Red clover polyphenol oxidase and lipid metabolism

Feeding lower-protein diets based on red clover and grass or alfalfa and corn silage does not affect milk production but improves nitrogen use efficiency in dairy cows

Reducing the dietary crude protein (CP) concentration can decrease the financial cost and lower the environmental impact of milk production. Two studies were conducted to examine the effects of reducing the dietary CP concentration on animal performance, nutrient digestibility, milk fatty acid (FA) profile, and nitrogen use efficiency (NUE; milk N/N intake) in dairy cows fed legume silage-based diets. Thirty-six multiparous Holstein-Friesian dairy cows that were 76 ± 14 (mean ± SD) days in milk and 698 ± 54 kg body weight were used in a 3 × 3 Latin square design in each of 2 studies, with 3 periods of 28 d. In study 1, cows were fed diets based on a 50:50 ratio of red clover to grass silage [dry matter (DM) basis] containing 1 of 3 dietary CP concentrations: high (H) = 175 g of CP/kg of DM; medium (M) = 165 g of CP/kg of DM; or low (L) = 150 g of CP/kg of DM. In study 2, cows were fed 175 g of CP/kg of DM with a 50:50 ratio of alfalfa to corn silage (H50) or 1 of 2 diets containing 150 g of CP/kg of DM with either a 50:50 (L50) or a 60:40 (L60) ratio of alfalfa to corn silage. Cows in both studies were fed a total mixed ration with a forage-to-concentrate ratio of 52:48 (DM basis). All diets were formulated to meet the MP requirements, except L (95% of MP requirements). In study 1, cows fed L ate 1.6 kg of DM/d less than those fed H or M, but milk yield was similar across treatments. Mean milk protein, fat, and lactose concentrations were not affected by diet. However, the apparent total-tract nutrient digestibility was decreased in cows fed L. The NUE was 5.7 percentage units higher in cows fed L than H. Feeding L also decreased milk and plasma urea concentrations by 4.4 mg/dL and 0.78 mmol/L, respectively. We found no effect of dietary treatment on the milk saturated or monounsaturated FA proportion, but the proportion of polyunsaturated FA was increased, and milk odd- and branched-chain FA decreased in cows fed L compared with H. In study 2, DM intake was 2 kg/d lower in cows receiving L50 than H50. Increasing the alfalfa content and feeding a low-CP diet (L60) did not alter DMI but decreased milk yield and milk protein concentration by 2 kg/d and 0.6 g/kg, respectively, compared with H50. Likewise, milk protein and lactose yield were decreased by 0.08 kg/d in cows receiving L60 versus H50. Diet had no effect on apparent nutrient digestibility. Feeding the low-CP diets compared with H50 increased the apparent NUE by approximately 5 percentage units and decreased milk and plasma urea concentrations by 7.2 mg/dL and 1.43 mmol/L, respectively. Dietary treatment did not alter milk FA profile except cis-9,trans-11 conjugated linoleic acid, which was higher in milk from cows receiving L60 compared with H50. We concluded that reducing CP concentration to around 150 g/kg of DM in red clover and grass or alfalfa and corn silage-based diets increases the apparent NUE and has little effect on nutrient digestibility or milk performance in dairy cows.

Milk from cows fed clover-rich silage compared with cows fed grass silage is higher in n-3 fatty acids

