Comparison of the fatty acid profiles in cheeses from ewes fed diets supplemented with different plant oils

Fatty Acids Profile and Consumers' Preferences of Pecorino Cheese Manufactured from Milk of Sheep Supplemented with Flaxseed and Ascophyllum nodosum

The impact of flaxseed and Ascophyllum nodosum supplementation in ewes during the summer season on the fatty acid and sensory profile and consumer preference for cheese was evaluated. Comisana ewes (n = 32) were divided into four groups: a control (CON) group fed (30 days) with pelleted concentrate, a flaxseed (FS) group fed with whole flaxseed supplementation (250 g/ewe per day), an A. nodosum (AN) group fed with 5% of A. nodosum (into 1 kg/ewe of pelleted concentrate), and an FS + AN group fed with a combination of algae and flaxseed. Pecorino cheeses were analysed after 1 day (curd) and after 45 days (cheese) of ripening. Curd from the FS and FS + AN groups registered higher contents of MUFA, n-3, and n-3/n-6, and lower levels of atherogenic and thrombogenic indexes than curd from the CON and AN groups, as well as a higher content of C18:3n-3, C18:2t9t12, and CLA9c11t, and n-3 and n-3/n-6 fatty acids. Consumers attributed the lowest scores for appearance attributes to AN Pecorino cheese; while Pecorino cheese from FS and FS + AN was judged to have a high-strength flavour attribute and a low rancid, mouldy, and piquant flavour, in comparison with cheese from AN. Flaxseed supplementation could be an effective strategy to improve the nutritional quality of the lipid fraction of cheese without having a detrimental impact on its sensory attributes, especially during the summer season.

Enrichment of Ewe’s Milk with Dietary n-3 Fatty Acids from Palm, Linseed and Algae Oils in Isoenergetic Rations

Increasing the levels of n-3 fatty acids (FA) in dairy products is an important goal in terms of enhancing the nutritional value of these foods for the consumer. The purpose of this research was to evaluate the effects of linseed and algae oil supplements in ovine isoenergetic diets on healthy milk fatty acid composition, mainly n-3. Seventy-two Churra dairy ewes were divided and randomly assigned to four experimental treatments for 6 weeks. The treatments consisted of a TMR (40:60 forage:concentrate ratio) that varied according to the inclusion of different types of fat (23 g/100 g TMR): hydrogenated palm oil (control), linseed oil (LO), calcium soap of linseed oil (CaS-LO) and marine algae oil (AO). The most effective lipid supplement to increase n-3 FA in milk was AO. 22:6 n-3 and total n-3 PUFA content increased from 0.02 and 0.60% (control) to 2.63 and 3.53% (AO), respectively. All diets supplemented with n-3 FA diminished the content of saturated FA in milk and its atherogenic index, while the levels of trans-11 18:1 and cis-9 trans-11 18:2 significantly increased. Overall, the enhancement of n-3 FA in ewe’s milk would be advantageous for the manufacture of nutritionally improved cheeses.

Dietary strategies to enrich milk with healthy fatty acids – a review

Feed is the main factor impacting the composition and quality of milk of dairy animals. Therefore, the present review explores the effects of feed and nutrition on milk fat content and levels of healthy fatty acids (FA) in milk consumed by humans. Milk and dairy products are two main sources of healthy and unhealthy FA in human nutrition. The concentrations of FA in milk depend mainly on diets; therefore, milk FA concentrations and ratios can be greatly altered by some feeding strategies. Dietary supplementation of the diets of dairy livestock with vegetable seeds or oils, microalgae and phytogenic feed additives, and feeding of some grasses can enhance the contents of healthy FA, including n-3 FA, α-linolenic acid, conjugated linoleic acid (CLA) and, generally, unsaturated FA in milk and dairy products. Enrichment of milk with healthy FA may make milk a source of anticarcenogens (CLA and polyphenols) for human health. This review, therefore, focusses on the current research findings on enrichment of milk with healthy FA and summarizes some effective supplementation strategies to alter milk FA profile.

Effect of Dietary Supplementation with Lipids of Different Unsaturation Degree on Feed Efficiency and Milk Fatty Acid Profile in Dairy Sheep

Lipids of different unsaturation degree were added to dairy ewe diet to test the hypothesis that unsaturated oils would modulate milk fatty acid (FA) profile without impairing or even improving feed efficiency. To this aim, we examined milk FA profile and efficiency metrics (feed conversion ratio (FCR), energy conversion ratio (ECR), residual feed intake (RFI), and residual energy intake (REI)) in 40 lactating ewes fed a diet with no lipid supplementation (Control) or supplemented with 3 fats rich in saturated, monounsaturated and polyunsaturated FA (i.e., purified palmitic acid (PA), olive oil (OO), and soybean oil (SBO)). Compared with PA, addition of OO decreased milk medium-chain saturated FA and improved the concentration of potentially health-promoting FA, such as cis-9 18:1, trans-11 18:1, cis-9 trans-11 CLA, and 4:0, with no impact on feed efficiency metrics. Nevertheless, FA analysis and decreases in FCR and ECR suggested that SBO supplementation would be a better nutritional strategy to further improve milk FA profile and feed efficiency in dairy ewes. The paradox of differences observed depending on the metric used to estimate feed efficiency (i.e., the lack of variation in RFI and REI vs. changes in FCR and ECR) does not allow solid conclusions to be drawn in this regard.

