Patrick Lennon

Portaferry

Patrick has 90 acres available for grazing although 30 acres of this is currently used for cereals. Patrick has extended his grazing season considerably this year. He turned out by day on the 10th February but what is more remarkable is that he has turned them out at night since the 18th February (except for six nights of bad weather).

Grass Growth

First of all Leonie showed how it was possible to calculate grass growth rates. First of all she took the current grass cover of 2675. This had fallen from 3,000 kgDM/ha two weeks previously. So grass cover over the farm had fallen by 325 kgDM/ha in the fortnight which averages out at 23 kgDM/ha/day. Then she calculated how much grass had been eaten by the stock on the farm. The 62 milkers are currently yielding an average of 24.5 litres with only a few cows yielding over 30 litres receiving a couple of kg of concentrate. So we assume they are consuming around 17 kgDM grazed grass each per day. The same was was done for each group of animals on the farm as can bee seen in the table. As can be seen a total of 1436 kgDM of grazed grass are consumed each day on Patrick's farm. If we divide this by the 17.6 hectares being grazed this represents a loss of 82 kgDM/ha/day. The farm has only actually lost 23 kgDM/day so the growth rate must be 61 kgsDM/day.

Grass Cover

Leonie then went on to show how it was possible to establish what average farm cover Patrick should be aiming for. First of all a rotation length has to be decided upon. This depends on how prone to drought the farm is. If a farm is not at all prone to drought then an 18 day rotation is sufficient this can go up to 25 days for very drought prone farms. Patrick thought 22 days would be about right. The total grazing area is divided by the rotation length in this case 17.6 ha / 22 gives us a 24 hour paddock size of 0.8 hectares. If the cows eat 1436 kgDM per day and have a 0.8 ha paddock then Patrick need an available cover of 1800 kgDM/ha. If we add this to a residual of 1600 kgDM/ha then the total cover of the current grazing paddock should be 3400 kgDM/ha. Average farm cover should be halfway between the pre-grazing 3400 and the 1600 residual which is 2500 kgDM/ha.

Leonie's Proposal

Leonie pointed out that with Patrick's good grassland skills he was now able to keep the cows out for nearly 10 months of the year. If he moved to compact February/March calving the cows would be dry during the winter period and would require only 3 - 4 tonnes of silage. She proposed that Patrick give up the conacre that he could not graze, along with his beef and cereal enterprises. Cow numbers would be increased to 77 cows allowing a yield of slightly over 5,000 litres which would be achieved off grass and very little meal.

Since very little silage would be required this could be cut as a genuine surplus. Enabling all the farm to be used for grazing. If we repeat the growth requirement calculation for an increased grazing area of 90 acres (36 hectares) and make allowances for slightly increased dairy stock numbers. (77 cows + 39 replacements). We find that all the growth that is needed is 45 kgDM/ha/day which can be achieved in late spring / early summer with no nitrogen and a good clover sward.