ABSTRACT
Enhancing dairy productivity in Pakistan relies heavily on crossbreeding indigenous cattle with exotic breeds like Holstein Friesian (HF). This study comprehensively evaluates the performance, genetic parameters, and effects of exotic inheritance level and sire selection on key economic traits in HF crossbred cattle to inform sustainable breeding strategies. Data on 1,123 lactation records were analyzed to estimate descriptive statistics, variance components, heritability, and genetic correlations for milk production (Daily Milk Yield-DMY, 305-day Standard Yield-SMY, Lactation Yield-LY), reproduction (Age at First Service-AFS, Age at First Calving-AFC, Calving Interval-CI, Dry Period-DP), and lactation length (LL). Results indicated a mean SMY of 3569 ± 729 L, AFC of 1161 ± 107 days, and CI of 423 ± 24 days. A significant linear trade-off was observed: increasing HF blood level from 50% to >75% raised SMY from 2919 to 4077 L but worsened AFC (1126 to 1191 days). Both blood level and sire group had highly significant (p<0.001) effects on milk yield and AFC. Crucially, the sire group had no significant effect on CI or DP. Heritability was high for milk yield traits (h²=0.38-0.40), moderate for AFC (h²=0.188), and low for CI and DP (h²=0.14). Genetic correlations were near-perfect among milk traits (r>0.91) and between CI and DP (r=0.87), but negligible between SMY and AFC (r=-0.07). The study concludes that an intermediate exotic inheritance level (62.5% HF) optimizes the yield-adaptation balance. The absence of genetic antagonism between yield and AFC, coupled with significant sire variance, enables simultaneous genetic improvement of both traits through the selection of proven sires. However, the low heritability of postpartum fertility traits necessitates management-driven interventions for optimal calving intervals. A successful dairy improvement strategy must therefore integrate balanced crossbreeding, strategic sire selection for yield and early maturity, and intensified nutritional and herd health management to unlock the full genetic and economic potential of HF crossbreds in Pakistan.