Cobalt and vitamin B12 supplementation of young sheep.

Abstract

Proc. Aust. Soc. Anim. Prod. Vol. 19 COBALT AND VITAMIN B12 SUPPLEMENTATION OF YOUNG SHEEP G. J. JUDSON, R. K. TURNBULL and B. R. KEMPE South Australian Dept of Agriculture, Box 1671 GPO Adelaide, S.A. 5001. SUMMARY The efficacy of 4 treatments in maintaining adequate plasma and liver vitamin B lz (B,,) concentrations was compared in young sheep grazing a cobalt (Co)-deficient site in the south east of South Australia. The treatments were injections of Blz or an intraruminal glass pellet containing Co prior to weaning and at weaning intraruminal glass pellets or Co pellets. A liveweight and fleece weight response was obtained to treatment. The intraruminal pellets maintained normal B,, status of sheep grazing Co-deficient pasture for about 1 year. Keywords: sheep, vitamin B12, cobalt supplements, fleece weight, liveweight. INTRODUCTION In South Australia, cobalt deficiency in sheep is widespread although severe Co deficiency is usually restricted to the coastal regions (Reuter et a2. 1988). The Co is required for the synthesis of Br2 by the ruminal micro-organisms and it is the vitamin that is required by the host tissues. However, in animals grazing phalaris a continuous supply of Co in the rumen is desirable since the prevention of phalaris staggers seems to reflect an independent role of Co in ruminal detoxification. For the prevention of Co deficiency in sheep it is generally recommended that subcutaneous injections of B12 be administered to lambs, commencing at tail docking and castration (marking), and Co intraruminal pellets at weaning for long-term protection (Reuter et al. 1988). The development of soluble glass pellets containing Co offers an alternative method of preventing Co deficiency in sucking and weaner sheep (Knott et al. 1985). In this study these various supplements were tested for their effectiveness in providing B12 to young sheep grazing a Co deficient pasture. MATERIALS AND METHODS An experiment was undertaken on ground-water rendzina soils near Naracoorte, South Australia. On 26 July 1984, Merino lambs at marking (week 0 of the experiment) were blocked within sex into groups of similar liveweight. From each block, lambs were allocated to 5 treatment groups, each of 7 wethers and 7 ewes, namely: Control - no B 12 or Co treatment; B 12KoP - 2 mg B 12 subcutaneously at week 0 and a 10 g Co pellet at weaning (week 11); B 12/GlP - 2 mg B12 at week 0 and a 34 g glass pellet at weaning; LGlP/GlP - a 17 g glass pellet at week 0 and a 34 g glass pellet at weaning, and LGlP - a 17 g glass pellet at week 0. The Co pellet which contained 30% by weight Co304 (Formula E, Top Australia Ltd) was given orally with 2 steel grinders. The soluble glass pellets (Cosecure, Chance Pilkington Ltd) contained by weight 13.4% copper (Cu), 0.3% selenium (Se) and 0.5% Co. The lambs were run as 1 mob until the experiment was terminated at week 67 when sheep were shorn. Sheep were weighed at frequent intervals (Table 1). At each weighing, blood samples for B12, Se and Cu assay were collected from 4 wethers and 4 ewes from each treatment group into heparinised containers: liver biopsies for B12 assay were also obtained from these sheep at weeks 11,25, 38,50 and 66. Vitamin B12 assays were as described by Judson et al. (1988). The liveweight and B12 results were subjected to a split-plot analysis of repeat measures with the main plot stratum being sex x sheep x treatment and the subplot stratum being sex x sheep x treatment x time. The plot of residuals against fitted values revealed heterogeneity for plasma B12 values. A loglo transformation was therefore performed and the analyses repeated. Vitamin B12 concentrations given in Table 1 are arithmetic means. Fleece weights were tested by 2-way analysis of variance using sheep as the block. Difference between treatment means was tested using the least significant difference test. RESULTS Table 1 gives the mean liveweights