|Wright, Janice - Jan|
Submitted to: Journal of Dairy Science
Publication Type: Abstract only
Publication Acceptance Date: 6/22/2003
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Concern has continued on possible bias in genetic evaluations of animals from embryo transfer (ET) due to preferential management. Performance of registered ET Holsteins was documented and compared with that of registered Holsteins from uniparous and biparous births. During the 1960s, 1970s, 1980s, and 1990s, number of ET Holsteins was 18, 1947, 103,436, and 269,064, respectively; numbers peaked in 1993 and have declined since. Of those ET animals, 88, 82, 85, and 66%, respectively, were female. Pedigree merit of ET animals was superior to population mean for milk, fat, and protein yields by 169, 6, and 8 kg, respectively, for ET cows and by 226, 9, and 9 kg for ET bulls. Males were <2% of registered twins. Pedigree merit of registered offspring from parents with one biparous birth or more was nearly identical to population mean for cows (superiority of only 15, 1, and 0 kg for milk, fat, and protein, respectively), but pedigree superiority for twin bulls (252, 10, and 9 kg) was even greater than for ET bulls. Means for ET cows (n = 10,277; mean of 1.02 sisters per ET cow) and their full sisters were virtually identical for standardized yield, yield deviation, and genetic merit for milk, fat, and protein. If ET cows were treated preferentially, their full sisters received equal preference. Mean somatic cell score (SCS) of ET cows (3.1) did not differ from population mean, but productive life (PL) of ET cows was 0.6 mo longer. Mean yield deviations for twins (n = 6514; mean of 1.02 uniparous full sisters per twin) were 93, 5, and 3 kg less for milk, fat, and protein, respectively, than those of their uniparous full sisters; mean twin SCS (3.1) did not differ, but mean twin PL was 0.4 mo shorter. Genetic merit of ET bulls (n = 3512; mean of 1.3 siblings per ET bull) did not differ significantly (P > 0.05) from that of their full brothers for all yield and component percentages, PL, and daughter pregnancy rate. More effort is needed to document the apparent bias in genetic evaluations of ET animals.