Iron absorption differs in piglets fed extrinsically and intrinsically 59Fe-labeled sow's milk

Area of Science:

• Nutritional Biochemistry
• Animal Physiology

Background:

• Species-specific milk iron bioavailability is crucial for offspring development.
• The extrinsic labeling technique is commonly used but its validity for milk iron absorption requires assessment.

Purpose of the Study:

• To compare iron bioavailability from sow's milk using extrinsic versus intrinsic labeling techniques.
• To validate the extrinsic labeling method for studying milk iron absorption in piglets.

Main Methods:

• Suckling piglets were used as an animal model.
• Sow's milk was labeled intrinsically (intramuscular 59Fe injection) and extrinsically.
• Iron distribution and retention from both labeling methods were compared.

Main Results:

• Intrinsic iron transfer to milk was slow (max 14h post-injection) with low recovery (0.00014%).
• Intrinsic iron predominantly associated with the fat fraction, while extrinsic iron bound to casein.
• Iron retention was substantially higher from intrinsically labeled milk compared to extrinsically labeled milk.

Conclusions:

• The extrinsic tag method is not valid for assessing iron absorption from sow's milk.
• Findings suggest potential invalidity of the extrinsic method for human milk iron absorption studies.