Effect of slaughter age and feeding system on the neutral and polar lipid composition of horse meat.

This study was undertaken to provide a thorough analysis of the neutral lipid (NL) and polar lipid (PL) fractions of horse meat that included the content and distribution of acyl and alkenyl moieties in foals under different rearing conditions. Two groups of crossbred horses were studied; the first group was selected from suckling foals produced under grazing conditions and slaughtered at 4 months of age (n=8), and the second group was selected from concentrate-finished foals and slaughtered at 12 months of age (n=7). There were significant differences related to the age and feeding practices of foals which affected the intramuscular (IM) fat content and the fatty acid (FA) composition of NL and PL fractions. Samples from suckling foals were leaner and provided the highest content of methylation products from the plasmalogenic lipids, and total and n-3 polyunsaturated fatty acid (PUFA). By contrast, the meat from concentrate-finished foals had a higher IM fat level resulting in a greater accumulation of 16:0 and total monounsaturated FAs in the NL fraction, whereas the muscle PL fraction retained a similar FA composition between both groups. Linolenic acid was preferentially deposited in the NL fraction, but linoleic acid and the long-chain n-3 and n-6 PUFAs were incorporated into the PL fraction where they served as cell membrane constituents and in eicosanoid formation.

Effects of linseed and quercetin added to the diet of fattening lambs on the fatty acid profile and lipid antioxidant status of meat samples.

Thirty-two Merino lambs fed barley straw and a concentrate formulated either with palm oil (CTRL group) or with linseed (+LS group), both alone or supplemented with quercetin (+QCT group or +LS+QCT group) were used to assess the effects of these dietary supplements on meat quality attributes. After being slaughtered, the longissimus thoracis muscles were used to study the fatty acid (FA) profile in detail, whilst longissimus lumborum slices were stored under refrigerated conditions to determine the lipid stability. Linseed increased the content of highly unsaturated n-3 long-chain fatty acid (20:5n-3; 22:5n-3; 22:6n-3). Interestingly, a significant increment of rumenic acid content (9c,11t-18:2) was observed when this seed was administered together with dietary quercetin. Moreover, the feeding of quercetin resulted in a reduction in the proportion of saturated FA and a decrease in lipid peroxidation of meat when the lambs were fed linseed. In conclusion, from both a nutritional and a commercial (shelf-life) point of view, it may be useful to include a source of quercetin when lambs are fed linseed diets.

Estimates of genetic parameters for fatty acids in brisket adipose tissue of Canadian commercial crossbred beef steers.

Heritability and genetic and phenotypic correlations between 15 individuals and 10 groups of fatty acids with a concentration greater than 0.5% in the brisket adipose tissue of 223 Angus and Charolais based crossbred commercial steers were estimated using univariate and bivariate animal models. Individual saturated fatty acids were low to moderately heritable, with heritability estimates ranging from 0.05 (C16:0) to 0.31 (C15:0). Individual monounsaturated fatty acids were low to moderately highly heritable ranging from 0.04 (9c C17:1 and 11c C18:1) to 0.51 (9c C14:1). Polyunsaturated fatty acid C18:2n-6 was moderately heritable (0.17). Among groups of fatty acids, heritability estimates ranged from 0.03 for branched chain fatty acid (BCFA) and n-6/n-3 to 0.16 for n-6 and Health Index. A range of low (0.00) to high (1.00) phenotypic and genetic correlations was observed among the 25 fatty acids considered in this study. In general, fatty acids such as conjugated linoleic acid (CLA) and 11t C18:1, with potential health benefits, showed significant antagonistic correlations with unhealthy fatty acids such as C14:0 and C16:0. The results from this study provide insight into the direct genetic control of host genes on fatty acid composition of beef tissues and will facilitate designs of genetic selection and/or genetic based diet management to improve fatty acid composition in beef cattle.

Association analyses of DNA polymorphisms in bovine SREBP-1, LXRα, FADS1 genes with fatty acid composition in Canadian commercial crossbred beef steers.

