The effect of glycerol or rumen-protected choline chloride on rumen fermentation and blood metabolome in pregnant ewes suffering from negative energy balance

Abstract

The objective of this study was to investigate the counteracting effects of glycerol or rumen-protected choline chloride supplementation on rumen fermentation and the profile changes in blood metabolites in pregnant ewes suffering from negative energy balance. Eighteen pregnant Hu sheep with a gestation period of 100 days were used in the present study. Feed restriction was started from 100 days of gestation and lasted for 9 days. During the period of feed restriction, these sheep were randomly assigned to three groups: the control group (CON, n = 6), which received no supplementation, the glycerol group (GLY, n = 6), which received 40 mL of glycerol per day, and the rumen-protected choline chloride group (RPC, n = 6), which received 10 g of rumen-protected choline chloride per day lasted 9 days. All supplements were mixed with feed. The results showed that, compared to CON, glycerol supplementation decreased the proportion of acetate (P < 0.01) and increased the proportion of propionate (P < 0.01). The proportions of butyrate (P = 0.04) and valerate (P = 0.04) were higher in GLY than in RPC, but there was no significant difference in their proportions between GLY and CON. Blood β-hydroxybutyric acid concentration continuously increased in CON during the treatment period, while it remained stable in the ewes receiving glycerol or rumen-protected choline chloride. Glucose levels in the blood of ewes receiving glycerol or rumen-protected choline chloride were higher than those in CON (P = 0.01). Compared to CON, the levels of non-esterified fatty acids (NEFA) (P = 0.02) and very-low-density lipoproteins (VLDL) (P = 0.04) in the blood were increased in ewes that received rumen-protected choline chloride. Correlation analysis of the DEMs and rumen fermentation parameters showed a positive correlation between citric acid and phosphohydroxypyruvic acid (r = 0.61, P < 0.01), as well as between bilirubin and BHBA (r = 0.59, P < 0.01). d-Glucose have a positive correlation with propionate (r = 0.48, P = 0.02), while have a negative correlation with BHBA (r = −0.77, P < 0.01), 2-hydroxylauroylcarnitine (r = -0.53, P < 0.01), 2-octenoylcarnitine (r = −0.61, P < 0.01), and 3-hydroxydodecanoic acid (r = −0.60, P = 0.04). It is concluded that the supplementation of glycerol or rumen-protected choline chloride counteracted changes in metabolite concentrations in ewes that had been induced by feed restriction.