Anne Ferlay

Effect of different types of forages, animal fat or marine oils in cow’s diet on milk fat secretion and composition, especially conjugated linoleic acid (CLA) and polyunsaturated fatty acids

This review summarises the known effects of forages, animal fats or marine oils on bovine milk fat secretion and composition. Special attention is given to fatty acids that could play a positive role for human health, such as butyric acid, oleic acid, C18 to C22 polyunsaturated fatty acids and conjugated linoleic acid (CLA). The efficiency of the transfer of n-3 polyunsaturated fatty acids from diet to milk is reviewed. Milk fat from pasture fed cows seems to be higher in linolenic acid than milk fat from cows receiving preserved grass or maize, but the magnitude of this difference is limited. Indirect comparisons show that milk fat from maize silage diets is richer in short-chain FA and linoleic acid when compared to grass silage diets. Compared to fresh grass, grass silage favours myristic and palmitic acids at the expense of mono- and polyunsaturated FA, including CLA. Protected tallow allows for a large increase in milk fat yield, and in the percentage of milk stearic and oleic acids, at the expense of medium chain FA. Non-protected tallow has a similar effect on medium chain FA without increasing so much C18 FA yield, which explains that it does not increase milk fat yield. Dose–response curves of milk CLA are reviewed for marine oil supplements, as well as the relationship between milk CLA and trans-C18:1 contents. The potential of marine oil supplementation to increase the mean CLA content in cow milk fat is large (more than 300% above basal values). A specific role for dietary C20:5 n-3 in the sharp decrease in milk fat secretion after fish oil supplementation is suggested. However, there is a need to evaluate how the different feeding strategies could change the other aspects of milk fat quality, such as taste, oxidative stability or manufacturing value.

Digestion and utilisation of fatty acids by ruminants

Abstract This review deals with the quantitative and qualitative changes in fatty acids (FA) throughout the total digestive tract of ruminants. Special attention is paid to the causes of variation in the extent to which different mechanisms contribute to the ruminal metabolism and intestinal digestion of FA. Most results obtained with diets not supplemented with lipids show that the FA flow leaving the rumen is higher than FA intake. This is due to bacterial synthesis of FA in the rumen. With diets supplemented with lipids, the FA balance at the end of the rumen is often negative. The cause of this apparent disappearance of FA is not known. In the rumen, lipids are first hydrolysed to a very large extent; then unsaturated FA are hydrogenated. Hydrogenation is almost complete for linolenic acid, and amounts to between 60 and 95% for linoleic acid. This proportion decreases when the level of concentrates increases in the diet. Digestibility of FA in the small intestine ranges from 70 to 90% and is not related to the level of FA intake. Contrary to the situation in monogastric animals, there are only moderate differences in the digestibility of individual FA. It appears to be higher for palmitic and stearic acids than for other saturated FA, and for oleic and linoleic acids than for stearic and linolenic acids. In the large intestine, there is synthesis of FA which are probably not absorbed.

Adipose tissue metabolism and its role in adaptations to undernutrition in ruminants.

Changes in the amount and metabolism of adipose tissue (AT) occur in underfed ruminants, and are amplified during lactation, or in fat animals. The fat depot of the tail of some ovine breeds seems to play a particular role in adaptation to undernutrition; this role could be linked to its smaller adipocytes and high sensitivity to the lipolytic effect of catecholamines. Glucocorticoids and growth hormone probably interact to induce teleophoretic changes in the AT responses to adenosine and catecholamines during lactation. Fat mobilization in dry ewes is related both to body fatness and to energy balance. The in vivo beta-adrenergic lipolytic potential is primarily related to energy balance, whereas basal postprandial plasma non-esterified fatty acids (NEFA) are related to body fatness, and preprandial plasma NEFA is the best predictor of the actual body lipid loss. Several mechanisms seem to be aimed at avoiding excessive fat mobilization and/or insuring a return to the body fatness homeostatic set point. As well as providing the underfed animal with fatty acids as oxidative fuels, AT acts as an endocrine gland. The yield of leptin by ruminant AT is positively related to body fatness, decreased by underfeeding, beta-adrenergic stimulation and short day length, and increased by insulin and glucocorticoids. This finding suggests that the leptin chronic (or acute) decrease in lean (or underfed respectively) ruminants is, as in rodents, a signal for endocrine, metabolic and behavioural adaptations aimed at restoring homeostasis.

