More Feed For Dairying

There’s a top limit of about 15 tDM/ha per year from non-irrigated rye-grass/clover pastures with no nitrogen fertiliser input, according to dairy scientist Dave Clark, working with Dexcel in Hamilton.

Dr Clark says this is a serious constraint to future increases in productivity from our dairy farms. So how can we feed our dairy cows better to achieve the extra 4% growth in production (the target set by this industry) without additional production or environmental costs?

One way is to look at using other forage crops, suggests Dave Clark. Potential annual yields of up to 26.6 tonnes of dry matter per hectare can be obtained from some temperate grasses, and maize, combined with a winter cereal, can grow up to 45 t DM/ha. “And in El Salvador the sub-tropical species, napier grass, produced up to 85 t DM/ha,” reports Dr Clark.

“But a major switch to crops is not feasible” he says, “because these high-yielding forages have insufficient crude protein to support dairy cow lactation, and high protein crops, such as soybean, are very low yielding.” Dr Clark considers that future gains will more likely come from increasing stress tolerance in pasture plants – making them more pest, disease and drought tolerant.

Biotechnology offers potential by improving photosynthesis of forages by up to 20%. Possibilities include transferring genes from subtropical plants such as maize, or by using a photo-synthetic enzyme, such as rubisco, from other plant sources. Bio-technology is also providing new know-ledge about controlling plant development and stress response that may allow dairy farmers to achieve another 5 t DM/ha per year from rye-grass-clover pastures.

16th April 2003
Source: Deric Charlton