Effect of olive pomace and extruded linseed on milk yield and fatty acid composition from dairy ewes

Use of extruded linseed (EL) in the diet of dairy ewes is an effective strategy to enrich milk with omega-3 polyunsaturated fatty acids (PUFA n-3) and conjugated linoleic acid (CLA). However, since EL is largely bio- hydrogenated in the rumen, the amount of extruded linseed needed to obtain an effective enrichment of PUFA n-3 in milk fat may often result in an increase of feeding cost. The use of polyphenols in the diet of dairy ruminants has been proposed as strategy to perturb rumen biohydro- genation of dietary PUFA and to increase the passage rate of PUFA omega-3 from the diet to milk. Crude phenolic concentrate (CPC) obtained by membrane filtration of olive vegetation waters to reduce their pollutant charge could be considered a good source of polyphenols, mainly secoridoides derivatives. The aim of this study was to evaluate the effect of the inclusion of linseed and CPC in diets of dairy ewes on milk yield and fatty acid (FA) composition. Twenty pluriparous Comisana ewes were randomly allotted into four groups after a baseline period of three weeks, when the animals received the same dietary reg- imen based on alfalfa hay and a concentrate feed poor in lipids. Subsequently, the four experimental diets were based on alfalfa hay ad libitum administrated and 800 g/head and day of a concentrate feed con- taining: linseed (L diet) or linseed plus different quantity of CPC to pro- vide 0.4 (L0.4), 0.8 (L0.8) or 1.2 (L1.2) g/kg DM of polyphenols. The trial lasted 5 week, individual milk yield was weekly recorded and analysed for proximate and FA composition. Data were analysed by a repeated measure model. The inclusion of EL and CPC in the diet of dairy ewes did not affect milk yield and proximate composition, however, at the maximum dose, CPC resulted in a significant increase of linoleic and alpha-linolenic acid by 18% and 24%, respectively, if compared to milk fat from ewe fed L diet. At the same time, milk fat from ewe fed L1.2 diet was lower in t11 18:1, CLA content (-38% for both FA) and other intermedi- ates of the biohydrogenation process, probably as a consequence of a perturbing effect of OP on rumen bacteria responsible of the biohydro- genation of dietary PUFA. In conclusion, addition of OP to diet supple- mented with EL enhanced the content of PUFA in milk fat from dairy ewes, without affecting productive performance of the animals.