The dairy industry is warning that AgResearch's heavily promoted AR37 endophyte ryegrass could result in lower milk production in summer and autumn.
The farmer-owned dairy research organisation, DairyNZ, has warned farmers its trials showed AR37 was resistant to pests and did not cause ryegrass staggers, but there could be the loss of 30kg of milk solids a cow over a season compared with grazing the established endophyte ryegrass, AR1.
That equated to about $600 a ha.
"We have now completed two seasons of trials in the paddock and two controlled indoor trials, and the results are showing a level of consistency,'' DairyNZ research manager Eric Hillerton said in a statement.
But Grasslanz chief executive John Caradus says nation-wide trials over a year showed pasture production from AR37 paddocks was 12% more than AR1.
The key factor in turning that into more milk was managing the extra grass growth.
"In terms of increased dry matter production and persistence, all the evidence I have seen to date is that it is living up to the claims.''
He described the 30kg of milk solids less per cow as "not significant'' when taken over a whole year, and while not questioning DairyNZ's research, he said the result could be due to how the trials were run and a difference in clover cover between the paddocks at various times
of the year.
Dr Caradus has not had any complaints about AR37 and said sales were as expected.
Respected Dunedin scientist Jock Allison said he was surprised AgResearch had started promoting the new grass and that the advertisements were fronted by its chief executive Andrew West, when there were questions about its performance.
"The science does not warrant such heavy promotion,'' he said.
The difference in milk production could equate to $600/ha a year on a farm which had a stocking rate of three cows/ha, he said.
DairyNZ's Dr Hillerton said the difference in milk production was more pronounced during summer and autumn than winter and spring.
"Any difference in milk solid production between the two endophyte strains during winter and spring is not statistically significant, but during summer and autumn the production difference is quite obvious.''
Dr Hillerton said his trials showed pasture dry matter yields between the two strains were inconsistent from year to year, which could also mean a claimed 12% increase in dry matter production from AR37 might not be repeated either.
Dr Caradus said Grasslanz Technology, which had developed AR37, was a wholly owned subsidiary of AgResearch.
The stock firm PGG Wrightson did invest in the development of AR37, but Dr Caradus said it could be licensed to other distributors.
The advertising campaign was funded and organised entirely by PGG Wrightson, he said.
"Neither Grasslanz Technology nor AgResearch have put a dollar towards the advertising campaign.''
The ryegrass was developed as an alternative to AR1 which Dr Caradus said did not persist in some dry parts of the country or where there was a heavy pest burden.