Changeable weather during the months of March and April delayed the closing of silage ground on most drystock farms, which may result in a later cutting date.
In this article, Gabriel Trayers outlines why high-quality silage (+70% DMD) is required for priority stock such as weanlings, finishing stock and autumn-calving cows. He also details how Future Beef Programme participants Michael and Niall Biggins have readjusted their plan to meet the feed requirements of both dry suckler cows and weanling heifers.
Following a delayed spring, silage reserves have become depleted on many farms. Many will push harvest date into June to make sufficient fodder and to rebuild reserves. However, this will result in a drop in silage quality to 68% DMD. This type of silage is fine for a spring-calving suckler herd, where the maintenance of body condition is the primary objective. Feeding this type of silage to weanlings, however, will result in additional supplementation rates to achieve the desired levels of winter weight gain.
Located just outside Glencorrib, south Mayo, Michael and Niall Biggins calve all their cows in spring. Calving, which is targeted to a 10-week window, commences at the beginning of February. The system is simple, selling quality bulls in late autumn and retaining the weanling heifers. These heifers are kept for the first winter. The plan going forward is to keep them until late spring or early summer, where they will be sold off grass. The weight of these heifers will have a major bearing on the price received.
The overall target is to have the heifers achieving at least 1kg/day since birth, with 0.6kg/head/day being achieved over the first winter. To achieve the latter target, they need high-quality silage (+70 DMD) to continue to grow over the housed period. If high-quality silage is not available, additional concentrate supplementation is required.
Gabriel Trayers and Michael and Niall Biggins pictured on farm
For example, heifers receiving a 66% DMD silage will need an additional +2kg of high-quality concentrate feed to maintain the growth levels required over the winter period. This adds to input costs, which could be saved by making high-quality silage.
With a spring-calving herd, cows need to be in a ‘fit condition’, calving at a body condition score of 2.5. Any score above that can lead to calving difficulties. Feeding high-quality silage to spring-calving cows could lead to an increase in body condition, so they need to be fed differently to the heifer weanlings on the farm. As a result, the plan is to make high-quality silage for the weanlings by cutting 14ac at the end of May. The remainder of the silage ground will be allowed to grow until the first week of June. This will be of lessor quality, but will be ideal for the cows next winter. The second cut will also be kept for the cows.
Challenges at closing
Closing ground to cut at the end of May has been a real challenge this year. A wet March delayed fertiliser applications. The 14ac earmarked for May silage had been grazed bare in February and 3000gals of slurry were applied in early April. To target cutting at the end of May, Michael and Niall reduced the chemical nitrogen application to 54 units, which was applied on April 15th. The slurry application added another 27 units of nitrogen/acre, giving a total nitrogen application of 81 units per acre. As a rule of thumb, grass growth will use two units of N per day. So this crop should be safe to cut in 40 days from the date of application.
Sugar and nitrate testing
Michael and Niall check the sugar and nitrate levels of their grass each year before cutting. They feel that this test will be particularly important this year due to the later application of fertiliser. Both sugar and nitrate levels are two important factors in achieving a good preservation at harvest.
When ensiling silage, the aim is to get the bacteria in the silage to convert the sugars available as quickly as possible to lactic acid to drop the pH of the silage to around 4. At this level, the silage is stable. The higher the sugar content, the more food for the bacteria and the quicker the pH drops. The target sugar content to ensure good fermentation is 3% or higher. Before harvesting the crop, Michael will bring a grass sample into his local Teagasc office. This grass will be tested using a refractometer to determine the sugar levels.
The possible high levels of nitrate is another concern, which can increase the buffering capacity, thus making it more difficult to reduce the pH level. This will also be checked in the local Teagasc office. If the nitrate test reading is high, the most likely cause is that not enough time has elapsed from the spreading date. In this case, cutting the crop may need to be delayed.
However, a delayed harvest will have consequences, as grass digestibility decreases by 2 to 3% units per week from the second-half of May. This decline reflects the increasing proportion of stem in the grass plant as the crop matures, typically:
A leafy sward with little or no stem should typically give a 75-80% DMD silage;
On the point of the seed head emerging (some stem), typically you should get 70-72% DMD;
If the seed head is emerging/emerged, silage quality will typically be less than 68% DMD.
Teagasc work has shown that if the sugar level is above 3%, with some nitrate, your preservation will be okay. To increase the sugar levels you can cut in the afternoon/evening, when the sugar levels have increased in the grass and wilt the silage to >28% DM to increase the sugar concentration. This will negate the effect of a high nitrate reading. However, if the sugar level is below 3% and the nitrate level is high, it is advised to wait until the sugar increases and the nitrate decreases.
Source: EMM/ A&FDA
