Influence Of Dietary Fat Source Research Articles

Calorie restriction and calorie dilution have different impacts on body fat, metabolism, behavior, and hypothalamic gene expression.

Caloric restriction is a robust intervention to increase lifespan. Giving less food (calorie restriction [CR]) or allowing free access to a diluted diet with indigestible components (calorie dilution [CD]) are two methods to impose restriction. CD does not generate the same lifespan effect as CR. We compare responses of C57BL/6 mice with equivalent levels of CR and CD. The two groups have different responses in fat loss, circulating hormones, and metabolic rate. CR mice are hungrier, as assessed by behavioral assays. Although gene expression of Npy, Agrp, and Pomc do not differ between CR and CD groups, CR mice had a distinctive hypothalamic gene-expression profile with many genes related to starvation upregulated relative to CD. While both result in lower calorie intake, CR and CD are not equivalent procedures. Increased hunger under CR supports the hypothesis that hunger signaling is a key process mediating the benefits of CR.

Influence of dietary fat sources and conjugated fatty acid on egg quality, yolk cholesterol, and yolk fatty acid composition of laying hens

ABSTRACT This study was conducted to investigate the effects of dietary fats (tallow [TO] or linseed oil [LO]) or conjugated linoleic acid (CLA), singly or in combination, on laying performance, yolk lipids, and fatty acid composition of egg yolks. Three hundred 50-week-old laying hens were given one of five diets containing 2% TO; 1% TO + 1% CLA (TO/CLA); 2% LO; 1% LO + 1% CLA (LO/CLA); and 2% CLA (CLA). Laying performance, egg lipids, and serum parameters were not [...]

Age-dependent alterations of glucose clearance and homeostasis are temporally separated and modulated by dietary fat

Diet- and age-dependent changes in glucose regulation in mice occur, but the temporal development, mechanisms and influence of dietary fat source remain to be defined.We followed metabolic changes in three groups of mice including a low-fat diet (LFD) reference group and two high-fat, high-sucrose diets based on either fish oil (FOD) or soybean oil (SOD), rich in ω3- and ω6-polyunsaturated fatty acids, respectively, to closely monitor the age-dependent development in glucose regulation in both obese (SOD-fed) and lean (LFD- and FOD-fed) mice. We assessed glucose homeostasis and glucose clearance at week 8, 12, 16, 24, 31, and 39 and performed an insulin tolerance test at week 40. We further analyzed correlations between the gut microbiota and key metabolic parameters.Interestingly, alterations in glucose homeostasis and glucose clearance were temporally separated, while 16S ribosomal gene amplicon sequencing revealed that gut microbial alterations formed correlation clusters with fat mass and either glucose homeostasis or glucose clearance, but rarely both. Importantly, effective glucose clearance was maintained in FOD- and even increased in LFD-fed mice, whereas SOD-fed mice rapidly developed impaired glucose clearance followed by a gradual improvement from week 8 to week 39. All groups had similar responses to insulin 40 weeks post diet initiation despite severe nonalcoholic steatohepatitis in SOD-fed mice.We conclude that age-related alterations in glucose regulation may occur in both lean and obese mice and are modulated by dietary fat as indicated by the sustained metabolic homeostasis observed in mice fed ω3-polyunsaturated fatty acids.

Influence of dietary fat source on sow and litter performance, colostrum and milk fatty acid profile in late gestation and lactation.

The objective of this study was to investigate the effects of dietary supplementation with various fat sources (3.8-3.9% of diet) during late pregnancy and lactation on the reproductive performance, fatty acids profile in colostrum, milk and serum of sow progeny. A total of 80 multiparous sows were randomly fed a control (adding no oil), palm oil (PO), fish oil (FO) or soybean oil (SO) supplemented diet from 90days of pregnancy to weaning. Supplementation of FO increased litter size of weak piglets, compared with the control-fed sows (P<0.05). Dietary FO and SO supplementation, enhanced the weaning survival rate, litter weaning weight, litter weight gain and fat content in milk (P<0.05). The highest immunoglobulin (Ig)G and IgM levels in colostrum and milk were observed in the FO group (P<0.05). Meanwhile, the highest concentration of C22:5 (n-3) and C22:6 (n-3) in colostrum, milk and piglet serum was observed in the FO group (P<0.05). Taken together, dietary inclusion of FO or SO improved growth performance of nursing piglets by increasing milk fat output, and FO consumption by sows might benefit the piglets via increasing n-3 polyunsaturated fatty acid availability and immunoglobulins (IgG and IgM) secretion.

