Ewe Milk Fat Research Articles

The impact of genetic merit on ewe performance and efficiency parameters.

The aim of this study was to investigate the impact of ewe genetic merit on ewe performance and efficiency parameters. The study consisted of three genetic merit groups (New Zealand [NZ], High Irish, and Low Irish) and ran from 2016 to 2019, inclusive. Each genetic merit group contained 30 purebred Suffolk and 30 purebred Texel ewes, which were selected based on their maternal genetic indexes in their country of origin, namely Ireland (€uro-star Replacement index) or New Zealand (New Zealand Maternal worth). Ewe body condition score (BCS), ewe body weight (BW), milk yield, milk composition, dry matter intake (DMI), and efficiency parameters were all analyzed using linear mixed models. Ewe BW was similar across all genetic merit groups at each time point (P > 0.05). In comparison to both High and Low Irish ewes, NZ ewes had a higher BCS at mating, mid-pregnancy, lambing, week 10 post-lambing (PL, P < 0.05). Ewe BW change was similar across genetic merit groups, except between mating and mid-pregnancy where ewe BW loss was greater for NZ ewes than Irish ewes (P < 0.05) and between weeks 6 PL and 10 PL, where NZ ewes gained BW and High and Low Irish ewes lost BW (P < 0.01). Ewe milk yield, milk fat, total solids, and gross energy content were superior for milk produced by NZ ewes at week 6 PL in comparison to milk produced by High Irish and Low Irish ewes (P < 0.01). NZ ewes produced a greater quantity of milk solids/kg of BW at week 6 PL compared with High Irish ewes (P < 0.01), whereas Low Irish ewes did not differ from either NZ or High Irish (P > 0.05). Low Irish ewes had a greater daily DMI than High Irish ewes in late lactation (week 10 PL, P < 0.05) and had a greater DMI/kg of ewe BW compared with the High Irish ewes at the same time point (P < 0.05). NZ ewes weaned a litter BW equivalent to 60.4% of their mating BW, which was more than the Low Irish ewes who weaned 57.1% of the ewe’s BW at mating (P < 0.01), whereas the High Irish ewes did not differ from either the NZ or Low Irish ewes at 59.3% of the ewe’s BW at mating (P > 0.05). This study presents a range of parameters across ewes of high and low genetic merit, demonstrating the ability to achieve gains through selection of animals of high genetic merit. Sheep producers should consider genetic indexes as a tool to assist in the decision-making process of selecting replacement ewes and/or breeding rams, once satisfied the animal is correct, and meeting the breeding objectives of the system.

Determination of Cyclopropenoid Fatty Acids in Ewe Milk Fat by GC-MS after Intravenous Administration of Sterculic Acid.

Cyclopropenoid fatty acids (CPEFA), found in oilseeds from Malvaceae and Sterculiaceae, have been shown to interfere with the endogenous synthesis of several bioactive lipids of dairy fat, such as cis-9, trans-11 18:2 and cis-9 18:1, by inhibiting Δ9-desaturase. No previous study has reported the presence of sterculic acid in animal fat and its incorporation in tissues after its administration, due to the lack of a proper methodology. In the present research, a GC-MS method based on cold base derivatization to fatty acids methylesters was developed to determine CPEFA in ewe milk triglycerides, after infusing sterculic acid (0.5 g/day) to six lactating ewes. An alternative derivatization based on silanyzation followed by GC-MS analysis was also tested, showing its possible applicability when CPEFA are present in the form of free fatty acids. Sterculic acid was detected in ewe milk triglycerides, demonstrating its incorporation from the bloodstream into milk by the mammary gland. The mean transfer rate represented 8.0 ± 1.0% of the daily dose. This study provides, for the first time, the presence of sterculic acid in milk fat, supporting the importance of understanding its occurrence in vivo and encouraging further research to determine whether it can be present in foods, such as dairy products, obtained under practical farming conditions.

