Brian Reidy: The many theories why milk volumes are lower

We are now in a critical period for milk production and fertility performance.

There is a lot of discussion about dairy herd performance at the moment.

A collection of the latest news, views and analysis from the farming desk on the topic of Dairy.

Bulk tank drivers are saying volumes are down and many herds owners are suggesting that they are around 3 litres back per cow on the same days last year.

Many theories are being offered for this issue. Some mysterious virus affecting the cows, yet to be named, is being blamed in some quarters.

Some are questioning feed quality, both bought-in and homegrown. I think that the answer may be as simple as the cows and ourselves may be short of sunshine.

Milking cows didn't get settled at grass until recently and were in and out of sheds for most of this spring.

As a result, they were on very variable diets from day to day and unfortunately, too many of the grass silages made in Ireland are not good enough to support milk production when required to replace grazing.

Couple this with a falling milk price and lower feeding of concentrates as a reaction to this and we end up with less milk in the tank.

And don't get me started on cows being held back to stay below a certain Nitrates band.

We are now in a critical period for milk production and fertility performance.

Beyond any underproduction already experienced, at this time of year grazing and feed conditions change and a lot of herds often suffer a significant production drop. These drops can be up to 15% in one month when a normal production curve should see a 6 to 8 per cent drop per month. Herds can't afford to take two performance drops in one season with prices under so much pressure.

Apart from grass quality changing, management should be examined carefully in this scenario. Farmers need to manage grass, it is not the cows' responsibility. Nutrient requirements for milk production are very similar in summer as in spring so the only change causing this milk production drop is the changing pasture base. It's crazy, each year when it is quoted that this yield drop is due to cows now being back in calf. The embryo is not much bigger than an egg and draws very little energy from the cow's consumption at this point. This change in performance is more likely a combination of things.

Drop off in quality of grass offered

The first factor involved in the production decline is the drop in nutrient density of the grass sward.

This relates to decreasing digestibility as the plant matures, which will occur naturally as grass varieties are in their reproductive phase and naturally have heading dates from mid-May to mid-June.

Even when a cow eats the same weight of feed, she doesn't consume the same amount of energy if the grass offered has got stemmy or seeds out.

In other words, there is way more energy in the leaf than there is in the stem and if a cow only has the capacity for the same volume of each then when less energy is consumed then 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 and this has meant variable growth conditions. In reality, it is a combination of the two.

The end product is a reduced nutrient intake by the cow if added supplements are not supplied to the diet or strong paddocks are not skipped and more appropriate grazing swards are offered.

This 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.

I have observed through grass sward analysis that the protein content of grass is a bit lower than normal at present which would indicate that the poor growing conditions and could mean that some of the nitrogen spread lately has not reached the leaf yet resulting in a paler green colour.

While we have seen an improvement in weather recently, we badly need a settled spell of heat and sunshine to improve grass quality.

Uptake of fertiliser and slurry nutrients has been slow due to the poorer weather, which has also contributed to the grass having a lower feed value.

Grazing activity in a stronger than ideal swards

Have you ever spent the time to just observe what your cows do when grazing a stronger than ideal sward of grass?

At this time of year when I visit herds, we walk the farm, measure grass and we can test the grass for nutrient value including Dry Matter, Energy, Protein, DMD, NDF and Sugars.

Most are now underestimating grass covers being offered to cows unless doing regular measuring.

Where cows had taken a drop off in milk volume over the last week or so, covers well in excess of 2000kg are typically being offered, but are being eyeballed as 1500-1600s.

Strong grass depresses total intake and protein is lower in this grass and therefore will further depress intakes.

Ask the cow's opinion of their diet, when you walk around cows these days, look to see if 60 to 70% of the cows at rest are ruminating and how dungs look consistency-wise.

Look at the body condition in the herd and any breeding information available at present. Most herds look in great order, however, as I mentioned above many herds are reporting a sudden milk drop and the Butter Fats have been a little low also recently.

Watching cows graze and looking at the sward in many farms tell an interesting story.

As I said earlier the covers being grazed are stronger than ideal.

In many cases, cows are only eating the top few inches of the sward and moving on to the next bite.

Essentially the cows are being very choosy while grazing and are doing quite a lot of walking around looking for a 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 then they have significantly less time available to lie down and chew the cud which is where they actually make the milk.

How can you reverse the milk drop?

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 ideal 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 and various approaches have been taken.

Some have 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 gone and taken a lot of paddocks out on one day with the plan to commence grazing after grass in these paddocks at lower covers early while introducing a buffer feed to complement these lower covers.

That buffer doesn't need to be complicated, 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 if available particularly if you need to graze lush, low covers to get sward quality across the farm back on track.

Pre-mowing may also be the correct approach on many farms to get improved intakes while improving subsequent grazing swards.

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.