The effect of timing of mineral supplementation of the ewe diet in late pregnancy on immunoglobulin G absorption by the lamb

Abstract

Two experiments were carried out to examine the effects of the timing and duration of mineral supplementation of the ewe's diet in the final 6 weeks of gestation on immunoglobulin G (IgG) absorption by their progeny. In experiment 1, 60 single-bearing ewes were allocated to one of four dietary treatments (no. = 15) and offered a basal diet of grass silage ad libitum, containing 50 g/kg molassed sugar-beet pulp, which was supplemented with concentrates for the final 7 weeks of pregnancy and were additionally provided with a daily mineral/vitamin supplement for the final 6 weeks (W-6), 4 weeks (W-4), 2 weeks (W-2) or no mineral/vitamin supplement, (control; W-0). The supplement contained Ca, P, Na, Mg, Mn, Zn, Se, Co, I and vitamin E and was offered at the daily rate of 48 g per ewe. The ewes were milked at 1, 10 and 18 h post partum and measured quantities of colostrum, proportional to birth weight were fed back to the progeny via a stomach tube. At each milking, colostrum yield was recorded and colostrum samples taken to determine the concentration and yield of IgG. Treatment had no effect (P > 0.05) on the yields of colostrum or IgG to 18 h post partum. The efficiency of IgG absorption was lower (P < 0.001) in the progeny of ewes who received supplementary minerals (W-6, 0.069, W-4, 0.078, W-2, 0.072, W-0, 0.261; s.e. 0.0244. P < 0.001) regardless of the duration of the mineral/vitamin supplementation period and this resulted in a reduced concentration of IgG in the lamb's serum. In experiment 2, 40 twin-bearing ewes were allocated to one of four dietary treatments (no. = 10) and offered a basal diet of grass silage ad libitum which was supplemented initially with 500 g of a concentrate containing 140 g crude protein (CP) per kg from day 98 to 133 of gestation and then replaced with 700 g/day of a concentrate containing 180 g/kg CP from day 134 of gestation until lambing, in addition to one of the following mineral/vitamin supplementation treatments : no supplementary minerals, W0 (control); 48 g of supplement per ewe per day in weeks 6 and 5 pre- partum (W6–5), or weeks 4 and 3 pre-partum (W4–3), or for the final 2 weeks pre-partum (W2–1). The ewes were milked and the lambs fed as in experiment 1. Again, treatment had no effect (P > 0.05) on the yields of colostrum or IgG to 18 h post partum. When ewes were offered the mineral/vitamin supplement in the final 2 weeks of gestation their progeny had a lower (P < 0.01) serum IgG concentration (4.6 g/l) than in the control treatment (14.0 g/l) or when the supplement was offered either in weeks 3 and 4 (11.3 g/l) or weeks 5 and 6 pre-partum (14.3 g/l). IgG absorption efficiency followed the same pattern as lamb serum IgG concentration. We conclude that supplementation of the ewe's diet at the level used in these studies for the final 2 weeks of pregnancy results in the production of offspring with a reduced ability to absorb colostral IgG. Furthermore, in order for this impairment of the IgG absorptive ability of the lamb to manifest itself the supplementation must occur for the final 2 weeks of gestation and supplementation for a 2-weekly period earlier in gestation will not elicit the same effect.

Effect of High Iodine Intake on Selected Parameters of Immunity in Sheep

“…These results are consistent with results of many studies that have recently demonstrated the negative effect of iodine on plasma immunoglobulin concentrations in lambs (13). In experiment conducted by Rose et al (19) after application of high doses of iodine (5.5-21 mg/kg dietary DM), a significant decrease in IgG in blood plasma within 24 h post partum was observed.…”

Effect of the level of iodine in the diet of pregnant ewes on the concentration of immunoglobulin G in the plasma of neonatal lambs following the consumption of colostrum

“…A number of studies have recently demonstrated the negative effect of I on plasma Ig concentrations in lambs, albeit at supplementation rates substantially higher than those of the present experiment (Boland et al 2004;Crosby et al 2004;Guinan et al 2005). In agreement with the present study, Boland et al (2005) demonstrated that I fed at 17•7 mg/d to pregnant ewes in the lead-up to lambing suppressed the plasma concentration IgG in the lambs after colostrum feeding, but that when the I was fed at 8•9 mg/d, there was no significant effect, relative to a basal diet assumed to provide less than 1 mg I/d.…”

The importance of the gestation period for welfare of lambs: maternal stressors and lamb vigour and wellbeing

“…Cross-fostering established that the depression in lamb plasma IgG occurred because of a reduced ability of the lamb to absorb IgG and was specifically a dose-dependent effect of ewe I intake. The depression in IgG absorption was part of a more general disruption of absorption (Boland et al 2006) and the critical period was the last 2 weeks before parturition (Guinan et al 2005; Boland et al 2008). The mechanism for the disruption in IgG absorption in the lamb is unclear but links with thyroid hormone metabolism are likely (Rose et al 2007; Boland et al 2008).…”