Pasture and extruded linseed influence on milk quality and ricotta sensory characteristic

Take home Message Adding extruded linseed to dairy ewes’ diet when pasture is lacking improves milk parameters. Ricotta made from such milk results in having better sensorial qualities in comparison to standard product. Introduction In central Italy (Lazio and Abruzzo regions) the diet of dairy ewes is almost exclusively based on pasture during summer, spring and autumn, while during winter they kept indoors and given a standard feeding (hay and grains). Ricotta is a milk product highly associated with freshness and low-fat and thus considered as healthy food. Seasonal feeding alteration can impact the quality of the product. The aim of this study was to evaluate the possibility of using extruded linseed with the purpose of maintain the quality of milk and ricotta when pasture is scarce. Material and methods 54 ewes of Comissana breed (farm located in Lazio, Central Italy) were randomly divided into three groups of equal size. Each group was fed one of three experimental diets: 1) Pasture (P)- typical pasture grazing; 2) Enriched diet (L)- supplemented with 0.190 kg of extruded linseed; 3) Farm diet (F)- typical winter ration (control group). The experimental diets were administered for 80 days in total. The first month after delivery, the ewes milk was used for lamb production, as traditionally common in this parts. After this first period they were milked twice a day and weekly bulk milk was sampled and analysed for chemical composition and lipid profile analysis. Ricotta was obtained from this milk using traditional methods (by whey protein coagulation) and sensory panel was then performed using a modified protocol from Pizzillo et al. (2005). Before milk analysis, the data on fatty acid composition were processed to compute the Δ9-desaturase activity index as the C14:0/C14:1 ratio (Addis et al., 2005), and the atherogenic index was calculated according to Chilliard et al. (2000). The data on milk fatty acids and structure was analysed using ANOVA. For models used for milk sampling time was not included because it was found not to be significant (P>0.05). The final model included the fixed effect of dietary treatment and the residual error expressed as Yij = +Di +εij. The sensory test data were normalised, then subjected to analysis of variance for repeated measures, with diet as sole factor. Duncan’s test was used to determine the groups significantly different from each other. Results & Discussion Milk from the L group had higher fat content (44.75 %DM, 5.21% total) while P group had higher content of milk proteins (L 4.25%; F 4.76%). Fatty acid analysis of milk resulted with distinct differences. L group had higher n-3, n-6 FA and P group was higher on 9-desaturas index and IA (Table 1). In ricotta sensory panel Greasiness and Spreadability were highest in L group, while in parameter of Whiteness group P scored the lowest