Nutritional value of suckler beef from temperate pasture systems.

The role of beef in human diets has been questioned over the last few decades, due largely to its typically high mass-based carbon footprint. However, recent advancements in sustainability literature challenge this paradigm based on the new theory that climate impacts of food commodities should be measured relative to their overall nutritional value rather than their nominal mass. This shift has opened a new opportunity for the global beef industry, and especially for pasture-based systems that can avoid food-feed competition for land and other resources, as beef is a nutritionally dense food. Nonetheless, the sector's true capability to supply a wide range of nutrients for humans, consistently across multiple systems under multiple weather patterns, has not been well-documented. Using whole-system datasets from the North Wyke Farm Platform in the South West of England, we investigated the nutritional value of beef produced from the three most common pasture systems in temperate regions: permanent pasture (PP), grass and white clover (GWC) and a short-term monoculture grass ley (MG). Beef produced from these three pasture systems was analysed for key nutrients (fatty acids, minerals and vitamin E) over three production cycles (2015-2017) to determine potential differences between systems. Fatty acid, mineral and vitamin E profiles of the pasture and silage fed to each group were also assessed, with subtle differences between pastures reported. For beef, subtle differences were also observed between systems, with GWC having higher omega-6 polyunsaturated fatty acid (PUFA) concentrations than PP and MG. However, the overall nutritional quality of beef was found to be largely comparable across all systems, suggesting that temperate pasture-based beef can be classified as a single commodity in future sustainability assessments, regardless of specific sward types. A 100 g serving of temperate pasture-based beef was found to be a high source (>20% recommended daily intake: RDI) of protein, monounsaturated fatty acids, saturated fatty acids, vitamins - B2, B3, B12 and minerals - Fe, P, Zn; a good source (10-19% RDI) of vitamin - B6 and mineral - K; and a complementary source (5-9% RDI) of omega-3 PUFA, vitamin - B9 and minerals - Cu, Mg, Se. The nutritional value of a food item should be used in defining its environmental cost (e.g. carbon footprint) to make fair comparisons across different food groups (e.g. protein sources). Here, we showed that pasture-based beef had a nutrient indexed carbon footprint of between 0.19 and 0.23 Kg CO2-eq/1% RDI of key nutrients.

Nitrogen and fatty acid rumen metabolism in cattle offered high or low polyphenol oxidase red clover silage.

Polyphenol oxidase (PPO) in red clover (RC) has been shown to reduce both lipolysis and proteolysis in silo and implicated (in vitro) in the rumen. However, all in vivo comparisons have compared RC with other forages, typically with lower levels of PPO, which brings in other confounding factors as to the cause for the greater protection of dietary nitrogen (N) and C18 polyunsaturated fatty acids (PUFA) on RC silage. This study compared two RC silages which when ensiled had contrasting PPO activities (RC+ and RC-) against a control of perennial ryegrass silage (PRG) to ascertain the effect of PPO activity on dietary N digestibility and PUFA biohydrogenation. Two studies were performed the first to investigate rumen and duodenal flow with six Hereford×Friesian steers, prepared with rumen and duodenal cannulae, and the second investigating whole tract N balance using six Holstein-Friesian non-lactating dairy cows. All diets were offered at a restricted level based on animal live weight with each experiment consisting of two 3×3 Latin squares using big bale silages ensiled in 2010 and 2011, respectively. For the first experiment digesta flow at the duodenum was estimated using a dual-phase marker system with ytterbium acetate and chromium ethylenediaminetetraacetic acid as particulate and liquid phase markers, respectively. Total N intake was higher on the RC silages in both experiments and higher on RC- than RC+. Rumen ammonia-N reflected intake with ammonia-N per unit of N intake lower on RC+ than RC-. Microbial N duodenal flow was comparable across all silage diets with non-microbial N higher on RC than the PRG with no difference between RC+ and RC-, even when reported on a N intake basis. C18 PUFA biohydrogenation was lower on RC silage diets than PRG but with no difference between RC+ and RC-. The N balance trial showed a greater retention of N on RC+ over RC-; however, this response is likely related to the difference in N intake over any PPO driven protection. The lack of difference between RC silages, despite contrasting levels of PPO, may reflect a similar level of protein-bound-phenol complexing determined in each RC silage. Previously this complexing has been associated with PPOs protection mechanism; however, this study has shown that protection is not related to total PPO activity.

The effect of high polyphenol oxidase grass silage on metabolism of polyunsaturated fatty acids and nitrogen across the rumen of beef steers.