Supplementation with eicosapentaenoic and docosahexaenoic acids in late gestation in ewes changes adipose tissue gene expression in the ewe and growth and plasma concentration of ghrelin in the offspring1.

Omega-3 long chain fatty acids have a positive impact on production. When consumed during late gestation, it might have fetal programming effects on the fetus, which will have lifelong impacts on development and production. The objectives of the present study were to evaluate the effect of increasing doses of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the diet of ewes in the last third of gestation on their body weight (BW), subcutaneous adipose tissue relative mRNA abundance of genes associated with adipose tissue metabolism, and growth performance and plasma metabolites and hormones of their offspring during the finishing phase. Ewes (n = 72) were blocked by BW and allotted to pens (8 per treatment) with 3 ewes per pen. Ewes were supplemented with an EPA and DHA source (Strata G113) at concentrations of 0, 1, or 2% of dry matter intake during the last 50 d of gestation. At lambing, all ewes were penned together and offered the same diet. After weaning at 60 d of age, lambs were blocked by BW and sex and fed for 56 d. All lambs were fed the same pellet diet (61.09% ground corn, 24.08% soy hulls, 11.09% soybean meal, 1.48% Ca salt of palm oil, and 2.26% mixed mineral vitamin), and were weighed every 14 d until the end of the trial. Blood samples were collected on the weight sampling days. Dry matter intake and refusals were weighed daily. Data were analyzed as a randomized complete block design with repeated measurements (SAS 9.4). Polynomial contrast (linear-L and quadratic-Q) was used for mean separation. There were no differences in ewe body condition score, milk production, milk fat, or milk protein, but there was a trend for increased (L, P = 0.06) lactose concentration, and also differences in DGAT1 (L, P = 0.04), Δ5-desaturase (Q, P = 0.06) and Δ6-desaturase (Q, P = 0.07), PPARα (Q, P = 0.03), ELOVL2 and 5 (Q, P < 0.07), FABP4 (Q, P = 0.04), FATP1 (Q, P = 0.06), leptin (Q, P = 0.02), and resistin (L, P = 0.05). Feeding pregnant ewes an increased amount of EPA and DHA in late gestation increased final BW (L, P = 0.01), ADG (L, P = 0.04; Q, P = 0.01), DMI (Q, P ≤ 0.01), plasma glucose concentration (L, P = 0.04), and trended to decrease ghrelin concentrations (L, P = 0.07) in offspring during the finishing period. Dam supplementation did not affect G:F, nor plasma NEFA concentration (P ≥ 0.53) of lambs. Therefore, increasing supplementation of EPA and DHA in pregnant ewes has an impact on offspring performance, increasing DMI, ADG, and BW.

Season and reproductive status rather than genetic factors influence change in ewe weight and fat over time. 4. Genetic relationships of ewe weight and fat score with fleece, reproduction and milk traits

The profitability of a sheep enterprise is greatly influenced by the ability of the ewe to produce a lamb annually. This paper examines the between- and within-breed association between the liveweight and fat score of the adult ewe and key fleece, reproduction and milk production traits. The study analysed the performance of 2846 first-cross Merino and Corriedale ewes from the maternal central progeny test (MCPT) over their first three production cycles. Breed (9 sire breeds) and within-breed (91 sires) correlations were calculated from bivariate correlations of adult liveweight and fat score with fleece, reproduction and milk production traits. The mean liveweight and fatness of the breeds were low to moderately negatively correlated with greasy fleece weight (–0.55 and –0.25, respectively) and moderate to strongly positively correlated with fibre diameter (0.88 and 0.41, respectively). However, the within-breed correlations were generally low to negligible. The genetic relationships between ewe fat score and reproductive traits at the breed and within-breed level was generally low to negligible and, in some cases, negative under production conditions where the ewes were well managed and averaged a fat score of 3.5 pre-joining and became too fat across the production cycle. Strong breed correlations between ewe fat score and milk fat concentration (0.88) suggest that selection of fatter sire breeds will lead to increased fat in their progenies’ milk, which was associated with larger lambs. The potential advantages of selecting for more fat to improve the maternal performance of the ewe seem to be limited in enterprises where the production system can easily be adjusted to restrict the influence of temporary and long-term feed deficiencies, as was achieved within the MCPT research flocks.