Short-term forage substitution with ensiled olive cake increases beneficial milk fatty acids in lactating cows

This study aimed to evaluate the effect of short-term forage substitution with ensiled olive cake (OC), on yield, composition and fatty acid (FA) profile of cows' milk. Mid-lactating Holstein-Friesian cows were randomly assigned for 21 days to two isoenergetic and isoproteic feeding treatments (12 animals per treatment), containing 0 and 10% DM of ensiled OC (C and OC groups, respectively). Milk yield was recorded daily, and milk samples were collected at 14 and 21 days of the trial for analyzing the fat, protein, and FA profile of milk. No significant differences were observed in milk yield, protein, and fat nor in protein and fat percentage of milk between groups. However, dietary supplementation with ensiled OC modified the FA profile of cow milk. Feeding cows with ensiled OC resulted in a significant decline of medium-chain FA, while long-chain and mono-unsaturated FA were risen in milk (P < 0.05). Among individual saturated FA, palmitic was particularly reduced, while among individual mono-unsaturated FA, increments of C18:1 cis-9 were demonstrated with the OC treatment (P < 0.05). Although total poly-unsaturated FA were decreased, the concentration of CLA cis-9, trans-11 tended to be elevated with OC feeding (P = 0.06). Overall, short-term forage substitution with ensiled OC improved, beneficially for human health, the lipid profile of milk without adversely affecting milk yield or milk composition of lactating cows.

Effect of Dietary Vegetable Sources Rich in Unsaturated Fatty Acids on Milk Production, Composition, and Cheese Fatty Acid Profile in Sheep: A Meta-Analysis

A meta-analysis was conducted to analyze the effects of different dietary vegetable sources rich in unsaturated FA (UFA) on sheep cheese FA profile. This study also quantified the overall effect of feeding sheep with vegetable sources rich in UFA (linseed, flaxseed, sunflower seed, canola, olive oil, bran oil, and olive cake), on milk yield (MY) and milk composition. A literature search was conducted to identify papers published from 2000 to 2019. Effect size for all parameters was calculated as standardized mean difference. Heterogeneity was determined using I ² statistic, while meta-regression was used to examine factors influencing heterogeneity. Effect size was not significant for MY, milk fat percentage (MFP), and milk protein percentage (MPP). Dietary inclusion of vegetable sources rich in UFA decreased the effect size for C12:0, C14:0, and C16:0 and increased the effect size for C18:0, C18:1 t-11, C18:1 c-9, C18:2 c-9, t-11, C18:2 n-6, and C18:3 n-3. Heterogeneity was significant for MY, MFP, MPP, and overall cheese FA profile. Meta-regression revealed days in milk as a contributing factor to the heterogeneity observed in MFP and MPP. Meta-regression showed that ripening time is one of the factors affecting cheese FA profile heterogeneity while the type of feeding system(preserved roughages vs. pasture) had no effect on heterogeneity. Overall, inclusion of dietary vegetable sources rich in UFA in sheep diets would be an effective nutritional strategy to decrease saturated FA and increase polyunsaturated FA contents in cheeses without detrimental effects on MY, MFF, and MPP.

Nutritional Indices for Assessing Fatty Acids: A Mini-Review

Dietary fats are generally fatty acids that may play positive or negative roles in the prevention and treatment of diseases. In nature, fatty acids occur in the form of mixtures of saturated fatty acid (SFA), monounsaturated fatty acid (MUFA), and polyunsaturated fatty acid (PUFA), so their nutritional and/or medicinal values must be determined. Herein, we do not consider the classic indices, such as ∑SFA, ∑MUFA, ∑PUFA, ∑n-6 PUFA, ∑n-3 PUFA, and n-6 PUFA/n-3 PUFA; instead, we summarize and review the definitions, implications, and applications of indices used in recent years, including the PUFA/SFA, index of atherogenicity (IA), the index of thrombogenicity (IT), the hypocholesterolemic/hypercholesterolemic ratio (HH), the health-promoting index (HPI), the unsaturation index (UI), the sum of eicosapentaenoic acid and docosahexaenoic acid (EPA + DHA), fish lipid quality/flesh lipid quality (FLQ), the linoleic acid/α-linolenic acid (LA/ALA) ratio, and trans fatty acid (TFA). Of these nutritional indices, IA and IT are the most commonly used to assess the composition of fatty acids as they outline significant implications and provide clear evidence. EPA + DHA is commonly used to assess the nutritional quality of marine animal products. All indices have their advantages and disadvantages; hence, a rational choice of which to use is critical.

