Vitamin B12 nutrition of foetal and newborn lambs.

Abstract

Animal Production in Australia VITAMIN B 12 NUTRITION OF FOETAL AND NEWBORN LAMBS C.G.HALPIN* and I.W.CAPLE* Cobalt deficiency in sheep is seen as an illthrift syndrome, particularly in the lamb flock, but in flocks affected with internal parasites or grazing poor quality pastures diagnosis of marginal deficiency has been difficult. Concentrations of serum vitamin B12 have been used to assess the cobalt nutrition of Victorian flocks (Halpin 1979). Serum B12 less than l.OOpg/l indicates that dietary cobalt intake may be inadequate (Sutherland 1980) but low serum levels may not always reflect the liver stores (Millar and Penrose 1980). There is limited information on how Bl2 levels change during growth in sheep. The aim of this experiment was to monitor plasma B12 in foetal and newborn lambs and examine the normal changes in Bl2 nutrition in a flock grazing pastures adequate in cobalt. Experiments were done on seven housed pregnant ewes and their catheterized foetal lambs during 30 days before birth, and on 10 ewes and their 17 suckling lambs at pasture for up to 150 days after birth. Heparinized plasma, liver, colostrum and milk samples were collected at intervals and analysed for vitamin B12 by a radioisotope dilution techniqu . Plasma concentration of B,2 in foetal lambs was less than 50% of that in In newborn lambs plasma Bl2 increased dramatically after they ewes (Fig-l). received colostrum. The high concentrations of B12 in colostrum decreased within 48 hours and plasma concentrations in suckling lambs reflected this reduced intake: by day 11, lamb plasma Bl2 had decreased to 0.40+0.05~g/l. It took 37 days before lamb B12 exceeded l.OOyg/l, and 150 days before they had concentrations similar to the ewes. Placental transfer of vitamin Bl2 does occur in sheep, although some partitioning between mother and foetus is evident. Colostrum is a drain on plasma B12 in the ewe, but provides an essential source of Blz for the lamb-Milk provides little Bl2 and plasma concentrations less than l.OO~g/l in lambs within the preruminant period are normal in flocks with adequate cobalt nutrition. These results have important implications in the diagnosis of cobalt deficiency in illthrifty lambs. Plasma vitamin B12 concentrations are not a reliable index of cobalt nutrition of preruminant lambs. HALPIN, C.G. (1979). Vic. Vet. Proc. 37:43. MILLAR, K.R. and PENROSE, M.W. (1980). N. 2. Vet. J. Z 28:97. SUTHERLAND, R.J. (1980). N. Z. Vet. J. Z 28:169. * Department of Agriculture, Attwood Veterinary Research Laboratory, Westmeadows, Vic. 3047. 658