Oilseed Lipid Supplements and Fatty Acid Composition of Cow Milk: A Meta-Analysis

Numerous experiments have studied the use of oilseed supplements in cow diets to alter milk fatty acid (FA) composition, but no quantitative synthesis of these studies is currently available. This article reports a meta-analysis of the response of cow milk FA composition to oilseed lipid supplements from linseed, rapeseed, soybeans, and sunflower seed. First, from a database of 145 oilseed supplementation experiments, we collected the mean FA percentages observed with unsupplemented diets and diets supplemented with the 4 oilseeds given as seeds (after various types of processing), as oils (including Ca salts and amides), or in protected forms. Second, we studied the response of the major milk FA percentages to increasing amounts of supplemental lipids from the 4 oilseeds. Responses were nonsignificant, linear, or quadratic, depending on the FA studied and the supplement. Effects of interfering factors, such as supplement form, forage component of the diet, or lactation stage, were difficult to assess from the available data. Third, we studied the response of the major milk FA percentages to increasing dietary intakes of linoleic or linolenic acids, taken separately. Overall, these results confirm the high plasticity of milk FA composition, with the widest variations being observed in the percentages of medium-chain versus C18 FA, and among the C18 in 18:0, cis-18:1, and trans-18:1. The percentages of the polyunsaturated FA cis-9 cis-12-18:2 and 18:3 were less variable, except when protected lipids (mostly formaldehyde treated) were supplied. However, trans-18:1 and polyunsaturated FA (including conjugated linoleic acid) exhibited the greatest variations when expressed relative to their respective basal values (for unsupplemented diets). Oils, compared with seeds, induced greater percentages of trans-18:1 and tended to decrease C6 to C12 FA more. Intakes of 18:2- and 18:3-rich lipid sources did not differ greatly in their effects on short- and medium-chain FA and trans-18:1 percentages, although the profiles of individual 18:1 and 18:2 isomers in milk differed. This meta-analysis provides quantitative estimates, obtained from the extensive literature produced over more than 40 yr, of the impact of oilseed supplements on milk FA composition.

Examination of the persistency of milk fatty acid composition responses to plant oils in cows given different basal diets, with particular emphasis on trans-C18:1 fatty acids and isomers of conjugated linoleic acid

It is well established that plant oils reduce milk saturated fatty acid content and enhance concentrations of conjugated linoleic acid (CLA) and trans C 18:1 in milk fat, but there is increasing evidence to suggest that milk fat CLA responses are often transient and decline over time. It is probable that time dependent adaptations in ruminal biohydrogenation and changes in milk fatty acid composition to lipid supplements are, at least in part, related to the composition of the basal diet. To test this hypothesis, 18 Holstein cows were used in a continuous randomized block design to examine changes in milk fatty acid composition over time in response to plant oils included in diets of variable composition. Cows were randomly allocated to one of three basal diets containing (g/kg dry matter (DM)) maize silage (267) and concentrates (733) (diet C); maize silage (332), grass hay (148) and concentrates (520) (diet M), or grass hay (642) and concentrates (358) (diet H). Basal rations were offered for 21 days, after which diets were supplemented with 50 g sunflower per kg DM (diets C-S and M-S) or 50 g linseed oil per kg DM (diet H-L). Oils were included in all rations incrementally over a five day period (days 0–4), and responses to 50 g/kg DM of the respective oils were evaluated for 17 days (days 4 to 20). Milk fatty acid composition was intensively monitored from days −2 to 20. In contrast to the H-L diet, both C-S and M-S treatments decreased ( P P cis -9, trans -11 CLA and trans -11 C 18:1 contents were enhanced on the C-S and M-S treatments but the increases were transient reaching the highest concentrations between days 4 and 6 ( cis -9, trans -11 CLA: 1·94 and 2·18 g per 100 g total fatty acids; trans -11 C 18:1 : 4·88 and 6·23 g per 100 g total fatty acids, respectively) but declined thereafter. In marked contrast, concentrations of cis -9, trans -11 CLA and trans -11 C 18:1 in milk from the H-L diet increased gradually over time, responses that were maintained until the end of the experiment (2·89 and 7·49 g per 100 g total fatty acids, respectively).Decreases in milk fat cis -9, trans -11 CLA and trans -11 C 18:1 after day 6 on the M-S and C-S diets were associated with concomitant increases in milk fat trans -10 C 18:1 content reaching 7·22 and 18·62 g per 100 g total fatty acids on day 18, respectively, whereas concentrations of trans -10 C 18:1 in milk on the H-L diet remained low throughout the experiment (0·70 g per 100 g total fatty acids on day 18). Furthermore, milk fat trans -11, cis -13 CLA, trans -11, trans -13 CLA and trans -12, trans -14 CLA contents were all enhanced on the H-L diet, while the M-S and C-S diets increased trans -8, cis -10 CLA, trans -10, cis -12 CLA and trans -9, cis -11 CLA concentrations. Across all diets, decreases in milk fat content were associated with increases in milk trans -10 C 18:1 , trans -10, cis -12 and trans -9, cis -11 CLA concentrations (r 2 =0·93, 0·88 and 0·89, respectively). In conclusion, the relative abundance of trans C 18:1 and CLA isomers in milk fat were dependent on the composition of the basal diet, type of plant oil and duration of lipid supplementation, highlighting the challenges in developing nutritional strategies for the production of milk highly enriched with CLA over an extended period of time.

