Dietary nonstructural carbohydrates influence synthesis of mare milk carbohydrates and yield.
Abstract: Mare milk is the primary source of nutrients for neonatal foals and contains various carbohydrates. Milk oligosaccharides are complex carbohydrates that are resistant to enzymatic digestion and provide support for the immune system and developing microbiome in the neonate. However, factors influencing the synthesis of milk carbohydrates in the mare are not well understood. This study aimed to determine the effects of dietary nonstructural carbohydrate (NSC) on mare milk composition and yield. Thoroughbred mares were paired by age and last breeding date then randomly assigned to one of two dietary treatments at 319 d of gestation: a high NSC concentrate (43.9% NSC; n = 9; HC) or a low NSC concentrate (17.8% NSC; n = 7; LC). The mares were fed the concentrate feeds in addition to forage. Colostrum and milk samples were collected at the following time points postpartum: at parturition, 12 h, 3 d, 7 d, 14 d, and 21 d. Total milk carbohydrates (lactose and oligosaccharides) were analyzed using an infrared-based milk analyzer (MilkoScan FT+, Foss, Denmark). Milk oligosaccharides were separately quantified following defatting and deproteinization with chloroform and methanol, purification by solid phase extraction, and correction for residual lactose. Daily milk yield was measured at 6 and 7 d postpartum. Mixed model ANOVA with repeated measures was used to evaluate the effect of diet and time on milk components and total milk yield. Mares fed the HC concentrate tended to have higher total milk carbohydrates than mares fed the LC concentrate (P = 0.059). There was no main effect of diet on milk oligosaccharides (P = 0.34); however, this study was the first to report a change over time in total oligosaccharide concentrations in mare milk, which were highest after foaling and decreased over time (P = 0.002). Daily milk yield, on a body weight (BW) basis, was higher in mares fed the HC concentrate (2.30% of BW) compared with the mares fed the LC concentrate (2.04% of BW; P = 0.035). These results demonstrate the importance of the maternal diet to milk composition and production, and ultimately, the nutrients provided to the foal. Mare milk is the primary source of nutrients for neonatal foals and contains various carbohydrates. The primary carbohydrate is lactose, which is an important source of calories for foals. Milk also contains carbohydrates referred to as oligosaccharides. Oligosaccharides are chemically and structurally more complex than lactose and are believed to be important in the gastrointestinal development of neonates. While it is known that these milk carbohydrates are important, we still do not fully understand how a mare’s diet affects the production of these carbohydrates or how the concentration of oligosaccharides in milk changes over time. To answer these questions, mares were fed either a high-sugar and starch feed or a low-sugar and starch feed in addition to hay and pasture. Milk samples were collected, and their carbohydrate content was measured during the first 3 wk after foaling. The highest concentrations of oligosaccharides in mare milk were observed on the first day after foaling and then decreased by 1 wk after foaling. The mares fed the high sugar and starch feed produced more milk and their milk was higher in carbohydrates compared with mares fed the low sugar and starch feed, demonstrating the importance of the diet for mare milk composition.
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Publication Date: 2025-06-26 PubMed ID: 40570156PubMed Central: PMC12267143DOI: 10.1093/jas/skaf213Google Scholar: Lookup
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Summary
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Overview
- This study investigated how feeding mares different levels of nonstructural carbohydrates (NSC) affects the carbohydrate content and yield of their milk postpartum.
- Researchers found that a high NSC diet led to increased total milk carbohydrates and daily milk yield, while milk oligosaccharide levels were highest at foaling and decreased over time regardless of diet.
Background and Purpose
- Mare Milk Composition: Mare milk is crucial for neonatal foals, providing vital nutrients, especially carbohydrates such as lactose and oligosaccharides.
- Lactose: The main carbohydrate and key energy source for foals.
- Oligosaccharides: More complex carbohydrates that resist enzymatic digestion and support the foal’s immune system and gut microbiome development.