Sheep and Goats Respond Differently to Feeding Strategies Directed to Improve the Fatty Acid Profile of Milk Fat

Simple Summary

Sheep and goat milk, as well as dairy products, are considered good sources of high-quality nutrients, particularly proteins and fats. Many positive effects on human health have been attributed to the consumption of dairy containing specific fatty acids, including some compounds originating from the polyunsaturated FA (PUFA) biohydrogenation operated by rumen microbes. In this bibliographic review, several nutritional strategies able to improve the milk fatty acids (FA) profile, in terms of an increase in the concentration of fatty acids considered beneficial to human health, are presented and discussed, with special attention to the differences between the two species.

Abstract

This bibliographic review presents and discusses the nutritional strategies able to increase the concentration of beneficial fatty acids (FA) in sheep and goat milk, and dairy products, with a particular focus on the polyunsaturated FA (PUFA), and highlights differences between the two species. In fact, by adopting appropriate feeding strategies, it is possible to markedly vary the concentration of fat in milk and improve its FA composition. These strategies are based mostly on the utilization of herbage rich in PUFA, or on the inclusion of vegetable, marine, or essential oils in the diet of lactating animals. Sheep respond more effectively than goats to the utilization of fresh herbage and to nutritional approaches that improve the milk concentration of c9,t11-conjugated linoleic acid (c9,t11-CLA) and α-linolenic acid. Dietary polyphenols can influence milk FA profile, reducing or inhibiting the activity and growth of some strains of rumen microbes involved in the biohydrogenation of PUFA. Although the effectiveness of plant secondary compounds in improving milk FA composition is still controversial, an overall positive effect has been observed on the concentration of PUFA and RA, without marked differences between sheep and goats. On the other hand, the positive effect of dietary polyphenols on the oxidative stability of milk fat appears to be more consistent.

Can Agro-Industrial By-Products Rich in Polyphenols be Advantageously Used in the Feeding and Nutrition of Dairy Small Ruminants?

Simple Summary

In the Mediterranean area, where dairy sheep and goats are widespread, the use of by-products in the diet of small ruminants is an ancient practice. Today the great availability of industrial by-products produced at the local level (e.g., grape, olive, tomato and myrtle residues), appears to be a promising strategy for reducing competition with human edible foods and the cost of off-farm produced feeds since they are imported worldwide. Moreover, these co-feeds can contribute to reducing the ecological and water footprint associated with crop cultivation. The presence of bioactive compounds, such as polyphenols, confers added value to these materials. Several positive aspects are apparent when such by-products are included in the diets of small dairy ruminants, in particular on ruminal metabolism, animal health, and the quality of derived products.

Abstract

Recently, the interest in industrial by-products produced at the local level in Mediterranean areas, resulting from fruit and vegetable processes, has increased because of their considerable amounts of bioactive compounds, including polyphenols. In this review, we analyze the most recent scientific results concerning the use of agro-industrial by-products, naturally rich in polyphenols (BPRP), in the diets of small dairy ruminants. Effects on milk production, milk and rumen liquor fatty acid profile, metabolic parameters, and methane production are reviewed. The feed intake and digestibility coefficients were generally depressed by BPRP, even though they were not always reflected in the milk yield. The main observed positive effects of BPRP were on quality of the milk’s FA profile, antioxidant activity in milk and blood, a reduction of rumen ammonia, and, consequently, a reduction of milk and blood urea. The expected beneficial effects of dietary polyphenols in small ruminants were not always observed because of their complex and variable matrices. However, owing to the large quantities of these products available at low prices, the use of BPRB in small ruminant nutrition offers a convenient solution to the valorization of residues arising from agricultural activities, reducing feed costs for farmers and conferring added value to dairy products at the local level, in a sustainable way.

Effect of forage type in the ovine diet on the nutritional profile of sheep milk cheese fat

The high nutritional value of sheep milk can be advantageous in the manufacture of cheese, and fat plays an important role in sheep cheese properties. The aim of this study was to investigate the effect of feeding common hay or silage diets used in commercial farms on the nutritional value of sheep cheese fat. We also monitored the effect of cheese ripening period on the fatty acid profile. Cheeses were produced from milk of sheep fed hay and silage diets from 8 farms, on 4 separate occasions (February, May, August, and November) over a 1-yr period. Eighty-four individual fatty acids were determined and identified by gas chromatography. Ripening time (100 and 180 d) significantly reduced moisture, acidity, and water activity of cheeses but did not affect the fatty acid content. However, hay feeding, compared with silage feeding, led to cheeses with 1.5- and 1.3-fold higher contents of vaccenic acid and conjugated linoleic acid, without detrimental changes in saturated and n-3 (omega-3) fatty acid composition. Hay forages could be a low-cost alternative for producing cheese with a fatty acid profile suitable for human health, which is an aspect of great interest to the food industry.