Polyphenol oxidase (PPO) activity in red clover (Trifolium pratense) has been reported to reduce both proteolysis and lipolysis, resulting in greater N use efficiency and protection of PUFA across the rumen. Although high levels of PPO have been reported in grasses such as cocksfoot (orchard grass; Dactylis glomerata), no in vivo research has determined whether grass PPO elicits the same response as red clover PPO. To test the hypothesis that silage ensiled from grass with high levels of PPO protects N and PUFA across the rumen, 6 steers with ruminal and duodenal cannulas were offered cocksfoot silage (CO; high-PPO grass), perennial ryegrass silage (PR; Lolium perenne; low-PPO grass), or red clover silage (RC; high-PPO control) at 16 g DM/kg BW daily with the experiment consisting of two 3 × 3 Latin squares with 21-d periods, consisting of 12 d of diet adaptation, 6 d of duodenal marker infusion, 2 d of duodenal sampling, and 1 d of ruminal sampling. All silages were well preserved, with DM of 34.4, 55.3, and 45.4% for CO, PR, and RC. Activity of PPO in silages was low due to deactivation but was greater in CO than either PR or RC (0.15 vs. 0.05 and 0.08 µkatal/g DM). Protein-bound phenol (mg/g DM) as a measure of the degree of oxidation and an indication of PPO protection was greatest for RC (15.9) but comparable for PR (10.1) and CO (12.2). Biohydrogenation of C18 PUFA was significantly lower on RC compared to the 2 grass silages with CO greater than PR. Despite lower levels of total fatty acid intake and subsequent duodenal flow, CO resulted in greater levels of phytanic acid and total branched and odd chain fatty acids in duodenal digesta than RC or PR. Ruminal ammonia concentration was greatest for RC, with no difference between the grasses. Duodenal flow of microbial N and efficiency of microbial protein synthesis were lowest for CO and comparable for RC and PR. The CO (high-grass PPO) did not result in elevated levels of C18 PUFA escaping the rumen or improve efficiency of total N transfer through the rumen compared to PR. The RC resulted in a greater flow of N and nonmicrobial N to the duodenum than the 2 grasses with PR greater than CO.

Fatty acid oxidation products ('green odour') released from perennial ryegrass following biotic and abiotic stress, potentially have antimicrobial properties against the rumen microbiota resulting in decreased biohydrogenation.

AIMS: In this experiment, we investigated the effect of 'green odour' products typical of those released from fresh forage postabiotic and biotic stresses on the rumen microbiota and lipid metabolism. METHODS AND RESULTS: Hydroperoxyoctadecatrienoic acid (HP), a combination of salicylic and jasmonic acid (T), and a combination of both (HPT) were incubated in vitro in the presence of freeze-dried ground silage and rumen fluid, under rumen-like conditions. 16S rRNA (16S cDNA) HaeIII-based terminal restriction fragment length polymorphism-based (T-RFLP) dendrograms, canonical analysis of principal coordinates graphs, peak number and Shanon-Weiner diversity indices show that HP, T and HPT likely had antimicrobial effects on the microbiota compared to control incubations. Following 6 h of in vitro incubation, 15.3% of 18:3n-3 and 4.4% of 18:2n-6 was biohydrogenated in control incubations, compared with 1.3, 9.4 and 8.3% of 18:3n-3 for HP, T and HPT treatments, respectively, with negligible 18:2n-6 biohydrogenation seen. T-RFLP peaks lost due to application of HP, T and HPT likely belonged to as yet uncultured bacteria within numerous genera. CONCLUSIONS: Hydroperoxyoctadecatrienoic acid, T and HPT released due to plant stress potentially have an antimicrobial effect on the rumen microbiota, which may explain the decreased biohydrogenation in vitro. SIGNIFICANCE AND IMPACT OF THE STUDY: These data suggest that these volatile chemicals may be responsible for the higher summer n-3 content of bovine milk.

Beef, chicken and lamb fatty acid analysis--a simplified direct bimethylation procedure using freeze-dried material.

When fractionation of meat lipids is not required, procedures such as saponification can be used to extract total fatty acids, reducing reliance on toxic organic compounds. However, saponification of muscle fatty acids is laborious, and requires extended heating times, and a second methylation step to convert the extracted fatty acids to fatty acid methyl esters prior to gas chromatography. Therefore the development of a more rapid direct methylation procedure would be of merit. The use of freeze-dried material for analysis is common and allows for greater homogenisation of the sample. The present study investigated the potential of using freeze-dried muscle samples and a direct bimethylation to analyse total fatty acids of meat (beef, chicken and lamb) in comparison with a saponification procedure followed by bimethylation. Both methods compared favourably for all major fatty acids measured. There was a minor difference in relation to the C18:1 trans 10 isomer with a greater (P<0.05) recovery with saponification. However, numerically the difference was small and likely as a result of approaching the limits of isomer identification by single column gas chromatography. Differences (P<0.001) between species were found for all fatty acids measured with no interaction effects. The described technique offers a simplified, quick and reliable alternative to saponification to analyse total fatty acids from muscle samples.

Ruminal protozoal contribution to the duodenal flow of fatty acids following feeding of steers on forages differing in chloroplast content.

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.

Effect of feeding fresh or conditioned red clover on milk fatty acids and nitrogen utilization in lactating dairy cows.

