In vitro study of red clover polyphenol oxidase activity, activation, and effect on measured lipase activity and lipolysis

Producing natural functional and low-carbon milk by regulating the diet of the cattle-The fatty acid associated rumen fermentation, biohydrogenation, and microorganism response

Conjugated linoleic acid (CLA) has drawn significant attention in the last two decades for its various potent beneficial effects on human health, such as anticarcinogenic and antidiabetic properties. CLA could be generally found in ruminant products, such as milk. The amount of CLA in ruminant products mainly depends on the diet of the animals. In general, the fat content in the ruminant diet is low, and dietary fat supplementation can be provided to improve rumen activity and the fatty acid (FA) profile of meat and milk. Especially, dietary 18-carbon polyunsaturated FA (C18 PUFA), the dominant fat source for ruminants, can modify the milk FA profile and other components by regulating the ruminal microbial ecosystem. In particular, it can improve the CLA in milk, intensify the competition for metabolic hydrogen for propionate producing pathways and decrease methane formation in the rumen. Therefore, lipid supplementation appears to be a promising strategy to naturally increase the additional nutritional value of milk and contribute to lower methane emissions. Meanwhile, it is equally important to reveal the effects of dietary fat supplementation on rumen fermentation, biohydrogenation (BH) process, feed digestion, and microorganisms. Moreover, several bacterial species and strains have been considered to be affected by C18 PUFA or being involved in the process of lipolysis, BH, CLA, or methane emissions. However, no review so far has thoroughly summarized the effects of C18 PUFA supplementation on milk CLA concentration and methane emission from dairy cows and meanwhile taken into consideration the processes such as the microorganisms, digestibility, rumen fermentation, and BH of dairy cattle. Therefore, this review aims to provide an overview of existing knowledge of how dietary fat affects rumen microbiota and several metabolic processes, such as fermentation and BH, and therefore contributes to functional and low-carbon milk production.

Effects of vegetable oil supplementation on rumen fermentation and microbial population in ruminant: a review

Understanding the nature of ruminant nutrition and digestion is essential to improve feeding management and animal production. Among many approaches, manipulating ruminant nutrition and fermentation through feed supplementation is being practised and researched. Over the last decade, the utilization of vegetable oils in feed formulation and their effects on various aspects of ruminants have been reported by many researchers. It is important to understand the lipid metabolism in ruminants by microorganisms because it affects the quality of ruminant-derived products such as meat and milk. Majority of vegetable oil supplementation could reduce rumen protozoa population in ruminants due to the effects of medium-chain fatty acids (FAs). However, vegetable oil also contains unsaturated FAs that are known to have a negative effect on cellulolytic bacteria which could show inhibitory effects of the fibre digestion. In this paper, the physiology of nutrient digestion of ruminants is described. This paper also provides a current review of studies done on improvement and modification of rumen fermentation and microbial population through vegetable oil supplementation.

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.

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.

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.

Stability of fatty acids during wilting of perennial ryegrass (Lolium perenne L.): effect of bruising and environmental conditions

BACKGROUND

Oxidation of fatty acids (FA) during field wilting of herbage could cause extensive losses of polyunsaturated FA. Recent studies showed a variable effect of wilting on the losses of FA. This suggests that environment and management conditions influence the loss of FA during wilting. The present study investigated the stability of FA in untreated and mechanically bruised perennial ryegrass, wilted under field conditions for 0, 12, 24, 36 and 48 h, or wilted under controlled climate conditions at three temperatures (15, 25 or 35 °C) and two light (dark or light) regimes to dry matter (DM) contents of 425, 525 or 625 g kg(-1).

RESULTS

During 48 h of field wilting, the total FA content declined (15.2 to 11.9 g kg(-1) DM) consistently, despite an increase in herbage DM content (197 to 676 g kg(-1)). Under controlled climate conditions, the herbage total FA content declined (15.1 to 11.7 g kg(-1) DM) mainly during the prolonged (56 to 62 h) initial drying to a DM content of 425 g kg(-1) and did not decline with further drying to DM contents of 525 and 625 g kg(-1). The decline in total FA was associated with a parallel decline in C18:3 content under field (9.15 to 6.36 g kg(-1) DM) and controlled (9.12 to 6.15 g kg(-1) DM) conditions. Concomitantly, the proportion of C18:3 in total FA decreased, whilst the proportion of C16:0 and C18:0 increased. Lower losses of FA (P<0.05) were observed at 15 °C compared to 25 and 35 °C. Light did not affect the losses of FA during wilting.

CONCLUSIONS

The duration of the wilting period mainly affected the changes in FA content and composition. Stability of FA in herbage could be increased by minimising the duration of wilting.