# Small metabolites vary in sow milk across the course of lactation, while moringa supplementation and cooling sows exposed to heat stress conditions have limited effects

## TL;DR

Sow milk composition changes during lactation, but adding moringa or cooling sows under heat stress has limited impact on metabolite levels.

## Contribution

The study reveals dynamic changes in milk metabolites during lactation and evaluates the limited effects of moringa and cooling interventions under heat stress.

## Key findings

- Milk metabolite content varied significantly across lactation days, reflecting physiological changes.
- Diet and parity influenced D0 metabolites, while ECP affected D3 metabolites.
- Moringa and cooling had limited effects on milk metabolites under heat stress.

## Abstract

This study aimed to characterize changes in small metabolites in sow milk over the course of lactation. The impact of Moringa oleifera leaf powder addition to diet and electronic cooling pads (ECP) on milk metabolites of sow under moderate heat stress was also evaluated. A 2 × 2 factorial experiment was conducted with Yorkshire x Landrace sows (n = 48) from gestation day 100 to lactation day 21. Treatments included heat stress + control diet (HS + CS), heat stress + Moringa (HS + M), ECP + CS, and ECP + M beginning with 12 sows per treatment. Milk was collected on lactation days 0 (D0, colostrum), 3 (D3, transitional milk), and 14 (D14, mature milk). Metabolites were extracted using the Bligh and Dyer method and then profiled using exploratory multiple reaction monitoring. Milk metabolite content varied significantly across lactation days. Diet and parity influenced milk metabolites on D0, ECP on D3, and parity on D14. The 55 metabolites increased between D0 and D3, linked to phenylalanine, tyrosine and tryptophan biosynthesis, starch, sucrose and galactose metabolism, while the 93 decreased metabolites were associated with protein synthesis and gut development, including phenylalanine, tyrosine and tryptophan biosynthesis and alanine, aspartate and glutamate metabolism. Between D3 and D14, 148 metabolites increased and reflected alanine, aspartate and glutamate and galactose metabolism, while the 21 decreased included L-leucine, creatine, myo-inositol, hypoxanthine and acetyl-carnitine. The 116 metabolites impacted by parity in D0 samples, were elevated in primiparous compared to multiparous sows, and linked to arginine biosynthesis, amino acid metabolism, and purine metabolism. On D14, parity affected 52 metabolites related to alanine, aspartate and glutamate metabolism, arginine biosynthesis and pyrimidine metabolism. ECP on D3 reduced 104 metabolites involved in the citrate acid cycle, cysteine and methionine metabolism, and pyrimidine metabolism. Milk metabolite content changed significantly between the three phases of milk production, reflecting mammary secretory activity and potentially the changing nutritional needs of piglets and maternal physiological adjustments throughout lactation. These findings highlight the dynamic nature of milk composition and the potential for dietary and environmental interventions to modulate milk metabolite content under heat stress conditions.

This study shows how sow milk composition shifts throughout lactation and demonstrates that diet and cooling strategies can influence milk quality under heat stress, offering potential benefits for piglet growth and sow health.

Graphical Abstract