Mapping loci affecting live weight and body size in Lori-Bakhtiari sheep using paternal half-sib design and identification of biomarkers linked to growth rate

The aim of this study was to map loci affecting live weight and body size in Lori-Bakhtiari sheep and identification of biomarkers linked to growth rate in sheep. Quantitative trait loci (QTL) linkage analysis in a Lori-Bakhtiari sheep population was conducted using the regression-based interval mapping method. The mapping population consisted of 162 animals related to 5 paternal half families. Phenotypic data were measurements of birth weight (BW), weight at one month of age (W1), weaning weight (WW), weight at six months of age (W6), chest circumference (HG6), body length (BL6), wither height at six months of age (HT6), weight at nine months of age (W9) and yearling weight (W12). Five sires and their progeny were genotyped for microsatellite markers in a candidate region on sheep chromosome 1. Data were analyzed in two phases, individual family analysis and combined family’s analysis using a single-QTL model. Analysis based on individual families revealed QTL related to W1 (210.6 cM), near INRA011 marker segregating in the second family. In the third family, QTL affecting W1 and WW were identified at 252.6 and 223.6 cM, nearby MCM137 and LSCV105 markers, respectively. In addition, in the fourth family, a QTL underlying W1 was detected at 256.6 cM near LSCV105 marker. Combined analysis of all the families resulted to the identification of a QTL associated with W1 at position 254.6 cM relative to the centromere near the LSCV105 marker. There were two strong candidate genes close to the location of the detected QTL, the transferrin and PIT1 genes, thus these genes may account for the observed QTL effects for growth traits in Lori-Bakhtiari sheep.