Effect of dietary lipids on nitrogen metabolism in the rumen: a review

This paper deals with the influence of supplementary lipids in the diet on protein degradation and microbial synthesis in the rumen, through the effect of lipids on the microbial ecosystem. Global effects of lipids can be summarized by a trend to decrease ammonia ruminal concentration but duodenal non-ammonia nitrogen flow is not modified. The two components of this flow, non-microbial and microbial flows, generally are not modified so that it can be deduced that modifications of degradation and microbial synthesis due to lipid addition are of low extent. The efficiency of microbial synthesis depends on the nature of fatty acids and is increased especially when organic matter ruminal digestibility is depressed; this can be related to the decrease in protozoa number in the rumen.

Long-Chain Fatty Acid Metabolism in Dairy Cows: A Meta-Analysis of Milk Fatty Acid Yield in Relation to Duodenal Flows and De Novo Synthesis

This study is a meta-analysis of the response of milk long-chain fatty acid (FA) yield and composition to lipid supply, based on published experiments reporting duodenal FA flows or duodenal lipid infusions and milk FA composition (i.e., 39 experiments reporting 139 experimental treatments). Analysis of these data underlined the interdependence between milk yields of C18 and short- and medium-chain (C4 to C16) FA. Lipid supplementation (producing an increase in duodenal C18 flow) decreased linearly milk C4 to C16 yield (-0.26 g of C4 to C16 produced per gram of duodenal C18 flow increase) and increased quadratically milk C18 yield. When these 2 effects increased the percentage of C18 in milk FA up to a threshold value (around 52% of total FA), then milk C18 yield was limited by C4 to C16 yield, decreasing the C18 transfer efficiency from duodenum to milk with high-lipid diets. Moreover, for a given duodenal C18 flow, a decrease in milk C4 to C16 yield induced a decrease in milk C18 yield. Despite high variations in C18 transfer efficiency between duodenum and milk, for a given experimental condition, the percentages of C18 FA in milk total C18 could be predicted from their percentages in duodenal C18, and the percentages at the duodenum and in milk were very similar when mammary desaturation was taken into account (i.e., considering the sums of substrates and products of mammary desaturase). The estimated amounts of 18:0, trans-11-, and trans-13-18:1 desaturated by the mammary gland were a linear function of their mammary uptake, and mammary desaturation was responsible for 80, 95, and 81%, respectively, of the yield of their products (i.e., cis-9-18:1; cis-9, trans-11-, and cis-9, trans-13-18:2). Thus, mammary FA desaturation capacity did not seem to be a limiting factor in the experimental conditions published so far.

Effects of supplementation of maize silage diets with extruded linseed, vitamin E and plant extracts rich in polyphenols, and morning v . evening milking on milk fatty acid profiles in Holstein and Montbéliarde cows

The aim of this study was to evaluate the effects on dairy performance and milk fatty acid (FA) composition of (i) supplementation with extruded linseed (EL), (ii) supplementation with synthetic or natural antioxidants, namely vitamin E and plant extracts rich in polyphenols (PERP), (iii) cow breed (Holstein v. Montbéliarde) and (iv) time of milking (morning v. evening). After a 3-week pre-experimental period 24 lactating cows (12 Holstein and 12 Montbéliarde) were divided up into four groups of six cows: the first group received a daily control diet (diet C) based on maize silage. The second group received the same diet supplemented with EL (diet EL, fat level approximately 5% of dietary dry matter (DM)). The third group received the EL diet plus 375 IU/kg diet DM of vitamin E (diet ELE). The fourth group received the ELE diet plus 10 g/kg diet DM of a PERP mixture (diet ELEP). Compared with the diet C, feeding EL-rich diets led to lower concentrations of total saturated FA (SFA) and higher concentrations of stearic and oleic acids, each trans and cis isomer of 18:1 (except c12-18:1), non-conjugated isomers of 18:2, some isomers (c9t11-, c9c11- and t11t13-) of conjugated linoleic acid (CLA), and 18:3n-3. The vitamin E supplementation had no effect on milk yield, milk fat or protein percentage and only moderate effects on milk concentrations of FA (increase in 16:0, decreases in 18:0 and t6/7/8-18:1). The addition of PERP to vitamin E did not modify milk yield or composition and slightly altered milk FA composition (decrease in total saturated FA (SFA) and increase in monounsaturated FA (MUFA)). The minor effects of vitamin E may be partly linked to the fact that no milk fat depression occurred with the EL diet. During both periods the Holstein cows had higher milk production, milk fat and protein yields, and milk percentages of 4:0 and 18:3n-3, and lower percentages of odd-branched chain FA (OBCFA) than the Montbéliarde cows. During the experimental period the Holstein cows had lower percentages of total cis 18:1, and c9,c11-CLA, and higher percentages of 6:0, 8:0, t12-, t16/c14- and t13/14-18:1, and 18:2n-6 than Montbéliarde cows because of several significant interactions between breed and diet. Also, the total SFA percentage was higher for morning than for evening milkings, whereas those of MUFA, total cis 18:1, OBCFA and 18:2n-6 were lower. Extruded linseed supplementation had higher effect on milk FA composition than antioxidants, breed or time of milking.

