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The desaturation of α-linolenic acid (ALA) to stearidonic acid (SDA) is considered to be rate-limiting for the hepatic conversion of ALA to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in humans, rodents, and chickens. Thus, we hypothesized that feeding laying hens SDA, as a component of the oil derived from the genetic modification of the soybean, would bypass this inefficient metabolic step and result in the enrichment of eggs with EPA and DHA at amounts comparable to that achieved by direct supplementation of hens' diet with these very long-chain (VLC) n-3 polyunsaturated fatty acids (PUFAs). In a 28-d study, laying hens incorporated 0.132 mg, 0.041 mg, or 0.075 mg of VLC n-3 PUFAs into egg yolk for each milligram of ingested dietary ALA derived primarily from conventional soybean oil (CON), dietary ALA derived primarily from flaxseed oil (FLAX), or dietary SDA derived from SDA-enriched soybean oil, respectively. Moreover, the amounts of total yolk VLC n-3 PUFAs in eggs from hens fed the CON (51 mg), FLAX (91 mg), or SDA (125 mg) oils were markedly less than the 305 mg found in eggs from fish oil-fed hens. Unexpectedly, SDA appeared to be more readily incorporated into adipose tissue than into egg yolk. Since egg yolk FAs typically reflect the hens' dietary pattern, these tissue-specific differences suggest the existence of an alternate pathway for the hepatic secretion and transport of SDA in the laying hen.

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Two experiments were conducted in which laying hens were administered lovastatin, a competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, the rate-limiting enzyme of the cholesterol biosynthetic pathway. In the first study, 26-week-old White Leghorn hens were fed corn-soybean meal diets containing either 0,0.0059,0.0124, or 0.0265% lovastatin (analyzed values) for a period of 35 days. Cholesterol content per gram of yolk was significantly lowered with each successive level of lovastatin, whereas egg cholesterol levels plateaued at approximately 151 mg, a 15% reduction from the basal value. In experiment 2,44-week-old White Leghorn hens were fed corn-soybean meal diets containing either 0,0.0290, 0.1198, or 0.2407% lovastatin (analyzed values) for a period of 9 days. In comparison to day 0 values, egg cholesterol contents on day 9 were reduced only at the two highest drug levels, with maximum observed decreases of approximately 8 and 13 % when expressed as milligrams of cholesterol per gram of yolk and milligrams of cholesterol per egg, respectively. No drug residues were detected in acetonitrile extracts of eggs from hens fed the highest dietary levels of lovastatin in each experiment.

Nitrogen-corrected true metabolizable energy (TME n ) and true amino acid digestibility values were determined, using cecectomized cockerels, for 20 sorghum [Sorghum bicolor (L.) Moench] cultivars that ranged in catechin equivalent (CE) percentages from 0 to 3.88. There were significant (P e 0.01) overall inverse relationships between CE content and (1) the individual digestibilities of lysine, methionine, threonine, isoleucine, leucine, valine, phenylalanine, histidine, and arginine; (2) the mean digestibility of essential amino acids; (3) the mean digestibility of nonessential amino acids; and (4) TME n values. In contrast to these overall trends, several cultivars of similar condensed tannin content had markedly different nutrient digestibilities. The dissimilarity of protein digestibilities in sorghum genotypes of similar tannin content was confirmed by subjecting samples of the ground grains to in vitro pepsin digestion with subsequent visualization of the undigested proteins by SDS-PAGE. The present work suggests that other components besides tannins are responsible for variations in the availability of nutrients in sorghum.