Relation between runs of homozygosity pattern and progeny uniformity in Nellore cattle

Abstract

Quantifying inbreeding levels and possible losses due to inbreeding depression on economically relevant traits would be ideal for establishing breeding strategies in breeding programs, but it would be equally advantageous if there is a relationship between genetic variability of offspring with high levels of inbreeding. The objective of this study is to identify the effects of inbreeding on the progeny variability of Nellore cattle, with a differentiated approach. Coefficients of inbreeding will be calculated from the genomic relationship matrix and the runs of homozygosity (ROH). The effect of inbreeding depression on birth weight, weaning weight, post weaning weight gain, scrotal circumference and visual muscle score will be estimated. Later, to study the effects of inbreeding effect on the variability of the progeny of bulls and according to the inbreeding coefficients, estimated by ROHs, the bulls of the two extremes of the distribution of inbreeding levels, based on quartiles : i) Quartile 1, containing 25% of the bulls with the highest ROH (minimum windows of 16 Mb) ii) Quartile 4, group with 25% with lower ROH (minimum windows of 1Mb). In addition, we will analyze the existence of ROH patterns in relation to the position and distribution along the chromosomes related to low genetic values variability of the progeny. With this research we hope to collaborate to clarify the consequences of inbreeding on the variability of progeny breeding value and on inbreeding depression losses in large herd of Nellore (Bos indicus) beef cattle.