Breeding Matters Part IV: Culling for Fertility

The last installment of this series seems to have struck a cord with folks. (Breeding Matters III: Inbreeding vs. Line breeding) There has been much dialogue around the subject, and that is great. Get

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4 thoughts on “Breeding Matters Part IV: Culling for Fertility

  1. Hi Morgan,

    I am the choir of course, but what the hell. I totally agree with your article, and the previous ones also. The only fine point I would add is that if we want full genetic expression we need to understand the impact management and environment has on all our genetic outcomes. Epi-Genetics! I know you know what it is and how in important it is, but I bet that many of the readers don’t understand its significance in the breeding outcomes. It is a relatively new field, and genetic fluidity is controversial, but I have seen it in action in our breeding program. I agree with those that say we shouldn’t pamper cattle, but we do need to manage for good genetic outcomes. When we are feeding that dry cow, she sis building a calf and the eggs in that calf will affect the herd for years–is she getting everything she needs?
    Great articles, keep up the good work! Look forward to more stuff to enjoy!

  2. I am respectfully disagreeing with you, Joe.

    The defects in question have not been “all but eliminated from the breed.” The two defects in question are monitored within registered Angus circles, but many carriers were simply sold into the commercial sector. I watched it happen for three years at sales up and down the Estern Seaboard. The defects haven’t been eliminated but relocated into an un monitored sector of the industry.

    Yes, the 9j9 bull behind Precision was the source of the first identified defect. However, Precision himself is the source of the second identified defect (Neuropathic hydrocephaly) stemming from that lineage. It was determined to be the result of a mutation within the genotype of Prcision 1680 by the folks who developed the tests at University of Illinois.

    As to how communication, honesty and integrity in handling of reports of the advent of these simple recessive, lethal genetic defects’ appearance in rancher’s herds, we have a different recollection of the facts.
    That period of time is still with us. The Angus Association has a vote for their governing board today. There is still ongoing litigation over who knew what and when surrounding these genetic defects in the Angus breed, and there are now suits over falsification of data which informs the algorithms for EPD development.

    I do not dispute the influence of environment on fertility. However, the cattle selected specifically on a fertility basis first and performance basis second (after all you have to have a live calf in order to measure its performance) which have the fewest additional inputs have higher predicted and actual fertility as a population than those which are not selected under the same or similar conditions.

  3. Morgan, heritabilities are measurable things, not sentiments! Fertility is pretty simple to quantify with bred=1 and open=0. When you take a set of a fertility records, it’s clear that a whole lot more of the phenotypic variance is explained by environomental and non-additive genetic variance than by additive (heritable) genetics. That’s not to say that fertility isn’t heritable at all, or that it shouldn’t be selected for. But it’s important to realize that when selecting for a lowly heritable trait (e.g., survival or reproduction), the overwhelming majority of the phenotype is explained by environment and by gene combinations that aren’t passed on to the next generation.

    There are two take-homes from this:
    1) Local adaptation is important, but a breeder can only sell so many cattle to his immediate neighbors. There is no guarantee that what works in one environment will work in another, unless the selection method separates additive genetic from non-additive and environmental factors, and compares animals across environments.
    2) When a low percentage of the variation is explained by additive genetics, this generally means that a higher percentage is explained by gene combination effects. Heterosis is one such effect. Where there is variance, there is opportunity. There is far greater opportunity to improve fertility via crossbreeding than via selection. This point would be a much more appropriate follow-up to your previous articles about linebreeding. Linebreeding’s greatest potential in the area of fertility is in the development of two diverse breed or lines with which to make an F1 cross for commercial application.

    Finally, the comment about Gardiners and Precision 1680 was inaccurate and unprofessional. Much like your Hereford example in an earlier article, recessive defects in that line were not immediately obvious because of avoidance of close breeding for several years. Also, GAR was sending early defective calves to IA State for analysis, and they were being told that the defect was environmental and not genetic. Perhaps they took a false sense of security in what they were being told, but that doesn’t translate to denial. It wasn’t until the spring/summer of 2008, when a commercial producer mated a group of Precision daughters to their half brothers, that it was clear that Precision was a culprit (although 9J9 was the original source). As their fall sale approached that year, there was still no definitive molecular test. In order to present the best knowledge they had at the time, they hired me (I was a graduate student at the time) to calculate carrier probabilities for every animal in the catalog, based on their pedigrees. They later implemented a sale credit program to replace defective animals, and that cost them millions of dollars. The defect was essentially purged from the breed soon after the molecular tests were developed. They had a streak of bad luck, but it was handled with honesty and integrity.

    Joe Emenheiser, PhD
    UVM Extension Livestock Specialist

  4. Morgan, this statement may be your best.

    “Traits such as fertility have been poo pooed as having low heritability. I personally disagree with that sentiment. Fertility is a survival trait in nature, not for the individual but for the species.”

    In the natural world, when cattle were wild, their only purpose was to “survive and reproduce.” It was not for heavy milk production, or for big weaning weights or fast growth or a certain look (mans idea in the show ring) (form followed function in the wild), proper skeletal structure and disease and parasite resistance. This cow had to be easy fleshing to increase fertility and get through winter-dry season-times of drought. Low birth weights and birthing structure, were an absolute necessity. Failure of any one of these traits removed her from the gene pool. That has to be the same method today. Following this method, not all out performance, will bring efficiency and profit.

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