Human milk fat is specially tailored to supply the developing infant with adequate and balanced nutrients. The present study aimed to quantify the composition of fatty acids, tocopherols and carotenoids in human milk, with special emphasis on the lactational changes. Colostrum, transitional and mature milk samples were collected longitudinally from the same forty-two healthy, well-nourished Chinese mothers. Fatty acids were quantified by GC with carotenoids (carotenes and xanthophylls) and tocopherols (α-, γ-tocopherol) determined by HPLC. Total fatty acid (TFA) content increased from 15·09 g/l in colostrum to 32·57 g/l in mature milk with the percentages of DHA and arachidonic acid (ARA) decreased. The ratio of n-6:n-3 PUFA and ARA:DHA remained constant during lactation at about 11:1 and 1·3:1, respectively. Both α-tocopherol and γ-tocopherol decreased over lactation with the ratio of α-:γ-tocopherol declined significantly from 7·21:1 to 4·21:1 (P < 0·001). Carotenoids all dropped from colostrum to mature milk as the less polar carotenes dropped by 88·67 %, while xanthophylls only dropped by 35·92 %. Lutein was predominated in both transitional and mature milk carotenoids (51·64–52·49 %), while colostrum carotenoids were mainly composed of lycopene (32·83 %) and β-carotene (30·78 %). The concentrations of tocopherols and xanthophylls but not carotenes were positively associated with TFA content in milk. These results suggested that colostrum and mature milk contained divergent lipid profiles and selective transfer mechanisms related to polarity might be involved. The present outcomes provide new insights for future breast-feeding studies, which also add in scientific evidences for the design of both initial and follow-on infant formulas.

This study was undertaken to provide a thorough analysis of the neutral lipid (NL) and polar lipid (PL) fractions of horse meat that included the content and distribution of acyl and alkenyl moieties in foals under different rearing conditions. Two groups of crossbred horses were studied; the first group was selected from suckling foals produced under grazing conditions and slaughtered at 4 months of age (n=8), and the second group was selected from concentrate-finished foals and slaughtered at 12 months of age (n=7). There were significant differences related to the age and feeding practices of foals which affected the intramuscular (IM) fat content and the fatty acid (FA) composition of NL and PL fractions. Samples from suckling foals were leaner and provided the highest content of methylation products from the plasmalogenic lipids, and total and n-3 polyunsaturated fatty acid (PUFA). By contrast, the meat from concentrate-finished foals had a higher IM fat level resulting in a greater accumulation of 16:0 and total monounsaturated FAs in the NL fraction, whereas the muscle PL fraction retained a similar FA composition between both groups. Linolenic acid was preferentially deposited in the NL fraction, but linoleic acid and the long-chain n-3 and n-6 PUFAs were incorporated into the PL fraction where they served as cell membrane constituents and in eicosanoid formation.

Indirect comparisons from studies in vivo have suggested that caprine mammary tissue is less sensitive than bovine mammary tissue to the anti-lipogenic effect of long-chain fatty acids (LCFA), including specific rumen biohydrogenation (RBH) intermediates of polyunsaturated fatty acids (PUFA). Our objective was to investigate the effects on lipogenesis of 18-carbon LCFA differing in the degree of unsaturation and/or double bond conformation using cultured slices of bovine and caprine mammary tissues. Mammary tissues were collected from five multiparous Holstein × Normande cows and six multiparous Alpine goats in mid lactation. The expression of genes involved in milk component synthesis was measured in tissues collected at slaughter and after slice preparation: FASN, SCD1, CD36, SREBF1 and PPARG1 mRNA levels were higher in bovine than caprine samples, whereas the opposite was observed for CSN2 mRNA levels. Bovine and caprine mammary slices were incubated for 20 h in a medium with BSA (control), cis-9-18 : 1, 18 : 2n-6, 18 : 3n-3, cis-9, trans-11-CLA, or trans-10, cis-12-CLA (the latter at 3 increasing concentrations: C1 (0·11 mm), C2 (0·16 mm), C3 (0·37 mm)). Lipogenesis was estimated by measuring the incorporation of 14C-acetate into total lipid. Significant differences of individual LCFA (P < 0·05) were observed between species: bovine tissue showed a decrease in total lipogenesis with 18 : 2n-6, 18 : 3n-3, trans-10,cis-12-CLA (C2 and C3) while caprine tissue showed an increase after treatment with 18 : 3n-3, cis-9, trans-11-CLA or trans-10, cis-12-CLA (C3). These results were not related to the mRNA abundance of our set of genes in the mammary slices after incubation. In conclusion, this study demonstrates that caprine mammary slices reacted differently from bovine mammary slices to the anti-lipogenic activity of specific LCFA and suggests that regulation of lipogenesis via other genes and/or at protein level and enzyme activity may be involved.

