Initial timing of alfalfa hay supplementation manipulates blood parameters, rumen gene expression, and epithelial microbiota in pre-weaning lambs.

ABSTRACT

The present study aimed to investigate the impact of initiating alfalfa supplementation at either 14 d or 42 d of age on growth performance, blood parameters, rumen tissue gene expression, and epithelial microbiota in pre-weaning lambs. A total of 42 seven-day-old male Hu lambs (3.88 ±â€…0.92 kg) were selected for this study. After 7 d of adjustment period, 6 lambs were slaughtered at 14 d of age to establish a baseline control. The remaining 36 lambs were randomly allocated to 2 treatment groups, every 3 lambs were considered a unit, including fed milk replacer, starter pellets, and either alfalfa hay fed at 14 (EAF) or 42 d of age (LAF). Body weight and feed intake were recorded for lamb until 70 d of age. Blood samples, rumen tissue samples, and epithelial microbiota samples were collected from the lambs at 42, 56, and 70 d of age. The results indicated that average daily gain, starter intake, and total dry matter intake were greater in the EAF group compared to the LAF group from 14 to 42 d of age (P < 0.01), but no significant differences from 43 to 70 d of age or during the entire trial. Treatment and age interactively affected the alfalfa intake (P = 0.02) from 43 to 70 d of age. The concentration of serum immunoglobulin A (IgA) (P < 0.01) and the expression of the rumen gene insulin-like growth factor-1 (P < 0.01) were greater in the EAF group compared to the LAF group at 42 d of age. Furthermore, the concentrations of alkaline phosphatase (P = 0.03), albumin (P < 0.01), total protein (P = 0.03), urea (P = 0.04), lipopolysaccharide (P < 0.01), ß-hydroxybutyric acid (P = 0.02), interleukin-1ß (IL-1ß) (P < 0.01), IL-4 (P < 0.01), and tumor necrosis factor-α (P < 0.01) were affected by age. The abundance of Prevotella was lower (P < 0.05), whereas Megasphaera (P < 0.05) was greater in the EAF group compared to the LAF group at 42 d of age. The early addition of alfalfa promotes rumen epithelial microbiota colonization. In conclusion, this study demonstrated that alfalfa provision at 14 d of age promotes growth performance in lambs, but this effect disappeared at 43 to 70 d of age. Moreover, provision of alfalfa at 14 d of age enhances the immune response, promotes rumen tissue cell proliferation, and affects dynamical changes of rumen epithelial microbiota. Meanwhile, our findings showed that the rumen undergoes significant physiological challenges during the transition from a liquid diet to a solid diet.

Recent studies have shown that in pre-weaning ruminants, the addition of alfalfa hay is beneficial for growth and rumen development. However, the effect of alfalfa supplementation timing on the growth of pre-weaning lambs remains still unclear. This study aims to explore the growth performance, blood parameters, rumen epithelial microbiota, and rumen tissue gene expression in response to alfalfa supplementation starting from either 14 d or 42 d of age in pre-weaning lambs. Our results indicate that alfalfa supplementation at 14 d of age could increase the average daily gain, starter intake, and total dry matter intake, but did not persist over the long term. When compared with the consumption of alfalfa starting at 42 d of age, starting to consume alfalfa at 14 d of age could improve immune response and promote rumen tissue cells proliferation. Furthermore, the supplementation of alfalfa, starting at 14 d of age, not only increased the abundance of Megasphaera, but also affected dynamical changes in the rumen epithelial microbiota. Additionally, our findings suggest that the rumen undergoes significant physiological challenges during the transition from a liquid diet to a solid diet.