Recovery and Viability of Mesquite Seeds Fed to Sheep Receiving 2,4-D in Drinking Water

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Abstract
Counted nos. of seeds of velvet mesquite (Prosopis juliflora var. velutina) were fed 2 Rambouillet ewes penned separately in cement-floored stalls. Seeds were fed on 6 separate occasions, each followed by a 7-day period during which all fecal pellets were removed daily and screened for seeds and seed fragments. All recovered seeds were tested for viability prior to and after mechanical scarification of seed coats. During the final three 7-day periods, 2, 4-D in the free acid form was added to the drinking water at a concn. of 100 ppm. Each ewe consumed approx. 1 gallon of water daily and suffered no apparent ill effects. Relationship between time elapsed after ingestion and no. of seeds eliminated was curvilinear. Greatest no. of seeds were eliminated on the 2d day and fewest on the 7th. Of the total seeds fed 31.9% were eliminated as whole intact seeds and the remainder were either wholly digested or eliminated as fragments. More than one-fourth (27.3%) of the total seeds eaten contained sound viable embryos when eliminated. Seeds recovered during 3 periods while sheep were receiving untreated drinking water showed an avg. immediate viability of 2.42% as compared with 1.84% for seeds recovered when sheep were receiving 2, 4-D in drinking water. Following scarification of seed coats viability of recovered seeds was 83.9% and 83.0%, respectively, for the same periods. Avg. viability of unfed seeds from the same lot was 6% and 94%, respectively, prior to and after scarification of seed coats. Chromotropic acid tests gave strong positive indication of 2, 4-D in the fecal pellets. Presence of 2, 4-D was further confirmed by marked inhibition of germinating velvet mesquite seedlings when grown in the same fecal material. Similar biological tests conducted after the fecal material had been exposed to the atmosphere in a greenhouse for 150 days showed that the pellets still contained phytotoxic quantities of 2, 4-D.