Hen feed and egg fatty acids

Last update: 24 August 2020

Introduction

Overconsumption of n-6 PUFA is suspected to be behind much of the chronic disease in the developed world, and it therefore may be necessary to lower the intake to a manageable level. Eggs are a highly nutritious food, but their fatty acid profile leaves something to be desired, at least for factory farmed products. It is already known that the amount of linoleic acid in an egg’s yolk is proportional to the amount of linoleic acid a hen consumes1. This experiment seeks to establish what is possible to do in terms of lowering the amount of linoleate in egg yolks in the setting of a family farm in Poland – a poorly controlled environment.

Methods and materials

The hens used in this study are approximately 15 months old, chiefly of the common red-white sex link commercial variety, but some are mixed breeds from own incubation. They have daytime access to approximately 178 m2 of backyard pasture (only about half of which is grass, due to drought and herbivory).

There were two feeding interventions, each lasting 15 days, as it was already shown that this time is sufficient to reach the point of diminishing returns for yolk fat reflection of dietary fat2. These would be compared against a baseline from before the first intervention.

At baseline, the hens were fed (in addition to whatever they would forage from their environment) the following, in rough order of quantity:

  • wheat,
  • commercial feed (17.8% crude protein, 3.5% crude fat),
  • oats,
  • human scraps (such as stale bread),
  • boiled potatoes,
  • barley,
  • dog food scraps.

The first intervention (RICE) limited hen nutrition largely to (as much as was possible given the circumstances, but allowing for accidental sabotage by self and third parties):

  • white rice,
  • commercial layer protein concentrate (41.5% crude protein, 1.34% crude fat),
  • human scraps.

The second intervention (WHEAT) limited hen nutrition largely to (with same caveats as above):

  • wheat,
  • commercial layer protein concentrate (41.5% crude protein, 1.34% crude fat),
  • barley (limited supply),
  • human scraps.

The commercial feeds and grains components of the diets above were provided to the hens on an ad-libitum basis (except where noted), trusting the hens’ protein leverage mechanism to guide their consumption adequately. Scraps were provided on an irregular schedule, as a treat, primarily limited by momentary availability.

A commercial laboratory was employed to do fatty acid testing of the eggs, using gas chromatography (GC/FID). Each sample, both baseline and the intervention, was composed of 10 eggs, chosen chiefly for their cleanliness from the most recent batch following the intervention period (or preceding the first one, in case of the baseline).

Results

As expected, the amount of linoleate in the yolks varied according to the amount of linoleate in the feed. Unexpectedly, the strength of the interventions was quite low.

Fatty acid typeBaseline (% total fat)RICE (% total fat)WHEAT (% total fat)
SFA35.3735.8733.97
MUFA56.7957.2758.76
n-3 PUFA0.270.360.37
n-6 PUFA7.576.506.94
Table 1: Summary of results.

Conclusion

Based on these findings, it seems clear that small-time farmers in Poland supplementing their hens with commercial feed, but chiefly using unprocessed grains, can produce eggs that are much lower in linoleate than is considered standard for factory farmed eggs. At the same time, the type of grain does not seem to play a large role. Use of practically available means of lowering linoleate of layer feed yields only small improvements in absolute yolk linoleate.

References

  1. Modified Egg Composition To Reduce Low-Density Lipoprotein Oxidizability: High Monounsaturated Fatty Acids and Antioxidants versus Regular High n−6 Polyunsaturated Fatty Acids. Niva Shapira and Joseph Pinchasov. Journal of Agricultural and Food Chemistry 2008 56 (10), 3688-3693 DOI: 10.1021/jf073549r
  2. Yalcin, Hasan & Nal, Mustafa. (2010). The Enrichment of Hen Eggs with x-3 Fatty Acids. Journal of Medicinal Food. 13. 10.1089/jmf.2008.0024.