Research has shown both production and health benefits for the use of chicory (Cichorium intybus) within ruminant diets. Despite this, little was known about the effects of this forage, containing differing fatty acid profiles and secondary plant compounds compared with ryegrass, on beef stability, fatty acid composition or sensory properties. An experiment was conducted to investigate whether the inclusion of chicory in the diet of grazing beef steers would alter these three properties in the M. Longissimus muscle when compared with beef steers grazing perennial ryegrass (Lolium perenne). Triplicate 2 ha plots were established with a chicory (cv. Puna II)/perennial ryegrass mix or a perennial ryegrass control. A core group of 36 Belgian Blue – cross steers were used within a 2-year beef finishing experiment (n=6/replicate plot). In the 2nd grazing year, steers were slaughtered as they reached a target fat class of 3. Muscle pH was checked 2 and 48 h post-slaughter. A section of the hindloin joint containing the M. Longissimus lumborum muscle was removed and a 20 mm-thick steak was cut and muscle samples were taken for analysis of vitamin E and fatty acid analysis. The remaining section of the loin was vacuum packed in modified atmosphere packs and subjected to simulated retail display. A section of the conditioned loin was used for sensory analysis. Data on pH, vitamin E concentration and colour stability in a simulated retail display showed there were no effects of including chicory in the diet of grazing beef steers on meat stability. There were also no differences found in the fatty acid composition or the overall eating quality of the steaks from the two treatments. In conclusion, there were no substantive effects of including chicory in the swards of grazing beef cattle on meat stability, fatty acid composition or sensory properties of the M. Longissimus muscle when compared with beef steers grazing ryegrass-only swards.

There is increasing evidence to indicate that nutrition is an important factor involved in the onset and development of several chronic human diseases including cancer, cardiovascular disease (CVD), type II diabetes and obesity. Clinical studies implicate excessive consumption of medium-chain saturated fatty acids (SFA) and trans-fatty acids (TFA) as risk factors for CVD, and in the aetiology of other chronic conditions. Ruminant-derived foods are significant sources of medium-chain SFA and TFA in the human diet, but also provide high-quality protein, essential micronutrients and several bioactive lipids. Altering the fatty acid composition of ruminant-derived foods offers the opportunity to align the consumption of fatty acids in human populations with public health policies without the need for substantial changes in eating habits. Replacing conserved forages with fresh grass or dietary plant oil and oilseed supplements can be used to lower medium-chain and total SFA content and increase cis-9 18:1, total conjugated linoleic acid (CLA), n-3 and n-6 polyunsaturated fatty acids (PUFA) to a variable extent in ruminant milk. However, inclusion of fish oil or marine algae in the ruminant diet results in marginal enrichment of 20- or 22-carbon PUFA in milk. Studies in growing ruminants have confirmed that the same nutritional strategies improve the balance of n-6/n-3 PUFA, and increase CLA and long-chain n-3 PUFA in ruminant meat, but the potential to lower medium-chain and total SFA is limited. Attempts to alter meat and milk fatty acid composition through changes in the diet fed to ruminants are often accompanied by several-fold increases in TFA concentrations. In extreme cases, the distribution of trans 18:1 and 18:2 isomers in ruminant foods may resemble that of partially hydrogenated plant oils. Changes in milk fat or muscle lipid composition in response to diet are now known to be accompanied by tissue-specific alterations in the expression of one or more lipogenic genes. Breed influences both milk and muscle fat content, although recent studies have confirmed the occurrence of genetic variability in transcript abundance and activity of enzymes involved in lipid synthesis and identified polymorphisms for several key lipogenic genes in lactating and growing cattle. Although nutrition is the major factor influencing the fatty acid composition of ruminant-derived foods, further progress can be expected through the use of genomic or marker-assisted selection to increase the frequency of favourable genotypes and the formulation of diets to exploit this genetic potential.

