Abstract
Simple SummaryGenetic selection for single-locus polymorphisms could offer suitable opportunities to rapidly improve milk traits in local unselected cattle breeds characterized by low production levels. Since these hardy breeds are generally raised in traditional extensive and semi-intensive systems, which make wide use of grazing resources, the interactive effect between genotype and feeding system is worthy of investigation. In Modicana cattle breed, milk composition and fatty acid profile were influenced by both genetic polymorphisms at the DGAT1 K232A locus and feeding systems. The milk from homozygous AA cows was associated with a more favorable fatty acid composition due to a lower percentage of total saturated fatty acids, saturated to unsaturated ratio, atherogenic index, and a greater presence of oleic acid and total unsaturated fatty acids. Our finding confirmed the important role of pasture feeding on milk composition: the high nutritional and healthy value of milk obtained in extensive systems by pasture-fed cows. The interaction between the two experimental factors also appears to play a role: in our experimental condition, it seems that high pasture feeding can resize the effect of the DGAT1 genotype on milk traits and fatty acid composition in Modicana cows.The interaction between genetic polymorphism and feeding system on milk traits and fatty acid composition was investigated in Modicana cows. Two DGAT1 K232A genotypes (AK and AA) and two feeding regimes, extensive system (EX) with 8 h of grazing without concentrate (EX) and semi-intensive systems (SI) with 2 h of grazing with concentrate, were investigated. DGAT1 genotype did not influence milk yield and composition. The feeding system affected milk composition: protein was significantly higher in SI and lactose in the EX system. A significant genotype × feeding system interaction was observed: the protein and casein levels of AK cows were higher in the SI compared to the EX system. Milk fatty acids profile, total saturated to total unsaturated fatty acids, n-6 to n-3 ratios, and atherogenic index were affected by the feeding system, improving the healthy properties of milk from animals reared in the extensive system. DGAT1 genotype influenced the fatty acid composition: milk from AA cows had a more favorable fatty acid composition due to lower total saturated fatty acids, saturated to unsaturated ratio, atherogenic index, and higher levels of oleic acid and total unsaturated fatty acids. Furthermore, an interaction genotype x feeding system was observed: the AK milk was richer in short-chain FAs (C4:0–C8:0) and C10:0 only in the EX but not in the SI system. Our data suggest that a high amount of green forage in the diet of Modicana cows can resize the effect of the DGAT1 genotype on milk traits and fatty acids composition.
Highlights
In cattle, feeding systems greatly affect milk quality traits such as chemical and fatty acid composition
The feeding system affected the percentage of milk protein, which was significantly higher in the SI farm, and lactose, significantly higher in the extensive system (EX) farm
A genotype × feeding system interaction was observed for the percentage of protein and casein, both significantly higher in the heterozygous AK cows reared in the SI as compared to heterozygous AK cows reared in the EX system (Figure 1)
Summary
In cattle, feeding systems greatly affect milk quality traits such as chemical and fatty acid composition. Bovine milk fatty acids composition is a complex trait affected by genetic and environmental factors, such as breed, diet, and stage of lactation [2,3,4]. One of the major QTL affecting milk fat composition in dairy cattle is located in the centromeric region of BTA14 and includes the DGAT1 gene that encodes for the diacylglycerol acyltransferase1 [7]. This enzyme catalyzes the final step of triglyceride synthesis by the esterification of fatty acyl-CoA to the sn-3 position of diacylglycerol [8]. The K variant has been associated with increased milk fat percentage and saturated fatty acids [11,12,13,14,15,16,17]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
