Estimates of genetic parameters and genetic trends for production and reproduction traits in Iranian buffaloes (Bubalus bubalis)

Calving and milk production records from April 1992 to March 2012 comprising 5353 records of age at first calving (AFC), 2972 records of 305-days milk yield (MY) and 2349 records of interval between first and second calving (CI) from the first lactation buffaloes within 785 herds of Iran were analysed using a linear animal model to estimate variance components and heritability for these traits. A linear animal model including direct genetic effect was implemented by Gibbs sampling methodology. A single Gibbs sampling chain with 300 000 rounds was generated by the TM program. Genetic trends were obtained by regressing yearly mean estimates of breeding values on birth year. Posterior mean estimates of direct heritabilities for MY, AFC and CI were 0.46 +/- 0.21, 0.20 +/- 0.06 and 0.21 +/- 0.14, respectively. The posterior means of direct genetic correlation between MY-AFC, MY-CI and AFC-CI were -0.31, 0.01 and -0.17, respectively. Estimates of direct genetic trends for MY, AFC and CI were negative and significant, and their corresponding values were -1.50 +/- 0.05 (P < 0.0001), -0.04 +/- 0.001 (P < 0.0001) and -0.02 +/- 0.005 (P < 0.001), respectively. Medium to high direct heritability estimates for productive and reproductive traits would be due to higher additive genetic variances for these traits and implied that applicable genetic variations observed for productive and reproductive traits could be applied in designing future genetic selection plans for Iranian buffaloes.