Chemical-nutritional characteristics and aromatic profile of milk and related dairy products obtained from goats fed with extruded linseed

Objective

This study aimed to evaluate the effect of dietary integration with extruded linseed (EL) on fatty acid (FA) and aromatic profile of goat cheese after 60 (T₆₀) days of ripening.

Methods

Thirty goats were divided in two groups. The control group (CG) was fed with conventional diet, whereas the experimental group (EL+) was fed with conventional diet supplemented with 10% of EL. Milk samples were collected on 30 and 60 days of trial to determinate chemical-nutritional composition and FA profile. At the end of experiment, six cheese-making sessions (3 for each group) were carried out using a pooled milk sample obtained from the 15 goats of each group. At 60 days of ripening, cheeses were analyzed for chemical-nutritional composition, FA and aromatic profile.

Results

An increase in the milk production, protein, fat and lactose were evidenced in the EL+ goats. Conversely, a reduction of somatic cells was observed in the EL+ compared with the CG. However, no variation was observed for urea and casein levels content in milk samples, and no changes in protein and lipid content were found for cheeses in the two experimental groups. Dietary supplementation with EL modified the FA profile of milk. There was a decrease in saturated FAs and an increase in polyunsaturated FAs. Chemical composition of T₆₀ cheese did not differ between the two groups but a different FA profile was observed. In T₆₀ cheese obtained from EL+ milk, an increase in short-chain FA and a decrease in medium and long-chain FA were observed. The EL diet led to cheeses with butanoic acid 2 times higher compared to CG cheeses. Moreover, a greater presence of aldehyde compounds and alcohols were observed in the cheeses of experimental group.

Conclusion

The present study pointed out that EL supplementation may improve the chemical and physical qualities of goat milk and cheeses.

Enhancing Omega-3 Long-Chain Polyunsaturated Fatty Acid Content of Dairy-Derived Foods for Human Consumption

Omega-3 polyunsaturated fatty acids (n-3 PUFA) are termed essential fatty acids because they cannot be synthesized de novo by humans due to the lack of delta-12 and delta-15 desaturase enzymes and must therefore be acquired from the diet. n-3 PUFA include α-linolenic acid (ALA, 18:3n-3), eicosapentaenoic (EPA, 20:5n-3), docosahexaenoic (DHA, 22:6n-3), and the less recognized docosapentaenoic acid (DPA, 22:5n-3). The three long-chain (≥C20) n-3 PUFA (n-3 LC-PUFA), EPA, DHA, and DPA play an important role in human health by reducing the risk of chronic diseases. Up to the present time, seafood, and in particular, fish oil-derived products, have been the richest sources of n-3 LC-PUFA. The human diet generally contains insufficient amounts of these essential FA due largely to the low consumption of seafood. This issue provides opportunities to enrich the content of n-3 PUFA in other common food groups. Milk and milk products have traditionally been a major component of human diets, but are also among some of the poorest sources of n-3 PUFA. Consideration of the high consumption of milk and its processed products worldwide and the human health benefits has led to a large number of studies targeting the enhancement of n-3 PUFA content in dairy products. The main objective of this review was to evaluate the major strategies that have been employed to enhance n-3 PUFA content in dairy products and to unravel potential knowledge gaps for further research on this topic. Nutritional manipulation to date has been the main approach for altering milk fatty acids (FA) in ruminants. However, the main challenge is ruminal biohydrogenation in which dietary PUFA are hydrogenated into monounsaturated FA and/or ultimately, saturated FA, due to rumen microbial activities. The inclusion of oil seed and vegetable oil in dairy animal diets significantly elevates ALA content, while the addition of rumen-protected marine-derived supplements is the most effective way to increase the concentration of EPA, DHA, and DPA in dairy products. In our view, the mechanisms of n-3 LC-PUFA biosynthesis pathway from ALA and the biohydrogenation of individual n-3 LC-PUFA in ruminants need to be better elucidated. Identified knowledge gaps regarding the activities of candidate genes regulating the concentrations of n-3 PUFA and the responses of ruminants to specific lipid supplementation regimes are also critical to a greater understanding of nutrition-genetics interactions driving lipid metabolism.