Ruminant products are criticised for their SFA content relative to PUFA, although n-6:n-3 PUFA is desirable for human health ( < 4). Rumen protozoa are rich in unsaturated fatty acids due to engulfment of PUFA-rich chloroplasts. Increasing the chloroplast content of rumen protozoa offers a potentially novel approach to enhance PUFA flow to the duodenum and subsequent incorporation into meat and milk. We evaluated protozoal contribution to duodenal n-3 PUFA flow due to intracellular chloroplast content. A total of six Holstein × Friesian steers were fed, in a two-period changeover design, either straw:concentrate (S:C, 60:40; DM basis; S:C, low chloroplast) or fresh perennial ryegrass (PRG; high chloroplast). Following 12 d adaptation to diet, ruminal protozoal and whole duodenal samples were obtained. N and fatty acid content of whole duodenum and rumen protozoal samples were assessed and protozoal 18S rDNA quantitative PCR performed, enabling calculation of protozoal N flow. The ratio of individual fatty acids:N in rumen protozoal samples was calculated to obtain protozoal fatty acid flows. Based on total fatty acid flow, contribution (%) of protozoa to individual fatty acid flows was calculated. Protozoal fatty acid data and microscopical observations revealed that protozoa were enriched with 18 : 3n-3 following PRG feeding, compared with the S:C diet, due to increased intracellular chloroplast content. However, duodenal protozoal 18S rDNA concentration post PRG feeding was low, indicating rumen retention of the protozoa. Nutrition influences the 18 : 3n-3 content of protozoa; the challenge is to increase protozoal flow to the small intestine, while maintaining sustainable rumen densities.

Based on the potential benefits to human health, there is interest in developing sustainable nutritional strategies to enhance the concentration of long-chain n-3 fatty acids in ruminant-derived foods. Four Aberdeen Angus steers fitted with rumen and duodenal cannulae were used in a 4 × 4 Latin square experiment with 21 d experimental periods to examine the potential of fish oil (FO) in the diet to enhance the supply of 20 : 5n-3 and 22 : 6n-3 available for absorption in growing cattle. Treatments consisted of total mixed rations based on maize silage fed at a rate of 85 g DM/kg live weight0·75/d containing 0, 8, 16 and 24 g FO/kg diet DM. Supplements of FO reduced linearly (P < 0·01) DM intake and shifted (P < 0·01) rumen fermentation towards propionate at the expense of acetate and butyrate. FO in the diet enhanced linearly (P < 0·05) the flow of trans-16 : 1, trans-18 : 1, trans-18 : 2, 20 : 5n-3 and 22 : 6n-3, and decreased linearly (P < 0·05) 18 : 0 and 18 : 3n-3 at the duodenum. Increases in the flow of trans-18 : 1 were isomer dependent and were determined primarily by higher amounts of trans-11 reaching the duodenum. In conclusion, FO alters ruminal lipid metabolism of growing cattle in a dose-dependent manner consistent with an inhibition of ruminal biohydrogenation, and enhances the amount of long-chain n-3 fatty acids at the duodenum, but the increases are marginal due to extensive biohydrogenation in the rumen.

Nutrition has a major impact on the fatty acid composition of beef, despite high levels of biohydrogenation of dietary polyunsaturated fatty acids (PUFA) in the rumen (Scollan et al., 2006). The latter may be ameliorated by feeding rumen-protected lipid. Grass relative to concentrate feeding results in beef characterised by a higher content of n-3 PUFA and excellent colour shelf life. This study investigated the effects of including a PUFA-rich lucerne-based plant extract (PX) on the fatty acid composition and meat quality in beef.

The oxidative stability of meat depends upon a combination of pro-and antioxidants and the degree of unsaturation of its lipid classes. When animals graze grass the concentrations of α-tocopherol and β-carotene in meat and fat increase and decrease when they are fed concentrates. Supplementation with α-tocopherol acetate increased αtocopherol concentration in the meat of concentrate-fed animals, less so for grass-grazed animals (Descalzo et al., 2005; Realini et al., 2004). Less is known about the relationship between diet, antioxidant enzymes systems such as Superoxide dismutase (SOD) and Catalase (CAT), and the oxidative stability of meat. This study aimed to determine the influence of a forage versus a concentrate diet fed to beef cattle, and an additional treatment with a PUFA-rich lucerne-based plant extract (PX), on the antioxidant profile of their meat, and its relationship with lipid oxidation and colour shelf life. The addition of PX raised the unsaturated nature of the beef muscle lipids and thus increased the oxidative stress (Kim et al., 2009).