Two previously reported DNA polymorphisms of sterol regulatory element binding transcription factor 1 (SREBP-1) and liver X receptor alpha (LXRα) and two DNA polymorphisms of fatty acid desaturase 1 (FADS1) were evaluated for associations with fatty acids in brisket adipose tissue of Canadian crossbred beef steers. The polymorphism of 84 bp insert/deletion in intron 5 of SREBP-1 was significantly associated with the concentration of 9c C17:1 (P=0.013). The G>A single nucleotide polymorphism (SNP) in the exon 4 of LXRα gene was associated with the concentration of 9c, 11t C18:2 (P=0.04), sum of conjugated linoleic acids (CLA) (P=0.025) and 11c C20:1(P=0.042). Two DNA polymorphisms in the promoter region of FADS1, deletion/insertion of →GTG in rs133053720 and SNP A>G in rs42187276, were significantly associated with concentrations of C17:0 iso, C17:0 ai, total branched chain fatty acids (BFA), 12t C18:1, 13t/14t C18:1, 15t C18:1, and 13c C18:1 (P<0.05). Further studies are needed to validate the associations and to delineate the roles of the gene polymorphisms in determining the fatty acid composition in beef tissues.

Influence of α-tocopherol supplementation on trans-18:1 and conjugated linoleic acid profiles in beef from steers fed a barley-based diet.

The current study was conducted to determine the effect of different α-tocopherol (vitamin E) inclusion levels on trans(t)-18:1 and conjugated linoleic acid (CLA) profiles in subcutaneous and intramuscular fat of steers fed a barley-based diet. Fifty-six feedlot steers were offered a barley-based finisher diet (73% steam rolled barley, 22% barley silage and 5% supplement as-fed basis) with four levels of supplementary dl-α-tocopheryl acetate (340, 690, 1040 or 1740 IU/steer per day) for 120 days. Adding vitamin E to the diet had little effect on the overall fatty acid composition of intramuscular fat. The proportion of individual and total t,t- and cis(c),t-CLA, n-3 fatty acids, total polyunsaturated fatty acids (PUFA), mono-unsaturated fatty acids and saturated fatty acids to PUFA ratio in subcutaneous fat were not influenced (P > 0.05) by dietary vitamin E supplementation. Increasing levels of vitamin E led to linear reductions in t6-/t7-/t8-18:1 and t10-18:1 (P < 0.05), and linear increase in t11-/t10-18:1 ratio (P < 0.05) in subcutaneous fat. The content of 20:3n-6 and total n-6 in subcutaneous fat decreased (P < 0.05) linearly with increasing amounts of vitamin E. The subcutaneous fat n-6:n-3 ratio showed a quadratic (P < 0.05) response to vitamin E. In conclusion, although vitamin E supplementation has some potential to reduce t10-18:1 formation and increase t11-/t10-18:1 ratio in subcutaneous fat of cattle fed barley-based diets, the changes in the present study were limited and may not have been sufficient to impact on human health.

The labile lipid fraction of meat: from perceived disease and waste to health and opportunity.

The fatty acid composition of beef and pork has been stigmatized due to their relationships with several diseases from cardiovascular disease to cancer. Meat lipids are, however, one of the few components of meat that can be modified in content and composition, and can present opportunities for value added production and health promotion. Until regulations and policies are in place to define requirements for fatty acid enrichment, however, the process remains relatively academic. Once practical goals are in place for fatty acid enrichment in meat, both theory and practice need to converge for successful production of fatty acid enriched meat. The present review covers aspects of policy in Canada, and requirements for research networks to respond to theoretical and practical challenges associated with production of fatty acid enriched meat. Finally, needs for education and marketing are outlined which must be in place to truly realize a transition of meat lipids from perceived disease and waste to health and opportunity.

Evaluation of rumen fatty acid hydrogenation intermediates and differences in bacterial communities after feeding wheat- or corn-based dried distillers grains to feedlot cattle.