Effects of dietary concentrate composition and linseed oil supplementation on the milk fatty acid profile of goats

Milk fat composition can be modulated by the inclusion of lipid supplements in ruminant diets. An interaction between the lipid supplement and the forage to concentrate ratio or the type of forage in the rations may affect milk fat composition. However, little is known about the effects of the starch-to-non-forage NDF ratio in the concentrate and lipid supplementation of goat diets. The aim of this work was to determine the role of dietary carbohydrates in goats rations supplemented with linseed oil on animal performance and milk fatty acid (FA) profile. A total of 16 dairy goats were allocated to two simultaneous experiments (two treatments each), in a crossover design with four animals per treatment and two experimental periods of 25 days. In both experiments alfalfa hay was the sole forage and the forage to concentrate ratio (33:67) remained constant. The concentrate in experiment 1 consisted of barley, maize and soybean meal (concentrate rich in starch), whereas it included soybean hulls replacing 25% of barley and 25% maize in experiment 2 (concentrate rich in NDF). As a result, the starch-to-non-forage NDF ratio was 3.1 in experiment 1 and it decreased to 0.8 in experiment 2. Both concentrates were administered either alone or in combination with 30 g/day of linseed oil. Animal performance parameters were not affected by experimental treatments. In contrast, major changes were observed in milk FA profile due to lipid supplementation and the type of concentrate. Linseed oil significantly raised vaccenic and rumenic acids as well as α-linolenic acid and its biohydrogenation intermediates while decreased medium-chain saturated FA (12:0 to 16:0) in milk fat. Milk fat contents of odd and branched-chain FA and trans-10 18:1 responded differently to linseed oil supplementation according to the concentrate fed.

Enhancement of dairy sheep cheese eating quality with increased n-3 long-chain polyunsaturated fatty acids

This study investigated the effect of different plant oil-infused and rumen-protected wheat-based pellets containing eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) on n-3 long-chain (≥C₂₀) polyunsaturated fatty acid (LC-PUFA) content, fatty acid recovery, and sensory attributes of ripened cheese from dairy sheep. During a 10-wk supplementary feeding trial, 60 dairy ewes balanced by live weight, milk yield, parity, and sire breed were randomly divided into 6 groups that were (1) supplemented with on-farm existing commercial wheat-based pellets without oil inclusion (control) or supplemented with wheat-based pellets infused with 50 mL/kg dry matter of oils from (2) canola, (3) rice bran, (4) flaxseed, (5) safflower, and (6) rumen-protected EPA + DHA. Milk samples from each treatment were collected separately by sire breed during the experimental period for cheese processing at the end of the experiment. Twelve batches of cheese (2 batches per treatment) were processed and ripened for 120 d. Three cheese samples were collected and analyzed for each cheese making session (total of 36 cheese samples) at d 120 of ripening. Processed cheese of rumen-protected EPA + DHA had the most efficiency at elevating total n-3 LC-PUFA [total EPA + DHA + docosapentaenoic acid (DPA, 22:5n-3] content compared with the control (0.49 vs. 0.28%). Flaxseed elicited the greatest enhancement of α-linolenic acid (ALA, 18:3n-3), whereas safflower was the most effective diet in enhancing the level of linoleic acid (18:2n-6) in cheese (1.29 vs. 0.71% and 4.8 vs. 3.3%, respectively). Parallel recoveries of n-3 and n-6 LC-PUFA were observed across all treatments except for α-linolenic acid and EPA. Cheese eating sensory traits were also highly affected by oil supplementation, with the highest score of 7.5 in cheese from the rice bran and flaxseed treatments. These results provide new insights into the biological mechanisms and processes that determine dairy ewe milk productivity by underpinning the vital biological role of n-3 LC-PUFA in not only enhancing the healthy composition of cheese from ewes but also translating it into consumer acceptability.

Grape pomace in ewes diet: Effects on meat quality and the fatty acid profile of their suckling lambs

Grape pomace (GP) is an inexpensive natural antioxidant promising as animal feed supplement due to its high content of phenolic compounds. In order to evaluate its effect in lactating ewe rations on meat quality and fat composition of their suckling lambs, 48 Churra ewes were divided into 4 treatments. All animals were fed a ration containing linseed oil (Control) supplemented with Vitamin E or two levels of GP. Lambs were nourished exclusively by suckling until they were slaughtered. Dietary GP did not generate adverse effects on carcasses or lambs meat quality when compared with Control or Vit-E diets. GP improved the water holding capacity of the meat. In addition, lambs meat FA profile was not nutritionally affected with the diets assayed. Hence, the use of GP as a dietary supplement in ewe rations would not have negative effects on meat from suckling lambs.

Probiotic supplementation effects on milk fatty acid profile in ewes

We hypothesised that probiotic feeding would alter the fatty acid (FA) profile of sheep's milk. Sixteen lactating ewes, kept under the same feeding and management practices, were randomly allocated to receive either a control diet or the same diet supplemented with a commercial multi-strain bacterial probiotic. Milk fat FA contents were monitored fortnightly for eight consecutive weeks from 14 d after lambing. Probiotic supplementation increased the contents of butyric and caproic acids in milk fat and had no negative effects on other relevant FA from the human's health point of view (i.e., no differences in branched chain, vaccenic, rumenic and n-3 FA were observed). Under the conditions assayed in the present work, the contents of milk FA originated from rumen microbial metabolism were scantly altered, which suggests that the rumen conversion pathways of FA were not substantially modified by the probiotics.