Polyphenol oxidase (PPO) in conditioned red clover (ensiled or cut and crushed) reduces both proteolysis and lipolysis in the herbage, which has led to increases in N use efficiency and polyunsaturated fatty acid (PUFA) content of milk when offered to dairy cows. In damaged plant cells, PPO is activated and binds protein through the formation of protein-bound phenols. This study investigated a) whether freshly cut red clover could increase N use efficiency and milk PUFA concentrations in dairy cows or whether PPO enzymes require prior activation before feeding to elicit a response, and b) apparent whole-tract amino acid digestibility to help determine the effect of PPO on amino acid utilization. Six multiparous Holstein x Friesian dairy cows in mid-lactation were allocated at random to 1 of 3 dietary treatments in a 3 x 3 Latin square: a control treatment of grass (low PPO, G); red clover (high PPO, RC), and conditioned red clover (high fully activated PPO, CRC). The CRC herbage was cut and chopped in the field and then transported with the G and RC herbages to the animal house. Each period consisted of a 2-wk adaptation to diet and a week of measuring dietary effects (N balance and milk collection). The PPO activity was greatest in the RC treatment as fed, whereas activation of latent PPO enzyme and protein-bound phenol levels were greatest in the CRC diet. Dry matter and total fatty acid intakes were comparable across treatments (18.8 kg/d and 550 g/d, respectively). Milk yields and total fatty acid content were similar across treatments (32.6 kg/d and 34.8 mg/mL, respectively). Cows offered either RC or CRC had greater levels of protein, C18 PUFA and total long-chain PUFA in their milk than animals offered grass with no difference between RC and CRC. Nitrogen intakes, and output in milk, urine, and feces were greater in cows offered the 2 red clover treatments than G, with no difference between RC and CRC. However, there were no differences in N use efficiency among diets as measured by the proportion of feed N converted into milk N, possibly as the result of the excessive supply of N with the red clover diets. Amino acid apparent whole-tract digestibilities were greater when on RC than G diets and intermediate when on CRC for all amino acids, with the exception of Met, which was reduced in cows on both red clover diets compared with G. It is proposed that the PPO trait could show more benefit to ruminants if red clover was fed in combination with lesser N-containing forages or if red clover was bred to contain less N.

Effect of fish oil on ruminal biohydrogenation of C18 unsaturated fatty acids in steers fed grass or red clover silages.

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.

Effects of high-sugar ryegrass silage and mixtures with red clover silage on ruminant digestion. 2. Lipids.

The experiment investigated the digestion of lipids from different forage silages in beef steers. Six Hereford x Friesian steers prepared with rumen and duodenal cannulas were given ad libitum access to a high-sugar grass silage, control grass silage, red clover silage, or mixtures of the red clover and each of the grass silages (50:50, DM basis). The experiment was conducted as an incomplete 5 x 5 Latin square, with an additional randomly repeated sequence. Total fatty acid and C18:3n-3 concentrations were greater (P < 0.05) for the high-sugar grass silage than the control grass silage or the red clover silage. Dry matter and total fatty acid intake were less (P < 0.05) for steers fed the control grass silage than for steers fed the other diets. Duodenal flow of C18:3n-3 was greater (P < 0.05), and flows of C18:0 and total C18:1 trans were less (P < 0.05), for the red clover silage compared with the 2 grass silage diets, with the mixtures intermediate. These results were supported by a reduction (P < 0.05) in biohydrogenation of C18:3n-3 for the red clover silage, with the mixtures again being intermediate. Flows of total branched- and odd-chain fatty acids were greater (P < 0.05) for the high-sugar grass silage diet, possibly as a result of greater microbial flow, because these fatty acids are associated with bacterial lipid. Duodenal flows of the chlorophyll metabolite, phytanic acid, were greater (P < 0.05) for animals fed the high-sugar grass silage treatments compared with the other treatments. These results confirm the potential for modifying the fatty acid composition of ruminant products by feeding red clover silage.

Comparison of grass and legume silages for milk production. 1. Production responses with different levels of concentrate.

Silages prepared from pure stands of ryegrass, alfalfa, white clover, and red clover over two successive year were offered to lactating dairy cows in two feeding experiments. Proportional mixtures of all cuts prepared in a yr were used to ensure that the forage treatments were representative of the crop. Additional treatments involved mixtures of grass silage with either white clover silage or red clover silage (50/50, on a DM basis). Silages were prepared in round bales, using a biological inoculant additive, and wilting for up to 48 h. Although the legumes were less suited to silage-making than grass, because of their higher buffering capacity and lower water-soluble carbohydrate content, all silages were well-fermented. A standard concentrate was offered at a flat-rate (8 kg/d in yr 1, and 4 or 8 kg/d in yr 2). All of the legume silages led to higher DM intake and milk yields than for the grass silage, with little effect on milk composition. Intake and production responses to legumes were similar at the two levels of concentrate feeding and with forage mixtures they were intermediate to those for the separate forages. An additional benefit of the clover silages, particularly red clover silage, was the increase in levels of polyunsaturated fatty acids, particularly alpha-linolenic acid, in milk. Legume silages also led to a lower palmitic acid percentage in milk. The efficiency of conversion of feed N into milk N declined with increasing levels of legume silage. White clover silage led to a higher N-use efficiency when the effect of N intake level is taken into account.