Alternatives are diversion
ALTERNATIVE forages are a costly diversion from the real task of producing high quality, high intake grass silage.
Speaking at the conference, Dr Mayne said: "Forget alternative forages on 95% of dairy farms."
He acknowledged forages such as maize and whole-crop could may play a role in lowering forage costs on some systems. But said that the effects of these forages on animal performance had been misinterpreted by producers and researchers.
A close look at results of UK and Irish trials in which grass silage had been replaced partially by forage maize and whole-crop showed no benefit or only small lifts in performance, he said, relative to grass silage only diets when similar concentrates were fed with both diets.
"Alternative forages have diverted emphasis from the primary objective with autumn-calving herds in good grass growing areas – the production of high digestibility, high intake grass silage," he said.
Grass maturity at cutting was the major influence on silage digestibility.
Dr Mayne also warned that reductions in digestibility in mid-May occurred irrespective of whether the sward was grazed in early spring. Delaying cutting date to increase grass yield after grazing in early spring would, therefore, reduce digestibility.
"A careful balance must be struck between the benefits of grazing silage swards in spring and the possible adverse effects on silage digestibility if cutting date is delayed too long in May," he said.
Dr Mayne also stressed that lower intakes of grass silage compared with grass were down to reduced grass digestibility at cutting more than effects of silage-making.
Ensiling reduced DM intake by 13%, whereas ensiling and later cutting knocked intake by 29%.
He recognised that in practice high digestibility silage reduced crop yield, increasing the cost of producing silage. "The challenge for research then, is to examine the scope to prevent the fall in digestibility with increasing grass yield," he said. "Alternatively, was there a way to upgrade low or medium digestibility grass during ensilage?" he asked.