Effect of Diet and Ambient Temperature-Humidity on Ruminal pH, Oxidation Reduction Potential, Ammonia and Lactic Acid in Lactating Cows2

Diet and ambient temperature-humidity are major factors in an animal's environment. Little information is available on the effect of ambient temperature and relative humidity on ruminal pH, oxidation reduction potential (ORP), ammonia (NH3) and lactic acid. Information concerning the interaction of diet and temperature-humidity should be useful m the feeding management of cattle in different climates. Increasing the proportion of concentrates or adding starch and soluble carbohydrates to rations of cattle has been observed to decrease ruminal pH with a concomitant rise in volatile fatty acids (VFA) (Cowsert and Montgomery, 1969; Sutton, 1968; Eadie, Hobson and Mann, 1967; Slanina and Cabadog, 1967). Similarly, high grain rations, and the addition of soluble carbohydrates has been reported to decrease ruminal pH with a simultaneous increase in lactic acid (Brawner et al., 1969; Sutton, 1968; Bruno and Moore, 1962; Waldo and Schultz, 1956). In general, the postfeeding or post treatment ruminal lactic acid peaked in 2 hours.