The effect of partially replacing rolled barley (86.6% of control diet) with 20% wheat dried distillers grains plus solubles (DDGS), 40% wheat DDGS, 20% corn DDGS, or 40% corn DDGS (dietary DM basis) on rumen fluid fatty acid (FA) composition and some rumen bacterial communities was evaluated using 100 steers (20 per treatment). Wheat DDGS increased the 11t- to 10t-18:1 ratio (P < 0.05) in rumen fluid and there was evidence that the conversion of trans-18:1 to 18:0 was reduced in the control and wheat DDGS diets but not in the corn DDGS diet. Bacterial community profiles obtained using denaturing gradient gel electrophoresis and evaluated by Pearson correlation similarity matrices were not consistent for diet and, therefore, these could not be linked to different specific rumen FA. This inconsistency may be related to the nature of diets fed (dominant effect of barley), limited change in dietary composition as the result of DDGS inclusion, large animal-to-animal variation, and possibly additional stress as a result of transport just before slaughter. Ruminal densities of a key fiber-digesting bacteria specie that produces 11t-18:1 from linoleic and linolenic acids (Butyrivibrio fibrisolvens), and a lactate producer originally thought responsible for production of 10t,12c-18:2 (Megasphaera elsdenii) were not influenced by diet (P > 0.05).

Association analyses of single nucleotide polymorphisms in bovine stearoyl-CoA desaturase and fatty acid synthase genes with fatty acid composition in commercial cross-bred beef steers.

Two previously reported non-synonymous coding single nucleotide polymorphisms (SNPs) of bovine stearoyl-CoA desaturase (delta-9-desaturase) (SCD) (c.878C>T) and fatty acid synthase (FASN) (g:17924A>G) were assessed for their associations with 72 individual and 12 groups of fatty acids in brisket adipose tissue of 223 Canadian commercial cross-bred beef steers. It was found that the 'CC' genotype of the SCD SNP was significantly associated with lower concentrations of saturated fatty acids (SFA) including 10:0, 14:0 and 20:0, higher concentrations of monounsaturated fatty acids including 9c-14:1, 12c-16:1 and 13c-18:1, higher concentrations of polyunsaturated fatty acids (PUFA) including 9c,15c-18:2, 10c,12c-18:2, 11c,13t-18:2 and 12c,14t-18:2, but lower concentrations of other PUFA of 9c,13t/8t,12c and 20:2n-6 (P < 0.05). The 'AA' genotype of the FASN SNP was significantly associated with higher concentrations of SFAs of 10:0, 12:0, 13:0, 14:0 and 15:0, lower concentrations of unsaturated fatty acids of 9c-18:1 and 20:3n-6, and higher concentrations of unsaturated fatty acids of 9c-14:1 and 12c-16:1 (P < 0.05). Significant epistatic effects between the SCD and FASN SNP genotypes were also found for several fatty acids including 10:0, 23:0, 6t/7t/8t-18:1, 12t-18:1, 13t/14t-18:1, 16t-18:1, total trans18:1 and 9c,13t/8t,12c-18:2 (P < 0.05). These results further suggest that SCD and FASN are strong candidate genes influencing fatty acid composition in beef cattle.

Feeding flaxseed in grass hay and barley silage diets to beef cows increases alpha-linolenic acid and its biohydrogenation intermediates in subcutaneous fat.

The objective of the study was to determine temporal fat deposition and fatty acid profiles in beef cows fed hay- or barley silage-based diets, with or without flaxseed. Crossbred cull beef cows (n = 64, >30 mo of age, 620 ± 5 kg) were removed from grassland pastures, randomly assigned to 16 pens, and given ad libitum access to 50:50 (wt/wt, DM basis) forage:concentrate diets containing 0 or 15% ground flaxseed (DM basis, 5.2% added fat). Diets consisted of hay control (HC), hay+flaxseed (HF), barley silage control (SC), and silage+flaxseed (SF). Backfat biopsies were obtained from each cow at 0, 6, and 12 wk, and at slaughter (~20 wk) to assess fatty acid composition. With the exception of feed efficiency, flaxseed × forage interactions were not significant for backfat accumulation or performance parameters. Flaxseed improved (P < 0.01) feed conversion when supplemented to hay-based diet and increased ADG (P = 0.03), resulting in a heavier (P = 0.02) BW. Compared with hay, barley silage increased (P < 0.01) DMI, ADG, and feed efficiency. Subcutaneous fat contained 0.68% n-3 fatty acids at wk 0, and reached 0.68, 0.81, and 0.94% in HF cows after 6, 12, and 20 wk, respectively (Y(n-3) = 0.0133X + 0.6491, r = 0.87). It was 0.67% at wk 0, and reached 0.65, 0.77, and 0.90% in SF cows after 6, 12, and 20 wk, respectively (Y(n-3) = 0.0121X + 0.6349, r = 0.75). In contrast, weight percentage of n-3 fatty acids decreased in HC cows from 0.63, 0.50, and 0.47, to 0.43%, and in SC cows from 0.63, 0.40, and 0.36, to 0.33% over the 20 wk. A forage × flaxseed interaction (P < 0.05) occurred for many of the α-linolenic acid (ALA) biohydrogenation intermediates, including vaccenic acid (C18:1 trans-11) and CLA (combined C18:2 trans-7,cis-9 and cis-9,trans-11) in plasma, and in subcutaneous fat this also included non-CLA dienes. Concentrations of most α-linolenic acid biohydrogenation intermediates were greater when feeding flaxseed with hay. In conclusion, forage source altered plasma concentrations and rate of accumulation of ALA biohydrogenation products in subcutaneous fat from beef cows fed flaxseed. Factors responsible for this response are yet to be defined, but may include forage-mediated changes in ruminal biohydrogenation of ALA, as well as alterations in fatty acid metabolism and deposition.

