Influence of Dietary Calcium and Protein on Fecal pH, Consistency, and Rate of Passage in Dairy Cattle

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Abstract
Holstein heifers (16) and 20 calves were in trials on the effect of 10 and 15% crude protein and 0.3 and 0.9% Ca in the diet on fecal pH and consistency and on rate of passage of the liquid phase of digesta. Time of 1st appearance of polyethylene glycol (PEG) was an indicator of rate of passage of the liquid phase in the lower tract of the animal. Respective fecal pH and SE for heifers and calves increased from 5.79 .+-. 0.03 and 5.78 .+-. 0.03 on low Ca diets to 6.24 .+-. 0.03 and 6.33 .+-. 0.03 on high Ca diets. High protein diets increased fecal pH from 5.89 .+-. 0.03 and 5.97 .+-. 0.03 and 6.13 .+-. 0.03 and 6.14 .+-. 0.03 for heifers and calves. Effects of Ca and protein were additive. Neither dietary protein nor Ca affected consistency of feces or 1st appearance of PEG in feces. Mean 1st appearances of PGE in feces were 683 .+-. 13 min for heifers and 528 .+-. 18 min for calves. Small correlations between fecal pH and fecal consistency and between fecal pH and 1st appearance of PEG in feces indicate little or no relationship of fecal pH to these 2 variables. From variance in the heifer trial, 10 fecal samples are required to estimate fecal pH within .+-. 0.16 pH units with 95% confidence.