Farm Update with Cathal Irwin, Future Beef Farmer
Grass growth is the big challenge this year on Cathal Irwin's beef farm, he is focusing on soil fertility, slurry management, and feed quality to maximise productivity and keep his herd thriving.
Cathal faced a challenge for growing enough grass on his farm this year. Last year he was stocked at less than 130 kg of organic nitrogen per hectare, and this is limiting his maximum fertiliser limits to 114 kg of chemical nitrogen per hectare this year.
How much grass does he need to grow?
As a rough calculation, 36 livestock units (18 cows, 18 calves, 22 finishing bulls, 6 heifers) will eat 187.2t of dry matter per year (5.2t DM/LU). Subtracting 21t dry matter for ration fed (25t at 85% DM), Cathal will need to utilise 166.2t DM of grass this year, which amounts to growing 10.5 t DM/ha of grass at 80% utilisation.
- 18 cows x 0.9 = 16.2
- 22 bulls x 0.7 x 5 months = 6.5
- 12 heifers x 0.7 x 6 months = 4.2
- 18 calves x 0.5 = 9 LU
- Total: 35.9 LU
How much grass can he grow with 114 kg N/ha?
With Cathal’s fertiliser allowance of 114 kg chemical N/ha, it can be estimated how much grass the farm will grow as follows;
- Nitrogen from soil: ~120 kg N/ha (heavy farm estimate)
- Plus animal recycling: 40 kg N/ha
- Plus slurry at 2000 gallons/acre: 25 kg N/ha
- Plus chemical nitrogen: 114 kg N/ha
- Total: 299 kg N/ha
- 299 kg N/ha divided by 3.25% (3.25 kg N per kg of grass) = 2 t DM/ha
In 2024 Cathal measured grass on the farm and grew 8.9 t DM/ha.
Options
Cathal will still be short almost 26 t DM of feed this year, based on the maximum amount of grass that he can grow.
To counteract this, he is:
- Taking soil samples and applying lime to boost soil fertility
- Using slurry, Ps, and Ks on high-response fields
- Delaying fertiliser application until soil temperatures exceed 8°C
- Using LESS for slurry spreading to retain nitrogen
- Buying silage early to manage feed quality
- Using protected urea for better nitrogen retention
Other options Cathal considered include sowing red clover silage to reduce the nitrogen required, but it will not suit his land. He could also buy in ration to make up the difference in feed but it would not be financially beneficial. He could also reduce stock numbers but does not wish to do so, or he could rent more land which will cost more money and cause extra work for him.
Performance
Cathal weighed the finishing bulls on 8th February. The home bred bulls (7) averaged 512kg and gained 2.08kg/day since their last weighing on 4th January. The bought in bulls (16) averaged 578kg and gained 1.85kg/day in the same period.
They are being fed between 8 to 12 kg/head/day based on their weights as they are built up to ad lib ration. They are all being supplemented with 1 bale of straw/week as a fibre source. The lighter bulls that were separated and housed on the straw bedded area have significantly improved with the extra space and Cathal is very happy with them.
One of the bought in bulls was sold on 14th February at 14.4 months of age. He was 423kg carcass weight and graded R+2+ making €2707. He was 780kg live weight on the 8th of February.
The home bred heifers (6) were also weighed on 8th February and averaged 386kg after gaining 0.54kg/day since January. The bought in heifers (3) averaged 510kg and gained 0.35 kg/day on average. They are eating 2.4kg of ration/head/day so Cathal is a little disappointed with them but thinks that lying space is the issue. He plans to sell the non-breeding heifers live over the coming 2 months.
Yearling heifers