High-throughput glycomic analyses reveal unique oligosaccharide profiles of canine and feline milk samples

Abstract

Oligosaccharides are important components of milk, serving as substrates for the intestinal microbiota, acting as antimicrobials that prevent pathogen colonization, and supporting the developing gastrointestinal immune system of neonates. Nutrient composition of canine and feline milk samples has been described previously, but little is known about the oligosaccharide content. Therefore, the objective of this study was to characterize canine and feline milk samples using a high-throughput glycomics approach. 23 dogs (9 Labrador retriever and 14 Labrador retriever x golden retriever crossbreed) and 6 domestic shorthair cats were recruited to the study. Milk samples were collected by manual expression at time points after parturition. Samples were collected across 2 phases per species, differentiated by maternal diet. Following extraction, oligosaccharide content was determined by liquid chromatography-mass spectrometry (LC-MS). In canine milk samples, 3 structures accounted for over 90% of all oligosaccharides detected across two diet groups. These were 3'-sialyllactose, 6'-sialyllactose, and 2'-fucosyllactose. In feline samples, a more diverse range of oligosaccharides was detected, with up to 16 structures present at relative abundance >1% of the total. Difucosyllactose-N-hexaose b, 3'-sialyllactose and lacto-N-neohexaose were all detected at abundances >10% in feline milk samples. Statistically significant differences (p<0.05) in oligosaccharide abundances were observed between collection time points and between diet groups within species. These data explore the oligosaccharide content of canine and feline maternal milk, representing an opportunity to generate a fundamental understanding of the nutritional needs of new-born puppies and kittens.

Fig 1. Example data obtained using HPLC Chip/TOF-MS to determine glycan signal in canine milk.

All known compounds were extracted, overlaid and annotated, and were structurally identified using an in-house library. Each colour indicates a different glycan class–dark blue (undecorated neutrals), red (fucosylated), green (sialylated), purple (fucosylated and sialylated) and light blue (sulfated).

Fig 2. Mean normalised relative abundances of feline milk oligosaccharides.

Proportion >1% for phase 1 and phase 2. Maternal diets: Phase 1 diet = Iams^® Kitten, Phase 2 diet = Royal Canin^® Feline Health Nutrition™ Mother & Babycat.

Fig 3. Mean normalised relative abundances of canine milk oligosaccharides.

Proportion >1% for phase 1 and phase 2. Maternal diets: Phase 1 diet = Eukanuba^® Premium Performance, Phase 2 diet = Royal Canin^® Maxi Starter.

Fig 4. Estimated mean (95%CI) normalised abundance for the ‘Early’, ‘Mid’ and ‘Late’ time category groups of the feline milk oligosaccharides.

Present at >5% of the total during the course of lactation. Asterisk bars indicate statistically significant differences within a diet group (p<0.05).

Fig 5. Estimated mean (95%CI) normalised abundance for the ‘Early’, ‘Mid’ and ‘Late’ time category groups of the canine milk oligosaccharides.

Present at >5% of the total during the course of lactation, plus LNnT in addition. Asterisk bars indicate statistically significant difference within a diet group (p<0.05).