Gains in Reliability with Genomic Information in US Commercial Holstein Heifers

Abstract Text:

Genomic selection allows producers to accurately identify genetically superior animals at a much earlier age than traditional parent averages. The objective of this study is to quantify the gain in reliability from including genomic information in a commercial US Holstein dairy female population. Genomic Predicted Transmitting Abilities (GPTAs) from two Zoetis Low Density Panels consisting of 6,836 markers (LD) and 10,932 markers (ZLD) and Parent Averages (PAs) for 73,480 Commercial US Holstein heifers were available for this study. Predicted transmitting abilities (PTAs) from the December 2013 USDA-CDCB evaluation for non-parent animals born in 2012 and 2013 were compared to corresponding GPTA from the December 2013 predictor population. Means were derived and daughter equivalents (DE) were estimated as described by VanRaden and Wiggans (1991). Mean reliabilities for the LD and ZLD panels were 66.85%, 71.15%, 71.15%, 71.15%, 64.48%, 67.45% and 63.10% for Lifetime Net Merit (NM$), Milk, Fat, Protein, Productive Life (PL), Somatic Cell Score (SCS) and Daughter Pregnancy Rate (DPR), respectively (not shown).  Average gains in reliability above parent average ranged from 42.69% to 45.44% for LD and from 44.93% to 47.62% for ZLD across the selected yield, health and fertility traits. Mean Daughter Equivalent (DE) above Parent Average across the selected traits ranged from 23.9 to 142.0 and 24.9 to 147.5 for LD and ZLD, respectively (Table 1). These results suggest that including genomic information in the genetic evaluation of young commercial Holstein females substantially increases reliability over the traditional parent averages.

Table 1. Observed reliabilities in the December 2013 for Traditional Parent Averages and their December 2013 Genomic Evaluation by trait and DNA panel (Chip)  

Trait1	Chip2	Parent Average	Genomic Value	Gain3	DE4
NM$	LD	23.21	66.76	43.55	30.7
	ZLD	21.54	67.21	45.68	32.0
Milk	LD	25.61	71.05	45.44	23.9
	ZLD	23.93	71.56	47.62	24.9
Fat	LD	25.61	71.05	45.44	23.9
	ZLD	23.93	71.56	47.62	24.9
Protein	LD	25.61	71.05	45.44	23.9
	ZLD	23.93	71.56	47.62	24.9
PL	LD	20.44	64.39	43.95	74.4
	ZLD	18.72	64.84	46.12	77.5
SCS	LD	23.13	67.44	44.31	55.5
	ZLD	21.37	67.92	46.55	57.8
DPR	LD	20.34	63.03	42.69	142.1
	ZLD	18.47	63.40	44.93	147.6

¹NM$ = Lifetime Net Merit Dollars, PL= Productive Life, SCS= Somatic Cell Score, DPR= Daughter Pregnancy Rate.

²LD= Low Density Panels consisting of 6,836 SNPs, ZLD= Low Density Panels consisting of 10,932 SNPs

³Gain=Genomic REL – Parent Average REL.

⁴DE= Daughter Equivalent

Keywords: Dairy, Genomic, Reliability