Influence of dietary fat source and feeding duration on finishing pig growth performance, carcass composition, and fat quality.

A total of 160 finishing pigs (PIC 327 × 1050; initially 45.6 kg) were used in an 84-d experiment to evaluate the effects of dietary fat source and feeding duration on growth performance, carcass characteristics, and carcass fat quality. There were 2 pigs per pen with 8 pens per treatment. The 10 dietary treatments were a corn-soybean meal control diet with no added fat and a 3 × 3 factorial with main effects of fat source (4% tallow, 4% soybean oil, or a blend of 2% tallow and 2% soybean oil) and feeding duration (d 0 to 42, 42 to 84, or 0 to 84). The control corn-soybean meal diet was fed in place of added fat diets when needed for duration treatment purposes. On d 0, 1 pig was identified in each pen and fat biopsy samples of the back, belly, and jowl were collected on d 0, 41, and 81 for fatty acid analysis. At the conclusion of the study, all pigs were harvested, carcass characteristics were determined, and back, belly, and jowl fat samples were collected for analysis. Overall (d 0 to 84), there were no differences among pigs fed the different fat sources for growth and carcass characteristics; however, pigs fed diets with added fat for the entire study had improved ( = 0.036) G:F compared with pigs fed the control diet without added fat. Pigs fed supplemental fat throughout the entire study also had improved ( < 0.05) ADG and G:F as well as heavier d-84 BW ( = 0.006) compared with pigs fed additional fat during only 1 period. Adding fat for the entire study increased ( = 0.032) backfat and tended to reduce ( = 0.079) the fat free lean index compared with pigs fed the control diet without added fat. Added fat also increased ( < 0.05) the iodine value (IV) when compared with pigs fed the control diet. Increasing the feeding duration of soybean oil lowered MUFA and increased PUFA concentrations for all fat depots, whereas these values remained relatively unchanged by the addition of tallow (duration × fat source interactions, < 0.05). Our study failed to show any feeding period × fat source interactions ( < 0.05) in fatty acid composition or IV for jowl fat, whereas this interaction occurred for belly fat and backfat, which would indicate a longer turnover rate for jowl fat. In conclusion, feeding additional fat improved ADG and G:F; however, feeding soybean oil for an increased duration, either alone or in combination with tallow, negatively affected the fatty acid composition and IV of different fat depots.

Influence of dietary fat sources and lysolecithin on growth performance, visceral organ size, and histological intestinal alteration in broiler chickens

The aim of this study was to investigate the influence of dietary fat sources and lysolecithin on growth performance, visceral organ size, and histological intestinal alterations in broiler chickens. Ninety-six 7-d-old male broiler chickens were assigned to 8 treatments in a 2×4 factorial arrangement of treatments with 2 levels of lysolecithin (0 and 145mg/kg) and 4 different fat sources [poultry fat (PF), yellow grease from Kagoshima (YG1), yellow grease from Kashima (YG2), and yellow grease from Hachinohe (YG3)]. Each treatment had 4 replicates of 3 broiler chickens per cage until 49d of age. There was no difference in BW gain due to fat sources, lysolecithin, or lysolecithin×fat source interaction throughout the experiment. By feeding lysolecithin, feed efficiency increased (P<0.05) during the growth period of 7 to 21d of age, and the weights of the duodenum, ileum, and total intestine decreased (P<0.05). Intestinal villus height, villus area, and cell area were not different among treatment groups, except that ileal villus height tended to decrease and ileal cell area tended to increase (P=0.077) by feeding lysolecithin. Increased duodenal cell mitosis and decreased jejunal tunica muscularis thickness were observed (P<0.05) by feeding lysolecithin. Furthermore, on the villus apical surface, more protuberated cells, cell clusters, and deeper cells at the sites of recently exfoliated cells were observed by feeding lysolecithin. However, the protuberant cells were not different among treatment groups. The Integrated Fluorescence Density Values of Anti-Cluster of Differentiation 36 reaction in the jejunum were significantly greater in the lysolecithin-fed groups, except YG2. These results indicate that feeding lysolecithin improves feed efficiency during 7 to 21d of age regardless of the fat type, and causes epithelial hypertrophy.