The present study investigated the effect of a high proportion of different forage species in the diet, parity, milking time, and days in milk (DIM) on milk fatty acid (FA) profile, and transfer efficiency of C18:2n-6, C18:3n-3, n-6, and n-3 in dairy cows. Swards with perennial ryegrass [early maturity stage (EPR) and late maturity stage (LPR)], festulolium, tall fescue (TF), red clover (RC), and white clover (WC) were cut in the primary growth, wilted, and ensiled without additives. Thirty-six Danish Holstein cows in an incomplete Latin square design were fed ad libitum with total mixed rations containing a high forage proportion (70% on dry matter basis). The total mixed rations differed only in forage source, which was either 1 of the 6 pure silages or a mixture of LPR silage with either RC or WC silage (50:50 on dry matter basis). Proportion of C18:2n-6 in milk FA was affected by diet, and RC and WC diets resulted in the highest proportion of C18:2n-6 in milk FA (21.6 and 21.8 g/kg of FA, respectively). The highest and lowest milk C18:3n-3 proportion was observed in WC and LPR, respectively. In addition, WC diet resulted in highest transfer efficiency of C18:3n-3 from feed to milk (12.2%) followed by RC diet (10.7%), whereas EPR diet resulted in the lowest transfer efficiency of C18:3n-3 (3.45%). The highest milk proportion of cis-9,trans-11 conjugated linoleic acid (CLA) was observed in cows fed TF (3.20 g/kg of FA), which was 23 to 64% higher than the proportion observed in the cows fed the other diets. The highest α-tocopherol concentration (µg/mL) in milk was observed in EPR (1.15), LPR (1.10), and festulolium (1.06). Primiparous cows showed higher proportion of cis-9,trans-11 CLA (2.63 g/kg of FA) than multiparous cows (2.21 g/kg of FA). Cows early in lactation had a higher proportion of long-chain FA in milk than cows later in lactation, as long-chain FA decreased with 0.184 g/kg of FA per DIM, whereas medium-chain FA increased with 0.181 g/kg of FA per DIM. Proportion of C18:2n-6 in milk from evening milking was higher than in milk from morning milking (16.7 vs. 15.8 g/kg of FA). In conclusion, the results showed that milk FA profile of cows was affected by forage source in the diet, and RC and WC increased the health-promoting FA components, particularly n-3, whereas the TF diet increased proportion of CLA isomers in milk. Proportion of CLA isomers in milk FA from primiparous cows was higher than in milk from multiparous cows. In addition, evening milk contained more FA originating from diets compared with morning milk.

Prospects for Trifolium Improvement Through Germplasm Characterisation and Pre-breeding in New Zealand and Beyond

Trifolium is the most used pastoral legume genus in temperate grassland systems, and a common feature in meadows and open space areas in cities and parks. Breeding of Trifolium spp. for pastoral production has been going on for over a century. However, the breeding targets have changed over the decades in response to different environmental and production pressures. Relatively small gains have been made in Trifolium breeding progress. Trifolium breeding programmes aim to maintain a broad genetic base to maximise variation. New Zealand is a global hub in Trifolium breeding, utilising exotic germplasm imported by the Margot Forde Germplasm Centre. This article describes the history of Trifolium breeding in New Zealand as well as the role and past successes of utilising genebanks in forage breeding. The impact of germplasm characterisation and evaluation in breeding programmes is also discussed. The history and challenges of Trifolium breeding and its effect on genetic gain can be used to inform future pre-breeding decisions in this genus, as well as being a model for other forage legumes.

Comparison of nitrogen transformation dynamics in non-irradiated and irradiated alfalfa and red clover during ensiling

Objective

To study the contribution of plant enzyme and microbial activities on protein degradation in silage, this study evaluated the nitrogen transformation dynamics during ensiling of non- and irradiated alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.).

Methods

Alfalfa and red clover silages were prepared and equally divided into two groups. One group was exposed to γ-irradiation at a recommended dosage (25 Gky). Therefore, four types of silages were produced: i) non-irradiated alfalfa silage; ii) irradiated alfalfa silage; iii) non-irradiated red clover silage; and iv) irradiated red clover silage. These silages were opened for fermentation quality and nitrogen components analyses after 1, 4, 8, and 30 days, respectively.

Results

The γ-irradiation successfully suppressed microbial activity, indicated by high pH and no apparent increases in fermentation end products in irradiated silages. All nitrogen components, except for peptide-N, increased throughout the ensiling process. Proteolysis less occurred in red clover silages compared with alfalfa silages, indicated by smaller (p<0.05) increment in peptide-N and free amino acid N (FAA-N) during early stage of ensiling. The γ-irradiation treatment increased (p<0.05) peptide-N and FAA-N in alfalfa silage at day 1, whereas not in red clover silage; these two nitrogen components were higher (p<0.05) between day 4 and day 30 in non-irradiated silages than the irradiated silages. The ammonia nitrogen and non-protein nitrogen were highest in non-irradiated alfalfa silage and lowest in irradiated red clover silage after ensiling.

