The nutritive value of refined rapeseed oils: A review

Fat composition of milk replacer influences postprandial and oxidative metabolisms in dairy calves fed twice daily

Milk replacers (MR) for calves contain alternative fat sources as substitute for milk fat. This substitution leads to differences in fat properties, such as the fatty acid profile and the triglyceride structure. This study evaluated how fat composition in MR affects gastrointestinal health, blood redox parameters, and postprandial metabolism in calves fed twice daily. Forty-five individually housed male Holstein-Friesian calves (2.3 ± 0.85 d of age) were assigned to 1 of 15 blocks based on the age and the day of arrival. Within each block, calves were randomly assigned to 1 of 3 experimental diets and received their respective diet from arrival until 35 d after arrival. The 3 experimental diets (n = 15 per treatment group) consisted of an MR with a blend of vegetable fats containing rapeseed and coconut (VG), an MR with only animal fats from lard and dairy cream (AN), and an MR containing a mixture of animal and vegetable fats including lard and coconut (MX). The fatty acid profile of each MR was formulated to resemble that of bovine milk fat while using only 2 fat sources. All MR were isoenergetic, with 30% fat (% DM), 24% crude protein, and 36% lactose. Chopped straw and water were available ad libitum from arrival onward but no starter feed was provided. Daily milk allowances were 6.0 L from d 1 to 5, 7.0 L from d 6 to 9, and 8.0 L from d 10 to 35, divided into 2 equal meals and prepared at 135 g/L (13.5% solids). Fecal appearance was scored daily; calves were weighed and blood was drawn on arrival and weekly thereafter. Urine and feces were collected over a 24-h period at wk 3 and 5 to determine apparent total-tract digestibility and assess gastrointestinal permeability using indigestible markers. Postprandial metabolism was evaluated at wk 4 by sequential blood sampling over 7.5 h, and the abomasal emptying rate was determined by acetaminophen appearance in blood. Fat composition in MR did not affect growth, MR intake, gastrointestinal permeability, nor nutrient digestibility. The percentage of calves with abnormal fecal scores was lower at wk 2 after arrival in calves fed VG than MX, whereas AN did not differ from the other treatments. Calves fed AN and MX had higher thiobarbituric acid reactive substances measured in serum than VG, whereas plasma ferric-reducing ability was greater in calves fed MX than VG. Postprandial acetaminophen concentrations did not differ across treatment groups, but the area under the curve was smaller in calves fed VG than in the other 2 treatments, which is indicative of a slower abomasal emptying. Postprandial serum triglyceride concentration was greater in calves fed AN than VG, whereas MX did not differ from the other treatments. Based on these outcomes, all 3 fat blends can be considered suitable for inclusion in MR for calves.

Morphological effects of rapeseed oil in rats. I. Short-term studies

Light microscopy of paraffin embedded and frozen sections, supplemented with electron microscopy, was performed on the heart muscle of young rats fed rapeseed oil in short-term experiments. It was confirmed that high levels of rapeseed oil, which contains erucic acid, produce severe lipoidosis of the heart muscle fibres within 10 days. An attempt was made to find out the lowest level of erucic acid in the rat diet to give rise to pathological fatty accumulation. Several frozen sections from each heart or serial sections in combination with electron microscopy were used for this evaluation. The level found to give rise to pathological fatty accumulation was about 2% by weight (w/w), while rats fed 1% erucic acid showed normal myocardium. No direct proof that erucic acid is of importance in human pathophysiology has hitherto been presented. It is concluded, however, that the similarity in reaction among the many species of experimental animals tested by different workers, as well as the basic metabolic disturbances demonstrated, are in strong favour of a similar effect in man.

Eicosapentaenoic acid causes transient accumulation of lipids in rat myocardium

Rats were given eicosapentaenoic acid (EPA) or palmitic acid (PALM) up to 15 days, and control animals were given carboxymethylcellulose. All suspensions which were given by gastric intubation contained tocopherol. Heart triacylglycerols, heart cholesterol and heart phospholipids significantly increased after one day of EPA treatment, but they were normalized within 15 days. Both after 2 and 10 days of treatment with palmitic acid the heart triacylglycerols were significantly greater than control. The heart cholesterol and heart phospholipids were significantly greater than control after 10 days of treatment with palmitic acid. Total carnitine palmitoyltransferase (CPT) activity in heart was significantly greater in rats treated with EPA for 15 days compared to control, but treatment with palmitic acid had no effect. The fatty acyl-CoA oxidase activity was greater in rats treated with EPA for 15 days and palmitic acid for 10 days compared to control. The fractional volume of lipid droplets in myocardial cells was calculated from electronmicrographs and was 0.112 +/- 0.016% after 1 day of EPA treatment compared to 0.035 +/- 0.016% in the control group. After 5 and 15 days the fractional volume was the same as control. The fractional volume of lipid droplets in rats treated with palmitic acid for 10 days was 0.120 +/- 0.023%. Treatment with EPA caused an immediate accumulation of lipids and lipid droplets in the rat heart which after few days normalized in parallel with an increased activity of total CPT in the heart.