The effects of feeding flaxseed to beef cows given forage based diets on fatty acids of longissimus thoracis muscle and backfat.

This study was conducted to investigate changes in fatty acid profiles of beef cows fed grass hay or barley silage based diets, with or without flaxseed supplementation. Both flaxseed and hay feeding increased levels of α-linolenic acid (LNA; 18:3n-3) in longissimus thoracis and backfat (P<0.001). A forage type by flaxseed level interaction was observed for most LNA biohydrogenation intermediates (P<0.05) that indicated feeding hay combined with flaxseed led to the greatest levels of total conjugated linolenic acid, total conjugated linoleic acid, total non-conjugated dienes and total trans-18:1. Predominant biohydrogenation intermediates included t11,c15-18:2, rumenic acid (c9,t11-18:2) and vaccenic acid (t11-18:1).

Increasing omega-3 levels through dietary co-extruded flaxseed supplementation negatively affects pork palatability.

To clarify the impact of feeding co-extruded flaxseed on carcass quality and pork palatability, 96 pigs (48 barrows and 48 gilts) were fed three different levels of flaxseed (0%, 5% and 10% of dietary intake) for 76days. Carcass quality and meat quality characteristics of pure loin muscle and ground pork (20% fat) were evaluated. Fat hardness and belly firmness decreased (P<0.001) with increasing co-extruded flaxseed. Pigs fed co-extruded flaxseed levels had higher lean yield (P=0.045) and total lean content (P=0.034). Loin from barrows had higher fat content compared to gilts (P<0.001). Co-extruded flaxseed supplementation increased (P<0.001) omega-3 content in loin and ground pork. Pork flavour intensity and off-flavour intensity scores lowered (P<0.001) with increasing levels of co-extruded flaxseed, being more accentuated (P=0.023) in reheated pork chops from barrows. Diet affected all texture and flavour sensory characteristics (P<0.05) as tissue levels of omega-3 fatty acids increased, likely as a result of increased lipid oxidation.

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.

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 total trans-18:1 (average 5.5% with grain v. 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 total trans-FA content was low. However, finishing increased the content of undesirable trans-18:1 and conjugated linoleic acid isomers, particularly after 2 months, whereas grass finishing was judged to provide a healthier beef fatty acid profile.

Comparison of wheat- versus corn-based dried distillers' grains with solubles on meat quality of feedlot cattle.

A considerable amount of information has been generated on the feeding value and impact of corn dried distillers' grains with solubles (DDGS) on meat quality, whereas little is known about the effects of wheat DDGS on meat quality, and no direct comparison of these two sources of DDGS has been completed. The current study was conducted to examine the objective and subjective carcass and meat quality traits of cattle fed diets containing corn or wheat (20% or 40%) DDGS (DM basis) as compared to a standard barley-based finishing diet (control). In general, meat obtained from animals fed the barley-based control diet was slightly darker in colour (lower chroma and hue at 24 h, P<0.01) and less tender (highest proportion of tough shears at 2 d and lowest proportion of tender shears at 20 d). Meat from corn DDGS was rated as more tender and palatable than control samples (P<0.05), and 20% corn samples were rated better for beef flavour intensity (P<0.01) and desirability (P<0.05) than 40% corn DDGS samples. In contrast, meat from steers fed wheat DDGS showed intermediate characteristics between steers fed control and corn DDGS diets. Hence, feeding wheat DDGS had no negative effects, and feeding corn DDGS had some positive effects on meat quality characteristics of beef.

