Our philosophy on carcase traits recognises that genetically higher levels of muscle and fat contribute to genetically higher levels of Whole Body Energy.
Genetic energy reserves are seen in the condition of our animals & its condition score that maintains our animals during challenging times, helping build overall flock resilience.
Yearling Eye Muscle Depth
There are 5mj energy in a kilo of muscle (or lean tissue)
“Every extra mm of EMD reduces AWT by 2.5kgs” Dr Mark Ferguson – neXtgen Agri (link to web)
Our selection for muscle is partly to improve the carcass appeal of our sheep for the butcher though mainly to improve the maternal efficiency of our ewes.
Muscle helps cap adult weight, which has significant flow-on benefits to stocking rate & profitability.
As an extra bonus, we also gain value from a positive genetic correlation of muscle with worm resistance & staple strength.
Correlations of increased eye muscle depth
- Higher reproductive rate in ewes
- Higher worm resistance
- Higher lean meat yield
- Higher dressing percentage
- Shifts lean meat from the forequarter to the loin
- Can reduce growth
- Can reduce eating quality
Yearling Fat
There is 37mj of energy in a kilo of Fat.
Whole Body Energy (WBE) is the fuel tank of energy our animals draw down on when faced with a nutritional, or environmental challenge. The bigger the genetic Fat reserve, the bigger the fuel tank.
The beauty of breeding sheep with a large genetic fat reserve is that they can lay down fat when feed is cheap, effectively filling a large fuel tank with cheap fuel. This fuel (or fat) can then be drawn down when feed is not cheap, reducing the need to refill with expensive fuel. This is particularly important during the lambing period & drought periods, or any other time the sheep are faced with a challenge.
A large genetic fuel tank leads to far greater “system efficiency” in our flocks through:
- increased stocking rates
- reduced maintenance requirements
- links to early puberty
- ewe lamb joinings
- providing energy for lambs to thrive from birth
- maintaining body weight of lambs in tough times
System efficiency, achieved through selection for Fat, is our best genetic tool to manage our variable farming climate, & is one of the key genetic differences we are most proud of in our sheep.
Correlations of increased fat cover
- Improved reproductive rate
- CV of fibre diameter goes down
- Intramuscular fat (marbling) improves
- Eating quality improve
- Fleece weight can go down
Intramuscular Fat
Our Genomics testing has opened the door to measuring IMF.
This is a trait we have only recently started selecting for with expected correlations to eating quality and tenderness. IMF is a 2nd tier trait that we include in our selection mix where we can.
This is a trait we have only recently started selecting for with expected correlations to eating quality and tenderness
Shear Force
Our Genomics testing has opened the door to measuring SHEARF5.
This is a trait we have only recently started selecting for & is the measure of pressure needed to cut through a piece of meat. SHEARF5 is a 2nd tier trait that we include in our selection mix where we can.
This is a trait we have only recently started selecting for with expected correlations to eating quality and tenderness
Adding high levels of muscle & fat to the Mumblebone sheep was a deliberate step & has created a significant point of difference between Mumblebone & most other bloodlines throughout Australia.
The traditional merino has unfortunately developed the reputation of “being born to die”. This reputation has come about through the over-selection of wool traits, at the expense of fat & muscle, which form the energy reserve an animal can draw down on when under pressure. The result of this selection emphasis is that these “wool focused” sheep quickly run out of energy when under pressure leading to poor foetus conversion & high ewe mortality.
The Mumblebone sheep have been designed to live.
Combining selection for muscle & fat, with growth & wool, is the simple step Mumblebone took to ensure our genetics offered breeders the chance to achieve high foetus conversion & low ewe mortality, with a high value fleece – all critical components of profitability.
Sheep with genetically higher levels of EMD and FAT gain condition more quickly in good times & take longer to lose condition when under pressure.
The ability for sheep to feed on condition when feed is “cheap” (or plentiful) creates the opportunity for them to draw down that condition when feed is scarce. Conversely, sheep that have lower levels of genetic fat and muscle are the first sheep to lose condition when under pressure, and are the first sheep to lose wool cut or foetuses because they don’t have the energy reserve to maintain them.
Muscle and Fat are essential traits in a modern merino flock.
Muscle
1kg of Muscle = 5mj energy.
1kg Fat = 37mj energy.
Carcass muscling is reflected by eye muscle depth.
- Correlations of increased eye muscle depth:
- Higher reproductive rate in ewes
- Higher worm resistance
- Higher lean meat yield
- Higher dressing percentage
- Shifts lean meat from the forequarter to the loin
- Can reduce growth
- Can reduce eating quality
Fat
Carcass fatness is reflected by the depth of fat between the eye muscle and the skin. Fat increases the ability of breeding ewes to maintain weight and condition in “tough” times.
Correlations of increased fat cover:
- Improved reproductive rate
- CV of fibre diameter goes down
- Intramuscular fat (marbling) improves
- Eating quality improves
- Fleece weight can go down
- IMF (intramuscular fat)
This is a trait we have only recently started selecting for with expected correlations to eating quality and tenderness
Mumblebone is an excellent example of using all the tools available to breed great Merino sheep that meet the needs of the future-focussed sheep farmer.
The change in sheep type, lift in the wool and repro data, and big steps forward in the farmability traits like fat, muscle and worm resistance over the last decade have been fantastic to be a part of.
CEO at neXtgen Agri & Breeding Consultant