Docosahexaenoic acid induces lipid accumulation in myocardial cells of rats

The aim of the study was to explore whether treatment with highly purified docosahexaenoic acid (DHA) over a short period affects the amount of lipid droplets in myocardial cells of rats, and whether heart peroxisomal enzyme activity is changed. Fifteen rats were fed a standard diet for 10 days and 15 rats were fed a cholesterol diet (2% of cholesterol) for 10 days. In each experiment six rats served as control, and three rats in each treatment group were given one of the following treatments by gastric intubation: DHA at 500, 1000, or 1500 mg day-1 kg-1 body weight. The fractional volume of lipid droplets in myocardial cells was calculated by morphometric methods. The heart triglycerides and the volume fraction of lipid droplets in the myocardium were greater in the standard diet rats treated with DHA compared with controls. There was no such increase caused by DHA treatment in the cholesterol diet rats. The heart fatty acyl-CoA oxidase tended to increase with DHA treatment in both standard and cholesterol diet rats, but this was significantly increased only after treatment with DHA 1500 mg day-1 kg-1 in the cholesterol diet rats. We conclude that treatment with highly purified DHA for 10 days results in cardiac lipidosis, assessed both by biochemical and morphological methods in standard diet rats, whereas DHA treatment has no additive effect on lipid accumulation in cholesterol fed rats.

Biochemical and toxicological studies on the effect of high and low erucic acid rapeseed oil on rats

Rats were fed on diets containing rapeseed oil, either containing low or high erucic acid content as well as the hydrogenated ones for 6 weeks. Body weight gain, biochemical and pathological parameters were investigated. The data showed high body weight gain for rats fed diets containing low erucic rape oil (LERo) compared with those fed either the high erucic rape oil (HERo), the hydrogenated or the partially hydrogenated oil diets. All rats showed non significant changes for total lipids, total cholesterol, GPT and GOT, except the partially hydrogenated rape oil diet which showed significant decrease for total cholesterol. Alkaline phosphatase however showed a significant decrease, while plasma phospholipids showed significant increase in rats fed on the hydrogenated oil diet. Triglycerides indicated non significant increase except in the group that received low erucic rape oil diet. Histopathological study showed changes in all tissues examined (liver and kidney).

The effects of original and randomized rapseed oils containing high or very low levels of erucic acid on cardiac lipids and myocardial lesions in rats

The nutritional status of the very lowerucate, rapseed oil, Brassica napus var. 'Tower,' was compared with that of the high-erucate oil, Brassica napus var. 'Target,' as well as with corn oil. The effect of randomization on the nutritional qualities of rapeseed oil was investigated as well. The feeding of diets containing the original and randomized 'Tower' oil or the original 'Target' oil, at the 20% level by weight, gave growth rates which were not significantly different from that for corn oil. However, the randomized 'Target' oil gave growth rates which were significantly less than all other groups. The growth results could not be explained simply on the basis of food consumption. The level of triglycerides in the hearts of rats fed the very low-erucate oils was not significantly different from the corn oil group. Triglyceride concentrations in the hearts of animals given the high-erucate oils were 7-12 times greater than all other groups. The level of total fatty acids in tissue phospholipids was the same regardless of dietary treatment. Fatty acid compositions of the tissue lipid were the same in animals fed either the original or randomized rapeseed oils. A much higher incidence of focal myocardial necrosis was found in animals receiving high-erucate rapeseed oil relative to animals given the corn oil. The incidence in rats fed diets containing very low-erucate rapeseed oil was intermediate between these latter two extremes.

Mortality and production characteristics of laying chickens fed high- and low-erucic acid rapeseed oils

Laying pullets were fed a diet supplemented with three percent of either high-erucic acid rapeseed (HEAR) oil or low-erucic acid rapeseed (LEAR) oil for 39 weeks. Egg production for the period was 78.8 and 80.1% by the birds fed the respective oils. Average egg weights were 56.8 and 58.7 g. respectively. Gains in body weight, liver weight and adrenal gland weight were similar with the two types of oil fed. Feed consumption was similar for the two groups of birds. The efficiency of utilization of the diet containing HEAR oil was accordingly lower than that of the diet containing LEAR oil. In the birds fed HEAR and LEAR oil respectively mortality attributed to metabolic disorders of the reproductive system, liver, and kidney was 3.3% and 1.2%. Mortality from other causes in the birds fed the two oils was 3.2 and 3.8% of the original populations.