Feeding co-extruded flaxseed to pigs: effects of duration and feeding level on growth performance and backfat fatty acid composition of grower-finisher pigs.

To examine the effect of co-extrusion on subsequent n-3 fatty acids in pig tissues, 8 pigs (barrows and gilts) were assigned to either a control treatment or one of nine treatments arranged in a 3 x 3 factorial design with 3 levels of co-extruded flaxseed (5%, 10% and 15%) and 3 durations of feeding (4, 8 and 12 weeks). Feed conversion improved slightly (P=0.01) with increasing dietary flaxseed but feeding flax for more than 8 weeks reduced average daily gain (P=0.02). In general, the duration and level of co-extruded flaxseed feeding affected (P<0.05) most fatty acids except for 22:6n-3 (P>0.05). Increasing the duration of flax feeding led to significant quadratic effects in backfat 18:3n-3 (P<0.001) and total n-3 fatty acids (P=0.002) when feeding 5% co-extruded flaxseed. Those increases were linear (P<0.001) when feeding 10% and 15% co-extruded flaxseed. Consequently feeding higher levels of flax for shorter periods vs. lower levels for longer periods appears to be more efficient at increasing n-3 fatty acids in pig backfat, but increases appeared to be less consistent. Moreover the addition of a 50:50 mix of extruded flax/peas to pig diets provided a highly available source of 18:3n-3 yielding n-3 fatty acid enrichments in backfat comparable to studies where extracted flaxseed oil was fed. Feeding flax co-extruded with field peas can be used to optimize consistent enrichments of n-3 fatty acids in back fat and relatively small amounts of this fat could be used to manufacture pork products to meet Canadian standards for n-3 fatty acid enrichment.

Feeding wheat dried distillers grains with solubles improves beef trans and conjugated linoleic acid profiles.

In western Canada, ethanol is produced mainly from wheat. As the demand for wheat increases, so do grain prices, which in turn creates incentives for feeding reduced-cost distillers coproducts to livestock. Substitution of wheat dried distillers grains plus solubles (DDGS) for barley grain may also create opportunities for enhancing beef fatty acid profiles because reducing starch concomitantly increases dietary fiber and oil and may shift PUFA biohydrogenation toward a healthier trans and CLA profile. To study this potential, heifers were fed diets containing 0, 20, 40, or 60% wheat DDGS (DM basis) substituted for rolled barley (n = 24; 133-d finishing period). Adding DDGS increased dietary oil (from 1.9 to 3.7%), but dietary fatty acid compositions remained consistent. Feeding increasing amounts of DDGS linearly decreased total diaphragm fatty acids on a milligram per gram basis (P = 0.031). For both brisket fat and diaphragm, feeding increasing amounts of DDGS caused linear increases in percentages of 18:2n-6 (P = 0.001) and total n-6 fatty acids (P = 0.001) but did not change the concentrations of individual or total n-3 fatty acids. Feeding increasing amounts of DDGS did not change the content of total trans MUFA in either brisket fat or diaphragm but led to linear decreases in 10t-18:1 (P = 0.033, brisket fat; P = 0.004, diaphragm) and increases in 11t-18:1 (P = 0.005, brisket fat; P = 0.003, diaphragm). Feeding increasing amounts of DDGS also caused a linear increase in 9c11t-18:2 (P = 0.044, brisket fat; P = 0.023, diaphragm) and total CLA (P = 0.086, brisket fat; P = 0.039, diaphragm). Overall, feeding DDGS enhanced the fatty acid composition of beef by decreasing 10t-18:1 while increasing the major CLA isomer (9c,11t-18:2) and its precursor 11t-18:1.

Effect of breed body size and the muscular hypertrophy gene in the production and carcass traits of concentrate-finished yearling bulls.

