Milk production, composition and milk fatty acid profile from grazing ewes fed diets supplemented with Acacia cyanophylla leaves as tannins source and whole or extruded linseed

Abstract

This experiment was conducted to investigate the effects of two different forms of linseed (whole or extruded) and only leaves of Acacia cyanophylla as tannins source on milk yield and fatty acid (FA) profile in dairy ewes. Tannins are secondary compound able to interfere with protein and lipid metabolism in the rumen. For this trial, an experimental flock of forty ewes, conducted on triticale pasture, and receiving 250 g of Soya bean meal a day, was divided into four groups. Such diet was complemented by 70 g of whole linseed for the first group (SW), 70 g of extruded linseed for the second (SE), 70 g of whole linseed together with 100 g of leaves of Acacia cyanophylla for the third group (SWA) and 70 g of extruded linseed with 100 g Acacia leaves for the last one (SEA). Daily milk production varied between 628 and 692 ml/ewe without significant difference. Fat and protein percentages did not differ between groups while milk urea content (mg/dl) was much lower (P < 0.05) for groups receiving A. cyanophylla leaves only (SWA and SEA). Odd FA, undecyclic acid (C11:0) and tridecyclic acid (C13:0) increased while pentadecyclic acid (C15:0) decreased significantly with extruded linseed intake. Extruded linseed and Acacia intake (P < 0.0004; P < 0.04) induced an increase in myristic acid (C14:0). Lauric acid (C12:0) percentage clearly increased with extruded linseed (P < 0.05). Stearic acid (C18:0) and Oleic acid (C18:1 cis9) were significantly decreased with extruded linseed and with Acacia tannins supplementation. Extruded linseed induced higher levels of trans-vaccenic acid and rumenic acid (C18:2 cis9 trans11) as well as linoleic acid (C18:2 cis-9, cis-12 (n-6)) and polyunsaturated fatty acids (P < 0.01) and reduced (P < 0.01) levels of stearic acid (C18:0) and oleic acid (C18:1 cis9). A. cyanophylla leaves also reduced oleic acid, but increased minor (n-6) fatty acids as γ-linolenic acid (C18:3 cis6 cis9 cis12 (n-6)) and docosapentaenoïc acid (C22:5 cis4 cis7 cis10 cis13 cis16 (n-6)). The effect of A. cyanophylla leaves with extruded linseed amplified oleic, and docosapentaenoïc acid levels.