As usual, Canadian Dairy Network (CDN) held its semi-annual Open Industry Session, which took place at the hotel Le Dauphin in Drummondville, Quebec. The following is a summary of the discussions and recommendations resulting from the Genetic Evaluation Board (GEB) meeting held the next day, on Thursday, October 26, 2017. The CDN Board of Directors will consider these recommendations for approval at its meeting on December 11, 2017.
- Given the previous decision to introduce official evaluations for Digital Dermatitis (DD) in the Holstein breed effective December 2017, the GEB made the following additional recommendations:
- With the use of a single step model for estimating genomic evaluations for Digital
Dermatitis, the output is a Genomic Estimated Breeding Value (GEBV) for genotyped
females with data and their genotyped ancestors. For this reason, no traditional
evaluations excluding any genomic information are estimated and no Direct Genomic
Values (DGV) will be published.
- Minimum criteria for labelling sires with an official evaluation for Digital Dermatitis must therefore be based on evaluations that include genomic information, which yields higher Reliability values. The GEB subsequently recommended that all bulls with at least 70% Reliability and daughters from at least five herds with hoof trimmer data be labelled with an official evaluation.
- CDN continue to work with CanWest DHI and Valacta towards the implementation of a new DHI herd management report associated with hoof health as well as an industry wise communication plan for promoting the collection of this data and the value of the new genetic evaluations for Digital Dermatitis.
- Also effective the December 2017 release, or as soon as possible thereafter, the GEB
recommended that CDN publish the Carrier Probabilities for AH2 on its web site, which is the newest haplotype affecting fertility discovered in the Ayrshire breed. Based on University of Guelph research, AH2 has a negative impact on 56-day non-return rate whereas AH1 has an effect on stillbirth rate instead. One-quarter of pregnancies between two carrier animals are expected to be affected so the easiest strategy to minimize the negative consequences is to avoid mating a carrier sire to a female that has a Carrier Probability greater than 10%.
- Given the popular usage by producers of the Inbreeding Calculator tool on the CDN web site and the growing market share of genomic young bulls offered by A.I. organizations, the GEB recommended that the default setting for genomic young bulls to be included be changed, as soon as possible, to be limited to only those that are labelled as actively marketed in Canada and are at least 11 months of age.
- Given the recent changes to the classification program offered by Holstein Canada for all breeds, the GEB recommended that CDN immediately implement the proposed strategy of using Udder Floor linear scores for continuing to assess Tilt and Reverse Tilt as defective characteristics in all breeds. Once enough data exists for CDN to provide genetic evaluations for Udder Floor as an additional type trait, then publication of these associated defective characteristics will be terminated.
- Following the successful submission of Canadian Milking Shorthorn evaluations for inclusion in the September 2017 Interbull Test Run for Red Dairy Cattle breeds, the GEB recommended that CDN introduce official Milking Shorthorn MACE evaluations for the production and type traits, as well as Somatic Cell Score, Milking Speed and Milking Temperament, effective the official release in April 2018. Publication policies for these new MACE evaluations will be similar to those applied for other breeds with MACE evaluations.
- Based on CDN research aimed at improving the accuracy of genomic evaluations based on validation results, the GEB recommended that the formula be modified for weighting traditional evaluations and Direct Genomic Values (DGV) when calculating official genomic evaluations depending on the heritability of the trait. Specifically, for traits with a heritability over 28%, the recommended weighting formula increases the emphasis on DGV for young animals to generally range from 80% to 90%, with the remaining weight on Parent Average, instead of the average current ratio of roughly 65:35. The expected implementation date of this improvement is April 2018.
- Also with the goal of improving genomic validation results, the GEB recommended that CDN examine the options of (a) applying minimum criteria for achieving official proven status that are specific to each trait underlying Calving Ability and Daughter Calving Ability, and (b) modifying the criteria for inclusion of proven sires in the reference population for genomics.
- Depending on the results of such an analysis, implementation of resulting changes could be effective as early as April 2018.
- Given the growing frequency of bulls receiving an official MACE evaluation for production without also an official MACE evaluation for type, the GEB considered an industry request to review the current requirement that bulls must meet the minimum criteria for an official domestic proof for both production and conformation before either are published. Upon consideration of this request and given the growing market share of genomic young bulls versus progeny proven sires, the GEB recommended that bulls can obtain official proof status for either production or type traits separately with implementation in April 2018. The proof status label for LPI will continue to be based on the lowest status achieved for either production or conformation with order of highest precedence being domestic proof, MACE and Parent Average.
- As requested by the GEB at its last meeting, CDN presented an assessment of advantages and disadvantages associated with changing the current scale of expression for Somatic Cell Score evaluations in Canada to the same scale used for all other functional traits.
- Considering the discussion and input received during the Open Industry Session, the GEB made the following recommendations:
- That effective August 2018, evaluations for Somatic Cell Score in all breeds will be expressed in terms of Relative Breeding Values (RBV) with an average of 100 and a range such that the best animals will have a rating of 115 or better and the poorest animals will be rated 85 or lower (i.e.: standard deviation of 5).
- Given that Mastitis Resistance is an index that combines both Somatic Cell Score and Clinical Mastitis, this trait should be promoted as the primary trait of selection for improved udder health in the Holstein, Ayrshire and Jersey breeds.
- For these same three breeds, Somatic Cell Score will be removed from the Functional Traits section of each animal’s Genetic Evaluation Summary page displayed on the CDN web site as well as from similar pages on the breed association web sites, and will therefore only be presented on the web pages providing details associated with udder health traits.
- The official status for Mastitis Resistance will be based on the official status applied to Somatic Cell Score.
- In advance of the implementation date, CDN will provide industry partners with appropriate extension information to prepare for this change in expression as well as revised file format descriptions.
- In addition to the current display of beta casein test results (i.e.: A2A2, A1A2 or A1A1) on the CDN web site, the GEB recommended that CDN also consider establishing the required data transfer procedures for publishing kappa casein test results (i.e.: BB, AB, AA), given the known associations with cheese-making properties.
- In terms of research and development carried out by CDN to meet future needs of the industry, the GEB supported and recommended that efforts continue in the following areas:
- Modification of current genetic evaluation systems to minimize any underestimation of traditional progeny proofs that may be caused by the pre-selection of young bulls for entry into A.I. based on their genomic evaluation.
- Examination of methods to continually improve the accuracy of genomic evaluations and the associated validation test results for specific traits with lower heritability.
- Development of genomic evaluations for additional traits of importance including more hoof-related and other health traits as well as feed efficiency.
- Analysis to update the current Pro$ formula applied in the Holstein and Jersey breeds at some point in 2018 given changes in milk and component prices in Canada and the implementation by CDN of genetic evaluations for new traits in recent years.
- The next Open Industry Session will be held on Wednesday, April 25, 2018 at the Holiday Inn in Guelph, Ontario, with the Genetic Evaluation Board meeting the following day.
If there are any questions, concerns or comments regarding the recommendations of the Genetic Evaluation Board, as outlined in this summary, please feel free to contact committee members listed here or by contacting Brian Van Doormaal directly at Canadian Dairy Network.