and plasma B12 concentrations for each treatment group. Significant (P < 0.001) treatment x time and sex x time interactions were observed for liveweight. An increase to treatment was observed at weeks 25, 59 and 66. At week 66, mean liveweights for the B 12/CoP and B 12/GlP groups were similar and greater than those of the LGlP/GlP and LGlP groups: these latter groups were similar and greater than the mean liveweight of the Control group (Table 1). The mean liveweight of wethers (45 kg) was significantly greater (P ~0.05) than ewes (41 kg) at week 66. Treatment had a significant effect (P < 0.01) on fleece weight of sheep. The mean fleece plus belly 378 Proc. Aust. Sot. Anim. Prod. Vol. 19 Table 1. Liveweight (kg) and plasma vitamin B12 concentrations (pmoWL) in sheep given different cobalt and vitamin B12 supplements @M/COP, B12 at mating + Co pellet at weaning; BWGIP, at marking + glass Co pellet at weaning; LGWGIP, glass Co pellet at marking and again at weaning; LGW, glass Co pellet at weaning) Mean values are for 14 sheep (liveweight) and 8 sheep (vitamin B12). Means followed by the same letter within each column are not significantly different at P = 0.05 weight (kg) for the Control, B 12/CoP, B 12/GlP, LGlP/GlP and LGlP treatment groups were respectively 3.8,4.1,4.4,4.2 and 4.1 (s.e.d. = 0.18). A significant (PC 0.001) treatment x time interaction was observed for plasma B12. The lamb glass pellets increased the mean values at week 5 and this increase was maintained at week 11 (weaning). There was no clear indication of a raised mean plasma B12 concentration at weeks 5 and 11 in response to the B12 injection (Table 1). From week 11 the mean plasma B12 values were raised above the corresponding values for the Control group at all stages of the experiment for the B 12/CoP, B 12/GlP and LGlP/GlP groups and up until week 59 for the LGlP group. A significant (P< 0.05) sex x treatment x time interaction was observed for liver B12 concentrations. Table 2 gives the mean values for each sex within each treatment group. Significant increases in the mean liver B12 concentrations were usually observed at weeks 25,38 and 50. Except for the LGlP group there was no consistent difference between sex within treatment. In the LGlP group mean liver B12 concentrations were greater (P < 0.05) in ewes than in wethers at weeks 25 and 50. Mean plasma Cu and blood Se concentrations for each of the treatment groups were greater than 8 pal/L and 0.5 ~.trnol/L respectively at all samplings indicating that the sheep were not at risk of Cu or Se deficiency during the experiment (Judson et al. 1987). Table 2, Liver vitamin B12 concentrations (nmol/kg wet weight) of sheep given different cobalt and vitamin B12 supplements (BKYCoP, B12 at mating + Co pellet at weaning; BlZGlP, at marking + glass Co pellet at weaning; LGWGlP, glass Co pellet at marking and again at weaning; LGIP, glass Co pellet at weaning) Mean values of 4 sheep For each column, means followed by the same letter are not significantly different at P = 0.05 379 Proc. Aust. Sot. Anim. Prod. Vol. I9 DISCUSSION In this study the mean B12 concentrations in plasma and liver of sheep in the Control group indicate that Co intake was inadequate at most stages of the experiment, particularly during late winter to spring (weeks O-l 1 and 50-66). Mean values indicative of normal B12 status in sheep are greater than 400 pmol/L plasma and 200 nmol/kg fresh liver (Judson et al. 1987). The low B12 status of the Control group was associated with depressed growth rate and probably depressed wool production. Shallow et al. (1989) reported that wether lambs were more susceptible than ewe lambs to Co deficiency. There was no evidence in the present study of a sex effect in response of liveweight to Co although liver B12 concentrations differed between sex within treatment groups at times during the experiment (Table 2). The 17 g glass pellet maintained normal B12 status of sheep for almost 1 year and the