- Knowledge Gap: Factors influencing how mares synthesize these milk carbohydrates, particularly the impact of diet, were not well characterized.
- Research Aim: To determine how dietary nonstructural carbohydrate levels (i.e., sugar and starch) influence mare milk carbohydrate composition and milk production.
Methods
- Study Subjects: Thoroughbred mares paired by age and breeding date, assigned to either:
- High NSC concentrate diet (43.9% NSC; HC group; n=9)
- Low NSC concentrate diet (17.8% NSC; LC group; n=7)
- Diet: Concentrate feeds provided alongside forage (hay/pasture) from day 319 of gestation through postpartum period.
- Sample Collection: Colostrum and milk sampled at parturition, 12 hours, and days 3, 7, 14, & 21 postpartum.
- Milk Analysis:
- Total milk carbohydrates measured using infrared milk analyzer (MilkoScan FT+).
- Oligosaccharides quantified after chemical processing (defatting, deproteinization, purification) and correction for residual lactose.
- Milk Yield: Measured daily at 6 and 7 days postpartum and expressed relative to mare body weight.
- Statistical Analysis: Mixed model ANOVA with repeated measures to assess effects of diet and time.
Key Findings
- Total Milk Carbohydrates: Mares fed the high NSC (HC) diet tended to have higher total carbohydrates in milk than those on the low NSC (LC) diet (P=0.059), suggesting diet influences overall carbohydrate content.
- Milk Oligosaccharides:
- No significant main effect of diet on oligosaccharide concentration (P=0.34).
- Concentration highest immediately postpartum and significantly decreased over time (P=0.002), marking the first study to describe this temporal pattern in mare milk.
- Milk Yield: Daily yield relative to body weight was greater in HC-fed mares (2.30% BW) compared to LC-fed mares (2.04% BW) with statistical significance (P=0.035), indicating diet boosts milk production.
Conclusions and Implications
- The maternal diet, specifically the amount of nonstructural carbohydrates, positively affects the quantity and carbohydrate content of mare milk.
- High NSC intake leads to increased milk production and higher total carbohydrates, potentially providing more energy and nutritional support to neonatal foals.
- Milk oligosaccharide levels naturally decline in the first weeks after foaling regardless of diet, which may be important for immune and microbiome development timing in foals.
- Understanding how diet affects milk composition can help optimize feeding strategies for pregnant and lactating mares to improve foal health outcomes.
Cite This Article
APA
Pyles MB, Fowler AL, Crum AD, Hayes SH, Schendel RR, Lawrence LM.
(2025).
Dietary nonstructural carbohydrates influence synthesis of mare milk carbohydrates and yield.
J Anim Sci, 103, skaf213.
https://doi.org/10.1093/jas/skaf213 Publication
Researcher Affiliations
- Department of Agriculture and Natural Resources, University of Minnesota Crookston, Crookston, MN 56716.
- Department of Animal and Food Sciences, University of Kentucky, Lexington, KY 40546.
- Department of Animal and Food Sciences, University of Kentucky, Lexington, KY 40546.
- Department of Animal and Food Sciences, University of Kentucky, Lexington, KY 40546.
- Department of Animal and Food Sciences, University of Kentucky, Lexington, KY 40546.
- Department of Animal and Food Sciences, University of Kentucky, Lexington, KY 40546.
MeSH Terms
- Animals
- Horses / physiology
- Female
- Milk / chemistry
- Milk / metabolism
- Diet / veterinary
- Dietary Carbohydrates / metabolism
- Dietary Carbohydrates / administration & dosage
- Dietary Carbohydrates / pharmacology
- Animal Feed / analysis
- Oligosaccharides
- Animal Nutritional Physiological Phenomena
- Lactation
- Pregnancy
- Colostrum / chemistry
Grant Funding
- 7005427 / U.S. Department of Agriculture National Institute of Food and Agriculture Multistate
Conflict of Interest Statement
The authors declare no conflicts of interest.
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