Production of trans and conjugated fatty acids in dairy ruminants and their putative effects on human health: A review

Consumption of milk and dairy products is important in Western industrialised countries. Fat content is an important constituent contributing to the nutritional quality of milk and dairy products. In order to improve the health of consumers, there is high interest in improving their fatty acid (FA) composition, which depends principally on rumen and mammary metabolism. This paper reviews the lipid metabolism in ruminants, with a particular focus on the production of trans and conjugated linoleic acids (CLA) and conjugated linolenic acids (CLnA) in the rumen. After the lipolysis of dietary lipids, an extensive biohydrogenation of unsaturated FA occurs by rumen bacteria, leading to numerous cis and trans isomers of 18:1, non-conjugated of 18:2, CLA and CLnA. The paper examines the different putative pathways of ruminal biohydrogenation of cis9-18:1, 18:2n-6, 18:3n-3 and long-chain FA and the bacteria implicated. Then mechanisms relative to the de novo mammary synthesis are presented. Ruminant diet is the main factor regulating the content and the composition of milk fat. Effects of nature of forage and lipid supplementation are analysed in cows and small ruminants species. Finally, the paper briefly presents the effects of these FA on animal models and human cell lines. We describe the properties of ruminant trans 18:1, when compared to industrial trans 18:1, CLA and CLnA on human health from meta-analyses of intervention studies and then explore the underlying mechanisms.

Classification of Human Milks Based on Their Trans 18:1 Fatty Acid Profile and Effect of Maternal Diet

BACKGROUND

The diet of breastfeeding women influences the trans fatty acid (TFA) composition of the milk excreted. However, the effects associated to TFA are isomer-dependent and diverse TFA profiles may have different nutritional implications.

OBJECTIVE

The aim of this research was to evaluate whether certain TFA patterns in human milk fat can be used as indicators of TFA intake from different sources.

METHODS

Milk fat from 60 women were examined and classified based on their TFA profile and conjugated linoleic acid (CLA) contents by principal component analysis (PCA).

RESULTS

The PCA of the data allowed the classification of the women into 3 groups depending on milk TFA content and profile. From the 60 subjects, 19 presented a TFA profile characteristic of ruminant products intake, 10 a typical TFA profile of industrial trans fats consumption and 31 a negligible trans content. Superimposed on this, 21 women presented high amounts of docosahexaenoic acid (22:6 n-3) which was related to fish intake.

CONCLUSIONS

The present research overcome problems associated to heterogeneous groups in nutritional experiments by a statistical classification of lactating subjects based on the TFA composition of their milk. This classification could be extrapolated to other nutritional studies dealing with TFA analysis and samples of different nature as biological samples or foodstuffs.

Dietary linseed oil increases trans-10,cis-15 18:2 in caprine milk fat

Trans-10,cis-15 18:2 has been recently detected and characterized in digestive contents and meat and adipose tissue of ruminants, but its presence in milk and dairy products is hardly known. The aim of this study was to quantify trans-10,cis-15 18:2 in milk fat, better understand its metabolic origin, and help to elucidate the mechanisms of rumen biohydrogenation when the diet composition might affect ruminal environment. To address these objectives, 16 dairy goats were allocated to 2 simultaneous experiments (2 groups of goats and 2 treatments in each experiment). Experimental treatments consisted of basal diets with the same forage-to-concentrate ratio (33/67) and 2 starch-to-nonforage neutral detergent fiber (NDF) ratios (0.8 and 3.1), which were supplemented or not with 30 g/d of linseed oil for 25 d in a crossover design. Trans-10,cis-15 18:2 contents in milk fat were determined by gas chromatography fitted with an extremely polar capillary column (SLB-IL111). Levels of trans-10,cis-15 18:2 in individual milk fat samples ranged from 0 to 0.2% of total fatty acids, and its content in milk fat increased 8 fold due to linseed oil supplementation, substantiating the predominant role of α-linolenic acid in its formation. The trans-10,cis-15 18:2 levels in milk fat were similar in both experiments, despite the fact starch-to-nonforage NDF ratio of their respective basal diets greatly differed. In conclusion, trans-10,cis-15 18:2 was clearly related to linseed oil supplementation, and its increase in milk fat was comparable when the basal diets were rich in either nonforage NDF or starch.