Effects of olive and fish oil Ca soaps in ewe diets on milk fat and muscle and subcutaneous tissue fatty-acid profiles of suckling lambs

Enhancing healthy fatty acids (FAs) in ewe milk fat and suckling lamb tissues is an important objective in terms of improving the nutritional value of these foods for the consumer. The present study examined the effects of feeding-protected lipid supplements rich in unsaturated FAs on the lipid composition of ewe milk, and subsequently in the muscle and subcutaneous adipose tissues of lambs suckling such milk. Thirty-six pregnant Churra ewes with their new-born lambs were assigned to one of three experimental diets (forage/concentrate ratio 50 : 50), each supplemented with either 3% Ca soap FAs of palm (Control), olive (OLI) or fish (FO) oil. The lambs were nourished exclusively by suckling for the whole experimental period. When the lambs reached 11 kg BW, they were slaughtered and samples were taken from the Longissimus dorsi and subcutaneous fat depots. Although milk production was not affected by lipid supplementation, the FO diet decreased fat content (P<0.001), whereas the OLI milk FA profile resembled that of the Control diet. In contrast, although FO drastically diminished the contents of stearic and oleic acids (P<0.001), all the saturated even-numbered carbon FAs from 6:0 to 14:0 increased (P<0.05). FO also produced the highest levels of c9,t11-18:2 (2.21%) and n-3 FAs, 20:5 n-3 (0.58%), 22:5 n-3 (0.48%) and 22:6 n-3 (0.40%). The high levels of trans-11 18:1 (7.10%) obtained from the FO diet would suggest that Ca soaps only confer partial protection in the rumen. In contrast, the lack of significant differences in trans-10 18:1 levels (P>0.05) and other trans-FAs between Control and FO treatments would indicate that FO treatment does not alter rumen biohydrogenation pathways under the assayed conditions. Changes in dam milk FA composition induced differences in the FA profiles of meat and fat depots of lambs, preferentially incorporated polyunsaturated FAs into the muscle rather than storing them in the adipose tissue. In the intramuscular fat of the FO treatment, all the n-3 FAs reached their highest concentrations: 0.97 (18:3 n-3), 2.72 (20:5 n-3), 2.21 (22:5 n-3) and 1.53% (22:6 n-3). In addition, not only did FO intramuscular fat have the most cis-9, trans-11 18:2 (1.66%) and trans-11 18:1 (3.75%), but also the lowest n-6/n-3 ratio (1.80) and saturated FA content were not affected. Therefore, FO exhibited the best FA profile from a nutritional point of view.

Effects of breed on milk fatty acid profile in dairy ewes, with particular reference to &lt;i&gt;cis-9, trans-11&lt;/i&gt; conjugated linoleic acid

The objective of this study was to determine and compare the fatty acid profile of milk fat, with particular reference to cis-9, trans-11 conjugated linoleic acid (CLA), in two indigenous Romanian sheep breeds (Spanca and Turcana), irrespective of the effects of diet and season. The ewes (n = 25 for each breed) received the same feed (total mixed rations) and were maintained under identical conditions. Four samples were collected from each individual ewe to determine fatty acids (FA), as methyl esters, using gas chromatography. The fatty acid groups, namely saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) acids were examined together with individual acids. Differences have been obtained between the two local breeds for the majority of FA. Fat in the milk of Turcana ewes has a healthier fatty acid profile than that of Spanca breed which has a lower concentration of SFA (60.9 vs. 73.3%) and higher concentrations of MUFA (31.0 vs. 21.0%) and PUFA (8.06 vs. 5.61%, respectively). Compared with the Spanca breed, fat in the milk of Turcana ewes had higher concentrations of trans -11 C18:1, C18:1 n9c, and cis-9 trans-11 CLA (2.67 vs. 1.01%, respectively). Δ 9 -desaturase activity is breed specific; vaccenic acid (trans-11 C18:1) desaturation and its conversion into cis-9, trans-11 CLA were more intense in the Turcana breed ewes. In conclusion, breed has a strong effect on the FA composition of ewe milk fat, and on cis-9, trans-11 CLA, in particular. The results obtained, support the sustainable use of animal genetic resources to improve the milk fat quality of ewes. Keywords : CLA, ewe’s milk, fatty acid profiles, Spanca, Turcana