Ruminant production in the UK is largely dependent on grasslands: approximately 52% of UK land is (improved) grassland and rough grazing. Herbage production from improved grassland can be over five times higher than that of indigenous swards (Davies et al., 1984) and these pastures account for the majority of ruminant (meat and milk) production from grassland the UK. They are also amenable to manipulation through the choice of species, variety and mixture of forages sown. Efficiency of production can be influenced at the levels of both the plant and the animal and by the nutrition and genetics of both. This paper examines strategies to increase production efficiency based upon optimising rumen fermentation linked to plant breeding approaches. In this way efficiency can be improved without recourse to diet manipulation with supplements, which is generally impractical at grazing. Although the rumen microbial population allows the ruminant animal to extract energy from otherwise unusable sources (i.e. fibres), the rumen is also the source of greatest inefficiencies in the use of nitrogen and energy. Degraded plant nitrogen that is not captured by the rumen microbes tends to be absorbed as ammonia, much of which is excreted as urea and contributes to ammonia and nitrous oxide emissions. Similarly, methane release from the rumen represents a waste of energy that could otherwise be used for production. Globally, these two processes result in ruminant livestock accounting for approximately a third of the methane emissions (Beauchemin et al., 2008) and half of the nitrous oxide emissions (de Klein and Eckard, 2008) from anthropogenic sources.

Acetyl-CoA hydrolase which is stimulated by adenosine-5′-triphosphate is present in the cytoplasm of ovine liver and, unlike in certain others species, is not inactivated by cold. It is suggested that this enzyme is involved in a substrate cycle between acetate and acetyl-CoA. The heat produced as a result of such cycling may be as much as 2·5% of basal heat production and may be partly responsible for the increased heat increment that often follows the ingestion of diets that provide large quantities of acetate.

Sixteen Blackface wether lambs (25–27 kg) were fed for 9 weeks on diets based on either barley (B) or sugarbeet pulp (S), with either a low or high protein content. A constant amount of metabolizable energy (ME) was given at twice maintenance level. At one stage the animals were fed frequently and blood was sampled over a 24 h period. Plasma was assayed for acetate, glucose and insulin. After slaughter, the metabolism of acetate to CO2 and lipid was investigated in perirenal adipocytes in vitro.

Frequent feeding helped to achieve near-steady-state conditions. Carbohydrate source influenced plasma acetate (P < 0·08) but not glucose or insulin. Level of protein in the diet influenced plasma acetate, higher concentrations of acetate were associated with lower levels of protein (P < 0·01). Acetate oxidation and incorporation into lipid was influenced by the concentrations of acetate, glucose and insulin in the incubation media (P < 0·001). Acetate oxidation was influenced by carbohydrate source (P < 0·05), whereas level of protein in the diet affected acetate incorporation into lipid (P < 0·05).

These results show how the balance of nutrients provided to a ruminant for metabolism may influence selected plasma parameters and the metabolism of acetate by adipose tissue, which may help to explain the reduced efficiency of ME utilization from more fibrous diets.

Red clover and fish oil (FO) are known to alter ruminal lipid biohydrogenation leading to an increase in the polyunsaturated fatty acid (PUFA) and conjugated linoleic acid (CLA) content of ruminant-derived foods, respectively. The potential to exploit these beneficial effects were examined using eight Hereford × Friesian steers fitted with rumen and duodenal cannulae. Treatments consisted of grass silage or red clover silage fed at 90% of ad libitum intake and FO supplementation at 0, 10, 20 or 30 g/kg diet dry matter (DM). The experiment was conducted with two animals per FO level and treatments formed extra-period Latin squares. Flows of fatty acids at the duodenum were assessed using ytterbium acetate and chromium ethylene diamine tetra-acetic acid as indigestible markers. Intakes of DM were higher (P < 0.001) for red clover silage than grass silage (5.98 v. 5.09 kg/day). There was a linear interaction effect (P = 0.004) to FO with a reduction in DM intake in steers fed red clover silage supplemented with 30 g FO/kg diet DM. Apparent ruminal biohydrogenation of C18:2n-6 and C18:3n-3 were lower (P < 0.001) for red clover silage than grass silage (0.83 and 0.79 v. 0.87 and 0.87, respectively), whilst FO increased the extent of biohydrogenation on both diets. Ruminal biohydrogenation of C20:5n-3 and C22:6n-3 was extensive on both silage diets, averaging 0.94 and 0.97, respectively. Inclusion of FO in the diet enhanced the flow of total CLA leaving the rumen with an average across silages of 0.22, 0.31, 0.41 and 0.44 g/day for 0, 10, 20 or 30 g FO/kg, respectively, with a linear interaction effect between the two silages (P = 0.03). FO also showed a dose-dependent increase in the flow of trans-C18:1 intermediates at the duodenum from 4.6 to 15.0 g/day on grass silage and from 9.4 to 22.5 g/day for red clover silage. Concentrations of trans-C18:1 with double bonds from Δ4–16 in duodenal digesta were all elevated in response to FO in both diets, with trans-11 being the predominant isomer. FO inhibited the complete biohydrogenation of dietary PUFA on both diets, whilst red clover increased the flow of C18:2n-6 and C18:3n-3 compared with grass silage. In conclusion, supplementing red clover silage-based diets with FO represents a novel nutritional strategy for enhancing the concentrations of beneficial fatty acids in ruminant milk and meat.

