LASALOCID AND PARTICLE-SIZE OF CORN GRAIN FOR DAIRY-COWS IN EARLY LACTATION .2. EFFECT ON RUMINAL MEASUREMENTS AND FEEDING-BEHAVIOR

The effects particle size of corn grain and the ionophore lasalocid on ruminal fermentation and feeding behavior of early lactation cows wer e examined. Eight multiparous and 4 primiparous cows in early lactatio n were fed diets (44% forage) with cracked or ground dried shelled cor n grain and with or without lasalocid (360 mg/d per cow). The experime nt was a replicated (n = 3) 4 x 4 Latin square design with 21-d period s and a 2 x 2 factorial arrangement of treatments. Ground corn decreas ed ruminal turnover time of starch, did not affect ruminal lactate con centrations, increased propionate, decreased the ratio of acetate to p ropionate, and decreased branched-chain fatty acids. The range of rumi nal pH within a day increased with ground corn, but mean pH was unaffe cted by treatment. Lasalocid increased lactate concentrations and did not affect the ratio of acetate to propionate. Lasalocid increased tot al time spent ruminating, and ground corn decreased ruminal con: tract ions. Lasalocid tended to increase water intake, and ground corn incre ased water intake. Interactions of lasalocid and particle size of the corn grain were observed for ruminal turnover time of starch and NDF, and ruminal pool size of acetate and total VFA.