Effect of temperature on food and water intake and rumen fermentation.

The purpose was to determine volatile fa t ty acid concentrations at normal (18 C) and high (35 C) ambient temperature, and to determine the effect of increasing the rumen temperature with an intraruminal heating coil in an 18 C ambient temperature. Four nonlactating, fistulated Holstein cows were placed in a climatically controlled chamber. Treatments were (18) ambient temperature ]8.2 C; (35) ambient temperature 35 C; (18-43) ambient temperature 18.2 C, intraruminal coil temperature 43.4 C; and (18-51) ambient temperature 18.2 C, intraruminal coil temperature 51.0 C. Analysis of variance indicated that significant differences (P < 0.05) for acetic, propionic, and butyric acids, rumen tenlperature, rectal temperature, feed intake, and water intake were observed. Cows subjected to 18.2 C ambient temperature~ but whose rumen temperatures were increased by intraruminal heating coils, consumed significantly less (P < 0.05) feed and water than cows subjected to the other treatments. The data indicate that lower ruminal volatile fa t ty acid concentrations which occur at high ambient temperatures cannot be explained by changes in ruminal temperature.