The Influence of Dietary Fat Source on Life Span in Calorie Restricted Mice.

Calorie restriction (CR) without malnutrition extends life span in several animal models. It has been proposed that a decrease in the amount of polyunsaturated fatty acids (PUFAs), and especially n-3 fatty acids, in membrane phospholipids may contribute to life span extension with CR. Phospholipid PUFAs are sensitive to dietary fatty acid composition, and thus, the purpose of this study was to determine the influence of dietary lipids on life span in CR mice. C57BL/6J mice were assigned to four groups (a 5% CR control group and three 40% CR groups) and fed diets with soybean oil (high in n-6 PUFAs), fish oil (high in n-3 PUFAs), or lard (high in saturated and monounsaturated fatty acids) as the primary lipid source. Life span was increased (p < .05) in all CR groups compared to the Control mice. Life span was also increased (p < .05) in the CR lard mice compared to animals consuming either the CR fish or soybean oil diets. These results indicate that dietary lipid composition can influence life span in mice on CR, and suggest that a diet containing a low proportion of PUFAs and high proportion of monounsaturated and saturated fats may maximize life span in animals maintained on CR.

Influence of dietary fat source and feeding duration on pig growth performance, carcass composition, and fat quality (2014)

A total of 160 finishing pigs (PIC 327 × 1050; initially 100.5 lb) were used in an 84-d experiment to evaluate the effects of dietary fat source and feeding duration on growth performance, carcass characteristics, and fat quality. Dietary treatments included a corn-soybean meal control diet with no added fat or a 3 × 3 factorial with main effects of fat source (4% tallow, 4% soybean oil, or a blend of 2% tallow and 2% soybean oil) and feeding duration (d 0 to 42, 42 to 84, or 0 to 84). One pig was identified in each pen on d 0, and biopsy samples of the back, belly, and jowl fat were collected on d 0, 41, and 81. At the conclusion of the study, all pigs were harvested, carcass characteristics were measured, and back, belly, and jowl fat samples were collected. Overall (d 0 to 84), there were no differences between fat sources for growth and carcass characteristics; however, pigs fed diets with added fat from d 0 to 84 had improved (P < 0.036) F/G compared with pigs fed a control diet without added fat. Pigs fed added fat throughout the entire study also had improved (P < 0.042) ADG and F/G and heavier d-84 BW (P < 0.006) compared with pigs fed additional fat for only period 1 or 2. Adding fat for the entire study increased (P < 0.032) backfat and tended to reduce (P < 0.083) fat-free lean index compared with pigs fed the control diet without added fat. Added fat also increased (P < 0.05) iodine value (IV) compared with pigs fed the control diet. Increasing the feeding duration of soybean oil or a blend of soybean oil and tallow decreased monounsaturated and increased polyunsaturated fatty acids relative to feeding tallow (duration × fat source interaction, P < 0.05), with the greatest changes in C18:1 and C18:2, respectively. In conclusion, feeding added fat improved ADG and F/G; however, feeding soybean oil for increasing duration, either alone or in a blend with tallow, negatively affected the fatty acid composition and IV of finishing pigs.; Swine Day, Manhattan, KS, November 20, 2014

Influence of Dietary Fat Source on Growth Performance Responses and Carcass Traits of Broiler Chicks

