AGB 211: Livestock and Poultry Breeding (2+1)

BEST LINEAR UNBIASED PREDICTION (BLUP) 

• When the performance records are used as clues in selection index, it is automatically assumed that the records have been adjusted previously for all known sources of environmental bias using adjustment factors. This method (Henderson et al., 1975) is mainly based on least-squares method. The basic steps involved in BLUP estimates are as an expression (model) that describes an individual’s performances in terms of all factors, that need to be taken into account i.e., herd-year-season model will be

Y_ijk = µ + f_i + s_j + e_ijk

where,

Y_ijk = measurement on the k^th progeny of the j^th sire born in the i^th herd- year- season

µ = over all mean

f_i = effect of the i^th herd- year- season

s_j = effect on the j^th sire born

e_ijk = residual error

BLUP is the best method for evaluating the breeding value of bulls and rank the sires according to their genetic merit because of the following reasons:

• Corrects the data automatically for all known non genetic sources
• Estimates simultaneously all the factors concerned
• Uses available a priori information more efficiently and more flexibly
• Maximizes the correlation between predictor and predict
• Provides an estimate of response to selection for groups of animals born in different years
• Accounts for complications such as non-random mating, genetic and environmental trends over time, herd differences in the average breeding value of dams and bias due to selection and culling
• Estimates also the breeding value of individual having no records.