Effects of substitution of a proportion of the concentrate in grass silage/concentrate-based diets with extruded linseed on performance and meat quality of dairy bulls

This study investigated effects of substituting a proportion of the concentrate in a grass silage:concentrate-based diet with 0, 400, 800 or 1200 g extruded linseed/head/day on the performance and meat quality of dairy bulls. Forty-eight dairy-breed bulls (i.e. 18 Holstein-Friesian, 6 Norwegian, 4 Norwegian × Holstein-Friesian, 12 Holstein × Norwegian and 8 Jersey × Holstein-Friesian), initial live weight (LW) and age 350 ± 30.9 kg and 11 ± 0.7 months, respectively were used. Grass silage was fed ad libitum and concentrates were fed daily on top of the silage. Concentrate intake was adjusted to ensure that total metabolizable energy intake from the supplement component of the diet (i.e. concentrate plus linseed) was constant among all treatments. Animals were slaughtered at a target LW at slaughter of 540 kg and so were slaughtered in three batches after 120, 147 and 185 days on experiment. Substitution of a proportion of the concentrate diet with extruded linseed had no effects on animal performance (i.e. dry matter intake, LW gain or carcass characteristics). Meat quality, in terms of cooking loss, sarcomere length, Warner Bratzler Shear Force, Commision Internationale de l’Eclairage (CIELAB) colour parameters L*, a*, b*, C* and Hue angle were not affected by dietary treatment. Substitution of a proportion of the concentrate diet with extruded linseed decreased palmitic acid (C16:0) and arachidonic acid (C20:4) concentrations (P<0.05), saturated:unsaturated fatty acid (FA) ratio (P<0.05) and the n-6:n-3 polyunsaturated FA (PUFA) ratio (P<0.001) in muscle. Trans vaccenic acid (C18:1 t11), α-linolenic acid (C18:3n-3), n-3 PUFA (P<0.05) and the ratio of PUFA:saturated (P:S) FA (P<0.01) in muscle were increased by the linseed treatment. Results demonstrate the ability to manipulate the FA composition of the meat of dairy bulls by substituting a proportion of the concentrate diet with extruded linseed, with no detrimental effects on their performance or instrumental meat quality.