Effect of Dietary Energy Level during Late Gestation on Mineral Contents in Colostrum, Milk, and Plasma of Lactating Jennies.

Simple Summary: Donkey milk is recognized as a functional food due to its high whey protein content. It is especially beneficial for newborn nutrition because of its nutritional similarities to human milk and its hypoallergenic properties. It can be used to prevent hypercholesterolemia and atherosclerosis. However, donkey lactation is less productive in terms of liters/d than dairy cow lactation. It has been suggested that the energy content of the diet in late pregnancy is the main factor influencing the composition of postpartum colostrum in dairy animals. However, research on the influence of dietary energy in late gestation on the mineral content of postpartum jenny milk is limited. Therefore, this study aimed to investigate the effect of dietary energy levels during late gestation on mineral contents in the colostrum milk of lactating jennies. The results showed that appropriately increasing dietary energy levels in late gestation increased the concentrations of Ca, P, K, Mg, Cu, Fe, Zn, and Mo in milk, but high dietary energy levels showed the opposite effect. The concentrations of these minerals in jenny milk decreased with the duration of lactation. This study investigated the effects of dietary energy levels during late gestation on mineral content in the plasma, colostrum, and milk of jennies postpartum. Twenty-four pregnant multiparous DeZhou jennies, aged 6.0  ±  0.1 years, with a body weight of 292  ±  33 kg, an average parity number of 2.7  ±  0.1, and similar expected dates of confinement (74  ±  4 days), were randomly allocated to three groups and fed three diets: high energy (12.54 MJ/kg, HE), medium energy (12.03 MJ/kg, ME), and low energy (11.39 MJ/kg, LE). Blood samples were collected from the jugular vein of each jenny at time points of 0 h, 24 h, 48 h, 5 d, 7 d, and 14 d after parturition. Additionally, milk samples were collected through manual milking, and an analysis of the mineral content was conducted. The results showed that compared with HE, both ME and LE significantly increased the levels of calcium (Ca), phosphorus (P), zinc (Zn), selenium (Se), molybdenum (Mo), and cobalt (Co) in the plasma and Ca, P, magnesium (Mg), copper (Cu), manganese (Mn), Zn, selenium (Se), molybdenum (Mo), and Co in the milk of jennies postpartum (p < 0.05); ME also increased the levels of potassium (K), iron (Fe), and Mn in plasma and K and Fe in milk (p < 0.05). The levels of Ca, K, Mg, P, Fe, Cu, Mn, Co, Se, Zn, and Mo in plasma and milk gradually decreased with increasing postpartum time. Their contents were the highest at 0 h postpartum, rapidly decreased after 24 h postpartum, and declined to the lowest on day 14 postpartum. The interaction between dietary energy level and postpartum time showed that although the concentrations of the minerals Ca, P, K, Mg, Fe, Cu, Mn, Zn, Co, Se, and Mo decreased in jennies' plasma and milk in the treatment groups with different energy levels as postpartum time increased, the pattern of change was also influenced by dietary energy level. The influence of dietary energy level in late gestation on the mineral content of milk and plasma during the postpartum colostrum phase was higher than that during the milk phase. In conclusion, this study demonstrated that, under the current experimental conditions, the mineral content of the colostrum, milk, and plasma of jennies after parturition was dependent on the dietary energy level during late gestation. [ABSTRACT FROM AUTHOR]