Genetic analysis of prolificacy, milk production and composition traits in Egyptian Zaraibi goats

This study was conducted to genetically and environmentally characterize prolificacy (litter size and weight at birth; LSB and LWB and litter size and weight at weaning; LSW and LWW, respectively), milk yield at the 7th (MY7), 15th (MY15), 30th (MY30), 60th (MY60), 90th (MY90) day of lactation and monthly milk yield (MMY) and milk composition traits in Egyptian Zaraibi goats. A total of 443 and 421 records produced by 121 Zaraibi lactating goats were used to assess prolificacy and milk production traits, respectively. The milk composition traits were measured using 371 milk samples obtained at random from 53 goats. The fourth parity showed the highest values for LWB, LWW, and MMY (3.62, 18.15, and 28.99 kg, respectively). Milk composition traits revealed an inverse tendency, decreasing until the second month and then increasing until the seventh month. The heritability estimates ranged from 0.07 to 0.13, from 0.04 to 0.39, and from 0.07 to 0.33 for prolificacy, milk yield, and milk composition traits, respectively. Negatively high genetic correlations between MMY and all milk composition traits were found. MMY had the highest estimate of heritability (0.39 ± 0.07), this means that the genetic improvement of this trait could be achieved through direct selection.