1. Impact of diet and management on rumen pH and acidosis in feedlot cattle Galen Erickson, Terry Klopfenstein Rick Stock, and Rob Cooper

2. When Nebraska students are asked a question and they don’t know the answer, they are instructed to answer “acidosis”.

3. Starch VFA Whole corn High moisture corn Dry rolled corn VFA CH 3 C=O OH CH 3 CH 2 C=O OH CH 3 CH 2 CH 2 C=O OH Energy Small Intestine Rumen Grain Feeding

4. Acidosis As A Continuum The severity of the acidosis insult determines the symptoms observed. However, for simplicity it is often divided into acute and subacute acidosis.

5. Acute Versus Subacute Acidosis Ruminal pH Acute Acidosis Subacute Acidosis <5.0 <5.6

6. Acute Acidosis Most often recognized Diet transition period Intake regulation: Forages = rumen fill Grain = chemical mechanisms “Sudden Death Syndrome” Liver Abscesses Bloat

7. Occurs more frequently Difficult to observe or identify Major response = Reduced feed intake! Pen feeding conditions Individual reductions in feed intake masked by pen average Erratic feed intake patterns Sub-Acute Acidosis

9. Symptoms of Subacute Acidosis

10. Acidosis and Intake Variation Low ruminal pH Reduced intake High ruminal pH Over consumption

11. Intake Variance Individually Fed Cattle

12. Variance in Feed Intake Among Days Within Feeding Period for Individually Fed Steers Burrin et al., 1988

13. Correlation between intake variance and gain/feed All: r =.30 All concentrate: r =.49 Burrin et al., 1988

14. Variance in Feed Intake Among Days Within Feeding Period for Individually Fed Steers But, averaged similar to a "pen" Burrin et al., 1988

15. Managing Acidosis  Rate of starch digestion  Amt of starch: adaptation  Grain type & processing  Byproducts  Roughage  Feed additives  Bunk management

16. Acidosis Research At Nebraska Continuous data acquisition system developed for individual measurements Individual feed bunks suspended from load cells Actually measuring feed “ disappearance ” Can get intake rate over time, meal size, meal frequency, etc.

17. Submersible pH probes fitted through rumen cannula Data collected via PC Acidosis Research At Nebraska

20. Typical research study: Computer takes readings of feed bunks and pH probes every 5 seconds Computer records average values for feed bunks and pH probes every minute to data file 60 minutes/hour * 24 hours/day = 1480 DATA POINTS PER DAY!!! Acidosis Research At Nebraska

21. Lbs./ day pH Typical Feed Intake And Ruminal pH Acidosis Research At Nebraska Cooper et al., 1998

22. Average Daily Ruminal pH 566330 Acidosis Research At Nebraska Cooper et al., 1998

23. Lbs./ day pH Subacute Acidosis Feed Intake And Ruminal pH Acidosis Research At Nebraska Cooper et al., 1998

24. Feed intake and ruminal pH of same steer as in previous figure, first and second day of step 2 (65% concentrate). Acidosis Research At Nebraska Cooper et al., 1998

25. DMI of Three Steers During Step-up Acidosis Research At Nebraska Cooper et al., 1998

26. Average Daily Ruminal pH Acidosis Research At Nebraska Cooper et al., 1998

27. Roughage Crawford et al., 2006

28. Alfalfa level, %P-value a Item4.59.013.5LQ DMI14.514.715.0 Average pH 5.415.52 5.58 0.010.70 Maximum pH 6.256.39 6.41 0.090.43 Minimum pH 4.924.955.02 0.050.56 Time < 5.6, min 1015853778 0.020.56 Area < 5.6 361276252 0.050.48 a No alfalfa level x CaMg(CO 3 ) 2 interactions were observed (P ≥ 0.15). Crawford et al., 2006 Roughage

29. DMI 23.5 c 21.2 ab 20.0 b 22.0 bc 0.02 Average pH 5.95 a 6.13 bc 6.11 b 6.25 c 0.01 Minimum pH 5.34 a 5.51 b 5.53 bc 5.63 c 0.02 Maximum pH 6.65 a 6.79 bc 6.75 ab 6.88 c 0.01 Time < 5.6, min 406268237156 0.06 a,b,c Means differ (P ≥ 0.15). Farran et al., 2003 Dietary Buffers ItemControlAcidbufAcidbufBicarb F-test 0.751.251.25

30. DMI, lb/d28.327.6 Rate of intake, % of daily intake/min.61.55 Ruminal pH a 5.595.73 Area below 5.6 bc 216.198.2 pH DIFF d 1.101.07 pH VAR e.063.055 a Means differ (P= 0.11). b Area = ruminal pH units below 5.6 by minute. c Means differ (P < 0.10). d Magnitude of daily ruminal pH change. e Variance of daily ruminal pH. ItemControlRumensin Treatment Feeding Rumensin Cooper et al., 1997

31. DMI, lb/d pre challenge, d 15-2122.021.621.6 challenge, d 2332.832.532.1 post challenge, d 24-2818.621.620.2 Ruminal pH pre challenge5.755.645.67 challenge 1 5.53 a 5.63 ab 5.76 b post challenge 2 5.565.545.71 pHVAR 3 0.570.490.48 9 X 2 Incomplete Latin rectangle; (6 reps/diet) Fed 50% of "normal" DMI on d 22, then 175% on d 23 (4 hours late) 1 (P = 0.06) 2 (P = 0.11) 3 challenge phase only (P = 0.10) ItemControlRumensinRumensin 33 g/ton44 g/ton Treatment Blackford et al., 2000 Feeding Rumensin

32. Blackford et al., 2002 c d d a a b a,b Means differ (P < 0.05); c,d Means differ (P < 0.10)

33. DMI, lb/d pre challenge24.9 a 20.6 b 19.4 b challenge34.3 a 30.5 b 29.4 b post challenge21.6 a 19.1 b 18.2 b Ruminal pH pre challenge5.575.575.65 challenge 1 5.685.715.77 post challenge 2 5.415.505.45 Max pH (initial) 3 7.027.117.12 18 fistulated steers (9 measured per period); (6 reps/diet, but different steers) Fed 50% of "normal" DMI on d 22, then 175% on d 23 (4 hours late) 1 (P = 0.06) 2 (P = 0.11) 3 challenge phase only (P = 0.10) ItemControlRumensinRumensin 33 g/ton44 g/ton Treatment Patterson et al., 2002 Feeding Rumensin

34. Krehbiel et al., 1995

35. Managing Acidosis  Rate of starch digestion  Amt of starch: adaptation  Grain type & processing  Byproducts  WCGF effective, WDGS not as effective  Roughage  Feed additives  Rumensin  Buffers variable CLEAR

36. Conclusions Link of DMI and pH Inducing experimentally to study! Acidosis in individuals versus pens Individual intakes in pens? Subacute acidosis/bloat > acute acidosis or “sudden death” Multiple factors influence rumen function Diet: grain, roughage, byproduct, additives Amount/rate of starch digestion Rumen stasis and bloat Metabolic acidosis and death may occur Decrease in DMI, liver abscesses, founder, etc

37. Beef Extension Page http://beef.unl.edu Beef Reports

38. CONTACT: Galen Erickson 402 472-6402; geericks@unlnotes.unl.edugeericks@unlnotes.unl.edu http://beef.unl.edu