No abstract

Several methods are available to extract total lipid and methylate fatty acids from a range of samples including red blood cells (RBC). Fatty acid analysis of human RBC can be undertaken using a two-step extraction and methylation or a combined one-step extraction and methylation procedure. The lipid composition of sheep RBC differs significantly from that of humans and may affect their extraction. The purpose of the current study was to examine the efficiency of extraction of lipid and detection of fatty acids from sheep RBC using a one-step procedure. Fatty acids were analysed using a one-step extraction and methylation procedure using methanol:toluene and acetyl chloride in comparison with a two-step procedure involving extraction of lipid using chloroform:methanol and separate methylation. Concentrations of saturated fatty acids including C16:0 and C18:0 were significantly higher (42.6 and 33.9 % respectively) following extraction using the one-step procedure compared with the two-step procedure. However, concentrations of some polyunsaturated fatty acids, including C20:5n-3 and C22:6n-3 were not significantly different between either procedure. The improved detection of fatty acids may be related to the ability of different solvents to extract different lipid fractions. The differential extraction of lipids and detection of fatty acids from sheep RBC may have important implications in studies examining the effect of dietary treatment on the possible health benefits of fatty acids.

Diets high in omega-6 (n-6) fatty acids in mice have been associated with a higher proportion of female offspring, however, the specific effects of dietary fatty acids on the sex ratio of sheep has not previously been reported. The aim of the present study was to determine whether feeding ewes a diet differing in n-6 for 6 weeks before and 3 weeks following conception would increase the proportion of female lambs born. Merino × Border Leicester ewes (n = 296) were allocated to receive either a diet high in n-6 (70% oat grain, 8% cottonseed meal, High n-6 diet) or, a control diet low in n-6 (88% legume silage, Low n-6 diet), for 42 or 53 days before and 17 days after conception, using a stratified block randomisation procedure based on body condition score and liveweight. Following synchronisation, oestrus was detected daily during natural mating with rams. After mating, all ewes grazed improved pastures as one group until lambing. Plasma n-6 concentrations were greater (P < 0.001), the time to parturition was shorter (P < 0.001) and the proportion of female offspring was higher (58.2 vs 43.5%, P = 0.010) when ewes were fed the High n-6 diet compared with the Low n-6 diet. Further research is required to determine whether the observed differences in sex ratio were due to specific alterations in n-6 fatty acids, or other differences in the diets not specifically related to n-6 such as saturated fat or energy density.

Diets high in omega-6 polyunsaturated fatty acids (n-6) are associated with increased prostaglandin F(2α) (PGF(2α)) synthesis in cattle, however, the specific effects on the potential prostaglandin response to an oxytocin challenge in sheep have not been reported. The aim of the current study was to determine whether oxytocin-stimulated PGF(2α) was significantly increased when ewes were fed a diet high in n-6 compared with a control diet low in n-6. Merino x Border Leicester ewes (n = 30) received one of two dietary treatments, either high in n-6 (70 % oat grain) or low in n-6 (control diet, 100 % cereal/legume silage). Ewes consumed the diets for 44 days prior to two consecutive oxytocin challenges. Plasma n-6 and PGF(2α) metabolite (PGFM) concentrations following oxytocin challenge were greater (P < 0.05) when ewes were fed a diet high in n-6 compared with the control diet. A higher availability of n-6 may have lead to an increased in vivo synthesis of PGF(2α), however, further research is required to determine the exact mechanisms involved.