Vitamin B12 is essential for normal growth in sheep, and is produced from cobalt in the rumen. Depending on the severity of the deficiency and age of the animal, vitamin B12 deficiency may be associated with a range of clinical signs, including reduced appetite, failure to thrive, reduced growth rate and wool production, anaemia, and weeping eyes.1
Cobalt deficiency has not been recognised in soils2 or in animals in the Goulburn area of the Southern Tablelands of NSW, yet there are claims locally that supplementing with vitamin B12 improves sheep productivity.
Vitamin B12 is available by injection, either alone or in combination with vaccines or anthelmintics. A dose of 2mg hydroxocobalamin by subcutaneous injection protects young sheep from depressed weight gain due to Vitamin B12deficiency for up to 14 weeks, although plasma B12 levels may begin to decline within two months.3
Parenteral products containing Vitamin B12 are readily available in rural merchandise stores throughout the district, and are widely promoted to sheep graziers. The addition of vitamin B12 increases the cost of a six antigen vaccination for sheep by about 95%, or by about 21c a dose.4
Results of an unpublished trial run in spring of 2007 in second cross lambs on a property at Gurrundah, 25km south of Crookwell, have been used by local rural merchants to support the sale of B12 products. This treatment-control trial of a couple of hundred lambs at marking reportedly showed a two kilogram advantage in favour of B12-treated lambs at weaning.5
The trial results were supported by the pub talk here, that B12 supplementation at marking causes lambs to heal up more quickly after mulesing, eliminates the tail in the mob at weaning, and reduces flystrike.
A second treatment-control trial was conducted on a property at Bannister, 17km south of Crookwell in spring 2009. The 232 Merino x Poll Dorset lambs were randomised into two groups prior to marking, at six weeks from the start of lambing. Half the lambs were vaccinated with Glanvac6® (Pfizer Animal Health) while the other half was vaccinated with Glanvac6 B12® (Pfizer Animal Health). The lambs were weighed 14 weeks later.
There was no statistical difference in liveweight between the two groups. The fact that the control group average was 0.6kg heavier than the treatment group highlighted the need to have either a much larger sample size, or to weigh all lambs both at the commencement and end of such a trial. Growth rate of these lambs reflected seasonal conditions, with a lower than expected growth rate of 210g per head per day.6
Four of thirty four cobalt supplementation trials in lambs in Western Australia produced a beneficial outcome. Responses were reported only on grass-dominant pastures in spring after above-average winter rainfall.7 With this in mind, vitamin B12 levels in crossbred lambs were measured on properties representative of the majority of soil types and localities in the Goulburn district at the end of spring 2010.
Spring pasture growth in the survey area exceeded normal in 2010. Legume content of the mainly improved pastures was negligible following years of drought conditions in the area. Blood samples were collected into lithium heparin tubes from ten crossbred lambs on ten properties at the time of weaning, as determined by each flock manager. The lambs varied in age between 14 weeks and 24 weeks. Breeds represented included second cross (BL/M x PD, BL/M x WS) and first cross (M x PD, Dohne x WS). Lambs were yarded on the day of sample collection, as fasting can increase B12 levels.1 Vitamin B12 is light-sensitive; samples were protected from light and consigned to the laboratory to arrive within 24 hours of collection.8 Only flocks where lambs had not received supplementary vitamin B12 were considered for the survey.
Vitamin B12 was determined by modified ECLIA by Regional Laboratory Services, Benalla. Results were reported in pmol/L. The normal range for B12 is reported to be between 400 and 5000 pmol/L; marginal levels are between 200 to 400 pmol/L, with deficient less than 200 pmol/L.8
The one hundred samples submitted returned B12 levels between 511 and >3100 pmol/L (Table 1). Only six of the samples tested had plasma B12 readings below 1000 pmol/L.
(Dam x sire)
|Predominant soil type||Location relative to Goulburn||Approximate age oldest lambs (wks)||Average B12
|# samples <1000 pmol/L|
|A||BL/MxWS||Grey loam||15km W||20||2097||1271-2693||0|
|B||D x WS||Shale||30km W||15||1530||511-2219||2|
Table 1. Vitamin B12 sample results for lambs from ten Southern Tableland flocks
Involvement in the small treatment trial highlights the need to have a substantial sample size for significant results (discussed further in these Proceedings by Helen McGregor).
The plasma B12 levels reported could be correlated with a treatment response trial to determine if the growth rate of lambs with vitamin B12 at the lower end of those results in the survey would improve with B12 supplementation.
The gender of the lambs sampled was not recorded. The mobs sampled were mixed sex, with both genders sampled on all properties except G, where only ewe lambs remained. Wethers are reported to be more susceptible than ewe lambs to B12 deficiency.9
Based on the accepted laboratory lower limit of normal Vitamin B12, no sheep in the mobs tested was vitamin B12 deficient, despite being raised in a bountiful spring.
Elizabeth Patrick BVSc provided the opportunity and technical support for the Vitamin B12 survey. Pfizer Animal Health funded the laboratory tests, and Tablelands LHPA funded the sample collection. Ten willing tablelands graziers provided the sheep and facilities for B12 sampling.
ECLIA Electrochemiluminescence immunoassay
Glanvac6® Multicomponent adjuvant vaccine against Corynebacterium pseudotuberculosis, Clostridium perfiringens type D, Cl. tetani, Cl. septicum, Cl. novyi, and Cl. chauvoei
pmol picomole (mole-12)
Sheep breeds: BL border leicester, D dohne, M merino, WS white suffolk, PD poll dorset