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|Autori: ||Moltisanti, Valentina|
|Titolo: ||Genetic polymorphisms at lipogenic loci in Modicana cows: effects on milk production traits in different feeding systems|
|Abstract: ||Sicily has one of the richest heritages of animal biodiversity of Italy. The dairy sector is characterized by many typical products, often related to breeds and indigenous cows, to feeding techniques that make extensive use of grazing and traditional cheese-making techniques. Dairy cattle breeds have been subjected to an intensive selection towards improvement of milk production traits. Milk composition is very variable, being conditioned by the complex metabolic activity linked to individual variability of animals, to nutritional and environmental factors.
In the present study, it was investigated for the first time in Modicana breed, novel information about polymorphisms at key genes involved in lipid metabolism and interaction between these polymorphisms and the feeding systems. It was studied how the presence of pasture in the diet can interfere with the effects of polymorphisms at the studied loci on milk yield, gross composition and fatty acid profile.
Modicana cows reared in two farms of the Ragusa province with an extensive and semi-intensive system were characterized under the genetic profile for the lipogenic polymorphisms (ABCG2-Y581S, DGAT1-K232A, STAT5A-V686A, SCD1-A293V). Subsequently, on the basis of the genotypes detected, 36 and 38 cows were selected from the semi-intensive and extensive systems, respectively. From these animals, individual phenotypic data were collected relative to productivity, milk composition, fatty acid profile and mineral composition, in order to evaluate the effect of the genetic polymorphisms and interaction with feeding systems on the quantitative and qualitative characteristics of milk.
The entire population resulted monomorphic at ABCG2 Y581S polymorphism while for the other loci the allele with higher frequency were: 91% for GC (232A) at DGAT1, 68% for T (686V) at STAT5A and 73% for T (293A) at SCD1.
Feeding system influenced milk yield and protein content that resulted higher in animals fed with natural pasture while, when feeding systems were considered in interaction with the polymorphisms, results do not allow to find significant differences within the different phenotypes in milk in both systems, extensive and semi-intensive.
Feeding system also affected milk FAs composition and animals reared in an extensive system, showed a lower content of SFA and a higher fraction of MUFA, PUFA and trans FAs. Then, considering the interaction between the feeding systems and the polymorphisms on milk FAs composition, results showed that some FAs were significant affected by this interaction. The DGAT1-K232A polymorphism in interaction with feeding system, affected the content of C4, CLA and C22:4. Milk of animals with DGAT1 GC/GC genotype (232A) and fed with pasture showed a higher content of CLA. The STAT5A-V686A polymorphism affected OBCFA composition, the content of which resulted higher in animals with TT genotype (686V). Animals with TT genotype showed also a higher content of C18:1t11, C18:1c9, C20:4 and C22:5n3 and a lower C20:5n3 content. No interaction has been detected between the identified genotypes and the feeding systems. The SCD1-A293V polymorphism in interaction with feeding systems affected the contents of C4, C6, C8, C18:1t11 and C20:3 that gradually decreased in animals reared in an extensive system from CC to heterozygous to TT genotype.
Finally, regarding mineral composition, the only significant effect was reported for the K content that was associated with STAT5A-V686A polymorphism and resulted higher in heterozygous animals.
This study described that relationship between the polymorphisms at lipogenic loci and feeding systems in Modicana cows affected some milk production traits but further research are required to describe and better understand the variations in milk traits, within and between the breeds, not only through a genetic or nutritional point of view but as a dynamic interaction between these two aspects.|
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|MLTVNT83E58H163W-PhD Thesis_Valentina Moltisanti.pdf||PhD Thesis_Valentina Moltisanti||1,56 MB||Adobe PDF||Visualizza/apri
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