This study was conducted to determine the effects of three different fat sources and their combination on growth performance, carcass traits and intestinal measurements of broiler chickens reared to 42 d of age. Two hundred day-old male broiler chicks (Ross 308) were randomly assigned to one of five treatments with four replicates of 10 chicks based on a completely randomized design. The dietary treatments consisted of 4% added fat from three different sources and their combination as follows: T, diet containing 4% tallow; CO, diet containing 4% canola oil; SFO, diet containing 4% sunflower oil; TCO, diet containing 2% tallow+2% canola oil; TSFO, diet containing 2% tallow+2% sunflower oil. Dietary fat type affected significantly BW and gain as well as feed efficiency in birds fed the TCO diets compared with those fed the other diets. Dietary fat type also modified meat yield, resulting in a higher breast and drumstick yields in the birds fed TCO and TSFO diets, respectively. Most of internal organ relative weights and small intestine measurements were not influenced by dietary treatments, except for the abdominal fat pad weight that was lower in birds fed SFO and for small intestinal length that was influenced by fat source. Results from the current study suggested that the supplementation with a combination of vegetable and animal fat sources in broiler diet supported positively growth performance and carcass parameters.

Influence of dietary fat on pork eating quality

This study compared the influence of dietary fat sources on meat quality, fatty acid composition and sensory attributes in pork. The experiment was conducted with 43 entire male pigs (Pietrain×(Landrace×Large White)) which were fed a basal diet without added fat (control diet) or supplemented with different sources of fat: animal fat (1%, AF1; 3%, AF3), soyabean oil (1%, SBO1) and calcium soaps of palm oil (1%, CaSPO1). Dietary fat supplementation did not significantly affect ultimate pH, colour, Warner–Bratzler shear force values, sensory attributes or SFA. Pigs fed SBO1 had the lowest proportion of MUFA and the highest of PUFA. In conclusion, these dietary fat sources could be recommended for inclusion in diets, at these levels, with no detrimental effect on eating quality. Despite finding no significant differences, the PCA afforded a comprehensive view of the predominating attributes of pork from animals fed the different fats.

Influence of dietary fat source and supplementary α-tocopheryl acetate on pulmonary hypertension and lipid peroxidation in broilers

An experiment was conducted to examine pulmonary hypertension and lipid peroxidation of broilers as affected by dietary fat source and α-tocopheryl acetate. Two hundred and forty day-old male chicks were used in a completely randomized design with five treatments consisted of four replicates and 12 chicks per replicate. Treatments included a control group that received no supplemental fat (treatment 1) or groups that received diets supplemented with beef tallow, soybean oil, a 50:50 blend of beef tallow and soybean oil, or soybean oil plus α-tocopheryl acetate added at 220 mg/kg (treatments 2 to 5). All diets were kept isoenergetic and isonitrogenous and diet treatments 2 to 5 had 50 g/kg of fat supplement. Results showed that weight gain and feed consumption were significantly (p ≤ 0.05) increased by adding fat to the diet during the starter stage. However, birds that received fat-supplemented diets gained less (p ≤ 0.05) during the grower period. Serum malone dialdehyde concentration and glutathione peroxidase activity were not affected by dietary treatments with the exception that inclusion of α-tocopheryl acetate to the diet supplemented with soybean oil significantly (p < 0.05) reduced the activity of the enzyme when measured at 21 days of age. The relative weights of heart and liver and the right ventricle weight to total ventricle weight ratio were greater in broilers fed fat-supplemented diets (p < 0.05).

