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ADAPTATION TO HIGH CONCENTRATE DIETS BY BEEF CATTLE. II. EFFECT OF RUMINAL pH ALTERATION ON RUMEN FEREMENTATION AND VOLUNTARY INTAKE OF WHEAT DIETS 1 W. R. Fulton 2, T. J. Klopfenstein and R. A. Britton University of Nebraska 3, Lincoln 68583 Summary An in vivo and in vitro fermentation study was conducted in conjunction with a feed intake trial to study the effect of controlling tureen pH on feed intake and tureen microbial fermentation patterns in steers fed a 90% concentrate wheat diet. Rumen pH was sup- ported by direct rumen infusion of an equal molar mixture of sodium and potassium hydrox- ide. Total feed intake was greater (P<.I) for hydroxide (9.87 kg) infused than for the control steers (8.39 kg). Higher period intakes were observed for the infused steers at all times with the exception of hour 2. Rumen pH values were significantly lower (P<.01) for the control steers (5.39 vs 5.88). These data indicate a possible relationship between low rumen pH and cessation of voluntary feed intake. Small differences in lactate occurred between these two treatments, possibly because of rumen microbial adaptation to a high con- centrate diet at the time the study was con- ducted. However, higher (P<.01) in vitro lactate concentrations were observed in incuba- tions where ruminal fluid source was from the hydroxide infused steers. Differences in volatile fatty acids (VFA) concentrations due to treatment were not large with the exception of valerate, which was appreciably higher (P<.05) in the control animals. Moles/lO0 moles of acetate isovalerate were significantly greater and valerate lower in the hydroxide versus control steers. aPublished with the approval of the Director as Paper No. 5606 Journal Series, Nebraska Agr. Exp. Sta. aPresent address: Citibank of Crete, Crete, NE 68333. 3 Department of Animal Science. (Key Words: Feed Intake, Rumen pH, Lactate, VFA.) Introduction A review (Dunlop, 1972) on acute acidosis occurring in ruminant animals would indicate that the major physiological alterations associ- ated with the lactic acidosis syndrome are well documented. However, the chronic or sub-acute form of acidosis (Tremere et al., 1978; Fulton 1979) characterized by an "off-feed" condition and (or) reduced feed intake and animal gain is not clearly defined. Feed intake is depressed when the tureen fluid pH falls below approximately 5.5 (Fulton et al., 1979) and rumen stasis has resulted (Dirksen, 1970). Feeding can influence tureen fluid pH and ruminal pH can influence micro- bial fermentation and its end-products (Hun- gate, 1966). Maintaining ruminal pH postfeed- ing with the inclusion of buffers in the diets has resulted in an increase in feed intake in some experiments (Bhattacharya and Warner, 1968; Nicholson and Cunningham, 1961). If rumen pH could be maintained postfeed- ing and the characteristic lactobacillus type of (Annison Lewis, 1959) prevented, there might be a reduced possibility of lactic acid accumulation. In addition, Esdale and Satter (1972) have shown that ruminal volatile fatty acid (VFA) production can be affected by alteration of rumen pH. The purpose of this study was to determine
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This note was uploaded on 09/19/2011 for the course ANS 5446 taught by Professor Brown during the Spring '08 term at University of Florida.

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