Tropical and Subtropical Agroecosystems (Aug 2016)
INFLUENCE OF TIME BETWEEN RUMINAL GLUCOSE CHALLENGES ON RUMEN FUNCTION
Abstract
Ruminal lactic acidosis is one of the most important metabolic problems in feedlot cattle. Gradually transitioning cattle to finishing-feedlot diets may reduce the risk for ruminal acidosis by providing sufficient time for adaptation. This adaptation of feedlot cattle to high-concentrate diets may causes marked changes in the ruminal environment, and time is required to establish stable ruminal conditions. However, few studies have evaluated the ruminal adaptation in steers. A metabolism trial was conducted to evaluate the effects of two consecutive glucose challenges on rumen function in steers fed a high-energy finishing diet. Four Holstein steers (320 kg LW) with cannula in the rumen were used in a 4 x 4 Latin square design. Four treatments were used and consisted of the time elapsed between both challenges of glucose (2, 4, 6 or 8 d). Ruminal fluid samples were taken at 0700 h (just prior the first glucose challenge), and from the second challenge (d 2, 4, 6, or 8) at 1 h before and 2, 4, 6, 8, 28, 52, 124, 196 and 268 h. As the time between fluctuation of energy intake increased, ruminal fluid pH (P 0.10). During the first 6 h following the second glucose challenge ruminal fluid pH decreased. No effects of treatments on ruminal pH were observed (P >0.10) among treatments from 3 days after the second challenge. Ruminal fluid osmotic pressure increased (P <0.10) after dosed glucose with all treatments. Ruminal osmolality increased (P <0.10) as the time between challenges were 2 or 4 days. After dosed glucose, total volatile fatty acids increased, except by treatment 1 after second challenge. Total volatile fatty acid and pH were related positively (R2 =0.69). As the time increased, a tendency on increment of concentrations of protozoa was observed. Ruminal glucose concentration decreased linearly (P <0.10) 2 h after the second fluctuation of energy intake. We conclude that ruminal alterations are magnified as the time between glucose challenge decreases.