Plant polyphenols associated with vitamin E can reduce plasma lipoperoxidation in dairy cows given n-3 polyunsaturated fatty acids

Diets rich in n-3 polyunsaturated fatty acids (PUFA) improve the nutritional value of ruminant products but also increase the risk of lipoperoxidation in plasma and tissues. The relative effectiveness of dietary antioxidants such as vitamin E (vit E) given alone or with plant extracts rich in polyphenols (PERP) containing rosemary, grape, citrus, and marigold was investigated in the plasma of mid-lactation dairy cows given diets enriched in 18:3 n-3. For a 30-d period, the animals were given a maize silage-based diet (control group C, n = 6) or the same basal diet supplemented with extruded linseed rich in 18:3 n-3 [50 g of oil/kg of diet dry matter (DM); group L, n = 6], extruded linseed + vit E (375 international units/kg of diet DM; 7,500 IU/cow per day; group LE, n = 6), or extruded linseed + vit E + PERP (10 g/kg of diet DM; group LEP, n = 5). Plasma susceptibility to lipoperoxidation was evaluated using in vitro parameters of conjugated diene formation (lag phase and maximum oxidation rate). Plasma indicators of lipoperoxidation and antioxidant status were analyzed in the 4 experimental groups as well as the fatty acid (FA) composition of total plasma lipids. At d 30, group L significantly increased plasma cholesterol esters (+57%) and phospholipids (+35%) compared with group C. It also increased plasma n-3 PUFA (4.7-fold increase) to the detriment of n-6 PUFA (-30%), leading to a higher peroxidizability index (+20%). Plasma in vitro lipoperoxidation was higher in group L (rich in 18:3 n-3) than in group C. Vitamin E alone had no effect on lipoperoxidation, whereas vit E in association with PERP lowered lipoperoxidation by increasing the resistance time against peroxidation (+47%) and by decreasing the oxidation rate (-48%) compared with group L at d 30. Surprisingly, in vivo plasma lipoperoxidation estimated by the plasma level of the major lipoperoxidation product (malondialdehyde) was not significantly increased in group L. This study shows, for the first time, that PERP supplied in association with vit E were able to reduce lipoperoxidation in lactating cows given a diet rich in 18:3 n-3, thereby helping to protect cows against the deleterious consequences of lipoperoxidation and potentially ensuring antioxidant potential for 18:3 n-3-enriched dairy products.

Optimising goat's milk and cheese fatty acid composition

Publisher Summary Lipid composition is one of the most important components of the technological and nutritional quality of goat milk. Besides their quantitative contribution to the amount of dietary energy, the different lipid and Fatty Acid [“FA”] compounds (cholesterol, short and medium chain saturated, branched, mono- and polyunsaturated, cis and trans , conjugated FA, etc.) are potentially involved as positive or negative predisposing factors for the health of human consumers. The FA composition of caprine dairy products depends largely on animal factors, although the effect of technological factors is very low. It is clear that the plasticity of milk fat composition is very large, with numerous interactions between forage, concentrates, oils and vitamins, on almost all major and minor FAs. It is highlighted that the addition of vegetable oils to maize silage diets increases sharply the trans FAs other than rumenic and vaccenic acids. The aim of future research is to better understand the effects of using grass-based diets, new combinations of feedstuffs and nutrients in concentrates, and oilseed technology and processing, in order to increase more selectively FAs of interest for human nutrition, without increasing less desired FAs and without decreasing the sensory quality of dairy products.