Conclusion

The result of this study indicate that red clover and alfalfa are two forages varying in their nitrogen transformation patterns, especially during early stages of ensiling. Microbial activity plays a certain role in the proteolysis and seems little affected by the presence of polyphenol oxidase in red clover compared with alfalfaa.

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.

Red clover silage improves milk fatty acid composition in dairy ewes

The purpose of this study was to evaluate the effects of two isoproteic total mixed rations containing either red clover (Trifolium pratense L.; RC diet) or lucerne (Medicago sativa L.; LU diet) silage as the major forage source on milk yield, milk composition, and milk fatty acid (FA) profile in dairy ewes. Sixteen dairy ewes were housed individually to receive the drawn diet (eight ewes eating each diet) and milked twice a day (0700 and 1500). Total dry matter intake, milk yield, milk composition, and nitrogen use efficiency were unaffected by treatments. The n-6/n-3 FA ratio tended to decrease, whereas the total polyunsaturated fatty acids (PUFAs) and PUFAs/saturated fatty acids ratio increased in the milk fat of ewes fed the RC diet compared with ewes fed the LU diet. The presence of α-linolenic (C18:3n-3) and linoleic (C18:2n-6) acids in the milk fat was 22% higher in ewes fed the RC diet than in those fed the LU diet. Compared with the LU diet, the RC diet had no effect on milk yield and composition, but improved the milk FA profile in dairy ewes due to an increased proportion of PUFAs (in particular C18:3n-3 and, to a lesser extent, C18:2n-6) and a decreased n-6/n-3 FA ratio.

Predicting duodenal flows and absorption of fatty acids from dietary characteristics in ovine and bovine species: a meta-analysis approach

Dietary and ruminal factors modify the ruminal biohydrogenation (RBH) of polyunsaturated fatty acids (FA), with duodenal FA flows being quantitatively and qualitatively different from FA intake. Using a meta-analysis approach from a database on duodenal flows of FA in ruminants, this study aimed to determine predictive equations for duodenal and absorbed flows of saturated FA, C18:1, C18:2 and C18:3 isomers, odd- and branched-chain FA (OBCFA), C20:5n-3, C22:5n-3 and C22:6n-3 and to quantify the effects of dietary and digestive factors on those equations. The database was divided into four subsets: forage, seed, vegetable oils or animal fats (oil/fat), and fish products (fish) subsets. Models of duodenal and absorbed FA flows were obtained through variance-covariance analysis. Effects of potential interfering factors (conservation mode and botanical families of forages, lipid source, technological processing of lipid supplements, diet composition and animal characteristics) were analysed. We obtained 83 models for duodenal FA flows as a function of FA intake for saturated FA (C14:0, C16:0 and C18:0), C18:1, C18:2 and C18:3 isomers and seven other models for OBCFA. For the seed/oil/fat subset, intakes of total C18:3, C18:2 and starch content increased the duodenal t11-C18:1 flow with 0.08, 0.16 and 0.005 g/kg of dry matter intake (DMI), respectively, whereas intake level [(DMI×100)/BW] decreased it. The c9c12c15-C18:3 RBH was higher for oil/fat than seed (96.7% v. 94.8%) and a protective effect of Leguminosae v. Gramineae against RBH for that FA appeared in the forage subset. The duodenal C17:0 flow increased with starch content and decreased with ruminal pH, respectively, whereas duodenal iso-C16:0 flow decreased with dietary NDF content for the seed/oil/fat subset. The duodenal C20:5n-3, C22:5n-3 and C22:6n-3 flows depended on their respective intake and the inhibitory effect of C22:6n-3 on duodenal C18:0 flow was quantified. Thirteen models of absorbed FA flows were performed depending on their respective duodenal flows. This study determined the effects of different qualitative and quantitative dietary and digestive factors, allowing for improved predictions of duodenal and absorbed FA flows.

