Can we have too much grass for calving?

Can we have too much grass for calving?
By Katrina Roberts, Herd Health Veterinarian, Anexa Vet Services

Famine to feast, bust to boom – these are the words that spring to mind to describe how average pasture cover (APC) on farm has changed in the last 3 months. An APC of above 2500kg/ha is not unusual for our clients now, and although you would think you can never have too much grass, you do need to be ready to manage it and not waste it, as wasting it now will create quality issues later on.

Entry covers of >4000kgDM for the dry cows mean that on your normal dry cow pasture allocation of 35m2 you are now offering your dry cows 10-11kgDM on all grass, or 120-130ME per cow per day. So for the majority of cows you should be able to be pasture only for the dry cows. However, if your normal farm policy is for the springing cows to get some supplement (in order to distribute minerals better), then you don’t want to be on 35m2 and giving them 3kgDM maize as you will be overfeeding the springing cows. Overfeeding springing cows is a waste of feed and if you have done a great job of getting your calving cows into target BCS (5- 5.5) then overfeeding them as springers will increase the risk of milk fever and ketosis.

It means you may need to rethink your supplements for the dry cows i.e. a low ME feed such as hay may be a good way of reducing the energy density of the diet for the springing mob. Alternatively you could reduce their area. This is an okay option for smaller cows when it’s dry, but of course Friesian cows on less than 30m2 will waste a lot of pasture i.e. the density of cows/area is just too high, and on wet days the utilisation will plummet on these smaller areas, leading to a greater reduction in dry matter intake (DMI) than you hoped. Of course reducing the area for the dry cows will also push feed ahead, so if we are still growing grass at the time you get this newsletter, slowing the round down further, will just create a problem in a few weeks’ time!

Grazing pastures with very long entry covers (e.g. >3500kgDM) down to 1200kgDM will result in longer recovery times and poorer subsequent growth rates. This could leave you with less grass in July/August than in your budget as once calving starts we need grass to be growing behind the cows and can’t afford slower growth rates.

Use of ProGibb and strategic nitrogen and sulphate fertiliser behind the milkers and dry mobs in July will help you bounce back quicker and not feel the prolonged effect of these longer entry covers.

Of course putting the milking cows into entry covers of >3500kgDM/ha will also lead to poor utilisation. Milking cows won’t graze as effectively on those really long pastures, leaving higher residuals than you would like for the first round. If we get a couple of weeks of really wet weather this of course will be amplified. A few potential issues here

  • 1/ you overestimate how much grass you think the milkers are getting because their residuals are higher than you want, and then you offer them less area and less supplements and the intakes drop further, spiralling into an under-feeding situation or
  • 2/ you accept these higher residuals and next round when the grass hasn’t grown you make the cows eat into this residual e.g. 1800 residual this round and then 1500 next round. Essentially that’s 300kg/ha of very poor quality feed or 2-3kgDM/cow/day, which may affect milk production and body condition loss.
So we don’t have a one size fits all solution but we want you to –
  • Measure your APC now and monitor weekly (so you know the growth rates)
  • Set up a plan for area offered for each mob and revise it regularly based on your feed situation (using tools that are available such as the spring rotation planner, feed budgeting, etc.)
  • Double check that the pasture intakes (and total intakes) of the cows make sense or match their production, BCS loss and eating behaviour.

  • Let’s capitalise on the grass we have!



    Date Added: Tuesday, 2nd July 2019


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