Turnip crops can provide an excellent highly digestible source of both energy and protein for dairy cows through the summer feeding period - the bulb will contain high concentrations of sugar leading to ME values of around 13MJ per kg DM while the leaf will have a crude protein level of close to 20%. This can be a very valuable addition to the diet at a time when both the energy (and digestibility) as well as the protein content of the pasture are under pressure.
The downside of this highly digestible crop is that it contains very limited levels of effective fibre, the sort that makes cows chew their cud. As a consequence, the crop needs to be introduced slowly into the diet over 4-5 days, the quantity fed needs to be kept below 30% of the total intake (which requires that we know the feeding rate!) and some additional effective fibre e.g. hay, straw, poor-quality baylage, should be added if possible.
To be able to accurately manage the feeding of this crop and gain maximum benefit from it requires that the yield be carefully measured; this will then allow the daily break size and therefore the DM intake per cow to be calculated.
- Take a 4 metre length of wire and bend it into a square to give one square metre. Alternatively, joining a 3.54m length of pipe into a circle will also give a "square" metre.
- Place it in a representative part of the crop and pick all the turnip plants in the enclosed area.
- Place the plants in a bag and weigh in kgs. Ideally, repeat this several times in various parts of the paddock and calculate an average weight.
- Divide the (average) weight from one square metre by 10 to get the kgs DM per square metre.
- Multiply kgs DM per square metre by 10,000 to get the yield of DM in tonnes per hectare.
- Hopefully the crop will still be growing in excess of 100kg DM per ha per day so it will weigh about 2.0 tonne heavier in a further 3 weeks' time!
Note:
- The target feeding rate should be approximately 4kg DM turnips per cow per day.
- For a crop yielding 10.0 tonne/ha, each cow needs to be offered four square metres per day i.e. 400 sq. metres per 100 cows per day, to achieve the targeted turnip intake.
- Plan for as long a face on the break as possible as this will give better utilisation.
- Make sure the crop is fed fast enough to ensure that it is finished before the crop quality deteriorates so that the re-grassing programme is not compromised.
If you would like to discuss measuring your crop and calculating the appropriate feeding rate, don't hesitate to give us a call at Totally Vets.