additional treatment of a 34 g glass pellet at weaning had only a marginal benefit in maintaining normal B12 status of sheep. This and other studies (see Judson et al. 1988) indicate that the soluble glass pellet is an alternative treatment for providing Co to sheep. However, these pellets are not available on the Australian market and there have been problems with the commercial production of these pellets in Great Britain (Judson et al. 1988). A suggested treatment regime for sheep retained on Co deficient pasture is to administer B12 injection at marking and an intraruminal Co pellet at weaning. The lack of a response in plasma B12 concentrations 5 weeks after an injection of B12 to lambs (see Table 1) is consistent with other studies indicating that plasma Br2 concentrations were unreliable as indicators of B12 status in sheep given such injections (Judson et aZ. 1989). Dewey et al. (1969) showed that 1 Co pellet with or without a steel grinder or 2 Co pellets in the rumen were effective in maintaining adequate B12 status for more than 5 years in penned sheep given a Co deficient diet. In those studies the pellet contained 60% by weight Co304. In the late 1970' the Co304 content of the commercially available pellets was reduced to 30%. s The present study indicates that 1 of these pellets was effective in maintaining normal liver B12 reserves for the period of the experiment (55 weeks after dosing) but not normal plasma B12 concentrations. As plasma B12 concentrations in sheep are more responsive than liver B 12 to current intake of Co (Sutherland 1980) this suggests that Co availability was marginal towards the end of the experiment (see Table 1). Millar and Albyt (1984) reported that the Co pellet, containing 30% by weight Co304, maintained raised serum and liver B12 concentrations in sheep for only about 14 weeks whereas Masters and Peter (1990) showed that the pellet was effective for at least 54 weeks in maintaining raised plasma B12 concentrations. These differences in the effective life of the Co pellet may be due in part to different brands or batches of the pellet. Further studies are needed to determine the effective life of the current Co pellet. The present findings suggest that a Co pellet may have to be given annually to maintain normal B12 status of sheep grazing Co deficient pasture. ACKNOWLEDGMENTS The skilled technical assistance of MS W. J. Babidge, MS R. Coventry and MS J. Kelly are greatly appreciated. This work was supported by a grant from the Australian Meat and Livestock Research and Development Corporation. We thank Mr P. Hood, Boo1 Lagoon for his co-operation in providing sheep and facilities. DEWEY, D. W., LEE, H. J. and MARSTON, H. R. (1969). Aust. J. Agric. Res. 20: 1109-16. JUDSON, G. J., BROWN, T. H., KEMPE, B. R. and TURNBULL, R. K. (1988). Aust. J. Exp. Agric. 28: 299-305. JUDSON, G. J., CAPLE, I. W., LANGLANDS, J. P. and PETER, D. W. (1987). In ` Temperate Pastures: their Production, Use and Management.' (Eds J. L. Wheeler, C. J. Pearson and G. E. Robards.) pp. 377-85. (Australian Wool Corporation-CSIRO:Melboume.) Trace Elements in New Zealand: Environmental, JUDSON, G. J., SHALLOW, M. and ELLIS, N. J. S. (1989). In ` Human and Animals' (Eds R. G. McLaren, R. J. Haynes and G. P. Savage.) pp. 225-9. (Lincoln College Printer-y: Lincoln Canterbury.) KNOTT, P., ALGAR, B., ZERVAS, G. and TELFER, S. B. (1985). In ` Trace Elements in Man and Animals - TEMA 5' (Eds C. F. Mills, I. Bremner and J. K. Chesters.) pp. 708-13 (Cwealth. Agric. Bur.: Slough). MASTERS, D. G. and PETER, D. W. (1990). Aust. J. Exp. Agric. 30: 33741. MILLAR, K. R. and ALBYT, A. T. ( 1984). N. 2. Vet. J. 32: 105-8. REUTER, D. J., CARTWRIGHT, B., JUDSON, G. J., McFARIANE, J. D., MASCHMEDT, D. J. and ROBINSON, J. B. (1988). Technical Report No. 139, Depart. Agriculture, South Australia. SHALLOW, M., ELLIS, N. J. S. and JUDSON, G. J. (1989). Aust. Vet. J. 66: 250-l. SUTHERIAND, R. J. (1980). N. 2. Vet. J. 28: 169-70. REFERENCES 380