Estimation of genetic parameters and genetic trends for reproductive traits in Saanen goats
The study was conducted on Saanen goats raised in Croatia. The object of the study was to determine the average litter size (LS), birth weight (BW) and total litter weight (TLW). The study included a total of 2 500 goats among which 1 786 were phenotyped. A total of 6 349 records for BW and 4 256 records for LS and TLW were used in descriptive and inferential statistical analysis. Determined averages for LS, BW and TLW were 1.74 lambs, 3.27 kg and 5.65 kg, respectively. Twinning and tripling
... ing and tripling rates were 36.9% and 6.2%. Single-trait analysis under repeatability animal model was used in estimation of variance components and prediction of breeding values. Season (as year-month interaction), age at lambing (as quadratic regression) nested within parity and type of birth were treated as fixed, while herd-year, additive genetic, permanent environmental and residual were treated as random effects, respectively. Investigated environmental effects significantly affected all reproductive traits (p<0.001). The largest phenotype variability among investigated traits was determined for TLW. Additive genetic effect accounted for 7%, 5% and 4% in total variability for LS, BW and TLW, respectively. Genetic trends of reproductive traits were estimated for the period from year 2000 to 2010. A positive genetic trend was determined for LS, a negative genetic trend for BW and genetic stagnation for TLW.