The following is an extract from an extension article published by Brian Van Doormaal and Lynsay Beavers of the Canadian Dairy Network.
Some producers have adopted the strategy of applying minimum values on one or more traits for filtering through sires to identify those to use in the herd. Such a strategy can have a very significant impact on the resulting sire selection, which is often not considered.
The ideal strategy for producers to achieve their breeding objectives is first to rank sires based on their preferred selection index (i.e. Pro$ or LPI). Once the highest sires for that index are identified, then the second step is to determine how to best incorporate them in your herd by avoiding matings that result in too much inbreeding and/or a higher risk of carrying an undesirable genetic recessive such as the gene associated with Cholesterol Deficiency.
Two national genetic selection indexes, LPI and Pro$, have a critical role to play. Canadian Dairy Network (CDN) and each breed association provides lists of top animals with proven sires, genomic young bulls, cows and heifers, ranked based on their LPI and Pro$. These indexes have been developed and implemented to guide Canadian producers in terms of setting their breeding goals and then realizing them. Select which index best suits your breeding goals and then stick with it to select the sires to use in your herd while managing the inbreeding level and likelihood of genetic recessives for each mating.
Recall that Pro$ was introduced in August 2015 as a profit-based index that ranks sires and cows according to the net profit that their daughters are expected to realize during the first six years of their life. Compared to Pro$, producers using LPI as their primary selection index can expect more genetic progress for conformation traits but slower gains for production yields and both indexes have a similar expected response for most functional traits.
To consult the full article, click here: https://www.cdn.ca/document.php?id=470.