The response of lactating cows to the total replacement of finely ground mature corn by pelleted citrus pulp was evaluated. Treatments with corn contained 10% corn and 24% citrus pulp while citrus diets contained 33% citrus pulp. The complete replacement of inorganic sources of Cu, Mn, Se, Zn, and Cr by organic sources was simultaneously evaluated. Four corn silage based diets were generated by a factorial arrangement of the two factors. Sixteen cows received the treatments in 4x4 latin squares. The effect of substituting inorganic by organic mineral sources was not conclusive. Daily dry matter intake was 19.4kg for citrus diets and 20.5kg with corn (P=0.03). The digestible organic matter intake was increased by corn supplementation (P<0.01). There was a trend for a decreased fractional rate of in situ ruminal degradation of corn silage dry matter (P=0.11) and for increased size of the indigestible fraction (P=0.15) in diets with corn, suggesting that degradation of forages did not determine the lower intake for citrus diets. The total substitution of corn by citrus pulp may decrease intake and digestibility.
bovine; starch; pectin; rumen; digestibility
