Feeding laying hens a bioavailable soy sterol mixture fails to enrich their eggs with phytosterols or elicit egg yolk compositional changes.

Coronary heart disease (CHD) is the leading cause of death in the United States. Elevated levels of plasma total cholesterol (TC), and particularly plasma low density lipoprotein-cholesterol (LDLC), are primary contributing factors to CHD. Dietary plant sterols (phytosterols) have been shown to significantly reduce plasma TC and LDLC in humans, primarily through inhibition of intestinal cholesterol absorption, and are potentially effective agents for reduction of CHD risk. Although a variety of phytosterol-containing foods are currently available, phytosterol-enriched eggs, which represent a potential value-added product, are conspicuously absent from the marketplace. Therefore, the objectives of this study were 1) to enrich shell eggs with phytosterols; and 2) to determine if feeding phytosterols to hens elicits egg compositional changes, particularly that of yolk cholesterol content. Sixteen 32-wk-old White Leghorn hens were fed a corn-soy-based layer diet without (n = 8) or with (n = 8) 1 g of supplemental soy sterols/100 g of diet for 28 d.. Hen performance was determined on an individual basis, and 1 egg/hen per week was collected, processed, and analyzed for yolk cholesterol, CP, crude fat (CF), and phytosterol content. There was no effect (P > 0.05) of supplemental dietary phytosterols on 28-d weight gain, feed consumption, feed efficiency, plasma TC, hen-day egg production, egg weights, egg component weights, and yolk cholesterol, CP, and CF contents. Small amounts of campesterol were present in most of the eggs (average of 0.29 and 1.02 mg/yolk for control vs. soy sterol-fed hens, respectively; P < or = 0.05), whereas only 3 of the 80 analyzed eggs contained trace amounts of beta-sitosterol and none contained any detectable stigmasterol. It was concluded that phytosterols are either poorly absorbed from the chicken intestine or, if they are absorbed, they are efficiently secreted back into the intestinal lumen, most likely via as yet uncharacterized adenosine triphosphate-binding cassette transporters.

Relationship between inhibition of mevalonate biosynthesis and reduced fertility in laying hens.

The objective of the present study was to determine the effects of inhibition of mevalonate biosynthesis on fertility and embryonic survival in laying chickens. White Leghorn hens were fed for 5 weeks with a control diet alone or a diet supplemented with one of two concentrations (0.03 or 0.06%) of the 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors atorvastatin, lovastatin or simvastatin. The hens were artificially inseminated once a week and eggs that were not analysed for cholesterol content were incubated. When averaged across dietary groups and expressed as a percentage of all eggs incubated, the incidence of unfertilized eggs was 1.6% (controls), 29.1% (atorvastatin), 4.4% (lovastatin) and 7.9% (simvastatin). In contrast, with the exception of lower values for birds fed 0.06% atorvastatin, all groups had comparable hatchabilities of fertilized eggs. Hatchability of all eggs incubated was decreased in both atorvastatin groups compared with the other treatments. However, embryonic mortality of fertilized eggs was unaffected (P > 0.05) by diet. Compared with controls, maximum decreases in egg cholesterol of 46, 22 and 7% were obtained with atorvastatin, lovastatin and simvastatin, respectively. Although the overall correlation of egg cholesterol content with hatchability was high (r = 0.82), the hatch rate of eggs containing approximately 105 mg cholesterol ranged from 0 to 67%, indicating that egg cholesterol content was not the only factor influencing embryo survival. This is the first study to indicate that a mevalonate-derived product or products plays an important role in avian fertility. In addition, this work challenges the contention that virtually all of the cholesterol in chicken egg yolk is essential for embryonic development and survival.

Evaluation of two novel biochemicals on plasma and egg yolk lipid composition and laying hen performance.

PD132301-2, an inhibitor of acyl-coenzyme A:cholesterol O-acyltransferase (ACAT; EC 2.3.1.26), and 1-stearylboronic acid (SBA), a fatty acid analogue, were orally administered to White Leghorn hens in separate experiments to evaluate their effects on layer performance and plasma and egg yolk lipids. Five 60-wk-old hens each were fed either a corn-soybean meal basal layer ration, or the basal diet supplemented with .0121, .0363, or .1089% PD132301-2. In a second experiment, 12 37-wk-old hens each were fed either a basal layer ration, or the basal diet supplemented with .20 or .40% SBA. The duration of the experiments were 21 and 16 days, respectively. Neither compound significantly affected hen-day production, egg weight, yolk weight, BW gain, feed consumption, feed efficiency, plasma total cholesterol and triglyceride concentrations, or egg yolk cholesterol content. PD132301-2 had no effect on yolk fatty acid profiles, and C22:6n3 was the only fatty acid altered by SBA. Although 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors have been successful in reducing egg cholesterol, ACAT inhibitors and fatty acid analogues apparently hold little promise in this regard. The results of the present work also support the concept that, in order to pharmacologically alter the cholesterol content of eggs, direct inhibition of key enzymes in the cholesterol biosynthetic pathway is necessary.

Fatty acid composition of mature human milk of Egyptian and American women.

