Article By: Country Wide-Magazine. Source: Country-Wide

The magnitude of ryegrass staggers last autumn is likely to have contributed to below average scanning percentages in flocks in Marlborough and Canterbury. The spring lamb cheque is likely to suffer as a result.

To find out more about the problem, AgResearch investigated the effect of ryegrass endophyte on sheep's eating habits. Scientists found that sheep are not prepared to eat less each day, as a way of reducing their intake of endophyte alkaloids. "Sheep are reluctant to reduce their daily intake and will eat high endophyte ryegrass if that is all they are given," says project leader Gerald Cosgrove.

Endophytic fungi in ryegrass helps protect the plant but also produces alkaloids that cause heat stress, reduced intake and staggers, when consumed by stock. The three key alkaloids are lolitrem B, ergovaline and peramine.

"In the typical ryegrass/clover sward, with limited clover or low-endophyte grasses, sheep have few alternatives and they suffer the consequences. Farmers must look to alternative species for protection during crunch periods," Cosgrove says.

In the 2001 trial, Romney hoggets were offered three options - perennial ryegrass with wild-type (high) endophyte (E+), ryegrass with no endophyte (E-), and white clover. The sheep were grazed on the blocks in December and February and their feed preference and intake were measured. The clover and grass were single swards placed side-by-side.

Results show that while sheep can detect endophyte alkaloids in the grass, they only avoid eating them when doing so does not reduce daily intake, or change the proportion of grass and clover in their diet. In other words, sheep are reluctant to reduce their daily intake and will eat high endophyte ryegrass if that is all they are given. Sheep prefer about 70% clover and 30% grass in their diet, although this varies with seasons and climate.

Sheep given either high endophyte (E+) or nil endophyte (E-) ryegrass alone, grazed for around 400 minutes/day. When they were given a choice between E+ and E- ryegrass, they still ate a combination of both, but showed a strong preference for E- grass. For example, in February, the time spent grazing E- was considerably longer (280minutes/day) compared to time grazing E+ (90 minutes/day).

When sheep were offered ryegrass and white clover, the sheep strongly preferred the clover, although they did eat some grass (either E- or E+). Results suggest that when sheep are offered both clover and ryegrass, they are not fussed whether the grass is high or low endophyte, as long as they are getting a high intake of clover (around 70%). This high clover intake is not possible in a traditional mixed sward situation. With a diet rich in clover and a small proportion of ryegrass, having high endophyte ryegrass did not alter sheep's preference for clover.
Scientists were also curious as to whether it is the high endophyte levels in grass that cause sheep to prefer more clover in their diet at different times. They found that there were differences between December and February grazings in terms of the proportion of clover in the diet. Sheep ate a greater proportion of clover in February (85%) than in December (63%), and this proportion was higher because they ate less ryegrass. As this trend was the same for E+ as well as E-, scientists believe that it wasn't endophyte that was causing the sheep to avoid ryegrass. Rather it was because the ryegrass was less digestible in February, even though it was still reasonably dense and leafy.

The research was funded by the Foundation for Research, Science and Technology and presented at the Society of Animal Production Conference, June 2002.