This paper reports on the effects of selenium supplementation on liveweight (LW), greasy fleece weight (GFW), fibre diameter (FD), impact of parasite infection and plasma glutathione peroxidase (GSH-Px) activity in weaned Merino sheep reared in a selenium-deficient area (blood GSH-Px < 40 U/g Hb). At weaning, 208 Merino wethers were assigned to two groups: control (CTRL) and treatment (SEL). The SEL group was injected with 0.5 mL of Deposel, a slow release selenium injection. LW, blood and faecal samples were taken at 6-week intervals over a 24-week period. At the end of the trial the animals were shorn and GFW and FD measurements were taken. The SEL group had significantly higher (P < 0.01) LW compared with the CTRL group at Weeks 6, 12, 18 and 24. There was a significant difference (P < 0.05) in GFW between the SEL and CTRL group, 2.93 and 2.75 kg, respectively. There was no difference in FD between the two groups. A trend (P < 0.06) towards lower faecal egg counts in the SEL group was seen but the difference between the two groups was not significant. As expected, the SEL group had significantly (P < 0.001) higher plasma GSH-Px activity compared with the CTRL group. In conclusion, selenium supplementation in weaned Merino sheep reared in a selenium-deficient area could increase the LW and GFW of the young sheep while perhaps reducing the level of parasitic infection.
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