Abstract
Simple SummaryIn a population of 1112 individuals of Sarda sheep, we investigated the polymorphism of 45 single nucleotide polymorphisms (SNPs) in 15 different genes that have been previously investigated because of their relation to metabolism and innate immunity. For SNPs with a sufficient allele frequency, we also tested their influence on a wide panel of dairy traits. The genotyping evidenced some new genetic patterns, and seven SNPs had significant influences on the milk yield, composition and coagulation traits. The results may represent a starting point to acquire new knowledge in the field of dairy sheep sector and to improve the breeding schemes for the Sarda sheep breed.The aim of the present research was to analyze the variability of 45 SNPs from different genes involved in metabolism and innate immunity to perform an association analysis with the milk yield, composition and milk coagulation traits. A population of 1112 Sarda breed sheep was sampled. Genotyping was generated by a TaqMan Open ArrayTM. Thirty out of the 45 SNPs were polymorphic, and 12 displayed a minor allele frequency higher than 0.05. An association analysis showed that the variability at genes PRKAG3 and CD14 was significantly associated with the daily milk yield. The variability at PRKAG3 was also associated with the protein and casein content, somatic cell score and bacterial score. The variation at the PRKAA2 gene was associated with the milk lactose concentration. The SNPs at CD14 were also associated with the traditional milk coagulation properties, while the SNPs at GHR and GHRHR were associated with kSR, a derived coagulation parameter related to the rate of syneresis. The information provided here is new and increases our knowledge of genotype–phenotype interactions in sheep. Our findings might be useful in appropriate breeding schemes to be set up for the Sarda sheep breed, but these should be confirmed by further studies, possibly performed on independent populations.
Highlights
Sheep are farmed all over the world, because of their great adaptability and relatively high productions
An association analysis showed that the variability at genes PRKAG3 and CD14 was significantly associated with the daily milk yield
The SNPs at CD14 were associated with the traditional milk coagulation properties, while the SNPs at GHR and GHRHR were associated with kSR, a derived coagulation parameter related to the rate of syneresis
Summary
Sheep are farmed all over the world, because of their great adaptability and relatively high productions. In the European Union, sheep milk production has been markedly increased in the last decades, extending from 2 to about 3 million t in the period of 1960–2019, and dairy sheep farming is a relevant sector of agriculture in many areas, such as for Greece, the leading EU country with 944 thousand t of ewe milk produced in 2019, followed by Romania, Spain and Italy [2]. Almost all milk is transformed into cheese; milk traits related to cheese-making, including milk coagulation properties (MCP), curd firming and syneresis, need to be evaluated, as they might impact the farm income [3]. Traditional and derived MCP have been studied in cattle and, later, in sheep to provide important information on the dynamics of coagulation, highlighting the similarities and differences between species [6,7]
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