Fatty acid composition of ruminal digesta and longissimus muscle from lambs fed silage mixtures including red clover, sainfoin, and timothy

This work investigated the effects of feeding silage mixtures of a plant containing polyphenol oxidase (PPO; red clover [; RC]), a plant containing tannins (sainfoin [; SF]), and a grass species not containing these compounds (timothy [; T]) on ruminal and intramuscular (i.m.) fatty acids of lambs. Forty 4-mo-old castrated male Romane lambs, divided into 5 groups, received 1 of the following silages: 1) T (100%), 2) a binary mixture of timothy and tannin-containing sainfoin ( cv. Perly; 50:50 [T-SF]), 3) a binary mixture of timothy and PPO-containing red clover ( cv. Mervius; 50:50 [T-RC]), 4) a ternary mixture of timothy, sainfoin, and red clover containing both tannins and PPO (50:25:25, respectively [T-SF-RC]), and 5) a binary mixture of tannin-containing sainfoin and PPO-containing red clover (50:50 [SF-RC]). In the rumen digesta, the partial or total replacement of T with forage legumes was associated with greater concentrations of PUFA ( < 0.001) and 1esser concentrations of MUFA ( < 0.001). The inclusion of forage legumes in the silage favored the accumulation of 18:3 -3 ( < 0.001), with the greatest concentrations being observed in SF-RC. This latter diet also led to the greatest percentage of 18:2 -6 ( < 0.001). Forage legumes decreased the -11 18:1 to 30% of T in rumen digesta ( < 0.001). Forage legumes decreased the total concentration of branched-chain fatty acids in the rumen digesta (on average, -28%; < 0.001), this effect being less marked (-17%; = 0.014) in T-RC in comparison with T. The dietary treatment tended to affect the proportion of MUFA ( = 0.081) and of PUFA ( = 0.079) in the i.m. fat of the LM, respectively, at the highest and lowest numerical value in the T group. The sum of -3 fatty acids was less in the T and T-SF groups compared with the mixture of legumes without T (SF-RC; < 0.001 and < 0.008, respectively). The latter group had also a lesser -6-to--3 ratio than the T-SF group ( = 0.01). -11 18:1 was greater ( < 0.03) in lambs given T as the sole silage in comparison with lambs given T-RC, T-SF-RC, and SF-RC. Rumenic acid (-9 -11 CLA) was detected at a greater percentage in the LM from the animals fed the T silage compared with animals fed the T-SF-RC treatment ( = 0.004). Contrarily, -9 -12 -15 18:3 was found at a greater concentration in the muscle from lambs in the SF-RC treatment compared with lambs in the other treatments ( < 0.001). Furthermore, the T-RC group showed a greater proportion of α-linolenic acid than the T group ( = 0.03). In conclusion, the effects of the 2 active compounds (PPO and tannins) appear to be similar and additive. Moreover, a silage composed of a mixture of RC and SF is an excellent forage for growing lambs in terms of i.m. fatty acid composition.

Nutritional enhancement of sheep meat fatty acid profile for human health and wellbeing

Dietary fatty acids (FA) consumed by sheep, like other ruminants, can undergo biohydrogenation resulting in high proportions of saturated FA (SFA) in meat. Biohydrogenation is typically less extensive in sheep than cattle, and consequently, sheep meat can contain higher proportions of omega (n)-3 polyunsaturated FA (PUFA), and PUFA biohydrogenation intermediates (PUFA-BHI) including conjugated linoleic acid (CLA) and trans-monounsaturated FAs (t-MUFA). Sheep meat is also noted for having characteristically higher contents of branched chain FA (BCFA). From a human health and wellness perspective, some SFA and trans-MUFA have been found to negatively affect blood lipid profiles, and are associated with increased risk of cardiovascular disease (CVD). On the other hand, n-3 PUFA, BCFA and some PUFA-BHI may have many potential beneficial effects on human health and wellbeing. In particular, vaccenic acid (VA), rumenic acid (RA) and BCFA may have potential for protecting against cancer and inflammatory disorders among other human health benefits. Several innovative strategies have been evaluated for their potential to enrich sheep meat with FA which may have human health benefits. To this end, dietary manipulation has been found to be the most effective strategy of improving the FA profile of sheep meat. However, there is a missing link between the FA profile of sheep meat, human consumption patterns of sheep FA and chronic diseases. The current review provides an overview of the nutritional strategies used to enhance the FA profile of sheep meat for human consumption.

