Variability of cholesterol concentration in plasma and egg yolks of hens and evaluation of the effect of some dietary oils

Effect of dietary fish meal on production performance and cholesterol content of laying hens

The effect of dietary fish meal (FM) on production and egg yolk cholesterol of commercial Hyline White Leghorn hens (24-week old) was studied for four weeks. Eighty birds were given a corn-wheat-soyabean meal diet that contained either 0% (control diet, C) or 3% fish meal (DM basis). Hens were randomly divided into two experimental treatments with four replicates (10 hens per replicate). Egg weight, daily egg production (g/hen/day), daily feed consumption and feed conversion ratio were recorded. At the end of each week, 12 eggs from each group were randomly collected and egg yolk cholesterol, egg volume, shell thickness and Haugh unit (HU) were measured. There was no significant (p > 0.05) effect of feeding 3% FM on egg yolk cholesterol concentration (mg/100 g yolk or mg/yolk) compared with the control diet, but 3% FM, tended to decrease egg yolk cholesterol concentration (1930.93 vs 2021.48 mg/100 g yolk). Hens fed on 3% FM had higher (p < 0.05) egg production, egg weight, egg volume, shell thickness, HU and better feed conversion ratio. It was concluded that under the condition of the study, feeding 3% fish meal improved egg production traits but was not able to reduce cholesterol concentration of the egg yolk although tended to reduce cholesterol concentration.

Variation in plasma cholesterol concentration over time in the domestic fowl

1. Variations in the concentration of plasma cholesterol available to the developing oocyte over a three week period in Gallus domesticus are described. 2. There are small changes in concentration between weeks for individual birds, but no changes between consecutive days within weeks or times within days. 3. It is recommended that future attempts to assess the relationship between variation in blood and yolk cholesterol concentrations estimate blood cholesterol concentration from two samples taken a week apart.

The hypocholesterolemic agent dichloroacetate increases egg cholesterol content of laying hens

Experiments were conducted to determine whether a diet with added dichloroacetate (DCA), an inhibitor of cholesterol biosynthesis, would influence plasma and egg cholesterol concentrations when fed to laying hens. In the first experiment, 62-wk-old laying hens (10 hens per treatment) were fed a control diet containing 0, 350, 700, or 1,400 ppm DCA for an 8-wk period. Egg production and size, feed intake, weight gain, and plasma and egg cholesterol were determined at biweekly intervals. In a second experiment, 36-wk-old laying hens (eight hens per treatment) received diets with 0, 3,000, or 6,000 ppm added DCA for a period of 6 wk. Production parameters and cholesterol measurements were conducted as in Experiment 1. Egg production and feed intake were significantly decreased with increasing levels of DCA in Experiment 1. In the second experiment, 6,000 ppm DCA sharply reduced feed intake, body weight, and egg production. Yolk weight and percentage yolk were significantly decreased by the higher levels of DCA used in Experiment 2. Total plasma cholesterol was not affected by dichloroacetate in either of the experiments. In contrast, egg cholesterol concentration increased by 10 and 37% in Experiments 1 and 2, respectively, in response to diets with added DCA when compared with the unsupplemented controls. Total egg cholesterol increased in response to dietary DCA in Experiment 1, but not consistently in Experiment 2 due to the decreased yolk size of the hens fed DCA. The results of these studies indicate that dietary DCA was not effective in reducing egg cholesterol concentrations.

Variation in egg yolk cholesterol concentration between and within breeds of the domestic fowl

1. The pattern of variation for egg yolk cholesterol concentration between 5 commercial egg layer lines and a cross of Gallus domesticus is described. 2. Yolk cholesterol concentration in the cross was lower than in the lines, and 6.7% lower than the midparent value. 3. It is proposed that the reduced yolk cholesterol concentration of the cross may be a consequence of heterosis, although sex-linkage and/or maternal effects cannot be discounted. 4. The difference between the cross and parental lines is consistent with a physiological relationship between yolk cholesterol concentration and rate of egg production, but not between yolk cholesterol concentration and yolk weight.

