Comparison of early- and late-maturing suckler bred bulls

The View from Teagasc: Suckler bull production systems were traditionally based on high concentrate diets. Lowering the cost of suckler bull production systems through the incorporation of grazed pasture during the growing-finishing phase is being evaluated at Grange.

A perceived challenge for these systems may be to achieve adequate carcass fat cover at ayoung slaughter age. Although progeny from the suckler herd are predominantly sired by late-maturing breed types, progeny sired by early-maturing breeds may be more suitableto grass-based suckler bull production systems.

Ongoing studies at Grange aim to determine growth and carcass characteristics of suckled male animals sired by either lateor early-maturing sires and finished in contrasting production systems.

Recent study

Some 90 spring-born early-maturing (AberdeenAngus- and Hereford-sired) and 120 springborn late-maturing (Charolais- and Limousinsired) weanling bulls out of predominantly late-maturing suckler cows, were used in a study to compare the two maturity groups in two production systems, and within each system animals were taken to a range of carcass weights.

The two production systems were: (1) ad-libitum concentrates plus grass silage; and, (2) grass silage plus 2kg concentrate daily for the first winter (~125-day duration), followed by 100 days at pasture and then an indoor finishing period on ad-libitum concentrates (plus grass silage).

Bulls were taken to carcass weights of approximately 340, 380 and 420kg.

Results

When comparing early- to late-sired bulls, to achieve the same carcass weight, the earlysired animals needed a higher slaughter weight, their kill-out proportion was lower,
carcass conformation score lower and fat score higher. Age at slaughter was 518 and
477 days for early- and late-maturing bulls, respectively. On production systems, to
achieve similar carcass weight, the ad-libitum concentrate-fed animals were associated with
lower slaughter weight (could be killed lighter and younger), higher kill-out
proportion and fatter carcasses.

Increasing carcass weight was associated with higher kill-out proportion, better carcass
conformation and increased fatness. During the first winter (as weanlings), silage intake,
total dry matter intake, average daily gain and feed conversion ratio did not differ
between early- and late-maturity bulls. At pasture, average daily gain was higher for the
late-maturing bulls. During the indoor finishing phase, the early-maturing bulls had
lower silage dry matter intake and higher concentrate intake, but total dry matter
intake was similar. Feed efficiency decreased with increasing carcass weight.

By EG O’Riordan. Marren, M McGee, AP Moloney
Teagasc, Grange, Dunsany, Co Meath

Pictured generic suckler herd. Photo O’Gorman Photography

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