Relationship between sire's estimated breeding values for first lactation and life time traits and ranking of sires in Sahiwal and its cross

Abstract

The performance records of 587 Sahiwal and its crossbred daughters of47 sires maintained during 1970 to 2001 at dairy farm ofthe university were used to evaluate sires for first lactation and life time performance traits. First lactation traits included-were age at first calving (AFC), first lactation milk yield (FLMY), first lactation period (FLP), first dry period (FDP), first calving interval (FCI), first service period (FSP); and life time traits were-herd life (HL), productive life (PL), life time milk yield (LTMY), total lactation length (TLL) and life time milk yield/day of productive life (LTMY/PL). Best linear unbiased prediction (BLUP) procedure was used to obtain the estimates of breeding values. The estimated breeding values (EBV's) showed large genetic variation between sires for both first lactation and lifetime traits. The EBV's ofsire for AFC had negative product moment correlation with EBV's for FLP an FSP, while, low and positive with EBV's for FLMY, FDP and FCl. The product moment correlation among sires estimated breeding values for HL, PL, TLL, LTMY were positive and moderately high (0.39 to 0.86). Rank correlation among EBY's of sires indicated that all sires would not rank same for first lactation and life time performance traits. However, the ranks of sires for different traits revealed that 4-5% top sires had similar rank for first lactation and life time traits. These results suggested that to improve lifetime productivity major culling of bulls should be done on the basis of their daughter's first lactation milk yield.