Page 106 - NZ Herefords Magazine 2018

Industry Focus

Tools of the trade – crossbreeding

WORDS SOUTHERN BEEF TECHNOLOGY SERVICES

CAREFULLY PLANNED AND WELL-MANAGED CROSSBREEDING SYSTEMS
OFFER THE POTENTIAL TO DELIVER SIGNIFICANT BENEFITS TO BEEF PRODUCERS.
THE MAIN BENEFITS RESULT FROM:
• ADDITIONAL PERFORMANCE AS A RESULT OF HYBRID VIGOUR (ALSO KNOWN AS HETEROSIS).
• THE ABILITY TO COMBINE THE BENEFITS OF DIFFERENT BREEDS (ALSO KNOWN AS BREED
COMPLEMENTARITY).

Heterosis or Hybrid Vigour 20 23.3
= extra performance above mid-parent mean.
• Showing 10kg (or 5%) hybrid vigour *Results were obtained from to dam being a
an experiment involving all M = Maternal heterosis due crossbred.
relevant crosses among
Hereford, Angus and 14.8
Shorthorn cattle.
PERFORMANCE / KG BREED B 230kg BREED A INCREASE % 10 8.5 I = Individual heterosis due to the turnoff animal being a crossbred
Source: Breeding for Profit,
QE 93015, DPI, Qld, 1993.

A x B
22Okg
22Okg

0 8.5

Straightbred Straightbred X-bred
Figure 1 – Example of hybrid vigour for weaning weight. cows cows cows
Straightbred X-bred X-bred
calves calves calves
Figure 2 – Responses in weaning weight per cow mated.
HYBRID VIGOUR (OR HETEROSIS)

Hybrid vigour is the amount by which the performance of Reproduction and maternal traits have low heritability and
the crossbred animals exceeds (or differs from) the average the traditional response to selection in breeding programmes
performance of the purebred parents that are used in the cross. will generally be slower compared with high heritability traits. At
An example of this for weaning weight is demonstrated in Figure 1. the same time however, significant improvement in these traits
The results of a crossbreeding trial using Hereford, Angus can be made through programmes that maximise heterosis.
and Shorthorn cattle in Southern Queensland are demonstrated The inverse is true with carcase traits. Significant and rapid
in Figure 2. Compared with the straightbred calves, the F1 progress can be made through selection for carcase traits in
crossbred calves showed an 8.5% increase on average in a breeding programme, while crossbreeding has little or no
weaning weight per cow mated. While significant, a larger heterosis effect. Growth traits are moderate for both heritability
increase of 23.3% was observed in the F2 calves, being those and heterosis, making progress possible through both selection
calves bred from F1 cows. The additional ‘boost’ was obtained and crossbreeding.
from maternal heterosis. The amount of hybrid vigour achieved will depend on the
Importantly, heterosis is not just observed for weaning type of crossbreeding or composite system implemented. A
weight but also in many economically important beef cattle composite breeding programme is a crossbreeding system that
production traits, especially in traits of low heritability such as is stabilised (inter-mating the crossbreds).
reproduction and adaptability traits. Figure 4 lists the types of crossbreeding systems, the levels
Figure 3 illustrates the relationship between heritability and of hybrid vigour (both individual and maternal) retained, and
heterosis for different categories of beef cattle traits. estimates of increases in weaning weight per cow mated.
To reiterate, to fully benefit from hybrid vigour the cow
herd should also be crossbred to take advantage of maternal
TRAITS HERITABILITY HETEROSIS
heterosis. Crossbred cows when compared with purebred
FERTILITY, MOTHERING ABILITY, females will generally have:
CALF SURVIVAL LOW HIGH • Increased conception rates
BIRTH & WEANING WEIGHT, MILK MEDIUM MEDIUM
• Improved calving ease
CARCASE HIGH LOW • Increased percentage of calves weaned
Figure 3 – Comparison of trait heritability and heterosis. • A longer production life (i.e. longevity).
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