Crossbreeding: Myths & Truths

This report delves into the complexities of cattle crossbreeding, addressing common myths and truths surrounding the practice. It examines the benefits of crossbreeding, such as heterosis (hybrid vigor) and breed complementarity, which lead to improved biomass, fertility, and weaning weight in calves. The report refutes the myth that crossbreeding significantly increases calf birth weight, citing research showing a modest increase of only 1-1.5 pounds. It clarifies that greater genetic distance between parental breeds results in higher heterosis, and that heterosis isn't limited to the first generation of crossbreeding. The report also debunks the myths that heterosis occurs within breeds and that carcass traits benefit more from crossbreeding than reproductive traits. Finally, it acknowledges limitations of crossbreeding, such as the potential for weaknesses from parental breeds and the challenges of maintaining rotational crossbreeding programs. The report concludes by emphasizing the advantages of crossbreeding over inbreeding for producing healthier and higher-quality calves.

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Crossbreeding: Myths & Truths
17th July 2019
Crossbreeding is a process which encompasses a significant amount of debate and
discussion within the domain of cattle business around the world. Crossbreeding is a process that
is of significant interest to the beef producers and there are some myths and truths that are
associated with the phenomenon of crossbreeding which is being undertaken on a wide scale in
the modern cattle industry around the world.
Crossbreeding has benefits: Truth
It can be said that crossbreeding has several benefits such as a process known as
heterosis. Heterosis can be defined as a phenomenon where a progeny of several varieties of a
species or crosses between various species of cattle demonstrate increased biomass,
developmental speed, and rate of fertility as compared to both the parents. The other major
advantage crossbreeding is the element of breed complementarity. According to historical pieces
of evidence, heterosis or hybrid vigor can be considered to be a positive result generating from
the act of crossbreeding cattle as a crossbred animal has superiority in comparison with the
average of its parents that are straight-bred. An enhancement in the weaning weight of cattle is
one of the positive outcomes of crossbreeding.
In recent times, discussions on crossbreeding have included the references to breed
complementarity which is the process of considering two diverse breeds and pairing them to
complement the major and the core traits of each of the breeds. The main objective of
crossbreeding is to emphasize each other's strengths and weaknesses concerning the different
breeds of cattle. The purpose of cross-breeding two animals is to develop upon the strengths of
each of the animals. For instance, if there is a lack of muscling in one breed, then it can be
overcome by the strong muscling feature in another breed. In other words, crossbreeding is all
about developing a breed of cattle where the strong features of one breed complement the weak
features of the other breed for achieving the final objective of producing a healthy breed of
cattle.
It is interesting to know that there is significant popularity of inbreeding by some of the
cattle breeders around the world, like in North America, where there is a high level of popularity

of inbreeding among the breeds of cattle that are purebred. Inbreeding is successfully managed
with the help of various mating programs. However, today a large number of dairy producers are
getting more inclined towards crossbreeding due to some of the negative outcomes of inbreeding
such as a reduction in fat, milk and protein production, greater counts of somatic cell, and
increase in the cases of dystocia or difficulty in the birth of calves and instances of stillbirths.
Crossbreeding counters all these problems by contributing towards reducing birth weights of
calves, enhancement in the levels of fat and protein, making it possible for the older facilities to
accommodate the moderate-sized cattle, and lowering inbreeding by using purebred sires for
undertaking to crossbreed on the herd of cattle.
Crossbreeding is responsible for a significant increase in calf birth weight: Myth
It is often alleged that crossbreeding in cattle results in a significant increase in the birth
weight of calves. According to a research conducted by the Meat Animal Research Centre or
MARC, on over 25000 breeding or calves for some of the most reputed beef breeds and their
crosses in the US, the effects of heterosis on the birth weight, weaning weight and yearling
weight has been analyzed between several breeds like British with British; Continental with
British and Continental with Continental. It was found in the study that the average enhancement
in the birth weight of the calves was around 1-1.5 pounds as a result of heterosis. Therefore,
crossbreeding does not increase the birth weight of calves by a significant volume as often
believed to be.
We know that crossbreeding increases weight of calves in respect of the first-generation
crossbreds. The weights of the calves that are born through crossbreeding are found to be more
than the purebred calves. The birth weight of calves is generally not much of a concern for the
cattle breeders. It is during situations where the calves are very large and the cows are having
difficulty in calving or it is during those situations where the calves are born very small in size or
weak in health that the cattle breeders become concerned about the birth weight of the calves. So,
the birth weight of calves born through crossbreeding will be more than those born through pure
breeds. However, the notion that the increase in the weight of the calves due to crossbreeding is
detrimental to the future of the calves is a myth because the increase in weight is not something
that is of too much concern. The weight only increases by a little margin that does not cause any
harm to the future of the cattle.

