Maintaining persistency during late lactation ‘critical’ for farm profitability

Maintaining persistency in late lactation within your dairy herd is critical to prolonging income and maximising profitability of the whole lactation.

This period presents an opportunity as the potential value of milk increases due to higher levels of milk constituents with moderate levels of supplementation typically being required.

James Ambrose, technical manager of Phileo by Lesaffre UK and Ireland, suggests ways to take advantage of the late lactation period as well as gearing your cows up for the dry period.

In many ways, milk solid yield during this period will be determined by the management, environmental factors and nutrition of cows during the late spring, when yield is at its peak, as well as through the summer.

As a rule of thumb, cows’ performance should only decline a maximum of 10% per month after peak yield. In other words, a herd that peaked at 32L in early May and held this for one month should yield approximately 19-20L at the start of October – a 40% reduction over four months.

The lower this reduction rate is over the summer period, the better production will be in the autumn.

It is worth reviewing your own herd’s figures to see if persistency was maintained through the summer months.

If not, it is worth trying to pinpoint why this may be so in order to try and rectify it for lactation 2020 (unfortunately issues that have led to poor persistency during the current lactation can’t be rectified now).

One of the most common issues that causes poor persistency in herds is failure to maximise dry matter intake (DMI) of the herd pre and post-peak and through the summer months.

DMI can become an issue, particularly during wet weather or where stocking rates are high on the milking platform. Herds that are including zero-grazed grass in the diet can also be at risk of persistency crashing if every cow is not able to eat grass at the feed barrier at the same time.

Feeding cows to maintain yields

We are well and truly into the final 100 days of lactation now for most herds and we need to be cognisant that the potential yield from grass declines for a number of reasons during the autumn.

These include:

  • Reduced dry matter (DM) content due to wetter weather;
  • Decline of grass intake as the days become shorter;
  • Grass fibre levels increase and digestibility decreases;
  • Grazing covers greater than 1,500 kg DM;
  • Grass energy levels decrease;
  • High crude proteins in grass can utilise excessive energy within the cow.

As farmers attempt to extend the rotation and keep grass in the diet for the remainder of lactation, it is important to be mindful of grass quality in autumn and adjust the diet accordingly.

At current prices, feeding concentrate and high-quality forage in addition to grass will more than pay off as higher milk solid yields are achieved and their subsequent revenue realised.

1.55kg MS returning €6.11, leaving a margin of €3.56/cow/day. Cows yielding 25L should be fed 5kg of compound feed if above grass intakes are being achieved. Diet cost – assuming feed costs of: grass @ €0.09/kg DM; compound @ €300/t; silage @ €130/t DM

DMI is essential to maintain persistency and should be monitored as closely as possible. As the weather gets wetter, grass DM will drop, so this has to be made up for elsewhere in the diet.

17kg of grass DM will support maintenance plus 23-24L in May, while the same intake of autumn grass will typically support maintenance of the cow plus 20L.

However, these sort of grass intakes are not really attainable during the autumn, and it is better to set the estimated intake from grass at 15kg DM. This will support maintenance plus 15L in dry weather and more if the cow is supplemented with concentrate accordingly above this yield.

During rain lasting up to a few days, parlour feed rates should be increased by 1-2kg/day until that passes. For more prolonged periods of wet weather, cows should be buffer-fed with high-quality forage.

Baled surplus grazing paddocks from earlier in the year are ideal in this regard. If additional nutrition is not provided quickly after the onset of wetter weather, milk yields will shut off and the dry period will come on early.

Looking ahead to the dry period

Cows should be scanned by early October and their body condition should be scored. Ideally, a body condition of 3.0 is required by the time a cow is dried off, so thinner cows and heifers will need to be fed additional concentrate during late lactation to improve their condition.

Taking this step now will save time, pen space and labour from having to separate and feed cows for condition score gain during the dry period.

Any cows that are in the right condition should not be fed once they are yielding less than 15L and still at grass.

We do not want fat cows (condition score 3.5) at drying off as these cows are at significantly greater risk of developing major metabolic health disorders post-calving such as ketosis, which severely impacts on production and fertility.

Milk recording sheets and scanning lists should be consulted to determine when cows should be dried off. Ideally, cows would milk for 305 days and have a 60-day dry period, which is the goal of compact spring and autumn-calving herds and is an indication of good herd fertility.

However, this is not always achieveable and, at this stage of the lactation, calving date and subsequent drying off date are more important than achieving a 305-day lactation as we need to ensure we provide sufficient time for the cow to prepare for the subsequent lactation.

Cows will need between a six and eight-week dry period. For example, cows calving mid-January 2020 will need to be dried off by the end of November and cows can be dried off in batches with a three-week spread on calving date within a group.

For example, one group could include cows that are six to nine-weeks pre-calving, which eases the transition of cows from the dry cow group to calving pens when they start to spring down.

Ideally, we would move the group that were batched at drying off to the calving pens / transition cow shed together in order to minimise social stress, which is not desirable around calving.

Any lameness issues should be addressed before drying off, and cows who have suffered repeated bouts of mastitis and those not in calf should be culled. Don’t carry surplus stock through the winter, particularly if head feed and lying space are limited.

Including Actisaf live yeast into the diet of cows that are grazing autumn grass will help to prolong lactation persistency by improving digestion of more fibrous grass leading to improved feed conversion efficiency.

Actisaf essentially gets the rumen microflora to release more energy from grass, making more energy available for milk solids production.

Key points:

  • Do everything to promote persistency of production in the final 1/3 of lactation – maximise milk solids production for the last 60-90 days of lactation and take advantage of higher milk prices due to increased milk protein and fat percentages;
  • Calculate your herd’s persistency for this lactation;
  • Recognise the limitations of grazed grass and supplement accordingly with concentrate and high-quality forage;
  • Implement the autumn rotation planner (ARP) and start closing grazed paddocks for next spring in the first week of October;
  • Assess body condition score (BCS) and feed for a target BCS of 3.0 for drying off;
  • Start grouping cows according to calving dates.