Microbial transformations in the rumen ecosystem have a major impact on our ability to meet the challenge of reducing the environmental footprint of ruminant livestock agriculture, as well as enhancing product quality. Current understanding of the rumen microbial ecosystem is limited, and affects our ability to manipulate rumen output. The view of ruminal fermentation as the sum of activities of the dominant rumen microbiota is no longer adequate, with a more holistic approach required. This paper reviews rumen functionality in the context of the microbiota of the rumen ecosystem, addressing ruminal fermentation as the product of an ecosystem while highlighting the consequences of this for ruminant agriculture. Microbial diversity in the rumen ecosystem enhances the resistance of the network of metabolic pathways present, as well as increasing the potential number of new pathways available. The resulting stability of rumen function is further promoted by the existence of rumen microbiota within biofilms. These protected, structured communities offer potential advantages, but very little is currently known about how ruminal microorganisms interact on feed-surfaces and how these communities develop. The temporal and spatial development of biofilms is strongly linked to the availability of dietary nutrients, the dynamics of which must also be given consideration, particularly in fresh-forage-based production systems. Nutrient dynamics, however, impact not only on pathway inputs but also the turnover and output of the whole ecosystem. Knowledge of the optimal balance of metabolic processes and the corresponding microbial taxa required to provide a stable, balanced ecosystem will enable a more holistic understanding of the rumen. Future studies should aim to identify key ecosystem processes and components within the rumen, including microbial taxa, metabolites and plant-based traits amenable to breeding-based modification. As well as gaining valuable insights into the biology of the rumen ecosystem, this will deliver realistic and appropriate novel targets for beneficial manipulation of rumen function.

Rapid breakdown of herbage proteins in the rumen and inefficient capture of nitrogen (N) by the rumen microbial populations are a major source of N loss and pollution in pasture-based ruminant agriculture. Degree of cell damage during mastication and ingestion varies between grass species with consequences for release of cell contents (protein, sugars and lipids) into the rumen (Kim et al., 2008). Consequently, grazing cattle on different grass species may provide an opportunity to manipulate N efficiency. The purpose of this study was to compare N utilisation efficiency by dairy cattle grazing grass species differing in chemical and morphological characteristics.

It is the practise for some farmers to supplement new season lambs with concentrates, often as a creep feed, in order to get them to market early before the price declines. This concentrate is usually based on cereals and would be high in n-6 fatty acids, diluting the beneficial effect of grass grazing which promotes the n-3 polyunsaturated fatty acid (PUFA) content in the meat (Fisher et al., 2000). The purpose of this trial was to assess the addition of linseed to the concentrate, fed in a creep-feed system, which would maintain or enhance the n-3 fatty acid composition of the meat of animals fed concentrates at grass during the finishing period (Cooper et al., 2004).

As grazing ruminants rely almost entirely on mastication to disrupt plant tissues, a series of processes (mastication, bolus formation and ingestion) will impact on the viability and number of cells that remain intact, and consequently alive, after ingestion (Kingston-Smith and Theodorou, 2000). Preliminary work in our group has shown substantial variation in the degree of cell damage during mastication and ingestion between grass species, resulting in differences in the rate of release of cell contents (protein, sugars and lipids) into the rumen (E.J. Kim, unpublished). These differences may affect nutrient utilisation by ruminal micro-organisms. The aim of this study was to compare the extent of nutrient release from three contrasting grass species following ingestion of the fresh forage by dairy cows.

Previous studies have shown that including fish oil (FO) in the diet of beef cattle resulted in increased long chain C20n-3 PUFA (C20:5n-3 and C22:6n-3) in muscle resulting in a lower n-6:n-3 ratio (Scollan et al., 2005). Fish oil is considered to be a good inhibitor of biohydrogenation in the rumen, resulting in increased production of C18:1 trans-11 (Vaccenic acid), the precursor for conjugated linoleic acid (CLA cis-9, trans-11) in muscle. This study investigated the effects of incremental levels of FO in the diet on fatty acid metabolism in the rumen.