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Two experiments were planned to study the influence of dietary fat sources (fish oil (FO) or sunflower oil (SO)) and dietary doses of &alpha;-tocopheryl acetate (&alpha;-TA) (0, 60 and 120 mg/kg of feed) and vitamin A (0 IU, 10000 IU and 20000 IU) on lipid oxidation of stored eggs in three stages of 0 or fresh, 1 and 2 months of storage time. In the first experiment, 96 hen layers in six treatments including two oil sources (FO and SO) and two dietary [0, 60 and 120 mg/kg doses of &alpha; -tocopheryl acetate (&alpha;-TA)] were fed for 75 days. In the second experiment, 96 hen layers in six treatments including two sources of &omega;3 and &omega;6 (FO and SO) and three doses&nbsp; 0, 10000 and 20000 IU of vitamin A were fed for 75 days. The results showed that using &alpha;-TA supplementation, lipid stability of enriched eggs increased and was very effective throughout the stored period of the eggs. Yolk TBA value was higher in fish oil than sunflower oil groups (p &lt; 0.01). The treatments that contained 120 mg/kg of &alpha;-TA in diets, showed lower lipid peroxidation than other groups in stages of 2 and 3 storage time (30 and 60 days). The degree of lipid oxidation in fresh, 1 and 2 months of storage eggs was measured by the lipid TBA values. The results showed that TBA value in fresh and stored eggs was higher in groups containing fish oil than other groups (p &lt; 0.01). The MDA value in stage 1 was higher in fish oil group and in 2 and 3 stages was lower in FO + A1. Therefore, addition of Vitamin E and A as natural antioxidants in diets containing oil source for the prevention of lipid oxidation is recommended. &nbsp; Key words:&nbsp;Fish oil, sunflower oil, &alpha;-tocopheryl acetate, vitamin A, TBA value, egg. &nbsp; &nbsp;

Oxidative Stability of Dark Chicken Meat Through Frozen Storage: Influence of Dietary Fat and α-Tocopherol and Ascorbic Acid Supplementation

We used factorial design to ascertain the influence of dietary fat source (linseed, sunflower and oxidized sunflower oils, and beef tallow) and the dietary supplementation with α-tocopheryl acetate (α-TA) (225 mg/kg of feed) and ascorbic acid (AA) (110 mg/kg) on dark chicken meat oxidation (lipid hydroperoxide and TBA values and cholesterol oxidation product content). α-TA greatly protected ground and vacuum-packaged raw or cooked meat from fatty acid and cholesterol oxidation after 0, 3.5, or 7 mo of storage at -20 C. In contrast, AA provided no protection, and no synergism between α-TA and AA was observed. Polyunsaturated fatty acid-enriched diets (those containing linseed, sunflower, or oxidized sunflower oils) increased meat susceptibility to oxidation. Cooking always involved more oxidation, especially in samples from linseed oil diets. The values of all the oxidative parameters showed a highly significant negative correlation with the α-tocopherol content of meat.

Influence of Dietary Fat Source, α-Tocopherol, and Ascorbic Acid Supplementation on Sensory Quality of Dark Chicken Meat

We studied the influence of dietary fat source and dl-alpha-tocopheryl acetate and ascorbic acid supplementation on the sensory quality of cooked dark chicken meat stored at −20 C for different periods. Results showed that dietary fat source and alpha-tocopheryl acetate supplementation influenced sensory scores (rancid flavor and aroma and acceptability). Ascorbic acid had no influence on these scores. Thiobarbituric acid values showed a high correlation with sensory scores. In addition, the low levels of alpha-tocopheryl acetate contained in the trace mineral-vitamin mix (20 IU/kg of feed) were enough to prevent rancidity development in cooked dark chicken meat when broilers were fed a saturated fat diet and samples were vacuum-packed and stored at −20 C for 13 mo.

Lipid Oxidation in Fresh and Spray-Dried Eggs Enriched with ω3 and ω6 Polyunsaturated Fatty Acids During Storage as Affected by Dietary Vitamin E and Canthaxanthin Supplementation

A 2 × 2 × 2 factorial experiment was planned to study the influence of dietary fat source (linseed oil or sunflower oil) and dietary doses of α-tocopheryl acetate (α-TA) (0 or 200 mg/kg of feed) and canthaxanthin (CX) (0 or 5 mg/kg of feed) on fatty acid (FA) composition and lipid oxidation of fresh and spray-dried eggs. Dietary supplementation with α-TA and CX modified the levels of certain long-chain polyunsaturated FA (PUFA). Lipid oxidation in fresh eggs and spray-dried eggs at 0, 6, and 12 mo of storage was measured by the lipid hydroperoxide (LHP) and TBA values. The LHP and TBA values were up to 10 times higher in spray-dried eggs than in fresh eggs. The evolution of LHP and TBA values in spray-dried eggs showed that ω3 FA-enriched eggs were more susceptible to lipid oxidation than those enriched with ω6 FA. The α-TA supplementation increased the lipid stability of enriched eggs and was very effective throughout the storage of spray-dried eggs. On the other hand, CX supplementation did not prevent lipid oxidation in PUFA-enriched eggs. Moreover, no synergistic effect between both compounds was detected.

