Summary
In western Canada, anthropogenic rangeland disturbance (e.g. through pipe laying and well installation) is frequent. Revegetation of such sites is often hindered by cattle grazing. Fencing to protect establishing vegetation is expensive. Application of chemical cattle repellants may be more cost effective. This study (conducted on reclaimed sites within the Aspen Parkland region of central Alberta, Canada) determined whether certain repellents reduced grazing intensity on vegetation to which they were applied by comparison with untreated vegetation.
Three trials were conducted between 30 May and 28 August 1989 at sites of different time since reclamation (seeding) and vegetation type:
Trial A - 10 years since reclamation; vegetation: Kentucky bluegrass Poa pratensis and white clover Trifolium repens; cattle stocking rate 0.90 animal unit months(AUM)/ha;
Trial B - 2 years since reclamation; vegetation: timothy grass Phleum pratense and T.repens; stocking rate 0.76 AUM/ha;
Trial C - 3 weeks since reclamation; vegetation: crested wheatgrass Agropyron pectiniforme, slender wheatgrass A.trachycaulum, smooth brome Bromus inermis (a non-native grass considered invasive), cock’s-foot Dactylis glomerata, perennial rye-grass Lolium perenne, medick Medicago spp., P.pratense and T.repens;stocking rate 1.21 AUM/ha.
The efficacy of four repellants was evaluated: pregnant mares' urine, Hinder® (150 mg/ml ammonium soaps), Skoot® (120 mg/ml tetramethylthiuram disulfide), and Deer-Away Big Game Repellent® (37% putrescent egg solids). Two concentrations of each were sprayed onto 1 x 3 m treatment plots randomized within blocks (at least 10 m apart) replicated four to six times.
Vegetation canopy heights (used to assess grazing intensity) were measured (on 3-4 dates commencing 9-21 days after application i.e. between 15 June-28 August) by: i) resting a sheet of plastic laminate over the canopy; or ii) by lowering a sliding bar attached perpendicularly to a stick until it contacted the uppermost leaves. The height of the sheet or bar above the soil surface was measured.
Big Game Repellent at the higher concentration was the only repellent that reduced cattle grazing, canopies of treated plots being taller than controls on each measurement date in all trials (i.e. indicating grazing was reduced). At the end of each trial recording period, canopy heights were:
Trial A - (73 days after application) control 47 mm, treatment 69 mm;
Trial B - (33 days after application) control 52 mm, treatment 69 mm;
Trial C - (40 days after application) control 66 mm, treatment 78 mm.
Repellent effectiveness declined over time as canopy measurements became shorter. Actual practical use for grazing management has still to be proven.
Canopies of plots treated with pregnant mares' urine, Hinder or Skoot were generally similar to controls and effects did not differ between trials.
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