Quantitative determination of conjugated linoleic acid isomers by silver ion HPLC in ewe milk fat

The aim of this research was to validate a method for the quantification of conjugated linoleic acid (CLA) isomers in the fat of ewe's milk. The isomers in the form of methyl ester (FAME) are separated by silver ion high performance liquid chromatography (Ag+HPLC) and the quantification was based on the measurement of the integrated area under the 231nm peaks, using external CLA reference standards. The response linearity is maintained in a wide range of concentrations and the quantification limit estimated was of 0.005μg/injection for the cis-9,trans-11 and trans-10,cis-12 isomers. Referred to the samples this limit would be 0.008mg/g of fat in the usual working conditions. In the precision assay an RSDr of 2.14% for the isomer cis-9,trans-11 was calculated and for the rest of the CLA isomers varied between 2.08 and 7.5%. The recovery assays were performed adding CLA cis-9,trans-11 triglyceride and the mean recovery was 96%. The method proposed allows the determination of the individual content of different CLA isomers using one single technique, HPLC and supposes saving time and resources.

Effect of the supplementation of dairy sheep diet with incremental amounts of sunflower oil on animal performance and milk fatty acid profile

The aim of this study was to investigate a suitable amount of sunflower oil (SO) inclusion in dairy sheep diet, in order to enhance the milk content of some potentially healthy fatty acids (FA; such as cis-9 trans-11 C18:2 –RA- and trans-11 C18:1 –VA-) without increasing other potentially unhealthy FA (such as trans-10 C18:1) or detrimentally affecting animal performance. Eighty dairy ewes were allocated to 4 treatments: no lipid supplementation (control), supplementation with 17 (SO1), 34 (SO2), or 51 (SO3) g of SO per kg of dry matter, for 28 days. Incremental amounts of dietary SO did not affect milk production nor the milk’s fat, protein and lactose contents. However, the FA profile was substantially modified. Treatment SO3 caused the highest enrichment in VA and RA and decreases in saturated FA, but it also enhanced the accumulation of trans-10 C18:1, which might jeopardise potentially the health-promoting properties of the ewe milk fat.

Effect of the addition of calcium soap to ewes’ diet on fatty acid composition of ewe milk and subcutaneous fat of suckling lambs reared on ewe milk

The aim of this work was to study the effect of the inclusion of calcium soap (CS) in ewes' diet on the fatty acid profile of suckling lambs. Sixty suckling lambs of three breeds (Castellana, Churra and Assaf) were divided into two equal groups. One group was fed with a diet composed of beetroot pulp, alfalfa, barley, corn, soy, cotton and 4% of CS, and the other with a control diet without CS. The fatty acid profiles of the ewe's milk samples collected on the day before slaughter and of the lamb subcutaneous fat collected from the back of the carcasses were analysed. The addition of calcium soap to the ewe's diet did not change the milk fatty acid profile but significantly increased SFA and decreased both the PUFA and MUFA levels of suckling lamb fat. PCA analysis revealed a good separation of the lamb samples according to the diet of the mothers, showing that diet is more important than breed in explaining sample variability.

