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The US cattle industry is characterized by a considerable genetic diversity
and variation. There are a large number of cattle breeds representing
significant differences in biological type and characteristics of mature
size, milk production, muscling, fat deposition, color, behavior, etc. This
proliferation of cattle breeds and types peaked in the 1970 and 1980s, with
numerous importations of cattle from European regions which had been
selectively bred and developed for unique traits and attributes for years.
Through promotional efforts, a desire to change cattle
genetics for increased growth, and the knowledge of production benefits from
crossbreeding, many hybrids or crossbred cattle where bred. To expand
numbers from a limited imported base, upgrading was common, (utilizing a
traditional Angus or Hereford base), for several generations until purebreds
were achieved. Through this time and process many half-blood, three
quarter-blood, and seven-eight blood bulls were used by commercial
producers. As breed populations and numbers increased, hybrid bull offerings
were largely replaced with purebreds, considerable to be more predictable,
were better evaluated though genetic evaluation programs, and more easily
promoted on breed strengths.
At a point in time with many well established breeds of
substantial numbers competing for the commercial producers bull buying
dollars, the focus is on utilizing available genetic resources to achieve
production efficiencies and meet market demands. It’s recognized there are
situations of too much and not enough and a better realization of what may
be optimal for profitability. There are situations of cows that are too big,
milk too little or too heavy, and calves that may be too lean at acceptable
market weights, those that fatten to light, those without adequate muscle to
yield well, and a market driven target for marbling and a penalty for the
wrong kind. Furthermore, there is value for consistency, and predictability
for both herd and feedlot management and product marketing.
Crossbreeding continues to offer solutions and benefits
for cattle production. Research supports crossbred cows of adapted breeds
and types will likely achieve the equivalent in pounds calf weaned of an
additional calf is their lifetime from the cumulative effects on fertility,
calf survival, weaning weight, and longevity in the herd. One of the best
strategies to deal with the antagonism of carcass grade and yield and
feedlot gain with appropriate finish weights is to blend breeds with a
strength for marbling and muscling. A preferred target for many cattle
feeders selling under a grid with a substantial choice select spread is for
calves with an Angus base and a bit of continental breed blood.
Many producers who had crossbred herds with a fairly
high percentage of continental breeding have achieved this goal by heavy use
of Angus bulls over the past generation. However, by retaining their own
replacements they may now find themselves almost back to producing purebred
cattle. The trend has been away from crossbreeding and a narrowing of the
genetic diversity as many breeds have had a declining share of the market
and with breed types tending to move closer together. Traditional
crossbreeding schemes include rotational and terminal crossing. Rotational
crossing entails mating females sired by one breed to another breed;
therefore requiring cow identification and segregated breeding pastures. It
also results in considerable diversity in the calf crop as calves will be by
two differing sire breeds. A terminal system offers a lot of theoretical
advantages as a uniform herd of a single cross or breed type of cows matched
to the feed and resources base can be mated to a sire breed to best
compliment to match the feeders and packers needs. This system doesn’t
generate its own replacement females which creates the complication of
sourcing quality females and cash flowing their purchase.
An alternative to get to a similar point of capturing a
substantial level of heterosis in the cow herd and blending breeds for the
strengths and to mask weakness, is to utilize hybrid or composite bulls. In
general the term hybrid is used to describe crossbred parents and composites
are the result of mating among crossbred parents. By utilizing crossbred
bulls the herd can be managed very simply breeding as if purebred without a
need to segregate cows by sire breed or sourcing outside replacements. After
a period of years the breed percentages represented in the composite will
stabilize and heterosis will be sustained at about 50% of potential for a 2
breed composite and 60 to 75% for a four breed composite depending on the
percentage individual breeds are represented in the four breed composite.
While there are concerns and constraints associated
with using hybrid and composite bulls, availability and use seems to be
increasing significantly with research data, breeder promotion, and
advancing genetic evaluation technology. Many bull sales in the northern
plains now feature hybrid bulls, often finding strong market acceptance by
producers. Breeding research with composites at the Meat Animal Research
Center have found little differences between purebred and three MARC
composite lines for variation in measured reproduction, production or
carcass traits. Data collected on composite sired calves at the university
on Nebraska teaching herd has further illustrated the value of blending of
breed types in hitting both marbling and yield targets of finished steers,
with 87% USDA choice or better with 66% yield grade 1 and 2.
The confounding effect of heterosis on an individual
bull’s performance record and the lack of accurate EPD’s has and continues
to be a concern. The adoption of multiple breed evaluations and cooperation
amongst some breed associations to produce EPDs on a single base with
appropriate adjustments for heterosis and utilization of genetic information
on purebred parents are moving forward and will make it easier for genetic
evaluation of hybrids.
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