Length of concentrate finishing affects the fatty acid composition of grass-fed and genetically lean beef: an emphasis on trans-18:1 and conjugated linoleic acid profiles

Abstract

Intensively finishing cattle on a high-grain diet is generally used to enhance marbling, whereas extensively finishing on grass is known to provide improved muscle fatty acid profiles. The objective of this study was to evaluate to what extent intensive concentrate finishing (0, 1 or 2 months) can be combined with forage feeding without negatively affecting the fatty acid profile of genetically lean animals. Bulls from the ‘Asturiana de los Valles’ breed were reared under grazing conditions with/without final finishing on a barley-based concentrate: 0 months (control;n= 7), 1 month (n= 10) and 2 months (n= 7). Yearling bulls were slaughtered commercially at an average live weight of 516 ± 9.8 kg. Increasing the finishing time on concentrate significantly increased the saturated and monounsaturated fatty acids, whereas polyunsaturated fatty acids (PUFAs) tended to decrease and it was not possible to increase the long-chain PUFA content in muscle tissue of this breed. An increase was observed for totaltrans-18:1 (average 5.5% with grainv.3.7% for grass). The 11t-18:1/10t-18:1 ratio was significantly higher in grass-fed (average 8.1) compared with grain-finished animals (average 1.1). Grass or limited concentrate finishing reduced the n-6/n-3 ratio in muscle tissue (average 3.6 for 0 and 1 month, and 4.9 for 2 months on grain finishing). The beef was within or close to the recommended values for human consumption (i.e. polyunsaturated/saturated > 0.45, n-6/n-3 < 4.0), and totaltrans-FA content was low. However, finishing increased the content of undesirabletrans-18:1 and conjugated linoleic acid isomers, particularly after 2 months, whereas grass finishing was judged to provide a healthier beef fatty acid profile.

Finishing strategies for steers based on pasture or silage plus grain and time on feed and their effects on beef quality

“…Similarly, Klee et al (2011) found higher n-6:n-3 ratios in tenderloin and round cuts from steers fed on pasture plus oat grain than in those cuts from steers fed only on pasture. Aldai et al (2011) reported lower n-6:n-3 ratios in beef from steers finished on pasture than from those fed on intensive grains (primarily barley). Additionally, the highest n-6:n-3 ratio was found in beef from steers fed grain for two months compared with one month.…”

“…The percentages of C18:0, CLA c-9 t-11, C18:3 n-3, C20:5 n-3, and C22:5 n-3 were higher for beef from the SW than from the LW treatment (P≤0.05), whereas there were no differences between the oat treatments. Aldai et al (2011) reported that beef from steers finished for two months on grains (primarily barley) had similar levels of CLA c-9 t-11, C20:5 n-3, and C22:5 n-3 but a lower level of C18:3 n-3 than beef finished for one month on grains. Aldai et al (2012) highlighted that the concentrations of fiber and starch in the rumen affected the fatty acid metabolism.…”

Recent developments in altering the fatty acid composition of ruminant-derived foods

“…Recent investigations have identified mRNA encoding the elongase and desaturase responsible in bovine tissues (Cherfaoui et al, 2012). Concentrates rich in 18:2n-6 result in higher concentrations of 18:2n-6 and associated longer-chain derivatives in the muscle of cattle (Warren et al, 2008;Aldai et al, 2011;Juá rez et al, 2011) and sheep (Nuernberg et al, 2005;Radunz et al, 2009;Turner et al, 2012a).…”

“…finishing on high-concentrate diets, rearing of cattle or lambs on forage-based systems is often associated with a decrease in muscle 16:0 and total SFA and higher cis-9 18:1 concentrations Sinclair, 2007;Alfaia et al, 2009;Aldai et al, 2011). Replacing grass silage with wholecrop wheat silage (Noci et al, 2005b) or maize silage ) increased in the n-6 : n-3 ratio of muscle, whereas wilting grass before ensiling decreased this ratio (Noci et al, 2007b).…”

Contenido de ácidos grasos en carne de bovinos cebados en diferentes sistemas de producción en el trópico colombiano

“…No hubo diferencias en contenido de ácido linoleico (Tabla 3), distinto a lo publicado por otros reportes científicos, donde se observó, que el porcentaje de linoleico en animales alimentados con pastura y forrajes fue el segundo más abundante después del oleico (21). Además el forraje es una fuente importante de linoleico, lo que influye en el contenido del mismo en carne.…”