The declining consumption of ruminant products has been partly associated with their high proportion (but not necessarily content) of saturated fatty acids. Recent studies have focused on the less prominent fact that they are also important sources of beneficial fatty acids, including n-3 fatty acids and conjugated linoleic acids. α-Linolenic acid (18: 3n-3) is of particular interest because it also contributes to improved flavour of beef and lamb. Many recent studies showed large effects of special concentrates on levels of fatty acids in milk and meat. However, the ‘rumen protection’ treatments, needed to ensure a worthwhile level of fatty acid in products, are expensive. Herbage lipids are the cheapest and safest source of these fatty acids and so breeding to increase delivery of fatty acids from plants into ruminant products is an important long-term strategy. Plant lipids usually contain high levels of polyunsaturated fatty acids, particularly 18: 2n-6 and 18:3n-3 which are the precursors of beneficial fatty acids. Whilst some plants are particularly rich in individual fatty acids (e.g. 18:3n-3 in linseed), there are also useful levels in grass and clover (Trifolium Spp.). Levels of fatty acids in forages in relation to species and varieties are considered, as well as management and conservation methods. Relationships between levels of fatty acids and existing traits and genetic markers are identified. The effects of forage treatments on the fatty acid content of ruminant products are reviewed. The higher levels of polyunsaturated fatty acids in milk from cows fed clover silages show that the level of fatty acids in herbage is not the only factor affecting levels of fatty acids in ruminant products. Further effort is needed to characterise susceptibility of unsaturated fatty acids to oxidative loss during field wilting and biohydrogenation losses in the rumen, and the relative importance of plant and microbial processes in these losses. The pathways of lipolysis and lipid oxidation are reviewed and other plant factors which offer potential to breed for reduced losses are considered.

The effects of the type of grass silage and dietary inclusion of fish oil (FO) on the fatty acid profile of bovine intramuscular and subcutaneous adipose tissue were investigated. Eighty Friesian steers were assigned (n 10) to unwilted or wilted silage, and to one of four rations which contained, per kg, 80 g of sunflower oil and either 0, 10, 20 or 40 g of FO replacing lard. Animals were slaughtered after 108 d and the fatty acid profile of the neutral, polar and total lipid fractions of the M. longissimus dorsi, and the total lipid fraction of the subcutaneous adipose tissue were determined. Wilting of grass prior to ensiling increased the concentration of conjugated linoleic acid (CLA) in intramuscular total lipid (P < 0·01), but did not affect the n-6:n-3 PUFA ratio. Increasing FO supply linearly increased (P < 0·05) the concentration of the cis-9, trans-11 and trans-10, cis-12 isomers of CLA and trans-11 18 : 1 predominantly in the neutral lipid fraction of intramuscular total lipid, and linearly decreased the n-6:n-3 PUFA ratio. Wilting of grass prior to ensiling increased the concentration of CLA in subcutaneous adipose tissue (P < 0·001), while increasing FO supply linearly increased the concentration of cis-9, trans-11 CLA. From a human nutrition perspective, increasing the level of FO in the ration or wilting of grass prior to ensiling appear to modify the fatty acid composition of beef muscle favourably. However, the health implications of associated increases in trans fatty acids remain to be elucidated.

Legumes are important constituents of ruminant diets and are a vital part of low input and organic systems. Previous studies have established the high intake characteristics and animal production potential of red clover silage. Studies with milk produced from cows fed on red clover silage was noted to have higher levels of polyunsaturated fatty acids (PUFA) but had a reduced shelf life which could be ameliorated by feeding additional vitamin E (Al-Mabruk et al., 2004). This study considered the effects of incremental inclusion of red clover silage in the diet of beef cattle on the fatty acid composition of the m. longissimus dorsi and meat quality.

Previous work has shown that the biohydrogenation of fatty acids is different in solid and liquid fractions prepared from rumen fluid (Dorel et al. , 2005). This study aimed to relate this observation to differences in the microbial population in the different fractions. Molecular techniques allow the rapid investigation of microbial numbers and diversity in environmental samples. However, description of the microbial diversity can be affected by the efficiency of DNA extraction from samples as it is known that it is harder to quantitatively extract DNA from some microbes than others (Clement and Kitts, 2000). The aim of this study was to investigate different protocols for preparing samples and extracting DNA from different fractions of rumen fluid, in terms of both the numbers and diversity of bacteria that could be recovered.