Influence of dietary fat source and copper supplementation on broiler performance, fatty acid profile of meat and depot fat, and on cholesterol content in meat

1. Three hundred and twenty d-old chickens were fed on a wheat/maize‐soyabean meal diet supplemented with (i) 50 g/kg lard, (ii) 25 g/kg lard and 25 g/kg rapeseed oil, (iii) 50 g/kg rapeseed oil, and (iv) 50 g/kg rapeseed oil and 200 mg copper per kg as copper sulphate pentahydrate. 2. Final weights at 39 d of age in chickens receiving rapeseed oil were lower by 9% than in those fed on the diet containing only lard ( P <0.05). The fatty acids profiles of lipids extracted from the tissues of 10 chickens per group reflected those of the diets. 3. The polyunsaturated fatty acid (PUFA) content of breast muscles and abdominal fat (expressed as a percentage of total fatty acids) was increased and the ratio of n-6:n-3 fatty acids was decreased by the substitution of lard by rapeseed oil ( P <0.001). These changes were more pronounced for the adipose tissue than for breast muscles. 4. Copper sulphate supplementation increased the final body weight of chickens by 4.3% ( P <0.05), reduced the saturated fatty acid (SFA) proportion ( P <0.05) in abdominal fat and increased the PUFA:SFA ratio ( P <0.05). The magnitude of improvement, however, was small. 5. The substitution of rapeseed oil for lard decreased the concentration of cholesterol in breast muscles by 13%. Copper supplementation further reduced the cholesterol content by 25%. Both effects were significant ( P <0.001).

Cholesterol oxidation in frozen dark chicken meat: influence of dietary fat source, and α-tocopherol and ascorbic acid supplementation

A factorial design assessed the effect of dietary fat source (beef tallow, fresh and oxidized sunflower oils, and linseed oil), and α-tocopheryl acetate (α-TA) and ascorbic acid (AA) supplementation (225 and 110 mg/kg feed, respectively) on the cholesterol oxidation product (COP) content and 2-thiobarbituric acid (TBA) values in raw and cooked dark chicken meat vacuum packaged and stored at −20°C for 7 months. COP determination showed good linearity, recovery and precision. Dietary α-TA was highly effective in protecting raw or cooked meat from cholesterol and fatty acid oxidation, regardless of its degree of unsaturation. In contrast, AA supplementation was ineffective and even promoted oxidation in raw meat from broilers fed unsaturated fat diets that had not been supplemented with α-TA. Oxidation values (raw or cooked meat) from α-TA or α-TA+AA supplemented diets were not statistically different ( P>0.05). TBA and COP values were significantly correlated in raw samples ( r=0.6466, P=0.0001).

The influence of changes in dietary fat and oils on fatty acid profiles of carcass fat in finishing pigs

The influence of dietary fat source on gross carcass composition and the rate of change of carcass fatty acids in growing–finishing pigs was studied. Three sources (Rape seed oil, R; Soya bean oil, S; Tallow, T), were included into iso-caloric and iso-nitrogenous grower and finisher diets at rates of 60, 60 and 65.5 g/kg. Diets were fed from 25 to 55 kg live weight. Thereafter, until 92.5 kg, treatments were either a continuation of the grower phase or a change to one of the other diets. Thus, there were nine combinations: TT, TR, TS, RR, RT, RS, SS, ST, SR—the first letter indicates the fat fed in the grower, the second, in the finisher. Three animals per treatment group were slaughtered at 67.5, 80.0 and 92.5, together with three at 55 kg to provide a base-line. Samples of both inner and outer shoulder fat were taken at all slaughter weights and analysed for fatty acid content. The results demonstrated that fatty acid profiles of carcass fat reflected those of the dietary fat, with the inner layer tending to be more saturated. Thus, for example, the concentrations of linoleic acid (g/kg fat) in the outer layer of backfat changed from 225 to 201 (treatment RT), 171 to 206 (TR), 359 to 212 (ST) and 171 to 292 (TS) between 55 kg and final slaughter weight. Rate of change of fatty acid concentration with increasing slaughter weight following diet changeover at 55 kg was estimated from exponential functions. There were differences in the rate of change of individual fatty acid concentrations as influenced by the source of that fatty acid. Thus, for linoleic acid, the rate of change (estimated as the proportion of the concentration at a specific time compared with that of the asymptote) was 0.66, 0.88 and 0.95, respectively at 2, 4 and 6 weeks for RT compared with 0.61, 0.82 and 0.92 for ST. Generally, data demonstrated that the bulk of changes (between 0.6 and 0.7, expressed as a proportion of function asymptotes) occurred within approximately 14 days.

