ABSTRACT:
This study evaluated the effects of different levels of substitution of ground corn by sweet potato flour on intake, digestibility, microbial protein synthesis and total Nitrogen (N) retention in sheep fed mixed diets based on corn silage. Eight castrated male sheep were used, kept in metabolic cages. The animals received fixed proportions of oat hay, corn silage and soybean meal. The control group (0%) received only ground corn, while the other groups received different levels of inclusion of sweet potato flour (SPF) to replace ground corn, in the proportions of 33%, 66%, and 100%. The 0% and 33% groups had lower neutral detergent fiber (NDF) intake than the 66% and 100% groups. There was a trend (P = 0.07) of effect of treatments on crude protein (CP) intake with a significant positive linear effect (P = 0.03). There was a trend (P = 0.07) for treatment effects in N intake with a significant positive linear effect (P = 0.03). The other parameters as urine N excretion (P = 0.91) and feces N excretion (P = 0.16) were not affected by the replacement of ground corn by SPF. Moreover, there was no effect on N retention (P = 0.43) and on efficiency of N use (P = 0.69). Adding SPF to a diet instead of corn did not alter the microbial protein parameters. The inclusion of sweet potato flour did not cause changes in the protein metabolism of animals, suggesting it can be used instead of corn.
Key words:
alternative feed; carbohydrate; faecal; metabolism