Extensive analysis of milk fatty acids in two fat-tailed sheep breeds during lactation

The profile of fatty acids (FA) in the milk fat of two Iranian fat-tailed sheep breeds, Sanjabi and Mehraban, was compared during lactation. Eight ewes of each breed, balanced in parity and carrying one foetus, were selected before parturition. Ewes were kept separated in individual pens during the experimental period, under the same management practices and fed the same diet, in order to eliminate any confounding effects on milk FA profile. Milk was sampled at biweekly intervals up to 10 weeks of lactation, starting 2 weeks after parturition. More than 100 FA were determined in milk fat by means of gas chromatography. The milk fat of Sanjabi ewes contained more cis-9 18:1, that of Mehraban ewes was richer in 10:0, 12:0 and 14:0, and no differences were found for 16:0 and 18:0. No breed differences were found for most branched-chain FA. Mehraban ewes showed a higher presence of vaccenic and rumenic acids in their milk fat. The milk fat of Sanjabi ewes had a lower atherogenicity index and n-6/n-3 FA ratio. The contents of several FA showed time-dependent changes, so breed differences were more apparent or disappeared as lactation progressed. The milk fat of Sanjabi ewes showed a better FA profile from the human health point of view.

Differences in milk fat composition from four old sheep breeds

Abstract. The present short communication presents a comparison between the milk fat composition of four old sheep breeds. All animals were fed the same diet and a milk sample was obtained at the same lactation day and analyzed for its major components, cholesterol concentration and a complete fatty acid profile. From all studied candidates, the Walachian breed (also when compared with modern breeds employed in the dairy industry) was determined to have the most suitable milk composition for human health.

Alternative to decrease cholesterol in sheep milk cheeses

The presence of cholesterol in foods is of nutritional interest because high levels of this molecule in human plasma are associated with an increasing risk of cardiovascular disease and nowadays consumers are demanding healthier products. The goal of this experiment was to diminish the cholesterol content of Manchego, the most popular Spanish cheese manufactured from ewes milk. For this purpose three bulk milks coming from dairy ewe fed with 0 (Control), 3 and 6% of linseed supplement on their diet were used. Nine cheeses (3 per bulk milk) were manufactured and ripened for 3 months. Cholesterol of ewes milk cheese from 6% to 12% linseed supplemented diets decreased by 9.6% and 16.1% respectively, therefore supplying a healthier profile. In a second experiment, different sources of unsaturated fatty acids (rich in oleic, linoleic and α-linolenic acids) were supplemented to dairy ewes and no significant differences were found on cheese cholesterol levels.

Associations between major fatty acids in plant oils fed to dairy goats and C18 isomers in milk fat

Relationships between fatty acids (FAs) in plant oils included in goat diets and milk fat C18 isomers were determined by Principal Factor Analysis (PFA). The three first principal factors (PF1, PF2 and PF3) accounted for 64.5% of the total variation in milk FAs contents. Fatty acids with a double bond at carbons 13, 14, 15 or 16 had high (>0.6) and positive loadings for PF1, trans-4 to trans-8 C18:1 for PF2, whereas trans-10 C18:1, trans-11 C18:1 and cis-9 trans-11 C18:2 showed high and positive loadings for PF3. Pearson's correlations supported that PF1, PF2 and PF3 were related to α-linolenic, oleic and linoleic acid intakes, respectively. Our results show that the quantitatively main FAs in plant lipids supplemented to dairy ruminants are often the main cause of the observed changes in milk C18 isomer contents. However, sometimes the observed changes are caused, or at least are influenced, by other FAs present in lower quantities in the plant lipids. Thus, using mixtures of plant oils with differently unsaturated main FAs could be a way of tailoring milk fat composition to a pre-designed pattern.

Effect of sunflower oil supplementation and milking frequency reduction on sheep milk production and composition

The aim of this study was to investigate the effects of milking frequency reduction and dietary lipid supplementation on intake, BW, and milk yield and composition in high yielding dairy ewes. Ten lactating Assaf ewes were allocated into 2 experimental groups (n=5). Ewes were fed alfalfa hay ad libitum and 34 g·kg(-1) of BW of a concentrate feed with either 0 (Control group) or 43 g of sunflower oil·kg(-1) of DM (SO group). The experiment lasted 63 d and consisted of 3 periods. During Period 1 (from d 1 to 21), ewes were milked twice a day. During Period 2 (from d 22 to 49), ewes were unilaterally milked, so that each gland of each ewe was milked either once or twice daily. During Period 3 (from d 50 to the end of the experiment), both udder halves were again milked twice daily. Intake, BW, and milk composition were controlled weekly and milk production from each half udder was recorded twice a week. Total DM intake, BW, and milk yield in Period 1 were not significantly (P>0.10) affected by dietary treatments. Milk yield tended to be increased in the ewes fed the SO diet in periods 2 (P=0.093) and 3 (P=0.067). Oil supplementation (SO diet) significantly (P<0.05) decreased milk protein and total solids concentrations in the 3 experimental periods and fat content in Period 3, and tended (P=0.077) to decline fat content in Period 2. Lactose content and somatic cell count (SCC) were unaffected (P>0.10) by dietary lipid supplementation in any of the experimental periods. There were no significant (P>0.10) differences between half udders in milk yield and composition in Period 1, and in SCC in any of the experimental periods. Fat and total solids contents were unaffected (P>0.10) by reducing milking frequency. Nevertheless, milk protein content was increased (P<0.001) when glands were milked only once daily whereas milk yield and lactose content were decreased (P=0.001). The interaction between gland and diet was significant for lactose in Period 2, suggesting a greater effect of milking frequency reduction on tight junctions in Control ewes. In fact, the ratio between glands for milk yield was significantly (P<0.05) greater in SO (0.82) than in Control (0.72) ewes. In Period 3, this ratio increased but it was still lower in Control ewes (0.92 vs. 0.78, P<0.05). Thus, milking frequency reduction and SO supplementation seem to have counteracting effects on milk production and composition. Our results suggest that SO-supplemented ewes have a better capacity of adaptation to changes in milking frequency, probably due to processes induced in the mammary gland.

