Enhancing the n-3 polyunsaturated fatty acid (PUFA) content of beef is important in view of the
generally saturated nature of fatty acids in ruminant meats and the negative effect this can have
on human health. This study examined the effects of different sources of dietary n-3 PUFA on
the performance of steers and the fatty acid composition of m. longissimus thoracis muscle and
associated subcutaneous adipose tissue. Animals were fed ad libitum on grass silage plus one of
four concentrates (60:40 forage:concentrate on a DM basis) containing differing sources of
lipid: Megalac (16:0), lightly bruised whole linseed (18:3n-3), fish oil (20:5n-3 and 22:6n-3) and
a mixture of linseed and fish oil (1:1, on an oil basis). Diets were formulated so that total dietary
oil intake was 6 %, approximately half of which was from the experimental test oil. Linseed
feeding not only increased the levels of 18:3n-3 in muscle phospholipid from 9´5 to 19 mg/
100 g muscle but also enhanced the synthesis of 20:5n-3, the level of which increased from 10
to 15 mg/100 g muscle. Linseed also increased the proportion of 18:3n-3 in muscle neutral lipid
and in adipose tissue lipids by a factor of 1´64 and 1´75 respectively. Fish oil feeding doubled
the proportion of 20:5n-3 and 22:6n-3 in muscle phospholipids. The proportion of 18:1 trans in
muscle neutral lipid was higher on the n-3 PUFA diets than the control diet, 0´04 and 0´02
respectively. Despite the implied modification to rumen metabolism, lipid source did not affect
feed intake, growth rate, cold carcass weight or carcass fatness, but carcass conformation score
was higher on fish oil treatments
P , 0´05: However, total muscle fatty acid content was not
different between treatments and ranged from 3´5±4´3 % of tissue weight. The increase in n-3
PUFA in the meat produced by feeding linseed or fish oil lowered the n-6:n-3 ratio but had little
effect on the P:S ratio.
Enhancing the n-3 polyunsaturated fatty acid (PUFA) content of beef is important in view of the
generally saturated nature of fatty acids in ruminant meats and the negative effect this can have
on human health. This study examined the effects of different sources of dietary n-3 PUFA on
the performance of steers and the fatty acid composition of m. longissimus thoracis muscle and
associated subcutaneous adipose tissue. Animals were fed ad libitum on grass silage plus one of
four concentrates (60:40 forage:concentrate on a DM basis) containing differing sources of
lipid: Megalac (16:0), lightly bruised whole linseed (18:3n-3), fish oil (20:5n-3 and 22:6n-3) and
a mixture of linseed and fish oil (1:1, on an oil basis). Diets were formulated so that total dietary
oil intake was 6 %, approximately half of which was from the experimental test oil. Linseed
feeding not only increased the levels of 18:3n-3 in muscle phospholipid from 9´5 to 19 mg/
100 g muscle but also enhanced the synthesis of 20:5n-3, the level of which increased from 10
to 15 mg/100 g muscle. Linseed also increased the proportion of 18:3n-3 in muscle neutral lipid
and in adipose tissue lipids by a factor of 1´64 and 1´75 respectively. Fish oil feeding doubled
the proportion of 20:5n-3 and 22:6n-3 in muscle phospholipids. The proportion of 18:1 trans in
muscle neutral lipid was higher on the n-3 PUFA diets than the control diet, 0´04 and 0´02
respectively. Despite the implied modification to rumen metabolism, lipid source did not affect
feed intake, growth rate, cold carcass weight or carcass fatness, but carcass conformation score
was higher on fish oil treatments
P , 0´05: However, total muscle fatty acid content was not
different between treatments and ranged from 3´5±4´3 % of tissue weight. The increase in n-3
PUFA in the meat produced by feeding linseed or fish oil lowered the n-6:n-3 ratio but had little
effect on the P:S ratio.
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