High sugar ryegrasses for livestock systems in New Zealand
Date
2007
Type
Conference Contribution - published
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Fields of Research
Abstract
There has been mounting interest over the proposed
production and environmental benefits from using
perennial ryegrass cultivars bred to have higher water
soluble carbohydrate content (high sugar grasses). Here,
we objectively review published evidence, from the EU
and New Zealand, of the effects of these on milk yield
per cow, liveweight gain in sheep, N utilisation and wider
trophic interactions. The literature reveals substantial
variation in animal responses, though some of the
uncertainty in interpretation can be resolved by combining
the data from multiple trials, and showing this forms a
continuum of response to diet quality. It also reveals
variation in the degree to which the sugar trait has been
expressed, possibly reflecting a gene x environment
interaction. Achieving a more consistent, and probably
greater than current, expression of the high sugar trait
would be a valuable goal. We suggest ‘proof of concept’
has been shown, notably for the potential for improving
N utilisation in the rumen, and so reducing the proportion
of N intake lost in urine. The evidence suggests that this
may be a greater challenge, albeit a more valuable goal,
because of the relatively high N (crude protein) content
forages that predominate in the New Zealand pasture
industry.
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Copyright © The Authors and New Zealand Grassland Association.