Breeding season is now approaching, meaning that cows very vulnerable to metabolic disorders.

Naturally, she will always devote nutrients and energy to milk production, prioritising this over body condition and key hormonal processes, which underpin fertility.

The 2023 and 2024 seasons have been testing. The prolonged wet weather has brought a myriad of challenges at farm level, which have varied greatly depending on location, soil type and other factors.

Typically, this time of year sees milk yield and its quality rocket, as cows enjoy lush, highly digestible swards. This year, however, a delayed start to grazing has left a wide range of covers on farms.

With the second round delayed in most cases, many herds have been grazing stronger than normal covers, are moving onto lower covers and in turn, a lift in grass quality.

Breeding season

Most herds are now approaching peak milk and solids yield, which in turn will dictate production for the rest of the lactation. This includes how much milk can be produced from grass into the summer and backend of the year.

There are a number of reports of lower body condition and reduced yields on many farms, owing largely to the wet start to the year and inability to graze.

These herds will be particularly vulnerable in the run up to peak yield and breeding.

Grass quality

Grazing conditions have rapidly improved and while cows are out full time, we must act with caution now and ensure nutritional requirements are met by realistically assessing what is produced from grazed grass and supplementing accordingly.

Farmers should calculate this with their nutritionist based on their herd’s requirements to eliminate the guess work.

Rapidly cutting feed rates may help with clean outs, however owing to the difficult start of lactation for many herds, now is not the time to push cows, particularly in moderate to higher yielding herds.

Image source: Phileo

Further to this, it is reported that grass crude protein levels are testing quite variably, with levels as low as 16%.

With increasing regulation on the crude protein content of compound feed, it may be worth sending some grass samples for analysis, as exemptions are available to raise the protein content of the compound in conjunction with your feed adviser.

However, grass regrowth coming into the second round is containing significantly lower NDF than usual and will have an increasing rapidly fermentable fibre content, leading to lower rumen pH and a risk of cows developing sub-acute rumen acidosis (SARA).

The risk of SARA

An acidic rumen slows down or kills the activity of fibre-digesting microbes, which has the knock-on effect of reducing feed digestion and energy output from the rumen, resulting in more grass passing through undigested.

Low butterfat levels can be used as an indicator of SARA when combined with other cow signals we can monitor.

Butterfat levels are related to rumen function. The digestion of fibre is a significant component of butterfat synthesis, with high unsaturated fatty acids in grass at certain periods also having a separate suppressive effect.

However, a low rumen pH amplifies the fat suppressive properties of unsaturated fatty acids found in stressed grass plants, reducing butterfat levels.

SARA can have a significant impact on rumen efficiency, herd performance and fertility, leading to a negative impact on milk solids, which negatively impact revenue depending on the contract.

Additionally, excess body condition loss because of SARA predisposes cows to several disorders including lameness, ketosis, milk fever, fatty liver and poor fertility.

Identifying the problem

One way to identify SARA is by looking at dung which can appear bubbly and loose. This results from excess production of acids in the rumen due to the rapid fermentation of grass resulting in SARA.

Undigested fibre particles in the dung and cud balls in yards can also suggest reduced rumen digestion due to lowered pH.

Other signs of SARA:

  • Excessive body condition loss due to reduced dry matter intakes resulting from sub-optimal rumen function
  • Drop of 0.3%-0.5% in butterfat over a week or a 0.3% drop in protein
  • Milk yields drop by around 2-3 litres/cow/day over the course of a week
  • More than 10% of the herd has a higher milk protein % than milk fat %
  • A fat to protein ratio of less than 1.15 to 1.

The below table illustrates the effect on profitability after a sharp drop in butterfat levels on a 100 cow herd over the course of one month.

Protein %3.35%3.35%3.35 %3.35%3.35%
Butterfat %4.2%4.0%3.8%3.6%3.4%
Milk solids kg @ 30 kg2.
Monthly milk price 30 ltrs*3332.531.753130.5
Monthly income / cow*€324€318€310.8€303.60€296.40
Monthly income / 100 cows*€32,400€31,800€31,080€30,360€29,640
Loss of income due to loss of butterfats compared to 4.2% butterfat– €600-€1,320-€2,040-€2,760
Irish milk pricing based on approximately €7/kg protein and €4/kg butterfat. Fixed processing cost of 4c/L

If you think your herd may have SARA, be sure to consult with your vet, as symptoms can also be associated with low protein and magnesium levels or liver fluke.

How to check for healthy rumination:

  • Look at rumen fill three to four hours after morning milking – poor rumen fill can be caused by reduced dry matter (DM) intake due to acidic conditions in the rumen;
  • High protein grass can also cause poor rumen fill as passage rate increases.
  • More than 65% of the herd should be ruminating two to three hours after milking, unless they are drinking or actively grazing;
  • Drool and saliva should be observed around the muzzle, with more than 65 chews/cud where strong rumination is evident.

If you suspect SARA in your herd, research has shown you can reduce the risk by adding Actisaf Sc 47 live yeast to your compound feed.

Actisaf significantly improves rumen efficiency, leading to increased digestion and utilisation of grass. Its stabilising effect on rumen pH reduces the threat of SARA and improves nutrient output from the rumen microbes.

By enhancing the rumen environment Actisaf has been consistently proven to improve fibre digestion, which can be particularly useful on heavier covers and when grass quality begins to decline mid-summer, increasing the nutrients harvested from every bite of feed.

Add Actisaf

Feeding Actisaf in during spring grazing replicates some of the effects of including structural fibre in the diet without adding gut fill.

Phileo by Lesaffre UK & Ireland recommend Actisaf is included at a minimum rate of 1kg/t, with an estimated cost of €10/t.

Adding Actisaf Sc 47 to animal feeds has been seen to boost the performance of animals by improving their rumen/gut microbiota.

This not only improves feed digestibility and energy supply but also the overall health status and well-being of animals, even in challenging conditions.

This helps optimise herd management to deliver full genetic potential, improving breeding efficiency and profits.