Exploit benefits of mixed forage
Exploit benefits of mixed forage
By James Garner
IMPROVING milk protein content by feeding cows mixed forage diets can reduce nitrogen waste in both high and low input dairy systems.
Taking data from two trials – one low and one moderate input dairy system – SAC Crichton Royals Katherine Leach told delegates at the BGS winter meeting in Malvern, Worcs, that feeding extra sugar and starch could improve milk protein levels.
She added that this could be achieved by feeding alternative forages – whole-crop barley and fodder beet – rather than grass silage.
The low input system involved 70 black and white cows yielding 5200 litres with a milk protein of 3.15%. The moderate input system also involved 70 black and whites, averaging 6000 litres and milk protein of 3.17%.
The unknown factor in the low input system is how much nitrogen is being fixed by clover. However, assuming a constant nitrogen fixation level of 140kg/ha (112 units/acre) the low input system showed an improvement in nitrogen efficiency from 23.2% in year one to 25.1% in year three of the study.
This improvement was achieved by increasing the amount of home-grown starch and sugar fed so more nitrogen found its way into the milk tank, said Dr Leach.
"Using alternative forages also reduces the area of clover, therefore theres less nitrogen fixed in the system.
"The moderate input system, once again uses alternative forages requiring lower fertiliser inputs and reducing waste." Before the trial began nitrogen inputs were 320kg/ha (256 units/acre). In the first year these were reduced to 220kg/ha (176 units/acre), along with a cut in stocking rate to 2/LU/ha from 2.4/ha, so inputs were also cut, she said.
Moving to three-times-a-day milking boosted milk yields to a peak of 8145 litres in year two, increasing nitrogen efficiency from 14.4% to a peak of 21.9%.
NITROGENEFFICIENCY
• Higher milk protein %.
• Feed alternative forages.
• Feed more sugar and starch.