Long-chain fatty acids have been shown to suppress appetite and reduce energy intake (EI) by stimulating the release of gastrointestinal hormones such as cholecystokinin (CCK). The effect of NEFA acyl chain length on these parameters is not comprehensively understood. An in vitro screen tested the capacity of individual NEFA (C12 to C22) to trigger CCK release. There was a gradient in CCK release with increasing chain length. DHA (C22) stimulated significantly (P < 0·01) more CCK release than all other NEFA tested. Subsequently, we conducted a randomised, controlled, crossover intervention study using healthy males (n 18). The effects of no treatment (NT) and oral doses of emulsified DHA-rich (DHA) and oleic acid (OA)-rich oils were compared using 24 h EI as the primary endpoint. Participants reported significantly (P = 0·039) lower total daily EI (29 % reduction) with DHA compared to NT. There were no differences between DHA compared to OA and OA compared to NT. There was no between-treatment difference in the time to, or EI of, the first post-intervention eating occasion. It is concluded that NEFA stimulate CCK release in a chain length-dependent manner up to C22. These effects may be extended to the in vivo setting, as a DHA-based emulsion significantly reduced short-term EI.

To investigate the potential use of n-alkanes (alkanes), long-chain alcohols (alcohols) and long-chain fatty acids (acids) for estimating the diet composition of sheep, in a feeding trial. A total of 18 sheep were assigned randomly to three different diets (diet A, diet B and diet C) containing up to eight herbage species (Leymus chinensis, Leymus dasystachys, Elymus sibiricum, Chenopodium album, Puccinellia chinampoensis, Medicago sativa, Saussurea sinuata and Bromus inermis). Faecal recoveries of alkanes, alcohols and acids were determined, and diet compositions were estimated using different combinations of alkanes, alcohols and acids. The faecal concentrations of individual alkanes, alcohols and acids were corrected using the mean recovery of the dietary treatment that the respective animal belonged to (diet recovery), or the mean recovery across all dietary treatments (general recovery). In general, diets did not affect the faecal recovery values for alkanes, alcohols and acids, and no difference in accuracy was found between diet composition estimates based on dietary recovery and general recovery. The accuracy of diet composition estimates declined as the number of dietary components increased from four to eight herbage species (P < 0.001). Better (P < 0.05) estimates of diet composition were obtained with the combinations of two or three marker types instead of alkanes alone. Moreover, results showed that excluding minor diet components from the calculations decreased (P < 0.05) the accuracy of diet composition estimates, whereas including extra non-grazed herbage species did not reduce (P > 0.05) the quality of diet composition estimates. These results confirmed the usefulness of alkanes, alcohols and acids as markers for determining complex diet composition of sheep. However, a negative impact on the accuracy of diet composition estimates, caused by missing minor diet components from the calculation of diet composition, could happen when plant wax markers are used to estimate the diet composition of free-ranging animals.

The limitations of the alkane technique in estimating the diet components of herbivores call for the introduction of new diet composition markers. Recently, long-chain alcohols (alcohols) and long-chain fatty acids (acids) have received the most attention and show great potential, when combined with alkanes, to estimate composition of complex diets. In the current study, faecal recoveries of alcohols and acids were determined in sheep in four different live weight groups fed three herbage species, either Leymus chinensis, L. dasystachys or Elymus sibiricum. Analysis of variance (ANOVA) was used to examine the effects of herbage species and live weight of sheep on faecal recoveries of individual alcohols and acids. Further, an indoor experiment with six sheep fed a diet of equal proportions, on dry matter (DM) basis, of three herbages was performed, allowing to assess the accuracy of alcohols and/or acids in combination with alkanes, to estimate diet composition. A one-sample t-test was carried out to test the accuracy of these estimates. Results of the first experiment indicated that the faecal recoveries of alcohols and acids were significantly affected by herbage species (P < 0.05). While the effects were significant or near significant for the faecal recoveries of some alcohols (C24-ol, C30-ol and C26-ol) (P ⩽ 0.05), no effect of live weight on faecal recoveries of acids was observed (P > 0.05). Therefore, adjustments based on diet-specific faecal recoveries might improve diet composition estimates. This was illustrated by the results of the second experiment. The diet composition estimated from alcohols or all combinations of alcohols with other marker types, after diet-specific correction of faecal recoveries, did not significantly differ from the actual composition (P > 0.05). However, using acids as additional markers resulted in poorer diet composition estimates. This study confirmed the utility of alcohols, combined with alkanes, as markers to estimate composition of complex diets. Although corrections based on mean faecal recoveries, average over animals and diets, resulted in some accuracy loss, results were still satisfactory and better than without recovery correction.