Population genetic structure and milk production traits in Girgentana goat breed

Abstract

The aim of this work was to evaluate the genetic status of the Girgentana goat, an endangered breed from Sicily (Italy), using microsatellite markers. Furthermore, as the main purpose of the Girgentana breed is milk production, quantitative milk traits were investigated, including fatty acid profile. Molecular data from CSN1S1, CSN2, CSN1S2, and CSN3 casein genes were also used to infer haplotypes. A total of 264 individuals were collected. Samples of Maltese (n ≤ 41) and Derivata di Siria (n ≤ 33) goat breeds were also used to understand the genetic relationship among breeds. Test-day records for milk production were collected to determine daily milk yield, fat, protein, casein, lactose, and somatic cell count. Individual milk samples were also collected for fatty acid extraction. Wright's statistics, gene flow, Nei genetic distance, factorial correspondence analysis, and Bayesian assignment test showed the existence of genetic variability and differentiation among breeds. The AMOVA results indicated that 89.96% of the total variance was partitioned within populations. The Girgentana breed appears to have a subdivided population, and has not experienced a recent bottleneck. A high variability in milk yield was observed. Mean morning milk yield was 1448 ± 404 g, with 4.30 ± 0.87% and 3.72 ± 0.44% of fat and protein percentages, respectively. The average somatic cell count found in Girgentana goat milk was higher than the threshold of 1 500000 cells/mL advised in Europe for fresh milk. Gross milk and fatty acid composition were similar to that reported in the literature for other local goat breeds.