Influence of supplemental condensed tannins on initial 112-d feedlot growth-performance and characteristics of digestion of calf-fed Holstein steers

In experiment 1, 150 calf-fed Holstein steers (119 ± 6 kg) were used to evaluate the effects of level of supplemental condensed tannin (0, 14, and 28 g/kg diet DM) in a conventional steam-flaked corn-based growing-finishing diet on feedlot growth performance. There were no treatment effects on growth performance during the initial 56-d period. However, during the subsequent 56-d period, supplemental condensed tannin tended to increase average daily gain (ADG; linear effect, P = 0.09). The increase in ADG was consistent with the tendency for increased dry matter intake (DMI; linear effect, P = 0.08). Hence, differences in gain efficiency during the second 56-d period were not appreciably affected (P = 0.80). Supplemental condensed tannin did not affect overall (112-d) ADG, DMI, gain efficiency, or dietary NE. In a second experiment, six Holstein steers (179.4 ± 7.9 kg) with cannulas in the rumen and proximal duodenum were used in a replicated 3 × 3 Latin square design to evaluate treatment effects on characteristics of ruminal and total tract digestion. Treatments were the same as in Trial 1. Tannin supplementation decreased (linear effect, P = 0.03) ruminal OM digestion and tended to decrease (linear effect, P = 0.06) ruminal feed N degradation. Tannin supplementation decreased (linear effect, P = 0.03) ruminal pH, but did not affect (P > 0.20) ruminal molar proportions of volatile fatty acids and estimated methane production. In current study, supplemental tannin had marginal effects on overall growth performance of calf-fed Holstein steers, but reduced ruminal, postruminal, and total tract nitrogen digestion

INFLUENCE OF TIME BETWEEN RUMINAL GLUCOSE CHALLENGES ON RUMEN FUNCTION

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