Improving lamb performance with sericea lespedeza and molybdenum

Improving lamb performance with sericea lespedeza and molybdenum

Summary

Prolonged feeding of sericea lespedeza (SL; Lespedeza cuneata) led to reduced serum concentrations of molybdenum, a co-factor in an enzyme complex that may contribute to weight gain. The objective was to determine the effect of Mo supplementation on changes in body weight (BW), and serum, fecal, urine and liver concentrations of trace minerals (TM) in lambs fed SL. Lambs weaned in May (84 ±1.5 d of age; 27 ± 1.1 kg) were blocked by BW and parasite resistance, and assigned randomly to be fed 900 g of 75% alfalfa pellets (CON; n = 10) or 75% SL pellets (n = 20) for 103 d. Within the SL group, half of the lambs were administered ~ 70 mg/lamb of sodium molybdate daily to ameliorate a reduction in serum molybdenum (SL+MO) observed previously. Supplements were isonitrogenous, isocaloric, and similar in TM. Serum was collected on d 28, 56, and 103, urine and feces on d 56, and a liver biopsy on d 104 to determine concentrations of TM (inductively coupled plasma-atomic emission spectroscopy). A mixed model was used for data analysis. Molybdenum drench increased serum (P < 0.001), liver (P < 0.001), and urine (P < 0.001) Mo to that of CON lambs, while that of SL lambs was markedly reduced. Fecal Mo was greatest in SL+MO followed by SL then CON lambs (P < 0.02). Serum concentrations of Co (P < 0.006) and Zn (P < 0.001) were reduced in SL compared with CON lambs, and Cu was greatest in CON followed by SL then SL+MO lambs (P < 0.001). Liver concentrations of Cu (P < 0.001), Mo (P < 0.001), Se (P < 0.004), and Zn (P < 0.03) were reduced in SL compared with CON lambs. Fecal Cu, Fe, Zn, and Co were reduced (P < 0.01) in SL compared with CON lambs, and Mn was reduced in SL+MO compared with CON lambs (P < 0.03). Urinary Co was reduced in SL compared with CON lambs (P < 0.03). Body condition score (BCS; P = 0.83) and BW (P = 0.13) were similar among diets (P = 0.13). Changes in TM of lambs, especially copper Cu, Mo, Se, and Zn could explain poor production reported in previous experiments.

Objectives/Performance Targets

Sericea lespedeza (SL; Lespedeza cuneata) is a plant grazed or fed to small ruminants for parasite control. Condensed tannins in SL may lead to unintended consequences such as changes in production. The objective was to determine the effect of SL with or without molybdenum supplementation on changes in body weight (BW), hematology, and serum chemistry in lambs. Thirty ram lambs weaned in May (84 ±1.5 d of age; 27 ± 1.1kg) were blocked by BW, breed, and parasite resistance, and randomly assigned to be fed 900 g of 75% alfalfa pellets (CON; n = 10) or 75% SL pellets (n = 20) for 103 d. Supplements were isonitrogenous, isocaloric, and similar in trace mineral concentrations. Within the SL group, half of the lambs were administered ~ 70 mg/lamb of sodium molybdate daily to ameliorate a reduction in serum molybdenum (SL+MO) observed previously. Lamb BW was obtained and blood collected every 14 d to determine hematological and serum chemical profiles. Data were analyzed using a mixed model with repeated measures. Mean packed cell volume (MCV), number of platelets, lymphocytes, monocytes, eosinophils, and hemoglobin were similar among diets (P > 0.10). White blood cell count (WBC; P < 0.05) and number of neutrophils (P < 0.001) were greater in CON than SL lambs. Red blood cell count (RBC) was greater in CON and SL+MO than SL lambs (P < 0.03). However, mean corpuscular volume (MCV; P < 0.08) and mean corpuscular hemoglobin (MCH; P < 0.06) tended to be greater in SL than CON lambs (P < 0.08). Serum concentrations of albumin (P < 0.001) and aspartate aminotransferase (AST; P < 0.003), were lower in SL than CON lambs. Serum concentrations of creatinine were greater for CON and SL+MO than SL lambs (P < 0.04), and total protein (TP) was greater in CON and SL than SL+MO lambs (P < 0.001). Serum concentrations of uric acid were similar among diets (P > 0.10). There was a treatment × time interaction for blood urea nitrogen (BUN) in that values  were greater in CON lambs between d 14 and d 42 than SL fed lambs, and otherwise similar (P < 0.001). Lambs BW was similar among diets (P = 0.13). Since most hematological and serum chemical profiles were within a normal range, any changes in animal health or production associated with condensed tannins in SL observed in previous studies likely were not related to these variables examined.

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