To examine the extent of the effect of muscular hypertrophy character in beef of northern-Spanish breeds, animal performance and carcass characteristics of 152 finishing steers from 5 genotypes were studied: 32 yearling bulls from a rustic Asturiana de la Montaña (AM) breed, 96 yearling bulls from Asturiana de los Valles (AV) breed, divided in 3 groups depending on the presence of the gene responsible for double-muscling (i.e., 32 AV mh/mh, 32 AV mh/+, 32 AV +/+), and 24 yearling bulls from AM x AV cross were used. Each genotype was composed of 8 animals per year (4 animals per pen) for 4 yr, except for the AM x AV genotype, which was only evaluated in the last 3 yr of the experiment. All animals were fed indoors with concentrate meal and barley straw ad libitum. Average daily gains in AV animals (1.41 kg/d) were greater (P < 0.01) than in AM (1.12 kg/d), whereas AM x AV were intermediate (1.29 kg/d) to these. No significant differences (P = 0.604) in ADG were found among the 3 AV genotypes. Longer fattening periods (P < 0.001) were taken for AM animals to reach acceptable BW at slaughter. Double-muscled animals (AV mh/mh) were found to have the best feed efficiencies when expressed as G:F (P < 0.001). However, residual feed intake calculated on a daily basis showed a greater efficiency in AV mh/mh and AM than in other genotypes. Carcasses from double-muscled animals had greater BW, yield, conformation and compactness index, and less fat cover than the other genotypes (P < 0.001). Carcasses from AM breed were the lightest and had the worst conformation, whereas those from AM x AV generally presented intermediate characteristics between AV and AM. Double-muscled animals had the greatest LM weight and area. The sixth-rib dissection revealed a greater percentage of muscle (84.6%) and decreased percentages of subcutaneous fat (1.1%), intermuscular fat (4.7%), bone (8.5%), and other tissues (1.2%) in AV mh/mh compared with other genotypes. Water-holding capacity was greatest in AM and least in AV mh/mh. In conclusion, double-muscled AV bulls would provide the greatest economic returns at intensive feeding systems because of their greater efficiency, reduced feeding costs, greater carcass weight and conformation, and greater lean yields, though some LM characteristics (reduced fat content and water-holding capacity) could negatively affect the sensory attributes of the meat compared with other genotypes with greater fatness.

Nonionophore antibiotics do not affect the trans-18:1 and conjugated linoleic acid composition in beef adipose tissue.

The common practice in North American feedlot industries is to add antibiotics to the diet to prevent disease and improve both BW gain and feed efficiency. In this study, 240 crossbred steer calves were backgrounded on a 54% silage diet for 80 d and fed a finishing diet consisting of 81% barley grain, 10% barley silage, and 7.5% supplement (DM basis) with and without in-feed antibiotics for approximately 120 d. Calves were assigned to 1 of 5 treatments: a control with no antibiotics, 11 mg/kg of chlortetracycline, 44 mg/kg of chlortetracycline, 44 mg/kg of chlortetracycline plus 44 mg/kg of sulfamethazine, and 11 mg/ kg of tylosin phosphate. A combination of GLC and silver-ion HPLC methods was used to analyze the fatty acid composition of brisket adipose tissue, with emphasis on trans-18:1 and CLA isomers. The inclusion of nonionophore antibiotics in the diet had little effect on the fatty acid composition, except that feeding either 44 mg/kg of chlortetracycline or 11 mg/kg of tylosin caused small increases in 9c-14:1 and 16:0 relative to the control (0.26 and 0.9 g/100 g of total fatty acids, respectively). Likewise, profiles of trans-18:1 and CLA isomers were unchanged by antibiotics, but across treatments the predominant trans-18:1 isomer was 10t-18:1 (where t = trans; 3.22%) at 3 times the concentration of the second most abundant isomer (11t-18:1; vaccenic acid, 1.05%). Rumenic acid (9c,11t-18:2, where c = cis) was the major CLA isomer at 61% of total CLA, followed by 7t,9c-18:2 at 9%. Because no other effects on fatty acid composition were evident, data for trans-18:1 and CLA were pooled across treatments to investigate possible relationships among rumen PUFA metabolites. The total trans-18:1 content in brisket adipose tissue was positively correlated with 10t-18:1, but not with 11t-18:1, whereas the total CLA was positively correlated with 9c,11t-18:2, but not with 7t,9c-18:2. The 7t,9c-18:2 was, however, positively correlated with 10t-18:1 and 6t/7t/8t-18:1 but was negatively correlated with rumenic acid. These metabolic interrelationships suggest the presence of bacterial populations with distinct pathways for PUFA biohydrogenation in which either 10t-18:1 or 11t-18:1 predominate. Overall, the nonionophore antibiotics tested did not appreciably change adipose tissue composition and consequently could not be used to improve the trans-18:1 or CLA profile (i.e., increase vaccenic and rumenic acids at the expense of 10t-18:1).

