Ovine White-Liver Disease (OWLD). Vitamin B₁₂ and Methyl Malonic Acid (MMA) Estimations in Blood

Abstract

At pasture outlet, mean plasma vitamin B₁₂ varied between 210 and 1,200 pmol/1 in 1 month old lambs, 19% of them had values below 250 pmol/1. In those put on OWLD pastures, mean values dropped after 2–4 weeks, and mostly stayed below 150 pmol/1 throughout grazing. Plasma methylmalonic acid (MMA) rose above 5 µmol/1 2–8 weeks after outlet, and above 15 µ-mol/1 4 weeks later. Reduced growth occurred 3–8 weeks after plasma B₁₂ dropped below 150 pmol/1, and 4–6 weeks after MMA rose above 5 µmol/1. Clinical OWLD was most often associated with plasma B₁₂ < 150 pmol/1 and MMA > 15 µmol/1. Cobalt fertilization of pastures induced satisfactory plasma B₁₂/MMA values for 3 succeeding years. Elevated plasma B₁₂ was found 3 weeks after Co pellet dosing. The use of Co lick resulted in large individual variations in plasma B₁₂/MMA.

The control lambs, which were healthy and grew well on pastures which some years contained marginal/deficient cobalt, had plasma B₁₂/MMA values which varied considerably. One year values indicated functional Co deficiency, but none developed OWLD, and growth was satisfactory, but less than other years. In these lambs, high MMA was not always associated with low B₁₂, or depressed growth. OWLD occurred in Co/B₁₂ deficient lambs, but Co/B₁₂ deficient lambs on other pastures did not develop OWLD.

Sammendrag

Ved beiteslipp hadde 19% av de månedsgamle lamma plasma vitamin B₁₂ under 250 pmol/1. Hos alle lam som ble satt på OWLD-beitene sank verdiene etter 2–4 veker, og var som regel under 150 pmol/1 iløpet av beiteperioden. Plasma methylmalonsyre (MMA) steg over 5 μmol/1 2–8 veker etter slipp, og over 15 μmol/1 4 veker senere. Redusert tilvekst kom 3–8 veker etter at B₁₂ var sunket under 150 pmol/1, og 4–6 veker etter at MMA steg til over 5 μmol/1. OWLD var som regel assosiert med plasma B₁₂ uder 150 pmol/1 og MMA over 15 μmol/1.

Koboltgjødsling av beitet ga tilfredsstillende plasma B₁₂/MMA hos lamma i 3 år etterpå. Ved dosering med koboltpellets var B₁₂ forhøyet 3 veker senere. Bruk av kobolt saltslikkestein resulterte i store individuelle variasjoner i plasma B₁₂/MMA.

Kontrollamma varierte sterkt mhp plasma B₁₂/M-MA. I 1986 indikerte verdiene funksjonell koboltmangel, men ingen utviklet OWLD, og veksten var tilfredsstillende, men noe mindre enn andre år. Hos disse lamma var ikke alltid høyt MMA korrelert til lavt B₁₂, eller til nedsatt vekst. OWLD forekom hos Co/B₁₂ deficitte lam, men Co/B₁₂ deficiette lam på andre beiter utviklet ikke OWLD.