The greater the genetic distance of the parental breeds, the more is the amount of heterosis:
Truth
It is evident from several research studies that the more divergent the parental breeds of
cattle are, the greater will be the heterosis. So, a beef producer will be able to see more heterosis
that will lead to a more healthy calf that will result from the mating of two extremely divergent
parents. The process of heterosis occurs from the combinations of various alleles that are
considered as forms of a gene. These are gained from the breeds of the parents that enhances the
heterozygosity at several places in the genome and it contributes to the recovery of the
individuals from depression generating out of inbreeding. For example, crosses of cattle from
British breeds such as Hereford and Angus might result in a relatively lesser degree of heterosis
as compared to a cross between British and Continental breeds. Furthermore, a cross between a
Bos taurus and a Bos indicus will result in more heterosis as compared to crosses belonging to
the breeds of Bos taurus.
We now know that the British breeds of cattle are more closely related to one another as
compared to the Continental European breeds. It is interesting to learn that these breeds have
diverged from one another around 100-200 years ago. Based on currently available data it is
determined that Bos Taurus breed has diverged from Bos indicus breed around 80,000 to 1,
00,000 years ago and due to this, the two groups have become genetically distant. The genetic
distance of the parents in the cattle is often considered to be an important factor for many of the
cattle breeders because they want to ensure that the health of the calves that are born are in good
condition and at the same time the birth weight of the calves are expected. Heterosis is desired in
crossbreeding because it results in much healthier calves that are born from the parents. So, it is
desirable by the dairy farmers that there is a bigger genetic distance between the parental breeds
of cattle so that the amount of heterosis is more that leads to the birth of healthier cattle.
Heterosis is present only in the first generation of crossbreeding: Myth
There is a notion that heterosis exists only in the case of the first generation of
crossbreeding. It is found that when there is mating between two straight -bred animals that are
of diverse breeds, at the time of the first cross there will be heterosis. But the mating of an F1

with two F1 crosses where F1 cattle happened to be the offspring from the initial cross along
with similar breed composition will create 50% heterosis in the process of mating. Furthermore,
when there is the mating of two crossbred cattle there is a tendency of retention of some of the
heterosis. But, the volume of heterosis that will be retained will be diverse for diverse
crossbreeding systems that depend on the system and also the number of breeds that are
involved. Hence, heterosis is not present only in the first generation of crossbreeding.
There are positive effects of the individual genes from the several breeds that are used in
crossbreeding. It is found that the dairy crossbreeding producers receive an enhanced
performance due to the occurrence of heterosis. In genetics, heterosis is also referred to as hybrid
vigor. It is found that even after the first generation of crossbreeding, heterosis leads to an
increased gain which is more than the average of the genetic level of the two-parent breeds of
cattle. The bonus that is gained from heterosis encompasses around 5% for production and 10%
for health, survival, fertility, and mortality. So, the effect of heterosis is evident even after the
first generation of crossbreeding. Therefore, the dairy farmers should not believe in myths which
say that heterosis can only be observed in the first generation of crossbreeding.
Crossbreeding helps to eliminate the several concerns of the dairy farmers related to
inbreeding. If the breeds that are to be used in crossbreeding chosen effectively then, the impacts
of heterosis are found to be opposite to the impacts of inbreeding depression. Heterosis leads to
you an extra advantage on the parent breed advantage and can be considered to be highly
valuable for various traits like health, vitality, disease resistance and fertility. Effective
crossbreeding is undertaken through mating two of the superior breeds of cattle. To take the
effects of heterosis to the next generation the breeds must be able to effectively complement each
other and independently they must have substantial selection base for continuing the unique
breeding goals.
Cross between unrelated lines in a breed causes heterosis: Myth
Heterosis does not occur when mating is conducted within breeds. It happens only at the
time when there is the mating of cattle from two or more breeds. For instance, when there is a
cross between Hereford x Hereford then there will not be any heterosis. Research studies indicate
that heterosis occurs when there is the crossing of a British cattle with a Continental cattle or
with a Bos indicus cattle. Hybrids are found to be more heterogeneous as compared to their