Evaluation of the morphometric characteristics of ewe milk fat globules, cheese yield and ripening in the intermediate lactation phase

The study was carried out on twenty ewes kept indoors at 25 days post partum. The experiment lasted 60 days, from 40 to 100 days post partum. The animals were homogeneous in terms of parity, lactation phase and feed. The results show that, as the lactation phase progresses, there is a gradual increase in the percentage of fat and a decrease in the average diameter of the fat globules. In particular, before the 55 days of lactation the milk quality and the cheese yield are lower and the weight loss at 10 days of ripening is higher.

Effect of diet supplementation with sunflower oil on milk production, fatty acid profile and ruminal fermentation in lactating dairy ewes

The aim of this research was to enhance the nutritional quality of ewe milk fat by increasing potentially healthy fatty acids (FA) through diet supplementation with unprotected oil rich in linoleic acid, and without detrimental effects on animal performance. Twenty-four ewes were assigned to two high concentrate diets, control or supplemented with 6% sunflower oil (SO), for 4 weeks. No differences between treatments were found in milk production and dry matter intake. Although the SO diet increased milk fat percentage and tended to reduce milk protein concentration, it did not affect milk fat, protein or total solid yield. Most of the modifications in milk FA composition were addressed toward a potentially healthier profile: a decrease in C12:0 to C16:0 and a remarkable increase in the contents of cis-9 trans-11 C18:2 (from 0.94 to 3.60 g/100 g total FA) and trans-11 C18:1 (from 2.23 to 8.61 g/100 g total FA). Furthermore, the levels reached were maintained throughout the period monitored. However, the SO diet increased other trans C18:1 isomer percentages, too. The lack of differences between treatments in the in vitro ruminal fermentation parameters, studied with batch cultures of rumen microorganisms, would indicate no negative effects on ruminal fermentation.

Seasonal variations in fatty acid composition of pasture forage plants and CLA content in ewe milk fat

The relations between fatty acids (FAs) composition of pasture forage plants and the content of conjugated linoleic acid (CLA) as a total content of cis-9, trans-11 + trans-7, cis-9 + trans-8, cis-10 CLA isomers in ewes’ milk fat during natural pasture season (April–September) were investigated. The extracts of ewes’ milk fat samples as well as the pasture samples were analyzed for fatty acid composition by capillary gas chromatography with flame ionization and mass spectrometric detection. α-Linolenic, linoleic, and palmitic acids were predominant in pasture plants, and their contents varied during pasture season. The most abundant and most varied fatty acid compound in pasture plants was α-linolenic acid. Its content significantly decreased from 62% to 39% (of total FA) ( P < 0.001) from May to August, and subsequently it slightly (57%) increased from August to September ( P < 0.05), compared with the beginning of pasture season. Similarly, the content of CLA in ewes’ milk fat decreased from 2.4% in May to 1.3% in August ( P < 0.001), and subsequently it rose to 2.6% in September ( P < 0.001). The α-linolenic/linoleic acid ratio in the pasture sample decreased from 4.36 in May to 1.97 in August ( P < 0.001), and subsequently it increased to 3.14 in September ( P < 0.001); thus, it reached the level approaching to that at the beginning of pasture season. The pasture seasonal variations in the ratio were directly proportional to the corresponding content of CLA and indirectly proportional to the ratio in ewes’ milk fat. The results suggest that the seasonal variations in CLA content in ewes’ milk fat are related primarily to the seasonal variation in α-linolenic acid content in grass lipids.

