Recovery and Germination of Grass Seeds Ingested by Cattle

Seeds of bluebunch wheatgrass [Psuedoroegneria spicata (Pursh) A. Love] and Sandberg bluegrass (Poa secunda Presl.) were fed to Holstein heifers in different amounts to investigate the effects of seed feeding level and seed size on the recovery and germinability of passed seed. Animals were fed 60,000, 30,000,15,000, and 7,500 seeds of each species. Passed seeds were recovered from dungcollected daily over a 4-day period and tested for germinability. In general, recovery of the larger-seeded bluebunch wheatgrass and the smaller-seeded Sandberg bluegrass declined as seed feeding levels decreased from 60,000 to 7,500 seeds per animal, and as time after seed ingestion increased from 1 to 4 days. Total seed recovery over the 4-day period was greater for bluebunch wheatgrass at the 60,000 seed feeding level, similar for both species at the 30,000 seed feeding level, and greater for Sandberg bluegrass at the 15,000 and 7,500 seed feeding levels.Germinability of bluebunch wheatgrass seeds decreased with each additional day in the digestive tract, while germinability of Sandberg bluegrass seeds remained constant or increased with time. Germinability of both species tended to increase as seed feeding levels decreased from 60,000 to 15,000 seeds per animal. Sandberg bluegrass seeds had greater germinability than bluebunch wheatgrass at all seed feeding levels and collection dates. Recovered seeds had significantly lower germinability than noningested seeds for both species. Results showed that livestock have the potential for dispersing enough germinable seeds on degraded rangelands.