Polyphenol Oxidase Containing Sidestreams as Emulsifiers of Rumen Bypass Linseed Oil Emulsions: Interfacial Characterization and Efficacy of Protection against in Vitro Ruminal Biohydrogenation

The low transfer in ruminants of dietary polyunsaturated fatty acids to the milk or peripheral tissues is largely due to ruminal biohydrogenation. Lipids emulsified by a polyphenol oxidase (PPO) rich protein extract of red clover were shown before to be protected against this breakdown after cross-linking with 4-methylcatechol. Protein extracts of 13 other vegetal resources were tested. Surprisingly, the effectiveness to protect emulsified lipids against in vitro ruminal biohydrogenation largely depended on the origin of the extract and its protein concentration but was not related to PPO activity. Moreover, PPO isoforms in vegetal sources, effectively protecting emulsified lipids, were diverse and their presence at the emulsion interface did not seem essential. Potato tuber peels were identified as an interesting biological source of emulsifying proteins and PPO, particularly since protein extracts of industrial potato sidestreams proved to be suitable for the current application.

A PPO Promoter from Betalain-Producing Red Swiss Chard, Directs Petiole- and Root-Preferential Expression of Foreign Gene in Anthocyanins-Producing Plants

A 1670 bp 5'-flanking region of the polyphenol oxidase (PPO) gene was isolated from red Swiss chard, a betalain-producing plant. This region, named promoter BvcPPOP, and its 5'-truncated versions were fused with the GUS gene and introduced into Arabidopsis, an anthocyanins-producing plant. GUS histochemical staining and quantitative analysis of transgenic plants at the vegetative and reproductive stages showed that BvcPPOP could direct GUS gene expression in vegetative organs with root- and petiole-preference, but not in reproductive organs including inflorescences shoot, inflorescences leaf, flower, pod and seed. This promoter was regulated by developmental stages in its driving strength, but not in expression pattern. It was also regulated by the abiotic stressors tested, positively by salicylic acid (SA) and methyl jasmonate (MeJA) but negatively by abscisic acid (ABA), gibberellin (GA), NaCl and OH(-). Its four 5'-truncated versions varied in the driving strength, but not obviously in expression pattern, and even the shortest version (-225 to +22) retained the root- and petiole- preference. This promoter is, to our knowledge, the first PPO promoter cloned and functionally elucidated from the betalain-producing plant, and thus provides not only a useful tool for expressing gene(s) of agricultural interest in vegetative organs, but also a clue to clarify the function of metabolism-specific PPO in betalain biosynthesis.

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.

The scope for manipulating the polyunsaturated fatty acid content of beef: a review

Since 1950, links between intake of saturated fatty acids and heart disease have led to recommendations to limit consumption of saturated fatty acid-rich foods, including beef. Over this time, changes in food consumption patterns in several countries including Canada and the USA have not led to improvements in health. Instead, the incidence of obesity, type II diabetes and associated diseases have reached epidemic proportions owing in part to replacement of dietary fat with refined carbohydrates. Despite the content of saturated fatty acids in beef, it is also rich in heart healthy cis-monounsaturated fatty acids, and can be an important source of long-chain omega-3 (n-3) fatty acids in populations where little or no oily fish is consumed. Beef also contains polyunsaturated fatty acid biohydrogenation products, including vaccenic and rumenic acids, which have been shown to have anticarcinogenic and hypolipidemic properties in cell culture and animal models. Beef can be enriched with these beneficial fatty acids through manipulation of beef cattle diets, which is now more important than ever because of increasing public understanding of the relationships between diet and health. The present review examines recommendations for beef in human diets, the need to recognize the complex nature of beef fat, how cattle diets and management can alter the fatty acid composition of beef, and to what extent content claims are currently possible for beef fatty acids.

