GENOMAX™ BULLS VS PROGENY PROVEN BULLS Dr. J. P. Chesnais, Semex Senior Geneticist
CHOOSING MATING SIRES Since the arrival of genomics, breeders have had several choices when selecting mating sires: 1) B ulls with first crop daughters; typically, these bulls are five to nine years of age and were first proven anytime between the last proof round and a proof round four years ago 2) B ulls which now have a lot of second crop of daughters, are at least 10 years of age and typically have hundreds or thousands of daughters in production 3) B ulls that do not have daughters in milk yet but have a genomic evaluation; typically, these bulls are one to three years of age and at Semex we call them Genomax™ bulls
If you selected bulls in each of these categories today, what could you expect in terms of the real genetic merit of these bulls? Would one category be better than the other on average? Which category is the safest to use for ensuring that most daughters in your herd will come from top bulls? Table 1 below shows the average LPI evaluation for the top active bulls in Canada in each of three categories: first crop sires, second crop sires and young genomic sires. First crop sires had to be officially proven, and second crop sires had to have at least 500 daughters in their proof. For first and second crop bulls, the averages are for the top 10 active bulls. For young genomic bulls, the averages are for the top 30 bulls, given that they are best used in groups, and that a greater number of different bulls are recommended than for proven bulls to inseminate the same number of cows. Also, young bulls do not produce as much semen as older bulls, and there is less time to accumulate a semen bank for them, so it makes sense that more top young bulls will be required to satisfy the demand for this category of bulls. All young bulls had to be active to be considered. Table 1: Average LPI evaluation and reliability of the top 10-30 bulls in each of three categories (April 2011 evaluations, CDN) Top sires in the US
8
Average LPI
Average REL
Top 10 first crop sires
2,330
89
Top 10 second crop sires
1,881
97
Top 30 young genomic sires
2,841
65