Effects of Physically Effective Fiber on Intake, Chewing Activity, and Ruminal Acidosis for Dairy Cows Fed Diets Based on Corn Silage

Abstract

A study was conducted to investigate the effects of physically effective (pe) neutral detergent fiber (NDF) content of dairy cow diets containing corn silage as the sole forage type on feed intake, meal patterns, chewing activity, and rumen pH. The experiment was designed as a replicated 3 x 3 Latin square using 6 lactating dairy cows with ruminal cannulas. Diets were chemically similar but varied in peNDF content (high, medium, and low) by altering corn silage particle length. The physical effectiveness factors for the long (original), medium (rechopped once), and fine (rechopped twice) silages were determined using the Penn State Particle Separator and were 0.84, 0.73, and 0.67, respectively. The peNDF contents of the diets were 11.5, 10.3, and 8.9%, for the high, medium, and low diets, respectively. Increased forage particle length increased intake of peNDF but did not affect intake of DM or NDF. Number of chews (chews/d) and chewing time, including eating and ruminating time, were linearly increased with increasing dietary peNDF. Meal patterns were generally similar for all treatments, except that number of meals was quadratically increased with increasing dietary peNDF. Mean ruminal pH, area between the curve and a horizontal line at pH 5.8 or 5.5, and time that pH was below 5.8 or 5.5 were not affected by peNDF content. Dietary peNDF content was moderately correlated to number of chews during eating (r = 0.41) and to total chewing time (r = 0.37). The present study demonstrates that increasing the peNDF content of diets increased chewing time, but increased chewing time did not necessarily reduce ruminal acidosis. Models that predict rumen pH should include both peNDF and fermentable OM intake. Dietary particle size, expressed as peNDF, was a reliable indicator of chewing activity.

Effect of corn silage particle size and level of soybean oil on ruminal mat composition, distribution and consistency in Zel sheep

“…Teimouri et al (2004) and Kononoff et al (2003) found that NDF consumption increased by reducing forage particle size due to increasing DMI, because they observed that DM and NDF intake increased when the geometric mean of diets particles reduced. In addition, the value of peNDF consumption was higher in coarse corn silage diets, which was consistent with the results of Beauchemin and Yang (2005) and Kononoff et al (2003). Analyzing data from many experiments, Zebeli et al (2006) found that peNDF can regress by 0.29 variations in DMI.…”

“…The physical fill could limit feed intake at low concentrate inclusion, but a metabolic rather than a physical constraint can be expected to be rate limiting at high concentrate inclusion. However, Beauchemin and Yang (2005) reported that reducing dietary peNDF>8 from 11.5 to 8.9% ration DM was not a rate-limiting step for particulate passage for rumen physical fill and feed intake in Holstein cows fed corn silage-based TMR with a high concentrate level (~60% of ration DM). Tafaj et al (2007) reported that reducing dietary hay particle size from 28.7 to 9.2 mm increased DMI by 13% only at a lowconcentrate level (13% in DM), but when a highconcentrate diet (~40% in DM) was fed, no differences were observed in sheep.…”

Feeding behavior and performance of sheep fed cactus pear in substitution of corn

“…The number of chews per day (12,777 chews/day) of sheep that did not receive cactus pear (treatment with 280 g/kg DM corn) was due to the lower amount of dietary NDF (426 vs 481.2 g/kg for the diet with 280 g/kg DM of cactus pear) and consequently lower content of dietary peNDF (physically effective NDF). Beauchemin & Yang (2005) reported that by decreasing the peNDF content of the diets, the number of chews per day during intake was linearly reduced and tended to reduce the number of chews during rumination.…”

Effect of grain type and processing method on rumen fermentation and milk rumenic acid production

“…The pH readings were averaged for each minute and presented as mean daily pH, minimum daily pH, maximum daily pH, duration (h/day) for which rumen pH remained ,5.8, ,5.5 and ,5.2. Similar pH thresholds (5.8, 5.5 and 5.2) were used by Maekawa et al (2002) and Beauchemin and Yang (2005) to describe the severity of ruminal acidosis. The number of daily episodes of rumen pH , 5.8 was also recorded.…”