THE COVETED end game of breeding cattle tough on the outside and tender on the inside is indeed possible, prominent animal scientist Dr David Johnston believes.
It comes down to selecting bulls in commercial situations based on expected progeny performances across both the carcase and the cow, he says.
And that means understanding what traits are under genetic control, how traits correlate and what the economic value of various traits are in your system.
Dr Johnston, from the Animal Genetics and Breeding Unit at the University of New England, appeared at the latest Intercollegiate Meat Judging Association webinar series.
Speaking to a colourfully-named topic "Rumps and Humps, Eggs and Pregs," he outlined the tightrope producers walk in juggling the many demands on cattle breeding programs, from meat quality to herd fertility.
Put simply, we want to make lots of money from the carcase traits of the steers our bulls are putting on the ground and we also want lots of calves from his daughters coming through the herd.
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So how do we balance the traits controlling carcase and those controlling calf numbers?
Dr Johnston said performance was a combination of genetics and the environment.
Making improvements meant simultaneously selecting for the right traits and innovating in terms of production systems.
How much comes down to genetics?
That is estimated via heritability, Dr Johnston explained.
He presented ballpark figures for carcase and meat quality: carcase weight is 45 per cent heritable, P8 and rib fat 30pc, intramuscular fat and marbling 30pc, eye muscle area 25pc and yield 45pc.
For cow traits: calving ease 10pc, cow weight 50pc, birth weight 40pc, heifer age at puberty 50pc and resume cycling interval 40pc.
"So, yes we have traits in both the carcase and the cow that are under genetic control and we can use estimated breeding values to utilise those known heritabilities to predict progeny performance," he said.
The first step to getting right the balance of traits is to have very clear breeding objectives.
The art is in weighing up trait heritability, the amount of genetic variation and whether there is any antagonism between traits. It is in knowing the economic value of traits in your system and in factoring in the production system, the target market, the breeding system and how long it takes to see traits expressed.
"Target markets are important, for example, because why would you select for tenderness if you are targeting the ground beef market," Dr Johnston said.
"And knowing which traits are the profit drivers in your system is critical.
"For example, for Brahman Jap Ox, the number one trait to breed for is cow weaning rate - the fertility of the herd is paramount to driving profit.
"However, at the same time, the liveweight, dressing percentage and saleable meat constitute about 40pc of the index."
An important thing is some of the traits are correlated. If we select for one trait does it affect another?
Both favourable or antagonist relationships can exist between traits.
So if a producer does selection to change carcase traits, what happens to the cow traits?
Research has shown across the board for carcase traits and cow traits there are no major antagonisms except for the relationship between the weight of the carcase and weight of cow, Dr Johnston said.
"We can change carcase traits without having a major effect on reproduction, for example," he said.
"Likewise meat quality traits have a low-to-moderate correlation with cow traits."
Dr Johnston suggested areas where more data could be important for researching additional traits - for carcase things like ossification, colour and Meat Standards Australia index; for meat quality iron content and fatty acid profile and for cow traits body composition, feed, adaptation and methane.
"And we have to work out should we even be bothering selecting for meat quality - are there clear market signals and do we know how much change is possible?" he said.
In summary, multi-trait breeding objectives are needed to make profit.
"And we can't ignore that adaptation is critical in the north - heat production, cow size, fat deposition has to be considered against carcase weight, yield, tenderness," Dr Johnston said.
"We have to look at alternative measures to get more data into genetic evaluations.
"And we should always be looking for non-genetic solutions to improve meat quality like ageing and tender stretching.
"The bottom line is if we want to improve carcase and reproduction we have to measure both, then select on both according to the defined breeding objective."
The story How to breed cattle tough on the outside, tender on the inside first appeared on Farm Online.