Ruakura scientists are making international waves with research suggesting that cattle embryos may be more useful than mice for understanding early human development.

But sadly for mice, they are likely to remain the first resort of scientists researching the first stages of mammal pregnancies.

A 5-year AgResearch study in which cattle and mouse embryos were genetically manipulated claims to "prove for the first time that research using rats and mice may not be able to be reliably extrapolated to apply to large mammals, including cows and humans".

The findings - part of work to reduce early embryo loss in dairy herds - focused on a particular gene, Oct 4, which has a role in embryo formation, and found differences in the way it is regulated in mice and cows.

AgResearch embryologist Dr Peter Pfeffer says the use of cow embryos that can be genetically manipulated gives scientists a second model to improve understanding of early pregnancies.

"In terms of embryonic stem cell identity, we think cattle will be more representative than mice of humans.

"By having two mammalian systems we are beginning to understand, we can see that what is common to the mouse and cattle is likely to apply to humans and things that are different may not also apply to humans."

The study was published this week as the feature article in US journal Developmental Cell and was quickly picked up by online magazine Science.

Under the headline "The mouse is not enough", Science quoted Stanford University fertility specialist Mylene Yao, who commended the authors for "dissecting the process of differentiation in the bovine embryo".

"It has really great implications for mammalian systems and potentially human development."

Dr Debra Berg was lead author of the study which needed ERMA approval and construction of a special containment shed.

Early mortality is a growing problem in the dairy industry and Dr Pfeffer says the study shows the need to focus on understanding early embryo development in cattle rather than mice to address the issue.

Dr Pfeffer says it has wider medical implications. "It's early days but at least we've given a clear example of where cattle are actually more similar to humans [than mice] and thus would be a better model system."

Associate Professor Mike Legge, of Otago University's departments of biochemistry and pathology, says significant differences in embryo formation between mammals have been recognised for some time but the research has advanced knowledge of how embryos develop.

"The paper adds to our knowledge of the control of early embryo cell decision-making when critical cell commitment is being made between the placenta and the embryo."

Legge says there will always be limitations in extending embryo development data to another species.