure farm pasture covers are maintained at an adequate level.

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This use of rotation length is a key tool for daily grassland management. When I say rotation length, it relates to the area grazed per day, eg 1/30 is a 30-day rotation, and on 30ha, the milking platform is calculated by 30ha/30days, equal to 1ha per day. For example, if the cows (and any other stock on the milking platform) have in total grazed 9ha this week, which is 1.29ha/day, this is a 23-day rotation (30ha/1.29ha).

While using the calendar date of the number of days between grazing for a particular paddock is useful, this is retrospective of the present situation and also dependent on the growth rates of a particular paddock if using the feed wedge for grazing decisions.

While many are in the practice of building up grass and extending the rotation length in autumn, in August it is important not to build up too much grass.

The aim for most should be a rotation length of no more than 30 days for September 1, with appropriate pre-grazing and residual pasture covers. In August, with a vegetative ryegrass plant, the aim is to promote the sward to tiller, which will maximise the number of tillers, ie grass plants, available to grow this autumn and spring. If the length of rotation becomes too prolonged too soon, the pasture will become tall and heavy and the lower leaves will be shaded, causing them to die and decay, and reduce the number and vigour of new tillers. Also, swards with a high mass (> 2,000kg DM/ha available) at this time will generally contain a higher proportion of dead material, which is poorly digested.

It's also important that pastures are grazed intensively at least once this autumn, again to remove dead material and stimulate the growth of ryegrass tillers and suppress undesirable species. Letting pasture covers get too heavy will not make this task easy.

As we move into September and through to November, rotation length should be extended further, ie 40-50 days, in line with the decline in grass growth rates.

In essence, good grass management is far from easy, and is an art of successful compromise between several conflicting requirements of the pastures and the animals, especially in the autumn. However, it's an inherent part of a profitable dairy unit and one skill that must be mastered.

Irish Independent