Factors affecting ewe's milk fat and protein content and relationships between milk yield and milk components

Test-day records of purebred Tsigai, Improved Valachian and Lacaune ewes were used to analyse the effect of environmental factors on milk fat and protein content. There were 121 424 and 121 158 measurements of fat and protein content for Tsigai, 247 742 and 247 606 measurements of fat and protein content for Improved Valachian and 2 194 measurements of fat and protein content for Lacaune ewes lambing between 1995 and 2005. Overall means and standard deviations for fat and protein content were 7.77 &amp;plusmn; 1.606% and 5.94 &amp;plusmn; 0.690% for Tsigai, 7.48 &amp;plusmn; 1.446% and 5.82 &amp;plusmn; 0.620% for Improved Valachian, and 6.97 &amp;plusmn; 1.514% and 5.62 &amp;plusmn; 0.692% for Lacaune. For fat content, analyses showed a highly significant (&lt;i&gt;P&lt;/i&gt; &lt; 0.01) effect of flock-test day and a highly significant (&lt;i&gt;P&lt;/i&gt; &lt; 0.01) or significant (&lt;i&gt;P&lt;/i&gt; &lt; 0.05) effect of the month of lambing, with the only exception of the month of lambing in Lacaune. The effect of litter size was highly significant (&lt;i&gt;P&lt;/i&gt; &lt; 0.01) or significant (&lt;i&gt;P&lt;/i&gt; &lt; 0.05) in Improved Valachian and Lacaune. For protein content, analyses showed a highly significant (&lt;i&gt;P&lt;/i&gt; &lt; 0.01) effect of flock-test day and a highly significant (&lt;i&gt;P&lt;/i&gt; &lt; 0.01) or significant (&lt;i&gt;P&lt;/i&gt; &lt; 0.05) effect of the month of lambing. The effect of litter size was highly significant (&lt;i&gt;P&lt;/i&gt; &lt; 0.01) in Tsigai and Improved Valachian. Covariates of days in milk which modelled the shape of lactation curves were insignificant, except for Improved Valachian fat content (Ali-Schaeffer regression adopted for sheep). The model explained about 50% of fat and protein variation in the breeds, with coefficients of determination between 0.517 and 0.587 for fat content and between 0.495 and 0.527 for protein content. Fat and protein content were almost equally correlated with milk yield in the three breeds. Lactation curves were constructed on the basis of solutions of a statistical model employed in the analyses.

Conjugated linoleic acid in ewe milk fat

Ewe milk fat from five different herds was studied to determine the content of conjugated linoleic acid (CLA) isomers. Research was carried out by combining gas chromatography-mass spectrometry (GC-MS) of fatty acid methyl esters (FAME) and 4,4-dimethyloxazolyne derivatives (DMOX) with silver ion-high performance liquid chromatography (Ag+-HPLC). Reconstructed mass spectral profiles of CLA characteristic ions from DMOX were used to identify positional isomers and Ag+-HPLC to quantify them. Total CLA content varied from 0.57 to 0.97 g/100 g of total fatty acids. FAME and DMOX were separated into a complex mixture of minor isomers and major rumenic acid (9-cis 11-trans C18:2) by GC-MS using a 100-m polar capillary column. Rumenic acid would represent more than 75% of total CLA. 11-trans 13-trans, 11-13 cis/trans plus trans/cis and 7-9 cis/trans plus trans/cis were the main CLA isomers after rumenic acid. Minor amounts of 8-10 and 10-12 C18:2 isomers were also found. Although most of the isomers were present in each herd's milk, differences in content were observed for some CLA species.

Effects of supplementing with calcium salts of palm oil fatty acids or hydrogenated tallow on ewe milk production and twin lamb growth.

