Relationship Between Plant Maturity and Foraging Experience of Lambs Grazing Hycrest Crested Wheatgrass

We compared the ingestive behavior of 8-week-old lambs experienced with either hycrest crested wheatgrass (Agropyron cristatum × Agropyron desertorum) or the shrub serviceberry (Amelanchier alnifolia) when they grazed on monocultures of vegetative or flowering hycrest crested wheatgrass growing in pots placed in the soil at ground level. A split block design was used to test for the main effects of plant maturity (vegetative or flowering) and experience (grass or shrub), and their interaction. Phenology affected ingestive behavior. Bite size (0.29 vs. 0.10 g per bite) and intake rate (4.2 vs. 3.3 g min−1) were higher (P \u3c 0.01), while bite rate (15 vs. 33 bites min−1) was lower (P \u3c 0.01) for lambs grazing flowering compared with vegetative grass. Experience also affected ingestive behavior. Grass-experienced lambs ingested grass faster (P\u3c 0.05) than shrub-experienced lambs (4.1 vs. 3.4 g min−1). Grass-experienced lambs had slightly higher bite rates (25 vs. 24 bites min−1) and took larger bites (0.21 vs. 0.18 g per bite), but differences were not statistically significant (P \u3e 0.05). The interaction between plant phenology and experience was not significant (P \u3e 0.05). Grass-experienced lambs were more (P \u3c 0.05) efficient ingesting both vegetative (3.6 vs. 3.0 g min−1) and flowering (4.6 vs. 3.7 g min−1) grass than shrub-experienced lambs. Shrub-experienced lambs failed more (P \u3c 0.05) at prehending flowering vs. vegetative grass (16 vs. 5%), while grass-experienced lambs did not (1.2 vs. 1.4%). We conclude that flowering grass was more difficult for lambs to ingest than vegetative grass, but these differences were offset by prior experience foraging on grass