Subcutaneous adipose fatty acid profiles and related rumen bacterial populations of steers fed red clover or grass hay diets containing flax or sunflower-seed

Steers were fed 70∶30 forage∶concentrate diets for 205 days, with either grass hay (GH) or red clover silage (RC), and either sunflower-seed (SS) or flaxseed (FS), providing 5.4% oil in the diets. Compared to diets containing SS, FS diets had elevated (P<0.05) subcutaneous trans (t)-18:1 isomers, conjugated linoleic acids and n-6 polyunsaturated fatty acid (PUFA). Forage and oilseed type influenced total n-3 PUFA, especially α-linolenic acid (ALA) and total non-conjugated diene biohydrogenation (BH) in subcutaneous fat with proportions being greater (P<0.05) for FS or GH as compared to SS or RC. Of the 25 bacterial genera impacted by diet, 19 correlated with fatty acids (FA) profile. Clostridium were most abundant when levels of conjugated linolenic acids, and n-3 PUFA's were found to be the lowest in subcutaneous fat, suggestive of their role in BH. Anerophaga, Fibrobacter, Guggenheimella, Paludibacter and Pseudozobellia were more abundant in the rumen when the levels of VA in subcutaneous fat were low. This study clearly shows the impact of oilseeds and forage source on the deposition of subcutaneous FA in beef cattle. Significant correlations between rumen bacterial genera and the levels of specific FA in subcutaneous fat maybe indicative of their role in determining the FA profile of adipose tissue. However, despite numerous correlations, the dynamics of rumen bacteria in the BH of unsaturated fatty acid and synthesis of PUFA and FA tissue profiles require further experimentation to determine if these correlations are consistent over a range of diets of differing composition. Present results demonstrate that in order to achieve targeted FA profiles in beef, a multifactorial approach will be required that takes into consideration not only the PUFA profile of the diet, but also the non-oil fraction of the diet, type and level of feed processing, and the role of rumen microbes in the BH of unsaturated fatty acid.

An overview of the nutritional value of beef and lamb meat from South America

The southern region of South America, a subtropical and temperate zone, is an important region for the production of beef and lamb meat, which is mainly produced in extensive pasture-based systems. Because of its content in highly valuable nutrients such as iron, zinc, selenium, fatty acids, and vitamins, meat is a unique and necessary food for the human diet in order to secure a long and healthy life, without nutritional deficiencies. Beef and lamb production systems based on temperate or tropical grasslands show interesting and, in some cases, a differential content in minerals, fatty acids and vitamins. This review deals with the distinctive aspects of the nutritional quality of beef and lamb meat produced in this region in terms of nutritional composition and the bioavailability of key nutrients related to its contribution for a healthy diet for all ages.

Effect of replacing grass silage with red clover silage on nutrient digestion, nitrogen metabolism, and milk fat composition in lactating cows fed diets containing a 60:40 forage-to-concentrate ratio

Diets based on red clover silage (RCS) typically increase the concentration of polyunsaturated fatty acids (PUFA) in ruminant meat and milk and lower the efficiency of N utilization compared with grass silages (GS). Four multiparous Finnish Ayrshire cows (108 d postpartum) fitted with rumen cannulas were used in a 4 × 4 Latin square design with 21-d periods to evaluate the effect of incremental replacement of GS with RCS on milk production, nutrient digestion, whole-body N metabolism, and milk fatty acid composition. Treatments comprised total mixed rations offered ad libitum, containing 600 g of forage/kg of diet dry matter (DM), with RCS replacing GS in ratios of 0:100, 33:67, 67:33, and 100:0 on a DM basis. Intake of DM and milk yield tended to be higher when RCS and GS were offered as a mixture than when fed alone. Forage species had no influence on the concentration or secretion of total milk fat, whereas replacing GS with RCS tended to decrease milk protein concentration and yield. Substitution of GS with RCS decreased linearly whole-tract apparent organic matter, fiber, and N digestion. Forage species had no effect on total nonammonia N at the omasum, whereas the flow of most AA at the omasum was higher for diets based on a mixture of forages. Replacing GS with RCS progressively lowered protein degradation in the rumen, increased linearly ruminal escape of dietary protein, and decreased linearly microbial protein synthesis. Incremental inclusion of RCS in the diet tended to lower whole-body N balance, increased linearly the proportion of dietary N excreted in feces and urine, and decreased linearly the utilization of dietary N for milk protein synthesis. Furthermore, replacing GS with RCS decreased linearly milk fat 4:0 to 8:0, 14:0, and 16:0 concentrations and increased linearly 18:2n-6 and 18:3n-3 concentrations, in the absence of changes in cis-9 18:1, cis-9, trans-11 18:2, or total trans fatty acid concentration. Inclusion of RCS in the diet progressively increased the apparent transfer of 18-carbon PUFA from the diet into milk, but had no effect on the amount of 18:2n-6 or 18:3n-3 at the omasum recovered in milk. In conclusion, forage species modified ruminal N metabolism, the flow of AA at the omasum, and whole-body N partitioning. A lower efficiency of N utilization for milk protein synthesis with RCS relative to GS was associated with decreased availability of AA for absorption, with some evidence of an imbalance in the supply of AA relative to requirements. Higher enrichment of PUFA in milk for diets based on RCS was related to an increased supply for absorption, with no indication that forage species substantially altered PUFA bioavailability.

