Strong grass is no good for milking cows
It’s that time of year when the hurling gets serious, and everyone seems to know how the Manager went wrong!
It’s also the time when feed conditions change, and a lot of dairies suffer a larger than acceptable production drop.
These drops can be up to 15% in one month.
The Manager also needs to be examined in this scenario.
As we know, nutrient requirements for milk production are very similar in summer and in spring, so the only change causing this milk production drop is the changing pasture base.
And, for anyone blaming good fertility on the milk drop, well, best of luck with that theory!
This change in performance may be one of two things or more likely a combination of these.
The first factor involved in the production decline is the drop in nutrient density of the pasture sward. This relates to decreasing digestibility, as the plant matures, which will occur naturally because grass varieties have heading dates from mid-May to mid-June.
The effect is: if a cow eats the same weight of feed, more of the nutrients are tied up, and unavailable for milk production.
In other words, there is way more energy in leaf than there is in stem, and if a cow only has the capacity for the same volume of each, then when less energy is consumed, less milk ends up in the tank.
The second factor is the variable Irish summer weather and its influence on perennial ryegrass growth rates. Over the last few weeks, we have seen all types of weather, meaning variable growth conditions.
- The end product is a reduced nutrient intake by the cow, unless supplements are added to the diet, or strong paddocks are skipped and more appropriate grazing swards are offered.
- The reduction in nutrient intake means less production, or increased weight loss.
Most of you will also have observed the colour of grass in fields lately.
Grass is in general a pale green colour, and many leaves have a yellow or purple tinge to them.
The colder nights, in particular, are having an effect.
I have also observed, through grass sward analysis, that the protein content of grass is a bit lower than normal at present, which would indicate that some of the nitrogen spread lately has not reached the leaf yet, due to poor growing conditions and the cold, resulting in a paler green grass colour.
Darker grass draws in more sunlight, and we are also deficient in that at present.
Have you ever spent the time observing what your cows do when grazing a stronger than ideal sward?
Earlier this week, I visited a customer and we walked his farm, measuring grass as we went.
I use a quadrant and clippers, and for accuracy, I test the grass for nutrient value, including dry matter.
Firstly, we established that he was currently grazing 2440 kg covers, which is much too strong.
The dry matter content of the grass was 20.1%.
The second observation was that the grass protein content was low, just under 19%.
The cows had taken a drop off in milk volume over the last week, as this type of grass cover was being grazed.
Firstly, the grass was too strong, so its energy content was low, at 11.2 ME, and strong grass depresses total intake, and protein is low in the grass, which will further depress intakes.
With that information on hand, I thought it might be a good idea to ask the cows’ opinion of their diet, as I do during all farm visits.
So, as we walked around the cows, I could see that up to 70% of the cows at rest were ruminating, and their dungs were mostly of a good consistency.
Body condition is excellent in the herd, and the breeding season seems to be going very well.
One observation I always make in a herd is coat colour, and in this case, the black was black, and the white was white.
All in all, a very happy and content herd of cows.
However, this herd had recently encountered a sudden milk drop and the butter fats have also been a little low recently.
Watching the cows graze, and looking at the sward, told an interesting story.
I said earlier the covers being grazed were 2,440kg.
The cows were only eating the top few inches of the sward, and moving on to the next bite.
Essentially, the cows were being very choosy while grazing, and were doing quite a lot of walking around looking for the nice bite.
This activity results in a lot of time and energy being used up to consume grass, resulting in less than optimum intakes of energy, meaning either production drops or body condition drops, or both.
This will have an adverse effect on milk quality also, as lower energy intakes will hit protein, while lower fibre intakes will hit butter fats.
Also in the mix is the reality that if cows spend more time and effort getting the required intake of grass into them, they have significantly less time available to lie down and chew the cud, which is when they actually make the milk.
If you have established that your grazing covers are too strong for optimum performance, then you need to take action sooner rather than later.
Take out the strong paddock ASAP, obviously weather conditions are currently not great for making bales, but every effort must be made to make it happen.
Many will worry that too many of their paddocks would need to be taken out to get back to quality swards. This has been an issue for many lately, various approaches have been taken.
Some staggered the taking out of paddocks so that they will be ready to graze in the next rotation on different days, rather than all being fit to graze on the same day.
Others have taken a lot of paddocks out on the one day, with a plan to commence grazing after-grass early in these paddocks at lower covers, while introducing a buffer feed to complement these lower covers.
That buffer doesn’t need to be complicated, maize silage or good quality bale silage along with increasing levels in the parlour will suffice in most cases.
If using a mixer wagon, this can be complemented with a little straw, particularly if you need to graze lush, low covers to get sward quality across the farm back on track.
What you can’t afford to do is to stay grazing the strong swards.
The problem will just get worse, as covers will just get stronger and stronger, resulting in poorer energy and protein contents, lower digestibility and intakes, and an even lower volume of milk in the tank.
The next six weeks can be very demanding from a grass management point of view in trying to minimise production drops. All pasture changes need to be monitored, and supplementing early to maintain nutrient intake is the key to maintain production over the summer period.
Summary
Strong grass is no good for milking cows, and will depress feed intakes and milk yield and quality.
Remember that if a cow drops four litres overnight due to a poor diet, and you don’t address the energy deficit, her yield will not recover.
It’s not just four litres though! If she has 150 days before drying off, she has just lost up to 600 litres.
