Fish oil (FO) in the diet alters milk fatty acid (FA) composition, enhances milk fat conjugated linoleic acid content (CLA), and also induces milk fat depression (MFD) in lactating cows (Loor et al., 2005). Even though ewes appear less prone to MFD, there is some evidence that supplementing high-concentrate diets with 10 g FO and 20 g sunflower oil (SO)/kg resulted in transient increases of milk fat content (+12%) after 3 d of supplementation, followed by a sustained decrease (up to -27%; Toral et al., unpublished). Under these circumstances, MFD in ewes was not explained by an increase in milk fat t10 c12-CLA concentration. Changes in milk FA composition were characterized by a severe reduction in 18:0 together with an increase in trans-18:1 content. Furthermore, the addition of SO and FO decreased DM intake (-19%) and reduced milk yield (-14%) which may indicate a negative impact of lipid supplements on ruminal fermentation in sheep fed high-concentrate diets. The current experiment was therefore designed to examine the effect of a mixture of SO and FO in the diet on ruminal FA profile and fermentation characteristics in ewes.

2 pages, 2 tables.--Contributed to: XIth International Symposium on Ruminant Physiology. (Clermont-Férrand (Francia), Sep 6-9, 2008).

This work was supported by Projects AGL2008-04805-C02-02 (MICINN) and CSI01B08 (Council of Castille and Leon).

Peer reviewed