The effect of Se-source and dosage on sheep requiring oxytetracyline treatment.

<p>Foot rot severity was assessed after 0, 20, 28, 40, and 60 wk of Se supplementation in ewes receiving no Se treatment, Na-selenate at a dosage rate of 8.95 mg Se/wk per ewe, or Na-selenite and Se-Yeast at 4.9, 14.7, or 24.5 mg Se/wk per ewe for 62 wk. If a sheep had one foot with a score of 4, or one foot with a score of 3 and a second foot with a score of 2 or greater, or if all 4 feet had FR, then 20 mg/kg oxytetracycline was administered subcutaneously (Liquamycin LA-200; Pfizer Animal Health, Exton, PA) at the 28- and 40-wk foot trimming sessions. No significant differences in parental oxytetracycline treatment were observed for individual treatment groups at 28 wk; however; more ewes with supranutritional Na-selenite treatment were treated with oxytetracyline than ewes receiving the lowest Na-selenite dosage (<i>P</i> = 0.05). At 40 wk, more ewes receiving Na-selenite at the highest dosage had to be treated with oxytetracycline than ewes receiving no Se, Na-selenite at both lower dosages, or Se-yeast at 14.5 mg/wk (all <i>P</i> ≤ 0.05).</p

The effect of Se-source and dosage on delayed-type hypersensitivity response to keyhole limpet hemocyanin (KLH).

<p>Delayed-type hypersensitivity (DTH) skin test responses was assessed after 52 wk of Se supplementation in healthy and footrot (FR)- affected sheep receiving no Se treatment, Na-selenate at a dosage rate of 8.95 mg Se/wk per ewe, or Na-selenite and Se-Yeast at 4.9, 14.7, or 24.5 mg Se/wk per ewe for 62 wk. (All Se treatment groups were combined.) <b>A</b>) Ear thickness response was not significantly affected by ewe FR status (<i>P</i> = 0.15). <b>B</b>) Ear wheal diameter response was decreased in FR-affected sheep (overall <i>P</i> = 0.03), which was significant only at 24 h (<i>P</i> = 0.007; <i>P</i>_Interaction = 0.05). C) Ear thickness response and D) ear wheal diameter response were not significantly affected by Se source or Se dosage.</p

The effect of Se-source and dosage on 30-min skin response to keyhole limpet hemocyanin (KLH).

<p>The 30-min skin test response following KLH challenge was assessed after 52 wk of Se supplementation in healthy and footrot (FR)-affected sheep receiving no Se treatment, Na-selenate at a dosage rate of 8.95 mg Se/wk per ewe, or Na-selenite and Se-Yeast at 4.9, 14.7, or 24.5 mg Se/wk per ewe for 62 wk. <b>A</b>) Ewes affected with FR had smaller 30 min ear-thickness responses to KLH intradermal injection than healthy ewes (overall <i>P</i> = 0.05). <b>B</b>) The 30 min ear-wheal diameter response was not significantly affected by ewe FR status or Se supplementation. <b>C</b>) Selenium dosage, but not Se source affected the ear-thickness response, as Se supplementation at lower dosages (8.95 mg/wk Na-selenate, 4.9 mg/wk Na-selenite, and 4.9 mg Se-yeast/wk) had smaller ear-thickness responses than supranutritional Se supplementation (14.7 and 24.5 mg/wk Na-selenite and Se-yeast; <i>P</i> = 0.01) or no Se supplementation (<i>P</i> = 0.01). <b>D</b>) Selenium dosage, but not Se source affected the ear-thickness response, as Se supplementation at lower dosages had or tended to have smaller ear-wheel diameter responses than supranutritional Se supplementation (<i>P</i> = 0.03) or no Se supplementation (<i>P</i> = 0.07).</p

The effect of Se-source on ex vivo neutrophil bacterial killing in sheep.

<p>Ex vivo neutrophil bacterial killing was assessed after 60 wk of Se supplementation in healthy and footrot (FR)-affected ewes receiving no Se treatment, Na-selenate, Na-selenite, and Se-Yeast for 62 wk<b>. </b><b>A</b>) Weekly oral Se drenching improved neutrophil bacterial killing in FR-affected ewes to percentages that were similar to healthy supplemented or healthy non-supplemented ewes. <b>B</b>) In FR-affected ewes, Na-selenate, Na-selenite, or Se-yeast improved neutrophil bacterial killing compared with no Se supplementation. The effect tended to be greater in ewes receiving Se-yeast compared with Na-selenite. The three dosages of Na-selenite or Se-yeast were combined because they did not differ. Different superscripts indicate group differences at <i>P</i> ≤ 0.10.</p

The effect of Se-source and dosage on antibody titers to keyhole limpet hemocyanin (KLH).

