Over the last two years, STgenetics has been collecting data on feed intake and weights on several thousand Holstein heifers at the Ohio Heifer Center. In this particular evaluation, only heifers between 200 and 400 days of age were considered. The final dataset included 1939 heifers with an average age of 301 days. Data collection was organized in trials of 70 days. The hardware comprised 80 GrowSafe bunks in 10 pens. On average, 8 animals were allowed to enter a pen per GrowSafe bunk. Daily feed intake was recorded using the GrowSafe bunks whereas body weight was recorded at entry and exit of the trial and, on average, 3 additional times during the trial. Average daily feed intake ranged from 11.48 to 64.40 with a mean of 40.78 pounds of fresh feed per day. Body weight ranged from 292.3 to 1087 with an average of 650.4 pounds. Average daily gain was estimated by a linear regression of body weight against days of age and averaged 2.153 pounds per day, ranging from 0.01 to 7.63. QC measures comprised minimum valid feed intake days (12), minimum valid weightings (2), minimum days on trial (30) and positive average daily gain. Residual feed intake was defined as the residuals from a linear model on daily feed intake comprising the fixed effects age, metabolic body weight, pen-year-season and average daily gain. Those residuals subsequently entered 2 different genetic and genomic evaluation models: An animal model whereas the covariance across individuals was defined by the numerator relationship matrix (Pedigree only) and the same model with the combined genomic and additive genetic relationship matrix (Single Step GBLUP). All models were fitted in a Bayesian framework using Gibbs sampling. Posterior means (and standard deviations) for the heritability estimates were 0.21 (0.06) for the traditional animal model and 0.16 (0.03) for the single step GBLUP model. Reliabilities of all 6718 individuals of the most recent 5 generations of the pedigree ranged from 0.02 to 0.7 with a mean of 0.16. The highest reliabilities were achieved by sires and grandsires having a high number of daughters and/or granddaughters that went through the trials. Correlations between the genomic breeding values of residual feed intake and traits currently evaluated by the USDA were small with the only exception being an unfavorable correlation between residual feed intake and PTAT. Keywords: feed efficiency, genomic prediction, single step
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Electronic Poster Session - Biology - Feed Intake and Efficiency 1, , 665, 2018
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