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  • Jeff M Chambers

"Silver Maple Dexters, why not polled?"

We have been asked this question many times over the years, and we are pleased to provide our reasons for not using polled genetics.

 

We do not prefer horns, although Dexter's horns are beautiful. See the photo of our first Dexter bull, Rainbow Hills Big Mac, insert. We have kept and shown Dexters with horns on for years but have dehorned all SMD stock since 2005.

 

We prefer not to have polled genetics. We have made that choice for multiple reasons.

 

First, since we brought Dexters on the farm 25 years ago, our breeding program has focused on producing high-quality, functional cattle for small farms that meet a dual-purpose conformation standard and are true to the Dexter breed standard[i]. Then and now SMD’s focus has been and continues to be improving multiple conformation and production traits.  Our selection and breeding decisions are based on these focus areas, nothing more. At no time in our selection of genetics to improve the areas of focus in our herd was there an intersection with polled stock. In 2024, we have, with humility but many years of hard effort, consistent focus, more than a few setbacks, and some degree of luck, achieved a level of excellence in conformation, type, and dual-purpose production that, in our assessment, the introduction of polled genetics would result in moving our herd in the wrong direction.

Specifically:

1.      We do not observe consistent quality udder traits, including attachment (fore and rear), udder capacity, and rear udder height and width.  We observe a high incidence of "ball udders."  

2.      We do not observe consistent breed conformation in type and breed character.  

3.      We do not observe consistent expression of depth, width, and spring.  

4.      We have observed a very high incidence of preputial prolapse.

 

None of this is to suggest that there are no excellent examples of Dexters with polled genetics; to the contrary, there are many. This also does not suggest that horned Dexters, by virtue of not having polled genetics, are superior or without fault. What is stated is that we do not see the ability to improve our herd from their use.  Further, as the following reasons explain, a breeder’s ability to access a broader range of genetics to improve stock is limited when using polled genetics.

 

Second, all the polled Dexter genetics in the national U.S. Dexter herd are derived from a single bull. The Dexter breed is a small population breed with a limited genetic pool in the US and worldwide. Many breeders in the US have and continue to focus on polled and, more specifically, producing homozygous polled animals, further stacking a single animal and its genetics in all pedigrees. Such concentration of an already limited gene pool back to a single animal is problematic for the continued improvement of the breed. It becomes even more problematic when a single on/off gene is used as a primary selection factor within a breeder's herd.

 

More directly, if everyone uses a single bull's genetics and line breeds multiple times to that bull, generation after generation, with the primary selection of a single trait, a constructive breeder's ability to improve their animals using those same genetics, generation after generation, is significantly hindered.  The genetic pool and opportunities become fixed with little to no variability.  This phenomenon, which is a selection-based founder effect[ii], results in the same outcome as a genetic bottleneck[iii], as if the population crashed, which severely limits the genetic variation available within a population.  As a result, improving the more complex and essential breed and dual-purpose production traits without genetic variation becomes increasingly difficult, if not impossible.   

 

The founder effect created through the widespread selection and linebreeding to a single bull has and will continue to create genetic drift[iv]. SMD’s breeding focus is on genotypic herd improvement with a mind to this year, next year, and every year thereafter.   Horns can be removed genetically with one breeding; a 90+ score classification animal, a superior udder, or a herd with exemplar Dexter type may take skillful breeding over many years or consume the entirety of a breeder’s lifetime if attained at all.

 

Third, with the reduction in genetic variability created within the US Dexter herd focused on polled, there is now and will be an ever-increasing need to reach outside that very restricted gene pool for other Dexter genetics to facilitate breed and herd improvement and maintain or return to breed type.  Our herd provides a breed standard, high-quality dual-purpose genetic ‘off-ramp’ or outlet now and into the future as a genetic resource to offset the current Dexter breeds’ genetic drift through founder effects in the rush to homozygous polled.

 

Fourth, the polled trait in Dexters did not come from a spontaneous mutation, nor did the polled gene "hide" for a century in the Dexter breed before "re-appearing." The polled Dexter is derived from an outcross with other polled breeds in the UK. We are not purity absolutists, believing SMD or anyone else's Dexters are the 100% epitome of purity. On the contrary, we accept some introgression of other breeds and acknowledge it in the SMD herd. Most notably, the UK Dexter Cattle Society had, during the '60s and '70s, a UK Dexter Society sanctioned and experimental breeding program in a well-meaning but misguided effort to eradicate the chondrodysplasia gene. Angus, Shorthorn, Jersey, and other breed crosses were used in that program. In the experimental program and Appendix registry, however, only after moving through Appendix A, B, and C listings with breeding back to full UK Dexter Cattle Society bulls were animals from the Appendix registry allowed entry into the UK Dexter Cattle Society full pedigree registry. The polled gene in Dexters came through this process; before that, there were no registered polled Dexters.   Either a mistake was made in the process of upgrading to allow a non-breed standard trait animal to advance through the Appendix registries, or there was an intentional allowance of non-breed standard characteristics wholly inconsistent with the breed standard of the time. Before this mistake or intentional allowance, the UK Dexter Breed standard was "Horns: Moderately thick, with an inward, upward curve. Removal of horns will not be penalized in the show ring." After the polled cross was accepted, the following was added: "Polled animals are acceptable but must be notified in writing." 

 

These are the reasons we do not use polled genetics in our Silver Maple Dexter herd. We are not disparaging other breeders' efforts or herds, discouraging others from using polled Dexter genetics, or promoting SMD stock through this response. We are stating Silver Maple Dexter’s reasons for not using polled genetics in the past and why SMD will not incorporate polled genetics into our herd.

 

[i] SMD uses the UK Dexter Cattle Society Breed Standard as our standard.   The ADCA does not provide a breed standard, only a guideline.   Purebred livestock breeders must breed to a standard, not a suggestion.  SMD is a member of the UK Dexter Cattle Society and the American Dexter Cattle Association.

 

[ii] In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. A founder effect can account for the presence of an allele at an unusually high frequency in an isolated population if the allele is selectively neutral and if all copies are identical by descent with a copy that was carried by a founder individual.

 

[iii] Genetic bottlenecks are events that limit genetic variation in a population and result in founding populations that can lead to genetic drift.  Most often, this is in the context of a population crash, but selection can also create genetic bottlenecks.

 

[iv] Genetic drift is the change in frequency of an existing gene variant in the population due to random chance. Genetic drift may cause gene variants to disappear completely, reducing genetic variation. It could also cause initially rare alleles to become much more frequent and even fixed. 

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