EFFECT OF DIETARY OAT HULLS OR WHEAT BRAN ON MINERAL UTILIZATION IN GROWING PIGS FED DIETS WITH OR WITHOUT SALINOMYCIN

Abstract

Four balance trials were conducted to determine the effect of dietary fiber (oat hulls or wheat bran) and salinomycin on mineral absorption and balance in growing pigs. The experimental diets were a corn-soybean meal control diet (C), a diet containing 10% oat hulls (OH), a diet containing 20% wheat bran (WB), each with or without salinomycin (SM; 82 mg kg−1). The inclusion of OH decreased Ca (P < 0.06) and Zn (P < 0.01) balance, largely as a consequence of decreased fractional absorption (absorbed as a percentage of intake), and decreased (P < 0.10) P balance and efficiency of P retention (P < 0.04). OH did not influence Mg balance. WB did not affect Ca, Zn or P balance, but increased (P < 0.02) Mg balance, primarily due to an increase in Mg intake. Both OH and WB depressed absolute and fractional Na absorption (P < 0.01), with only nonsignificant reductions in Na balance. OH depressed K absorption (P < 0.01), but apparent K absorption was slightly increased (P < 0.08) by WB due to a greater K intake. Neither fiber source affected K balance. Pigs fed the OH and WB diets were in positive Mn balance, in contrast to the negative Mn balance in pigs fed the C diets. OH and WB increased (P < 0.01) Cu intake, and despite a decrease in fractional Cu absorption in pigs fed the OH (P < 0.03), balance was not affected. WB increased (P < 0.01) Cu balance. The apparent and fractional absorption of P was improved by SM (P < 0.05) only in pigs fed the WB diets. SM decreased apparent and fractional Cu absorption and Cu balance in the OH trials (P < 0.05) and WB trials (P < 0.01) for pigs fed the C diets only. SM did not influence Ca, Mg, Na, K, Zn or Mn absorption and balance. The results indicate that OH, and to a lesser extent WB, decreases mineral balance in pigs. The greater effects of OH suggest that differences in the chemical and physical properties, and susceptibility to degradation, may be as important as level in the diet in determining the impact of dietary fiber on mineral balance. Key words: Swine, dietary fiber, salinomycin, mineral balance