Objective: Estimate multi-trait genetic parameters for somatic cell score, milk yield and type traits in Nigerian Dwarf (ND) goats from the United States.
Methods: Data from 1041 ND goats in the United States with kiddings in 95 herds were used to estimate multi-trait genetic parameters for somatic cell score (SCS), milk (MILK), fat (FAT) and protein (PROT) yields, and 14 type traits. An 18-trait mixed linear animal model for lactation mean SCS (Log2), MILK, FAT, PROT and 14 type traits was applied. A factor analytic approach (FA1) in ASReml software was used to obtain convergence.
Results: Averages for SCS were low (2.85±1.29 Log2), and were 314±110.6, 20.9±7.4 and 14±4.9 kg, respectively, for MILK, FAT and PROT. Heritabilities for SCS, MILK, FAT and PROT were 0.32, 0.16, 0.16, and 0.10, respectively. The highest heritabilities for type traits were for stature (0.72), teat diameter (0.49), and rump width (0.48), and the lowest estimates were for dairyness (0.003) and medial suspensory ligament (0.03). Genetic correlations of SCS with MILK, FAT and PROT were positive but low (0.25, 0.18 and 0.23, respectively). Genetic and phenotypic correlations between MILK, FAT and PROT were high and positive (≥0.66). Absolute values of genetic correlations involving SCS with type traits were generally low or not different from zero. Most of the phenotypic correlations involving SCS with type traits were low. No serious unfavorable genetic correlations between milk yield traits and SCS or between milk yield traits or SCS and type traits were found.
Conclusion: Genetic variation exists in the ND breed for most studied traits. The development of selection programs based on these estimates may help accelerate favorable multi-trait genetic changes in this breed.
Keywords: Fat Yield, Protein Yield; Genetic Correlation; Goats; Heritability.