Prediction of the fatty acid composition of beef by near infrared transmittance spectroscopy.

The intramuscular fat content and composition influence consumer selection of meat products. A study predicting the fatty acid (FA) profile of ground beef from the Longissimus thoracis of yearling bulls (n=100) using near infrared transmittance spectroscopy (NIT) was conducted. The samples were scanned using an Infratec 1265 Meat Analyzer which operates in transmittance mode from 850 to 1050nm. NIT technology was able to accurately predict (R(CV)(2) over 0.76) some prominent FAs such as C14:0, C16:0, C16:1cis9, C17:0, C18:1cis9 and C18:1cis11, and minor FAs like C13:0, C15:0, C17:1cis9 and C18:1cis13. When studying FA groups, NIT spectra were able to accurately predict saturated (R(CV)(2)=0.837), branched (R(CV)(2)=0.701) and monounsaturated (R(CV)(2)=0.852) FAs. In addition, NIT spectra provided useful information on the contents of conjugated linoleic acids (CLA) in beef. These results show the potential of NIT technique as a rapid and easy tool to predict the major FAs in beef, especially those located in triglycerides.

Characterisation of intramuscular, intermuscular and subcutaneous adipose tissues in yearling bulls of different genetic groups.

Fatty acid (FA) composition of intramuscular (IM, Longissimus thoracis muscle), intermuscular (IT) and subcutaneous (SC) fat of one hundred intensively fed yearling bulls with different propensities to fatten were studied. Meat samples were collected from Asturiana de los Valles bulls with different genotypes with respect to the myostatin gene (mh/mh n=24, mh/+ n=26 and +/+ n=25) and from Asturiana de la Montaña (n=25) bulls lacking the mutation responsible for double muscling and characterised by small to medium-frame size adapted to less favoured mountain areas. FA profiles were expressed as percentages of total FA (g/100g of total FA) and organised into groups (saturated (SFA), branched (BFA), monounsaturated (MUFA), C18:1trans, polyunsaturated (PUFA), n-6, n-3, conjugated linoleic acids (CLA), unsaturated (UFA)) and ratios (MUFA/SFA (M/S), PUFA/SFA (P/S), UFA/SFA (U/S), n-6/n-3). The IT depot was the most saturated and SC depot contained the most monounsaturated FAs, while IM fat had the most polyunsaturated FAs. IM fat showed the highest P/S ratio and for the n-6/n-3 ratio there were no significant differences between adipose tissue depots. In general, genotype effects were more pronounced in IM and SC fat profiles compared to the IT depot, for which no significant differences between genotypes were found in SFA, PUFA (including n-6 and n-3), UFA and most of the ratios. IM fat of mh/mh animals had the highest content of PUFA and thus the highest P/S ratio. Accordingly, the presence of the gene causing double muscling influenced the tendency to deposit carcass fat and its FA composition, mainly in IM fat. In general, when carcass fat decreased, SFA content decreased while PUFA and UFA contents increased due to the changes in their percentages.

Gas-liquid chromatographic method for analysing complex mixtures of fatty acids including conjugated linoleic acids (cis9trans11 and trans10cis12 isomers) and long-chain (n-3 or n-6) polyunsaturated fatty acids. Application to the intramuscular fat of beef meat.

The optimisation and validation of a gas-liquid chromatographic (GLC) method using direct saponification with KOH/methanol followed by a derivatization with (trimethylsilyl)diazomethane was carried out trying to overcome all the difficulties posed by the analysis of complex mixtures of fatty acids (FAs) in animal fat tissues. The presented method allowed sensitive, selective and simultaneous determination of a wide range of different FAs, including short-chain FAs, branched-chain FAs and conjugated linoleic acid isomers in the same GLC run along with other well known saturated, monounsaturated and polyunsaturated FAs. To demonstrate the feasibility of the procedure, the total FA profile of beef meat was characterised.