The Growbulk story is one of innovation and opportunity.


early development

Dr Roland Sumner and AgResearch lead the development of the breed over a 13 year period with the sole aim of developing a” hardy dual purpose sheep able to consistently meet both meat and wool processor demands for a fast growing, well muscled lamb carcass from a dam producing a heavy bulky fleece”.

Screening in genetics from across New Zealand, 8 different breed combinations were evaluated before settling on the Romney, Texel and Poll Dorset breeds as the new genetic base. 

Stabilisation of the Growbulk breed was achieved by sourcing the best available genetics from these breeds and developing the Growbulk flock on the Whatawhata hills in the King County. The steep terrain and challenging summer dry of Whatawhata provided the perfect testing ground for the new breed. 

The Growbulks early development on the hills of Whatawhata was also significant in terms of the need to provide a genuine dual purpose breed option that would perform in a range of environments, particularly as sheep production was being pushed from the traditional flat areas into the countrys’ hill and high country.

In 1998 AgResearch took on 4 breeders in an evaluation role to measure the performance of the new Growbulk breed against traditional breed options. Don Morrison at Rosedale was one of the breeders chosen primarily because of the extensive objective measurement undertaken at Rosedale with their Romney sheep and also the extensive cross breeding trials Rosedale was involved in.

From the first years involvement Don Morrison could see the massive opportunity the Growbulk sheep could provide to the New Zealand sheep industry. Lamb vigour and survivability was significant even in the first cross lambs. Lamb growth rates were higher in those same lambs than any other of the crosses being measured and meat yields in the killed lambs were 8% higher.


PLAN A for Rosedale Growbulk was clear, defined and focused…To use the best genetics and the best technologies to breed the most efficient breeding ewe in New Zealand. 

The Rosedale Growbulk breeding programme developed in a JV partnership with AgResearch, incorporates the genetic strengths of the high fertility, high fleece weight Romney base with the high bulk fleece Poll Dorset and Texel. The MyoMax and LoinMax growth and muscling genes from the Poll Dorest and Texel were fast-tracked through the Growbulks to further enhance growth rates and meat yield. Milk production and fertility advantages from the Poll Dorset were capitalised on and lamb vigour and mothering ability from the Texel used to maximise lamb survival.

Since 1998 we have focused on that breeding programme without the constraint of breed limitations and we have been able to introduce additional genetic components where compatible with our focus of total ewe efficiency. Selected use of Perendale, Tefrom and Charollais Sires have been used in both an evaluation and development role.

Rosedale Growbulk today represents 30 years development and stabilisation form both Rosedale and AgResearch. The full use of DNA genetics in the measurement and indentification of production genets has further assisted the breeds development as has involvement in a number of AgResearch and OVITA research programmes aimed at maximising total breeding efficiency.

Rosedale Growbulk has been at the foreground of Research into Lamb Survival, Ewe Longevity, Total Ewe Efficiency and Ewe Body Condition.

Since 2003 Rosedale Growbulk has been ranked number 1 in New Zealand for Lamb Survival measuring Lamb Viabity at Birth. It is currently ranked number 1 in New Zealand by SIL as the trait leader for Dual Purpose breed Meat Yield and has enjoyed Glammies success as a finalist twice in the last three years including Grand Champion Tastiest Lamb in New Zealand in 2012.

Farming can be as simple or as complicated as you want and with Rosedale Growbulk we have found the answer very simple.

What We've Achieved

  • No. 1 NZ rank for Lamb Survival
    since 2003 measuring Lamb Viability at Birth.

  • Glammies Winner
    and 3 times finalist in New Zealand’s Tastiest Lamb
    since 2012.

  • SILACE as Trait Leader
    for Dual Purpose Meat Yield.

  • Plan B People & Planet
    We now offer a 5% donation from all rams sold to a charity, school, sports club, etc of your choice.
  • 400 sale ram hoggets
    tested with 5K SNP Chip(inc Myomax and Loinmax muscling genes.