Two experiments were conducted with Polypay ewes nursing twin lambs to evaluate the effects of supplementing fat (calcium salts of palm oil fatty acids or hydrogenated tallow) on ewe lactation. In Exp. 1, ewes were fed a 52% concentrate:48% hay-based diet (as-fed basis) consisting of alfalfa hay (n = 4), endophyte-free fescue hay (n = 4), or fescue hay with 3.7% fatty acids (n = 4) from d 4 to 56 of lactation. In Exp. 2, ewes were fed similar diets that had endophyte-free fescue hay (n = 6), fescue hay with 3.7% fatty acids (n = 5), or fescue hay with 3.1% tallow (n = 6) from d 14 before lambing until d 57 of lactation. Diet formulations with supplemental fat were more nutrient dense, and treatments were fed to meet ewe nutrient requirements; this caused diets with added fat to be offered at 10 and 17% lower rates than unsupplemented diets in Exp. 1 and 2, respectively. Lambs were maintained to consume only ewe milk. Ewe milk production and composition were determined using a portable milking machine following a 3-h separation from lambs. In Exp. 1, milk fat content was increased (P < 0.01) when ewes consumed fescue hay with fatty acids vs. the fescue hay diet (11.4 vs. 8.3%). Ewes fed fescue hay with fatty acids lost the most (P < 0.05) weight over lactation (-8.6 kg) compared with ewes fed the alfalfa hay (-2.4 kg) and fescue hay (-3.8 kg) diets. Other milk measures, lamb gain, and production efficiencies were not changed. In Exp. 2, ewes supplemented with fatty acids produced more (P < 0.05) milk fat than those fed tallow (290 vs. 210 g/d). The proportion of synthesized milk fat 14:0 was decreased (P < 0.01), but the percentage of incorporated 16:0 increased (P < 0.05) when fatty acids were fed. Dietary fat digestibility by ewes was increased (P < 0.01) by fatty acid supplementation but decreased (P < 0.01) when tallow was added. Although ewe weight measures were not changed in Exp. 2, twin lamb gain per ewe organic matter intake was most efficient (P < 0.05) when ewes were supplemented with fatty acids. Results suggest that feeding hydrogenated tallow decreased nutrient availability for ewe milk fat production. A complete diet based on endophyte-free fescue hay can replace a traditional alfalfa hay diet, whereas supplementing with the calcium salts of palm oil fatty acids may be more feasible when energy is limiting during ewe lactation.

Quantitative characterization of unsaturated and trans fatty acids in ewe’s milk fat

Ewe's milk fat obtained from the milk of five different herds were studied to character- ize main and minor fatty acids using a combination of gas chromatography and mass spectrometry. In order to assess monounsatured trans fatty acids content, fatty acid methyl esters (FAME) were fractionated by silver ion thin-layer chromatography prior to gas chromatography analysis. Trans fatty acids (TFA), including conjugated linoleic acid, represented 4.9% of the total FAME; most of them belonged to C18:1 trans isomers (2.9%) with a small range of variation (2.5-3.2%). The dis- tribution profile of trans-C18:1 molecules indicated that more than half were trans-11, whereas the proportion of potentially unhealthy compounds (trans-10 and trans-9 C18:1) was less than 10%. Mean trans-C16:1 content was 0.25% of total FAME. The sum of the different trans-C18:2 isomers (excluding conjugated linoleic acid) was 0.88% and C18:3 trans isomers represented 0.16%. Ewe's milk / fatty acid / trans fatty acid

Quantitative characterization of phospholipids in milk fat via 31P NMR using a monophasic solvent mixture.

The phospholipids (PL) occurring in both ewe and cow milk fat globule membrane were identified and quantitatively determined using 31P NMR spectroscopy with inverse gated decoupled sequences, which allowed a rigorous quantitative analysis. A strict relation between amount and distribution of PL and type of feeding was found. The method was calibrated over a mixture of PL standards. A recently introduced solvent constituted by a monophasic dimethylformamide/triethylamine/guanidinium hydrochloride solvent mixture was used. Compared to the traditional chloroform/methanol/water-EDTA solvent, the new solvent mixture shows very similar accuracy and precision from a quantitative point of view. The monophasic solvent overcomes the partition problems related to a biphasic system, and slightly enlarges the range of 31P NMR chemical shifts, thus improving the resolution. In addition, the new solvent apparently displays a lower chemical shift dependence on the various PL concentrations. The limit of the method is mainly determined by the formation of adducts between triethylamine and some PL, namely, PE, monomethylphosphatidylethanolamine, phosphatidylethanolamine plasmalogens, and some lyso-PL. However, the new 31P NMR signals arising from these adducts could be easily quantified in the determination of PE.