Comparison between wheat, triticale, rye, soyabean oil and strain of laying bird on the production, and cholesterol and fatty acid contents of eggs

1. The effects of feeding three types of cereal grain (wheat, triticale or rye) and soyabean oil (0 or 20 g/kg) over a 12-week period on the production, yolk cholesterol and yolk fatty acid concentrations of three strains of laying pullets were studied. 2. Pullets fed on wheat- or triticale-based diets had higher body weight gains, egg productions, egg weights, egg mass and lower yolk cholesterol concentrations than pullets fed on rye-based diets. However, there were no significant differences between the cereals in yolk cholesterol content. 3. There were no significant differences between the three cereals in total food consumption of pullets nor of yolk weight nor yolk concentration of palmitic, stearic and oleic acids. 4. Pullets fed on triticale-based diets had higher yolk linoleic acid concentrations and lower yolk oleic acid: linoleic acid ratios than pullets fed on rye- or wheat-based diets. 5. Soyabean oil supplementation increased egg production, egg mass, yolk linoleic concentration and yolk unsaturated to saturated fatty acid ratio, but reduced yolk oleic acid: linoleic acid ratio. 6. There were differences between strains of pullets in weight gain, food consumption, rate of lay, egg weight and yolk cholesterol, but not in yolk fatty acid concentrations. 7. It was concluded that wheat- or triticale-based diets gave good production of eggs of lower cholesterol content, that soyabean oil supplementation gave eggs with a high unsaturated to saturated fatty acid ratio and that two strains of layers produced eggs with lower yolk cholesterol concentrations than a third strain.

Cholesterol concentration of egg yolk and blood plasma and performance of laying hens as influenced by dietary alpha-ketoisocaproic acid

Experiments were conducted to determine the effect of supplemental alpha-ketoisocaproic acid (KIC) or Leu on layer performance and plasma and egg cholesterol levels. In the first experiment, 0, .09, or .27% KIC and .09 or .27% Leu were fed to 62-wk-old laying hens. In a second experiment, the same levels plus another level of .54% KIC and .54% Leu were fed to 32-wk-old hens for an 8-wk period. The basal diet or the basal diet supplemented with .27% KIC or .27% Leu were continued for 20 wk to determine the long-term effects of these supplements. In a third experiment, hens were fed 0, .1, .2, or .4% KIC for 8 wk. The addition of KIC and Leu to the hen diets did not affect percentage egg production, egg weight, shell thickness, or Haugh units. In Experiment 1, .27% KIC and .09% Leu significantly increased BW gain. Neither KIC or Leu significantly affected BW gain in Experiment 2 when measured at 8 or 28 wk. In the third experiment, diets supplemented with KIC increased significantly BW gain. In Experiment 1, .09% KIC and .09% Leu significantly reduced egg cholesterol at 4 wk. After 8 wk, .27% KIC reduced egg cholesterol significantly below the controls. No effect on plasma or egg cholesterol was observed in Experiments 2 and 3.

Cholesterol content in market hen eggs

The yolk cholesterol content in eggs of White Hisex laying hybrid from 3 specialized commercial farms averaged 1230, 1330 and 1230 mg/100 g of yolk over an 11-months laying period, i.e. 303, 304 and 309 mg cholesterol/100 g of consumable egg portions. In testing Babcock B-380, Moravia SSL, Shaver Starcross 288, and Hisex HX-1, the av. cholesterol content varied from 1200 to 1360 mg/100 g of yolk or from 372 to 444 mg/100 g of consumable egg portions. Throughout the egg-laying period, the yolk cholesterol content fluctuated rather irregularly and showed great variability (variation coefficient 9.7-18.2%). The values recorded failed to follow any of the common functions of the trend. Intensive market egg production was found to be associated with decreases in yolk cholesterol content.

