27 February 1998

Researchers look to composite calves for consistent quality

By Jonathan Riley

COMPOSITE-BRED beef calves have consistently achieved higher weaning weights than purebred counterparts in US studies, says beef producer Richard Fuller, technical director of the Yorks-based Beef Improvement Group.

As part of a fact-finding tour of the US, which aimed to establish how to organise a sustainable method of breeding suckler cow replacements, Mr Fuller and the Beef Improvement Group visited the Clay Research Centre, Nebraska.

"The Clay centre was established in 1966 as the US Meat and Animal Research Centre, and 32,000 pigs and cattle now pass through the centre every year," says Mr Fuller.

A herd of over 7000 cows is based there with production profits supporting 300 staff. A further 50 research scientists are funded by the government. Meat technologists and breeding specialists work closely with producers and processors to assess the market value of the work, with meat processors recording carcass data from cattle produced at the centre and returning it to the researchers.

Trial work includes assessing the biological status of many pure breeds of cattle and even more cross-breds. Priority has been to establish breeding and feeding regimes to achieve low input, high output systems to produce beef as cheaply as possible, but to a high and consistent standard of eating quality.

"A key advantage that the US cattle research programme has over the UK effort is a secure, strategic long-term funding programme, with many projects set up with 10-year protocols," explains Mr Fuller.

Work began on rotational cross breeding and composite breeding 15 years ago. Trials have proved that hybrid vigour generated by cross breeding improves traits with low heritability, including fertility, calving difficulty, calf survival, maternal abillity, growth rate, longevity of beef cows and feed efficiency. This leads to an increase of up to 23% of total calf weaning weight above the average merit of the purebred parents, says Mr Fuller.

But fluctuations in breed composition between generations in rotational cross breeding systems are likely to cause considerable variation in performance levels of cows and calves for main traits unless breeds used in the rotation are similar in performance characteristics.

On the other hand, results have shown that composite populations offer a procedure that is more effective than continuous cross breeding for using genetic differences amoung breeds to achieve and maintain optimum performance.

Although composite breeding loses 25% of the hybrid vigour of a first cross, researchers have shown that this is compensated for by enhanced stability and consistency in the composite breeding and slaughter populations.

The centres researchers have also identified those breeds which confer early puberty. This is selected for to achieve two-year first calving to bring heifers quickly into production.

Selecting for improved carcass characteristics contributes to meat yield and eating quality. Their programmes use all these characteristics as components to create a medium sized, low input/high output cow type.

The principle of composite breeding is to select breeds which show advantages in each trait and to cross them together to produce an ideal breed which consistently achieves the best economic performance. "We are a long way from this appraoch to beef breeding in the UK, but we must learn from the detailed US research and its practical application." &#42

Composite-bred calves exhibit much of the hybrid vigour of first crosses.

US BEEF BREEDING

&#8226 Low input/high output.

&#8226 Consistent eating quality.

&#8226 Composite breeding.