As we enter into the second week of closing, the effect of grazing heavier covers becomes apparent; cows are working harder and milk production is beginning to fluctuate.
The two most important areas excellent farmers focus on are cow Body Condition Score (BCS) and grazing residuals.
But is there a trade off?
- If we work cows hard to achieve low residuals are we burning off too much body condition?
- If we allow a slightly higher residual, can we improve milk performance and minimise body condition loss?
I would argue with both points. We know that higher pre-grazing covers (>1,800kg of Dry Matter per hectare(DM/ha)) have a slightly lower energy content than mid-summer pre-grazing covers (1,400-1,600kg DM).
So as the energy content is lower, how can we avoid working too hard and avoid negatively affecting BCS?
Striking the perfect balance
If we constantly graze the highest covers on the wedge, the energy intake of the animals will be compromised – therefore move cows onto some low covers every few days.
This will increase the energy content of the diet and give cows a break from working hard while grazing the high covers, as lower covers are much easier cleaned out.
Last week, I sent away two grass samples to compare energy content.
One sample was from a cover of 2,000kg DM/ha and the second was from a reseeded paddock prior to its first grazing (1,000kg DM/ha). The quality of both samples was disappointing.
Older Sward – Pre-grazing cover of 2,000kg DM/ha
Reseeded paddock – Pre-grazing cover of 1,000kg DM/ha
Looking at the results
The high cover had a Metabilisable Energy (ME) of 10.3MJ kg/DM. I thought this would have been closer to 11MJ.
The second sample from a reseeded paddock had a higher ME at 11MJ per kg/DM, however I would have expected this to be closer to 11.5MJ per Kg/DM.
The two samples highlighted the effect shorter daylight hours has on grass quality. If you want to query a grass sample on your own farm, send it away with your meal rep.
It is tested using the same machine that tests silage so there should be no charge. The grass quality samples above are from our farm and are not an average – hopefully your own will test much better!
Move between heavier and lighter pre-grazing covers
It is advisable to fluctuate between heavy and mid-range covers (1,200-1500kg DM/ha) to balance feed quality.
With the slurry spreading deadline looming, we have worked through heavy covers for four-to-five days in a row as we need to get certain areas of the farm grazed off and spread.
Cows have dropped back 1-1.5L and protein percentage will be a back a bit but the residuals have been super.
Now we have moved them onto two days of 1,200kg DM/ha covers before moving them back to the next 2,000kg DM/ha cover.
The lower cover will prevent further milk drop and it may lift production in terms of litres and milk solids.
When we have ground conditions in our favour, we will not leave high residuals. Target residuals are particularly important between October 1-20.
These paddocks will carry covers greater than 800kg DM/ha over the winter and therefore the base of the sward must be clean for it to winter well.
The importance of Body Condition Score
As we mention wintering the grass well, we must also winter the cows well.
An adequate Body Condition Score (>2.75) at dry off is crucial to ensuring cows will calve in good condition (3.0) next spring.
On many farms, Body Condition Score is behind target and there are several steps to take to correct this.
Steps to correcting Body Condition Score:
- Get an independent person to body condition score your cows, sooner rather than later.
- Send silage samples away to identify how good/bad winter feed quality is.
- Allow a longer dry period for under-conditioned cows.
- All heifers must get 12 weeks dry as they are still growing and their mammary glands take longer to repair any damaged tissue during the dry period than mature cows.
- Cows carrying twins will not gain any condition between now and calving so it is crucial that they get a longer dry period also (e.g. 12+ weeks).
Once we measure we can manage. If we don’t identify how good or bad silage quality is, we will not know how likely the animals are to gain weight on this feed during late autumn or winter.
A member of your discussion group or advisor could score your herd.
Monitor grass quality with calves
It is also important to monitor grass quality with calves – they need to be on rocket fuel, bigger calvers or preferably in-calf heifers can clean up behind them.
However, as with the cows, do not work any group too hard or they will lose too much condition.
If grazing out poor quality swards, move them onto some high quality feed afterwards.
Where in-calf heifers are following calves, keep calves fenced off a proportion of their field so that the in-calf heifers can get a fresh break before going to work on whatever the calves have threw out of the high chair.
