Sward / Pasture Characteristics

The grass leaf has a higher digestibility than the stem thus the greater the proportion of leaf the higher the digestibility

Generally a 5% increase in leaf content would be equivalent to a 1% improvement in digestibility. Good sward management is essential in order to maximise digestibility since grass above 6 cm will be predominantly leaf whereas below 6 cm there are higher levels of dead and low digestibility material. At turnout target grass cover should be around 10 – 12 cm in order to provide satisfactory supplies of readily available material.

A recent series of trials looked at the impact of different sward digestibility’s (Organic Matter Digestibility OMD) on dairy cow performance using spring calved cows in late summer and autumn.

Daily milk yields and grass dry matter intakes were directly related to grass digestibility. Cows allocated the 76% OMD sward were able to consume 0.6 kg more grass and this produced an extra 1 kg more milk than those offered the 73% sward.

Comparison between the 73% and 71% OMD groups shows a similar pattern of intake and milk production.

The milk yield improvements were however, less dramatic (+1.3 kg milk from 1.8 kg dry matter) than that with the highest OMD sward due to the poorer quality.

Other studies have extended these results to show that when pasture OMD exceeds 74% each extra kg of DM intake can result in a 1 kg increase in milk yield.