Fatty acid composition of mature human milk of rural Egyptian and American women was determined by gas-liquid chromatography. Milk of Egyptian women contained significantly higher percentages of capric, lauric, myristic, linoleic and arachidonic acids, saturated fatty acids (SFA), and polyunsaturated fatty acids (PUFA). Conversely, milk of American women contained higher percentages of stearic and oleic acids, total unsaturated fatty acids, and monounsaturated fatty acids. The PUFA:SFA ratio in Egyptian samples was 0.54 +/- 0.18 compared to 0.47 +/- 0.22 in American samples. Increased percentages of medium-chain SFA in Egyptian milk suggested increased mammary gland lipid synthesis. Analysis of Egyptian diets indicated high-carbohydrate and low-fat intakes may have resulted in limited availability and incorporation of dietary fatty acids into milk triglycerides. Thus, increased percentages of medium-chain SFA observed in Egyptian milk may reflect mammary gland synthesis in an attempt to maintain lipid concentrations in milk.

Dietary self-selection and the regulation of protein and energy intake in chicks.

Studies were conducted to determine whether chicks could regulate their protein intake independent of total energy intake in self-selection feeding trials. Day-old White Mountain cockerels were reared in electrically-heated battery brooders and given access to either a 23% protein control ration (no choice) or two diets containing 10% or 60% protein with or without supplemental amino acids. The latter were added to either improve the dietary amino acid balance or to alter plasma and brain levels of free large neutral amino acids (tryptophan, isoleucine, leucine, valine, phenylalanine, and tyrosine) which have been implicated in the neuroregulation of feed intake. Both feed and water were provided ad lib, and the location of the feed troughs within each pen were changed daily. Body weights and feed intakes were measured daily, and total calorie and protein intakes were calculated. Chicks offered 10% and 60% protein diets with no supplemental amino acids exhibited reduced weight gains and markedly higher protein intakes as compared to birds fed either the control ration or those given a choice between 10% and 60% protein diets supplemented with methionine. The higher protein consumption by chicks fed the unsupplemented diets most likely was a result of an attempt to compensate for a dietary methionine deficiency. Chicks fed the 10% and 60% protein diets supplemented with amino acids grew at a slower rate than those fed the 23% protein control diet. In general, plasma and brain data did not support a proposed relationship between certain large neutral amino acid ratios and protein or energy intake.

A comparison of methionine sources for broiler chickens fed corn-soybean meal diets under simulated commercial grow-out conditions.

Two experiments, involving 5,760 birds each, were conducted under simulated commercial grow-out conditions to determine the relative response of broiler chicks to two supplemental levels each of DL-methionine (DL-MET), L-methionine (L-MET), and methionine hydroxy analogue-free acid (MHA-FA) fed on an equimolar basis in corn-soybean meal diets. MHA-FA was shown to support 49-day weight gains comparable to those of chicks fed DL-MET, and both sources were superior to L-MET in this regard. However, there were no significant differences due to MET sources in the efficiency of feed utilization. When compared to basal-fed chicks, birds fed supplemental L-MET, DL-MET, or MHA-FA had elevated plasma free MET levels, whereas cyst(e)ine and taurine concentrations were not affected by dietary treatment. There were no effects of diet on either mortality or the incidence of leg abnormalities. The results of these studies suggest that MHA-FA is an acceptable source of MET for broiler chicks fed corn-soybean meal diets from day-old to market weight.

Partial alleviation of phenylalanine toxicity in the chick by supplemental dietary tryptophan.

Studies were conducted to determine the physiological effects of feeding diets containing high levels of phenylalanine to chicks. Marked reductions in weight gain and feed conversion were observed in birds fed a diet containing 2.52% L-phenylalanine and .47% L-tyrosine. Excess dietary phenylalanine caused elevations of phenylalanine and tyrosine in serum and brain, whereas cerebral concentrations of free isoleucine, leucine, and valine were generally decreased. Supraoptimal amounts of glycine, arginine, and tryptophan were fed in an attempt to alleviate the toxic symptoms observed in birds fed high phenylalanine diets. Only tryptophan supplementation proved successful in partially alleviating the growth-depressive effects of phenylalanine toxicity. Both serum and brain levels of tryptophan were increased by tryptophan supplementation. Results of two radiotracer studies with 14C-tryptophan suggested that brain uptake of tryptophan was inhibited by hyperphenylalaninemia.

Investigations of leg abnormalities in chicks consuming high tannin sorghum grain diets.

Studies were conducted into the etiology of leg abnormalities noted in chicks fed high tannin sorghum grain diets. These anomalies were characterized by a bowing of the legs with a swelling of the hock joints. The incidence of these leg problems was found to be markedly higher when the amino acids in the diet provided by soybean meal were replaced by crystalline amino acids. Supplemental vitamins and minerals had no alleviating effect on the leg problem. Bone mineralization was apparently not influenced by tannins as demonstrated by similar bone ash values for chicks fed high or low tannin sorghums. A possible alteration caused by tannin in the organic matrix of bone is discussed. High tannin sorghum depressed chick growth and feed conversion when compared with low tannin sorghum in both sorghum-soybean meal and sorghum-amino acid rations. This growth depression was overcome by supplementing the high tannin sorghum-soybean meal diet with .15% DL-methionine, but no growth response was observed from a similar supplementation of a high tannin sorghum-amino acid diet.