H.D. Norman, J.L. Hutchison*, and J.B. Cole
Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD
2012 J. Dairy Sci. (?)
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Availability of genomic evaluations since 2008 has resulted in many changes in breeding programs. The contribution of young bulls (0.8 to 3.9 yr old) to those programs was investigated. The number of Holstein sires of young bulls doubled from 2008 (126 sires) to 2011 (276 sires); 14% of sons were sired by a young bull in 2008 compared with 40% in 2011. Corresponding values for Jerseys were 34 and 54 sires of young bulls in 2008 and 2011, respectively, with 19 and 40% sired by young bulls. From US breeding records from 2007 through 2011, 19,359,730 Holstein and 1,133,090 Jersey breedings were examined. Young bulls were used for 28% of Holstein breedings in 2007, 29% in 2008, 39% in 2009, 43% in 2010, and 48% in 2011; annual percentages for young genotyped Holstein bulls were 0, 8, 36, 42, and 48%. Genotyped bulls accounted for 0, 26, 92, 98, and 99% of breedings to young Holstein bulls annually from 2007 through 2011. Young bulls were used for 25, 27, 31, 33, and 40% of Jersey breedings annually, with 0, 0, 22, 32, and 39% of breedings to young genotyped bulls; genotyped bulls accounted for 0, <1, 72, 98, and 98% of breedings to young Jersey bulls. Percentage of female progeny sired by young bulls was calculated by progeny birth year for 5,035,103 Holstein and 496,062 Jersey heifers. Young bulls annually sired 24, 23, 23, 33, and 40% of Holstein heifers born from 2007 through 2011 and 29, 27, 30, 33, and 35% of Jersey heifers. Mean sire age for Holstein progeny born in 2011 was 23 mo younger than in 2006 for bulls and 12 mo younger for heifers; corresponding values for Jerseys were 15 and 4 mo. Mean net merit from December 2011 weighted by number of breedings was $290 for 2008 breedings, $339 for 2009 breedings, and $361 for 2010 breedings of active Holstein bulls and $230, $483, and $532 for genotyped Holstein bulls (a difference of $60, $144, and $171, respectively). Corresponding values for Jerseys were $270, $286, and $324 for active bulls and $396, $448, and $510 for genotyped bulls (differences of $126, $162, and $186). Use of young bulls has greatly reduced the generation interval and improved the rate of genetic gain since implementation of genomic evaluation.
(Key words: breeding, service sire, genomic)