Nf. Suttle et al., FAILURE OF MINERAL SUPPLEMENTATION TO AVERT APPARENT SODIUM DEFICIENCY IN LAMBS WITH ABOMASAL PARASITISM, Animal Science, 63, 1996, pp. 103-109
Two groups of 28 Finnish Landrace (FL) lambs were given (group Mg) or
denied (group O) access to a magnesium (Mg)-rich mineral mixture to es
tablish its role in the hitherto frequent development of diarrhoea in
the flock. Diarrhoea developed in most lambs but became marginally wor
se in group Mg (P < 0.05) by weaning. At weaning, 28% of the lambs had
salivary sodium:potassium (Na: K) ratios < 4 indicating Na deficiency
but pasture was not low in Na (60.9 mmol/kg dry matter (DM)) and prov
iding the mineral mixture (which also contained Na) did not alleviate
the deficiency. Raised plasma pepsinogen (PP) concentrations were indi
cative of abomasal parasitism and all lambs were drenched with levamis
ole. Groups were subdivided at weaning, either continuing on their pre
vious treatments (groups Mg/Mg and O/O) or being offered pure salt (Na
Cl) (groups Mg/Na and O/Na). Mineral consumption was measured from wea
ning and varied widely between groups and with time for the first 2 we
eks. Early consumption was maximal at 19.6 g per head per day in group
Mg/Mg and zero in group Mg/Mg and faecal DM was significantly lower i
n the former group (165 v. 223 (s.d. 16.9)g/kg DM). All groups showed
an improvement in Na status after weaning followed by a decline and Na
Cl consumption showed opposite changes about a mean of 6.3 g per head
per day: faecal DM became uniformly low (ca. 200 g/kg fresh weight) in
all groups. A further rise in PP prompted a second treatment with lev
amisole 6 weeks after weaning. When salivary Na:K was low (1 and 7 wee
ks after weaning), a significant relationship (P = 0.002) was found be
tween salivary K (mmol/l, faecal DM (g/kg) and plasma pepsinogen (PP U
per l): K=22.9+4.5 PP-0.047 DM (d.f. 82:r=0.34). Nematodiasis may hav
e caused an ion imbalance and an associated diarrhoea, inducing a crav
ing for NaCl which was ill-met by a mixture rich in laxative Mg.