Farm Ireland
Independent.ie

Sunday 19 November 2017

It will pay to prioritise grass management

Dairy

Mary Kinston

For many of you, the silage is cut and the aftergrass is growing -- and whether it's available now or over the next couple of weeks, it has potential to come back into the milking cows grazing rotation.

Where your weekly pasture cover has been under pressure because of high stocking rates, dry conditions or poor growth, the sight of the clean growing aftergrass can be a welcome relief. However, where stocking rates are low on the milking platform and silage has constantly been removed, or where grass growth has consistently matched your grass demand without the silage ground, the return of the silage ground can rock the boat of managing grass quantity and quality. Therefore, summer grass management relies on regular measurement and a degree of risk analysis, with appropriate surplus management strategies.

Measuring your grass cover weekly, and using the feed wedge to identify and manage grass surpluses, are essential tools at this time of year in order to maximise milk protein, minimise the fall in milk yield and aid good conception rates by maintaining the quality of the milking cow's diet.

Essentially, surplus management is about minimising the amount of grass stem and maximising grass leaf in the diet. The grass feed wedge is reliant on calculating your pre-grazing cover as defined below, with a cover greater than this amount representing a surplus above the herd's feed demand.

Target pre-grazing cover = (stocking rate x intake of pasture x rotation length) + residual cover, eg, three cows/ha x 18kg DM grass/cow x 21days + 100kg DM/ha = 1,234kgDM/ha.

Mid-summer grass management can be challenging as grass growth rates in July are generally up around 40-60kg DM/ha/day, but high growth rates of up to 70-80kgDM/ ha/day can still occur. So while silage aftermaths are great for supplying good quality pasture, they can be challenging, as they further reduce pasture demand and promote the likelihood of grass surpluses.

Mid-summer grass surpluses are less guaranteed than in late spring and early summer as the removal of the seed head makes grass growth more reliant on the vegetative tiller, which has less vigour than the reproductive tiller pre-seed head emergence.

So the method and the length of closure of your present surplus has to be given due consideration to minimise the risk to your future grass supply. For example, surpluses and pasture quality can be managed by closing for pit silage (second-cut/long-term silage) or bales (usually short-term silage), for hay, spraying-off and re-seeding, topping or pre-mowing.

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From these options, pit silage/second cut, regrassing and haymaking pose the greatest risk to grass supply as the period of closure can be as long as two months before the milking cow can return for grazing. Where these strategies are used, grass demand (stocking rate cows/ha x kilogrammes of grass/cow/day) must coincide with your average estimates of you future pasture growth rates for the closure period over the coming months. Referring to previous years, pasture growth data can be useful for this.

Where grass demand is close to estimated growth rate, short-term methods, such as cutting light surpluses for round bales, topping or pre-mowing, are more appropriate strategies. This way you restore pasture quality, the immediate surplus is removed and the paddock quickly re-enters the grazing rotation.

The drawbacks of short-term surplus strategies are that they tend to be more expensive as only a small amount may be harvested. In addition, they need to be repeated more often and some would argue that topping or pre-mowing just wastes time and diesel.

However, the bales harvested are generally excellent quality that can be a great supplement for feed pinches in late or early lactation. Maximising grass quality will also ultimately benefit the cow in terms of performance, rather than letting it rot away or making her eventually consume what she has already rejected.

Surpluses arise because growth exceeds demand, so if you are feeding meal, reducing the amount fed can be a cost-effective strategy especially if you are potentially going over quota.

Lowering meal feeding increases your grass demand and reduces potential surpluses, but, if removed, this meal needs to be replaced by high-quality leafy pasture, so getting your grass management skills up to speed is essential.

Mary Kinston is a Kerry-based farm consultant. Email: mary.kinston@gmail.com

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