Abstract
The Thoroughbred is among the most valuable horse breeds, and its husbandry is a major industry. Mare's milk plays a major role in the health of neonatal foals. Although the main components of mare's milk are broadly characterized, free oligosaccharides (OS), which possess various bioactivities in many mammalian milks, have not been fully profiled in Thoroughbreds. The aim of this study was to identify and quantify OS in Thoroughbred mare's milk during the first week of lactation, when foals typically consume mare's milk exclusively. A total of 48 OS structures (including isomers and anomers), corresponding to 20 unique compositions, were identified by nano LC‐Chip QToF‐MS and confirmed by tandem mass spectrometry. Neutral OS were the most abundant glycans (58.3%), followed by acidic OS containing Neu5Ac (33.3%), a minor presence of fucosylated OS structures (6.25%) and one structure containing NeuGc (2.1%). Comparison with other well‐characterized mammalian milks revealed that mare's milk shared 8 OS structures with human, bovine, pig and goat milk (i.e., 2 sialyllactose isomers, 3 hexose, LNH, LNT, and OS with the composition 3 Hex‐1 Neu5Ac). Additionally, there were seven unique OS not previously found in other mammal milks. During the first 7 days of lactation, the percentage of neutral and fucosylated OS increased, whereas acidic OS decreased and the total OS concentration ranged from 217.8 mg·L−1 to 79.8 mg·L−1.
Highlights
The Thoroughbred is among the most valuable horse breeds, and its husbandry is a major industry
This study identified and quantified OS in mare’s milk during the first week of lactation
It is likely that the untargeted approach used in this study, combined with the high accuracy, sensitivity, and excellent chromatographic resolution obtained by the nano LC-Chip quadrupole time-of-flight (QToF)-MS technology [24], allowed the detection of all the OS in the samples analyzed
Summary
The Thoroughbred is among the most valuable horse breeds, and its husbandry is a major industry. Milk oligosaccharides (OS) are typically composed of 3–10 monosaccharide units, including glucose (Glc), galactose (Gal), N-acetyl-glucosamine (GlcNAc), N-acetyl-galactosamine (GalNAc), fucose (Fuc), and sialic acids (NeuAc/NeuGc). OS are classified as neutral (containing glucose/galactose/ GlcNAc/GalNAc/fucose) or acidic (which include the previously mentioned monosaccharides and are further decorated by the sialic acids NeuAc/NeuGc) These free glycans are not digestible by neonates, they exhibit a wide variety of biological roles, with potential prebiotic, antimicrobial, anti-adhesive, and immunomodulatory activity [4]. Mare’s milk unique OS profile gut microbiome in the early life of mammals [5] Their structural composition determines the accessibility of carbohydrates for bacteria in the large intestine and selects which taxa dominate the distal gut of neonates [6]. A recent study showed that bovine whey colostrum N-glycans released by the novel enzyme endo-bN-acetylglucosaminidase selectively promoted the growth of B. longum subsp. infantis ATCC 15697 [10]
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