Effects of feeding increasing dietary levels of high oleic or regular sunflower or linseed oil on fatty acid profile of goat milk

In this work, the effects of increasing amounts of 3 plant oils in diets on the fatty acid (FA) profile of goat milk were studied. The study consisted of 3 experiments, one per oil tested (linseed oil, LO; high oleic sunflower oil, HOSFO; and regular sunflower oil, RSFO). The 3 experiments were conducted successively on 12 Malagueña goats, which were assigned at random to 1 of 4 treatments: 0, 30, 48, and 66 (H) g of added oil/d. A basal diet made of alfalfa hay and pelleted concentrate (33:67) was used in all of the experiments. For each animal, milk samples collected after 15 d on treatments were analyzed for fat, protein, lactose, and FA composition, whereas individual milk yield was measured the last 3 d of each experiment. Oil supplementation affected neither dry matter intake nor milk production traits. Increasing the oil supplementation decreased the content of saturated FA (especially 16:0) in milk fat and increased mono- and polyunsaturated FA in a linear manner. Vaccenic acid content linearly increased with the oil supplementation by 370, 217, and 634% to 5.32, 2.66, and 5.09 g/100 g of total FA methyl esters with the H diet in LO, HOSFO, and RSFO experiments, respectively. Rumenic acid content linearly increased with LO and RSFO supplementation by 298 and 354% from 0.53 and 0.41 g/100 g of total FA methyl esters with the 0 g of added oil/d diet. The content of trans-10-18:1 was not affected by LO supplementation but showed an increasing linear trend with HOSFO supplementation and linearly increased with RSFO supplementation. The ratio of n-6 to n-3 polyunsaturated FA in milk fat was decreased by about 70% with the H diet in the LO experiment and it was increased by 54 and 82% with the H diet in the HOSFO and RSFO experiments. In conclusion, LO supplementation in this work seemed to be the most favorable alternative compared with HOSFO or RSFO supplementation.

Influence of feeding Mediterranean food industry by-products and forages to Awassi sheep on physicochemical properties of milk, yoghurt and cheese

Feeding agro-industrial by-products and unconventional forages, rich in potentially anti-nutritional factors, may influence the quality of the raw milk and the dairy products prepared therefrom. The aim of the present study was to determine side-effects on physicochemical properties of milk, yoghurt and cheese of feeding diets where one third were feeds either rich in lipids (tomato pomace and olive cake) or phenols (olive leaves and lentil straw) or electrolytes (Atriplex leaves). The diets, including a control diet, were designed to be isoenergetic and isonitrogenous. They were fed in amounts of 25 kg dry matter/day per head during 50 days to 6×10 multiparous fat-tailed Awassi ewes. Milk samples were analysed for various physicochemical traits and fatty acid composition on days 0, 24, 36 and 48. Three times, milk pooled by group was processed to yoghurt and non-aged farmer-type cheese, which were analysed for their gross and fatty acid composition and texture, and were subjected to sensory evaluation. Feeding olive cake and tomato pomace reduced milk casein, but increased proportions of monounsaturated fatty acids. There were some variations in minerals among test diets but, contrary to expectations, Atriplex did not increase milk sodium. The nutritional composition of yoghurt and cheese was not varied much by the test feeds, except for some changes in fatty acid profile similar to the milk. Yoghurt firmness declined with all test diets, but texture score tended to be lower only for olive cake and leaf diets relative to control. Cheese firmness was increased by feeding the Atriplex leaf and olive cake diets which was also reflected in the texture scores. No off-flavours were reported. Possible reasons for effects on the dairy products are discussed. In conclusion, the feeds investigated had certain effects on the physicochemical properties of dairy products, but these were neither very systematic nor large thus not prohibiting their use in Mediterranean sheep milk production systems.