parents. A reduction in the number of heterozygotes leads to a situation where there is an
increase in the number of homozygotes. The mutants which are most recessive happen to be
deleterious. Hence the inbred lines are caused to be weakened due to possessing an increment in
the number of homozygous recessive genes. Hybrids are stronger because the recessive genes
from each of the parents are usually hidden by the dominant genes from the other. The hybrids
become even more heterozygous as compared to their parents and this is increased even more
when there is a greater divergence in the parents. The contrast appears to be the most at the time
when the parents happen to be highly homozygous inbred lines.
In the case of species that are closely related, an enhancement in the growth or stature of
the hybrids is accompanied most of the times by problems of fertility such as sterility in the
hybrids. In respect of the interspecific crosses where the parents of the cattle are secured from
the wild and non-inbred populations, the complementation process of deleterious recessive
alleles cannot be held responsible for creating heterosis or hybrid vigor. We can say that there is
a lack of effective understanding of the concept of hybrid vigor for heterosis regarding the
interspecific hybrids. However, it is agreed that the reciprocal crosses that are made between
species which are closely related results heterosis or hybrid vigor in one direction only but not in
the case of the reciprocal cross.
The carcass traits receive more benefit from crossbreeding as compared to reproduction
traits: Myth
According to beef research conducted worldwide, it is found that the degree of
heritability and heterosis are related to each other in an inverse manner. So, the highly heritable
traits become the opposite when benefits from heterosis are concerned. Carcass performance will
gain advantage from the process of cross-breeding if more benefits are derived by focusing more
on the complementarity of the breed as compared to heterosis. The reproductive traits are very
significant to the dairy farmers that produce calves from cows. These reproductive traits are
lowly heritable and therefore, they gain substantial benefits from heterosis. There is a lot of other
things to crossbreeding rather than just the process of heterosis. This can be attributed to the
several advantages that come to the cattle breeders through breed complementarity.
The focus lies on the major strengths of each of the breeds and letting the core strengths
complement each other in respect of the two breeds that are used in the process of cross-

breeding. The ultimate objective is to achieve an optimized level of performance. The cattle
produce can increase the results of crossbreeding by taking the advantage of traits that are
economically important such as the reproduction and fertility of the cattle that benefit
significantly from the process of heterosis but they are lowly heritable and they are utilizing
breed complementarity along with EPDs for gaining benefit from the traits that are even more
highly heritable.
We now understand that crossbreeding is one of the most popular techniques that are
undertaken by the modern cattle breeders to enhance the quality of the calves produced.
Inbreeding is found to diminish the quality of the calves that are born and due to the several
disadvantages of inbreeding which impact the life of the cattle and the quality of the meat
received from such a cattle the modern cattle producers are in favor of undertaking crossbreeding
because the process helps to produce healthy calves. Hence, crossbreeding is recommended by
most of the cattle breeders and it is to be remembered that the distance is the genetic composition
of the parental breeds there will be enhanced heterosis and hybrid vigor in the calves that are
born. Hybrid vigor or heterosis is a desirable phenomenon that ensures much better health and
physical attributes of cattle as they grow up and become ready to either produce milk or to give
meat.
Finally, it is important to learn about some of the disadvantages of crossbreeding. Some
of the limitations of the process at that the crossbreeds that are produced from such a process
show the weakness of the breeds from which they are born and the process of heterosis in the
initial process reduces with backcrossing of the parental breeds. The crossbreeding plans which
are considered to be rotational and specifically, those with three breeds have the potential to
observe considerable heterosis. However, it is difficult to maintain our rotational crossbreeding
program as it needs prudent and effective Record-Keeping and planning. Therefore, it is to be
remembered that when the process of crossbreeding is undertaken in respect of early generation
crosses there can be some diversity regarding the size and body conditions of the curves
depending upon the breeds.