Effects of supplementing concentrates with different energy levels on growth performance, blood indicators, and fecal microbiota of Mongolian horses in late gestation

BACKGROUND: Horse breeding and management have a globally extensive history, with horses serving vital roles in transportation, warfare, agriculture, and cultural activities. In China, particularly in Inner Mongolia, the horse industry faces challenges such as harsh winters and limited nutritional research for local breeds, especially during late gestation. This critical period is essential for fetal development and maternal health, and inadequate nutrition can lead to complications like nutritional abortions and poor foal growth. Similar issues exist worldwide in cold climates or regions with seasonal pasture variations, emphasizing the need for comprehensive equine nutrition research. RESULTS: This study investigated the effects of supplementary feeding with concentrates of different energy levels-high (HEN), medium (MEN), and low (LEN)-on Mongolian broodmares during late gestation. Supplementation with MEN concentrate significantly improved the final body weight of mares, tended to increase average daily gain (ADG), and enhanced nutrient digestibility. Blood biochemical indicators showed that lactate dehydrogenase (LDH) activity was significantly higher in the MEN group compared to HEN and LEN groups, indicating enhanced anaerobic glycolysis. Conversely, aspartate aminotransferase (AST) activity was significantly lower in the MEN group, suggesting reduced hepatic or muscular stress. Antioxidant indices demonstrated reduced oxidative stress, with catalase (CAT) levels significantly higher and malondialdehyde (MDA) levels lower in the MEN group. Reproductive hormone analysis revealed that MEN supplementation increased follicle-stimulating hormone (FSH) levels, while the LEN group had significantly higher progesterone (P4) and estradiol (E2) levels. Fecal microbiota analysis indicated altered microbial community composition favoring beneficial bacteria, and metabolomic analysis revealed significant differences in metabolites related to energy metabolism and other physiological pathways. CONCLUSIONS: The study provides compelling evidence that medium-energy (MEN) concentrate supplementation is an effective nutritional strategy for late-gestation Mongolian broodmares, promoting maternal health, metabolic efficiency, and physiological homeostasis. These findings have global implications, offering insights to optimize broodmare nutrition worldwide, particularly in cold climates or regions with seasonal pasture shortages. By adopting similar strategies, breeders can enhance reproductive outcomes and contribute to the sustainable development of the horse industry on a global scale.