Impact of polymorphisms at the PRNP locus on the performance of dairy goats reared under low-input pastoral farming systems

Abstract

Our hypothesis was that polymorphisms in the PRNP locus controlling animal resistance to scrapie do not adversely affect overall performance of dairy goats reared under low-input pastoral farming systems. Hence, the objective was to investigate the association of polymorphisms at codons 146 (N/S/D), 211 (R/Q) and 222 (Q/K) in the PRNP gene locus with milk production, udder health and body condition score (BCS) of dairy goats in Greece. A total of 766 goats from seven farms were used. Goats belonged to two indigenous Greek breeds, Eghoria (n = 264) and Skopelos (n = 287), and one foreign breed, Damascus (n = 215); the former two were treated together as one indigenous population. Nuclear DNA was extracted from individual blood samples. Polymorphisms at the studied codons were detected with Real-Time PCR analysis. Milk production, udder health and BCS of individual animals were recorded monthly for two consecutive milking periods. Milk production traits included daily and total milk yield and corresponding milk fat, protein, lactose and solids-non-fat (SNF) content and yield. Udder health traits included udder asymmetry, fibrosis, abscesses and total number of udder problems per milking period, milk somatic cell count, and total viable count. The allele substitution effect at codons 146, 211 and 222 on the studied traits was assessed with mixed linear models. Overall, resistance-associated alleles did not affect the studied traits. Nominally statistically significant effects on some milk composition, udder health and BCS traits were detected, which did not remain significant after correcting for multiple testing. In conclusion, genetic selection for scrapie resistance in dairy goats is not likely to compromise animal performance. Nevertheless, continuous monitoring of selective breeding programmes is advised to safeguard against possible emerging side-effects on animal performance and genetic diversity.