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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Genomics and Improvement Laboratory » Research » Publications at this Location » Publication #338521

Title: Genetic evaluation of gestation length as a trait of the service sire

item Wright, Janice
item Vanraden, Paul

Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/27/2017
Publication Date: 6/24/2017
Citation: Wright, J.R., Van Raden, P.M. 2017. Genetic evaluation of gestation length as a trait of the service sire. Journal of Dairy Science. 100(Suppl. 2):42(abstr. M100).

Interpretive Summary:

Technical Abstract: Predicted transmitting abilities (PTA) for gestation length (GL) were developed for all dairy breeds and crossbreds. Initial GL edits gave 20.5 million records of 10.8 million cows and included GL after either heifer or cow inseminations. Preliminary analysis revealed a very negative genetic trend in the last 2 years (toward shorter gestation), causing concerns about effects of unreported embryo transfer (ET) or sexed semen. Further edits required a sex code from the calving ease database and a pedigree record for each calf to determine its ET status. Those edits reduced the data to 12.4 million records of 6.8 cows born since 1990. The model included effects of conception month, age-parity of dam, breed of dam, offspring code, herd-year-season, service sire, permanent environment of dam, and error. PTAs were computed for all 73 million animals from their additive relationships to the sires. An animal model for GL as a trait of the calf might provide higher reliability by using maternal genetic relationships for dams, but the focus here was on service sire direct genetic effects, which were nearly 4 days shorter for Holsteins and Jerseys than for Brown Swiss and Guernseys. Heritability estimates computed as 4 times the service sire variance were 0.48 from heifers and 0.44 from all lactations (heifers and cows) based on 5 million Holstein GL records. The GL PTAs for recent Holstein bulls (born 1995 or later with 90% or higher reliability) have a minimum of -5.6 and maximum of +6.4 and a SD of about 1.4 day. Jersey and Brown Swiss bulls both had the same SD of about 1.4 after adjustment to within-breed bases but had smaller ranges of values than Holstein due to fewer bulls: -4.2 to +5.0 for Jersey; -3.6 to +5.6 for Brown Swiss. Genomic predictions for Holsteins averaged 65% reliability. Short GL is favorably correlated by about 0.38 with daughter calving ease and by about 0.24 to 0.29 with yield and productive life. Thus, current strong selection for these correlated traits has already decreased GL in recent years. Gestation length (GL) can be useful in mating programs to group all birth dates together in seasonal calving, managing maternity pens, or improving calving ease as a correlated trait. Official GL evaluations are expected in 2017.