TAG composition of ewe's milk fat. Detection of foreign fats

AbstractThe TAG composition of 45 samples of ewe's milk, collected throughout the year from five Spanish breeds, was analyzed according to their carbon number by using short capillary column GC. The TAG content had a bimodal distribution with maxima at C38 (12.8%) and C52 (8.4%). The TAG composition did not vary significantly with respect to the time of year of sampling but was affected by the breed. Multiple regression equations based on TAG content are proposed to detect foreign fats in ewe's milk fat. Analysis of known mixtures of lard, palm oil, and cow's milk fat with ewe's milk fat have experimentally confirmed the accuracy of the equations.

Study of individual trans- and cis-16:1 isomers in cow, goat, and ewe cheese fats by gas-liquid chromatography with emphasis on the trans-delta3 isomer.

Low-temperature gas-liquid chromatography (GLC) was applied to study the distribution profiles of isomeric trans- and cis-hexadecenoic acids in ruminant (cow, goat, and ewe) milk fat after their fractionation by argentation thin-layer chromatography (Ag-TLC). The fat was extracted from cheeses (12 samples of each species), the most common foods made with goat and ewe milks. The predominant trans-16:1 isomer is palmitelaidic acid (the delta9 isomer), but it does not exceed one-third of the total group, which itself represents 0.17% (cow), 0.16% (goat), and 0.26% (ewe) of the total fatty acids. The trans-delta3 16:1 isomer, which is reported for the first time in ruminant lipids and which likely comes from the animals' feed, is present at a level of ca. 10% of the trans-16:1 acid group. Otherwise, all isomers with their ethylenic bond between positions delta4 and delta14 are observed in the three species studied, roughly showing the same relative distribution pattern. Quantitatively, the trans-16:1 isomers only represent ca. 5% of the sum of the trans-16:1 plus trans-18:1 isomers, and they appear of little importance in comparison. It is inferred from this and recent studies that some previously reported data that were established for consumption assessments dealt in fact mainly with iso-17:0 acid, which was confused with (and added to) trans-delta9 (palmitelaidic) acid; consequently, these results were large over-estimates. Regarding the cis-16:1 acids, the delta9 isomer is the prominent constituent as expected, but the second-most important isomer is the delta13 isomer. It does not appear that trans-16:1 isomers are from ruminant milk fats of great nutritional importance as compared with trans-18:1 isomeric acids. As for trans18:1 isomers, the combination Ag-TLC/GLC is a necessary procedure to quantitate trans-16:1 acids accurately and reliably. Ag-TLC allows removal of interfering branched 17:0 acids and cis-16:1 acids, and low-temperature GLC permits an accurate measurement of all individual isomers most of which with baseline resolution.

Triglyceride composition of ewe, cow, and goat milk fat

AbstractThe separation and identification of the components in milk fat, which are mainly triglycerides, is a challenge due to its complex composition. A reverse‐phase high‐performance liquid chromatography (HPLC) method with gradient elution and light‐scattering detection is described in this paper for the triglyceride analysis in ewes’ milk fat. Triglyceride identification was carried out by combining HPLC, gas‐liquid chromatography (GLC), and the calculated equivalent carbon numbers of several triglyceride standards. Quantitation of partially resolved peaks in the HPLC chromatogram was accomplished by applying a peak deconvolution program. Forty‐four fatty acids were identified by GLC analysis, but only 19 were used for the following prediction of triglyceride molecular species; 181 triglycerides were identified, some of which were grouped at the same peak and needed application of the deconvolution program. Consequently, coefficients of variation were close to or lower than 5%. Moreover, the triglyceride composition of ewe, cow, and goat milk fat were compared by using these methods. These results show that ewe milk fat is richer in short‐ and medium‐chain triglycerides, and cow milk fat is richer in long‐chain and unsaturated triglycerides.