The influence of dietary fat source (sunflower oil or olive oil) on LDL composition and serum lipid levels in miniature swine ( Sus scrofa)

A total of 24 miniature swine ( Sus scrofa) were fed with two diets of 9% fat content, differing only in the quality of the fat source (sunflower oil and olive oil). Two groups of animals were fed for a 12-week period, and the other two groups were fed for a 50-week period. After the two experimental periods, the influence of the dietary fat on serum lipids and protein and fatty acid composition of isolated LDLs was studied. In the short term, the serum cholesterol level was slightly higher in the olive oil group but, with the time of adaptation to the diet, serum levels of TC, FC and PL increased significantly in the sunflower group. In the long term, LDL and HDL were also significantly higher in the sunflower group when compared to the monounsaturated diet. In the sunflower group, PROT/TC and PROT/LIP ratios decreased significantly with the experimental period, while in the olive oil group they increased, due to the decrease in EC and TG fractions. The LDL particle in the olive group contained fewer saturated fatty acids and more monounsaturated fatty acids, specially oleic acid, than the LDL in the sunflower group. The changes found in chemical and fatty acid compositions of LDL, according to the saturation degree of the predominant fat of the diet, could alter its cellular metabolism.

Influence of dietary fat source on oxidative stability and fatty acid composition of milk from cows receiving a low or high level of dietary vitamin E

Fifteen primiparous Holsteins were used in a latin square design with three periods and three treatments to assess the effect of fat source on milk flavour, yield and composition, and composition of milk fat. A basal diet was supplemented with one of three concentrates offered twice daily: soybean meal (no supplemental fat); cracked, micronized soybeans (containing 20 g kg−1 oil); and soybean meal plus CSFA which supplies an amount of fat similar to that of the soybeans. Periods lasted 6 wk, and each cow received 6000 IU dL α-tocopheryl acetate d−1 for the last 2 wk of each period. Measurements of milk yield, composition and flavour were made at the end of weeks 4 and 6 of each period. Feeding CSFA reduced DM intake (P = 0.064), but fat supplemented diets tended to supply more NE1 than the unsupplemented diet (P = 0.085). Yields of milk (P &lt; 0.001), fat (P &lt; 0.001) and energy (P = 0.003) were increased by fat supplementation. Protein yield was reduced (P = 0.003) when CSFA were fed. Soybeans reduced fat concentration in milk, but only before supplemental vitamin E was given. Soybeans increased α-tocopherol output in milk (P &lt; 0.05). Milk from cows fed soybeans was most susceptible to oxidation (P &lt; 0.01). Intensity of oxidized flavour was similar before and during vitamin E supplementation. Fat supplementation reduced the proportion of short- and medium-chain fatty acids (P &lt; 0.001) and increased the proportion of C18 fatty acids in milk (P &lt; 0.001). Soybeans increased the proportion of polyunsaturated fatty acids in milk but CSFA did not. Soybeans can escape biohydrogenation in the rumen and render milk susceptible to oxidation by increasing the proportion of polyunsaturated fatty acids. At the levels fed, vitamin E did not prevent oxidation due to its low transfer to milk. Key words: Oxidized milk, fatty acids, soybeans, tocopherol, dairy cow