Forage polyphenol oxidase and ruminant livestock nutrition

Polyphenol oxidase (PPO) is predominately associated with the detrimental effect of browning fruit and vegetables, however, interest within PPO containing forage crops (crops to be fed to animals) has grown since the browning reaction was associated with reduced nitrogen (N) losses in silo and the rumen. The reduction in protein breakdown in silo of red clover (high PPO forage) increased the quality of protein, improving N-use efficiency [feed N into product N (e.g., Milk): NUE] when fed to ruminants. A further benefit of red clover silage feeding is a significant reduction in lipolysis (cleaving of glycerol-based lipid) in silo and an increase in the deposition of beneficial C18 polyunsaturated fatty acid (PUFA) in animal products, which has also been linked to PPO activity. PPOs protection of plant protein and glycerol based-PUFA in silo is related to the deactivation of plant proteases and lipases. This deactivation occurs through PPO catalyzing the conversion of diphenols to quinones which bind with cellular nucleophiles such as protein reforming a protein-bound phenol (PBP). If the protein is an enzyme (e.g., protease or lipase) the complexing denatures the enzyme. However, PPO is inactive in the anaerobic rumen and therefore any subsequent protection of plant protein and glycerol based-PUFA in the rumen must be as a result of events that occurred to the forage pre-ingestion. Reduced activity of plant proteases and lipases would have little effect on NUE and glycerol based-PUFA in the rumen due to the greater concentration of rumen microbial proteases and lipases. The mechanism for PPOs protection of plant protein in the rumen is a consequence of complexing plant protein, rather than protease deactivation per se. These complexed proteins reduce protein digestibility in the rumen and subsequently increase undegraded dietary protein flow to the small intestine. The mechanism for protecting glycerol-based PUFA has yet to be fully elucidated but may be associated with entrapment within PBP reducing access to microbial lipases or differences in rumen digestion kinetics of the forage and therefore not related to PPO activity.

Short Communication: Erythrocytes assayed early ante mortem can predict adipose tissue and muscle trans-18:1 isomeric profiles of steers fed red clover silage supplemented with flaxseed

Mapiye, C., Dugan, M. E. R., Turner, T. D., Rolland, D. C., Basarab, J. A., Baron, V. S., McAllister, T. A., Block, H. C., Uttaro, B. and Aalhus, J. L. 2013. Short Communication: Erythrocytes assayed early ante mortem can predict adipose tissue and muscle trans-18:1 isomeric profiles of steers fed red clover silage supplemented with flaxseed. Can. J. Anim. Sci. 93: 149–153. Steers were fed a red clover silage-based diet with or without flaxseed to evaluate over time the effects of flaxseed supplementation on erythrocytes (ERC) trans(t)18:1 isomers composition and their relationships to adipose tissue and muscle t18:1 profiles at slaughter. Concentrations of most ERC t18:1 isomers in steers fed flaxseed increased (P<0.01) markedly in the first 2 mo and increased gradually thereafter. Strong (P<0.01) correlations of t9-, t10- and t11-18:1 isomers were observed from month 2 to 6 between ERC and beef tissues collected at slaughter from steers fed flaxseed. Findings suggest that ERC sampled as early as 2 mo into the feeding period can be indicative of variation in beef t18:1 isomeric profile at a later slaughter date when feeding red clover silage with flaxseed.