title: Response to selenium supplementation of sheep grazing cultivated pastures in the Natal Midlands.
abstract: The response to selenium supplementation of sheep grazing cultivated pastures was investigated on different farms in the Natal Midlands, Republic of South Africa. Over a period of one year, a significant (P < 0.01) improvement of 18.2% in live mass gain and of 13.7 and 15.8% (P < 0.05) in greasy and clean wool production, respectively, was measured in response to selenium supplementation in young ewes at the Cedara Research Station. In ewes injected with a long-acting barium selenate product, the glutathione peroxidase (GSH-Px) activity in the erythrocytes was maintained at elevated levels, above that of the control group, for almost 2 years. On 6 private farms, mature ewes were dosed approximately 6 weeks before mating, with a long-acting intraruminal selenium pellet. On 2 of the farms, a significant improvement (P < 0.05) in fertility of ewes was observed with no response to supplementation in the birth mass, lamb growth rate, or in lamb mortality. The long-acting pellets maintained elevated erythrocyte GSH-Px activity in the ewes for approximately one year. Although sheep on some farms in the Natal Midlands responded to selenium supplementation, it seems advisable to establish the selenium status of a flock before embarking on a supplementation programme. The risk of an excessive selenium intake, through the inadvertent supplying of selenium in different feed sources, has been demonstrated and should be guarded against.
authors: Department of Animal Science, University of Natal, Pietermaritzburg, Republic of South Africa.
authors: J B
authors: JB
authors: Van Ryssen
authors: G D
authors: GD
authors: Bradfield
authors: S
authors: S
authors: Van Malsen
authors: J F
authors: JF
authors: De Villiers
mesh_terms: D000821:Animal Feed; D000818:Animals; D004912:Erythrocytes / Q000201:enzymology; D005260:Female; D005979:Glutathione Peroxidase / Q000097:blood; D012643:Selenium / Q000008:administration & dosage* / Q000097:blood; D012756:Sheep / Q000378:metabolism*; D013019:South Africa
chemical_list: D005979:Glutathione Peroxidase; D012643:Selenium