Line 1 Herefords created through linebreeding to ‘fix’ desirable traits
In most instances, inbreeding and linebreeding should be avoided by cattle breeders to prevent the doubling up of “bad” genes, but in some instances can be used as a genetic tool to “fix” a desired trait.
Michael Gonda of the Department of Animal Science at South Dakota State University explains that linebreeding is merely planned inbreeding.
“What the breeder is trying to do is produce progeny that are related to an outstanding ancestor somewhere back in the pedigree. Ideally, they would be only doing this while keeping inbreeding coefficients low,” says Gonda.
Breeders might be trying to double up a certain ancestor, having that individual appear on both sides of the pedigree, but farther back than father-to-daughter mating, siblings, half-siblings or even grandsire-to-granddaughter.
“One humorous definition of the difference between inbreeding and linebreeding is that linebreeding is what we call it when it works, and inbreeding is when it doesn’t,” he says.
Inbreeding is usually considered bad, and linebreeding has been touted as a good tool when selecting for certain genetics.
One advantage to linebreeding is that ranchers can increase the relationship of their animals to a genetically valuable ancestor. By stacking the genes, this enables the linebred individual to transmit more characteristics to its offspring than the other parent, because it possesses more homozygous genes.
“We call this prepotency. This can be valuable to seedstock producers who want to spread the genetics of an outstanding animal throughout their herd,” he explains.
There have been many instances where herds were intentionally inbred or linebred, such as the research project that began in 1934 at the Agricultural Research Service’s (ARS) Fort Keogh Livestock and Range Research Laboratory (LRRL) in Miles City, Mont.
Line 1 Herefords
“This study was done with Hereford cattle, and they ended up with some animals that were more than 40 percent inbred. The Line 1 Herefords are an example of a successful linebreeding program that was able to maintain high relationship coefficients with a common ancestor – Advance Domino 13 – while keeping average inbreeding coefficients relatively low, at less than 10 percent,” says Gonda.
The idea was to create some inbred lines that could later be crossed with unrelated inbred lines as a way for cattlemen to capture more heterosis – or hybrid vigor – and produce a consistent product by crossing inbred lines within a breed. But this vision was never fulfilled and has since been largely supplanted by crossbreeding.
As stated by Sharon Durham, an ARS staff member, in a 2009 article about the Line 1 cattle, this project was started by using two sons of Advance Domino 13, the founding sire for the desired line. The two sons, Advance Domino 20 and Advance Domino 54, were purchased from Fred DeBerard of Kremmling, Colo. and bred to 50 cows purchased from George Miles of Miles City, Mont. Then, the daughters of Advance Domino 20 were bred to his paternal half-sibling, Advance Domino 54, and vice versa.
After those first matings, the Line 1 Hereford cattle were maintained by USDA at Miles City, and they all descend from this foundation.
The actual inbreeding in each generation was kept low because matings between close relatives were avoided. This was a successful linebreeding program in which a high degree of relationship, 39 percent, to the founding sire has been maintained for more than 18 generations.
“Without linebreeding, the relationship to an ancestor 18 generations ago would be less than one one-thousandth of a percent,” stated Durham.
Most of the academic and commercial tests that assess production characteristics of individual bulls can be traced to this original research with Line 1 cattle.
Things like length of feeding period and number of animals required to measure economy of gain in progeny testing were pioneered in the development of Line 1 cattle and are now part of the Beef Improvement Federation Guidelines for Uniform Beef Improvement Programs.
Data from Line 1 animals also contributed to the first estimates of heritability and genetic correlation for beef cattle.
The genetic work with Line 1 also contributed greatly to our understanding of maternal genetic effects in beef cattle. The influence of a cow’s milk production on the growth of her calf is one example.
“Early on, it was established that inbreeding could have detrimental effects on production efficiency. Crossing Line 1 with other inbred lines of Hereford cattle provided some of the first estimates of heterosis for beef cattle. These early results were complemented by the later observation that heterosis fully offset negative effects of inbreeding,” Durham stated.
Hereford breeders and commercial beef producers have purchased Line 1 cattle for more than 65 years for use in their own herds.
Today, direct descendants of the Line 1 Hereford cattle bred at Fort Keogh are found in almost every state and several foreign countries. More than half of all Herefords recorded in the United States today trace part of their ancestry to Line 1.
Mating close relatives in the Line 1 program provided a continuous test for the presence of harmful recessive genes.
“Thus, ARS provided a secure source of germplasm when the Hereford breed has run into problems with genetic defects such as dwarfism and epilepsy,” continued Durham.
The Line 1 cattle have also provided several unique opportunities for genetic research.
As stated by Durham, the increased genetic uniformity resulting from long-term linebreeding makes genome sequences easier to assemble. This positioned the Line 1 Hereford cattle for contributions in future research. A Line 1 bull was selected to make a widely used genomic library, and DNA from a Line 1 cow was the foundation of the recently completed bovine genome sequence.
Heather Smith Thomas is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to firstname.lastname@example.org.