RESUMEN
The present study aimed to investigate the impact of initiating alfalfa supplementation at either 14 or 42 days 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 ± 0.92 kg) were selected for this study. After 7 d of adjustment period, six lambs were slaughtered at 14 d of age to establish a baseline control. The remaining 36 lambs were randomly allocated to two treatment groups, every three 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.
RESUMEN
The establishment of the rumen microbiota plays an important role in the rumen development. However, little is known about the effects of alfalfa supplementation time on rumen microbiota establishment. Here, a total of 42 Hu lambs, seven-day-old, were chosen for the study. After a week of adjustment, six lambs were sacrificed to establish a baseline. The remaining 36 lambs were randomly split into two groups: one receiving alfalfa hay at 14 days (EAF), the other at 42 days (LAF), both groups received milk replacer and starter pellets. Introducing alfalfa at 14 days of age significantly improved total dry matter intake between 28 and 42 days (p = 0.04) and average daily gain from both 14 to 28 days (p = 0.04) and 28 to 42 days (p < 0.01), but this effect disappears from 56 to 70 days (p > 0.05). At 42 days, the abundances of Naganishia, Ascochyta, and Neosetophoma in the EAF group were significantly higher (p < 0.05) than those in the LAF group (17.8% vs. 3.97, 10.89% vs. 1.77, and 1.27% vs. 0.09%, respectively). At 56 days, the abundances of Ascochyta, Wallemia, and Aspergillus in the EAF group were significantly lower (p < 0.05) than in the LAF group (3.53% vs. 16.40, 8.78% vs. 18.89, and 2.14% vs. 4.69%). At 70 days, Aspergillus abundance in the EAF group was significantly higher (p < 0.05) than in the LAF group (2.69% vs. 0.85%). The LEfSe analysis showed that Methanobrevibacter_smithii was the archaeal biomarker at 14 days in both groups. Methanobrevibacter_sp_AbM4 was enriched at 56 days in the LAF group. Compared to the LAF group, the specific fungal biomarkers in the EAF group included Sporobolomyces and Bullera at 14 days, Naganishia, Didymella, Cleistothelebolus, and Alloleptosphaeria at 42 days, Ascochyta, Neoascochyta, and Alfaria at 70 days. Correlation analysis results showed strong patterns of association both within and between archaea and fungi, which were influenced by alfalfa supplementation time. In summary, alfalfa supplementation at 14 days of age promotes the growth performance of lambs before weaning, and alfalfa supplementation timing significantly affects rumen archaeal and fungal communities and dynamical changes.
