Managing wet conditions in Tyrone

Heavy downpours and wet ground conditions at the beginning of the month made grazing difficult on Richard Marshall’s farm in Omagh, Co Tyrone, and led to cows being housed for five days last week.

However, Richard got away with grazing while ground conditions were deteriorating for a few days longer than he previously had during wet times in other years.

Recent improvements to grazing infrastructure have allowed him to take a snatch-and-grab approach to keeping grazed grass in cows’ diets. The two key changes he has made since joining the Dairylink Ireland programme last year are opening additional gaps into paddocks and installing extra drinkers.

This allowed cows to be back-fenced in paddocks while conditions were deteriorating underfoot. Back-fencing stops cows from walking over grazed ground, but it is only possible when there is a drinker available in each grass allocation.

The extra entry points into paddocks stopped poaching around gaps as cows did not have to walk through the same gap twice. Damage was also avoided by on/off grazing where cows are at grass for a few hours but are brought in after they finish grazing.

The milking platform was walked on Wednesday for a grass measurement and then again on Friday to assess ground conditions. Grazing recommenced the following day when cows were back fenced for a few hours after morning and evening milking.

Growth

Although it was wet at the start of June, it was still relatively warm, and grass grew at 70kgDM/ha/day on the Marshall farm last week. With no cows grazing, this left Richard with 8.5ha that was too strong for grazing.

These paddocks were mowed on Monday and were baled the following day, which allowed the ground to rejoin the grazing rotation quickly. Delaying this until second-cut silage at the start of next week would have led to a substantial grazing deficit on the milking platform.

A back-of-an-envelope approach to budgeting grass was set out in last week’s Dairylink article (see www.ifj.ie/envelope). It involves estimating grass covers in each paddock, calculating average cover per cow and then comparing this to the mid-season target of 160-180kgDM/cow.

The need to bale 8.5ha of strong covers pushed stocking rate on the Marshall farm up to 6.21LU/ha and meant average cover per cow on the grazing rotation was low during the grass walk last week at 111kgDM/cow.

Buffer

Dairylink Ireland adviser Aidan Cushnahan said that Richard will need to buffer-feed cows with bales until supply catches up with demand. This is illustrated in the grass wedge in Figure 1 which shows a deficit between actual covers (red bars) and demand (black line running from target pre-grazing cover to target post-grazing residual).

Richard uses computer software programme AgriNet for grass budgeting which compares supply to demand within individual paddocks. This is more comprehensive than the back-of-an-envelope grass budgeting technique which is based only on an average across the whole milking platform.

However, for farmers who don’t have a subscription to a grass software program, budgeting grass based on average cover per cow alone is still much more useful than no grass budgeting at all.

It may seem that Richard mowed too much surplus grass because he now has a deficit, but remember the paddocks which were baled were above the black line in the grass wedge, so they were too heavy for grazing.

Turning cows into these paddocks would have led to poor post-grazing residuals.

Meanwhile, grazing would be delayed in the paddocks that are on target in the grass wedge, so covers there would have also gone over the black line and became too strong for grazing.

Aidan Cushnahan points out that buffer-feeding bales does not mean Richard is short of grass, but rather he was short of paddocks with the correct post-grazing cover.

Grass in a bale is money in the bank as it will still be utilised by cows and will not lead to grass quality being compromised on the rest of the milking platform.

Drying off

The first cows will be dried off on the Marshall farm at the end of next week.

The aim is to have a two-month dry period plus any cow yielding less than 12 litres is dried off early.

Richard is assessing body condition by feeling for fat around the tail head and any thin cows will also get dried off early.

Dry cow therapy

Selective dry cow therapy is carried out on the Marshall farm with records of breeding, scanning, mastitis cases and milking recording used in consultation with a local vet to decide the treatment.

In general, cows with no cases of mastitis and a somatic cell count under 150,000/ml get teat sealer only.

Read more

Dairylink: a beginner’s guide to budgeting grass

Dairylink: making silage four times a year