The application of a selenium fertiliser for the correction of marginal deficiencies in grazing sheep.

A commercial fertiliser, consisting of a poorly soluble barium selenate core with a coating of highly soluble sodium selenite, was evaluated in 2 trials for the provision of selenium (Se) to grazing sheep. The fertiliser was administered at a level of 1 kg per hectare to 3 of 6 kikuyu paddocks during 1995 and 1996 in Trial 1, while the other paddocks were left untreated. The Se status of SA mutton merino ram lambs, as reflected by whole blood, liver and kidney Se concentrations, was elevated (P < 0.01) for at least 5 months after application of the fertiliser. Whole blood and liver Se concentrations of animals grazing unfertilised control paddocks were indicative of a subclinical Se deficiency at times (<100 ng Se/ml whole blood and <300 microg Se/kg liver dry matter). In Trial 2, 4 of 7 paddocks on which an oat fodder crop was established were treated with the Se fertiliser during 1995 and 1997. The remaining 3 paddocks were left unfertilised as controls. Groups of 10-15 pregnant SA mutton merino ewes were introduced to these paddocks within 2 weeks of parturition. These ewes and their progeny utilised these paddocks for a mean (+/- SD) period of 41 +/- 8 days after parturition. The whole blood Se concentrations of these ewes and their offspring were elevated (P < 0.01) relative to their contemporaries utilising control paddocks. No suggestion of a subclinical Se deficiency was discernible in animals grazing control paddocks, although whole blood Se levels approached 100 ng Se/ml during 1997. The application of Se fertiliser did not result in improvements in ewe reproduction or lamb growth. There was a suggestion of an improvement (P = 0.21) in mean (+/- SE) lamb survival on paddocks receiving Se fertiliser compared to control paddocks (71.5 +/- 4.6% vs 62.2 +/- 5.3% respectively).

The effect of selenium supplementation during the early post-mating period on embryonic survival in sheep.

The effect of selenium (Se) supplementation of ewes with blood Se concentrations ranging between 100-200 ng/ml on embryonic survival during the early post-mating period (days 15-35) was studied in 4 trials. In the 1st 2 trials 137 ewes were used in 1991 and 118 in 1992. After being mated as a single flock, these ewes were stratified randomly into 3 groups. One group served as a control, the 2nd was injected with 1 ml Deposel (containing 50 mg Se as Ba selenate) and the 3rd group injected with 1 ml containing 1 mg Se as Na selenite. During 1991, supplementation was administered immediately after the mating period. It was postponed by 14 days in 1992. Parenteral Se supplementation reduced (p < 0.10) the number of ewes that lambed by > 19% during 1991 but not during 1992. The number of ewes producing twins was unaffected. In Trials 3 and 4 there was a consistent indication that parenteral Se supplementation of pregnant ewes between 15-35 days after mating resulted in a reduced (22-40%) embryonic survival rate, although significant (p < or = 0.10) differences were only observed after the pooling of treatments receiving parenteral Se supplementation. Drenching of ewes with 50 mg Se as Na selenite resulted in a similar tendency. Biochemical appraisal of the blood, kidney and liver Se status of ewes failed to reveal toxic levels. The possible mechanisms involved in impaired embryonic survival are unclear. Supplementation of ewes during the 1st month of pregnancy with parenteral Se preparations is not recommended.

Parenteral copper and selenium supplementation of sheep on legume-grass pastures: biochemical and production responses in lambs to maternal treatment.

Liver and kidney copper (Cu) and selenium (Se) concentrations were studied over a 7-month period after parenteral supplementation using Cu heptonate and barium (Ba) selenate in 44 8-month-old South African (SA) Mutton Merino wethers. Responses in plasma Cu and blood Se concentrations, as well as fecundity were also measured in a breeding flock of SA Mutton Merino ewes for 3 consecutive years. The effect of maternal supplementation with Cu and Se was assessed in terms of biochemical parameters and production responses in 654 lambs produced by these ewes. Parenteral treatments with Cu and Se raised liver and kidney concentrations (P < or = 0.05) for up to 7 months in wethers under conditions where liver Cu and Se respectively declined to concentrations below 30 mg/kg DM and 300 micrograms/kg dry matter (DM) in spring. Plasma Cu concentrations of breeding ewes which received Cu heptonate were increased (P < or = 0.05) by 18% relative to the control group in which concentrations declined to 91 micrograms/dl during late pregnancy. Blood Se concentrations of control ewes exceeded 200 ng/ml, and were unaffected by parenteral Se supplementation. Survival of progeny of Cu heptonate treated ewes tended (P < or = 0.10) to be improved by 13% (0.68 vs 0.60). This tendency was accompanied by generally higher (P < or = 0.10) plasma Cu concentrations of these lambs relative to control lambs at 10 - 20 and 45 - 55 d of age. Lambs of Cu supplemented ewes that died prior to weaning, had higher (P < or = 0.05) liver Cu concentrations than control group contemporaries.(ABSTRACT TRUNCATED AT 250 WORDS)

Production responses of sheep supplemented with copper, cobalt and selenium on kikuyu ryegrass pastures.

The copper (Cu) and selenium (Se) status of SA Mutton Merino ewes grazing kikuyu-ryegrass pastures was investigated by analysing blood and liver samples. The response of ewes to oral supplementation with Cu, Cobalt (Co) and Se as single elements, or in 4 combinations were simultaneously assessed in a 2 x 2 x 2 factorial experiment. Pastures grazed were low in Cu (less than 5 mg Cu/kg DM) except for the summer months, while pasture Se concentrations remained at concentrations less than 0,03 mg Se/kg DM for almost the entire period. Plasma Cu concentrations remained in excess of 80 micrograms/dl until pasture Cu concentrations decreased below 5 mg/kg DM. Blood Se concentrations generally reflected liver Se concentrations. Supplementation of ewes with 5 g Cu oxide needles (Embamin Copper LA, Rhône Poulenc) markedly increased (P < or = 0,01) hepatic Cu and plasma Cu concentrations. The monthly drenching of ewes with 5 mg Se as sodium selenite elevated blood Se concentrations to normal levels in excess of 100 ng/ml while ewes not supplemented with Se had blood Se concentrations indicative of a deficiency (50-100 ng/ml). Supplementation of ewes with Cu and Se elevated (P < or = 0,05) concentrations of these trace elements in the plasma and blood of their progeny. Supplementation of ewes with Cu and Se resulted in respective improvements (P < or = 0,05) of 5,3 and 4,8% in live mass during lactation, compared to contemporaries which did not receive either Cu or Se.(ABSTRACT TRUNCATED AT 250 WORDS)