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Improving Existing Traits and Adding Exciting New Ones 21-MAR-2016 Some believe genomics is the be-all and end-all of the opportunity for genetic improvement. In reality, genomics is a by-product of solid traditional genetic evaluation systems and would not work without them as input. For this reason, Canadian Dairy Network (CDN) is continually improving both genomic AND traditional genetic evaluations to provide you with the most accurate overall genetic information possible for each animal. Read about some recent changes that have been made, as well as about some exciting things to come on the horizon. Separating Somatic Cell and Production Traits In 1999, Canada was one of the very first countries in the world to use each cow's test day information for genetic evaluations instead of lactation-based data. Since that time the production traits, namely Milk, Fat and Protein yields, were evaluated simultaneously with Somatic Cell Score using statistical software called the "Canadian Test Day Model" (CTDM). While this system has served the industry very well for the past 15 years or so, research at CDN in recent years identified an opportunity to improve the stability of published Somatic Cell Score proofs. Given the growing importance of this trait in the eyes of producers and its contribution towards both LPI and Pro$ indexes, CDN geneticists found that both production and Somatic Cell Score proofs would be improved, in terms of variability over time, if they were analyzed using two separate test day models rather than calculated simultaneously within a single multiple trait system. Effective April 2016, the new approach of calculating production evaluations separately from Somatic Cell Score will be used for all breeds. This enhancement also required the calculation of new genetic parameters such as heritabilities and genetic correlations across traits. In addition to affecting Milk, Fat, Protein and Somatic Cell Score, the update can also lead to changes for Lactation Persistency and a minor impact on Herd Life, since Somatic Cell Score is a predictor of indirect Herd Life. For Holsteins, this improvement is expected to have no impact on LPI for 85% of proven sires and 76% of genotyped cows, and the most extreme changes will be a one-time adjustment of up to ±40 and ±130 LPI points for proven sires and cows respectively. Daughter Fertility and Female Fertility Traits Improvements to CDN's traditional evaluations for female fertility are also expected before the end of this year, which mainly entails the use of pregnancy check data to better determine conception dates. The pregnancy check data collected from producers by DHI now provides CDN with the opportunity to improve the existing genetic evaluation system for traits related to female fertility, of which three reflect heifer fertility and four represent fertility in lactating cows. The main traits to be affected by this improvement are the interval from first service/insemination to conception in both heifers and cows as well as days open. To date, subsequent calving records have been used to determine when conception occurred, simply by using the insemination record approximately 280 days prior to the calving date. Utilizing data that confirms pregnancy status will reduce the time required to validate that conception actually did occur and it will also allow for the inclusion of conception dates for females that do not have a subsequent calving date at CDN. In terms of sire proofs for First Service to Conception, more data on daughters will be available, and about six months earlier, which therefore increases the accuracy of this trait, as well as Daughter Fertility as the overall index that combines key female fertility traits. Novel Traits to Come in Canada On-going research is set to release a wealth of new information in the coming years. Key areas of current research include health traits as well as feed efficiency and methane emissions.
As is the case in all industries, the only thing constant is change - the same goes for Canadian genetic evaluations. Improvements to methodology, incorporating new data to strengthen existing evaluations, and the development of novel traits all contribute to maintaining Canada's status as a world leader in dairy cattle improvement. Authors:
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