Last month I wrote that the most important attribute of the Brahman breed was not the high levels hybrid vigor of their crossbred offspring but its breeding value of transmittable characteristics as purebreds (and crossbreds).
I know that comes as a surprise, after all even the lowest performing animals of two different breeds can produce a generally superior performing crossbred animal when compared to its parents, but that superiority is transitory, it is not reproducible in the next generation and in fact will be halved.
Breeding value is the influence that an animal’s genetics have on a specific trait. It is never known with complete certainty, but it can be estimated using accurate pedigrees and performance records for the trait that are collected from the individual, its parents and progeny, and other relatives. Bulls will have estimated breeding values with higher accuracies than cows, but not necessarily higher breeding values, due to differences in numbers of off spring produced.
These estimated breeding values are the Expected Progeny Differences in the ABBA National Cattle Evaluation. Using EPD for selection is seven to nine times more effective than selection based on the actual record (birth weight, adjusted weaning weight, carcass merit ultrasound, etc.)! However, breeding value is also the sum total of the genetic effects of the breed.
A breed must be outstanding in its overall genetic contribution. Just as the effects of hybrid vigor are cumulative in the life of an individual, so too are breed effects. A breed does not have to be outstanding in every trait; no breed has ever attained that though many have claimed to, but there must be outstanding traits that can be selected for use as a purebred too.
If a breed could only justifiably be raised to only produce crossbreds, how many breeding animals would be needed with today’s advanced reproductive technology? The genome of the bovine breeds is remarkably similar (maybe more than 95%), regardless of where they originated. Th e physical differences between the breeds are major but likely controlled by only a few hundred or thousand genes (or gene interactions) and their products. Genes are divided into two main groups based on their mode of action, dominance or additive.
Dominance is when a gene or gene product masks or shuts down its (recessive) paired gene (allele). Dominance provides polledness and coat color to Brahmans (among other traits). The other gene action is called additive because the genes selected act additively (like stacking bricks) to increase (or decrease) the level of a trait through selection. Most of the traits we measure in reproduction, growth, carcass, etc. are caused by additive gene action. Additive gene action is what EPD measures. What are the breed effects of the Brahman breed? Most would point out high heat and humidity adaptation, parasite tolerance, disease resistance, and longevity on the plus side to cite some of the negatives (excitability, later puberty, higher birthweights when bred to Bos taurus cows, lowered feedyard gains, and lower carcass merit, etc.). All of these traits are due to additive gene action and can be selected for (or against) very effectively by the use of EPD. None of these are all or none traits (like pregnancy – she is either pregnant or not), they can be measured on a scale that goes from the absolute best to the absolute worst in the breed.
Every Brahman has genes that control all of these (and more). Lacking the ability to actually be able to identify the genes (or combinations) that affect these traits, we use the next best tool – records. ABBA members are fortunate that they have EPD, even if some may question the validity of the results of given animals. Within a herd, the EPDs will certainly correctly rank all of the animals in the herd if you ensure the accurate parentage and proper and timely collection of your animals records.
Trusting other breeders to do the same, and trust is critical when sharing data including EPD, selection progress will be made and more quickly that selection based on records alone. Although the discussion has been about purebreds, crossbred individuals have the same gene action and can have calculated EPD and Accuracy values for the same traits as the purebreds if the effect of hybrid vigor on the trait could be determined
The average of the parental EPDs would be a close estimate if the accuracies were high, but in most cases they are not. Parental averages (with a “fudge factor”) were used in early National Cattle Evaluations to estimate EPD for animals without any records. In fact it was widely used in some purebred breeds to provide an idea of the performance of potential matings. If the dam had no EPD data, then the dam’s sire EPD was weighted by 25% to make comparisons. This was not too far from the actual early EPD models themselves when there was very little dam information to calculate their EPD.
There is a table of adjustments provided by the US Meat Animal Research Center in Clay Center, NE, on the Beef Improvement Federation website that provides adjustments to compare bulls of different breeds that might be used in a cross, and it is useful when choosing different breeds of bulls for Golden and Certified Brahman F1 female production.
See page 14 of this magazine. Of course, the center is located in Nebraska so the breed of sire averages may not mean much in the South or South east but Brahmans do very well. Birth weight is high but these bulls are mated to Bos taurus females who are fed all winter so it is expected that it would be high. Recently Dr. Bailey Engle at USMARC reached out to several Brahman breeders for semen on their more widely used bulls and many of you responded with generous donations; Brahmans do and will continue to have a place in their research. Thank you!