<p>Antibody titers to keyhole limpet hemocyanin (KLH) were assessed after 60 wk of Se supplementation in healthy and footrot (FR)-affected sheep receiving no Se treatment, Na-selenate at a dosage rate of 8.95 mg Se/wk per ewe, or Na-selenite and Se-Yeast at 4.9, 14.7, or 24.5 mg Se/wk per ewe for 62 wk. A) Weekly oral Se drenching improved KLH antibody titers in FR-affected ewes to titers that were similar to healthy ewes receiving no Se or healthy ewes receiving Se treatment. <b>B</b>) In FR-affected ewes, KLH antibody titers were greater in all Se-supplemented groups compared with the non supplemented group with the exception of the 24.5 mg/wk Na-selenite group. Different superscripts indicate group differences at <i>P</i> ≤ 0.10.</p

The effect of Se-source, Se-dosage, and foot rot status on serum-Se concentrations in sheep.

<p>Serum-Se concentrations were measured after 0, 14, 27, 40, and 54 wk of Se supplementation, and foot rot severity was assessed after 0, 20, 28, 40, and 60 wk of Se supplementation in ewes receiving no Se treatment, Na-selenate at a dosage rate of 8.95 mg Se/wk per ewe, or Na-selenite and Se-Yeast at 4.9, 14.7, or 24.5 mg Se/wk per ewe for 62 wk. Serum-Se concentrations for each treatment group are shown as separate bars for healthy sheep (lighter background) and for sheep with foot rot (darker background). At baseline (wk 0), no significant treatment group differences were observed; however, healthy ewes had higher serum-Se concentrations than ewes with FR (<i>P</i> = 0.01). After treatments started, group differences by foot-rot status subsided, whereas Se-source and Se-dosage affected serum-Se concentrations. Both healthy and FR-affected ewes that received no Se treatment had decreased serum-Se concentrations (<i>P</i> < 0.0001). Supranutritional Se-yeast supplementation increased serum-Se concentrations linearly with dosage (<i>P</i> < 0.0001), whereas ewes receiving supranutritional Na-selenite supplementation at 14.7 and 24.5 mg Se/wk achieved similar serum-Se concentrations as ewes receiving 4.9 mg/wk of Se-yeast.</p

Study design.

<p>Mature breeding ewes were randomly assigned to 8 treatment groups (n = 30 each; 15 healthy and 15 foot rot affected) for 62 wk based on Se source (no Se, inorganice Na-selenate, inorganic Na-selenite, and organic Se-yeast) and Se supplementation rate (0, 4.9, 14.7, and 24.5 mg Se/wk; Na-selenatate only at 8.95 mg/wk Se/wk)<b>.</b></p

Serum-Se concentrations (ng/mL) in ewes after weekly oral drenching with no Se, inorganic Se (Na-selenate or Na-selenite), and organic Se (Se-yeast) at varying supplementation rates (4.9, 14.7, and 24.5 mg Se/wk; Na-selenate only at 8.95 mg Se/wk) for 62 wk.¹

1<p>Adapted from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0082572#pone.0082572-Hall1" target="_blank">[1]</a>; numbers differ because all sheep are included here and classified as healthy or footrot-affected.</p>2<p>The largest SEM of the 8 treatment groups is shown.</p>3<p>Number of healthy sheep in each treatment group.</p>4<p>Least squares means.</p>5<p>Number of footrot-affected sheep in each treatment group.</p

The effect of Se-source on foot rot (FR) severity in sheep.

<p>Foot rot severity was assessed after 0, 20, 28, 40, and 60 wk of Se supplementation in ewes receiving no Se treatment, Na-selenate, Na-selenite, and Se-Yeast for 62 wk. All dosage groups were combined for each chemical source of Se treatment. The proportion of sheep (%) in each FR-severity category within each treatment group is shown (scale 0 to V; with no FR  =  0 being the lowest category). The scoring and categorization for FR is described in detail in the Materials and Methods. There were no consistent effects of Se source on FR prevalence and severity across time.</p

The effect of Se-source and dosage on foot rot (FR) severity in sheep.

<p>Foot rot severity was assessed after 0, 20, 28, 40, and 60 wk of Se supplementation in ewes receiving no Se treatment, Na-selenate at a dosage rate of 8.95 mg Se/wk per ewe, or Na-selenite and Se-Yeast at 4.9, 14.7, or 24.5 mg Se/wk per ewe for 62 wk. The proportion of sheep (%) in each FR-severity category within each treatment group is shown (scale 0 to V; with no FR  =  0 being the lowest category). The scoring and categorization for FR is described in detail in the Materials and Methods. There were no consistent effects of Se source and dosage on FR prevalence and severity across time.</p