Influence of probucol ((4,4'-isopropylidine dithio)-bis(2,6-di-t-butyl-phenol)) on egg yolk cholesterol content and performance of laying hens

Addition of the hypocholesteremic agent Probucol ((4,4'-isopropylidine dithio)-bis(2,6-di-t-butyl-phenol)) to the diet of laying hens at up to 1% significantly reduced egg yolk cholesterol content (mg/g yolk) without impairment of rate of egg production, egg weight, shell strength, albumen quality, or other production related parameters. Dietary concentration of .1% Probucol significantly reduced yolk cholesterol within 2 weeks after feeding. Higher concentrations did not further reduce yolk cholesterol. Probucol at .025% reduced egg yolk cholesterol within 4 weeks after feeding, but after 8 weeks of feeding, eggs from hens fed .025% Probucol did not differ significantly in yolk cholesterol from those fed the basal unsupplemented diet. This suggests possible adaptation in cholesterol synthesis by the laying hen.

The amino acid and energy requirements of broiler breeder hens

Three trials, involving 1000 broiler breeder hens each, were conducted under rather uniform conditions in order to test the applicability of two models for calculating the amino acid requirements of broiler breeders, and to evaluate their energy requirements. The birds fed diets based on Model A (which assumes that all of the egg white and shell membrane proteins are synthesized during albumen formation and secretion at the expense of tissue proteins) produced at a rate greater than the planned target, whereas Model B (which assumes that only ovoglycoproteins and shell membranes are thus produced) supported a production close to the anticipated performance. This indicates the validity of Model B, developed for egg layers, to predict the requirements of the most limiting amino also for broiler breeder hens. The resulting practical diets contained considerably lower protein levels than customary. According to Model B, minimal amino acid requirements for broiler breeder hens producing a daily egg mass of 52.7 g. having a body weight of 3.5 kg and gaining weight at a rate of 4 g/day, calculated to be as follows (g/hen/day): methionine, .57; sulfur amino acids, .83; lysine, .76; arginine, 1.11; threonine, .72; valine, .92; isoleucine, .85; leucine, 1.25; tryptophane, .19; histidine,

The effect of dietary monoterpenes on the cholesterol level of eggs

Monoterpenes were included in the diets of laying hens in an attempt to inhibit the synthesis of cholesterol and hence reduce its amount in egg yolk. However, feeding five monoterpenes, phorone or 200 mg. cholesterol per day to hens did not significantly change the level of cholesterol in the egg yolk. These compounds did not cause signs of ill health in the hen or a decline in egg production.

Divergent selection for yolk cholesterol in laying hens

1. Lines were selected for divergence in yolk-cholesterol concentration for three and four generations in the Cornell Controll (Leghorn) and Athens-Canadian (AC) (meat-type) randombred populations respectively. Selection was based on both individual and family records. 2. Cholesterol values were obtained from two consecutively laid eggs when birds were 28 weeks of age. The yolks of eggs from individual hens were pooled and analysed for cholesterol content by the colorimetric assay of Zlatkis et al. (1953) on the "fat extract" obtained by a modification of the procedure of Folch et al. (1956). 3. The largest differences between high and low lines (1-27 and 1-38 mg cholesterol/g yolk) were observed in the last generation of selection. There was evidence of a lack of response in the low lines. Realized heritability estimates obtained by dividing the difference between high and low lines by half the cumulative selection differential ranged from 0-11 to 0-25 in the AC population and from 0-21 to 0-25 in the Leghorn population. Realised estimates on a within-line bassis suggest that selection for yolk cholesterol is effective only in the upward direction.

Summary of available data for cholesterol in foods and methods for its determination

A search of the literature has been conducted on the cholesterol content of foods and on the methods for its determination. The amount of cholesterol in food is important because of its possible relationship to the onset of atherosclerosis in humans. Cholesterol is present primarily in foods of animal origin. The main sources in the American diet are eggs, poultry, dairy products, fish and seafood, and meat products. Only a few samples of these products have been analyzed. In many cases there is a wide range in cholesterol values for samples analyzed. Much of the research was conducted many years ago. The most commonly used methods were gravimetric or colorimetric. In many cases the samples investigated were not adequately described. Cholesterol was often determined without isolating it from interfering materials. Although some of the cholesterol values reported in the literature appear to be reasonably accurate, there is an urgent need for reinvestigation of the cholesterol content of foods using more recently developed methods of analysis.