BACK TO GUELPH 2000 TITLES

BACK TO MEETINGS MAIN PAGE
 

Does rumen pH affect diet choice of dairy cows?
J.E. Keunen1, J.L. Cumby1, J.C. Plaizier1, I. Kyriazakis2, T.M. Widowski1, T.F. Duffield1 and B.W. McBride1
1University of Guelph, Guelph, Canada, 2Scottish Agricultural College, Edinburgh, Scotland

A nutritional model to induce prolonged periods of decreased rumen pH indicative of Subacute Ruminal Acidosis (SARA) was used to determine if SARA affects the choice between feeds differing in buffering capacity. Choice was offered between alfalfa hay and alfalfa pellets in experiment 1 and between pellets containing 4 % of sodium bicarbonate and control pellets containing additional salt to equalize sodium content in experiment 2. Both experiments used four multiparous mid lactation Holstein dairy cows, and consisted of two SARA weeks separated by a control week. Cows were given choice of two feeds, twice daily at 11 am and 3 pm for 30 min (Exp.1) or 15 min (Exp. 2) for five consecutive days in each experimental week. Cows had prior experience to the test feeds prior to the start of both experiments. These feeds were presented to the cows in the same manner that they were given during the experimental weeks. Preference ratios (PR) for test feeds were calculated for each choice period as the ratio between the amount of test feed consumed and the total feed intake during each choice period. In experiment 1, SARA increased the preference for hay. This preference was made within the first 24 hours of all sample periods. In experiment 2, rumen pH was low in all weeks. Cows preferred bicarbonate pellets to the control pellets with added salt. This preference increased from week 1 to week 3, as a result of learning of the effects of bicarbonate on rumen pH or an increased aversion to the high salt content in the control pellets. SARA is a problem of major importance in the dairy industry, especially in transition cows, as was shown by Plaizier et al. (ADSA, 1999), and diet choice is one way of letting the animals attenuate this disorder for themselves. Diet choice is proving to be an effective and important means of treating subclinical disorders in dairy cows.
 

TABLE 1. Preference ratios for feeds by day
 

EXP'T / TREAT	DAY 1	DAY 2	DAY 3	DAY 4	DAY 5
1 / SARA (1,2)	0.56	0.87	0.91	0.83	0.83
1 / CONTROL (2)	0.54	0.50	0.72	0.54	0.75
2 / WEEK 1 (3)	0.69	0.62	0.70	0.85	0.86
2 / WEEK 2 (3)	0.75	0.90	0.91	0.86	0.85
2 / WEEK 3 (3)	0.79	0.97	0.97	0.86	0.92

(1) average of two SARA weeks combined
(2) PR for hay
(3) PR for bicarbonate pellets